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74 terms

Photonics Dictionary

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alignment telescope

An optical tooling instrument consisting of an objective lens, a focusing lens, an optical micrometer, a reticle and an eyepiece. The alignment telescope projects a precise line of sight to which a...

astronomical mirror

An astronomical mirror, also known as a telescope mirror or primary mirror, is a key component of a reflecting telescope. It serves as the primary optical element responsible for gathering and...

astronomical telescope

An astronomical telescope is a type of optical instrument designed to gather and magnify light from distant celestial objects for observation and analysis. It typically consists of two main optical...

autocollimator

An autocollimator is an optical instrument used for measuring small angular deviations with high precision. It operates on the principle of autocollimation, where a light source is directed onto a...

auxiliary telescope

A low-power telescope placed at the eyepiece of an optical system to increase overall magnification. Most often used to evaluate image quality.

bench -> optical bench

A support for optical parts comprising a solid bed that permits precise longitudinal movement of one component relative to the others, and a number of sliders equipped with holders for lenses, lamps,...

Bertrand lens

A small convergent lens, located between the objective and eyepiece of a microscope, that focuses an image of the upper focal plane of the objective in the focal plane of the eyepiece. It is commonly...

binocular microscope

A microscope designed with two eyepieces (oculars), permitting the use of both eyes when viewing through the instrument.

Brucke loupe

A telemicroscope in which a negative eyepiece is used to produce erect images.

clear eye distance

In a visual optical system, the axial distance from the last mechanical surface of the eyepiece to the exit pupil.

coherent fiber bundle

A coherent fiber bundle (CFB), also known as a coherent fiber optic bundle, is an assembly of multiple optical fibers arranged in a specific geometric pattern to maintain the spatial coherence of...

coincidence prism

A compound prism consisting of an assembly of small prisms cemented together that is used in a coincidence rangefinder to transmit the images from the two objectives to a single eyepiece for viewing.

coincidence rangefinder

An optical instrument used to determine the distance to a target being viewed. Two similar optical systems view the target via 45° mirrors at the ends of a fixed baseline. One system creates the...

comparator

1. An eyepiece or magnifier with a scale at its image plane. That scale is placed in contact with an object, permitting direct measurement of its size. 2. Also called traveling stage and traveling...

comparison microscope

Two microscopes that are coupled on a common stand, the two images being projected side by side in the field of view of a single eyepiece for comparison.

compensating eyepiece

A microscope eyepiece designed for use with apochromatic objectives. Since apochromatic objectives are undercorrected for lateral color, these eyepieces are overcorrected for that aberration.

compound microscope -> microscope

An instrument consisting essentially of a tube 160 mm long, with an objective lens at the distant end and an eyepiece at the near end. The objective forms a real aerial image of the object in the...

dichroscopic eyepiece

An eyepiece used in a polariscope or polarizing microscope to give a comparison view of the same object under illumination by the two complementary rays of polarized light.

diopter movement

The adjustment of the eyepiece of an instrument to provide accommodation for the eyesight differences of individual observers. The axial distance through which the eyepiece must be moved, to provide...

diopter scale

A scale located on the eyepiece focusing screw and used to measure the amount of defocusing of the eyepiece in diopters. The reciprocal of the image distance in meters is a measure of the amount of...

dioptometer

A telescopic system having an eyepiece, a reticle and an objective. The instrument measures wavefront power in diopters.

distance of distinct vision

The near-point distance of the normal eye. The value of 10 in. or 25 cm is normal. This value is used in evaluating the designated magnification of a simple magnifier or eyepiece.

eikonometer

A scale attached to a microscope eyepiece that is seen superimposed on the image and that is used to measure the dimensions of the viewed object.

erecting eyepiece

An eyepiece combined with an erecting prism or lens system.

