Spherical aberration hi-res stock photography and images

Skiopticon image from the Department of Photography at the Royal Institute of Technology. Use by Professor Helmer Bäckström as lecture material. Bäckström was Sweden's first professor in photography at the Royal Institute of Technology in Stockholm 1948-1958.I-III shows the point formation that arises at different setting of the plate, if the lens is subject to spherical aberration. On IV we see the corresponding shootings with a spherically corrected lens. For more info see: Bäckström, Helmer. Photographic manual. Nature and Culture. Stockholm. 1942. p. 86. Stock Photo

RM2F778AD–Skiopticon image from the Department of Photography at the Royal Institute of Technology. Use by Professor Helmer Bäckström as lecture material. Bäckström was Sweden's first professor in photography at the Royal Institute of Technology in Stockholm 1948-1958.I-III shows the point formation that arises at different setting of the plate, if the lens is subject to spherical aberration. On IV we see the corresponding shootings with a spherically corrected lens. For more info see: Bäckström, Helmer. Photographic manual. Nature and Culture. Stockholm. 1942. p. 86.

It was fortunate that he Hubble Space Telescope was designed for on-orbit repair. Soon after Hubble was placed into orbit during space shuttle mission STS-31, it became evident that something was wrong with the telescope’s optical system. It was discovered that Hubble’s primary mirror had been ground to the wrong shape. It would be necessary to design a solution to what is known as “spherical aberration.” This solution called Corrective Optics Space Telescope Axial Replacement (COSTAR) was installed during the planned first servicing mission. To prepare for the installation, astronauts returne Stock Photo

RMEN8HKK–It was fortunate that he Hubble Space Telescope was designed for on-orbit repair. Soon after Hubble was placed into orbit during space shuttle mission STS-31, it became evident that something was wrong with the telescope’s optical system. It was discovered that Hubble’s primary mirror had been ground to the wrong shape. It would be necessary to design a solution to what is known as “spherical aberration.” This solution called Corrective Optics Space Telescope Axial Replacement (COSTAR) was installed during the planned first servicing mission. To prepare for the installation, astronauts returne

saving on-line with the Internet magnifying a dollar bill Stock Photo

RFD6JRE9–saving on-line with the Internet magnifying a dollar bill

Several colors surrounding one green floral center photographed with a soft focus effect. Stock Photo

RFRPE97N–Several colors surrounding one green floral center photographed with a soft focus effect.

Soft shadows, bokeh of branches and leaves in dappled light, an old rendered wall, shadow selfie of a man in a fedora hat, a mystery unsolved Stock Photo

RM2RHE3T1–Soft shadows, bokeh of branches and leaves in dappled light, an old rendered wall, shadow selfie of a man in a fedora hat, a mystery unsolved

Archive image from page 88 of The electron microscope, its development,. The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 ( Commercial Electron Microscopes 77 Fig 24, Test photograph of simplified R.C.A. microscope. Thin membrane spattered with heavy metal. Electronic magnification X3,100 and the specimen, very near to the latter, in order to reduce the cross section of the beam and the heat development in the specimen. Such wide bundles produce large spherical aberration, and cannot be used for photographs with high r Stock Photo

RMW9G101–Archive image from page 88 of The electron microscope, its development,. The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 ( Commercial Electron Microscopes 77 Fig 24, Test photograph of simplified R.C.A. microscope. Thin membrane spattered with heavy metal. Electronic magnification X3,100 and the specimen, very near to the latter, in order to reduce the cross section of the beam and the heat development in the specimen. Such wide bundles produce large spherical aberration, and cannot be used for photographs with high r

A manual of photographic chemistry, theoretical and practical . Fig. 30. out, and this can be effected by means of the diaphragms before alluded to in the paragraph on spherical aberration; theposition and use of which will be shown in the following pages.Variation of Focus for J^ear and Distant Objects.—Lenses employed with the full aperture, do not render near andremote objects sharp upon the ground glass of the camera atthe same time. If the foreground is in focus, the lens must bethrown inwards to make the distance clear, and vice versa. Stock Photo

RM2ANF5X7–A manual of photographic chemistry, theoretical and practical . Fig. 30. out, and this can be effected by means of the diaphragms before alluded to in the paragraph on spherical aberration; theposition and use of which will be shown in the following pages.Variation of Focus for J^ear and Distant Objects.—Lenses employed with the full aperture, do not render near andremote objects sharp upon the ground glass of the camera atthe same time. If the foreground is in focus, the lens must bethrown inwards to make the distance clear, and vice versa.

Vincent Chevalier's achromatic microscope, 1825 Stock Photo

RMKWK8F2–Vincent Chevalier's achromatic microscope, 1825

Intentional colorful blur created with a macro camera lens, useful for digital background bokeh Stock Photo

RF2AW6BF1–Intentional colorful blur created with a macro camera lens, useful for digital background bokeh

Brucellosis News on the phone.Mobile phone in hands. selective focus and chromatic aberration effects. Stock Photo

RF2FYN1A2–Brucellosis News on the phone.Mobile phone in hands. selective focus and chromatic aberration effects.

. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. OPAQUE OBJECTS. 197 the lens, D E; these rays, as also those shown by fig. Ill, will be brought into a focus, F, when the lens is placed as there represented; but if the flat side occupy the same position, then, according to fig. 112, it will be in the worst possible condition, as its spherical aberration will be the greatest. Fig. 125 represents this arrangement, the same letters being used as in the preceding figur Stock Photo

RMPG43N2–. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. OPAQUE OBJECTS. 197 the lens, D E; these rays, as also those shown by fig. Ill, will be brought into a focus, F, when the lens is placed as there represented; but if the flat side occupy the same position, then, according to fig. 112, it will be in the worst possible condition, as its spherical aberration will be the greatest. Fig. 125 represents this arrangement, the same letters being used as in the preceding figur

Shown is the deviation of some of the reflected light from the focus and that arises from the curvature of the mirror, causes a blurring of the image, Stock Vector

RF2C9C59N–Shown is the deviation of some of the reflected light from the focus and that arises from the curvature of the mirror, causes a blurring of the image,

RFRHRRRR–Dappled background

Curved industrial construction background Stock Photo

RF2HAHFRM–Curved industrial construction background

$. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . has been pointed out by some of these workers that under these conditions the instrumental resolution required to resolve regular arrays of atoms or mole- cules is not so high as in the case of isolated noncohe- rent objects. The resolving power of the Siemens Elmi- skop I as limited by the diffraction error and spherical aberration alone is 2.8 A. This is worsened in practice by the chromatic error and astigmatism to 7 A. We were thus encouraged to attempt the direct observa- tion of crystal lattices in crystals Stock Photo$

RMMA7AE4–. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . has been pointed out by some of these workers that under these conditions the instrumental resolution required to resolve regular arrays of atoms or mole- cules is not so high as in the case of isolated noncohe- rent objects. The resolving power of the Siemens Elmi- skop I as limited by the diffraction error and spherical aberration alone is 2.8 A. This is worsened in practice by the chromatic error and astigmatism to 7 A. We were thus encouraged to attempt the direct observa- tion of crystal lattices in crystals

Photo Accessories. Lenses. Publication of the book 'Meyers Konversations-Lexikon', Volume 7, Leipzig, Germany, 1910 Stock Photo

RFCEGG7F–Photo Accessories. Lenses. Publication of the book 'Meyers Konversations-Lexikon', Volume 7, Leipzig, Germany, 1910

portrait, studio, photography, photo, picture, image, copy, deduction, triplet, Stock Photo

RFJ90298–portrait, studio, photography, photo, picture, image, copy, deduction, triplet,

Diverging and converging lenses. Type of eye lens. Convex and concave lenses of eyeglasses. Vector illustration Stock Vector

RF2S06H43–Diverging and converging lenses. Type of eye lens. Convex and concave lenses of eyeglasses. Vector illustration

RF2AFDJJJ–Lenses physics icon. Outline lenses physics vector icon for web design isolated on white background

Abstract metal spinning stripes on a black background, monochrome. Design. Long tangled mechanism. Stock Photo

RF2X8NF3D–Abstract metal spinning stripes on a black background, monochrome. Design. Long tangled mechanism.

