"In <em>optics</em>, a deviation in the rays of light when unequally refracted by a lens or reflected by a mirror, so that they do not converge and meet in a point or focus, but separate, forming an indistinct image of the object, or an indistinct image with prismatically colored edges."-Wright, 1902

Aberration

"In optics, a deviation in the rays of light when unequally refracted by a lens or reflected…

An apparatus used to photograph images in a light microscope. The long camera is connected to the eye piece while the microscope uses a mirror to light the specimen. The image is captured on the photographic plate.

Micrographic Apparatus with Camera and Microscope

An apparatus used to photograph images in a light microscope. The long camera is connected to the eye…

Binoculars, or Prism Field Glasses, from Kodak in 1907.

Binoculars

Binoculars, or Prism Field Glasses, from Kodak in 1907.

Field glasses or binoculars from Ecker in Lucerne, Switzerland.

Swiss Binoculars

Field glasses or binoculars from Ecker in Lucerne, Switzerland.

This image shows a woman creating an illustration using the camera obscura.

Camera Obscura

This image shows a woman creating an illustration using the camera obscura.

The illustration of putting lenses in front of the eye. The focal point of the image is reflected into the eye. The focal point in the lens will end past the eye, creating a blurry image.

Optical Position and Size of Image Through Lens in Front of Eye

The illustration of putting lenses in front of the eye. The focal point of the image is reflected into…

"They have also a shorter focus for red, and a longer one for blue, and thus magnify the red image more than the blue; and as the objective gives a large blue and small red image, the two cancel one another and a colourless image is produced." &mdash;Encyclopaedia Britannica, 1910

Huyegenian Eyepiece Diagram Showing Lens Refraction

"They have also a shorter focus for red, and a longer one for blue, and thus magnify the red image more…

"If the real image produced by the objective coincides with the collective lens, only the inclination of the principal rays is altered. The lens nearer to the eye is distant from it about its focal length. The eye&mdash;lens converts diverging pencils into parallels. Both lenses together form the exit pupil of the objective behind the eye&mdash;lens." &mdash;Encyclopaedia Britannica, 1910

Ramsden Eyepiece Lens Refraction Diagram

"If the real image produced by the objective coincides with the collective lens, only the inclination…

"When the object is at a long distance from the lens, the image formed is smaller than the object, and inverted." -Foster, 1921

Convex Lens

"When the object is at a long distance from the lens, the image formed is smaller than the object, and…

"Showing a system with chromatic difference of spherical aberration. O" &#8332; image of O for red light; O'" for blue. The system is under&mdash;corrected for red, and over&mdash;corrected for blue rays." &mdash;Encyclopaedia Britannica, 1910

Light Correction of Blue and Red Lights using Spherical Lens

"Showing a system with chromatic difference of spherical aberration. O" ₌ image of O for red light;…

A Baker demonstration light microscope illustrating the different parts of the microscope. The eyepiece is adjusted at knob F. The mirror J reflects light from a light source to shine light through the sample.

Baker Demonstration Light Microscope with Mirror Reflecting Light Source

A Baker demonstration light microscope illustrating the different parts of the microscope. The eyepiece…

A swift Stephenson's Binocular Microscope with a mirror reflecting light source. The microscope has an adjustable slits to monitor how much light is coming through the sample. Two eyepieces focuses and magnify the sample by adjusting both lenses.

Swift Stephen's Binocular Microscope with Mirror Reflecting Light Source

A swift Stephenson's Binocular Microscope with a mirror reflecting light source. The microscope has…

An illustration of entocentric transmission of a compound microscope. The series of light refracted by the lens causes a projection to make near objects appear larger, and farther objects smaller.

Entocentric Transmission in Compound Microscope Appear Images Larger or Smaller

An illustration of entocentric transmission of a compound microscope. The series of light refracted…

A Greenough's binocular light microscope. The microscope has two eyepieces to view the sample with both eyes. The mirror is used to provide a light source for the microscope by reflecting light.

Greenough's Binocular Light Compound Microscope with Mirror Reflecting Light Source

A Greenough's binocular light microscope. The microscope has two eyepieces to view the sample with both…

"The intersection of the principal rays lies in front of the object, and consequently objects in front of the plane focused for will be projected on E magnified and the objects lying behind it diminished ("hypercentric" transmission). It produces a perspective representation entirely opposed to ordinary vision." &mdash;Encyclopaedia Britannica, 1910

Hypercentric Transmission in Microscopic Objective

"The intersection of the principal rays lies in front of the object, and consequently objects in front…

An adjustment screw diagram used to raise or lower microscope slightly. The series of screw and springs are used to move the microscope, B.

Leitz Micrometer Adjustment Screw for Microscope

An adjustment screw diagram used to raise or lower microscope slightly. The series of screw and springs…

A petrographic light microscope used to identify thin layered rocks and minerals. The microscope have two polarizer filter beneath the sample, with circular rotating stage.