Erfle eyepiece

A telescopic eyepiece comprising five or six simple lenses in the form of three doublets or two doublets and a singlet.

eye lens

The lens of an eyepiece nearest the observer's eye.

eyepiece

Also known as ocular. The lens system used between the final real image in a visual optical system and eye. It acts as an image magnifier. Many types of eyepieces are known; e.g., the Huygens used in...

eyepiece micrometer -> measuring eyepiece

Also known as an eyepiece micrometer. A microscope eyepiece that has a finely divided scale ruled or photographed on a section of transparent glass, and located in the focal plane. The dimensions of...

fiberscope

An optical instrument consisting of an objective lens, a coherent (usually flexible) fiber bundle and an eyepiece to examine the output of the fiber bundle.

field lens

1. A lens situated at or near the plane of an internal image to project the aperture of a previous objective or erector upon the aperture of a following lens. 2. A lens at or near the plane of a...

filar eyepiece

A measuring eyepiece with a screw-micrometer-driven crosshair used to measure the size of the image.

flexible imagescope -> fiberscope

An optical instrument consisting of an objective lens, a coherent (usually flexible) fiber bundle and an eyepiece to examine the output of the fiber bundle.

flying spot microscope

A microscope that uses a flying spot scanner, directed through the eyepiece, as a light source to determine the features of a transparent specimen. The flying spot is modulated by the varying density...

focus

1. The focal point. 2. To adjust the eyepiece or objective of a telescope so that the image is clearly seen by the observer. 3. To adjust the camera lens, plate, or film holder so that the image is...

Galilean telescope

A refracting telescope that yields an erect image by the use of a positive lens for its objective and a negative lens for its eyepiece.

goniometer eyepiece

An eyepiece having a rotating index or cross wire linked to an external 360° scale to allow measuring of angles in an image.

grain isolating diaphragm

In a microscope, the diaphragm located between the Bertrand lens and the eyepiece, which is closed during conoscopic viewing to restrict the interference figures to that of a crystal lying on the...

Greenough microscope

A form of a stereoscopic microscope having paired objectives, prisms and eyepieces, and invented by H. Greenough.

Gregorian telescope

A telescope with an ellipsoidal secondary concave mirror that reflects rays from a parabolic primary mirror through an opening in the center of the primary, where the image is viewed with an eyepiece.

GRIN lens

A GRIN (gradient index) lens is a type of optical lens that utilizes a gradient in refractive index across its volume rather than having a uniform refractive index like conventional lenses. This...

Huygenian eyepiece

An ocular having two planoconvex lenses that are formed from similar glass and that are separated by a space equal to half the sum of their focal lengths. This eyepiece is free of lateral chromatic...

hyperplane eyepiece

An eyepiece similar to the Huygenian eyepiece, but having an eye lens that is a cemented doublet and that provides more lateral color correction.

image splitting eyepiece

An eyepiece having a special prism arrangement linked to a micrometer screw to allow reading of the angular relations between the two prism segments to be varied. When the prism faces are parallel,...

imagescope -> fiberscope

An optical instrument consisting of an objective lens, a coherent (usually flexible) fiber bundle and an eyepiece to examine the output of the fiber bundle.

Kellner eyepiece

An eyepiece consisting of a planoconvex field lens and a cemented doublet as the eye lens.

Keplerian astronomical telescope

A simple form of astronomical telescope that uses a fixed objective and a focusable eyepiece. The objective forms an intermediate image in the instrument, resulting in an image that appears upside...

kidney-bean effect

A dark region created by spherical aberration of an eyepiece's exit pupil. Because of the aberration, an observer's eye must be at different distances from the eyepiece to view different regions of...

lens bench -> optical bench

lensometer

An ophthalmic instrument used to measure the magnitude and direction of the maximum and minimum powers of a spectacle lens, and mark the optical center of the lens by an ink dot. When the lens to be...

Lippich prism

A small half-shade analyzer placed in the eyepiece of a polarimeter to determine the character of the polarized light emitted by the instrument. It consists of a Nicol prism situated so that it...

Photonics Dictionary