The electron microscope, its development, The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 Geometrical Electron Optics 11 transversal spherical aberration. In fact, the bundle has its smallest cross section not at p but at m, which is called the disc of minimum confusion. Its radius is one quarter of the spherical aberration. When an electron lens is focused, it is always m, not p, which is made to coincide with the screen or plate. Scherzer ^ has proved the important theorem that in electron lenses, whether electrostatic Stock Photo

RMRWMPFH–The electron microscope, its development, The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 Geometrical Electron Optics 11 transversal spherical aberration. In fact, the bundle has its smallest cross section not at p but at m, which is called the disc of minimum confusion. Its radius is one quarter of the spherical aberration. When an electron lens is focused, it is always m, not p, which is made to coincide with the screen or plate. Scherzer ^ has proved the important theorem that in electron lenses, whether electrostatic

. The Pharmaceutical era. nsmit it to theeye. It acts as a simple mi-croscope and gives a virtualimage, which is not inverted,but has the same direction asthe image from which it wasformed. When composed of morethan one lens or combination,that next the eye is termedthe Eye I^ens and that turnedtowards the objective theField Lens. The ocular is subject to thesame defects of chromaticand spherical aberration asthe objective, and has thesedefects corrected in the same manner. Of the many varieties of oculars which have been in-vented, only two are of sufBcient importance to deserveattention, the Stock Photo

RM2AFWMBD–. The Pharmaceutical era. nsmit it to theeye. It acts as a simple mi-croscope and gives a virtualimage, which is not inverted,but has the same direction asthe image from which it wasformed. When composed of morethan one lens or combination,that next the eye is termedthe Eye I^ens and that turnedtowards the objective theField Lens. The ocular is subject to thesame defects of chromaticand spherical aberration asthe objective, and has thesedefects corrected in the same manner. Of the many varieties of oculars which have been in-vented, only two are of sufBcient importance to deserveattention, the

RF2AW6BF4–Intentional colorful blur created with a macro camera lens, useful for digital background bokeh

. Laboratory work in bacteriology. Bacteriology. THE MICROSCOPE. 125 The violet component is bent most, and hence, is brought to a focus at a different point from the red ray, which is bent the. least. The result is a fringe of colors. This is designated as chromatic aber- ration. It is necessary, therefore, to correct the chromatic and spherical aberration, in order to obtain the best optical re- sults. The spherical aberra- tion is partially corrected by means of stops or diaphragms, which hold back the peri- pheral rays, and allow only the central ones to pass through, since these give rise Stock Photo

RMPG2R6F–. Laboratory work in bacteriology. Bacteriology. THE MICROSCOPE. 125 The violet component is bent most, and hence, is brought to a focus at a different point from the red ray, which is bent the. least. The result is a fringe of colors. This is designated as chromatic aber- ration. It is necessary, therefore, to correct the chromatic and spherical aberration, in order to obtain the best optical re- sults. The spherical aberra- tion is partially corrected by means of stops or diaphragms, which hold back the peri- pheral rays, and allow only the central ones to pass through, since these give rise

RF2HAHFRG–Curved industrial construction background

. The electron microscope, its development, present performance and future possibilities . Fig 24, Test photograph of simplified R.C.A. microscope. Thin membrane spattered with heavy metal. Electronic magnification X3,100 and the specimen, very near to the latter, in order to reduce the cross section of the beam and the heat development in the specimen. Such wide bundles produce large spherical aberration, and cannot be used for photographs with high resolution, but they are very useful for focusing the specimen. Apart from the higher intensity, a wide bundle has the advantage of smaller depth Stock Photo

RMMA79YR–. The electron microscope, its development, present performance and future possibilities . Fig 24, Test photograph of simplified R.C.A. microscope. Thin membrane spattered with heavy metal. Electronic magnification X3,100 and the specimen, very near to the latter, in order to reduce the cross section of the beam and the heat development in the specimen. Such wide bundles produce large spherical aberration, and cannot be used for photographs with high resolution, but they are very useful for focusing the specimen. Apart from the higher intensity, a wide bundle has the advantage of smaller depth

RF2XKPBCX–Convex and concave lens. Optics physics icon. Scheme with light ray direction and bending through lens. Vector

RF2AFCWDD–Lenses physics icon. Simple illustration of lenses physics vector icon for web design isolated on white background

RF2X8NCDA–Abstract metal spinning stripes on a black background, monochrome. Design. Long tangled mechanism.

The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 Geometrical Electron Optics 11 transversal spherical aberration. In fact, the bundle has its smallest cross section not at p but at m, which is called the disc of minimum confusion. Its radius is one quarter of the spherical aberration. When an electron lens is focused, it is always m, not p, which is made to coincide with the screen or plate. Scherzer ^ has proved the important theorem that in electron lenses, whether electrostatic, magnetic, or combined, the spherical Stock Photo

RMRYF2WG–The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 Geometrical Electron Optics 11 transversal spherical aberration. In fact, the bundle has its smallest cross section not at p but at m, which is called the disc of minimum confusion. Its radius is one quarter of the spherical aberration. When an electron lens is focused, it is always m, not p, which is made to coincide with the screen or plate. Scherzer ^ has proved the important theorem that in electron lenses, whether electrostatic, magnetic, or combined, the spherical

. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. rthest from the slide, and c is probably thebest of them; but no single achromatic lens is capable ofperfect correction for anything like short foci. (b) Double or triple achromatic lenses.—With foci of teninches and over, however, the spherical aberration is muchless, and these lenses then perform very well, and are incommon use for long-focus work. Two or even three of suchlong-focus lenses combined, make better short-focus lensesthan single achromatics of such short focus ; and hence it i Stock Photo

RM2AG0B61–. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. rthest from the slide, and c is probably thebest of them; but no single achromatic lens is capable ofperfect correction for anything like short foci. (b) Double or triple achromatic lenses.—With foci of teninches and over, however, the spherical aberration is muchless, and these lenses then perform very well, and are incommon use for long-focus work. Two or even three of suchlong-focus lenses combined, make better short-focus lensesthan single achromatics of such short focus ; and hence it i

RF2AW6BDN–Intentional colorful blur created with a macro camera lens, useful for digital background bokeh

RMPG43PD–. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. MAGNIFYING POWERS. 161 fering with definition. The spherical aberration may be con- siderably diminished by attending to the figm^e of the lens employed; thus, if it be a planoconvex, the convex side should be placed towards the eye, if a double convex, it has been found in practice that one whose radii are in the proportion of one to six is the form in which the aberration is the least; but it can be entirely got ri

RF2HAPH8K–Curved industrial construction background

. The electron microscope, its development, present performance and future possibilities . Fig. 4. Spherical aberration aberration can never be eliminated as long as there are no space charges or currents in the space traversed by electrons. All lenses used to date in electron optics fall into this class. The spherical aberration has always the sign as shown in figure 4, i.e., the strength of the lens increases with the angle a. In optics this is called an undercorrected lens. Corrected electron lenses are impossible. Scherzer has proved also that the same fundamental difficulty exists in the Stock Photo

RMMA7A0N–. The electron microscope, its development, present performance and future possibilities . Fig. 4. Spherical aberration aberration can never be eliminated as long as there are no space charges or currents in the space traversed by electrons. All lenses used to date in electron optics fall into this class. The spherical aberration has always the sign as shown in figure 4, i.e., the strength of the lens increases with the angle a. In optics this is called an undercorrected lens. Corrected electron lenses are impossible. Scherzer has proved also that the same fundamental difficulty exists in the

RMRWK390–The electron microscope, its development, The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 Commercial Electron Microscopes 77 Fig 24, Test photograph of simplified R.C.A. microscope. Thin membrane spattered with heavy metal. Electronic magnification X3,100 and the specimen, very near to the latter, in order to reduce the cross section of the beam and the heat development in the specimen. Such wide bundles produce large spherical aberration, and cannot be used for photographs with high resolution, but they are very usef

The microscope; an introduction to microscopic methods and to histology . ope. O. Object. It is represented without a cover-glass. Ordinarily objects are covered whether ex-amined with immersion or with dry objectives. Stage. Section of the stage of the fnicroscope. 19. Non-Achromatic Objectives.—These are objectives in which the chro-matic aberration is not corrected, and the image produced is bordered by coloredfringes. They show also spherical aberration and are used only on very cheapmicroscopes. { 7, 8, Figs. 12, 13). I 20. Achromatic Objectives.—In these the chromatic and the spheric Stock Photo

RM2AWR8X2–The microscope; an introduction to microscopic methods and to histology . ope. O. Object. It is represented without a cover-glass. Ordinarily objects are covered whether ex-amined with immersion or with dry objectives. Stage. Section of the stage of the fnicroscope. 19. Non-Achromatic Objectives.—These are objectives in which the chro-matic aberration is not corrected, and the image produced is bordered by coloredfringes. They show also spherical aberration and are used only on very cheapmicroscopes. { 7, 8, Figs. 12, 13). I 20. Achromatic Objectives.—In these the chromatic and the spheric

$. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. 168 PRACTICAL TKEATISE ON THE MICROSCOPE. ciety of Arts. The eye-piece in question was invented by Huyghens for telescopes, with no other view than that of diminishing the spherical aberration by producing the refrac- tions at two glasses instead of one, and of increasing the field of view. It consists of two planoconvex lenses, with their plane sides towards the eye, and placed at a distance apart equal to half the Stock Photo$

RMPG43P6–. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. 168 PRACTICAL TKEATISE ON THE MICROSCOPE. ciety of Arts. The eye-piece in question was invented by Huyghens for telescopes, with no other view than that of diminishing the spherical aberration by producing the refrac- tions at two glasses instead of one, and of increasing the field of view. It consists of two planoconvex lenses, with their plane sides towards the eye, and placed at a distance apart equal to half the

RF2HAPH84–Curved industrial construction background

. The electron microscope, its development, present performance and future possibilities . FiG. 5. Chromatic aberration scopes in which the field is seldom more than a few degrees of arc. The coma is illustrated in figure 6. A lens, corrected for spherical aberration but not corrected for coma, images extra- axial points in the shape of an arrowhead pointing toward the axis. The point of the arrow corresponds to the ray which passes through the center of the lens; all other rays strike the screen at a greater distance from the axis. Rays passing through coaxial circles of the lens strike the s Stock Photo

RMMA7A0W–. The electron microscope, its development, present performance and future possibilities . FiG. 5. Chromatic aberration scopes in which the field is seldom more than a few degrees of arc. The coma is illustrated in figure 6. A lens, corrected for spherical aberration but not corrected for coma, images extra- axial points in the shape of an arrowhead pointing toward the axis. The point of the arrow corresponds to the ray which passes through the center of the lens; all other rays strike the screen at a greater distance from the axis. Rays passing through coaxial circles of the lens strike the s