Petrographical Light Microscope with Mirror and Eyepieces

A petrographic light microscope used to identify thin layered rocks and minerals. The microscope have…

"The image produced by a microscope formed of two positive systems is inverted, the objective L1 tracing from the object OO1 a real inverted image O'O'1, and the eyepiece L2L2 maintaining this arrangement." &mdash;Encyclopaedia Britannica, 1910

Ray Transmission in Compound Microscope with a Positive Ocular

"The image produced by a microscope formed of two positive systems is inverted, the objective L1 tracing…

An illustration of a compound microscope that produces upright image using negative eyepiece. The image is focused onto a concave lens, instead of convex lens, to diverging light.

Ray Transmission in Compound Microscope with a Negative Eyepiece

An illustration of a compound microscope that produces upright image using negative eyepiece. The image…

"The long lever D is pressed to one side by the screw F, and is thus turned round the in E. On the tube very near to pin E is cylinder C, which by the action of the screw F is very slightly raised or lowered." &mdash;Encyclopaedia Britannica, 1910

Swift and Son Micrometer Adjustment Lever for Microscope

"The long lever D is pressed to one side by the screw F, and is thus turned round the in E. On the tube…

A light reflection diagram of a light microscope using a mirror. The mirror is used in a microscope to provide light for the sample. The light source hits the mirror, then gets reflected onto the small condenser lens on the stage.

Microscope Mirror Illumination by Light Reflection

A light reflection diagram of a light microscope using a mirror. The mirror is used in a microscope…

Illustration showing Abbe illuminating apparatus with condenser. The mirror, m, reflects light from the light source to provide light for viewing the specimen. The reflected light is passed through the condenser then onto the specimen.

Abbe Microscope Mirror Illumination by Light Reflection with Condenser

Illustration showing Abbe illuminating apparatus with condenser. The mirror, m, reflects light from…

Opera glasses, also known as theater binoculars or Galilean binoculars, they are compact, low power optical magnification devices, usually used at performance events, whose name is derived from traditional use at opera performances. Magnification power below 5x is usually desired in these circumstances in order to minimize image shake and maintain a large enough field of view. A magnification of 3x is normally recommended. The design of many modern opera glasses of the ornamental variety is based on the popular lorgnettes of the nineteenth century

Opera Glass

Opera glasses, also known as theater binoculars or Galilean binoculars, they are compact, low power…

An illustration of the position and the size of the image viewed by the eye. The eye approximates the the height of the image. The image's height is the hypotenuse of the triangle, creating an angle with the eye. This image is then reflected upside down in the eye.

Position and Size of Image for Eye Optics

An illustration of the position and the size of the image viewed by the eye. The eye approximates the…

"If y be the object the image appears to a normal eye situated behind the system L with passive accommodation at a very great distance under the angle w'. Since H' P&#61; F O, &#61; y, from the focal length of the simple microscope is the image side focal length." &mdash;Encyclopaedia Britannica, 1910

Optical Position and Size of Image Through Magnifying Glasses

"If y be the object the image appears to a normal eye situated behind the system L with passive accommodation…

"The intersection of the principal rays in this case lies in the middle of the entrance pupil or of the exit pupil. By head and eye motion the various parts of the whole field can be viewed one after another." &mdash;Encyclopaedia Britannica, 1910

Optical Position of Diaphragms using Lens

"The intersection of the principal rays in this case lies in the middle of the entrance pupil or of…

Double Porro prism systems are used in small optical telescopes to re-orient an inverted image, and especially in many binoculars where they both erect the image and provide a longer, folded distance between the objective lenses and the eyepieces.

Porro Prism

Double Porro prism systems are used in small optical telescopes to re-orient an inverted image, and…

"In photometry (measure of light), a mounting for an incandescent lamp ... Rotator. The lamp to be tested is mounted upon a revolving spindle, ss, current being supplied through the brushes bb. The axis of rotation may be varied by turning the spindle about the horizontal shaft a." -Whitney, 1911

Rotator

"In photometry (measure of light), a mounting for an incandescent lamp ... Rotator. The lamp to be tested…

"An instrument described by Foucault for transmitting a beam of light along the optical axis of a fixed horizontal telescope."&mdash;Finley, 1917

Siderostat

"An instrument described by Foucault for transmitting a beam of light along the optical axis of a fixed…

"O' is the virtual image of O formed at a spherical surface of centre C and radius CS." &mdash;Encyclopaedia Britannica, 1910

Virtual Image Formed on Spherical Surface

"O' is the virtual image of O formed at a spherical surface of centre C and radius CS." —Encyclopaedia…

A large dissecting stand with magnification eyepiece and mirror reflecting the light source. The stand is useful for dissecting small organisms.

Large Dissecting Stand with Magnification Eyepiece Mirror Reflecting Light Source

A large dissecting stand with magnification eyepiece and mirror reflecting the light source. The stand…