A lamp, usually incandescent, that has a very compact filament, permitting a greater concentration of emitted light, aided by the use of small apertures and appropriate reflectors.

For a lens with an obscured or noncircular aperture, the focal length divided by the effective aperture.

A visual spectrophotometer with a rhomb located directly before the entrance aperture of a constant-deviation...

1. Calculated distance between two exactly opposed points on a beam at a chosen fraction of peak power (typically 1/e2). 2....

A form of high-power microscope objective where the space between the object and the first element is filled with an oil...

The lens located at the object end of a microscope tube. A wide range of objectives is available, including simple...

A high-quality, narrow-angle lens of high aperture designed for low magnification in the recording of cathode-ray tube...

An apparatus, designed for use with a camera, that is used to rapidly open the path from lens to film, to maintain the...

The term that represents the size of one of the many small elements into which a television image is necessarily broken down...

The image of the aperture stop, usually the objective lens, that is produced by the eye lens. When the exit pupil of the...

1. That portion of the aperture that functions to collect energy and deliver it to the final system detector. 2. For an...

1. That branch of optics that illustrates the theory in which q is substituted for sin q in Snell's law. Effective results...

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...

The numerical aperture of an optical system used to couple (launch) power into an optical waveguide.

A device for measuring linear dimensions. The optical caliper generally consists of two circularly mounted mirrors whose...

A condenser that forms a hollow cone-shaped beam of light with its focal point in the plane of the specimen. If it is used...

A lensless photographic camera that uses a small sharp-edged hole as its aperture. The light passed by this aperture onto...

A device that measures the spatial distribution of energy perpendicular to the propagation path of a radiant beam. An energy...

A source that attempts to create the characteristics of an ideal blackbody. It consists of a cavity, generally spherical,...

That object distance at which a camera must be focused so that the far depth of field just extends to infinity. The near...

A support for optical parts comprising a solid bed that permits precise longitudinal movement of one component relative to...

An aperture consisting of a semitransparent central region whose amplitude transmittance only is varied, and the relative...

The propagation or hindrance of waves reaching each aperture of the interferometer because of atmospheric turbulence.

A lens that exhibits spherical aberration when used at large aperture settings, and that forms an image with a slightly...

A positive lens located at or close to an intermediate image plane. The collector refracts off-axis light bundles, directing...

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

In optics and photolithography, a phase mask refers to a device that modifies the phase of light waves passing through it....

A spectrograph in which the flux density transmitted through the entrance aperture is regulated by an optical wedge or...

A defect in an optical system that prevents rays from reaching their intended destination; it can be caused by an undersized...

The smallest linear diameter to which a laser or other beam of radiant energy is capable of being focused, depending on the...

Characteristic of optical analyses that are limited to infinitesimally small apertures. Also called first-order or Gaussian...

To reduce the size of a lens aperture, which increases the depth of field.

Scalar diffraction theory is a simplified approach used to describe the propagation of electromagnetic waves, particularly...

1. Also known as near-field diffraction. The field of radiation sent through an aperture in an absorbing screen at large...

An interferometric method for describing the surface shape of large coated or uncoated optical flats. The procedure uses a...

A series of permanent holograms in dichromated gelatin formed by opening total page-composer apertures and setting a point...

Wide-field fluorescence microscopy uses either naturally occurring structures or staining with fluorescent tags that are...

An instrument used for viewing in low levels of illumination by means of infrared radiation. A high-aperture lens forms an...

A two-stage illuminating system for a microscope in which the source is imaged in the aperture of the substage condenser by...

An interferometer that functions by first detecting the light striking each aperture and then combining the two detector...

A camera with a very high aperture lens or mirror system for photographing x-ray fluorescent screen images, mainly to save...

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...

A small opening or slit in a mask.

In a lens, the square of the radius of its aperture divided by the product of the focal length and the wavelength. It...

The formation of a fan of light or energy rays in a beam as the beam passes through an extremely narrow aperture.

An electron tube that is used as a camera tube for a television system. When the picture to be transmitted is focused on a...

The second adjustable iris diaphragm in an optical system. In the common microscope condenser system, it usually is located...

The law stating that the brightness of an object that is examined through a slotted disc, rotating over a critical...

A camera that consists of a concave spherical mirror with an aspheric plate situated at the center of curvature of the...

The series of interference bands that appear in the spectrum when a specified glass plate is inserted into a spectroscope,...

A microscope design that involves apertures inserted in conjugate plane positions inside the microscope, with one aperture...

