Photonics Dictionary: H

A plotted relation between Log E (logarithm to base 10 of exposure in metercandle seconds) and density (logarithm to base 10 of opacity).

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...

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,...

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...

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.

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.

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

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 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...

A type of receiver that uses a local oscillator at a frequency deliberately offset from that of the incoming signal. It is less sensitive than a homodyne receiver, but easier to build because it...

In optical communications, the translation of optical signals into radio signals, lowering their frequency in detection from greater than 1014 Hz to less than 1010 Hz, so that further signal...

High harmonic generation (HHG) refers to a nonlinear optical process in which intense laser light interacts with a gaseous medium, typically an atom or a molecule, to produce harmonics of the...

Also known as HCS, an analytical method designed to collect statistically relevant amounts of quantitative data on many parallel cell populations or processes within cells through the combination of...

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....

Histochemical staining is a laboratory technique used in biology and medicine to visualize specific chemical components within biological tissues. This technique involves the application of various...

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...

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 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 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...

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 is an advanced imaging technique that combines holography and tomography to provide three-dimensional reconstructions of transparent or weakly scattering objects with high...

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 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 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 wave in the electromagnetic spectrum that has both electrical and magnetic field vectors in the direction of propagation.

A mode possessing components of both electrical and magnetic field vectors in the direction of propagation.

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...

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,"...

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....

That object distance at which a camera must be focused so that the far depth of field just extends to infinity. The near limit of the depth of field is then half the hyperfocal distance. For normal...

A hyperspectral imaging camera is a sophisticated imaging device capable of capturing and processing data across a wide range of wavelengths within the electromagnetic spectrum, typically from...

Hyperspectral resolution refers to the level of detail or granularity in the spectral information captured by a hyperspectral imaging system. In hyperspectral imaging, the electromagnetic spectrum is...

This term literally means "to lag behind.'' It is quite often used to describe the residual effect that remains after the primary effect has been removed, or the lag that exists between the...