RMRWMPTB–The electron microscope, its development, The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 12 The Electron Microscope selves increasingly with the distance from the axis. Of these, only the coma increases with the first power of extra-axial distance, therefore, this is the only one of importance in micro- FiG. 5. Chromatic aberration scopes in which the field is seldom more than a few degrees of arc. The coma is illustrated in figure 6. A lens, corrected for spherical aberration but not corrected for coma, images extra

. The principles of physics. Fig. 322. vantages derivedare as follows: 1. The combination diminishes spherical aberration and therebyincreases the flatness of the field. The images o 6 and a b (Fig. 323)are in reality curved in consequence of the spherical aberration COMPOUND MICROSCOPE. 425 caused by the objective. The effect of the field lens is to correctthis curvature in a measure. 2. The combination increases the field of view, so that a largerarea of the object is made visible at the same view. 3. The combination diminishes chromatic aberration. All microscopes, however, should be furnis Stock Photo

RM2AFRC79–. The principles of physics. Fig. 322. vantages derivedare as follows: 1. The combination diminishes spherical aberration and therebyincreases the flatness of the field. The images o 6 and a b (Fig. 323)are in reality curved in consequence of the spherical aberration COMPOUND MICROSCOPE. 425 caused by the objective. The effect of the field lens is to correctthis curvature in a measure. 2. The combination increases the field of view, so that a largerarea of the object is made visible at the same view. 3. The combination diminishes chromatic aberration. All microscopes, however, should be furnis

. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MICROSCOPE. 335 towards the object, the aberration is 4| times the thickness of the lens. Hence, when a plano- convex lens is employed, its convex surface should be turned towards a distant object, when it is used to form an image by bringing to a focus parallel or slightly-diverging rays; but it should be turned towards the eye, when it is used to render parallel the rays which are diverging from a very near object. The single lens having the least spherical aberration is a double convex, whose radii are as 1 to 6. When Stock Photo

RMPFN762–. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MICROSCOPE. 335 towards the object, the aberration is 4| times the thickness of the lens. Hence, when a plano- convex lens is employed, its convex surface should be turned towards a distant object, when it is used to form an image by bringing to a focus parallel or slightly-diverging rays; but it should be turned towards the eye, when it is used to render parallel the rays which are diverging from a very near object. The single lens having the least spherical aberration is a double convex, whose radii are as 1 to 6. When

. The electron microscope, its development, present performance and future possibilities . Fig. 15a cal aberration would have very poor resolution. The effect corresponding to inelastic collisions is absent in ordinary micro- scopy, as light in general does not change its wavelength in the object. An exception is fluorescence microscopy. In this case, it would be possible to imitate the working of the electron micro- scope by reversing the usual process. Instead of observing the visible fluorescence through chromatically corrected objectives, one could use lenses corrected for spherical aberra Stock Photo

RMMA7A03–. The electron microscope, its development, present performance and future possibilities . Fig. 15a cal aberration would have very poor resolution. The effect corresponding to inelastic collisions is absent in ordinary micro- scopy, as light in general does not change its wavelength in the object. An exception is fluorescence microscopy. In this case, it would be possible to imitate the working of the electron micro- scope by reversing the usual process. Instead of observing the visible fluorescence through chromatically corrected objectives, one could use lenses corrected for spherical aberra

The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 Commercial Electron Microscopes 77 Fig 24, Test photograph of simplified R.C.A. microscope. Thin membrane spattered with heavy metal. Electronic magnification X3,100 and the specimen, very near to the latter, in order to reduce the cross section of the beam and the heat development in the specimen. Such wide bundles produce large spherical aberration, and cannot be used for photographs with high resolution, but they are very useful for focusing the specimen. Apart from Stock Photo

RMRYH4FK–The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 Commercial Electron Microscopes 77 Fig 24, Test photograph of simplified R.C.A. microscope. Thin membrane spattered with heavy metal. Electronic magnification X3,100 and the specimen, very near to the latter, in order to reduce the cross section of the beam and the heat development in the specimen. Such wide bundles produce large spherical aberration, and cannot be used for photographs with high resolution, but they are very useful for focusing the specimen. Apart from

. Quarterly journal of microscopical science. he term aristokratic image was introduced to denote the bestpoicer image obtainable by given combinations of eye-pieces, searcher andobjective. ^ Messrs. Powell and Lealand fully agree with me in this view. THB PRESENT CONDITION OF ENGLISH OBJECT-GLASSES. 265 Example.—In the finest objectives now obtainable I findwhen the spherical aberration is corrected there is a strongsecondary spectrum, chiefly consisting of a mixture of the redand yellow rays. But when this is corrected, by using allpossible precautions, so as to render the achromatism almost Stock Photo

RM2AGD1FJ–. Quarterly journal of microscopical science. he term aristokratic image was introduced to denote the bestpoicer image obtainable by given combinations of eye-pieces, searcher andobjective. ^ Messrs. Powell and Lealand fully agree with me in this view. THB PRESENT CONDITION OF ENGLISH OBJECT-GLASSES. 265 Example.—In the finest objectives now obtainable I findwhen the spherical aberration is corrected there is a strongsecondary spectrum, chiefly consisting of a mixture of the redand yellow rays. But when this is corrected, by using allpossible precautions, so as to render the achromatism almost

RMPG43R0–. A practical treatise on the use of the microscope, including the different methods of preparing and examining animal, vegetable, and mineral structures. Microscopes; Microscopy. MAGNirYING POWEES. 159 it will be i^equisite, in the first place, that certain terms, such as spherical and chromatic aberration, be fuUy under- stood. Most persons are familiar with the fact, that when parallel rays of light fall upon a piano or double convex lens, they are brought to a point at a certain distance from the lens, which point is termed their focus. Thus sup- pose in fig. Ill that the rays, L L, &c

$Electron microscopy; proceedings of the Stockholm Conference, September, 1956 electronmicrosco00euro Year: 1957 has been pointed out by some of these workers that under these conditions the instrumental resolution required to resolve regular arrays of atoms or mole- cules is not so high as in the case of isolated noncohe- rent objects. The resolving power of the Siemens Elmi- skop I as limited by the diffraction error and spherical aberration alone is 2.8 A. This is worsened in practice by the chromatic error and astigmatism to 7 A. We were thus encouraged to attempt the direct observa- tion Stock Photo$

RMRYH6P8–Electron microscopy; proceedings of the Stockholm Conference, September, 1956 electronmicrosco00euro Year: 1957 has been pointed out by some of these workers that under these conditions the instrumental resolution required to resolve regular arrays of atoms or mole- cules is not so high as in the case of isolated noncohe- rent objects. The resolving power of the Siemens Elmi- skop I as limited by the diffraction error and spherical aberration alone is 2.8 A. This is worsened in practice by the chromatic error and astigmatism to 7 A. We were thus encouraged to attempt the direct observa- tion

A manual of photographic chemistry, theoretical and practical . focus, adding ma-terially to rapidity of action. The aberrations of the front lens, especially for oblique rays,are such as to render it altogether impossible that these can be 350 OPTICS OF PHOTOGKAPHT. transmitted to a focus, especially on the same plane as that towhich the axial rays converge, hence the back lens must con-sist of a combination of two simple lenses, the materials andcurvatures of which are so adjusted as not only to form anachromatic in itself, but to possess so great an amount ofnegative spherical aberration as Stock Photo

RM2ANF1DR–A manual of photographic chemistry, theoretical and practical . focus, adding ma-terially to rapidity of action. The aberrations of the front lens, especially for oblique rays,are such as to render it altogether impossible that these can be 350 OPTICS OF PHOTOGKAPHT. transmitted to a focus, especially on the same plane as that towhich the axial rays converge, hence the back lens must con-sist of a combination of two simple lenses, the materials andcurvatures of which are so adjusted as not only to form anachromatic in itself, but to possess so great an amount ofnegative spherical aberration as

$Electron microscopy; proceedings of the Electron microscopy; proceedings of the Stockholm Conference, September, 1956 electronmicrosco00euro Year: 1957 has been pointed out by some of these workers that under these conditions the instrumental resolution required to resolve regular arrays of atoms or mole- cules is not so high as in the case of isolated noncohe- rent objects. The resolving power of the Siemens Elmi- skop I as limited by the diffraction error and spherical aberration alone is 2.8 A. This is worsened in practice by the chromatic error and astigmatism to 7 A. We were thus encoura Stock Photo$

RMRWNTFT–Electron microscopy; proceedings of the Electron microscopy; proceedings of the Stockholm Conference, September, 1956 electronmicrosco00euro Year: 1957 has been pointed out by some of these workers that under these conditions the instrumental resolution required to resolve regular arrays of atoms or mole- cules is not so high as in the case of isolated noncohe- rent objects. The resolving power of the Siemens Elmi- skop I as limited by the diffraction error and spherical aberration alone is 2.8 A. This is worsened in practice by the chromatic error and astigmatism to 7 A. We were thus encoura

Gilbert light experiments for boys . mirror areright side up. Searchlight Reflectors. The reflectors on battleship search-lights (Fig. 108) are made in the shape of a parabola (Fig. 109).Parallel rays which strike parabolic reflectors converge exactlyat the focus, and conversely if a light is placed exactly at thefocus the reflected light consists of parallel rays which gostraight forward. The reflectors on automobile and locomotiveheadlights are also parabolic, and the lamp is placed at the focus.Spherical Aberration. Spherical mirrors do not converge allparallel rays at the focus because tho Stock Photo

