Photonics Dictionary: A

Ablation applied to polymers and chemical solids. Process of material removal that minimizes edge damage but will not heat the surrounding portion of the sample.

Optical surface damage due to abrasive rubbing. Abrasion damage affects are less than the thickness of the optical coating layers. Surface investigation may be achieved by aluminization of the coated...

Powder used to produce a smooth optical surface through abrasive polishing. Compounds may produce a surface finish specified for each.

The present radiation level within a laser or electromagnetic radiation operating area.

Electromagnetic radiation present upon the open aperture of the source within an operating environment.

The intermolecular attraction between two surfaces, as between a substrate and a coating; it is an important factor in the durability of optical thin films.

An intermolecular substance that serves to hold materials together. Two types are used in the optical industry: one, which must be transparent and colorless, to cement lenses together; and a...

A television format with enhanced vertical resolution (400 lines as compared with the standard 330) that, unlike high-definition television, can operate on existing bandwidths and with existing...

Advanced driver assistance systems (ADAS) refers to a set of safety features and technologies designed to assist drivers in the driving process and enhance overall vehicle safety. These systems use...

A category of systems designed to communicate a photo taken from the air (e.g., aircraft, balloon, satellite) to a ground station. It can be done by direct television transmission of the photo, or by...

In image processing, the result of a sampling frequency that is too slow to preserve the spatial frequencies of the image. When detail has a frequency greater than half the sampling frequency, it...

Also known as all-glass fiber. A fiber with both a silica core and a silica cladding, regardless of the presence of a polymer overcoat or buffer.

Broadband radiation emitted by a laser that does not transmit through the optical element. It can be removed by filtering.

A signal in the form of continuously variable voltage or current.

A state in which an image is distorted by an optical system.

Dispersion that occurs when the medium's index of refraction decreases as the frequency of the propagating light increases. For a given medium, some wavelength ranges may produce anomalous dispersion...

In image processing, methods of reducing image defects that result from false data. Techniques include sampling, linear intensity, filtering a high-resolution image to produce a low-resolution image,...

A gas, such as oxygen, that improves the speed and efficiency of a laser cutter or welder when applied to the work surface, or an inert gas, such as argon, that helps to clean or shield the work...

A glass-ceramic material developed in Russia. Astrosital resembles Zerodur in terms of its ultralow thermal expansion. Other spellings include Astro-Sital and Astro-Sitall.

A mode of data transmission whereby each bit of information is generated separately, with some stop/start code to indicate the interval between bits.

Spectrometric analysis of the distinct and characteristic spectra of atoms of elements. The atoms are energized to emit radiant energy, which, when dispersed by a prism or diffraction grating,...

Any photographic medium that, when chemically developed, produces an exact photographic reproduction of the original.

Eye blink or head movement in response to bright light. Aversion responses such as blinking are sufficient protection from less hazardous lasers, including Class 2 lasers. An eye blink can occur, at...

In astronomy, the method of deliberately viewing objects with peripheral vision to take advantage of the eye's greater sensitivity to faint light a few degrees from the optical center.

A vapor-phase oxidation process for fabricating graded-index optical fibers. It differs from outside vapor phase deposition in that the preform is developed radially rather than longitudinally. An...

The measurement of heat energy as determined from absolute zero as the zero point on the scale. Increments are identical to the Celsius as well as Kelvin scales.

Component that is externally controlled via electronic or photon signal.

Any system of time measurement that is based on atomic resonances. The transition times between the hyperfine levels of cesium-133 have been accepted as the international standard.

In the SI system, prefix meaning 10-18.

A dispersion relation defined in order to value the reciprocal amount of dispersion. It is defined as the refractivity over the difference in index values of the shortest and longest visible...

A form of roof prism used to invert an image. The prism has faces cut normal to the optical axis; therefore, the prism may be placed within the optical path of a system and invert the image without...

Device which measures the index of refraction of glass as well as the dispersion over visible range.

A reflecting prism that inverts the image. The image is reflected four times internally and emitted laterally. The prism is cut normal to the optical axis while the image is internally reflected from...

Designed for the function of optical wavefront analysis. Shack-Hartmann camera aberration sensors use a lens array to image the wavefront to the CCD image plane. Live feedback may be applied through...

The alteration and reduction of color with the addition of white light. The perceived color shift that occurs as the monochromatic-white combination meets the eye and is interpreted by the brain. The...

Method of preserving the measured color value and color information as it is translated from differing devices. For example the output of a television display may be measured to have an identical...

The minimum value of luminance for vision. The value may vary with age as well as dark adaption period. (Measured range approximately log luminance -3 through 2.) About 10 -2 ml at the fovea, 10 -5...

The value of the distance of distinct vision, minimum focusing distance or near point, divided by the focal length of the lens. Magnification is produced when the optic is placed at its focal...

The natural log of the ratio of absorbed intensity over the total intensity which gives a constant value assuming a stable volume as well as energy. In optical physics the absorbance may be defined...

A doped or absorbing transparent medium cut or molded into a wedge in order to measure the real and imaginary components of the refractive index. An internally reflected Gaussian beam is interfered...

The ratio of energy or intensity absorbed by the medium (numerator) to the total incident energy.