Photonics Dictionary: H

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

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

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

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

A high-sensitivity camera is a type of camera designed to perform well in low light conditions, capturing clear and detailed images with minimal noise. These cameras typically feature advanced sensor...

A fish-eye lens designed to photograph cloud formations over the entire visible sky.

A photographic recording of interference patterns between a plane wave and a spherical wave on a high-resolution photographic emulsion.

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...

An analysis used for problems of wave propagation. The principle notes that each point of an advancing wavefront is the center of a new disturbance, the source of a new series of waves. It also notes...

A hypercentric lens refers to a lens system where the chief rays of light from an object are directed through the center of the lens aperture, ensuring that the entrance pupil is situated at...

With respect to photography, the process used to increase the effective speed of an emulsion between manufacture and exposure.

In chemistry, a halide refers to a chemical compound containing one or more halogen atoms bonded to another element. The halogens are a group of elements in the periodic table that includes fluorine...

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

With respect to waveguides, the continuous change in the direction of the axis of the wavelength, during which the axis is perpendicular to the direction of polarization.

A defect in the cleaved end face of an optical fiber, defined as multiple surface irregularities across the fiber surface. A less serious imperfection of the same nature is known as mist.

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

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

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

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

A communications system that can transmit in only a single direction at a time. See duplex.

Describing a surface that is coated with a film of metal of such thickness that it transmits about one-half of the incident light and reflects about one-half.

1. The value on either the leading or the trailing edge of a laser pulse at which the power is one-half of its maximum value. 2. The wavelength at which a filter is transmitting one-half of its peak...

A device for forming at least two adjacent areas of polarized light. The angle between the directions of vibration of the light waves in the two areas is generally small.

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

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

That voltage required across a Pockels, Kerr or other electro-optic light modulator to retard one polarization electrical vector by one-half a wavelength relative to the other. It corresponds to a...

A plate containing a uniform pattern of transparent holes in an opaque background, the clear area being nearly equal to the opaque area. Used in the printing process.

The gray-colored tones halfway between shadows and highlights in a reproduced image.

The development of a transverse electric field in a solid material when it carries an electric current and is placed in a magnetic field that is perpendicular to the current.

1. The faintly hued ring that is seen to surround a light source viewed through fog or light clouds. The size of scattering particles determines the size of the ring. 2. The ring surrounding a...

Any of the five elements astatine, chlorine, fluorine, bromine and iodine, grouped because their chemical properties are similar.

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

The line that divides the two half-images in a coincidence rangefinder. The two halves of the images formed by the two objectives of the instrument must be brought to a point where they coincide...

A device small enough to be held in a hand that uses a magnifying lens and a translucent back to permit the viewing of photographic transparencies.

Usually a dielectric coating on glass or plastic optics; a coating that is comparable in hardness to glass itself.

Text or images printed on paper or another tangible medium, as opposed to those viewed electronically on a cathode-ray-tube screen.

High-modulus elastic fibers that exhibit the following differences from conventional elastic fibers: Increasing temperature decreases recovery force (the fibers are enthalpic vs. conventionally...

The process of sealing laser components by means of frit seals, welding or bonding rather than using epoxy.

A type of x-ray that is capable of deep penetration; its wavelength is about 10-8 cm.

A type of optical fiber in which a silica core is surrounded by a hard polymer or similar material much stronger than the customary cladding material.

In the most general sense, the resistance of a solid surface to damage.

Harmonic generation refers to a nonlinear optical process in which incoming photons interact with a material and produce new photons at integer multiples of the frequency of the incoming photons....

An instrument designed to calculate the amplitude and phase of the different harmonic elements of a radiation wave utilizing a graph of the wave.

A direct-vision prism made in one piece that can be used only in parallel light.

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