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398 terms

Photonics Dictionary: T

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tessar lens
A lens similar to the Cooke triplet anastigmat, with the rear crown achromatized for improved coverage and definition. It is used in medium-speed cameras and enlargers.
test chart -> resolution target
A chart on paper or glass containing a series of sets of lines at progressively smaller spacing and used to ascertain the limiting number of lines per millimeter that an optical system is capable of...
test cube
A device used to detect elevation, pyramid and resolution errors in prisms and other components by bringing them into contact with the three highly polished, flat, perpendicular surfaces that form...
test glass
A transparent block shaped accurately to reverse curvatures of the components it is used to test. By contacting an accurately finished negative lens shape with a newly made positive, the conformity...
test pattern -> pattern
A device that determines the lens shape in the cutting or edging phase of fabrication. It also is used to denote the arrangement of markings on a reticle.
tetartohedral crystal
The section of crystal symmetry having only one-quarter of the greatest number of faces permitted by the crystal system of which the section is a member.
tetragonal
With respect to crystals, having three mutually rectangular axes, only two of which are equal.
tetrode
An electron tube that has an anode, a cathode, a control electrode and another electrode (usually a screen grid).
texel
A contraction for "texture element." A base unit used in computer graphics that defines the surface of three-dimensional objects. Texels are obtained from texture memory and represent color to be...
TF/TA
terrain following/terrain avoidance
TFD
time and frequency dissemination
TFEL
thin-film electroluminescent
TFF
thin-film filter
TFM
transverse field modulator
TFR
tightly folded resonator
TFT
thin-film transistor
TGG
terbium gallium garnet
TGS
triglycine sulfate
thallofide cell
A photoconductive cell that uses thallium oxysulfide as the light-sensitive medium.
thematic mapper
An instrument used to record infrared images of large areas. The recorded data are used to produce maps in false color indicating particular themes such as vegetation, cloud cover, temperature...
theodolite
A precise telescope set on a pair of rotation axes, the horizontal and vertical axes equipped with two divided circles. One circle measures horizontal angles and the other measures vertical angles....
thermal blooming
The effect that characterizes an intense laser beam that is passed through an absorbing medium, causing the absorbed energy to produce density changes that can alter the intensity distribution of the...
thermal detector -> infrared detector
An infrared detector is a device that is used to detect and measure infrared radiation, which lies beyond the visible spectrum of light. These detectors are utilized in various applications,...
thermal dissociation
A technique for detecting free radicals by their electronic spectra. The material to be studied is placed in a temperature-controlled furnace through which radiation is propagated onto a...
thermal imaging
The process of producing a visible two-dimensional image of a scene that is dependent on differences in thermal or infrared radiation from the scene reaching the aperture of the imaging device.
thermal-infrared camera
A thermal-infrared camera, often referred to simply as a thermal camera, is a type of imaging device that detects infrared radiation emitted by objects due to their temperature. Unlike traditional...
thermal interface materials
Thermal interface materials (TIMs) are substances or compounds used to enhance the thermal conductivity between two surfaces in contact. These materials are primarily employed in electronic devices,...
thermal lensing
Distortion of an optical component as a result of heat, which can influence the divergence and the mode quality of a beam passing through the component.
thermal noise-limited operation
Operation in which the minimum detectable signal has its limits set by the thermal noise of the detector, the load resistance and the amplifier noise.
thermal photography -> thermal recording
A term referring to various processes for forming visible images outside of a camera to be photographed on ordinary film. Unlike regular infrared photography, thermal photography is an indirect...
thermal radiation
The emission of radiant energy in which the energy emitted originates in the thermal motion of the atoms or molecules of the source material.
thermal radiator
A source that emits radiant energy when its molecules or atoms are thermally excited.
thermal recording
A term referring to various processes for forming visible images outside of a camera to be photographed on ordinary film. Unlike regular infrared photography, thermal photography is an indirect...
thermal resistance
In a laser, a measure of the device's ability to dissipate internally generated heat.
thermionic diode
A diode electron tube that contains a heated cathode.
thermionic emission
The emission of free electrons by a rise in temperature of the cathode alone.
thermistor
A solid-state semiconducting structure (basically one of the bolometers) that changes electrical resistance with temperature. Materially, some kind of ceramic composition is used. A thermistor has...
thermochromic material
A material that changes color as it is heated or cooled.
thermocouple
A device composed of dissimilar metals that, when welded together, develop a small voltage dependent upon the relative temperature between the hotter and colder junctions. Banks of thermocouples...
thermodynamics
Examination of the processes whereby heat energy is converted into other forms of energy.
thermoelectric converter
An instrument that transforms heat energy into electrical energy.
thermoelectric cooling
A refrigeration method based on the Peltier effect. When an electric current passes through a thermocouple of two dissimilar metals joined in two places, heat is absorbed at the cold junction and...
thermoelectric solar cell
A solar cell that uses a thermoelectric converter, consisting of two sheets of metal with a semiconductor sandwiched between them, to generate electricity.
thermogram
Also known as analog thermogram. The resultant photograph, illustrating, in tones ranging from black to white, the spatial relationship of the infrared radiation temperatures of the different details...
thermograph
The instrument used to collect thermal radiation information on an object by scanning. It consists basically of a detector, a photoconductive element that converts incident radiation to an electrical...
thermography
Thermography is a technique that involves the use of an infrared imaging device, called a thermal camera or infrared camera, to detect and visualize the infrared radiation emitted by objects. This...
thermoluminescence
An alternative term for incandescence.
thermomagnetic imaging
The production of an image on a magnetic film that is exposed to infrared radiation and heated to a point above Curie temperature in regions of the image. The image is contacted with paramagnetic...
thermophotovoltaic
Thermophotovoltaic (TPV) refers to a technology that converts heat energy into electricity using the principles of thermophotovoltaics. In a thermophotovoltaic system, thermal radiation from a heat...
thermopile -> thermocouple
A device composed of dissimilar metals that, when welded together, develop a small voltage dependent upon the relative temperature between the hotter and colder junctions. Banks of thermocouples...

Photonics DictionaryT

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