Photonics Dictionary: H

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

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

The process of subjecting glass to temperature cycling to produce physico-chemical reactions that alter its properties. Similar processes can be accomplished with a laser -- most commonly a CO2,...

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

A superthin, highly reflective mirror.

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,...

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

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.

The splitting of an element's spectral line as the result of the interactions between the electron spin and the spins of adjacent magnetic nuclei, or the presence of several isotopes in the sample...

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.

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

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.

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...

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...

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 optical system that superimposes a synthetic display providing navigational or weapon-aiming information on a pilot's or driver's field of view. The system includes a cathode-ray tube, collimating...

A series of flanges or other conducting surfaces, usually metal, attached to an electronic device to transmit and dissipate heat that might damage internal circuitry.

A small mass spectrometer used to find leaks in a vacuum system by detecting the presence of helium. Using a magnetic deflection device that is permanently tuned to helium, it is capable of detecting...

A helium-neon (HeNe) laser is a type of gas laser that emits visible red light at a wavelength of 632.8 nm. It operates based on the principle of stimulated emission of photons from excited helium...

Laboratory experiments that focus on demonstrating new capabilities of a certain technology or device, usually without consideration of industrial or commercial practicality.

Radiation consisting of more than a single wavelength in the visible region of the spectrum.

High dynamic range (HDR) refers to a technology that allows for a broader and more dynamic range of luminosity in visual content, such as images or videos. It is particularly associated with displays...

A screen with a reflected or transmitted light beam that is confined to a much smaller bundle than was received by the screen, thereby resulting in a higher luminance.

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-speed motion camera, also known as a high-speed camera or slow-motion camera, is a specialized imaging device designed to capture fast-moving events or phenomena at extremely high frame rates....

A camera designed to record at rates exceeding 50 fps. For frame rates up to about 500 fps, an ordinary pull-down mechanism can be used. From 500 to 1000 fps, the film must be moved continuously, the...

Histology is the branch of biology and medicine that involves the study of the microscopic structure of tissues and organs at the cellular and subcellular levels. It is a field that focuses on the...

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.

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.

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.

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...

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...

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...

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...

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...

In television, the number of individual pixels that can be distinguished in a horizontal scanning line; also called horizontal definition.

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

A method of manufacturing polycrystalline infrared-transmitting optical fiber by heating a single halide crystal billet and forcing it through a die.

A mirror with a coating that reflects infrared radiation and transmits visible light.

A hydrogel is a three-dimensional network of polymer chains that are hydrophilic, meaning they have a strong affinity for water. This network structure allows hydrogels to absorb and retain large...

Hydrophilic is a term used to describe substances or materials that have an affinity for water. The word hydrophilic comes from the Greek words "hydro," meaning water, and "philos," meaning loving or...

Hydrophobic is a term used to describe substances or materials that repel or do not readily interact with water. The word hydrophobic comes from the Greek words "hydro," meaning water, and "phobos,"...

In fiber optics, a material whose properties, usually of transmission, are distinctly affected by the absorption of water vapor.

Hyperchromic shift refers to an increase in the absorption of light, leading to a higher absorbance, often observed in certain chemical or biological substances upon undergoing a structural change....