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lens Dictionary Terms

auto-iris lens
A device for automatic exposure control in which a motor-driven diaphragm adjusts the aperture in response to a signal from a photocell detecting ambient light.
Fizeau fringes
Fizeau fringes are interference fringes observed in an interferometer, specifically in a Fizeau interferometer. The Fizeau...
aplanatic lens system
A system that satisfies the Abbe sine condition, and is free from spherical aberration and coma.
reduced focal length
The ratio of the first focal length of a lens to the refractive index of the medium containing the incident light; the ratio...
neutralization
In optics, the process of combining two lenses having equal and opposite powers to produce a result having no power.
modulation transfer function analysis/measurement equipment
MTF analysis/measurement equipment refers to instruments and tools used to measure and analyze the modulation transfer...
glazing
The process whereby a spectacle lens is placed in a frame.
optical autocorrelator
An instrument used to test lenses by utilizing the optical transfer function. It consists of a HeNe laser, a beamsplitter...
flange focal distance
The distance between the locating surface of the lens mount and the image plane.
prism binoculars
A pair of telescopes with prismatically erected images, mounted side by side with the eyepieces at the interocular distance...
finished lens molding
A method used to produce precision spherical and aspheric molded glass lenses without grinding or polishing.
optical switching
Optical switching refers to the process of controlling the routing or transmission of optical signals within a network using...
clear aperture
The limited light-gathering area of an optical system. The area is normally restricted to an edge or outer surface of an...
fiberscope
An optical instrument consisting of an objective lens, a coherent (usually flexible) fiber bundle and an eyepiece to examine...
allyl diglycol carbonate
Commonly known as CR39, this thermosetting plastic is used in the casting of eyeglass lenses because of its toughness and...
motion picture camera
A camera equipped with a lens and a long length of perforated film, the latter being moved intermittently between exposures...
transmission sphere
A precision lens designed to convert the plane wavefront output of an interferometer to a spherical wavefront for the...
rolled edge
Also known as a turned-down edge. A rapid change of curvature near the edge in a lens or prism surface.
narrow-angle dark-field illumination
An imaging system designed to highlight small deviations in a planar reflective object such as a mirror. The system can be...
sign conventions
A convention that defines specific dimensions of an optical system, such as the image distance or radius of curvature of a...
collective lens
A convex or positive lens that serves to collect energy and direct it into subsequent system optics.
telephoto ratio
In a telephoto lens, the ratio of the overall length to the focal length of the lens. It is generally about 0.8 to 0.9 in...
component
1. A constituent part. It may consist of two or more parts cemented together, or with near and approximately matching...
plastic optics
The integration of plastic materials into optical applications. When the materials are refined into lenses, prisms and...
electron image tube
A cathode-ray tube that increases the brightness or size of an image or forms a visible image from invisible radiation. The...
terrestrial telescope
A telescope that produces an erect image. Erection is achieved either by a lens (for a long instrument) or a prism (for a...
adhesive
An intermolecular substance that serves to hold materials together. Two types are used in the optical industry: one, which...
custom optic
A custom optic refers to an optical component that is designed, manufactured, and tailored to meet specific requirements or...
core-coupled lens
A semispherical or conical lens created directly on the core of an optical fiber to focus light from a laser into the fiber...
center of curvature
The center of the sphere of which the surface of a lens or mirror forms a portion. Each curved surface of a lens has a...
radial astigmatism
The astigmatism in a lens system that results when light enters the system at an oblique angle.
lens meridian
A line passing through the center of a lens surface, from edge to edge.
geometric center
The physical center of the lens; it is on the axis of the lens, halfway between the front and rear vertex. It is sometimes...
output spectrum display
The direct computation of the Fourier transform of the space variant system output of an optical processor with a single...
polystyrene
A plastic used in molded optical components. Styrene elements can be combined with acrylic elements to produce achromatic...
bevel face width
The actual width of a bevel rather than its width projected along the lens aperture.
first principal point
The principal point of a lens relative to the object space.
angular aperture
The angle between the most divergent rays that can pass through the lens to form an image. In a birefringent crystal light...
symmetrical lens
A lens system made up of two sets of similar lenses, each of which compensates for many of the aberrations produced by the...
electromagnetic lens
An electron lens consisting of a homogeneous axial electric field and a magnetic field used in high-quality image tubes for...
overhead projector
A projector used to project transparencies. A horizontal 8 x 10-in. stage for writing or laying down preformed...
vertex power
The reciprocal of the back focal distance of a spectacle lens.
global optimization
A controlled random search process, such as generalized simulated annealing, that has been incorporated into many optical...
electric quadrupole lens
A device that uses four electrodes set in an alternating positive-negative polarity series to focus the beams of charged...
oleophobic
Oleophobic is a term used to describe substances or materials that repel or resist oils. The word oleophobic comes from the...
fiber-coupled LED
A fiber-coupled LED (light-emitting diode) refers to an LED device that is optically coupled to an optical fiber for the...
negative lens
zone plate
A plate of glass, usually a photograph, on which there is a central spot surrounded by concentric annular zones, alternately...
Gaussian beam optics
The area of optics that deals with the propagation of Gaussian laser beams in free space, or any general medium - i.e....
ocular surface
That surface of a lens located nearest to the eye.
complex lens
A lens made up of a number of lens elements arranged into two or more groups.
center of perspective
That viewpoint at which the angular subtenses of points in the picture are identical to angular subtenses of the original...
lens molding
The production of rough glass lens blanks that are pressed while red-hot to the approximate size and shape of the finished...
Kellner eyepiece
An eyepiece consisting of a planoconvex field lens and a cemented doublet as the eye lens.
relay lens
A lens or lens system used to transfer a real image from one point within an optical system to another, with or without...
beam positioner
A device (e.g., prisms, lenses, tubes) used to align a beam in a system.
lenslets
A matrix of miniature lenses, molded or formed onto a common base.
rear focusing
A type of internal focusing in which only the lens elements closest to the rear of the lens barrel are moved.
diaphragm
A flanged or plain ring with a restricted aperture, located in an optical system at any of several points, that cuts off...
anamorphic lens
A lens, usually having one or more cylindrical surfaces, used to produce distorted images and later to restore them to true...
phototheodolite
A camera equipped with angular scales in altitude and azimuth. The scale readings are imprinted on the film when an exposure...
aplanat
Also known as aplanatic lens. A lens corrected for spherical aberration and coma.
degreaser
A tank with a boiling solvent at the bottom and a ring of cold piping higher up that condenses the liquid and returns it to...
Ramsden eyepiece
An eyepiece consisting of two planoconvex lenses of the same focal length, with facing convex surfaces.
member
In a lens system, a group of elements considered as an entity; either a front or rear member depending on whether it is...
eccentric mounting
A lens mounting with eccentric rings that may be rotated to shift the axis of the lens to a prescribed position.
Fresnel number
In a lens, the square of the radius of its aperture divided by the product of the focal length and the wavelength. It...
dispersive lens
 curvilinear distortion
A lens aberration in which the focal length varies radially outward from the center of the field. It has the effect of...
burnishing
The process of lapping a thin edge of metal over the bevelled edge of a lens to maintain it within its cell.
thin lens relationships
Formulas designating the relationships between image distance, object distance, focal length, refractive index, etc., of a...
stereomicrography
Technique that provides two stereographic views of an object that are larger than the object itself, by means of mutually...
stick machine
A polishing machine with a lens mounted on a wooden stick, allowing a very wide sweep. It is used to polish hemispherical or...
edge
The flat or angled surface, usually fine-ground, that limits the aperture of a lens or prism surface.
hyperplane eyepiece
An eyepiece similar to the Huygenian eyepiece, but having an eye lens that is a cemented doublet and that provides more...
bevel
A chamfer ground on the edge of a lens or prism. Bevels are used to prevent chipping or to achieve a mechanical fit.
fish-eye lens
A type of wide-angle lens that has an angular field above 140° and that exhibits barrel distortion. The most commonly...
spherometer
An instrument for measuring the radius of curvature of a spherical lens or mirror surface. It may consist of a ring resting...