Magnification that is above the level of maximum useful magnification and does not contribute useful resolving power. In a...

A photographic objective that uses the thick meniscus principle to obtain its power. It is designed to photograph small...

The liquid used in microscopy to fill the space between the high-power objective lens and the microscope slide in order to...

A loss of resolution or detail in a television signal caused by the size of the electron scanning beam.

The maximum circular area over which radiance and radiant exposure can be averaged.

An instrument designed to measure the numerical aperture of an objective.

A pair of long, slender parallel apertures used in experiments on diffraction and interference.

In a lens system, a group of elements considered as an entity; either a front or rear member depending on whether it is...

A lens system made up of two sets of similar lenses, each of which compensates for many of the aberrations produced by the...

An imaging process in which the single opening of a simple pinhole camera is replaced with many openings called,...

The condition of the numerical aperture or beam diameter of the laser, LED, or other optical source being larger than the...

Two simple meniscus lenses arranged symmetrically on either side of the aperture stop, providing reduced coma, lateral color...

Specified curved optic intended for maximum collection of light, including off-axis rays, before leaving the exit aperture.

The amplitude, polarization and phase contained in the field distribution over the aperture.

Also called coating jig allowance. That margin on an optical component that is outside the clear aperture for use in holding...

A ray of an image-forming bundle that passes through the edge of the entrance pupil or aperture stop. Usually used in...

Also referred to as the axial ray (or a-ray), a marginal ray originates from the axial point of the object and passes...

Spherical or chromatic aberration in a lens having a wide aperture. It is present because the refracting power varies for...

Device used to measure the numerical aperture of a microscope, composed of a 14-mm-thick glass block with numerical aperture...

Also known as a shadow mask, a perforated plate placed between the focusing and accelerating electrodes, and the tricolor...

The use of computer analysis in the calculation of diffraction patterns for information on the design of optical systems. In...

The series of equally spaced parallel slits that make up a scanning aperture in place of a single slit, in the scanning of a...

The photographic filming of the action of x-ray images recorded on a fluorescent screen by means of large lens apertures and...

An astronomical telescope is a type of optical instrument designed to gather and magnify light from distant celestial...

There are three types of telecentric lenses: -Image-space telecentric lenses are those in which the aperture stop is...

A double meniscus system in which two achromatized meniscus lenses are arranged symmetrically on either side of the aperture...

A device for automatic exposure control in which a motor-driven diaphragm adjusts the aperture in response to a signal from...

A Fresnel lens is a type of optical lens that consists of a series of concentric grooves or steps carved into a flat, thin...

A nonmagnetic instrument utilizing an electrofocus and deflection tube with a photocathode for imaging purposes. The optical...

A lens having an extremely high aperture and used in the recording of x-ray fluorescent screen images. It often is specially...

The recording of the information contained in a modulated electron beam onto photographic or silicon resin-coated materials....

The angular spectrum approach is a mathematical and computational technique used in the field of optics to analyze and...

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...

Method for reducing laser speckle in which the object field comes from a real diffuse object or the reconstructed object...

Coded image obtained optically with a nonredundant pinhole array imaging aperture.

In an optical system, the gradual reduction of image illuminance as the off-axis angle increases, resulting from limitations...

The entrance slit, also known simply as the slit, is an essential component in optical instruments such as spectrometers and...

Electromagnetic radiation present upon the open aperture of the source within an operating environment.

The restricting opening at the rear of a lens or prism that is commonly defined as the maximum diameter of the emergent cone...

An inspection device in which the profile of a mechanical part is projected onto a ground-glass screen at a precisely known...

In an optical system, the aperture size at which the lens gives its best overall performance.

The limited light-gathering area of an optical system. The area is normally restricted to an edge or outer surface of an...

The angle between the most divergent rays that can pass through the lens to form an image. In a birefringent crystal light...

The actual width of a bevel rather than its width projected along the lens aperture.

The angular width of a radiation beam. With respect to a conical beam of light, it is the vertex angle of the cone. The...

A laser having a rod that is a stacked array of discs immersed in a transparent flowing coolant fluid. In this way, the...

In a lens or other optical system, the image of the aperture stop as seen from image space.

The sine of the vertex angle of the largest cone of meridional rays that can enter or leave an optical system or element,...

A factor derived by equating the incident light on the subject to the required incident light for suitable photography. The...

The ratio of the diameter of the entrance pupil in an optical system to the equivalent focal length of that system. The...

