Definitions

A mechanical device designed to smoothly vary the effective diameter of a lens, thereby controlling the amount of light allowed through.

The adjustable membrane located just in front of the crystalline lens within the eye. The iris gives the eye its color. See also iris diaphragm.

Radiant flux incident per unit area of a surface. Also called radiant flux density.

A thermosetting material used in the jacket of fiber optic cables.

Application of radiation to an object.

One of a number of nuclides characterized by an identity between their mass numbers, but each having a different atomic number.

Indication of emission brightness with degree of emission from an optical source.

Having the same chromaticity or color.

1. Lines of the same color. 2. A term used in photoelastic stress analysis to refer to the interference fringes produced in birefringent materials.

The points on a photographic negative that are of equal density.

A graphic depiction of the loci of all points in space relative to a laser transmitter at a specific altitude.

With respect to the effect of crystals on lightwaves, the family of curves having constant direction of polarization.

In the context of electronics and optics, an isolator refers to a device that allows the transmission of signals in one direction while attenuating or blocking signals in the opposite direction. The...

An enclosure for a calorimeter that allows measurement of unusually low quantities of power and energy.

A curve or surface having equivalent light intensity.

A direct recording photometer that is designed to scan a photographic negative to determine its points of isodensity.

Free of coma.

Graphic representation of quantified values of image quality whose points all refer to images that are of a constant subjective quality.

Lines of equal atmospheric attenuation in a laser beam.

The slight difference in wavelength of an element's given spectral line observed in comparing different isotopes of that element.

A spectroscopic technique in which an excitation band absorbs laser energy resulting in an electronic transition. The isotopic species may then be measured using a time of flight mass spectrometer....

That property of a material that determines that velocity of propagation within the material is the same for all directions.

The outer material that surrounds and protects the buffered and unbuffered fibers in an optical cable.

The higher throughput obtained with an FTIR device compared with traditional spectrometers that need slits to achieve resolution. The advantage differs according to wave number and resolution.

An instrument designed to measure the index of refraction of a gas by the interference patterns formed by two beams, one of which passes through a vacuum tube in which the gas is slowly released.

Phrase applied to any noise of extraterrestrial origin, named for the engineer who discovered the phenomenon.

A prism produced by severing a Nicol prism and reconstructing the polarization angles of the two halves so that they are slightly wedged toward each other.

A continuous-wave dye laser that uses a circulation pump and nozzle to provide an optically flat stream of dye across the laser's optical axis.

A device to hold and locate a workpiece as it guides, controls or limits a cutting tool.

Also called coating jig allowance. That margin on an optical component that is outside the clear aperture for use in holding the component in the optical thin-film coater tooling during the...

An optical instrument containing a gimballed sighting telescope, used to measure angular relationships in horizontal and vertical planes.

1. In relation to cathode-ray tube displays, errors in the signal's amplitude, phase or both that result in small, rapid aberrations in size or position of the image. 2. Errors of synchronization...

A design for bent crystal monochromators in which spacing is constant along any circular arc terminating at the two foci and with equally spaced Bragg planes curved about only one axis.

The graph of a curve describing the spectral irradiance of extraterrestrial sunlight.

A device consisting of two optical systems in which two signals are simultaneously transformed to produce their spectra, and these spectra are multiplied and inversely transformed to produce the...

Characteristic of radiation detectors that produce energy that is similar to the energy of superconductive gaps when interacting with photons.

A unit of energy or work in the MKS system of units. One joule is equal to 107 ergs.

A detector cooling device in which a gas under high pressure escapes through an expansion valve in the tank; as the escaped gas liquefies, it cools the site of the sensor.

A small defocused Galilean telescope mounted in a hole in a door. Viewed from inside through the positive lens, a wide-angle view of the outside is seen; viewed from outside through the negative...

A semiconductor device with the property of conducting current more easily in one direction than the other. It has two terminals containing a single crystal of semiconducting material that ranges...

A device designed to measure radiant energy, particularly in the thermal region.

The diffraction of a particle by a standing lightwave.

In an interlaced scanning electro-optical system such as television, the system resolution will be less than the number of active scan lines because of the random phase nature of the object being...

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

The SI unit of temperature equal to 1°C. See absolute temperature scale.

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

See color perception test equipment; eye test apparatus.