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621 terms

Photonics Dictionary

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EFL

effective focal length; equivalent focal length

acousto-optic deflection

The angular change of an incident beam due to vibrational induced refractive index changes within a crystal.

acousto-optic deflector

A system designed with a laser as a light source and a means for producing sound waves extending beyond 100 MHz to deflect light efficiently.

acousto-optic modulators and deflectors

An acousto-optic modulator (AOM) is a device that utilizes the interaction between sound waves and light waves to modulate or control the intensity, frequency, phase, or direction of laser beams. It...

angle of deflection

The angle through which a beam is deflected.

angle of reflection

The angle formed between the normal to a surface and the reflected ray. This angle lies in a common plane with the angle of incidence and is equal to it.

antireflection coating

An antireflection coating (AR coating) is a thin film or coating applied to optical surfaces, such as lenses or windows, to minimize unwanted reflections and increase the transmission of light...

asymptotic spectral reflectance

The unchanging nature of spectral reflectance as vegetational density increases to the point where additional increases in leaf area index or biomass do not cause a change in the spectral reflectance.

attenuated total reflectance spectroscopy

Attenuated total reflectance (ATR) spectroscopy is a technique used in analytical chemistry to obtain IR spectra of samples. It is particularly useful for analyzing solid and liquid samples without...

backreflection -> narcissus

A defect in infrared systems that appears as a dark circular area on a displayed image, caused by radiation reflecting into a detector. It can be reduced by low-reflective coatings or by altering the...

beam deflection tube

An electron-beam tube in which the current to an output electrode is regulated by the transverse motion of the tube's electron beam.

bidirectional reflectance distribution function

Unified notation for specification of reflectance in terms of both incident- and reflected-beam geometry; i.e., the ratio of reflected radiance in direction toward the viewer to the irradiance in...

bistatic reflectivity

Characteristic of a reflector that reflects light along a different line or lines than that of the incident ray.

cathode-ray tube deflection plane

A plane that lies at right angles to the tube axis that has the deflection center.

compensated reflector

A corner reflector that provides an increase in the range of angles over which it may be used.

corner-cube reflector -> corner cube

A corner cube, also known as a corner reflector or retroreflector prism, is a type of optical device used to reflect light or electromagnetic waves back towards their source with minimal deviation in...

deflection

Any bending of a wave of radiation away from its expected path, as, for example, by diffraction or by a magnetic field.

deflection circuit

The circuit that regulates an electron beam's deflection in a cathode-ray tube.

deflection focusing

The progressive defocusing of a cathode-ray tube display image that occurs when the deflected electron beam impinges on the cathode-ray tube screen at a slant.

deflection under static load

For an optical table, the amount of displacement that occurs when a heavy load is placed or moved on the surface. To measure deflection under static load, a 113-kg (250 lb) weight is placed in the...

deflection yoke

A metal coil or coils wrapped around the outside of the neck of a cathode-ray tube. Current passing through the coils produces a magnetic field, which can be used as an alternative to deflection...

diffuse reflectance

Ratio of diffusely reflected flux to incident flux.

diffuse reflectance spectroscopy

Diffuse reflectance spectroscopy (DRS) is a nondestructive analytical technique used to investigate the optical properties of materials, particularly in the field of spectroscopy. Unlike traditional...

diffuse reflection

Nonspecular reflection from a rough surface.

diffuse reflector

A reflecting surface that scatters radiation that is incident on it, thus producing diffuse reflection.

directional reflectance

Reflectance in a specified direction, for a specified direction of incident illumination.

distributed Bragg reflector

A device similar to distributed feedback lasers in construction and operation, but in which the period grating that produces feedback is removed from the gain region to simplify fabrication. The...

electro-optic deflection

The effect whereby a light beam is deflected by a birefringent prism when its polarization is changed by voltage applied to an electro-optical crystal through which the beam passes. The deflection of...

electroreflectance spectroscopy

A type of electromodulation that measures changes in spectral reflectance.

electrostatic deflection

The deflection of an electron beam by the action of an electrostatic field that has a component perpendicular to the direction of the beam.

Fresnel reflection

Fresnel reflection refers to the reflection of light at the interface between two different media with different refractive indices. This phenomenon was named after the French engineer and physicist...

Fresnel reflection loss

Reflection losses incurred at input and output of optical elements because of the difference in refractive index between glass and the immersion medium.

Fresnel reflection method

A method for measuring the index profile of an optical fiber by measuring the reflectance as a function of position on the end face.

frustrated total reflection

Light leakage at a total reflecting interface when another highly refractive medium is brought close to it.

graded reflectivity mirror

A mirror whose percent reflectance varies as a function of position on the mirror surface.

infrared reflector

An optical component coated to reflect infrared radiation. Gold, silver and aluminum are typical coating materials.

laser reflow soldering

Use of a laser to solder joints by melting the solder coatings on the mating components.

law of reflection

The law stating that the angle of reflection is equal to the angle of incidence, the incident ray, reflected ray and normal to the surface, all being located in the same plane.

maximum luminous reflectance

The greatest luminous reflectance possible for a specified chromaticity.

mixed reflection

The simultaneous occurrence of specular and diffuse reflection.

moiré deflectometry

An optical interference technique widely utilized as a method of nondestructive testing when determining the ray deflection and the modulation transfer function (MTF) of an optical system associated...

ocular accommodation reflex

The eye's involuntary reaction in the process of accommodation. This reflex is most dramatic in response to looking at a distant object after having previously been focused on a near object or vice...

optical continuous wave reflectometer

An instrument used to measure backscatter as well as optical return loss and reflectance within an optical fiber system by measuring the reflected light when a continuous wave is transmitted through...

optical grating reflectance evaluator

A device for measuring diffraction grating efficiency at any angle of incidence, consisting of a reflectometer wherein the detector rotates around the grating at a specific distance and is attached...

optical time-domain reflectometer

An optical time-domain reflectometer (OTDR) is a specialized instrument used in optical fiber communications to characterize and analyze the optical fibers' characteristics, including attenuation,...

optical time-domain reflectometry

A method for characterizing a fiber wherein an optical pulse is transmitted through the fiber, and the resulting light scattered and reflected to the input is measured (by an optical time-domain...

paraboloidal reflector -> paraboloidal mirror

A concave mirror that has the form of a paraboloid of revolution. The paraboloidal mirror may have only a portion of a paraboloidal surface through which the axis does not pass, and is known as an...

photoelectric reflectometer

A photoelectric photometer used to measure the reflectance of a surface.

photoreflectance

A noncontact form of electromodulation in which modulation of the electric field is caused by photo-excited electron-hole pairs from a pump source.

radially variable reflectivity optic

A reflecting optic whose reflectivity is a function of the radial distance from the optic axis; can be used to convert a Gaussian beam to one of uniform cross section.

Photonics Dictionary