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ASU Dictionary Terms

densitometer
1. An instrument used to measure the opacity or density of dyes, pigments or dispersed particles that form an image in or on...
fiber optic spectrometer
A fiber optic spectrometer is a device used for measuring the spectral content of light. It utilizes optical fibers to...
polarimeter
A polariscope with a half-shade device and an angular scale generally attached to the analyzer. It is used to measure the...
microreciprocal degree
An approximated measure of the smallest change in color temperature detectable by the human eye, defined as the reciprocal...
Fizeau toothed wheel
A device used to measure the speed of light by adjusting the rotation of a toothed wheel so that light passing through one...
photon correlation spectroscopy
Spectroscopy used to study the concentration, diffusion and Brownian motion of small particles suspended in a fluid by...
flux rise time
Time elapsed during the radiant output change from 10 to 90 percent of maximum in a light-emitting diode or laser. Usually...
metrology
Metrology is the science and practice of measurement. It encompasses the theoretical and practical aspects of measurement,...
sclerometer
An instrument used to test the hardness of various materials. It measures the pressure on a standard point that is necessary...
phototransistor tachometer
A tachometer consisting of a light source, rotating perforated wheel and phototransistor to measure the rates of rotation of...
surface analysis by laser ionization
(SALI) A type of spectroscopy in which neutral atoms or molecules are ionized by an excimer laser beam and then measured by...
crystal spectrometer
A device designed to measure crystal properties by analysis of crystal diffraction.
biprism
A piece of glass polished flat on one side, with a pair of polished faces that form an angle close to 180° on the other...
center thickness
The lens thickness measured at the optical axis.
ephemeris time
Uniform measure of time based on dynamics law and calculated according to planetary orbital paths; specifically, Earth's...
compensator
An optical element that measures the phase difference between two components of elliptically polarized light to correct for...
scattered fringe period
Measure of the interference fringe pattern produced by the forward scattering of light by an optical fiber; the fringe...
data cube
A multidimensional array of values that is commonly used in programming to describe a time series of image data. Each...
Brillouin scattering
Brillouin scattering is a phenomenon in physics where an incident electromagnetic wave (usually light) interacts with...
machine vision lens
A machine vision lens is a specialized optical lens designed for use in machine vision systems, which are used for automated...
dioptometer
A telescopic system having an eyepiece, a reticle and an objective. The instrument measures wavefront power in diopters.
absolute colorimetric
Method of preserving the measured color value and color information as it is translated from differing devices. For example...
custom lapping and polishing services
Custom lapping and polishing services involve specialized processes used to improve the surface finish and dimensional...
radiant intensity
The radiant energy emitted within a time period per unit solid angle, usually measured in watts per steradian.
thickness gauge
A device used to measure the thickness of a given substance.
time-correlated single photon counting
Time-correlated single photon counting (TCSPC) is a technique used in photon counting applications, particularly in the...
interferometer
An instrument that employs the interference of lightwaves to measure the accuracy of optical surfaces; it can measure a...
mirror testing
The observation and measurement of the flatness of a mirror surface by contacting an optical flat with the mirror. The...
integrated photonics
Integrated photonics is a field of study and technology that involves the integration of optical components, such as lasers,...
infrared lens
An infrared lens is an optical component specifically designed and optimized for transmitting, focusing, or manipulating...
attosecond photonics sources
Attosecond photonics sources refer to devices or systems that generate extremely short pulses of light on the order of...
Angstrom compensation pyrheliometer
A system used for measuring direct solar radiation.
isotopically selected laser spectroscopy
A spectroscopic technique in which an excitation band absorbs laser energy resulting in an electronic transition. The...
perceived color
The apparent color, as seen by the human eye, as distinguished from color as a measurable property of light.
local injection detection system
A device used to evaluate the quality of fiber optic splices made in the field by injecting light into the cladding of the...
ellipsometry
Ellipsometry is an optical technique used to characterize the properties of thin films and surfaces. It is based on the...
optical testing instrument
An optical testing instrument is a device or system used to evaluate and measure the performance, quality, and...
pixel pitch
Pixel pitch refers to the distance between the centers of two adjacent pixels on a display screen or imaging sensor. It is...
beam divergence
Increase in the diameter of an initially collimated beam, as measured in milliradians (mrad) at specified points; i.e.,...
microdensitometry
The science that deals with the measurement of optical absorbance (i.e. optical densities) over microscopic areas of a given...
phase constant
With respect to a traveling plane wave at a known frequency, the space rate of decrease of phase of a field component in the...
McLeod gauge
A gauge designed to measure high degrees of vacuum. It consists of a glass bulb attached to the vacuum vessel, the...
pyrheliometer
An instrument for measuring the intensity of solar radiation.
spectroscope
In a general sense, any one of a class of instruments used to disperse radiation, visible or invisible, into its component...
photoelectric photometer
Also known as electronic photometer. A photometer with a photocell, phototransistor or phototube for measuring the intensity...
frequency comb
A frequency comb is a precise and regular series of equally spaced spectral lines, or frequencies, that are generated with...
phase
In optics and photonics, "phase" refers to a property of electromagnetic waves, such as light, that describes the position...
diffuse reflectance spectroscopy
Diffuse reflectance spectroscopy (DRS) is a nondestructive analytical technique used to investigate the optical properties...
azimuth angle
1. In astronomy, the angle measured clockwise (eastward) in a horizontal plane, usually from north (true north, Y-north,...
cathetometer
A type of comparator with a telescope equipped with a cross wire mounted on a vertical sliding column. It is used to measure...
automatic optical inspection
A system for automatic industrial process control or measurement, consisting of an optical module for image acquisition, a...
picosecond continuum
A broadband, visible picosecond probe pulse capable of measuring an entire absorption spectrum in one shot.
Nichols radiometer
An instrument devised by Nichols and Hull for use in the measurement of radiation pressure. The device has two small...
height-range indicator
A display that allows the observation and measurement of the altitude and range of airborne objects.
total image runout
Image displacement by a decentered lens, rotated on a chuck whose axis of rotation passes through the geometrical center of...
optical clock
An optical clock is a highly precise and advanced timekeeping device that relies on the oscillations of electromagnetic...
solar occultation
Measurement of absorption by the gas of interest in the 2- to 6-µm range as a function of tangent height pressure. The...
spectral response
Measure of a detector's signal during exposure to radiation of a constant power level and varying wavelength.
total radiation pyrometer
Also known as a pyrradiometer. An instrument that is designed to measure heat radiation nonselectively; e.g., the...
nitric oxide detector
A pollution-measuring device used to detect the presence of nitric oxide regardless of other gases present. It utilizes the...
optical lever
A device used to detect and measure small amounts of rotation. The rotating object contains a reflecting surface from which...
focal power
In a symmetrical optical system this is a measure of the influence of the system upon the focus of a pencil of rays passing...
q-switched operation
Q-switched operation, or q-switching, is a technique used in lasers to produce short and intense pulses of light. The term...
magnetic rotation spectroscopy
Technique in which the polarization rotation of light, and its relationship to the magnetic field strength can be analyzed...
absolute temperature scale
The measurement of heat energy as determined from absolute zero as the zero point on the scale. Increments are identical to...
optical channel monitor
An optical channel monitor (OCM) is a device used in optical communication systems to monitor and analyze the performance of...
fixed-pattern noise
Fixed-pattern noise is the measure of the static (nontemporal) differences between pixels when the detector is evenly...
alphanumeric reader
An instrument that reads alphabetic, numerical and special characters by means of a photosensor that measures the varying...
lateral load test
A method of measuring microbending losses in optical fiber by sandwiching a length of fiber between two parallel plates,...
silicon photodiode
A silicon photodiode is a semiconductor device that converts light into an electrical current. It is a type of photodetector...
phototheodolite
A camera equipped with angular scales in altitude and azimuth. The scale readings are imprinted on the film when an exposure...
detector-Dewar assembly
A detector-Dewar assembly typically refers to a combination of a detector and a Dewar flask used in scientific instruments,...
immersion refractometer
A type of refractometer designed to measure the refractive indices of liquids. A section of the instrument is immersed into...
electromodulation spectroscopy
A type of modulation spectroscopy that measures spectral reflectance or transmittance changes induced by applying a...
2D profile sensor
A 2D profile sensor is a type of sensor used in various industrial and technological applications to measure and capture...
spectrophotometer
A spectrophotometer is a scientific instrument used to measure the intensity of light at various wavelengths in the...
laser gyroscope
Counter propagating beams imaged along the same path in order to detect rotation. Precise rotation is measured through...
pupilometer
An instrument for measuring the diameter of the human eye pupil.
optical multimeter
An instrument that measures several optical parameters, such as optical power and wavelength, with a single measurement...
gegenschein-zodiacal light photometer
A photometer used to measure sky brightness and polarization associated with zodiacal light, background starlight, F-region...