machine vision system
A machine vision system is an integrated combination of hardware and software components designed to capture, process, and...
chromatic aberration
Chromatic aberration is an optical phenomenon that occurs when different wavelengths (colors) of light are refracted by a...
sun-tracking concentrator
Controlled beam technology that introduces beams of sunlight through holes in a roof that are relayed throughout the...
light field
The term light field refers to the spatial distribution of light rays traveling in all directions through a given space. It...
edge thickness difference
The maximum variation in thickness of a lens as measured around a diameter centered on the optical axis. The ETD divided by...
aplanatic surface
An aplanatic surface is an optical surface that is specifically designed or shaped to minimize spherical aberration and...
absolute magnification
The value of the distance of distinct vision, minimum focusing distance or near point, divided by the focal length of the...
cosine fourth law
A formula indicating that, for an imaging lens system, the image brightness for off-axis points will fall off at a rate...
photochromic
Photochromic refers to a property exhibited by certain materials, typically organic compounds or dyes, which undergo...
dioptrics
The branch of optics that deals with the study of the refraction of light, particularly by the transmitting medium of the...
scanning electron microscopy
Scanning electron microscopy (SEM) is an advanced imaging technique used in microscopy to obtain high-resolution,...
concave lens
 SELFOC fiber
Derived from "self-focusing,'' Nippon Sheet Glass Co. (NSG) of Japan's trade name for graded-index fiber rods with parabolic...
Gauss lens
A telescope objective with excellent spherochromatic correction, consisting of a meniscus crown and a meniscus flint, both...
vitreous humor
The transparent fluid that fills the portion of the eye between the eye lens and the retina (the posterior chamber).
iris
The adjustable membrane located just in front of the crystalline lens within the eye. The iris gives the eye its color. See...
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...
optical coatings
Optical coatings are thin layers of materials applied to optical components, such as lenses, mirrors, filters, and prisms,...
aqueous humor
The transparent fluid that fills the portion of the eye between the cornea and the eye lens (the anterior chamber).
optical glass
Optical glass refers to a type of glass specifically engineered and manufactured for use in optical components and systems,...
unipotential electrostatic lens
A simple electrostatic lens with a focus controlled by a single potential difference.
Cooke objective
A telephoto lens form noted for its lack of distortion.
interchangeable lens
A lens that has a mount, usually bayonet or screw type in design, that can be used on a camera in place of lenses with the...
myopia
A vision defect commonly referred to as nearsightedness. The defective condition results when the image of a distant object...
aplanatic points
Aplanatic points refer to specific points in an optical system where certain aberrations, such as spherical aberration or...
nodal points
Of all the rays passing through a lens from an off-axis object point to its corresponding image point, there is always one...
block
A supporting member used to hold optical parts during grinding and polishing. It also describes the assemblage of optical...
color correction
The reduction in longitudinal, lateral and secondary chromatic aberrations in a lens or lens system.
lens transmission
The ratio of the intensities of a light bundle before and after passing through the lens.
f number (f/#)
The expression denoting the ratio of the equivalent focal length of a lens to the diameter of its entrance pupil.
second principal point
The principal point of a lens relative to image space.
holographic lens
A photographic recording of interference patterns between a plane wave and a spherical wave on a high-resolution...
layout
In the optical shop, the process of positioning and marking a blank or lens before surfacing, cutting and edging.
bayonet coupling
A coupling mechanism designed to quickly lock a connector into an adaptor or a lens into a lens mount. Typically coupling is...
optical system
A group of lenses, or any combination of lenses, mirrors and prisms, so constructed as to refract or reflect light to...
diffractive optics
Optical elements that use diffraction to control wavefronts. Diffractive optical elements include diffraction gratings,...
double-convex lens
A converging lens with both surfaces convex.
shading
1. The sorting of lenses by their color. 2. In an optical system, an irradiance or brightness gradient in the image that is...
image distance
The distance from the last surface of a lens system to the image. For a thin lens system, this distance is equivalent to the...
power
With respect to a lens, the reciprocal of its focal length. The term power, as applied to a telescope or microscope, often...
lens
A lens is a transparent optical device that focuses or diverges light, allowing it to pass through and form an image. Lenses...
quadrupole lens
A device used in electron microscopes and particle accelerators to focus electron beams by the arrangement of four...
Sonnar lens
A photographic objective that uses the thick meniscus principle to obtain its power. It is designed to photograph small...
stacked-diode laser
A type of laser used when a great amount of power is required. Avoiding the bulk of large numbers of optical lenses, this...
alignment telescope
An optical tooling instrument consisting of an objective lens, a focusing lens, an optical micrometer, a reticle and an...
SELFOC lens
 microcircuit manufacturing
The formation of transistors, diodes, capacitors, resistors and other electronic elements directly on a flake of silicon by...
flat-field lens
A lens that focuses on a flat plane because its field of curvature is close to zero.
optical work
The degree to which the surface of a lens causes an incident ray of light to bend, or the amount of convergence or...
evaporagraph
A sensor generally used for infrared imaging. It consists of two chambers separated by a thin, blackened membrane. An...
meniscus anastigmat
An anastigmatic lens with a thick meniscus construction that flattens the field and corrects chromatic and spherical...
aspheric
Not spherical; an optical element having one or more surfaces that are not spherical. The spherical surface of a lens may be...
wide-angle lens
A wide-angle lens is a type of camera lens that has a shorter focal length than a standard or normal lens, allowing it to...
cardinal points
Focal, nodal or principal points of a lens. If the respective distances of the object and image are measured from the...
principal axis
A straight line connecting the curvature centers of the refracting lens surfaces. In a mechanical sense, a line joining the...
spotted tool
A metal tool used to hold a number of lens blanks during grinding and polishing.
hologon
A multifaceted holographic disc that is rotated by a motor to deflect incident light to a scanning system's lens.
diamond turning
Diamond turning, also known as diamond machining or diamond cutting, is a precision machining process used to produce...
marginal rays
Also referred to as the axial ray (or a-ray), a marginal ray originates from the axial point of the object and passes...
kinoform
Lens which, by altering the phase, efficiently images through a holographic process.
Fourier transform hologram
A hologram formed by the recording of a plane object situated in the focal plane of a lens so that each object gives rise to...
infrared optical material
The range of materials that, unlike glass, may be used in the infrared. Water-soluble salts, such as cesium iodide, and...
magnetic lens
An arranged series of coils, magnets or electromagnets disposed in such a way that the resulting magnetic fields generate a...
terahertz spectrometer
A terahertz spectrometer is a scientific instrument used to measure and analyze the properties of materials in the terahertz...
germanium crystal
Germanium crystal refers to a crystalline form of the element germanium (Ge), which is a metalloid and semiconductor...
rectilinear
In a straight line. When applied to a lens, it indicates that images of straight lines formed by the lens are not distorted.
C-mount
A standard lens interface initially made for 16mm movie cameras and now used primarily on closed-circuit television cameras....
total image runout
Image displacement by a decentered lens, rotated on a chuck whose axis of rotation passes through the geometrical center of...
hydrogel
A hydrogel is a three-dimensional network of polymer chains that are hydrophilic, meaning they have a strong affinity for...
dielectric lens
A lens made up of a dielectric material that is capable of influencing radio waves much in the same way an optical lens...
optical manufacturing tools and machinery
Optical manufacturing tools and machinery encompass a wide range of equipment, instruments, and systems used in the...
camera
A light-tight box that receives light from an object or scene and focuses it to form an image on a light-sensitive material...
Cassegrain lens system
A two-mirror lens design used in astronomical telescopes, the primary being a parabola, the secondary a smaller hyperbola....
GRIN lens
A GRIN (gradient index) lens is a type of optical lens that utilizes a gradient in refractive index across its volume rather...
microfiche
A small card (10 x 15 cm) that has been treated with a photographic emulsion to record and store the microimages of...
f-Theta lens
A family of lenses commonly used in scan systems for reading or printing documents. The lens must be designed such that the...
