Photonics Dictionary: H

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...

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.

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...

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...

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 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.

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

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....

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....

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...

The decrease in effect in developable density on a photographic plate formed by a second exposure to radiation having a longer wavelength, usually red or infrared.

A unit of frequency equivalent to one cycle per second.

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

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...

A superthin, highly reflective mirror.

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...

A system of Japanese origin that utilizes Fresnel lenses and a fiber optic network to transmit sunlight to otherwise inaccessible areas.

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...

A multifaceted holographic disc that is rotated by a motor to deflect incident light to a scanning system's lens.

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 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...

An ocular having two planoconvex lenses that are formed from similar glass and that are separated by a space equal to half the sum of their focal lengths. This eyepiece is free of lateral chromatic...

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 vision defect commonly referred to as farsightedness. Results when the image of a distant object is focused beyond the retina by the relaxed eye. The condition can be corrected by introducing a...

An eyepiece similar to the Huygenian eyepiece, but having an eye lens that is a cemented doublet and that provides more lateral color correction.

Hyperspectral imaging is an advanced imaging technique that captures and processes information from across the electromagnetic spectrum. Unlike traditional imaging systems that record only a few...

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...