Murty interferometer
A form of shearing interferometer that contains a simple wedged (plane-parallel) glass plate with a nonzero optical path...
magnetic spectrograph
An electron system using the effect of a constant magnetic field on electron paths to differentiate electrons that have...
vacuum gauge
A gauge designed to measure the degree of vacuum in an evacuated vessel. A simple U-tube containing mercury is adequate for...
angular subtense
The measured planar or solid angle of related aspects of an optical system with respect to an optical axis.
cathode radiant sensitivity
Cathode radiant sensitivity refers to the ability of a photocathode to convert incident radiant energy, typically in the...
mode filter
A device used in measuring the attenuation of multimode optical fibers. A short reference length of fiber when combined with...
Fizeau fringes
Fizeau fringes are interference fringes observed in an interferometer, specifically in a Fizeau interferometer. The Fizeau...
focometer
A device used to measure the focal length of an optical system or lens.
x-ray crystal spectrometer
An instrument that measures the wavelengths of an x-ray spectrum by the diffraction of x-rays from a crystal with a given...
infrared jamming
A countermeasure used against heat seeking missiles to reduce their effectiveness. Normally it involves the emittance of...
cardinal points
Focal, nodal or principal points of a lens. If the respective distances of the object and image are measured from the...
stereo compilation
Extraction of three-dimensional measurements from a stereo pair of photographs.
fiber photometry
An optical recording technique that uses light source(s), a beamsplitting cube, light detector(s) and an optical fiber...
evaporation coating
Coating carried out in a sealed chamber evacuated by a mechanical pump in series with an oil diffusion pump to a pressure...
Shack-Hartmann wavefront sensor
The Shack-Hartmann wavefront sensor is an optical device used for measuring the wavefront aberrations of an optical system....
stylus profilometer
A measuring instrument used for surface profiling and quantifying the roughness of a material. The stylus is placed on the...
photogrammetry
Photogrammetry is a technique used to obtain accurate three-dimensional measurements of objects and environments through the...
line spectrum
A spectrum formed by radiation whose energy values of the property being measured cluster about at least one discrete value,...
permeability
Typically represented by the Greek letter μ, magnetic permeability is the measure of a material's ability to generate and...
fluorometer
An instrument used to measure the duration of fluorescence emanating from a biological sample to monitor and evaluate its...
fiber optic preform
A fiber optic preform is a cylindrical glass rod or tube used as the starting material for manufacturing optical fibers. It...
optogenetics
A discipline that combines optics and genetics to enable the use of light to stimulate and control cells in living tissue,...
anisotropy
Anisotropy refers to the property of exhibiting different values or characteristics when measured in different directions....
lateral extensometer
An extensometer used to measure deformations in the thickness of a plate caused by tension, compression or other stress.
infrared camera
An infrared camera, also known as a thermal imaging camera or IR camera, is a device that captures and visualizes the...
field tilt
The angle measured between the focal surface containing the image and a plane normal to the optical axis.
beamwidth
The angular width of a radiation beam. With respect to a conical beam of light, it is the vertex angle of the cone. The...
international candle
A unit of measurement of luminous intensity based on a physical standard, a set of calibrated carbon filament lamps. The old...
focal length
The focal length of a lens is the distance between the lens's optical center (or principal point) and the image sensor or...
micrometer
1. The SI unit of length equal to 10-6 m. Also called micron. 2. A screw thread device used to make accurate physical linear...
Martin's diameter
A specific method for measuring the diameter of irregular shaped particles, Martin's diameter is the measured distance...
turbidity
Turbidity is a measure of the cloudiness or haziness of a fluid caused by the presence of suspended particles. These...
radio telescope
An instrument designed to collect naturally formed extraterrestrial electromagnetic radiation within the radio frequency...
absolute luminance threshold
The minimum value of luminance for vision. The value may vary with age as well as dark adaption period. (Measured range...
parallel scanning
Parallel scanning refers to a method of acquiring data or images simultaneously from multiple sources or in parallel, rather...
photoelectric exposure meter
A device consisting of a microammeter, a photovoltaic cell and a battery. It is used for the measurement of scene brightness...
electric dichroism spectroscopy
The use of a krypton laser system for the measurement of small molecules aligned by an electric field, by analyzing the...
lidar
Lidar, short for light detection and ranging, is a remote sensing technology that uses laser light to measure distances and...
open-dish method
A measurement method for reflectance by gas ionization in which light passes through a vapor before and after reflection....
long-path absorption spectroscopy
The method that, by measuring the absorption along an atmospheric path at wavelengths ranging from two to a continuum, can...
electroreflectance spectroscopy
A type of electromodulation that measures changes in spectral reflectance.
radiation pyrometer
Also known as radiation thermometer. A pyrometer in which the radiant intensity from the source to be measured is used to...
segment height
In a bifocal spectacle lens, the vertical measurement of distance from the uppermost borderline of the bifocal segment to...
burst pressure
The measure used in vacuum technology to quantify the total pressure capacity of the ferrofluidic seal before it fails.
diffraction grating
A diffraction grating is an optical component consisting of a surface with a periodic structure of equally spaced, parallel...
epifluorescence microscopy
Fluorescence imaging technique in which the excitation light from the objective is directed into the sample producing...
abridged spectrophotometer
An instrument that uses optical filtration in order to measure the transmittance for a discrete range or specific number of...
machine vision system
A machine vision system is an integrated combination of hardware and software components designed to capture, process, and...
laser frequency measurement
Mod Method of obtaining precise temporal mode characteristics.
optical transform image modulation
A technique for detecting and measuring atmospheric pollution, in which an oscillating mirror directs half the incoming...
motion controller
In optics, a motion controller refers to a device or system that precisely controls the movement of optical components, such...
microdensitometer
The fundamental tool of microdensitometry, the microdensitometer is an instrument used for the precise measurement of...
laser rangefinder
A laser rangefinder is a device that uses laser technology to measure the distance between the device and a target. It...
color monitoring instrument
An instrument providing a continuous measure of color.
flowmeter
A flowmeter is a device used to measure the flow rate or quantity of a fluid passing through a particular point in a system....
particle image velocimetry
A whole-flow-field technique providing instantaneous velocity vector measurements in a cross-section of a flow that is...
absorptivity
The measured change in absorption at a single wavelength while altering experimental parameters such as the incident...
pyroelectric infrared detector
Unlike the thermocouple or bolometer, the pyroelectric infrared detector is a current source with an output proportional to...
measuring eyepiece
Also known as an eyepiece micrometer. A microscope eyepiece that has a finely divided scale ruled or photographed on a...
integration time
Integration time, in the context of optics, imaging systems, and sensor technology, refers to the duration over which a...
photometric
Pertaining to the measurement of the intensity of light.
isoperibol enclosure
An enclosure for a calorimeter that allows measurement of unusually low quantities of power and energy.
color temperature meter
A device containing two photocells behind deep red and blue filters to measure color temperatures. The amplifier gain is...
biomarker
A biomarker, short for biological marker, refers to a measurable and quantifiable indicator of a biological condition,...
photoacoustic calorimetry
Periodic interruptions of a light beam incident on an absorbing medium that produce heat, expansion and acoustic wave...
luminous intensity
Luminous flux emitted by a source in a given range of directions; the unit of measure is the lumen/steradian, now known as...
noise current
Any noise or current fluctuation that prevents precise measurement of the signal current. Both dark current and signal...
synthetic aperture radar
Imaging radar that increases the sweep of its along-track (or azimuth) capacity by measuring not only the time delay of the...
lens watch
A dial depth gauge graduated in diopters; a lens measure.
telephotometry
The principles and techniques involved in the use of telephotometers to measure atmospheric extinction.
half bandwidth
The term half bandwidth (HBW) generally refers to the width of a spectral band or frequency range at half of its maximum...
anisotropic
Anisotropic is a term used to describe a material or substance that exhibits different properties or behaviors in different...
refractive index contrast
A measure of the relative difference in refractive index between two optical materials. Most commonly used in fiber optics...
laser Doppler velocimeter
Device which determines particle velocity through the measurement of scattered interference of a beam pair from a single...
optical resolution
A measure of image quality produced by an optical system. May be specified in terms of cycles per millimeter, referencing a...
detective quantum efficiency
The square of the ratio of the measured detectivity to the theoretical maximum detectivity.
spatial resolution
Spatial resolution refers to the level of detail or granularity in an image or a spatial dataset. It is a measure of the...
scintillation counter
An instrument designed to measure radiation indirectly through the use of several phosphors and a photomultiplier tube. The...
transverse interferometry
The method used to measure the index profile of an optical fiber by placing it in an interferometer and illuminating the...