Judas optics
A small defocused Galilean telescope mounted in a hole in a door. Viewed from inside through the positive lens, a wide-angle...
optical assembly
An optical assembly refers to a collection of optical components that are carefully arranged and aligned to perform a...
scanning disc
In field-sequential color television, the rotating tricolor disc placed between the subject and the lens, or between the...
holographic camera
A holographic camera, also known as a holographic imaging system or holographic recorder, is a specialized device used to...
microscope
An instrument consisting essentially of a tube 160 mm long, with an objective lens at the distant end and an eyepiece at the...
segment width
In spectacle lenses, the lateral measurement of a multifocal segment at its maximum width.
crown glass
One of the two principal types of optical glass, the other being flint glass. Crown glass is harder than flint glass, and...
aspheric lens
An aspheric lens is a type of lens whose surface profiles deviate from the traditional spherical shape. Unlike spherical...
fan
A set of rays through a lens originating at a common point and contained in one plane.
axial bundle
A bundle of rays that originates from an object point on the optical axis of a lens system.
cleared out
Denoting a finished circular edge. A decentered lens is adjusted on a centering chuck so that its image runs true, and the...
pitch polishing compound
Pitch for polishing mixed with other materials to give it the right viscosity so that it will follow the fine-ground lens...
meniscus lens
A lens that has one convex surface and the other concave.
corrected lens
A compound lens, the dimensions and materials of which have been so chosen that the lens is appreciably free of aberrations.
plano lens
himawari
A system of Japanese origin that utilizes Fresnel lenses and a fiber optic network to transmit sunlight to otherwise...
resolution
1. In optics, the ability of a lens system to reproduce the points, lines and surfaces in an object as separate entities in...
camera obscura
A forerunner of the modern camera, this instrument had a focusable lens that produced a sharp image on the enclosure...
injection-mounted assembly
A process by which a plastic cell is molded around a glass lens or lenses to create a mount, eliminating the metal barrel...
first-side toric
The process of grinding the toric surface of a single vision sphero-cylindrical lens.
magnetorheological finishing
Magnetorheological finishing (MRF) is a precision optics polishing technique used for shaping and finishing optical surfaces...
optical materials
Optical materials refer to substances or compounds specifically chosen for their optical properties and used in the...
telephoto power
The ratio between the focal length of a lens having a longer focal length than that of the standard lens used with a camera,...
loupe
A low-power (2x to 10x) magnifier consisting of a single positive lens assembly.
lenticular stereo photography
A type of stereoscopic photography in which a pair of lenses focuses a pair of images, relative to the positions of the two...
microscope immersion fluid
The liquid used in microscopy to fill the space between the high-power objective lens and the microscope slide in order to...
zonal aberration
Spherical or chromatic aberration in a lens having a wide aperture. It is present because the refracting power varies for...
immersed detector
A radiation detector with its active medium mounted within a lens that focuses the radiation signal. The improvement in...
microscope eyepiece
An eyepiece located at the near end of the microscope tube. It often is a simple Huygens eyepiece, but compensating and...
principal point
The intersection of the principal plane and the optical axis of a lens.
focometer
A device used to measure the focal length of an optical system or lens.
minimum object distance
Minimum object distance, often abbreviated as MOD, refers to the closest distance at which a camera lens or optical system...
ophthalmoscope
Also referred to as a funduscope, an ophthalmoscope is a specialized instrument used by ophthalmologists for observing and...
radiuscope
A microscope to which a beamsplitter and illuminated reticle have been added that is used to measure contact lenses.
Hartmann test
A test for spherical aberration, coma or astigmatism in which incident rays from a point source are isolated by small holes...
convertible lens
Any lens with at least two lens elements, each of which can be used singly or in combined configurations.
nodal bench
A bench with instrumentation including a collimator, a microscope, positioners and a nodal slide used to rotate a lens about...
focal plane
A plane (through the focal point) at right angles to the principal axis of a lens or mirror; that surface on which the best...
liquid crystal on silicon
Liquid crystal on silicon (LCoS) is a display technology that combines liquid crystal materials with silicon-based...
multiple lens block
A block that can hold more than one lens or blank.
cathode-ray tube faceplate
A fiber optic end plate constructed by drawing a bundle of parallel fibers embedded in glass and cutting it into thin...
stick marks
The fine scratches formed when, in hand centering, the forked stick used to move the lens on the chuck marks the rotating...
holographic optical element
A component used to modify light rays by diffraction; the HOE is produced by recording the interference pattern of two laser...
infrared optic
Infrared optics refer to optical components and systems designed to manipulate and control infrared (IR) light, which lies...
calcium fluoride
An optical material used in place of crown glass to produce lenses with extraordinary correction of chromatic aberrations....
far point (of vision)
The object distance at which the eye is focused with the eye lens in a neutral or relaxed state.
Rayleigh criterion of resolving power
When a lens system with a circular aperture is free of aberrations, the image of a point object will appear as a disc of...
anamorphote lens
A lens that distorts an optical image.
tessar lens
A lens similar to the Cooke triplet anastigmat, with the rear crown achromatized for improved coverage and definition. It is...
split lens interference
The interference of the two real images formed by a Billet split lens.
lenticular image dissection
A method of image dissection whereby a lens transfers images onto a lenticular plate that in turn illustrates the images as...
sine wave object
An object that has a sinusoidal variation of luminance. Its image will have a sinusoidal variation of illuminance and the...
converging meniscus
A converging lens with one convex and one concave surface.
optical dummy
1. A lens formed to a desired curve and used to form a polisher. 2. A piece of glass included in a block to fill out the...
negative carrier
The structure that holds the photographic negative in a proper position that is both flat and parallel to the lens plane, as...
photon sieve
A photon sieve is an optical device used in the field of optics and imaging. It's designed to focus and shape light,...
Geometrical optics
The area of optics in which the propagation of light is described by geometrical lines (or rays) governed by Fermat's...
planetary camera
A camera system used for microphotography in which the document to be recorded is on a flat bed, perpendicular to the lens...
biconvex lens
A lens having each of its outer faces curved outward.
optically compensating zoom system
A variable focal length lens system that retains the object in focus as one or more lenses move as a unit along its optical...
transposition
In optics, the changing of the relative curves of a lens without changing its refractive value.
biplanar lens
Electron lens consisting of an homogeneous axial electric field.
vertical imbalance
The difference in base up or down prism power at corresponding points located on the two lenses of a pair of spectacles.
convex lens
 spherocylinder
A lens or lens surface that is a combination of a sphere and cylinder.
cathode-ray tube lens
A high-quality, narrow-angle lens of high aperture designed for low magnification in the recording of cathode-ray tube...
double-image prism
A prism block that, when used with a lens, is capable of forming two images of one object.
centration
In a perfectly centered lens, the mechanical axis (defined by the ground outside the diameter of the lens) is made to be...
micro-optics
Micro-optics refers to the design, fabrication, and application of optical components and systems at a microscale level....
principal plane
In a lens or lens system, that surface at which the projections of an entering and exiting ray intersect. Also known as the...
angular spectrum approach
The angular spectrum approach is a mathematical and computational technique used in the field of optics to analyze and...
soft-focus lens
A lens that exhibits spherical aberration when used at large aperture settings, and that forms an image with a slightly...
axial gradient
In gradient index optics, a gradient profile in which the refractive index varies along the direction of light propagation,...
third-order theory
Calculations of lens aberrations whereby the first two terms of the series expansion are the only ones employed....
fiber-lens fusing
A method of terminating optical fibers by forming a lens directly on the end of the fiber, eliminating the need for precise...
Fraunhofer hologram
A far-field pattern holographically reproduced image that is categorically considered with three-dimensional lensless...
triplet
A lens assembly made up of three lens elements that may or may not be cemented.
autocollimating spectrograph
A spectrograph in which the refracted beam returns almost along the path traveled by the incident beam, and is brought to a...
hyperfocal distance
That object distance at which a camera must be focused so that the far depth of field just extends to infinity. The near...
centered curve
The surface curvature designed to reduce the marginal error found in the periphery of a spectacle lens.
