Definitions: H

A filter that allows heat radiation from an incident beam to pass without absorption or reflection.

A guided missile that uses an infrared sensor to detect and home in on an enemy target. The missile is guided by the high infrared emissions produced by a target, such as the heat from an aircraft or...

A condition in which the solid inclusions within a glass blank are very numerous, such as 25 or more to the square inch.

In the SI system, prefix meaning one hundred, 102.

A gas lamp used in the early 1900s as a physical standard for measurement of luminous intensity. The Hefner unit was superseded by the candle and then by the candela.

A display that allows the observation and measurement of the altitude and range of airborne objects.

A rangefinder used to determine the height or altitude of aerial targets by means of optical triangulation. The device employs the stereoscopic principle.

A method used in facsimile scanning that sweeps the elemental area across the copy in a spiral motion as the result of the movement of a single turn helix against a stationary bar.

An instrument designed to record the duration and intensity of solar radiation.

A device having a plane mirror so mounted that it can be set to reflect sunlight into a piece of laboratory equipment. It is driven by a clock to compensate for the sun's daily motion around the pole...

A small mass spectrometer used to find leaks in a vacuum system by detecting the presence of helium. Using a magnetic deflection device that is permanently tuned to helium, it is capable of detecting...

A helium-neon (HeNe) laser is a type of gas laser that emits visible red light at a wavelength of 632.8 nm. It operates based on the principle of stimulated emission of photons from excited helium...

A compact optical projection system, mounted on or built into a helmet, and used to project data or a scene directly into the eyes of the wearer. Also called visually coupled display.

The capability of the spatial distributions of incident and reflected flux to interchange completely without alteration of the measured reflectance.

A photoanalytical instrument for analysis of jaundice conditions in infants that measures bilirubin (a breakdown product of hemoglobin that produces jaundice), albumen-carrying capacity and binding...

A material used in photodynamic therapy that is retained selectively by tumor tissue when injected into the body; it then fluoresces when exposed to blue light and necroses when exposed to red laser...

Laser cavity bounded by a plane mirror and a concave spherical mirror with the plane mirror located at the center of curvature of the concave mirror.

The inductance of a closed circuit in which an electromotive force of one volt is produced when the electric current in the circuit is varied uniformly at a rate of one ampere per second.

The total fusion and sealing of materials, or usually an enclosure, to ensure that they are airtight.

Laboratory experiments that focus on demonstrating new capabilities of a certain technology or device, usually without consideration of industrial or commercial practicality.

The decrease in effect in developable density on a photographic plate formed by a second exposure to radiation having a longer wavelength, usually red or infrared.

The ionization and spark emission due to exposure to ultraviolet radiation.

A unit of frequency equivalent to one cycle per second.

The radio waves of the electromagnetic spectrum that have frequencies of up to 10,000 megacycles per second.

Radiation consisting of more than a single wavelength in the visible region of the spectrum.

Light measurement by comparison of the luminances of unlike chromaticities.

The interaction between two oscillations of unlike frequencies that forms other oscillations, specifically those with a frequency equal to the frequency difference of the former oscillations.

A type of receiver that uses a local oscillator at a frequency deliberately offset from that of the incoming signal. It is less sensitive than a homodyne receiver, but easier to build because it...

In optical communications, the translation of optical signals into radio signals, lowering their frequency in detection from greater than 1014 Hz to less than 1010 Hz, so that further signal...

Property of a substance whose volume elements differ in composition and optical properties.

A junction between semiconductors that differ in their doping level conductivities, and also in their atomic or alloy composition.

The combination of more than one type of small-molecule monomer into a polymer.

A method used in integrated optics; formed by growing an epitaxial layer of active material, removing it from its base and splicing it onto a passive substrate.

In plano work, that property of a surface determining that it is convex and contacts a flat test glass at its center.

A term used to describe a photograph, film or television picture where the values for black and white areas are at or near their limits, thereby giving the maximum degree of difference between them.

High dynamic range (HDR) refers to a technology that allows for a broader and more dynamic range of luminosity in visual content, such as images or videos. It is particularly associated with displays...

High harmonic generation (HHG) refers to a nonlinear optical process in which intense laser light interacts with a gaseous medium, typically an atom or a molecule, to produce harmonics of the...

Also known as HCS, an analytical method designed to collect statistically relevant amounts of quantitative data on many parallel cell populations or processes within cells through the combination of...

Extensive data storage in the form of bits, with the use of high-resolution photographic materials and optics, and generally a laser.

Distortion of the high frequencies of a signal. In television, the term generally applies to frequencies above the 15.7 kHz line frequency.

A screen with a reflected or transmitted light beam that is confined to a much smaller bundle than was received by the screen, thereby resulting in a higher luminance.

A superthin, highly reflective mirror.

Optical fiber in which the attenuation exceeds the normally acceptable level for long-haul or data communications use.

A filter possessing one transmission band that extends from a cutoff frequency other than zero to frequency at infinity.

A very high bandwidth communication line often used in fiber optics.

A cloud chamber designed to maintain the gas within it at a high pressure as a means of reducing the range of the high-energy particles and, subsequently, increasing the chances of observing...

A satellite-borne remote sensing device capable of transmitting images at 10 and 20 m resolution from an altitude of 830 km, each sensor covering a ground area of 60 km, by means of a folded...

The holographic recording of sequences of high-speed phenomena. With a multiple beam laser, multiple holograms that depict rapid events can be formed on a single medium.