Photonics Dictionary: H

A semicircular, half-wave quartz plate between the polarizer and analyzer. It often is used in forming precision settings with a polariscope.

A plate of electro-optical material that serves to rotate the plane of polarization of a light beam.

A test for spherical aberration, coma or astigmatism in which incident rays from a point source are isolated by small holes in a metal disc located close to the lens or mirror under test....

A filter, used in photography, that absorbs the ultraviolet and extreme blue violet radiation scattered by atmospheric haze.

The heat-affected zone (HAZ) refers to the portion of a material, typically metal, that experiences changes in its microstructure and mechanical properties due to the heat generated during welding,...

A glass filter that transmits visible light while absorbing infrared energy (heat).

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

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 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.

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...

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 heterojunction is a junction formed between two different semiconductor materials with differing band gaps. These materials can be of the same or different types (e.g., both n-type, both p-type, or...

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.

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...

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 shutter actuated by means other than mechanical springs for timings on the order of nanoseconds. The shutter is used in the photography of rapid moving objects or events.

The three-dimensional interference pattern of fringes that is recorded on a holographic plate to facilitate the study of a complex object.

The interferometric analysis of a complex object by utilizing the three-dimensional hologram. By causing a laser beam to diverge into two directions, one of which directly strikes a holographic...

A specific type of hologram that will transmit a pure plane wave when the hologram is illuminated by the type of wave it is matched to.

The application of coherent wavefront techniques to the determination of the physical state of a system without appreciably altering that state.

A system of sensors and related instrumentation that allows a navigable object (usually a missile) to locate its destination by some distinguishing characteristics of that target, and then calculate...

An infrared device used in satellites and rockets to determine a heat horizon for the Earth at altitudes (above 200 miles) where the visible horizon cannot be discerned. The device scans the infrared...

In television, the period during which the electron beam is cut off while the raster returns from the right-hand side of the screen to the left.

Horizontal concentrations that comprise the dominant factor in atmospheric gradient correction. The range bias near due north and due south azimuths coincides with the systematic decrease in surface...

The locus of the points in the field of binocular vision that are observed singly. The images of these points correspond to the respective retinal points.

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

A plotted relation between Log E (logarithm to base 10 of exposure in metercandle seconds) and density (logarithm to base 10 of opacity).

Device in which the various circuit elements are fabricated in different substrate materials and then appropriately joined together so that the various substrate materials can be chosen to optimize...

A photoreceptor material used in solar cells and in drums for laser printers and high-speed copiers because of its high quantum efficiency over a wide spectral band, high data-rate capability and...

A type of stereoscopic photography in which the distance between the two view points is greater than the average interpupillary distance. Therefore, the viewed image will appear to be half its size...

This term literally means "to lag behind.'' It is quite often used to describe the residual effect that remains after the primary effect has been removed, or the lag that exists between the...

A halogen lamp, also known as a tungsten halogen, quartz-halogen, or quartz iodine lamp, is an incandescent lamp that uses a tungsten filament surrounded by a small amount of halogen gas, such as...

A holographic camera, also known as a holographic imaging system or holographic recorder, is a specialized device used to capture 3D holographic images of objects or scenes. Unlike conventional...

Any integrated circuit that also makes use of one or more discrete components; frequently used to describe circuits that combine both photonic and electronic components.

Also known as constant angle or constant deviation fringes. The interference fringes observed with dense flat plates near normal incidence. The fringes of the Fabry-Perot interferometer are Haidinger...

Triggering a laser at a predetermined time by pumping it to a level just below its threshold and then using an auxiliary source that quickly pumps it above threshold. Means of achieving it in laser...

1. In a cathode-ray tube, the glow surrounding a bright spot that appears on the fluorescent screen as the result of the screen's light being reflected by the front and rear surfaces of the tube's...

The term half bandwidth (HBW) generally refers to the width of a spectral band or frequency range at half of its maximum amplitude. It is commonly used in the context of signal processing, optics,...