Petzval lens
A high-speed, narrow-field lens consisting of two achromats spaced about the aperture stop. Its uses include portrait...
apochromat
An apochromat, often referred to as an apochromatic lens or apochromatic objective, is a type of optical system designed to...
lens measure
A tool used to determine the curvature of a lens surface in terms of dioptric power. See lens watch; spherometer.
negative meniscus lens
A negative powered lens with one surface convex and the other concave, the latter having the greater curvature. It also is...
achromat
An achromat, in the context of optics, refers to a type of lens or lens system designed to reduce chromatic aberration....
molded blank
A blank whose basic surface curves are attained by heating and forming a given weight of raw glass; a rough glass blank...
body
In the optical field, a piece of glass to which a lens or prism is cemented. The unit is ground and polished as a whole to...
brass gauge
A sheet of thin brass, one edge of which has been accurately cut to a known and marked circular radius. It is used to check...
metallographic microscope
A specially designed microscope for observing the etched surface of a polished metal specimen. The specimen is often laid...
radial gradient
In gradient index optics, a gradient profile in which the index varies in a direction perpendicular to the optical axis....
reversed telephoto lens
Canada balsam
A resin obtained from the balsam fir, Abies balsamea, used as a lens cement.
duplet lens system
An optical system having two sets of components separated by an air space, while successive lenses in each set are cemented...
decentration aberration
An aberration occurring in a lens system when one or more of the centers of curvature of the optical surfaces do not...
periscopic lens
Two simple meniscus lenses arranged symmetrically on either side of the aperture stop, providing reduced coma, lateral color...
motion controller
In optics, a motion controller refers to a device or system that precisely controls the movement of optical components, such...
orthoscopic eyepiece
A telescopic eyepiece that produces a field of view between 40° and 50°. The eyepiece consists of a single element...
collector
A positive lens located at or close to an intermediate image plane. The collector refracts off-axis light bundles, directing...
epoxy
Common name for a variety of adhesives used for lens bonding, fiber optic splicing and other photonics applications. The...
conjugate ratio
The ratio between the object distance and the image distance measured along the principal axis of a lens or mirror. An...
illuminated magnifier
A magnifying lens fitted with a battery-operated lamp by which an object can be conveniently illuminated during observation.
hill cloud lens
A fish-eye lens designed to photograph cloud formations over the entire visible sky.
microscope objective
The lens located at the object end of a microscope tube. A wide range of objectives is available, including simple...
image plane holography
A hologram in which the image of an object, or the object itself, is located near the hologram recording plane, for optimum...
doublet
1. A compound lens consisting of two elements. If there is an air space between the elements it is called an...
compound lens
A lens composed of two or more separate elements of optical glass that may or may not be cemented together. The surfaces of...
Maddox rod
Lenslike composition of stacked glass cylinders through which a spot of light appears as a streak perpendicular to the...
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...
astigmatism
A lens aberration that results in the tangential and sagittal image planes being separated axially.
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...
iconometer
An instrument in which an object's image, produced by a lens of known focal length, is used to determine the object's...
adapter
1. In optics, the housing, usually cylindrical, that contains the lenses and iris diaphragm of a camera. 2. In fiber optics,...
artificial star
A point source of light used for the test and evaluation of image quality. May be a backlit pinhole in an otherwise opaque...
optical staining
With respect to microscopy, also called dispersive staining, optical staining the projection of colors through areas of a...
flare
Nonimage-forming light, concentrated or diffuse, that is transmitted through the lens to the image. It is frequently the...
optical cement
A permanent, transparent, and highly transmissive adhesive capable of withstanding extreme temperatures that is applied to...
glass marking ink
Ink used for writing on glass, and also for blackening the edges of lenses to prevent reflection. In the latter case, the...
critical aperture
In an optical system, the aperture size at which the lens gives its best overall performance.
relay condenser
A form of lens assembly used in a projection system to maximize efficiency and assure uniform illumination of the object...
lensometer
An ophthalmic instrument used to measure the magnitude and direction of the maximum and minimum powers of a spectacle lens,...
double-concave lens
A diverging lens with both surfaces concave.
magnesium fluoride
A colorless, crystalline compound whose low refractive index (n = 1.38) makes it effective as a lens antireflection coating...
spindle
A loose term for a single polishing machine. In a lens factory it is the minimum unit of production.
wedge tolerance
A method of specifying the allowable edge-thickness difference or decentering of a lens.
turret
A rotating plate containing two or more lenses to provide a rapid interchange.
mechanical tube length
In a microscope, the physical distance between the focal points of the objective lens and the eyepiece. The standard tube...
lens element
One optical element of a multielement lens. See optical element.
cineradiography
The photographic filming of the action of x-ray images recorded on a fluorescent screen by means of large lens apertures and...
focal collimator
A collimator having, at one end of a tube, an objective lens, and at the other, a reticle with a pair of spaced lines...
axicon
An optical device that produces a line image lying along the axis from a point source of light; therefore, it has no...
bellows
In optics, a collapsible structure situated between the lens and film of a camera to allow variation of the distance between...
intraocular lens
A lens that is implanted within the eye to replace the eye lens, which has been removed because of cataract or other defect.
grain isolating diaphragm
In a microscope, the diaphragm located between the Bertrand lens and the eyepiece, which is closed during conoscopic viewing...
aberration sensor (wavefront sensor)
Designed for the function of optical wavefront analysis. Shack-Hartmann camera aberration sensors use a lens array to image...
spherochromatism
A lens aberration. The chromatic variation of spherical aberration.
perfect lens
A theoretical, ideal lens capable of producing perfect images. Used as a lens design and analysis tool to image collimated...
cartesian lens
A lens, one surface being a cartesian oval, that produces an aplanatic condition.
aspheric mirror
An aspheric mirror is an optical mirror surface that deviates from the shape of a perfect sphere, having a non-spherical...
focus lamp
An incandescent or carbon arc lamp designed with a stable and compact arc or filament that permits it to be used as a light...
fluorographic camera
A camera with a very high aperture lens or mirror system for photographing x-ray fluorescent screen images, mainly to save...
simple magnifier
A short focal length (less than five inches) positive lens used to produce a magnified image of the object being viewed....
concentric lens
A lens having surfaces whose centers of curvature coincide.
convergent beam sensing mode
A type of photoelectric proximity mode sensing incorporating a lens system to focus the light from the emitter in a small,...
immersion oil
An oil required by oil-immersion objectives that is applied between the exterior of the objective lens and a cover glass or...
high-speed movie camera
A camera designed to record at rates exceeding 50 fps. For frame rates up to about 500 fps, an ordinary pull-down mechanism...
sapphire
Sapphire can refer to either a gemstone or a specific type of crystalline material commonly used in various industrial...
cylindrical lens
A cylindrical lens is an optical component that has different curvatures along its two orthogonal axes, resulting in a shape...
ringlight
A circular lamp or bundles of optical fibers placed around the perimeter of an objective lens to illuminate the object field...
retrofocus lens
Also known as reversed telephoto lens. A lens consisting of an ordinary objective with a negative component near its front...
image orthicon
A camera tube widely used in television broadcasting. It consists of three sections within a single vacuum envelope. 1. A...
astronomical telescope
An astronomical telescope is a type of optical instrument designed to gather and magnify light from distant celestial...
plasmonics
Plasmonics is a field of science and technology that focuses on the interaction between electromagnetic radiation and free...
multifocal lens
A lens with internally adjustable elements to produce a range of focal lengths. Unlike a true zoom lens, a multifocal lens...
planoconvex lens
A lens that has one plane surface and one convex surface.
spurious resolution
A phenomenon that causes the details in an image to appear at a spatial frequency higher than that at which the contrast...
center thickness
The lens thickness measured at the optical axis.
electron-beam lithography system
An electron-beam lithography (EBL) system is a sophisticated nanofabrication tool used in the semiconductor industry and...
first-side meniscus
The process of grinding the concave surface of a single-vision spherical lens.
optical phase distortion
Optical phase distortion refers to a phenomenon where the phase of an optical wavefront is altered as it propagates through...
lens testing equipment
Lens testing equipment refers to a range of specialized tools and instruments used to evaluate the optical performance,...
telecentric lens
There are three types of telecentric lenses: -Image-space telecentric lenses are those in which the aperture stop is...