mode beating
In optics, "mode beating" refers to an interference phenomenon that can occur in laser systems with multiple longitudinal...
angle-tracking system
A system in which a sequence of direct measurements of the target position is fed into a tracking filter that may produce...
laser spark spectroscopy
A method of analysis in which a pulsed laser beam is used to heat a particle, producing a plasma, or laser spark. As the...
crosstalk
The measurable leakage of optical energy from one optical conductor to another. Also known as optical coupling.
radial distortion
An alteration in magnification from the center of the field to any point in the field, measured in a radial direction from...
shutter speed tester
A device used to measure the opening time of a shutter. The most common devices depend on the charging or discharging of an...
spectrometry
The study and measurement of spectra and their components.
stellar photometry
The utilization of photometric measurement to determine the relative magnitudes of the heavenly bodies.
fiber-coupled LED
A fiber-coupled LED (light-emitting diode) refers to an LED device that is optically coupled to an optical fiber for the...
focal collimator
A collimator having, at one end of a tube, an objective lens, and at the other, a reticle with a pair of spaced lines...
quantum sensing
Quantum sensing refers to a class of sensing technologies that leverage principles from quantum mechanics to enhance the...
mass spectrometer
A device used to measure the masses and relative concentrations of atoms and molecules. It utilizes the Lorentz force...
kron camera
Astronomical detector consisting of a photocathode isolated from the target by a coin value from which electrons are focused...
nit
Unit of measurement of brightness (luminance) equal to one candela per square meter.
goniometer eyepiece
An eyepiece having a rotating index or cross wire linked to an external 360° scale to allow measuring of angles in an...
Er:YAG laser
An Er:YAG laser is a type of solid-state laser that uses a crystal made of erbium-doped yttrium aluminum garnet...
optical activity
The capacity of a chiral substance such as a crystal or molecule to rotate the plane of polarized light that is transmitted...
millimeter (mm)
A unit of metric measurement, equal to 0.001 m. 25.4 mm equal 1 inch.
multichannel spectral analyzer
A spectrometric instrument that detects radiation simultaneously in multiple channels, sorts it spectrally from the deep...
optical table
An optical table, also known as an optical bench or an optical breadboard, is a specialized platform used in optics...
spectrobolometer
A combination spectrometer and bolometer that is designed to measure a narrow band of radiation from a star.
modulation spectroscopy
A method of spectral analysis in which some property of the sample is varied and the corresponding change is measured. The...
illuminometer
A photometric instrument used to measure the illumination falling on a surface. It may be photoelectric or visual.
current transient
A sudden, brief increase in current or voltage in a circuit that can damage sensitive components and instruments. Preventive...
spectral flow cytometry
Spectral flow cytometry is an advanced flow cytometry technique that expands the capabilities of traditional flow cytometry...
overall distance
The physical distance, measured along the optical axis, from the object to the image. Also called overall length.
integrating sphere
A hollow sphere coated internally with a white diffusing material and provided with openings for incident beam, specimen and...
acutance
In photography, the density gradient across an edge separating light from darkness, a physically measurable quantity that...
bench photometer
A device used to compare the luminous intensities of two sources by locating a point between the two light sources where the...
refracted ray method
The technique for measuring the index profile of an optical fiber by scanning the entrance face with the vertex of a high...
triangulation
A method of measuring distance by recording a single scene from two points of perspective. Surveying instruments can be...
sextant
A handheld navigational instrument used to measure the elevation angle of celestial bodies such as the sun. An image of the...
spectral repeatability
Spectral repeatability refers to the consistency and reproducibility of spectral measurements across multiple trials or...
comparator
1. An eyepiece or magnifier with a scale at its image plane. That scale is placed in contact with an object, permitting...
aiming circle
An instrument designed to measure angles in azimuth; used in general topographic work and military gunnery.
astronomical photography
The use of photographs to record astronomical objects and phenomena for purposes of physical observation and measurement of...
infrared modulated ellipsometry
A direct method of measuring refractive index that works best with flat-surfaced samples (i.e., those that are not dependent...
bandgap
In semiconductor physics, the term bandgap refers to the energy range in a material where no electronic states are allowed....
goniometer
A spectrometer or autocollimator used to measure prism angles.
metasurfaces
Metasurfaces are two-dimensional arrays of subwavelength-scale artificial structures, often referred to as meta-atoms or...
ratiometer
An electronic device that minimizes short-term drift effects and random measurement error inherent in alternate...
glossmeter
A photometer for measuring gloss by comparing the specular reflectance to that from a perfect specular reflector.
calorimetry
Calorimetry is a branch of science that involves the measurement of heat flow in physical or chemical processes. It...
feature extraction
In image processing and machine vision, the process in which an initial measurement pattern or some subsequence of...
feret's diameter
In microscopy, the measured distance between theoretical parallel lines that are drawn tangent to the particle profile and...
optical tooling level
A surveying device used to measure vertical displacement of target centers of scale lines from a horizontal plane generated...
kampometer
A device designed to measure radiant energy, particularly in the thermal region.
multiple wavelength interferometry
A specific form of phase shifting interferometry - commonly referred to as multiple wavelength phase shifting interferometry...
atomic absorption spectrometer
An atomic absorption spectrometer (AAS) is an analytical instrument used to determine the concentration of specific chemical...
minimum perceptible
The smallest object that may be seen, measured in terms of the angle subtended by the object measured at the eye. Also...
astronomical unit
The unit generally used to express distances within the solar system, and sometimes to measure interstellar distances....
ultraviolet fiber optics
Ultraviolet (UV) fiber optics refers to optical fibers that are designed and optimized for the transmission of ultraviolet...
diffraction efficiency
Diffraction efficiency is a measure of how effectively a diffractive optical element (DOE) or diffraction grating directs...
eikonometer
A scale attached to a microscope eyepiece that is seen superimposed on the image and that is used to measure the dimensions...
radiac
An acronym for radioactive detection, identification and computation. The term refers to the detection and measurement of...
transient calorimetric technique
A method of measuring total hemispherical emissivity of the plane surface of a solid that consists of thermally isolating a...
Risley prism
A Risley prism, also known as a Risley prism pair or Risley rotating prism, is an optical device used for controlling the...
quantum efficiency
Quantum efficiency (QE) is a measure of the effectiveness with which a device or system, typically in the context of...
photomultiplier tube
A photomultiplier tube (PMT) is a highly sensitive vacuum tube that detects and amplifies low levels of light. It is widely...
infrared light-emitting diode
An infrared light-emitting diode (IR LED) is a semiconductor device that emits infrared light when an electric current...
reflectometer
An instrument for measuring reflectance.
near-infrared camera
A near-infrared (NIR) camera is an imaging device designed to capture images in the near-infrared region of the...
divided circle spectrometer
A spectroscope having a divided circle and a means for the rapid reversal of prisms for the measurement of refractive index...
optical grating reflectance evaluator
A device for measuring diffraction grating efficiency at any angle of incidence, consisting of a reflectometer wherein the...
Rockwell hardness
Rockwell hardness (Rc) refers to a method for measuring the hardness of a material, primarily metals, using an indentation...
optical assembly
An optical assembly refers to a collection of optical components that are carefully arranged and aligned to perform a...
amplitude-modulated sensor
A type of fiber optic sensor that detects alteration in position, distance, pressure, liquid level or temperature by...
flame spectroscopy
The study of flames by means of a laser emitting blue light and a spectrometer to measure the green fluorescence created by...
tachometer
An instrument designed to measure the rate of rotation of components, such as shafts.
Fresnel number
In a lens, the square of the radius of its aperture divided by the product of the focal length and the wavelength. It...
minimum visible
The smallest area of uniform brightness that can be seen by the eye. It is measured in terms of the solid angle subtended by...
spherometer
An instrument for measuring the radius of curvature of a spherical lens or mirror surface. It may consist of a ring resting...
prism coupler
An instrument that measures the angle at which a prism can couple laser light into an optical waveguide; used to determine...
accelerometer
An accelerometer is a sensor or transducer that measures the rate of change of velocity of an object, or in simpler terms,...
linear field
The measured width of the field of view at any distance.