RM2AXAP5M–Gilbert light experiments for boys . mirror areright side up. Searchlight Reflectors. The reflectors on battleship search-lights (Fig. 108) are made in the shape of a parabola (Fig. 109).Parallel rays which strike parabolic reflectors converge exactlyat the focus, and conversely if a light is placed exactly at thefocus the reflected light consists of parallel rays which gostraight forward. The reflectors on automobile and locomotiveheadlights are also parabolic, and the lamp is placed at the focus.Spherical Aberration. Spherical mirrors do not converge allparallel rays at the focus because tho

RMRWMPTD–The electron microscope, its development, The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 FiG. 5. Chromatic aberration scopes in which the field is seldom more than a few degrees of arc. The coma is illustrated in figure 6. A lens, corrected for spherical aberration but not corrected for coma, images extra- axial points in the shape of an arrowhead pointing toward the axis. The point of the arrow corresponds to the ray which passes through the center of the lens; all other rays strike the screen at a greater distance fro

$. The principles of physics. nserted in the side of the telescope. The reflector serves asan object-glass, and is of course free from chromatic aberration,while spherical aberration is corrected by the shape given the 1 The student may ascertain the magnifying power of a terrestrial telescope byviewing a scale directly with one eye, and its magnified image as seen through thetelescope with the other eye. (See the authors Laboratory Manual and Note Book.) 2 On the whole, however, if the matter of expense be disregarded, the balance ofadvantage is generally considered to lie with the refracting Stock Photo$

RM2AFRBB9–. The principles of physics. nserted in the side of the telescope. The reflector serves asan object-glass, and is of course free from chromatic aberration,while spherical aberration is corrected by the shape given the 1 The student may ascertain the magnifying power of a terrestrial telescope byviewing a scale directly with one eye, and its magnified image as seen through thetelescope with the other eye. (See the authors Laboratory Manual and Note Book.) 2 On the whole, however, if the matter of expense be disregarded, the balance ofadvantage is generally considered to lie with the refracting

The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 FiG. 5. Chromatic aberration scopes in which the field is seldom more than a few degrees of arc. The coma is illustrated in figure 6. A lens, corrected for spherical aberration but not corrected for coma, images extra- axial points in the shape of an arrowhead pointing toward the axis. The point of the arrow corresponds to the ray which passes through the center of the lens; all other rays strike the screen at a greater distance from the axis. Rays passing through coaxial Stock Photo

RMRYF39T–The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 FiG. 5. Chromatic aberration scopes in which the field is seldom more than a few degrees of arc. The coma is illustrated in figure 6. A lens, corrected for spherical aberration but not corrected for coma, images extra- axial points in the shape of an arrowhead pointing toward the axis. The point of the arrow corresponds to the ray which passes through the center of the lens; all other rays strike the screen at a greater distance from the axis. Rays passing through coaxial

Elements of natural philosophy (Volume 2-3) . from a point concias far behind the reflector as the real radiant is infront; but if they converge before deviation, they willbe brought to a focus as far in front as the virtual racli-ant is behind the reflector. usioiL 216 NATURAL PIIILOSOPIIT. SPHERICAL ABERRATION, CAUSTICS, AND ASTIGMATISM. Sphericalaberration; Incident pencilnot small; Illustration; Longitudinal aberration; Lateralaberration; § 56. Thus far the discussion has been conducted uj)onthe supposition that the pencil is veryNsmall, and that 2, theversed-sine of the angle d, included Stock Photo

RM2AJ2DJP–Elements of natural philosophy (Volume 2-3) . from a point concias far behind the reflector as the real radiant is infront; but if they converge before deviation, they willbe brought to a focus as far in front as the virtual racli-ant is behind the reflector. usioiL 216 NATURAL PIIILOSOPIIT. SPHERICAL ABERRATION, CAUSTICS, AND ASTIGMATISM. Sphericalaberration; Incident pencilnot small; Illustration; Longitudinal aberration; Lateralaberration; § 56. Thus far the discussion has been conducted uj)onthe supposition that the pencil is veryNsmall, and that 2, theversed-sine of the angle d, included

The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 12 The Electron Microscope selves increasingly with the distance from the axis. Of these, only the coma increases with the first power of extra-axial distance, therefore, this is the only one of importance in micro- FiG. 5. Chromatic aberration scopes in which the field is seldom more than a few degrees of arc. The coma is illustrated in figure 6. A lens, corrected for spherical aberration but not corrected for coma, images extra- axial points in the shape of an arrowhe Stock Photo

RMRYF39P–The electron microscope, its development, present performance and future possibilities electronmicrosco00gabo Year: 1948 12 The Electron Microscope selves increasingly with the distance from the axis. Of these, only the coma increases with the first power of extra-axial distance, therefore, this is the only one of importance in micro- FiG. 5. Chromatic aberration scopes in which the field is seldom more than a few degrees of arc. The coma is illustrated in figure 6. A lens, corrected for spherical aberration but not corrected for coma, images extra- axial points in the shape of an arrowhe

. The principles of physics. farthest from its vertex are brought to a focus nearer themirror than the inner rays; consequently the image furnished bya luminous point is a circle brightest toward its center. This phe-nomenon is called the spherical aberration of a mirror. It rendersthe definition of the images of objects, especially of broad objects, very bad. In conse-quence of this it is oftennecessary to cut ofi theoutside rays by a dia-phragm, which improvesthe definition at the ex-pense of the brightnessof the image. By constructing anumber of rays (Fig.243) we may show thatall rays after Stock Photo

RM2AFRPT7–. The principles of physics. farthest from its vertex are brought to a focus nearer themirror than the inner rays; consequently the image furnished bya luminous point is a circle brightest toward its center. This phe-nomenon is called the spherical aberration of a mirror. It rendersthe definition of the images of objects, especially of broad objects, very bad. In conse-quence of this it is oftennecessary to cut ofi theoutside rays by a dia-phragm, which improvesthe definition at the ex-pense of the brightnessof the image. By constructing anumber of rays (Fig.243) we may show thatall rays after

. The principles of physics. Fig. 276. 328. Spherical aberration. — In all ordinary convex lensesthe curved surfaces are spherical, and the angles which inci-dent rays make with the little plane surfaces of which wemay imagine the spherical surface to be made up, increase. Fig. 277. rapidly toward the edge of the lens. Thus, while those raysfrom a given point of an object which pass through the cen-tral portion, as A (Fig. 277), meet approximately at the samepoint F, those which pass through the marginal portion aredeflected so much that they cross the axis at nearer points,e.g. at F; so a blu Stock Photo

RM2AFRHW5–. The principles of physics. Fig. 276. 328. Spherical aberration. — In all ordinary convex lensesthe curved surfaces are spherical, and the angles which inci-dent rays make with the little plane surfaces of which wemay imagine the spherical surface to be made up, increase. Fig. 277. rapidly toward the edge of the lens. Thus, while those raysfrom a given point of an object which pass through the cen-tral portion, as A (Fig. 277), meet approximately at the samepoint F, those which pass through the marginal portion aredeflected so much that they cross the axis at nearer points,e.g. at F; so a blu

$. Light, a textbook for students who have had one year of physics. highly magnifying them, and they become a source of troubleonly in the most exacting work with telescope or microscope.The nature of this fault will be considered later under thehead of diffraction, sections 72 and 73. 39. Spherical aberration.—Another fault is known asspherical aberration. Quite apart from the just-mentioneddifficulty of diffraction, and from chromatic aberration, therays coming through the edges of a lens are not brought to thesame focus as those coming through near the center. Thisfollows from the fact menti Stock Photo$

RM2AFMTTK–. Light, a textbook for students who have had one year of physics. highly magnifying them, and they become a source of troubleonly in the most exacting work with telescope or microscope.The nature of this fault will be considered later under thehead of diffraction, sections 72 and 73. 39. Spherical aberration.—Another fault is known asspherical aberration. Quite apart from the just-mentioneddifficulty of diffraction, and from chromatic aberration, therays coming through the edges of a lens are not brought to thesame focus as those coming through near the center. Thisfollows from the fact menti

A manual of photographic chemistry, theoretical and practical . arious rajs crossing and interfering with each other.In correcting for spherical aberration, the lirst point to beattended to is the curve of the lens itself. A biconvex lens,as shown in the (Fig. 28) diagram, is the worst form. The plano-convex and the meniscus lenses are preferable, and for land-scapes the latter is very commonly employed. But spherical aberration, even in a lens which is badly madeas regards form, may be remedied in another way, viz., byusing a diaphragm or stop, so as to cut off a portion of thelight, and prev Stock Photo

RM2ANF655–A manual of photographic chemistry, theoretical and practical . arious rajs crossing and interfering with each other.In correcting for spherical aberration, the lirst point to beattended to is the curve of the lens itself. A biconvex lens,as shown in the (Fig. 28) diagram, is the worst form. The plano-convex and the meniscus lenses are preferable, and for land-scapes the latter is very commonly employed. But spherical aberration, even in a lens which is badly madeas regards form, may be remedied in another way, viz., byusing a diaphragm or stop, so as to cut off a portion of thelight, and prev

Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . some w^orks on optics,that a combination of two convergent lenses was calculated by SirJohn Herschel, and said to be free from spherical aberration. This,however, is a mistake, which Herschel himself has rectified in hismemoirs. We now come to the most important method of correcting spher-ical aberration, that is, by a second lens of opposite character.Suppose we want to correct the spherical aberration of the positivelens X (Fig. 26) along its axis, ff is the l Stock Photo

RM2AWT32X–Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . some w^orks on optics,that a combination of two convergent lenses was calculated by SirJohn Herschel, and said to be free from spherical aberration. This,however, is a mistake, which Herschel himself has rectified in hismemoirs. We now come to the most important method of correcting spher-ical aberration, that is, by a second lens of opposite character.Suppose we want to correct the spherical aberration of the positivelens X (Fig. 26) along its axis, ff is the l

Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . ss the axis atH /. In this case the spherical aberration is of theopposite character, and is called negative aberra- tion. It is evident, from the foregoing, that spher-ical aberration varies with the aperture of the lensand the material of which the lens is made.R Therefore, the larger a lens is in proportion toits focal length, the greater its spherical aberra-tion. A lens of an aperture of, say ^oth of itsfocal length, has no perceptible spherical aberration. Stock Photo

RM2AWT52T–Wilson's quarter century in photography : a collection of hints on practical photography which form a complete text-book of the art . ss the axis atH /. In this case the spherical aberration is of theopposite character, and is called negative aberra- tion. It is evident, from the foregoing, that spher-ical aberration varies with the aperture of the lensand the material of which the lens is made.R Therefore, the larger a lens is in proportion toits focal length, the greater its spherical aberra-tion. A lens of an aperture of, say ^oth of itsfocal length, has no perceptible spherical aberration.

