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8,726 terms

Photonics Dictionary

hecto
In the SI system, prefix meaning one hundred, 102.
Hefner unit lamp
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 The Hefner unit was superseded by the candle and then by the candela.
height-range indicator
A display that allows the observation and measurement of the altitude and range of airborne objects.
heightfinder
A rangefinder used to determine the height or altitude of aerial targets by means of optical triangulation. The device employs the stereoscopic principle.
HEL
high-energy laser
helical scanning
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.
heliograph
An instrument designed to record the duration and intensity of solar radiation.
heliostat
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...
helium leak detector
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...
helium-neon laser
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...
helmet-mounted display
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.
Helmholtz reciprocal relationship
The capability of the spatial distributions of incident and reflected flux to interchange completely without alteration of the measured reflectance.
HEM
hybrid electromagnetic wave; heat exchange method
hematofluorometer
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...
hematoporphyrin derivative
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...
hemispherical cavity
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.
HEMT
high-electron-mobility transistor
henry
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.
HEPA
high-efficiency particulate air
hermetic bonding
The total fusion and sealing of materials, or usually an enclosure, to ensure that they are airtight.
hero experiments
Laboratory experiments that focus on demonstrating new capabilities of a certain technology or device, usually without consideration of industrial or commercial practicality.
Herschel effect
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.
Hertz effect
The ionization and spark emission due to exposure to ultraviolet radiation.
hertz
A unit of frequency equivalent to one cycle per second.
Hertzian waves
The radio waves of the electromagnetic spectrum that have frequencies of up to 10,000 megacycles per second.
heterochromatic light
Radiation consisting of more than a single wavelength in the visible region of the spectrum.
heterochromatic photometry
Light measurement by comparison of the luminances of unlike chromaticities.
heterodyne
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.
heterodyne receiver
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...
heterodyning
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...
heteroexcimer -> exciplex
The term "excimer," strictly used, refers to excited species made by combination of two identical moieties, atoms or molecules. Excited complexes that do not fall into this category are...
heterogeneous
Property of a substance whose volume elements differ in composition and optical properties.
heterojunction
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...
heteropolymerization
The combination of more than one type of small-molecule monomer into a polymer.
heterostructures
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.
HEX
heat exchanger unit
HF
high frequency
HFS
hyperfine structure
HID
high-intensity discharge
Higgs boson
The Higgs boson is a fundamental particle associated with the Higgs field, a field that permeates the universe and is responsible for giving mass to other fundamental particles through the mechanism...
high
In plano work, that property of a surface determining that it is convex and contacts a flat test glass at its center.
high contrast
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
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
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...
high-content screening
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...
high-density storage
Extensive data storage in the form of bits, with the use of high-resolution photographic materials and optics, and generally a laser.
high-excitation potential -> excitation potential
The amount of energy required to raise the energy level of an atom; a necessity if the atom is to radiate energy. High excitation potential is the amount of energy in the upper state of the...
high-frequency distortion
Distortion of the high frequencies of a signal. In television, the term generally applies to frequencies above the 15.7 kHz line frequency.
high-gain screen
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.
high-index-contrast subwavelength grating
A superthin, highly reflective mirror.

Photonics Dictionary

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