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Photonics Dictionary: A

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A
absolute (kelvin degrees), absorption, acoustic, alpha particle, analog, anode, ampere, amplitude, area, atomic, atomic mass, Helmholtz free energy, mass number, nucleon number
a
atto-
A-O
acousto-optic
A/D
analog-to-digital
aA
attoampere
AA
analog to analog, anti-aliasing (AA optical filter e.g. low pass filter), approximate absolute temperature, atomic absorption
AAAS
American Association for the Advancement of Science
AART
Analog Adaptive Resonance Theory
AAS
American Astronomical Society
Abaxial ray
Ray oriented and assumed to propagate orthogonal to the optical axis
abaxial spherical aberration -> oblique spherical aberration
coma, fifth order aberration with on-axis focal point variation with incident off axis ray height position
Abbe condenser
A two-lens arrangement intended to image light into a microscope slide sample. The primary aberrations present are red and blue rings observed around the image focus.
Abbe constant
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...
Abbe illumination
Image of a uniform source through the sample of a microscope image system. Light from the sample plane is reimaged by the objective into the image plane.
Abbe prism
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...
Abbe refractometer
Device which measures the index of refraction of glass as well as the dispersion over visible range.
Abbe sine condition -> sine condition
First stated by Abbe, condition states that the ratio of input and output angles, from object point to image point, for two arbitrary rays must be equal.
Abbe-Porro prism
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...
aberration
A departure from ideal paraxial imaging behavior. The distortion of an optical field wavefront as it is propagated through the elements of an optical system. The field distortion is due to the...
aberration sensor (wavefront sensor)
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...
ABG
The ABg model or Harvey-Shack is a method of describing bidirectional scattering from isotropic or polished surfaces.
ablation -> laser ablation
Laser ablation is a process that involves the removal or erosion of material from a target surface using laser energy. This technique is widely used in various scientific, industrial, and medical...
ablation threshold
The minimum energy required to induce atomic and molecular separation or displacement due to incident intense laser irradiation.
ablative photodecomposition
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.
ablative wall flashlamp
A high-brightness, short-duration source in which low-pressure gas initiates the discharge to vaporize material from the tube wall, leading to a high-pressure discharge of ionized wall material.
Abney effect
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...
abrasion mark
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...
abrasive
Powder used to produce a smooth optical surface through abrasive polishing. Compounds may produce a surface finish specified for each.
abridged spectrophotometer
An instrument that uses optical filtration in order to measure the transmittance for a discrete range or specific number of wavelengths.
ABS
absorbance; acrylonitrile butadiene styrene
abs
absolute value
absolute colorimetric
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...
absolute luminance threshold
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...
absolute magnification
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...
absolute purity threshold
Least value of color value combinations which gives white light; minimum purity as determined to be white.
absolute refractive index
The ratio of the speed of light in a vacuum divided by the speed of light in the medium.
absolute temperature scale
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.
absolute white
A perfect diffuser that exists only as a concept, or a white with known spectral characteristics used as a reference in measuring absolute reflectance.
absorbance
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...
absorbing wedge
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...
absorptance
The ratio of energy or intensity absorbed by the medium (numerator) to the total incident energy.
absorption
The transfer of energy from an incident electromagnetic energy field with wavelength or frequency to an atomic or molecular medium.
absorption band
A group of frequencies or wavelengths on the electromagnetic spectrum which exhibits resonance or energy contributions near and in relation to a peak resonance wavelength.
absorption coefficient, absorption cross section
The transition cross section constant coefficient which defines the transition probability of absorption from ground to a higher level within a given atomic or molecular species. The transition...
absorption hologram
A hologram formed when the light of the illuminating beam is absorbed in correspondence with the recording exposure. In application, absorption holograms are intended for use in satellite...
absorption index
The absorption index represents the imaginary component of the complex index of refraction, and not the real component. The imaginary component may characterize the attenuation per unit length...
absorption lens
An optical lens manufactured to control the transmission of light over a specified wavelength range. Low absorption lenses are produced which are anti-reflection coated for UV, VIS and IR wavelengths...
absorption line
The wavelength or frequency corresponding to an absorption resonance with a given molecular or atomic species. The line spectrum will vary with the element as well as the molecular compound.
absorption meter
A measuring device that uses a light-sensitive cell or detector to determine the amount of light transmitted by a substance.
absorption peak
An absorption peak refers to a sharp increase or spike in the absorption of electromagnetic radiation at a particular wavelength or energy level. It is a distinctive feature in the absorption...

Photonics DictionaryA

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