A companion to the United States pharmacopia; . e, or ocular, the first ofwhich is the magnifying lens, and isattached to the lower end of the body,while the other is a small tube slidinginto the upper part of the draw-tubeand carrying a combination of lensesfor enlarging or amplifying the imagemade by the objective. The relation of the optical parts toeach other are shown in Fig. 550. The objective should be correctedfor chromatic and spherical aberration,which is done by combining a double-convex lens of crown-glass and a plano-concave lens of flint-glass (doublet).In the better class of obj Stock Photo

RM2AM621J–A companion to the United States pharmacopia; . e, or ocular, the first ofwhich is the magnifying lens, and isattached to the lower end of the body,while the other is a small tube slidinginto the upper part of the draw-tubeand carrying a combination of lensesfor enlarging or amplifying the imagemade by the objective. The relation of the optical parts toeach other are shown in Fig. 550. The objective should be correctedfor chromatic and spherical aberration,which is done by combining a double-convex lens of crown-glass and a plano-concave lens of flint-glass (doublet).In the better class of obj

The Kodak Salesman . tion. There was atime when the possessor of an an-astigmat which had found its wayinto his hands from abroad felthimself just a little better equippedthan his neighbor who could boastonly of a lens originating in theUnited States perhaps. It may bethat years ago there was some justi-fication in this attitude and that theimported lenses were better correct-ed for spherical aberration, comaand all the other optical errors thanwere lenses here, but that time haslong since passed. In addition tobeing available at a more reason-able price, Kodak Anastigmat lensesare now equal t Stock Photo

RM2AJ4HHR–The Kodak Salesman . tion. There was atime when the possessor of an an-astigmat which had found its wayinto his hands from abroad felthimself just a little better equippedthan his neighbor who could boastonly of a lens originating in theUnited States perhaps. It may bethat years ago there was some justi-fication in this attitude and that theimported lenses were better correct-ed for spherical aberration, comaand all the other optical errors thanwere lenses here, but that time haslong since passed. In addition tobeing available at a more reason-able price, Kodak Anastigmat lensesare now equal t

$A manual of photographic chemistry, theoretical and practical . hazy, owing to the ray Z being refracted in agreater degree than any others of those between it and the LENSES. 339 upper boundary ray O. If tlie transmitted ray Z, instead oftaking the coarse Z, went straight to 0,the intermediate raysdoing the same, then would we have a perfect single leris;but such is not the case, owing to the aberration caused bythe spherical surface of the glass. Spherical aberration, itmay here be once more remarked, is that property in a lenswhereby parallel rays falling either obliquely or axially uponits Stock Photo$

RM2ANF5AX–A manual of photographic chemistry, theoretical and practical . hazy, owing to the ray Z being refracted in agreater degree than any others of those between it and the LENSES. 339 upper boundary ray O. If tlie transmitted ray Z, instead oftaking the coarse Z, went straight to 0,the intermediate raysdoing the same, then would we have a perfect single leris;but such is not the case, owing to the aberration caused bythe spherical surface of the glass. Spherical aberration, itmay here be once more remarked, is that property in a lenswhereby parallel rays falling either obliquely or axially uponits

RM2ANF5NC–A manual of photographic chemistry, theoretical and practical . Fig. 30. out, and this can be effected by means of the diaphragms before alluded to in the paragraph on spherical aberration; theposition and use of which will be shown in the following pages.Variation of Focus for J^ear and Distant Objects.—Lenses employed with the full aperture, do not render near andremote objects sharp upon the ground glass of the camera atthe same time. If the foreground is in focus, the lens must bethrown inwards to make the distance clear, and vice versa.. Fig. 31. This is a necessary consequence of the foc

$An American text-book of physiology . n common with all optical instruments, while others arejieculiar to the eve and are not found in instruments of human construction.The former class will be first considered. Spherical Aberration.—It has been stated that a ]iencil of rays fallingui)on a spherical refra»-ting surface will be refracted to a common focus.Strictlv sjxiaking, however, the outer rays of the pencil—i. e. those which fall THE SENSE OF VISION. 761 near the periphery f the refracting snrface—will be reiracted more than thoseA lie near the axis and will come to a focus sooner. T Stock Photo$

RM2AJDNJY–An American text-book of physiology . n common with all optical instruments, while others arejieculiar to the eve and are not found in instruments of human construction.The former class will be first considered. Spherical Aberration.—It has been stated that a ]iencil of rays fallingui)on a spherical refra»-ting surface will be refracted to a common focus.Strictlv sjxiaking, however, the outer rays of the pencil—i. e. those which fall THE SENSE OF VISION. 761 near the periphery f the refracting snrface—will be reiracted more than thoseA lie near the axis and will come to a focus sooner. T

$. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. , that the spherical aberration is partially removed. Inthe calculation the radius in the apex must form the basis. SIMPLICITY OF THE APHAKIAL SYSTEM. 311 the cornea, should have a length h 4> = 30*58 mm., in order, in the Fig. 122.. absence of the lens, to bring parallel rays to a focus on the retina.Now, since this axis is, almost without exception, much shorter, theaphakial eye must in general be in a high degree hypermetropic. Inorder to find the degree of this H, with a gi Stock Photo$

RM2AGDE6N–. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. , that the spherical aberration is partially removed. Inthe calculation the radius in the apex must form the basis. SIMPLICITY OF THE APHAKIAL SYSTEM. 311 the cornea, should have a length h 4> = 30*58 mm., in order, in the Fig. 122.. absence of the lens, to bring parallel rays to a focus on the retina.Now, since this axis is, almost without exception, much shorter, theaphakial eye must in general be in a high degree hypermetropic. Inorder to find the degree of this H, with a gi

The student's guide to diseases of the eye . Fig. 9.—Spherical aberration. of foci. This spherical aberration increases with the size ofthe lens. In the eye it is, to a great extent, removed by theiris, which prevents the light from passing tnrough the mar-ginal parts of the crystalline lens. If parallel rays are incident from the side to-wards/ (Fig. 10) they will be focussed at /, at thesame distance from the lens as f hence every lenshas two principal foci—anterior and posterior. 12. The path of a ray passing from one point toanother is the same, whatever its direction; the pathof the ray Stock Photo

RM2AWK79A–The student's guide to diseases of the eye . Fig. 9.—Spherical aberration. of foci. This spherical aberration increases with the size ofthe lens. In the eye it is, to a great extent, removed by theiris, which prevents the light from passing tnrough the mar-ginal parts of the crystalline lens. If parallel rays are incident from the side to-wards/ (Fig. 10) they will be focussed at /, at thesame distance from the lens as f hence every lenshas two principal foci—anterior and posterior. 12. The path of a ray passing from one point toanother is the same, whatever its direction; the pathof the ray

. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. Fia. 15.—Spherical Aberration a plane; or conversely, the diagram or picture m m must bedrawn upon a concave surface to produce a flat image mm, anexpedient actually employed in early solar microscopes.. Fig. 16.-Distortions of Image The curved image maybe more or less flattened, as it iacalled, by adopting a meniscus form for the lens, as shown infig. 14 by the various achromatics b, c, e. But we are nowconfronted with another result of aberration, in the form of the THE PARTS OF A LANTERN Stock Photo

RM2AG0BCY–. Optical projection : a treatise on the use of the lantern in exhibition and scientific demonstration. Fia. 15.—Spherical Aberration a plane; or conversely, the diagram or picture m m must bedrawn upon a concave surface to produce a flat image mm, anexpedient actually employed in early solar microscopes.. Fig. 16.-Distortions of Image The curved image maybe more or less flattened, as it iacalled, by adopting a meniscus form for the lens, as shown infig. 14 by the various achromatics b, c, e. But we are nowconfronted with another result of aberration, in the form of the THE PARTS OF A LANTERN

. Light, a textbook for students who have had one year of physics. t the lens defects such aschromatic and spherical aberration, curvature of field, etc.,would be very prominent. Therefore, wherever high magnify-ing power is necessary, it is provided by a compound micro-scope. Figure 58 shows the arrangement of parts. The ob-ject is usually in the form of a slide, a very thin slice of thematerial to be examined enclosed between two thin glass plates.The slide is represented by the short arrow A in the diagram.Slides being more or less transparent, they are examined bytransmitted light. A mirro Stock Photo