electron micrograph
The photographic recording of images produced by the electrons from an electron microscope. The electron beam carries the...
iris diaphragm
A mechanical device designed to smoothly vary the effective diameter of a lens, thereby controlling the amount of light...
optical coherence tomography imaging system
Optical coherence tomography (OCT) is an imaging technique used in medical diagnostics and biomedical research to obtain...
nanophotonics
Nanophotonics is a branch of science and technology that explores the behavior of light on the nanometer scale, typically at...
convexo-concave lens
 snooperscope
An instrument used for viewing in low levels of illumination by means of infrared radiation. A high-aperture lens forms an...
fiber optic scanner
A scanner in which a fiber optic assembly replaces a lens system.
pattern
A device that determines the lens shape in the cutting or edging phase of fabrication. It also is used to denote the...
contour projector
An inspection device in which the profile of a mechanical part is projected onto a ground-glass screen at a precisely known...
depth of field
The distance, on either side of the object plane focused on, through which satisfactory image definition can be obtained....
vacuum apparatus
Equipment dependent on the effects of a vacuum. The principal applications in optics are in the coating of lenses and...
optical element
An optical part constructed of a single piece of optical material. It is usually a single lens, prism or mirror.
optical design and engineering services
Optical design and engineering services involve the development, customization, and optimization of optical systems and...
biconcave lens
A lens having each of its outer faces curved inward.
image transducer
Any arrangement of a bundle of optical fibers that alters the shape of the image. For example, by systematic regulation of...
marginal error
The distortion in an ophthalmic lens resulting from the refraction of light rays entering the periphery of the lens surface....
periscope
An optical instrument designed to displace the line of sight in a vertical direction. For submarines and other military uses...
exit pupil
In a lens or other optical system, the image of the aperture stop as seen from image space.
crystalline lens
The internal lens of the eye. It is semielastic to permit changes in its power when focusing on objects at near distances.
antireflection coating
An antireflection coating (AR coating) is a thin film or coating applied to optical surfaces, such as lenses or windows, to...
Mangin mirror
A double-surfaced catadioptric spherical mirror whose spherical first surface consists of a negative meniscus (concave) lens...
modulated zone plate
A zone plate produced by a computer and having a binary structure that can be etched into a chromium or quartz layer. It...
laser diode module
A laser diode module is a compact device that incorporates a laser diode, optics, and often other components into a single...
polishing
The optical process, following grinding, that puts a highly finished, smooth and apparently amorphous surface on a lens or a...
optical bench
A support for optical parts comprising a solid bed that permits precise longitudinal movement of one component relative to...
catoptric system
An optical system in which the only image-forming elements are curved-surface mirrors; e.g., a Cassegrain lens system.
curvature
The measure of departure from a flat surface, as applied to lenses; the reciprocal of radius. Applies to any surface,...
Dogmar/Aviar lens
A general-purpose lens, also known as the Celor lens, used widely in photography and commercial processing; it has the form...
diverging lens
A diverging lens is a type of lens that causes parallel rays of light to spread out or diverge. It is thinner in the center...
lenticular
An array or mosaic of optical surfaces. May be a number of lenses closely packed to form multiple images or many parallel...
Ross lens
A corrective lens system that is placed near the focal plane of a Newtonian telescope to increase its effective field of...
eye lens
The lens of an eyepiece nearest the observer's eye.
axial color
A lens aberration that causes axial light rays having different wavelengths to focus at various points along the axis.
divergent-meniscus lens
A lens with one surface convex and the other concave, the latter having the greater curvature. It also is known as a...
burning glass
A convex lens that brings an incident bundle of rays to a focus to produce intense heat at the focus.
double-Gauss lens
A fast, wide-angle lens used in television and photographic cameras, with excellent overall correction, but subject to...
lens system
Two or more lenses arranged to act in conjunction with one another.
t number
The equivalent f number of a fictitious lens that has a circular opening and 100 percent transmittance, which would give the...
spot filter
A neutral density filter that, when placed in front of the iris of a lens, increases the f-stop range.
apodization
The use of a variable transmission filter at the aperture stop of a lens to modify its diffraction pattern. Reduced...
dispersion
Dispersion refers to the phenomenon where different wavelengths (colors) of light travel at different speeds when passing...
oil-immersion objective
A form of high-power microscope objective where the space between the object and the first element is filled with an oil...
exposure meter
An instrument used to measure the light from a scene to be photographed and to indicate the camera lens and shutter settings...
pseudo-second-derivative
A method used to approximate the values of the homogeneous second derivatives at each iteration in the course of lens design...
box camera
The simplest, most inexpensive type of camera, which is shaped as an oblong or square box, containing the simplest lens,...
second-side toric
The process of grinding the concave surface of a sphero-cylindrical lens.
binocular magnifier
A device having a pair of decentered lenses, one for each eye, that focuses on a single object as a magnifier. It is often...
null lens
A lens used in the optical testing of an aspheric surface. It converts a spherical wavefront into one that precisely matches...
erecting eyepiece
An eyepiece combined with an erecting prism or lens system.
stop down
To reduce the size of a lens aperture, which increases the depth of field.
short-focus lens
 optical center
The point on the optical axis of a lens that is the image of the nodal points. For any bundle of rays passing through the...
lenticular color photography
A type of additive color photography using a lenticular structure impressed on a film base and a camera lens with a filter...
millidiopter
A unit of metric measure equivalent to 1 thousandth (or 10-3 ) of the standard unit of optical power which is the diopter (1...
image optics
Any form of lens, optical system (camera, telescope, microscope, etc.), or opto-electronics utilized for the purpose of...
ultraviolet lens
A lens intended for use with wavelengths shorter than about 380 nm. It must be made of quartz, calcium fluoride, lithium...
generating
A rapid roughing process for the quick removal of glass, the first step in manufacture of a curved lens surface. It is...
zoom lens
An optical system of variable focal length, the focal plane remaining in a fixed position. This result is achieved by moving...
magneto-optic readout device
A device using the Kerr effect to read back the signals from mechanically recorded tapes and discs. It consists of a light...
front-cell focusing
A method of focusing an optical system by moving the front component (the lens closest to the subject) to change the...
Rayleigh interferometer
A device that is used to determine the index of refraction of a gas or liquid through the interference patterns formed by...
infrared lens
An infrared lens is an optical component specifically designed and optimized for transmitting, focusing, or manipulating...
beam shaper
A beam shaper is an optical device or system designed to modify the spatial profile or intensity distribution of a laser or...
focused laser scattering
A single-particle scattering technique in which an incident laser beam is tightly focused by means of lenses to yield a...
hololens
A series of permanent holograms in dichromated gelatin formed by opening total page-composer apertures and setting a point...
measuring wedge
A wedge in a rangefinder or heightfinder used to displace the image produced by one telescope so that it coincides with that...
ring lens
A toric lens generated by rotating a specific cross section about an axis beyond its area and used in the formation of...
petrographic microscope
A microscope equipped with a polarizer, an analyzer and a Bertrand lens to focus on the upper focal plane of the objective....
working aperture
The maximum aperture of a lens at which it will still give a sharp image, even though its physical aperture may be larger.
meta-optics
Meta-optics, also known as metasurface optics or flat optics, is a branch of optics that involves the design, fabrication,...
condenser
A single positive lens or group of lenses used in a projection system to collect light from a source and cause it to...
molded lens
A molded lens is an optical lens manufactured using a molding process, typically involving the shaping of a material, such...
optical axis
The imaginary line passing through both the centers of curvatures of the optical surfaces of a lens or mirror; the optical...
lens mount
The metal tube that maintains the optical components of a lens in proper relationship. Some lenses are mounted in metal...
shadowgraph
A method of demonstration or examination using a point source illumination without the use of any projection lens between...
chalcogenide
Chalcogenide refers to a class of compounds containing elements from group 16 of the periodic table, which includes sulfur...
plasmon ion-assisted deposition
Plasmon ion-assisted deposition (PIAD) is a technique used in thin-film deposition processes, particularly in the production...
optical constructor
A system of modular mechanical components for building precision optical systems. The basic equipment includes a variety of...
decentration
In a single element, any lack of coincidence between the optical and the mechanical axes. In a lens system, any lack of...
infrared photomicrography
Photographic recording that uses infrared radiation as the light source to form an image of a microscopic object and a...