Raman spectroscopy
Raman spectroscopy is a technique used in analytical chemistry and physics to study vibrational, rotational, and other...
sag
1. In the geometric sense, an abbreviation for the term "sagitta,'' the height of a curve measured from the chord. ...
phase-change optical disc
An erasable data recording and storage medium that uses a laser to heat the crystalline surface of the disc to a certain...
baselength
The distance between pupil centers in a two-pupil system, measured perpendicularly to the optic axis.
band head
The measured wavelength of the most distinct edge of a spectral band.
common optoelectronics laser detection system
A laser warning and countermeasure system containing a sensor that indicates the direction of a laser beam, and analytical...
diopter scale
A scale located on the eyepiece focusing screw and used to measure the amount of defocusing of the eyepiece in diopters. The...
absorption meter
A measuring device that uses a light-sensitive cell or detector to determine the amount of light transmitted by a substance.
video measuring gauge
A device that calibrates the size, position or distance of objects imaged on a video screen.
reflectance spectrophotometer
An instrument that spectrally analyzes the flux reflected from a material. The reflected flux may be total, diffuse or...
laser velocimeter
A system that uses a continuous-wave laser to measure the velocity of an object by focusing the laser beam on the object,...
low-light-level instrumentation
Instrumentation designed to permit the perception, recording or measurement of scenes under conditions of low incident...
intrinsic photoconductivity
The absorption of a photon raising an electron across the forbidden gap from valence to conduction band of the semiconductor...
arc flash
An arc flash is a sudden release of electrical energy due to an electric arc — a continuous, high-current discharge of...
optical manufacturing tools and machinery
Optical manufacturing tools and machinery encompass a wide range of equipment, instruments, and systems used in the...
near-field scanning
A measurement technique used to determine the spatial distribution profile of an electrical or optical quantity of interest...
detectivity
A measure of the sensitivity of a detector; the reciprocal of noise equivalent power (NEP). See D*.
clinometer
An instrument for measuring the vertical angle of an object. It usually contains an accurately made protractor, a sensitive...
spectrophotometric analysis
The detection and measurement of spectral reflectance, spectral transmittance or relative spectral emittance, relative to...
detector
1. A device designed to convert the energy of incident radiation into another form for the determination of the presence of...
autostigmatic microscope
A microscope to which a beamsplitter and illuminated reticle have been added to measure the radius of curvature of a...
reflective spectroscopy
Reflectance spectroscopy is a technique used to analyze the reflective properties of materials across various wavelengths of...
atomic clock
An atomic clock is a highly precise timekeeping device that uses the vibrations or oscillations of atoms as a reference for...
film thickness gauge
An interferometer spectrometer designed to measure thicknesses of thin films or layers by recording the interferogram and by...
photographic sensitometry
The measurement of the responsivity of photographic media and of the relations between exposure and density of developed...
optical dynameter
A small low-power microscope or magnifier with a scale that is used to measure the exit pupil diameter and eye relief on...
dosimeter
A device used to detect and measure the quantity of exposure to nuclear or x-ray radiation, and dependent on the fact that...
double-pulsed holographic interferometry
Interferometric measurement of the interference pattern recorded when a complex object is illuminated by two laser pulses...
adaptive optics
Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effects of...
photoelectric photometry
The use of photoelectric sensors to detect and measure the intensity of a light source. This application, as compared to...
waveform analyzer
A device designed to measure the amplitude and frequency of the elements in a complex waveform.
equidensitometry
1. The use of an electronic microdensitometer to measure points of equal density on a photographic deposit. 2. A technique...
instantaneous field of view
Instantaneous field of view (iFOV) is a term commonly used in the context of remote sensing, imaging systems, and optical...
optics
Optics is the branch of physics that studies the behavior and properties of light, including its interactions with matter...
Bragg method of crystal analysis
A technique in which a beam of x-rays is directed against a crystal, the atoms of which, because of their lattice...
biometrics
Biometrics refers to the automated recognition of individuals based on their physiological or behavioral characteristics....
degree of coherence
A quantitative measurement of the coherence of a light source; equal to the visibility (V) of the fringes of a two-beam...
heterochromatic photometry
Light measurement by comparison of the luminances of unlike chromaticities.
interference microscope
A special form of microscope that utilizes interference for observing and measuring the phase and optical thickness in...
Mach-Zehnder interferometer
A Mach-Zehnder interferometer is an optical device used to measure the phase difference between two collimated beams of...
diffractometer
A measurement device used to study the structure of matter using the diffraction of electromagnetic radiation.
conjugate ratio
The ratio between the object distance and the image distance measured along the principal axis of a lens or mirror. An...
CubeSat
A CubeSat is a type of miniaturized satellite characterized by its standardized size and modular design. CubeSats are...
differential absorption lidar
A lidar (light detection and ranging) technique used in pollution monitoring. Two light beams are emitted simultaneously,...
gray
1. A measure of absorbed dose, equal to the energy imparted by ionizing radiation to a mass of matter corresponding to 1 J...
gamma-ray spectrometer
An instrument used to detect and measure the energy distribution of gamma rays. It has been used to chart the radioactivity...
marhic method
Nondestructive measurement of the delta and alpha of clad optical fibers that involves interferometry with the fiber...
sonde
A ruggedized scintillation counter used in oil well logging. The cylindrical housing contains a gamma ray source, a...
Helmholtz reciprocal relationship
The capability of the spatial distributions of incident and reflected flux to interchange completely without alteration of...
optical comparator
Typically used for the examination of manufactured or engineered parts, an optical gauging device, in which a backlight is...
spectral domain optical coherence tomography
Spectral domain optical coherence tomography is an imaging technique used in medical diagnostics, particularly in...
spectral width
A measure of the wavelength extent of a spectrum.
hyperchromic shift
Hyperchromic shift refers to an increase in the absorption of light, leading to a higher absorbance, often observed in...
reflection coefficient
Parametric measurement for elliptical fiber and cable expressed as a ratio of the two-directional flow of power through the...
spectroradiometer
A spectroradiometer is a device used to measure the intensity of light at different wavelengths across the electromagnetic...
picosecond spectroscopy
A method of measuring complex sequential photosynthetic reactions by varying the pulse time and wavelength of light...
photodetector
A photodetector, also known as a photosensor or photodiode, is a device that detects and converts light into an electrical...
Munsell color system
Founded by professor Albert Munsell. In the field of colorimetry, the Munsell color system is a color space that identifies...
embedded laser
The term "embedded laser" typically refers to a laser device that is integrated or embedded into a larger system or...
disc calorimeter
A device that provides simple and reliable laser power and energy measurement. Essentially a heat flux sensor producing an...
photometry
Photometry is the branch of science that deals with the measurement of light, particularly in terms of its intensity and the...
surface-enhanced Raman spectroscopy
Surface-enhanced Raman spectroscopy (SERS) is an analytical technique that combines the principles of Raman spectroscopy...
actinometer
A device that measures the intensity of photochemically active radiation, particularly from the sun. One form of this...
velocity modulation laser spectroscopy
A method of measuring negatively charged phase ions using a color-center or lead-salt diode laser.
machine vision lighting
Machine vision lighting refers to the use of specific lighting techniques and equipment in the field of machine vision,...
multi-axis alignment
Multi-axis alignment refers to the process of aligning or adjusting components or systems in multiple spatial dimensions or...
absorption spectrophotometer
Measures the absorption or sample transmittance over a range of specified wavelengths. Sample may be placed within the...
pulse video thermography
A noncontact, nondestructive method of measuring defects in thin composite materials, using a xenon flashtube to generate...
PIN photodiode
A PIN photodiode is a type of photodetector or semiconductor device used to convert light signals into electrical signals....
beam profiling
Beam profiling is a technique used to characterize and analyze the spatial intensity distribution of a laser beam. It...
MEMS fiber optic switch
A MEMS fiber optic switch is a microelectromechanical system (MEMS) device designed to selectively route optical signals...
holographic particle velocimetry
A method of measuring flow velocity by seeding the flow with neutrally buoyant particles and using a pulsed laser to...
optical encoder
A device designed to measure linear or rotary motion by detection of the movement of markings on a transparent medium past a...
absorption spectroscopy
Experimental method of measuring the transmission of a given sample as a function of the wavelength.
laser absorption spectroscopy
An experimental research technique by which absorbed or unabsorbed radiation is analyzed in order to characterize and...
Callier coefficient
The coefficient termed by Callier as the ratio between the density of photographic negatives measured by parallel light and...
qubit
A qubit, short for quantum bit, is the fundamental unit of information in quantum computing and quantum information...
mandrel wrap test
A means of testing optical fiber for macrobending losses by wrapping the fiber once at very low tension around a mandrel,...
scopometer
A device used to take turbidimetric or nephelometric measurements by considering the contrast between a constant brightness...
Ritchey-Common test
An interferometric method for describing the surface shape of large coated or uncoated optical flats. The procedure uses a...
goniophotometer
A device used to measure directional reflectance, with light collection restricted to a narrow range of angles of which the...
attosecond-pump attosecond-probe spectroscopy
Attosecond-pump attosecond-probe spectroscopy (APAP) is an advanced technique in ultrafast spectroscopy that allows...
