Photonics Dictionary: G

The term gradient-index profile refers to a specific type of refractive index distribution within an optical material. In optics, the refractive index of a material describes how much the speed of...

Gram-negative bacteria are a group of bacteria that possess a cell envelope composed of a thin layer of peptidoglycan surrounded by an outer membrane. This outer membrane contains lipopolysaccharides...

Gram-positive bacteria are a group of bacteria that have a thick cell wall composed primarily of a substance called peptidoglycan. This thick peptidoglycan layer retains a stain called crystal violet...

An electron tube having two electron guns, one on each side of the storage medium, to encode the information onto the medium, and to read and simultaneously erase the electrostatic encoding.

Graphene is a two-dimensional allotrope of carbon consisting of a single layer of carbon atoms arranged in a hexagonal lattice pattern. It is the basic building block of other carbon-based materials...

Formula used in convection study to express the ratio of buoyant force to viscous force.

The British term for reticle.

A grating beamsplitter is an optical device that utilizes the principles of diffraction to split a beam of light into multiple beams, often redirecting them at specific angles. It is based on the...

A specific, right-angle prism having a transmission grating replicated on its hypotenuse face and used in applications requiring a system that can produce in-line viewing for one wavelength.

A spectroscope having a diffraction grating for the resolution of light of various wavelengths.

The substrate upon which a diffraction grating will be ruled. It must be dimensionally stable, and the surface must be polished to an accurate flat or spherical form as required by the grating. The...

The effect of a powerful gravitational field on light traveling through the field. This effect is detectable in astronomical observations when light from a distant source passes a massive object...

Postulated by Einstein in his theory of relativity. They are waves traveling at the speed of light and exerting force on matter in their path. They are produced by changes in the distribution of...

In image processing, machine vision and television, discrete brightness values quantized for a group of pixels. They can range from white, through various shades of gray, to black.

Transparencies that represent progressive steps in the amount of transmitted radiation for administering predetermined amounts of radiation to a radiation-sensitive substance. The steps are...

Image enhancement operations that involve altering gray-scale values. For instance, brightness sliding involves adding or subtracting an identical brightness value to or from each pixel in an image;...

A porous ceramic substance that is ground to a given optical form and on which a polished plate of glass is sagged by heat application. It is capable of transmitting in a partial vacuum. The glass...

Familiar term for CD/I disc. The CD/I standard also is known as the green standard.

A form of a stereoscopic microscope having paired objectives, prisms and eyepieces, and invented by H. Greenough.

A GRIN (gradient index) lens is a type of optical lens that utilizes a gradient in refractive index across its volume rather than having a uniform refractive index like conventional lenses. This...

Machinery used to grind and finish a component, such as a lens or prism, to a desired precision. Usually such machines carry a cup-shaped or flat tool (lap) into close contact with the part. An...

A tool of cast iron or another suitable medium used with a slurry of silicon carbide, aluminum oxide or emery for grinding optical surfaces.

A method of determining the abrasion resistance of very hard materials by passing a weighted wiper blade across them in a sand-water slurry for a specified number of times.

For a given mode propagating in a medium of refractive index n, the velocity of light in vacuum c, divided by the group velocity of the mode. For a plane wave of wavelength l, it is related to the...

For a particular mode, the reciprocal of the rate of change of the phase constant with respect to angular frequency.

A factor derived by equating the incident light on the subject to the required incident light for suitable photography. The lamp-subject-distance then is multiplied by the aperture and solved in...

A wave in which energy is focused near a boundary separating materials having different properties. Propagation of the wave is in a direction parallel to the boundary.

A camera accurately aligned to a weapons system to provide a photographic record of system performance.