Bertrand lens
A small convergent lens, located between the objective and eyepiece of a microscope, that focuses an image of the upper...
fluorographic lens
A lens having an extremely high aperture and used in the recording of x-ray fluorescent screen images. It often is specially...
stereoscopic distortion
An exaggerated depth appearance in stereo photographs caused by the lenses in the camera being farther apart than the eyes...
Luneburg lens
A dielectric sphere with an index of refraction that varies with distance from the sphere center. A parallel beam of rays is...
metalens
A metalens, short for "metasurface lens," is a type of optical lens that uses nanostructured materials to manipulate light...
working distance
In microscopy, the clear distance between the specimen being viewed and the first optical element of the objective lens.
split-crown triplet lens
A lens derived from the Cooke triplet anastigmat, but with one of the crown elements split in two, resulting in improved...
divergent lens
x-ray image intensifier
An image intensifier that consists of an evacuated tube with a large input phosphor screen at one end. The phosphor screen...
Huygenian eyepiece
An ocular having two planoconvex lenses that are formed from similar glass and that are separated by a space equal to half...
point spread function
The point spread function (PSF) is a fundamental concept in imaging that describes the response of an imaging system to a...
secondary color
An aberration that remains after primary color is corrected. Primary color causes the back focus of a lens to vary with...
diffractive lens
Any optical device that utilizes diffraction in an image-forming capability. Familiar diffractive lenses are zone plates,...
cell
1. A single unit in a device for changing radiant energy to electrical energy or for controlling current flow in a circuit....
rouge
A very fine powdered ferric oxide used in polishing lenses.
Erfle eyepiece
A telescopic eyepiece comprising five or six simple lenses in the form of three doublets or two doublets and a singlet.
reflecting objective
An image-forming system that uses mirrors rather than lenses. Such objectives are frequently used for astronomical...
borescope
A device for the internal inspection of hard-to-get-at mechanical parts, such as rifle barrels, sewer pipes, oil wells, or...
focal length
The focal length of a lens is the distance between the lens's optical center (or principal point) and the image sensor or...
impurity level
In the context of optical materials, the term "impurity level" refers to the presence of foreign atoms or molecules within...
aspheric lens system
An optical system having one or more lens or mirror components that have nonspherical surfaces. These surfaces, whether...
monolithic lenslet module
An array of refractive microlenses that are round, square and hexagonal and as small as 15 µm. They are used for...
wood lens
A type of radial gradient lens that can focus light even though its surfaces are flat.
incident ray
A ray of light that falls upon or strikes a surface of an object such as a lens. It is said to be incident to the surface.
spinthariscope
A device through which scintillations are observed or counted through a magnifying lens system.
mirror lens
An image-forming system having curved mirrors in place of transparent glass components. Mirror lenses are commonly used for...
conical lens
A lens with a surface that is a cone instead of the usual sphere.
lens speed
Also known as f number, lens speed is commonly represented as the ratio of the focal length to the diameter of the lens....
aperture diaphragm
The second adjustable iris diaphragm in an optical system. In the common microscope condenser system, it usually is located...
standard lens
A lens whose focal length is roughly equal to the diagonal of the negative format of the camera on which it is mounted.
cutting
The process of forming a lens to a given pattern, or of cutting a piece of glass along the line of scratch.
endoscope
An endoscope is a medical device used for visualizing and examining the interior of hollow organs, body cavities, or...
astigmatizer
A cylindrical lens that may be rotated to distort a bundle of light originating at a point source, to form a line image.
solar simulator
A solar simulator is a device used to replicate the spectrum and intensity of sunlight in a controlled environment for...
panoramic distortion
The image distortion produced by a panoramic camera with a swinging lens or a swinging mirror in front of a fixed lens. The...
thick lens
A lens with an axial thickness adequate to make it producible.
supplementary lens
A meniscus that is often fitted before a camera lens to permit focusing on near objects.
centering
1. Mounting a lens or mirror so that its optical axis is coincident with the optical or mechanical axes of other portions of...
cutting center
The point on a cutting line that will become the geometrical center of the cut lens.
spherical microintegrated lens
A tiny lens (as small as 100 µm in diameter) used to focus light on charge-coupled devices, formed by heating a...
integrated optics
A thin-film device containing miniature optical components connected via optical waveguides on a transparent dielectric...
extreme ultraviolet
Extreme ultraviolet (EUV) refers to a specific range of electromagnetic radiation in the ultraviolet part of the spectrum....
Topogon lens
A symmetrical, very wide-angle lens. Well-corrected for spherical aberration and color, the Topogon can cover fields up to...
Fresnel lens
A Fresnel lens is a type of optical lens that consists of a series of concentric grooves or steps carved into a flat, thin...
decentering
1. The grinding or edging of a lens so that the geometrical center and optical center do not coincide. 2. The shifting of an...
otoscope
An otoscope is a medical device used by healthcare professionals, particularly ear, nose, and throat (ENT) specialists,...
concave
Concave is an adjective used to describe a surface or shape that curves inward or has a hollow or recessed appearance. In...
test glass
A transparent block shaped accurately to reverse curvatures of the components it is used to test. By contacting an...
catadioptric imaging system
A system that uses both reflection and refraction to achieve its focal power. While the relative powers of the lenses and...
Maksutov objective
A catadioptric lens assembly consisting of a Maksutov corrector and a spherical primary mirror.
Celor lens
 diopter
A unit of optical measurement that expresses the refractive power of a lens or prism. In a lens or lens system, it is the...
emmetropia
The normal condition of vision where an object at infinity is in sharp focus with the eye lens in a neutral or relaxed state.
printer
A photographic enlarger with a fixed negative plane and a fixed paper plane, often using a roll of paper that is advanced...
lens disc
A rotating disc that holds several lenses of differing focal length about a diameter. Used to switch lenses in a system...
effective f number
For a lens with an obscured or noncircular aperture, the focal length divided by the effective aperture.
object working distance
Distance between the front vertex of a lens and the object.
xenon arc photocoagulator
An instrument for eye surgery that directs intense xenon arc light through the transparent cornea lens to the retina where...
converging lens
Also known as convergent lens or convex lens. A lens that converges an incident bundle of rays to a focus.
camera shutter
An apparatus, designed for use with a camera, that is used to rapidly open the path from lens to film, to maintain the...
centered lens system
A lens system in which the centers of curvature of all surfaces fall on a common axis.
focal point
That point on the optical axis of a lens, to which an incident bundle of parallel light rays will converge.
chuck mark
The mark formed when the movement of the lens over the face of the centering chuck abrades the surface.
polycarbonate
A tough, durable, heat- and cold-resistant optical quality plastic used in injection-molded items such as streetlight...
relative aperture
The ratio of the diameter of the entrance pupil in an optical system to the equivalent focal length of that system. The...
optical design software
Optical design software refers to specialized computer programs used by optical engineers, physicists, and designers to...
radius tool
A metal device of convex or concave curvature to which lens castings or semifinished lenses are cemented with only their...
optical head
In compact disc and CD-ROM technology, the portion of the drive that projects the laser light onto the surface of the media...
countersink
The concave portion of a surface, formed on a blank, on which the disk of higher refractive glass will be fused to form a...
microfilm equipment
Two essential pieces of equipment used in connection with the microfilming process: a camera capable of producing, on film,...
telephotography
1. A method of photographing distant objects with a lens of long focal length. 2. The reproduction of photographs over a...
rapid rectilinear lens
A double meniscus system in which two achromatized meniscus lenses are arranged symmetrically on either side of the aperture...
optical Fourier transform
The optical Fourier transform is a mathematical operation applied to optical signals that involves transforming a spatial...
fused quartz and silica
Fused quartz and silica are closely related materials, both composed primarily of silicon dioxide (SiO2), but they are...
inset
The horizontal distance between the 90° meridian of a bifocal lens and the geometrical center of the segment.
conjugate points
The two points on the principal axis of a mirror or lens so positioned that light emitted from either point will be focused...