RM2AFMRHM–. Light, a textbook for students who have had one year of physics. t the lens defects such aschromatic and spherical aberration, curvature of field, etc.,would be very prominent. Therefore, wherever high magnify-ing power is necessary, it is provided by a compound micro-scope. Figure 58 shows the arrangement of parts. The ob-ject is usually in the form of a slide, a very thin slice of thematerial to be examined enclosed between two thin glass plates.The slide is represented by the short arrow A in the diagram.Slides being more or less transparent, they are examined bytransmitted light. A mirro

The student's guide to diseases of the eye . Fig. 8.—Axes of a lens.. Fig. 9.—Spherical aberration. of foci. This spherical aberration increases with the size ofthe lens. In the eye it is, to a great extent, removed by theiris, which prevents the light from passing tnrough the mar-ginal parts of the crystalline lens. If parallel rays are incident from the side to-wards/ (Fig. 10) they will be focussed at /, at thesame distance from the lens as f hence every lenshas two principal foci—anterior and posterior. 12. The path of a ray passing from one point toanother is the same, whatever its direc Stock Photo

RM2AWK7ND–The student's guide to diseases of the eye . Fig. 8.—Axes of a lens.. Fig. 9.—Spherical aberration. of foci. This spherical aberration increases with the size ofthe lens. In the eye it is, to a great extent, removed by theiris, which prevents the light from passing tnrough the mar-ginal parts of the crystalline lens. If parallel rays are incident from the side to-wards/ (Fig. 10) they will be focussed at /, at thesame distance from the lens as f hence every lenshas two principal foci—anterior and posterior. 12. The path of a ray passing from one point toanother is the same, whatever its direc

. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . Fig. 100.—Deformity of Image Due to the Shape of the Retina. pole and the incident rays suffer spherical aberration in the peripheralregions, hence the impossibility of rectilinearity when a distant fieldis under observation with fixation at a definite point. The aberroscopeshows the presence of this distortion. But on accommodation it isfound that the aberroscope generally shows no distortion and evenan over-correction giving evidence of the formation of an anteriorlenticonus. At the same time Stock Photo

RM2CE3XWG–. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . Fig. 100.—Deformity of Image Due to the Shape of the Retina. pole and the incident rays suffer spherical aberration in the peripheralregions, hence the impossibility of rectilinearity when a distant fieldis under observation with fixation at a definite point. The aberroscopeshows the presence of this distortion. But on accommodation it isfound that the aberroscope generally shows no distortion and evenan over-correction giving evidence of the formation of an anteriorlenticonus. At the same time

. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. , although its performances were verysuperior to those of the non-achromatic instrument.*Concave mirrors, when formed of segments of spheres,are liable to spherical aberration, just as lenses are(Fig. 21) ; therefore, when it is required to renderdivergent rays parallel, or bring parallel rays to afocus, it is necessary that the figure of the mirrorshould be that of a parabola. Specula of thisform are used in astronomical telescopes, therefled Stock Photo

RM2CF36BK–. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. , although its performances were verysuperior to those of the non-achromatic instrument.*Concave mirrors, when formed of segments of spheres,are liable to spherical aberration, just as lenses are(Fig. 21) ; therefore, when it is required to renderdivergent rays parallel, or bring parallel rays to afocus, it is necessary that the figure of the mirrorshould be that of a parabola. Specula of thisform are used in astronomical telescopes, therefled

$. The London, Edinburgh and Dublin philosophical magazine and journal of science. mula? as given in the text-books forcentral spherical aberration are computed to the squareof the aperture only,—a degree of approximation which isinsufficient for the purpose of the practical optician in thedesign of photographic and other objectives. In thefollowing work a formula will be given for the longitudinalaberration for a system of coaxial spherical surfaces separatingmedia of refractive indices fi0...fjLK which is correct to thefourth power of the aperture. A greater degree of accuracythan this is usu Stock Photo$

RM2CENJC2–. The London, Edinburgh and Dublin philosophical magazine and journal of science. mula? as given in the text-books forcentral spherical aberration are computed to the squareof the aperture only,—a degree of approximation which isinsufficient for the purpose of the practical optician in thedesign of photographic and other objectives. In thefollowing work a formula will be given for the longitudinalaberration for a system of coaxial spherical surfaces separatingmedia of refractive indices fi0...fjLK which is correct to thefourth power of the aperture. A greater degree of accuracythan this is usu

RM2CF3BAJ–. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. impossible in practice. Spherical aberration maybelessened by reducing the aperture of the lens, bycutting off the marginal portion by means of stops ordiaphragms ; but any great use of this means causesa loss of light very detrimental to the performanceof the instrument. Advantage may also be taken ofthe position in which the lens is placed and also ofits figure; the spherical aberration of some lenses,such as plano-convex and meniscus, is mu

. The book of photography; practical, theoretical and applied. gh an isochromatic screen, providingthe exposure is made with the screen. Spherical Abereatiox. Spherical aberration is due to thecurved surface of the lens, and may bedefined as the inability of the lens tobring the rays which pass through itsedges or margin to the same focus asthose passing through its centre (see Fig. eliminated, although with spherical lensesit can never be entirely removed. Forpractical purposes, it is consideredsufhcient when the image of a point oflight is rendered in the picture as acircle of not more than Stock Photo

RM2CEYAX1–. The book of photography; practical, theoretical and applied. gh an isochromatic screen, providingthe exposure is made with the screen. Spherical Abereatiox. Spherical aberration is due to thecurved surface of the lens, and may bedefined as the inability of the lens tobring the rays which pass through itsedges or margin to the same focus asthose passing through its centre (see Fig. eliminated, although with spherical lensesit can never be entirely removed. Forpractical purposes, it is consideredsufhcient when the image of a point oflight is rendered in the picture as acircle of not more than

. The science-history of the universe . points of the object along the line lasttraveled by the light. Hence the object appears greatlymagnified—its extremities appearing to be much fartherapart than in reality they are. The more convex the lensthe greater is its magnifying power, but the greater, atthe same time, the difficulty in using it without some cor-rection of the spherical aberration which increases withthe curvature of the lens. Double convex lenses, used asmagnifying glasses, are frequently called simple micro- 90 PHYSICS scopes, as distinguished from the powerful compound mi-crosco Stock Photo

RM2CDD67B–. The science-history of the universe . points of the object along the line lasttraveled by the light. Hence the object appears greatlymagnified—its extremities appearing to be much fartherapart than in reality they are. The more convex the lensthe greater is its magnifying power, but the greater, atthe same time, the difficulty in using it without some cor-rection of the spherical aberration which increases withthe curvature of the lens. Double convex lenses, used asmagnifying glasses, are frequently called simple micro- 90 PHYSICS scopes, as distinguished from the powerful compound mi-crosco

. The book of photography; practical, theoretical and applied. Fig. 500.—Section of Double Meniscus Lens. Since it is uncorrected for chromaticaberration, it is no use focussing with itin the ordinary way ; the result must becorrected by one of the methods describedon p. 355. Besides this fault, the lens issubject to spherical aberration, curva-ture of field, and astigmatism, unless wellstopped down. Except when used as asupplementary lens, or magnifier, to alter. Fij. 502.—Section of Thhee-Glass Single Achro-matic Lens. the focus of another, it is hardly adaptedfor practical work of any descr Stock Photo

RM2CF6NMJ–. The book of photography; practical, theoretical and applied. Fig. 500.—Section of Double Meniscus Lens. Since it is uncorrected for chromaticaberration, it is no use focussing with itin the ordinary way ; the result must becorrected by one of the methods describedon p. 355. Besides this fault, the lens issubject to spherical aberration, curva-ture of field, and astigmatism, unless wellstopped down. Except when used as asupplementary lens, or magnifier, to alter. Fij. 502.—Section of Thhee-Glass Single Achro-matic Lens. the focus of another, it is hardly adaptedfor practical work of any descr

$. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . Fig. 23.—Curves Showing the Spherical Aberration of the Cornea. (After Brud- zewski.) The abscissae indicate the distance from the visual axis in millimeters; theordinates show the refraction in diopters. where the angle w and the distance y must be variable and experi-mentally obtainable. 46. It is known that a spherical surface has positive aberration. Aspherical cornea of 40 diopters has at 4 millimeters from the axis anaberration of about 3 diopters. But such a spherical surface may bemade a Stock Photo$

RM2CE09FF–. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . Fig. 23.—Curves Showing the Spherical Aberration of the Cornea. (After Brud- zewski.) The abscissae indicate the distance from the visual axis in millimeters; theordinates show the refraction in diopters. where the angle w and the distance y must be variable and experi-mentally obtainable. 46. It is known that a spherical surface has positive aberration. Aspherical cornea of 40 diopters has at 4 millimeters from the axis anaberration of about 3 diopters. But such a spherical surface may bemade a

. The book of photography; practical, theoretical and applied. or orthostigmat. Astig-matism, although seldom entirely absentfrom any lens, is more usually found inlenses designed to obtain great flatnessof field. The introduction of Jena glasshas enabled the optician to devise com-binations in which this defect is almostentirely eliminated. The method of test-ing for astigmatism is described on p. 35. Curvature ob Field. One difficidty inseparable from thespherical form in which lenses are groundhas already been dealt with, namely,spherical aberration. There is, however,another. The image of Stock Photo

RM2CEYAN9–. The book of photography; practical, theoretical and applied. or orthostigmat. Astig-matism, although seldom entirely absentfrom any lens, is more usually found inlenses designed to obtain great flatnessof field. The introduction of Jena glasshas enabled the optician to devise com-binations in which this defect is almostentirely eliminated. The method of test-ing for astigmatism is described on p. 35. Curvature ob Field. One difficidty inseparable from thespherical form in which lenses are groundhas already been dealt with, namely,spherical aberration. There is, however,another. The image of