Maddox rod
Lenslike composition of stacked glass cylinders through which a spot of light appears as a streak perpendicular to the...
strain measuring equipment
germicidal UV
Germicidal ultraviolet (GUV) refers to a specific range of UV radiation that has disinfectant properties capable of killing...
photochemical hole burning
A method of producing disks for erasable optical data storage. Information is recorded by a laser beam that generates pits...
edge thickness difference
The maximum variation in thickness of a lens as measured around a diameter centered on the optical axis. The ETD divided by...
light sectioning
Technique for measuring the volume bulk of materials as they move along a conveyor with an accuracy of better than 1...
frame rate
Frame rate refers to the frequency at which consecutive images, or frames, are displayed in a video sequence. It is...
atomic force microscope
An atomic force microscope (AFM) is a high-resolution imaging and measurement instrument used in nanotechnology, materials...
fiber optic gyroscope
A fiber optic gyroscope (FOG) is a type of gyroscope that uses the interference of light waves to detect changes in...
Fresnel reflection method
A method for measuring the index profile of an optical fiber by measuring the reflectance as a function of position on the...
optical time-domain reflectometer
An optical time-domain reflectometer (OTDR) is a specialized instrument used in optical fiber communications to characterize...
photometric equipment
Photocells of various kinds used to measure photometric quantities; i.e., intensity, luminance and illuminance. Meter...
adiabatic laser colorimetry
Method for studying absorption coefficients of low-loss materials, in which a sample is allowed to come to thermal...
optical memory
1. The direct storage of data as bits in memory using optical systems and properties. The memory makes use of a laser beam...
fluence
Fluence is a term used in various scientific and technical disciplines to describe the amount of something per unit area....
electrostrictive
A common form of high-precision, ceramic-based actuator capable of moving and measuring at the nanometer level.
cutback technique
A technique for measuring fiber attenuation or distortion by performing two transmission measurements. One is at the output...
ultramicrometer
A system used to measure very small displacement by electrical means.
cyanometer
An instrument designed to measure the proportion of light emitted by a source in the blue region of the spectrum.
dispersive power
A measure of the dispersive properties of a glass. The relative dispersion is defined as: where C, D, and F refer to the...
ophthalmology
Ophthalmology is a branch of medicine that focuses on the anatomy, physiology, and diseases of the eyes and visual system....
autocollimator
An autocollimator is an optical instrument used for measuring small angular deviations with high precision. It operates on...
opacity
A measure of a material's inability to transmit light, equal to the reciprocal of its transmittance.
spectrophone technique
Gas detection measurement technique that uses a built-in capacitative microphone to calculate the amount of absorbed laser...
optical density
A measure of the transmittance through an optical medium. Optical density equals the log to the base 10 of the reciprocal of...
near-infrared spectrometer
A near-infrared (NIR) spectrometer is an analytical instrument used to measure the absorption, transmission, or reflection...
optical caliper
A device for measuring linear dimensions. The optical caliper generally consists of two circularly mounted mirrors whose...
light pen
A handheld, light-sensitive device that is used with a display console to directly change, measure or erase the visual...
fluorometry
The analysis and measurement of the fluorescence emitted by a source. Fluorometric processes are more sensitive than light...
ultrasonic detector
A mechanical, electrical, thermal or optical detector designed to identify and measure ultrasonic radiation.
spectrum measuring instrument
A traveling microscope or an automatic microdensitometer used to measure the spectrum plate obtained in a spectrograph.
curvature
The measure of departure from a flat surface, as applied to lenses; the reciprocal of radius. Applies to any surface,...
optoelectronics
Optoelectronics is a branch of electronics that focuses on the study and application of devices and systems that use light...
functional near-infrared spectroscopy
Functional near-infrared spectroscopy (fNIRS) is a non-invasive neuroimaging technique that measures changes in hemoglobin...
sidereal time
Frequently used in astronomical measurement, it is based on the diurnal rotation of a star relative to the fixed stellar...
cold atom
Cold atoms refer to atoms that have been cooled to extremely low temperatures, typically in the microkelvin (µK) to...
optical time-domain reflectometry
A method for characterizing a fiber wherein an optical pulse is transmitted through the fiber, and the resulting light...
3D laser line profile sensor
A 3D profile sensor, also known as a 3D profiling sensor or 3D depth sensor, is a technology that is used to capture and...
mean solar time
One of two types of solar time - the other being apparent solar time - the mean solar time is the time measured by the...
nodal bench
A bench with instrumentation including a collimator, a microscope, positioners and a nodal slide used to rotate a lens about...
etaloning
Etaloning is an optical phenomenon that occurs in imaging systems, particularly in devices such as spectrometers,...
Debye-Sears ultrasonic cell
A device used in ultrasonic imaging to measure the velocity and attenuation of compressional waves in a transparent liquid...
single-photon avalanche diode
A single-photon avalanche diode (SPAD) is a specialized type of photodetector designed to detect extremely weak optical...
phase-modulated sensor
A phase-modulated sensor is a type of sensor that uses modulation of the phase of a signal to measure changes in a physical...
ultrasonic
Ultrasonic refers to sound waves with frequencies higher than the upper audible limit of human hearing, typically above...
Sagnac interferometer
A type of interferometer in which two coils of optical fiber are arranged so that light from a single source travels...
quantum key distribution
Quantum key distribution (QKD) is a method of secure communication that utilizes principles from quantum mechanics to...
potentiometer
A device designed to measure electromotive force or electrical difference potential.
diopter
A unit of optical measurement that expresses the refractive power of a lens or prism. In a lens or lens system, it is the...
nuclear quadrupole resonance spectroscopy
A chemical detection technique used to measure molecules that have a magnetic dipole moment. The analysis is directed to...
equivalent wavelength
In surface height measurement of optics with steep slopes, the use of two short visible wavelengths to synthesize a longer,...
photographic resolution
A measure of the ability of a photographic system to record fine detail. Usually stated in terms of cycles per millimeter on...
segment width
In spectacle lenses, the lateral measurement of a multifocal segment at its maximum width.
eye test apparatus
Instruments used by ophthalmologists and optometrists to study the eye. There are, for instance, the ophthalmoscope to...
filovirus
Filoviruses are a family of viruses that are responsible for severe and often fatal hemorrhagic fevers in humans and...
air dose
A quantitative measure of the amount of radiation given off by an instrument, expressed in roentgens per unit of free air.
single-molecule FRET
Single-molecule Förster resonance energy transfer (smFRET) is a specialized technique in biophysics and molecular...
space pattern
On a test chart, the pattern designed to direct and measure geometric distortion.
Secondary Speckle Pattern
A self-interference effect that generates random patterns; secondary speckle pattern (SSP) typically occurs in diffuse...
radiuscope
A microscope to which a beamsplitter and illuminated reticle have been added that is used to measure contact lenses.
scanning tunneling microscope
A high-resolution imaging instrument that can detect and measure the positions of individual atoms on the surface of a...
microphotometry
The measurement of the intensity of spectral lines by the examination of a very small area under a microscope and the...
circular dichroism
Circular dichroism (CD) is a spectroscopic technique used to study the structural characteristics of chiral (asymmetric)...
dots per inch
A measurement of the spatial resolution of a line or area array in an optical character recognition scanning device.
laser-light-scattering photometer
A scattering photometer using scattered light in the solid angle 4.51+0 19° with respect to the forward direction, and...
infrared thermistor
A thermistor that uses a semiconductor that is sensitive to infrared radiation to measure the radiation's intensity.
photoelectric spectrophotometer
A system that consists of a spectrophotometer with a photoelectric detector for measurement of radiant energy.
telephotometer
An instrument used to measure the luminance (brightness) of a distant object. The object is viewed through a small...
magnetometer
A magnetometer is a scientific instrument used to measure the strength and/or direction of a magnetic field. It can detect...
x-ray diffractometer
An instrument that uses a crystal to diffract x-rays for the measurement of the intensities of the diffracted rays.
unit of error
A unit of measurement in a rangefinder corresponding to 12 s of arc in the apparent field.
astrometry
The analysis and measurement of celestial bodies, their motions and positions.
laser speckle
Sparkling granular pattern that is observed when an object diffusely reflects coincident laser light. Speckle appears as an...
nodal testing
The measurement of first- and higher order properties of a lens and its formed image, including effective focal length, back...
etalon
An etalon is an optical device that consists of two parallel reflecting surfaces separated by a precise and known distance....
dilatometer
An instrument used to measure expansion of solids, liquids and gases.
measuring wedge
A wedge in a rangefinder or heightfinder used to displace the image produced by one telescope so that it coincides with that...