Seidel aberrations
Seidel aberrations refer to a set of monochromatic aberrations in optical systems, named after the German mathematician and...
diffusing filter
A filter purposely made to be placed before a lens to render the image rather unclear.
parfocal lenses
Lenses that have identical flange focal distances and can be interchanged.
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....
pinhole camera
A lensless photographic camera that uses a small sharp-edged hole as its aperture. The light passed by this aperture onto...
optical table
An optical table, also known as an optical bench or an optical breadboard, is a specialized platform used in optics...
wide-angle distortion
A common aberration in lenses covering large fields of view; it results in images of objects near the edge of the field...
lens bench
aperture stop
A physical constraint, often a lens retainer, that limits the diameter of the axial light bundle allowed to pass through a...
mount
See gimbal mount; kinematic mount; lens mount.
process lens
A lens that is symmetrical and designed to work between 1:1 and about 4:1. It covers a field of about ±20° at f/8...
triple aplanat
A compound lens consisting of two negative lenses of flint glass. A double-convex lens of crown glass is cemented between...
entrance pupil
In a lens or other optical system, the image of the aperture stop as seen from object space.
Rayleigh range
In the region of a Gaussian beam focus by a diffraction-limited lens, it is the axial distance from the point of minimum...
bitoric lens
A lens, both surfaces of which are ground and polished into a toric or cylindrical form.
double-meniscus lens
See periscopic lens; rapid rectilinear lens.
cleaning equipment
In optics, degreasers or ultrasonic arrangements used for removing pitch, cement or polishing material from lenses during...
diffraction-limited lens
A lens with aberrations corrected to the point that residual wavefront errors are substantially less than one-quarter the...
hyperopia
A vision defect commonly referred to as farsightedness. Results when the image of a distant object is focused beyond the...
photographic field
The maximum angle of view that can be recorded by a camera. Field is a function of lens focal length and film format.
stereo camera
A camera with two taking lenses and synchronized shutters. Two images are recorded simultaneously on separate frames,...
vertometer
A device that measures the back focal length or vertex power of a lens.
electron lens
An electric field produced to influence an electron stream much in the same manner that a lens affects a light beam.
electron-beam film scanning
The method by which photographic film is scanned by an electron beam. One technique uses the uniform light of a television...
YAG crystal
A YAG crystal refers to a solid-state crystal made of yttrium aluminum garnet (YAG), which is a synthetic crystalline...
image quality
A measure of the closeness with which an optical image is capable of resembling the original object. The factors that affect...
achromatic lens
A lens consisting of two or more elements, usually of crown and flint glass, that has been corrected for chromatic...
grinding and polishing machinery
Machinery used to grind and finish a component, such as a lens or prism, to a desired precision. Usually such machines carry...
trial sets (ophthalmic)
Sets of lenses (positive, negative and cylindrical) usually mounted in circular rims suitable for slipping into trial...
inverted telephoto lens
optical cements and adhesive
Optical cements and adhesives are specialized materials used in the assembly and bonding of optical components in optical...
plano surface
A lens or mirror surface that is perfectly flat.
cementing surface
The surface of an element of a compound lens that will produce the cemented interface. The curves of this interface are...
gravitational lens
The effect of a powerful gravitational field on light traveling through the field. This effect is detectable in astronomical...
convergence
1. In optics, the bending of light rays toward each other, as by a convex or positive lens. 2. Turning in the eyes to view a...
negative-refraction metamaterial
An artificial material, engineered to have a negative refractive index value, such that light or any other form of...
semifinished
A term used to describe a spectacle lens or blank with one surface totally finished.
film plane
The site behind the lens system in a camera where photographic media are positioned for exposure.
spheric lens
A spheric lens, also known as a spherical lens, is a type of optical lens with at least one surface that is part of a...
Billet's split lens
An experimental lens used to produce interference fringes. A positive lens is cut into halves along its center, and the...
uncut
A term describing lenses with both surfaces finished but not yet cut to any form.
ophthalmology
Ophthalmology is a branch of medicine that focuses on the anatomy, physiology, and diseases of the eyes and visual system....
narcissus
A defect in infrared systems that appears as a dark circular area on a displayed image, caused by radiation reflecting into...
electron filter lens
An electrostatic device that uses an electric potential barrier to allow the transmittance of electrons at or above a set...
lensless microscopy
Lensless microscopy, also known as computational or holographic microscopy, is an imaging technique that captures and...
curvature of field
A lens aberration that causes a flat object surface to be imaged onto a curved surface rather than a plane.
laser optics
Laser optics refers to a broad category of optical components and systems designed for manipulating and controlling laser...
retroreflecting multipass cell
Two lenses, separated by a distance equal to the sum of their focal lengths, and retroreflecting mirror assemblies, one of...
variable-focus lens
A lens assembly containing several movable elements to permit changing of the effective focal length (EFL). Unlike a zoom...
split lens
A close-up lens, semicircular in shape, that is mounted in front of a conventional lens focused at infinity. The result is...
chuck
In the optical field, a tube to which a lens is fastened for centering.
cylinder axis
In a cylindrical lens, the meridian parallel to the generating lines of the cylindrical surface. In a toric lens, the...
thin lens
A concept used for purposes of preliminary calculations and analysis. In theory it is a lens whose axial thickness is zero.
spot diagram
A method of evaluating image quality whereby a large number of rays are traced through a lens from a single object point,...
Sturm interval
The distance between two focal lines in an astigmatic image produced by a lens or mirror.
machine vision lens
A machine vision lens is a specialized optical lens designed for use in machine vision systems, which are used for automated...
variable-focus condenser
An Abbe condenser in which the upper lens element is fixed. The lower lens may focus the illumination between the elements...
lens watch
A dial depth gauge graduated in diopters; a lens measure.
erecting system
Lenses or prisms that serve to erect the image; i.e., to bring the image upright after it has been inverted by the objective.
gradient-index profile
The term gradient-index profile refers to a specific type of refractive index distribution within an optical material. In...
coma
A lens aberration, resulting from different magnifications in the various lens zones, that occurs in that part of the image...
entrance slit
The entrance slit, also known simply as the slit, is an essential component in optical instruments such as spectrometers and...
lensless Fourier transform hologram
A hologram formed without lenses and with the object and reference points sharing the same plane. In the initial recording,...
plane grating
A transmission or reflecting grating with a flat or plane surface requiring a lens or concave mirror to focus the spectrum.
optics
Optics is the branch of physics that studies the behavior and properties of light, including its interactions with matter...
microlens array
A microlens array is a grid-like structure composed of numerous small lenses, typically arranged in a regular pattern. Each...
trinoscope
A color-television viewing system with three kinescopes, three lenses and three deflection yokes used to form the red, green...
toric lens
A lens having one or more toric surfaces. A toric surface is one having a maximum power in one meridian and a minimum power...
inner focusing
In a camera, the movement of one or more lenses behind the front lens, rather than of the front lens itself, to bring the...
metamaterial
Metamaterials are artificial materials engineered to have properties not found in naturally occurring substances. These...
convex
Convex is an adjective used to describe a surface or shape that curves outward, bulges, or has a rounded and outwardly...
phase contrast microscopy
Phase contrast microscopy is an optical microscopy technique that enhances the contrast of transparent and colorless...
