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Photonics Dictionary: H

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HJ
heterojunction
HMD
head-mounted display; helmet-mounted display
HMFG
heavy metal fluoride glass
HMS
helmet-mounted sight
hn
energy of a quantum of radiation
HNDT
holographic nondestructive testing
HNIL
high-noise-immunity logic
hodoscope -> conoscope
An optical instrument, generally a polarizing microscope, that is used to determine the interference figures and optical axis of a sample crystal. Also called a hodoscope.
HOE
holographic optical element
hole burning
The dip or gap in the profile of a laser beam's line width when it is both homogeneously and inhomogeneously broadened. When an inhomogeneously broadened spectral line is saturated by incident light,...
hollow waveguide
An infrared-transmitting optical fiber with a hollow core; it can be square, round or rectangular in cross section. Capable of carrying high laser power but subject to high bending losses.
holmium
A soft, malleable, stable rare-earth element. Holmium laser systems are used in surgical procedures involving the cutting and vaporizing of soft tissue, cartilage and calcific structures.
holmium laser
Holmium lasers are a type of medical laser that utilizes holmium-doped crystals as the gain medium. The term holmium laser is often associated with a specific type of laser used in urology for...
holocamera
A camera system used to form a high-precision hologram of the subject on a photographic plate. It contains a high-power pulsed laser as the illuminating source.
hologon
A multifaceted holographic disc that is rotated by a motor to deflect incident light to a scanning system's lens.
hologram
An interference pattern that is recorded on a high-resolution plate, the two interfering beams formed by a coherent beam from a laser and light scattered by an object. If after processing, the plate...
holographic camera
A holographic camera, also known as a holographic imaging system or holographic recorder, is a specialized device used to capture 3D holographic images of objects or scenes. Unlike conventional...
holographic cinematography
A technique used to create a series of interrelated holographic images that give an appearance of motion when projected in sequence. A flashing laser is used in both the recording and projecting of...
holographic crystal growth analysis
The study of crystal growth from the molten stage utilizing a holographic system wherein interferometric techniques record detailed and measurable elements of crystal microstructure. In this way, the...
holographic grating
A holographic grating is a type of diffraction grating that is produced using holographic recording techniques. It consists of a periodic structure of alternating transparent and opaque regions,...
holographic interferogram
The three-dimensional interference pattern of fringes that is recorded on a holographic plate to facilitate the study of a complex object.
holographic interferometry
The interferometric analysis of a complex object by utilizing the three-dimensional hologram. By causing a laser beam to diverge into two directions, one of which directly strikes a holographic...
holographic lens
A photographic recording of interference patterns between a plane wave and a spherical wave on a high-resolution photographic emulsion.
holographic matched filter
A specific type of hologram that will transmit a pure plane wave when the hologram is illuminated by the type of wave it is matched to.
holographic memory
The storage of data as bits in memory by holographic processes. The laser beam is divided into reference and object beams, and bit information is stored as a hologram.
holographic microscopy
The holographic recording of a microscopic specimen whereby magnification is achieved by alteration in a wavelength or radius of curvature between recording and reconstruction of the wavefront. With...
holographic nondestructive testing
The application of coherent wavefront techniques to the determination of the physical state of a system without appreciably altering that state.
holographic optical element
A component used to modify light rays by diffraction; the HOE is produced by recording the interference pattern of two laser beams and can be used in place of lenses or prisms where diffraction...
holographic particle velocimetry
A method of measuring flow velocity by seeding the flow with neutrally buoyant particles and using a pulsed laser to holographically record particle displacement during a short time period. An...
holographic tomography
Holographic tomography is an advanced imaging technique that combines holography and tomography to provide three-dimensional reconstructions of transparent or weakly scattering objects with high...
holography
Holography is a technique used to capture and reconstruct three-dimensional images using the principles of interference and diffraction of light. Unlike conventional photography, which records only...
hololens
A series of permanent holograms in dichromated gelatin formed by opening total page-composer apertures and setting a point source of light in each storage location. It performs much like a...
holomorphic
With respect to a crystal, the characteristic of possessing two ends symmetrical with each other.
homeotropic orientation
The perpendicular orientation of the molecular axes of the nematic molecules in a nematic crystal, relative to the electrode plates.
homing guidance system
A system of sensors and related instrumentation that allows a navigable object (usually a missile) to locate its destination by some distinguishing characteristics of that target, and then calculate...
homocentric
A term applied to rays that possess the same focal point, which may be infinity, thereby meaning that the rays are parallel.
homodyne receiver
A type of receiver utilizing a local oscillator phase-locked to the incoming signal.
homogeneous
That property of a substance that determines that all components of volume are the same in composition and optical properties.
homogeneous broadening
The broadening of a laser's line width in a way that affects every atom (or molecule), and thus the whole system, in the same manner. Examples are collision broadening, and natural or intrinsic...
homogeneous cladding
That part of the cladding wherein the refractive index is constant within a specified tolerance, as a function of radius.
homogeneous multilayer coating
A thin film of absorbing or nonabsorbing layers in which the absorption of radiation at any point is directly proportional to the electrical field intensity at that point.
homogeneous orientation
The parallel orientation of the molecular axes of the nematic molecules in a nematic crystal, relative to the electrode plates.
homogeneous x-rays
X-rays of one frequency or a narrow band of frequencies.
homojunction
A junction between semiconductors that differ in their doping level conductivities but not in their atomic or alloy compositions.
honeycomb table
An optical test table made up of two outer layers or "skins'' bonded to either side of a honeycomblike core, usually of aluminum or steel. It results in equal quality with greatly reduced weight...
horizon detector
An infrared device used in satellites and rockets to determine a heat horizon for the Earth at altitudes (above 200 miles) where the visible horizon cannot be discerned. The device scans the infrared...
horizontal blanking interval
In television, the period during which the electron beam is cut off while the raster returns from the right-hand side of the screen to the left.
horizontal chromatography
A type of paper chromatography that produces a chromatogram that is horizontal instead of vertical.
horizontal drive control
A device that controls the output of a television receiver's horizontal oscillator.
horizontal resolution
In television, the number of individual pixels that can be distinguished in a horizontal scanning line; also called horizontal definition.

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