A shutter in which the opening and closing times for a large aperture setting occupy a substantial fraction of the total...

A small convergent lens, located between the objective and eyepiece of a microscope, that focuses an image of the upper...

Two formulas used in diffractometer analysis, the first giving the individual diffraction patterns of each aperture, the...

Also referred to as the V number in fiber optics; the normalized frequency is a dimensionless quantity, denoted by the...

A flanged or plain ring with a restricted aperture, located in an optical system at any of several points, that cuts off...

An aperture located at an image plane of an optical system that determines the size and shape of the image.

A region far from an aperture or source where the diffraction pattern is essentially the same as that at infinity. Changes...

A combination 80-column computer card containing a 35-mm microfilm frame. Reference data can be punched onto the card to...

A forerunner of the modern camera, this instrument had a focusable lens that produced a sharp image on the enclosure...

The flat or angled surface, usually fine-ground, that limits the aperture of a lens or prism surface.

Imaging radar that increases the sweep of its along-track (or azimuth) capacity by measuring not only the time delay of the...

1. A device generally used in a cathode-ray or camera tube to emit a stream of electrons moving at uniform velocity in a...

An aperture, usually rectangular in shape, with a large length-to-width ratio, and a fixed or adjustable shape through which...

A device that holds a number of filters and allows the filter with the desired characteristics to be rotated into an optical...

A light-tight box that receives light from an object or scene and focuses it to form an image on a light-sensitive material...

An Abbe condenser in which the upper lens element is fixed. The lower lens may focus the illumination between the elements...

An electron-gun system is an assembly used to generate and control a focused beam of electrons. Electron guns find...

The formation of an image by a pinhole aperture that transmits radiation, such as gamma radiation.

The real numerical aperture (NA) of a fiber when the computed NA is not valid because of change in the glass indices during...

The direct cladding used for fused silica cores to create large numerical aperture fibers and used as overcoats to...

The maximum aperture of a lens at which it will still give a sharp image, even though its physical aperture may be larger.

The Shack-Hartmann wavefront sensor is an optical device used for measuring the wavefront aberrations of an optical system....

The metal tube that maintains the optical components of a lens in proper relationship. Some lenses are mounted in metal...

The use of a variable transmission filter at the aperture stop of a lens to modify its diffraction pattern. Reduced...

The area closest to an aperture or source where the diffraction pattern differs substantially from that observed at an...

The restricting aperture located at the front of the lens. It is usually defined as the maximum diameter of the entrance...

In the context of thin film deposition processes such as evaporation or sputtering, masks are used to selectively deposit...

A machine vision lens is a specialized optical lens designed for use in machine vision systems, which are used for automated...

The ratio of the lens aperture to its focal length (1/f/#).

A physical constraint, often a lens retainer, that limits the diameter of the axial light bundle allowed to pass through a...

An opening or hole through which radiation or matter may pass.

An astronomical mirror, also known as a telescope mirror or primary mirror, is a key component of a reflecting telescope. It...

The technique for measuring the index profile of an optical fiber by scanning the entrance face with the vertex of a high...

A high-speed, narrow-field lens consisting of two achromats spaced about the aperture stop. Its uses include portrait...

The ray that passes through the center of the aperture stop in an optical system. It often is called the principal ray of an...

The ratio of aperture area over receiving area for a specific lens. Also called geometric concentration.

In a lens or other optical system, the image of the aperture stop as seen from object space.

Factor that relates the pulse spread occurring in a graded-index fiber to that of an equivalent step-index fiber having an...

1. In optics, the bending of rays away from each other. 2. In lasers, the spreading of a laser beam with increased distance...

An infrared lens is an optical component specifically designed and optimized for transmitting, focusing, or manipulating...

A visual, single-unit spectrophotometer with a biprism and a Wollaston prism. The Wollaston prism polarizes coincident...

An instrument consisting essentially of a tube 160 mm long, with an objective lens at the distant end and an eyepiece at the...

Array used in coded-aperture imaging experiments with two-beam CO2 lasers that provide an artifact-free process, faithful...

A digital camera is a device that captures and records still images or video in digital format. Unlike traditional film...

The process of producing a visible two-dimensional image of a scene that is dependent on differences in thermal or infrared...

An accurately produced hole of any size and shape that is used as a masking device in an optical system. Pinhole apertures...

A zone plate in which the zones are alternately transparent and opaque to specific radiation, and coarse enough so that no...

When a lens system with a circular aperture is free of aberrations, the image of a point object will appear as a disc of...