Knoop hardness
A measurement of the hardness of a material as determined by the penetration depth of a diamond stylus under a specified...
lens testing equipment
Lens testing equipment refers to a range of specialized tools and instruments used to evaluate the optical performance,...
lensometer
An ophthalmic instrument used to measure the magnitude and direction of the maximum and minimum powers of a spectacle lens,...
photoelectric reflectometer
A photoelectric photometer used to measure the reflectance of a surface.
lock-in amplifier
A lock-in amplifier is a specialized electronic instrument used to extract and measure small signals embedded in noise or...
probe
Acronym for profile resolution obtained by excitation. In its simplest form, probe involves the overlap of two...
optical air mass
A measure of the optical path length for light traveling from the sun or other celestial source through Earth's atmosphere...
reticle
An optical element located at an image plane, containing a pattern that assists in pointing an instrument or measuring...
rangefinder
1. An optical distance finder that depends on triangulation of two convergent beams on an object from disparate view points....
mean spherical intensity
The average intensity of a light source measured over all directions.
coordinate measuring microscope
An instrument used to measure the coordinates of a point on an object such as a photographic plate.
Becke apertometer
Device used to measure the numerical aperture of a microscope, composed of a 14-mm-thick glass block with numerical aperture...
photoplethysmography
Photoplethysmography (PPG) is a non-invasive optical technique used to detect changes in blood volume in tissues. It...
lumen
A lumen is a unit of measurement used to quantify the amount of luminous flux, which is the perceived power of light. In...
light meter
Any device that is used to sense and measure light. See exposure meter; photoelectric exposure meter; photoelectric...
theodolite
A precise telescope set on a pair of rotation axes, the horizontal and vertical axes equipped with two divided circles. One...
traveling microscope
A measuring instrument composed of a microscope and reticle, and mounted on a calibrated slide mechanism. May be used...
Z-scan
A technique for determining the nonlinear optical properties of a sample material by moving the sample through a focused...
incident light meter
An exposure meter designed to measure the light striking an object and used at a suitable location in a scene.
microspectrograph
A microspectroscope equipped with a sensing and recording device, such as a camera, to measure the spectrum formed by...
ultraviolet photoemission spectroscopy
A technique for measuring the energy spectrum of electrons emitted during the absorption of ultraviolet radiation. This...
meta-optics
Meta-optics, also known as metasurface optics or flat optics, is a branch of optics that involves the design, fabrication,...
calorimeter
An instrument used to measure the change of heat content of a system by measuring microwave power in terms of generated heat.
near-infrared spectroscopy cerebral oximetry
A monitoring technique used to measure the oxygen saturation levels in the brains of patients, commonly in operating room...
alidade
An old name for the rotating arm moving about an axis of rotation over a divided circle used to measure angles. Now the term...
bathymetric map
A surveying map representing measurement of depth, particularly that of the ocean.
swept source optical coherence tomography
Swept-source optical coherence tomography is an imaging technique used in medical diagnostics, particularly in...
holographic crystal growth analysis
The study of crystal growth from the molten stage utilizing a holographic system wherein interferometric techniques record...
label-free
Label-free refers to a technique or method that does not require the use of additional labels, tags, or markers to detect or...
optical continuous wave reflectometer
An instrument used to measure backscatter as well as optical return loss and reflectance within an optical fiber system by...
Michelson stellar interferometer
An interferometer constructed to be positioned on a telescope to measure the angular separation of the components of double...
interferometric calorimetry
Heat measurement method in which the sample is made part of the interferometer and the temperature increase is determined by...
apertometer
An instrument designed to measure the numerical aperture of an objective.
luxmeter
An illuminometer designed to measure illumination in terms of luxes.
photographic photometry
A form of photometric measurement, often used with light sources that are transparent or fluctuating, in which a...
split-beam laser interferometer
An instrument that divides a single laser beam in two and uses one half as a sensing beam and the other as a reference beam,...
laser strainmeter
An instrument usually consisting of a very long interferometer, 3 to 800 m, and a laser light source for the study and...
time-to-amplitude converter
A time-to-amplitude converter (TAC) is an electronic circuit that converts a time interval between two events into an...
resolving power
A measure of an optical system's ability to produce an image which separates two points or parallel lines on the object. See...
residual gas analysis
A measurement in optical thin-film coating processes whereby the gases remaining in the vacuum chamber after coating are...
retinal reflectometry
The study of the quality of the image formed on the retina by the measurement of the flux reflected from the eye when the...
InGaAs photodiode
An InGaAs photodiode refers to a photodetector device that is constructed using a semiconductor material composed of a...
laser ceilometer
A device used for measuring the height of clouds from a position on the ground. Measurement technique uses a vertically...
radiometry
Ratiometry is a technique used in various scientific fields, particularly in analytical chemistry and biochemistry, to...
retroreflection
Retroreflection is a phenomenon in optics where light is reflected back toward its source, typically in a direction nearly...
lens measure
A tool used to determine the curvature of a lens surface in terms of dioptric power. See lens watch; spherometer.
Geiger counter
Also called Geiger-Müller counter. An instrument designed to detect and measure radioactivity through the use of a...
angular tracking
A laser radar application in which a sequence of direct measurements of target position is fed into a tracking filter to...
optical coherence tomography angiography
Also known as OCT-A, optical coherence tomography angiography is an imaging technique that uses light waves to measure...
edge response
Intensity distribution in the image of an edge. The gradient of the edge-response curve is a measure of the image quality of...
photoelectric counter
A device used to count objects that pass a given point by allowing each object to obstruct a beam of light falling on a...
Abbe refractometer
Device which measures the index of refraction of glass as well as the dispersion over visible range.
fiber Bragg grating
A fiber Bragg grating (FBG) is a type of optical filter that is inscribed or "written" into the core of an optical fiber. It...
FTIR spectrometer
FTIR (Fourier transform infrared) spectrometer is a powerful analytical instrument used to obtain an infrared spectrum of...
Hartmann test
A test for spherical aberration, coma or astigmatism in which incident rays from a point source are isolated by small holes...
integral density
With respect to color photography, the measurement of the way the color film modulates the radiant flux in the optical...
differential spectrophotometry
The measurement of the spectrum bands formed by a spectroscopic sample, based on the differences between the sample and the...
optical bench
A support for optical parts comprising a solid bed that permits precise longitudinal movement of one component relative to...
emissometry
The use of a material's emissivity to measure absorption. It is useful as an absorption loss measurement technique, since at...
spectrosensitometer
A sensitometer having a continuously controlled monochromator to measure spectral sensitivity and contrast of photographic...
Jamin refractometer
An instrument designed to measure the index of refraction of a gas by the interference patterns formed by two beams, one of...
enzyme-linked immunosorbent assay
An enzyme-linked immunosorbent assay (ELISA) is a laboratory technique used to detect and measure the presence of specific...
photochemical detector
An instrument used to detect and measure radiant energy by the formation of a chemical reaction.
enhanced picture archiving and communication system display
Enhanced picture archiving and communication system (PACS) display (ePAD) is a software tool used in medical imaging to...
Hefner unit lamp
A gas lamp used in the early 1900s as a physical standard for measurement of luminous intensity. The Hefner unit was...
photoelectric pyrometer
An instrument used to measure the temperature of a source through the use of photoelectric cells to detect and measure the...
positioning
Positioning generally refers to the determination or identification of the location or placement of an object, person, or...
quantum cascade laser
A quantum cascade laser (QCL) is a type of semiconductor laser that operates based on the principles of quantum mechanics....
full width half maximum
Full width half maximum (FWHM) is a measure of the extent of a function. Given by the difference between the two extreme...
metalens
A metalens, short for "metasurface lens," is a type of optical lens that uses nanostructured materials to manipulate light...
reflective
The term reflective is an adjective that describes the ability of a surface or material to reflect light or other forms of...
phenotype
In biology, particularly genetics and evolutionary biology, the phenotype refers to the observable characteristics or traits...