$. A treatise on diseases of the eye . :------- o 0-^^ Fig. 62. Aberration.—It is only when small pencils of light are isolated thatwe may assume that all the rays meet in their conjugate foci after refrac-tion at a spherical surface. ^Nhen a large sector of the wave passes intothe second medium the angles of incidence of the rays increase so rapidly,as the distance from the axis increases, that the more peripheral raysare refracted too much in proportion to the central rays, so that thesharpness of the focus is marred. This constitutes spherical aberration. Chromatic Aberration.—This results f Stock Photo$

RM2CDJFHM–. A treatise on diseases of the eye . :------- o 0-^^ Fig. 62. Aberration.—It is only when small pencils of light are isolated thatwe may assume that all the rays meet in their conjugate foci after refrac-tion at a spherical surface. ^Nhen a large sector of the wave passes intothe second medium the angles of incidence of the rays increase so rapidly,as the distance from the axis increases, that the more peripheral raysare refracted too much in proportion to the central rays, so that thesharpness of the focus is marred. This constitutes spherical aberration. Chromatic Aberration.—This results f

$. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . ens to decrease the natural chromatism of the eye before which it isplaced. 116 PHYSIOLOGICAL OPTICS IX. SPHERICAL ABERRATION 86. Caustic caused by refraction at a curved surface and thephenomenon of spherical aberration as exhibited by a lens. In Fig.52 let AMP be a spherical surface of which C is the center of curvature,P the pole and PC, produced, the axis. Air and glass are the media.The paths of the various refracted rays due to the incident parallelrays may be found according to the law o Stock Photo$

RM2CDXGBX–. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . ens to decrease the natural chromatism of the eye before which it isplaced. 116 PHYSIOLOGICAL OPTICS IX. SPHERICAL ABERRATION 86. Caustic caused by refraction at a curved surface and thephenomenon of spherical aberration as exhibited by a lens. In Fig.52 let AMP be a spherical surface of which C is the center of curvature,P the pole and PC, produced, the axis. Air and glass are the media.The paths of the various refracted rays due to the incident parallelrays may be found according to the law o

. Portrait . o v t v a i i; reason that as a rule portrait lenses working at F-5 orF-4 focus sharper at the center than on the edges, orvice versa, due to the fact that they have to a greater orlesser degree the fault of spherical aberration, whichcauses the rays of light passing through the center ofthe lens to be somewhat longer than those passingthrough the edges; thus, when the lens is focused on. Posing at Home the center figure the outer figures may be out of focus,or when the outer figures are focused the center is out.To get them as near together as possible the group isposed in circul Stock Photo

RM2CE06A3–. Portrait . o v t v a i i; reason that as a rule portrait lenses working at F-5 orF-4 focus sharper at the center than on the edges, orvice versa, due to the fact that they have to a greater orlesser degree the fault of spherical aberration, whichcauses the rays of light passing through the center ofthe lens to be somewhat longer than those passingthrough the edges; thus, when the lens is focused on. Posing at Home the center figure the outer figures may be out of focus,or when the outer figures are focused the center is out.To get them as near together as possible the group isposed in circul

$. A text-book of human physiology . rays oblique. The first case is the simplest (for the second see page 525). Suppose wehave a lens, which in the horizontal meridian has a refractive power of 10diopters; in the vertical meridian a refractive power of 13 diopters. It isevident that the beam after refraction will no longer have a common focus,for the incident rays in the horizontal meridian are brought to a focusyV m- behind the lens and those falling in a vertical meridian J^ m. behindthe lens. Further study of the ])rol)lem has shown that if no account be taken ofthe spherical aberration, th Stock Photo$

RM2CE6PFT–. A text-book of human physiology . rays oblique. The first case is the simplest (for the second see page 525). Suppose wehave a lens, which in the horizontal meridian has a refractive power of 10diopters; in the vertical meridian a refractive power of 13 diopters. It isevident that the beam after refraction will no longer have a common focus,for the incident rays in the horizontal meridian are brought to a focusyV m- behind the lens and those falling in a vertical meridian J^ m. behindthe lens. Further study of the ])rol)lem has shown that if no account be taken ofthe spherical aberration, th

. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . Fig. 57.—The Rules of the Optometer of Young. the most important instruments for the study of physiologic optics,—enables us to measure spherical aberration directly. It is in the formof a little rule carrying a fine white line on a black background onone side. The observer looks along this line through a -J- 10 3D. lens.In front of the lens is placed a small horizontal rule, free to move andcarrying different groups of slits. Two slits in this rule will act likethe openings in the experiments o Stock Photo

RM2CDX4TK–. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . Fig. 57.—The Rules of the Optometer of Young. the most important instruments for the study of physiologic optics,—enables us to measure spherical aberration directly. It is in the formof a little rule carrying a fine white line on a black background onone side. The observer looks along this line through a -J- 10 3D. lens.In front of the lens is placed a small horizontal rule, free to move andcarrying different groups of slits. Two slits in this rule will act likethe openings in the experiments o

$. The London, Edinburgh and Dublin philosophical magazine and journal of science. and /uL the index of refraction, then the error produced by Measurement of the Refractive Index of Liquids. 307 the spherical aberration of a parallel beam may be written AF = R8a20(/u), (9) A/=-RaVM, (10) where (/>(//,) and ^{fi) are certain functions depending on thetype of lens employed. The curves are drawn for (1) asphere, (2) a plano-convex lens with light incident on curvedface, (3) a plano-convex lens with light incident on plane face,(4) double convex lens with faces of equal curvature. Fig. 2represen Stock Photo$

RM2CEP1CC–. The London, Edinburgh and Dublin philosophical magazine and journal of science. and /uL the index of refraction, then the error produced by Measurement of the Refractive Index of Liquids. 307 the spherical aberration of a parallel beam may be written AF = R8a20(/u), (9) A/=-RaVM, (10) where (/>(//,) and ^{fi) are certain functions depending on thetype of lens employed. The curves are drawn for (1) asphere, (2) a plano-convex lens with light incident on curvedface, (3) a plano-convex lens with light incident on plane face,(4) double convex lens with faces of equal curvature. Fig. 2represen

$. The microscope and its revelations. s called the rirtini/ />rinci/>til focus of the lens. It will he manifest that since the rays in passing through lenses ofvarious kinds arc unequally refracted they cannot all meet exactly in asingle local point. This gives rise to what is a most important featurein the behaviour of lenses, which is known as spherical aberration. Figs. 17 and IK show the refraction of rays of monochromatic1 A fro/ iniii^c ca.ii l>c received on a screen, but ft virtual image cannot. SPHERICAL ABERRATION 15 light parallel to the axis falling on a plano-convex lens o Stock Photo$

RM2CEE63A–. The microscope and its revelations. s called the rirtini/ />rinci/>til focus of the lens. It will he manifest that since the rays in passing through lenses ofvarious kinds arc unequally refracted they cannot all meet exactly in asingle local point. This gives rise to what is a most important featurein the behaviour of lenses, which is known as spherical aberration. Figs. 17 and IK show the refraction of rays of monochromatic1 A fro/ iniii^c ca.ii l>c received on a screen, but ft virtual image cannot. SPHERICAL ABERRATION 15 light parallel to the axis falling on a plano-convex lens o

$. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. SENSE or sight. 855 the density of the lens at its central part, in order that it may act more strongly on rays of light, by which the refracting power is increased at that point; this is accomplished in the crystalline lens of the eye in this manner since it is less dense at the circumference than in the centre : or, spherical aberration may be diminished by placing a diaphragm between the object of which the image is to be formed and the lens Stock Photo$

RMRE02HC–. The physiology of the domestic animals; a text-book for veterinary and medical students and practitioners. Physiology, Comparative; Domestic animals. SENSE or sight. 855 the density of the lens at its central part, in order that it may act more strongly on rays of light, by which the refracting power is increased at that point; this is accomplished in the crystalline lens of the eye in this manner since it is less dense at the circumference than in the centre : or, spherical aberration may be diminished by placing a diaphragm between the object of which the image is to be formed and the lens

. Animal physiology. Physiology, Comparative. 424 SPHERICAL ABERRATION. owing to the large quantity of minute blood-vessels which it contains, it presents a bright red hue. The choroid coat, seen through the pupil, has exactly the same aspect; so that the pupil is not readily distinguished. During the day the vision of these Albinos is very indistinct, and the glare of light is painful to them; and it is only when twilight comes-on, that they can see clearly and without discomfort. 546. The eye is much more remarkable for its perfection as an optical instrument, than we might be led to suppose Stock Photo

RMRN4MTK–. Animal physiology. Physiology, Comparative. 424 SPHERICAL ABERRATION. owing to the large quantity of minute blood-vessels which it contains, it presents a bright red hue. The choroid coat, seen through the pupil, has exactly the same aspect; so that the pupil is not readily distinguished. During the day the vision of these Albinos is very indistinct, and the glare of light is painful to them; and it is only when twilight comes-on, that they can see clearly and without discomfort. 546. The eye is much more remarkable for its perfection as an optical instrument, than we might be led to suppose

$. The microscope : an introduction to microscopic methods and to histology. Microscopes. CH. I] MICROSCOPE AND ACCESSORIES 5 10. Correction of Chromatic and of Spherical Aberration.âEvery simple lens has the defect of both chromatic and spherical aberration, and to overcome this, kinds of glass of different refractive power and different dis- persive power are combined, concave lenses neutralizing the defects of convex lenses. If the concave lens is not sufficiently strong to neutralize the aberra- Fig. 13. The ray (o) near the edge of the lens is brought to a focus nearer the lens than the Stock Photo$