Maksutov corrector
A thick meniscus lens arranged concentric with the center of curvature of a spherical mirror to produce an image free of...
front operating aperture
The restricting aperture located at the front of the lens. It is usually defined as the maximum diameter of the entrance...
moving aperture technique
Method for reducing laser speckle in which the object field comes from a real diffuse object or the reconstructed object...
image jump
In optics, the term image jump refers to a displacement or shift in the apparent position of an image when a change occurs...
macro lens
A camera lens, used in macrophotography, that is designed and corrected to produce optimum definition of a nearby object...
internal surface
A nonoptical surface, within lenses and lens mounts, that contributes largely to flare by reflecting light into the image...
thin-film coating
Thin-film coatings are layers of material applied to the surface of an object or substrate, typically to modify its optical,...
telescope lens
A telescope lens is a primary optical component of a telescope system that gathers and focuses light to form an image. It is...
diamond-turned optic
Diamond turning refers to a precision machining process used to produce complex optical components, particularly lenses and...
concavo-convex lens
A lens with one concave surface and one convex surface; synonymous with meniscus.
ocular accommodation
The physical adaption of the eye lens, by means of ciliary muscle contraction, in order to maintain a clear, in focus image...
nodal testing
The measurement of first- and higher order properties of a lens and its formed image, including effective focal length, back...
autofocus system
A means of adjusting the sharpness of an image automatically, with a sensor for estimating distance or contrast and a drive...
major
A blank to which a piece of glass of a different refractive index will be fused to form a multifocal lens.
plastic lens
A lens made from transparent plastic material. Lenses over 31/2 in. in diameter are usually machined, ground and polished....
image working distance
The distance between the last vertex of a lens and the image.
quadratic phase terms
Conceptual formulas that characterize both the transmittance functions of lenses and propagation in the Fresnel zone.
quasi-Fourier transform
The transform defining that, if a reference beam is a divergent spherical wavefront, then the reconstructed image will be...
diffusing screen
In printing, a translucent screen used with lenses to provide an even distribution of diffused light.
pupil
1. In the eye, the opening in the iris that permits light to pass and be focused on the retina. 2. In a lens, the image of...
telescope
An afocal optical device made up of lenses or mirrors, usually with a magnification greater than unity, that renders distant...
metallographic polishing machine
A small optical polishing machine intended for polishing the surface of a metal specimen before etching for examination...
image plane
A plane in which an image is formed. A real image formed by a positive lens would be visible upon a screen located in this...
bifocal lens
A two-part lens that has a different focal length for each part. Generally, it is used in eyeglasses to correct for both...
electrostatic lens
The electrical distribution that serves to influence an electron beam in the same way that an optical lens affects a light...
Barlow lens
A negative lens used to increase the effective focal length of a telescope objective.
telephoto lens
A compound lens so constructed that its overall length is equal to or less than its effective focal length.
lens barrel
The mechanical structure that holds a number of individual lens elements.
Gaussian optics
1. That branch of optics that illustrates the theory in which q is substituted for sin q in Snell's law. Effective results...
anastigmat
A compound lens combination whose astigmatic difference is zero for one or more off-axis zones in the image plane. In such a...
microscopy
Microscopy is a scientific technique that involves the use of microscopes to observe and study objects that are too small to...
multiple lens camera
A camera that uses a rotating mirror to project sequential images onto lenses that are arranged in an arc. The reflected...
immersion liquid
Term synonymous with refractive index liquid, but related more to tank or chamber immersion of crystals, fibers, lenses,...
ultraviolet lens
A microscope used either to detect selective absorption of various wavelengths by the specimen or to achieve increased...
Prentice's rule
A method of determining prism power at any point on a lens. Prism power equals the product of the dioptric power and the...
barium fluoride
A relatively hard crystal, highly resistant to excessive energy radiation, that is frequently used for optical windows,...
rear operating aperture
The restricting opening at the rear of a lens or prism that is commonly defined as the maximum diameter of the emergent cone...
photoelectric scanner
A system mounted a few inches above a moving plane that consists of a light source, lenses and one or more phototubes. In...
intermediate image
In an optical system with a series of lenses, images formed prior to the final focal plane.
lens blank
A lens blank is a piece of optical material in a raw, unfinished state, typically in the form of a disk or block, from which...
Cooke triplet lens
The simplest lens in which all primary aberrations may be corrected. It consists of two positive crown elements on either...
hand viewer
A device small enough to be held in a hand that uses a magnifying lens and a translucent back to permit the viewing of...
Shack-Hartmann wavefront sensor
The Shack-Hartmann wavefront sensor is an optical device used for measuring the wavefront aberrations of an optical system....
bias frame
A frame taken with a CCD camera over an exposure length of zero seconds with the lens cap on or the shutter closed and no...
revolving lens fiber optic scanner
A sequential scanning device, utilizing a revolving lens, in which the cathode-ray tube image is transformed into a circle...
magnifier
A lens or lens system that produces an enlarged virtual image of an object placed near its front focal point.
linear receive optics
Linear receive optics typically refers to the optical components and systems used in the reception (detection) of linearly...
Murty interferometer
A form of shearing interferometer that contains a simple wedged (plane-parallel) glass plate with a nonzero optical path...
line of sight
The line of vision; the optical axis of a telescope or other observation system. The straight line connecting the object and...
linear optics
Linear optics refers to the study and manipulation of light in a linear and deterministic manner, where the response of...
electron optics
The control of free electron movement through the use of electrical or magnetic fields, and use of this electron movement in...
brightfield
Brightfield refers to a type of microscopy and imaging technique in which the specimen is illuminated with a white light...
compound shutter
A center-opening shutter made up of several identical leaves that are mounted symmetrically around the optical axis of the...
point light source
1. With respect to angular subtense, a source of light, such as a star, that is very small. In a lab, a point source may be...
aperture ratio
The ratio of the lens aperture to its focal length (1/f/#).
modulation
In general, changes in one oscillation signal caused by another, such as amplitude or frequency modulation in radio which...
absorption lens
An optical lens manufactured to control the transmission of light over a specified wavelength range. Low absorption lenses...
planoconcave lens
A lens with one plane surface and one concave surface.
area concentration
The ratio of aperture area over receiving area for a specific lens. Also called geometric concentration.
perspective distortion
The distortion that is the result of viewing a print from a point other than the center of perspective. The center of...
spectrograph
An optical instrument for forming the spectrum of a light source and recording it on a film. The dispersing medium may be a...
fiber optic field flattener
A plate consisting of fused optical fibers with both surfaces ground and polished, and having the entrance surface curved to...
Lummer-Gehrcke plate
A high-resolution spectroscopic device commonly used in the early 20th century as a component of double-beam...
pinhole eyepiece
A type of eyepiece, or the modification of an eyepiece, in which a small hole, without a lens, functions as the eye lens;...
MTF optimization
Computerized lens design algorithm that permits the lens MTF characteristic to be included and controlled during the...
pincushion distortion
An aberration of a lens system caused by an increase in lens focal length as the field angle increases. The amount of...
panoramic lens
A lens system that is capable of producing a 360° image, or one that is very close to that. In recording, the image may...
slide projection lens
A lens designed for projection of color transparencies.
lateral color
Lens aberration resulting in image size variation as a function of wavelength. See also chromatic aberration.
digital camera
A digital camera is a device that captures and records still images or video in digital format. Unlike traditional film...
telescope exit pupil
The image of the aperture stop, usually the objective lens, that is produced by the eye lens. When the exit pupil of the...
picking
The process whereby pitch is broken and the lenses or blanks are removed from the block.
collimator
An optical instrument consisting of a well- corrected objective lens or mirror with a light source and or object/image (i.e....
thermal lensing
Distortion of an optical component as a result of heat, which can influence the divergence and the mode quality of a beam...
slab-off
The process of making an abrupt break in a spherical surface on a spectacle lens so that a new center of curvature is set...
Abbe condenser
A two-lens arrangement intended to image light into a microscope slide sample. The primary aberrations present are red and...
star testing
The visual examination by a trained observer of the image of a point source. Any coloring or departure from the Airy disc...
stereoscope
A small instrument containing a picture support and a pair of magnifying lenses so arranged that the left eye sees only the...
blur circle
A blur circle refers to the out-of-focus region in an image captured by an optical system. When an object in a scene is not...
lap
A metal tool used to grind lenses with loose abrasive (see diamond cutting tool). The functional surface of the lap is...
dialytic telescope
A telescope that corrects dispersion and spherical aberration through the use of one or more lenses, usually smaller than...
proximal scanning
Technique using a fiber optic assembly to illuminate an opaque object and transmit an image back from it without a lens...
spherical aberration
Spherical aberration is an optical aberration that occurs when light rays passing through a lens or curved optical surface...
segment height
In a bifocal spectacle lens, the vertical measurement of distance from the uppermost borderline of the bifocal segment to...

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