Dobson spectrophotometer
A spectrophotometer that measures the amount of ozone in the atmosphere through a comparison of solar energy at two...
piezoresistance
Piezoresistance is a phenomenon in materials science and physics where the electrical resistance of a material changes in...
high-speed motion camera
A high-speed motion camera, also known as a high-speed camera or slow-motion camera, is a specialized imaging device...
abrasion mark
Optical surface damage due to abrasive rubbing. Abrasion damage affects are less than the thickness of the optical coating...
atomic time
Any system of time measurement that is based on atomic resonances. The transition times between the hyperfine levels of...
transducer
A transducer is a device or component that converts one form of energy into another. It is commonly used in various fields,...
ultraviolet-visible spectrometer
Also known as UV-VIS spectrometer, a device that measures the absorbance, reflectance or transmittance of light in the...
exposure meter
An instrument used to measure the light from a scene to be photographed and to indicate the camera lens and shutter settings...
glass dosimeter
A device that detects and measures the quantity of exposure to nuclear radiation. It uses a special glass rod that...
lateral shearing interferometer
A lateral shearing interferometer is an optical device used in interferometry to measure phase differences between two beams...
surveying instruments
Instruments used for measuring angles and occasionally lengths on the ground. The principal surveying instruments are the...
manometer
A device used to measure the pressure of gases and vapors, without regard to atmospheric pressure.
geodimeter
Trade name referring to an instrument that determines surface distances by measuring the length of time it takes for a...
rise time
Measurement of the time elapsed during the current output change from 10 to 90 percent in a photoconductor.
phosphor thermometry
A method for remote measurement of the temperature of moving surfaces in harsh environments by using a laser to stimulate...
projection thermography
The measurement of surface temperature by a thermograph that forms a pattern of the heat radiated by the surface on a...
gravimeter
An instrument capable of precise measurements of the Earth's gravity. This permits the detection of small changes in local...
optical profiler
Also known as a white-light interferometer. Measures surface texture and shape from nanometer-scale roughness to...
infrared spectroscopy
The measurement of the ability of matter to absorb, transmit or reflect infrared radiation and the relating of the resultant...
photographic shutter efficiency
A measure of the total light passed by a shutter during an exposure, compared with the light that could be passed by an...
skew angle
The angle at which photoelectric sensors are aligned to prevent light from being reflected back to the sensor from the...
ultraviolet reflectance
Ultraviolet reflectance refers to the ability of a material or surface to reflect UV light. Ultraviolet light is...
bolometer
A thermometric instrument used for the detection and measurement of radiant energy. Its essential component is a short...
field of view
The field of view (FOV) refers to the extent of the observable world or the visible area that can be seen at any given...
photographic radiometry
The use of photographic recording equipment to measure radiant energy. With this procedure, many measurements of radiant...
optical fiber optic switches
Optical fiber optic switches are devices used in optical fiber communication systems to selectively route optical signals...
jig transit
An optical instrument containing a gimballed sighting telescope, used to measure angular relationships in horizontal and...
refractometer
An instrument used to measure the refractive index of solids and liquids. Several types exist, the most common being the...
interphako interference microscopy
Measures the refractive indices axially from the fiber profile. Microscopy technique provides an interferogram with high...
nitrogen vacancy
A nitrogen vacancy (NV) refers to a specific type of defect or impurity in a crystal lattice where a nitrogen atom replaces...
exposure index
A measure of film speed sensitivity to light.
modulation transfer function analysis/measurement equipment
MTF analysis/measurement equipment refers to instruments and tools used to measure and analyze the modulation transfer...
fluorescence lifetime
Fluorescence lifetime refers to the average time it takes for a fluorophore, a molecule that absorbs light at one wavelength...
spot meter
A telescopic light-sensing meter used to measure illumination levels of small regions at a distance of many feet; it is used...
fluorescence lifetime imaging
Fluorescence lifetime imaging (FLIM) is an advanced imaging technique that provides information about the lifetime of...
Laurent polarimeter
A Laurent polarimeter is an instrument used in optics for measuring the rotation of plane-polarized light caused by...
colorimetric photometer
A photometer that uses a set of color filters to measure the intensity of light in various regions of the spectrum.
quantum-ehanced metrology
Quantum-enhanced metrology refers to the use of quantum mechanics principles and techniques to enhance the precision and...
integrated energy
Also known as integrated exposure. A measurement of light from sources that vary rapidly with time, defined as the integral...
serpentine bend mode filter
A device used in measuring attenuation in optical fiber. The loss caused by the bends in a short reference length of fiber...
telemetry
The science of sensing and measuring information at some remote location and transmitting the data to a convenient location...
sensitometer
An instrument for determining the sensitivity of a photographic film to light. The film is given either a stepped exposure...
laser texturing
Laser texturing is a manufacturing process that involves using a laser beam to selectively modify the surface of a material,...
nox
Equal to 10-3 lux; used in measuring low values of illumination and luminance.
Casimir force
The Casimir force is a quantum phenomenon that results in an attractive force between two closely spaced uncharged...
distributed feedback laser
A distributed feedback laser (DFB laser) is a type of semiconductor laser diode designed to emit coherent, narrow-bandwidth...
spectrometric analysis
The analysis of spectra and their components, determined from their measurements.
fiber optic sensor
A fiber optic sensor is a device that uses optical fibers to detect and measure physical, chemical, biological, or...
slab interferometry
The method for measuring the index profile of an optical fiber by preparing a thin sample that has its faces perpendicular...
attenuation meter
A device used to measure power loss in fiber optic connectors, cables or systems.
deflection under static load
For an optical table, the amount of displacement that occurs when a heavy load is placed or moved on the surface. To measure...
meter
1. The basic unit of length in the metric system, equal to 39.37 in. or 3.28 ft. 2. Any device or instrument used for...
remote sensing
Remote sensing is a method of data collection and observation where information about objects, areas, or phenomena on...
transverse scattering
The method for measuring the index profile of an optical fiber or preform by illuminating it coherently and transversely to...
polarimetry
The measurement of the rotation of the plane of polarization of radiant energy, usually through the use of a polarimeter.
vertometer
A device that measures the back focal length or vertex power of a lens.
gyroscope
A gyroscope is a mechanical device consisting of a spinning disk or wheel mounted on a spinning axis in such a way that its...
absolute white
A perfect diffuser that exists only as a concept, or a white with known spectral characteristics used as a reference in...
angle gauge
A glass or metal measurement tool having a precisely calibrated angle between two of its faces.
scanner
1. A device used to trace out an object and build up an image. One of the most common of these types is video scanning. The...
colorimetry
The methods used to measure color and to define the results of the measurements.
resonator
A resonator is a device or system that exhibits resonance, which is a phenomenon that occurs when an external force or...
flow cytometry
Flow cytometry is a powerful technique used in biology and medicine for the quantitative analysis of the physical and...
galvanometer
An instrument for detecting or measuring small electric currents.
mean spherical luminous intensity
The average luminous intensity of a point light source measured over all directions.
hematofluorometer
A photoanalytical instrument for analysis of jaundice conditions in infants that measures bilirubin (a breakdown product of...
extensometer
1. A strainmeter capable of measuring the change in the relationship between two reference points, provided that the points...
millidiopter
A unit of metric measure equivalent to 1 thousandth (or 10-3 ) of the standard unit of optical power which is the diopter (1...
Baume scale
The scale for floating hydrometers used to measure the specific gravity of a polishing suspension. The depth of immersion is...
aerial photogrammetry
The application of aerial photographs as a means of measurement in map making and surveying.
photoelectric colorimeter
A system having a photoelectric detector for the measurement of three quantities related by linear combination to...
photoelectron holography
A technique proposed for studying the atomic structure of crystals by measuring the interference pattern generated when the...
normal
Sometimes referred to as the surface normal or 'surface norm'; the normal is an axis that forms right angles with a surface...
spectroreflectometer
A spectrophotometer specially designed to measure spectral reflectance.
modulation transfer function
Also called sine wave response and contrast transfer function. The modulation transfer function is the ratio of the...
photoclinometer
A photographic recording instrument that measures deviation from the vertical of a drilled well or mine.
metabolic imaging
Metabolic imaging refers to the visualization and quantification of metabolic processes within living organisms, tissues, or...
plate crystal
Any crystalline material whose length is much less than its measured diameter.
sensitometry
Primarily the measurement of photographic sensitivity of certain materials such as photographic film. It refers to the...
photoelectric receiver
An instrument that uses a photocell to detect and measure the intensity of incident light.
ring-laser gyroscope
A solid block of glass-ceramic material with holes drilled the length of all four sides, and mirrors attached to the corners...
steradian
The unit solid angle subtended at the center of a sphere by an area on its surface equivalent to the square of the radius;...
laser damage threshold
The laser damage threshold refers to the maximum level of laser intensity that a material can withstand without experiencing...
balloon-borne astronomical system
Any instrument or system carried by a balloon to the upper atmosphere to measure and record atmospheric information, such as...
fluorescence correlation spectroscopy
A powerful method, referred to as FCS, for determining the average diffusion coefficients of fluorescent molecules in...
Golay cell
A thermal radiation detector consisting of a small cell with a blackened plastic front face that bulges slightly when heat...
infrared detector
An infrared detector is a device that is used to detect and measure infrared radiation, which lies beyond the visible...
laser anemometry
The process by which laser emission is used in measuring fluid velocity and, more specifically, the detection of air and...
quantitative phase imaging
Quantitative phase imaging (QPI) is an advanced imaging technique used in microscopy to measure and analyze the optical...