RMRE05KJ–. The microscope : an introduction to microscopic methods and to histology. Microscopes. CH. I] MICROSCOPE AND ACCESSORIES 5 10. Correction of Chromatic and of Spherical Aberration.âEvery simple lens has the defect of both chromatic and spherical aberration, and to overcome this, kinds of glass of different refractive power and different dis- persive power are combined, concave lenses neutralizing the defects of convex lenses. If the concave lens is not sufficiently strong to neutralize the aberra- Fig. 13. The ray (o) near the edge of the lens is brought to a focus nearer the lens than the

$. A text-book of bacteriology, including the etiology and prevention of infective diseases and a short account of yeasts, and moulds, haematazoa, and psorosperms. Bacteriology. THE BACTERIOLOGICAL MICROSCOPE. ^7 of a microscope are principally convex, and the imperfections whick result mnst, if possible, be entirely overcome. These imperfections are spherical and chromatic aberration. Spherical aberration results from the unequal refraction of rays passing through lenses with equal curvatures. The rays passing through an ordinary convex lens do not all come to the same focus.. The rays passing Stock Photo$

RMRE4JDJ–. A text-book of bacteriology, including the etiology and prevention of infective diseases and a short account of yeasts, and moulds, haematazoa, and psorosperms. Bacteriology. THE BACTERIOLOGICAL MICROSCOPE. ^7 of a microscope are principally convex, and the imperfections whick result mnst, if possible, be entirely overcome. These imperfections are spherical and chromatic aberration. Spherical aberration results from the unequal refraction of rays passing through lenses with equal curvatures. The rays passing through an ordinary convex lens do not all come to the same focus.. The rays passing

$. The microscope; an introduction to microscopic methods and to histology. Microscopes. ch. r MICROSCOPE AND ACCESSORIES of parallel rays very near the axis is at/", rays {o i), nearer the edge, would come to a focus nearer the lens, the focus of the ray nearest the edge being nearest the lens. | 9. Correction of Chromatic and of Spherical Aberration.—Every simple lens has the defect of both chromatic and spherical aberration, and to overcome this, kinds of glass of different refractive power and different dispersive power are combined, concave lenses neutralizing the defects of convex le Stock Photo$

RMRE061M–. The microscope; an introduction to microscopic methods and to histology. Microscopes. ch. r MICROSCOPE AND ACCESSORIES of parallel rays very near the axis is at/", rays {o i), nearer the edge, would come to a focus nearer the lens, the focus of the ray nearest the edge being nearest the lens. | 9. Correction of Chromatic and of Spherical Aberration.—Every simple lens has the defect of both chromatic and spherical aberration, and to overcome this, kinds of glass of different refractive power and different dispersive power are combined, concave lenses neutralizing the defects of convex le

$. The physiology of domestic animals ... Physiology, Comparative; Veterinary physiology. SENSE OP SIGHT. 855 the density of the lens at its central part, in order that it may act more strongly on rays of light, by which the refracting power is increased at that point; this is accomplished in the crystalline lens of the eye in this manner since it is less dense at the circumference than in the centre : or, spherical aberration may be diminished by placing a diaphragm between the object of which the image is to be formed and the lens, so as to cut off those rays which pass through the circumfere Stock Photo$

RMRE3THT–. The physiology of domestic animals ... Physiology, Comparative; Veterinary physiology. SENSE OP SIGHT. 855 the density of the lens at its central part, in order that it may act more strongly on rays of light, by which the refracting power is increased at that point; this is accomplished in the crystalline lens of the eye in this manner since it is less dense at the circumference than in the centre : or, spherical aberration may be diminished by placing a diaphragm between the object of which the image is to be formed and the lens, so as to cut off those rays which pass through the circumfere

$. Electron microscopy; proceedings of the Stockholm Conference, September, 1956. Electron microscopy. has been pointed out by some of these workers that under these conditions the instrumental resolution required to resolve regular arrays of atoms or mole- cules is not so high as in the case of isolated noncohe- rent objects. The resolving power of the Siemens Elmi- skop I as limited by the diffraction error and spherical aberration alone is 2.8 A. This is worsened in practice by the chromatic error and astigmatism to 7 A. We were thus encouraged to attempt the direct observa- tion of crystal Stock Photo$

RMRD6FB7–. Electron microscopy; proceedings of the Stockholm Conference, September, 1956. Electron microscopy. has been pointed out by some of these workers that under these conditions the instrumental resolution required to resolve regular arrays of atoms or mole- cules is not so high as in the case of isolated noncohe- rent objects. The resolving power of the Siemens Elmi- skop I as limited by the diffraction error and spherical aberration alone is 2.8 A. This is worsened in practice by the chromatic error and astigmatism to 7 A. We were thus encouraged to attempt the direct observa- tion of crystal

. The electron microscope, its development, present performance and future possibilities. Electron microscopes. Commercial Electron Microscopes 77. Fig 24, Test photograph of simplified R.C.A. microscope. Thin membrane spattered with heavy metal. Electronic magnification X3,100 and the specimen, very near to the latter, in order to reduce the cross section of the beam and the heat development in the specimen. Such wide bundles produce large spherical aberration, and cannot be used for photographs with high resolution, but they are very useful for focusing the specimen. Apart from the higher in Stock Photo

RMRD5FPR–. The electron microscope, its development, present performance and future possibilities. Electron microscopes. Commercial Electron Microscopes 77. Fig 24, Test photograph of simplified R.C.A. microscope. Thin membrane spattered with heavy metal. Electronic magnification X3,100 and the specimen, very near to the latter, in order to reduce the cross section of the beam and the heat development in the specimen. Such wide bundles produce large spherical aberration, and cannot be used for photographs with high resolution, but they are very useful for focusing the specimen. Apart from the higher in

RMRD5CTH–. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. MICROSCOPE. 335 towards the object, the aberration is 4| times the thickness of the lens. Hence, when a plano- convex lens is employed, its convex surface should be turned towards a distant object, when it is used to form an image by bringing to a focus parallel or slightly-diverging rays; but it should be turned towards the eye, when it is used to render parallel the rays which are diverging from a very near object. The single lens having the least spherical aberration is a double convex, whose radii are as 1 to 6. When

. Animal physiology. Physiology, Comparative; Physiology, Comparative. ALBINOS. SPHERICAL ABERRATION. 409 being reflected from one part of the interior of the globe of the eye to another, which would cause a great confusion and indis- tinctness in the picture. Hence it is that, in those individuals (both among Man and the lower animals) in whose eyes this pig- ment is deficient, vision is extremely imperfect. The eyes of those individuals (termed Albinos), derive, from the absence of pigment, a very peculiar appearance. The iris does not possess its ordinary colour ; but, owing to the large qu Stock Photo

RMRN4KJ0–. Animal physiology. Physiology, Comparative; Physiology, Comparative. ALBINOS. SPHERICAL ABERRATION. 409 being reflected from one part of the interior of the globe of the eye to another, which would cause a great confusion and indis- tinctness in the picture. Hence it is that, in those individuals (both among Man and the lower animals) in whose eyes this pig- ment is deficient, vision is extremely imperfect. The eyes of those individuals (termed Albinos), derive, from the absence of pigment, a very peculiar appearance. The iris does not possess its ordinary colour ; but, owing to the large qu

. The electron microscope, its development, present performance and future possibilities. Electron microscopes. Geometrical Electron Optics 11 transversal spherical aberration. In fact, the bundle has its smallest cross section not at p but at m, which is called the disc of minimum confusion. Its radius is one quarter of the spherical aberration. When an electron lens is focused, it is always m, not p, which is made to coincide with the screen or plate. Scherzer ^ has proved the important theorem that in electron lenses, whether electrostatic, magnetic, or combined, the spherical. Fig. 4. Sphe Stock Photo

RMRD5FTC–. The electron microscope, its development, present performance and future possibilities. Electron microscopes. Geometrical Electron Optics 11 transversal spherical aberration. In fact, the bundle has its smallest cross section not at p but at m, which is called the disc of minimum confusion. Its radius is one quarter of the spherical aberration. When an electron lens is focused, it is always m, not p, which is made to coincide with the screen or plate. Scherzer ^ has proved the important theorem that in electron lenses, whether electrostatic, magnetic, or combined, the spherical. Fig. 4. Sphe

$. Pathogenic micro-organisms. A text-book of microbiology for physicians and students of medicine. (Based upon Williams' Bacteriology). Bacteriology; Pathogenic bacteria. 20 BACTERIOLOGY correction may be thanged by altering,the distance between these component lenses, as, for example, in an objective equipped with a correction pollar. Objectives corrected in respect to spherical aberration are designated as aplanatic. Restriction of the size of the field is also an important factor in making it appear flat. Light of different wave lengths (different colors) is refracted to a different degree Stock Photo$

RMRE3HH0–. Pathogenic micro-organisms. A text-book of microbiology for physicians and students of medicine. (Based upon Williams' Bacteriology). Bacteriology; Pathogenic bacteria. 20 BACTERIOLOGY correction may be thanged by altering,the distance between these component lenses, as, for example, in an objective equipped with a correction pollar. Objectives corrected in respect to spherical aberration are designated as aplanatic. Restriction of the size of the field is also an important factor in making it appear flat. Light of different wave lengths (different colors) is refracted to a different degree

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