Pirani gauge
A vacuum gauge designed to measure very high degrees of vacuum by thermal conduction.
nuclear magnetic resonance spectroscopy
That branch of spectroscopy that applies to the study of interactions between energy and atomic nuclei. The simultaneous...
three-filter densities
Integral densities that are measured relative to arbitrarily selected red, green and blue filters.
fluorescence decay system
A device, also called a fluorescence lifetime instrument, that measures decay curves of fluorescing samples. It generally...
radiation dosimetry
The detection and measurement of nuclear and x-ray radiation.
fall time
Measurement of the interval during which a photodetector's signal and output current drops from 90 to 10 percent.
nanopositioning
Nanopositioning refers to the precise and controlled movement or manipulation of objects or components at the nanometer...
FMCW lidar
FMCW lidar stands for frequency-modulated continuous wave lidar. It is a type of lidar (light detection and ranging)...
differential interferometer
A device that produces an interferogram that can be directly related to the temperature gradient and thereby provides a...
photoacoustic gas cell
A device for measuring absorption coefficients in which a confined, nonabsorbing gas fills the space inside the cell between...
target size and orientation
Angular tracking measurement estimated from the properly normalized image second-moment tensor.
laser cavity
A laser cavity, also known as an optical cavity or resonator, is a fundamental component of a laser system. It is a confined...
numerical aperture
The sine of the vertex angle of the largest cone of meridional rays that can enter or leave an optical system or element,...
beam profiler
A device that measures the spatial distribution of energy perpendicular to the propagation path of a radiant beam. An energy...
fluctuation spectroscopy
A technique developed to measure the molecular weight of macromolecules by analyzing the spontaneous fluctuations that occur...
spatial phase shift
The change in position of the image of a sine wave object from its ideal position. Usually measured in degrees with...
brightness meter
An instrument for measuring the brightness (luminance) of a scene. It may be a spot meter, covering an area of a degree or...
color comparator
1. A device used in chemistry to compare the colors of solutions held in flat-bottomed tubes and viewed along the length of...
Bose-Einstein condensate
A Bose-Einstein condensate (BEC) is a state of matter that forms at temperatures close to absolute zero. It is named after...
spatially offset Raman spectroscopy
Spatially offset Raman spectroscopy (SORS) is a technique that extends traditional Raman spectroscopy by incorporating...
mode field diameter
For a single-mode fiber, the measurement of the irradiance distribution at the fiber's end face.
volumetric imaging
Volumetric imaging refers to the capture, visualization, and analysis of three-dimensional (3D) information from a volume of...
target angular position
Measurement estimated from the position of the image's centroid.
ring micrometer
A flat, round micrometer that is placed in the focal plane of a telescope to measure difference in right ascension and...
profilometry
Measurement of surface roughness or quality through the use of a diamond-pointed stylus connected to a coil in an electric...
torque
A calculated measure of the ability of an incident force to cause an object to spin. The spin speed of any given object is a...
quantum
The term quantum refers to the fundamental unit or discrete amount of a physical quantity involved in interactions at the...
surface profile
A representation of the shape of a surface, including any roughness or other irregularities. The profile can be generated by...
calcite interference microscope
A microscope that allows examination of a small crystal and conveniently provides linearly polarized object and reference...
scanning coherent slope microscopy
Measures by heterodyning interferometry the local slope of a vibrating sample. The method allows the reconstruction of a...
radiometer
A device used to measure the intensity of radiant energy.
mixed signal oscilloscope
A mixed-signal oscilloscope (MSO) is a type of electronic test instrument that combines the capabilities of both a...
pyramid error
Pyramid error in optics refers to an aberration in the shape of an optical surface, particularly in the context of mirrors....
spatial light interference microscopy
Spatial light interference microscopy (SLIM) is an optical microscopy technique that belongs to the category of quantitative...
sterance
Flux per unit solid angle and per unit area measured normal to the direction of propagation of the flux.
definition test object
A chart, either printed on paper or prepared photographically on glass plates or film, that consists of 3-bar resolution...
image quality
A measure of the closeness with which an optical image is capable of resembling the original object. The factors that affect...
intensity-modulated sensor
A type of fiber optic sensor that responds to a change in the intensity of received light caused by the displacement or...
damped least squares
An organizational method used in optical design computer programs. The technique produces one number (merit function) to...
flux density
Flux per unit area measured normal to the direction of propagation of the flux.
whiteness measurement
The use of whiteness formulas to replace visual assessment.
color aging test
A test used to measure the degree of fading of different colored materials, especially those involving organic dyes, which...
digital signal processing
Digital signal processing (DSP) refers to the manipulation and analysis of signals, which are representations of physical...
microphotometer
An instrument capable of measuring the transmitted or reflected luminance from a very small area seen under a microscope....
transmission efficiency
Measure of the amount of light that is transmitted, relative to the amount lost by absorption or reflection.
detector array
A detector array refers to a collection of individual detector elements arranged in a two-dimensional grid or matrix format....
gas filter correlation
A technique for measuring the concentration of any gases. Identical infrared beams are alternately chopped, one passing...
thermal resistance
In a laser, a measure of the device's ability to dissipate internally generated heat.
absorbing wedge
A doped or absorbing transparent medium cut or molded into a wedge in order to measure the real and imaginary components of...
spectral integral density
With respect to color photography, the measurement, at a given wavelength, of the way the color film modulates the radiant...
Rogovsky coil
Conductor element for use in integrated electro-optic systems that measures current flowing through it.
photon drag detector
An infrared detector in which radiation passes through a doped germanium crystal, creating a voltage drop that can be...
opacimeter
An instrument for measuring opacity.
photoacoustic spectroscopy
A method for obtaining the optical absorption spectra of solids, semisolids, liquids and gases. PAS is inherently...
critical fusion frequency
The fusion frequency of flicker that is needed just to produce complete fusion and to assure the visual sensation of...
luminance range
An objective measure of an object's brightness that is derived from the ratio of the luminance of its lightest section to...
scatterometry
A measurement technique used for the rapid quantitative evaluation of surface quality based on the detection and analysis of...
wavelength meter
A device that measures the wavelength of an electromagnetic wave.
optometer
An instrument designed to measure the refractive power and range of accommodation of the eye. See ophthalmic instruments.
projection moire topography
A contour mapping technique that involves projection of a grating onto an object to produce a shadow grating that is...
hyperspectral resolution
Hyperspectral resolution refers to the level of detail or granularity in the spectral information captured by a...
double diffuse density
Measurement derived from calculation when incident flux of a negative is entirely diffuse and all radiation transmissions...
photoemissive tube photometer
A photometer that uses a photoemissive tube to detect and measure light. See photoelectric photometry.
transverse offset method
A technique used to measure the mode-field diameter of an optical fiber by scanning one fiber past another at a distance of...
filar eyepiece
A measuring eyepiece with a screw-micrometer-driven crosshair used to measure the size of the image.
luminous flux
Descriptive of the radiant power of visible light modified by the eye response. It is the measure of the flow of visible...
swept-source laser
A swept-source laser, also known as a wavelength-swept laser, is a type of laser that rapidly and continuously changes its...
spectrometer
A kind of spectrograph in which some form of detector, other than a photographic film, is used to measure the distribution...
colorimeter
A colorimeter is a device used to measure and quantify the color characteristics of an object or a light source. It provides...
prismograph
A graphical device used to measure prism power.
photoconductive antenna
Photoconductive antenna (PCA) is a semiconductor element that generates or detects high-frequency electromagnetic signals....
photon burst detection of fluorescence
A type of laser spectroscopy used to measure short-lived isotopes by observing sudden bursts of fluorescence resulting from...
triclinic
With respect to a crystal, having three unequal axes intersecting at angles, only two of which can be equal and only one of...
photoelectric colorimetry
The measurement and analysis of color using a photoelectric instrument having three filters with broad spectrum bands.
minimum separable
The least space between two parallel lines that can be discriminated as a gap to the human eye. It is measured in terms of...
luminous energy
A measure of the time-integrated amount of flux. It has units of lumen-seconds and might be used to describe such things as...
tracking accuracy
Measurement of a translation stage's deviation from absolute straightness, that is, its angular motion in both the vertical...
proximity probe
A noncontact sensor used in the remote measurement of position, speed or other variables of moving parts.
spectrometric oil analysis
An analytical technique used to determine, identify and localize impending malfunctions. It is based upon quantitative and...
dye-polymer optical disc
A type of erasable data storage device that uses a medium deposited on the disc in two layers, each dyed to absorb a...
spectroscopy
Spectroscopy is a technique used in the study of interactions between matter and electromagnetic radiation. It involves...
mensuration
The process or act of measuring the geometric properties of an object or image.
internal standard
A material that is present or added to a sample undergoing spectroscopic analysis, to serve as an intensity reference for...
digital camera
A digital camera is a device that captures and records still images or video in digital format. Unlike traditional film...
x-ray streak camera
A diagnostic instrument that uses a photocathode design to see a broad range of x-ray radiation by streaking the...
microchannel plate
A microchannel plate (MCP) is a specialized electron multiplier device used in various applications such as particle...

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