Photonics Dictionary: T

Optical aberration such that image magnification varies with ray distance from the optical axis in a radial distortion.

A telescope that produces an erect image. Erection is achieved either by a lens (for a long instrument) or a prism (for a compact instrument). Very small terrestrial telescopes of low power may be of...

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...

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...

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.

In a laser, a measure of the device's ability to dissipate internally generated heat.

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...

An adhesive whose viscosity decreases as the temperature is increased to a limit. Canada balsam, resin and pitch are examples of thermoplastic cements.

A material used in the jacket of fiber optic cables.

A type of holographic film widely used for industrial applications because it is inexpensive and erasable.

A display device having a thermoplastic film as the control layer medium. The film, moving from a playoff reel, is scanned by an electron gun and melted by an RF heating unit. Deformation of the film...

Two 30° prisms that are used to produce constant deviation when rotated by equal and opposite angles.

In visual perception, the smallest difference in illumination perceived on the average.

In laser damage testing, the exposure of many sites of a sample to different intensities of laser irradiation to discover the point at which the laser induces failure of the material.

A family of semiconductor switching devices of which the silicon-controlled rectifier and the triac are most commonly used. They are fabricated from four positive and negative alternating layers.

The amount of time needed for a detector signal or electronic circuit to reach 63 percent of its final value after a fixed incident power is first applied.

A controlled motion system that may use a telescope, camera or antenna to follow accurately a satellite, missile, vehicle or other device in response to radar, radio or computer signals.

An electronic device consisting of a semiconductor material, generally germanium or silicon, and used for rectification, amplification and switching. Its mode of operation utilizes transmission...

The element in a charge-coupled device that receives the charge packets transferred from the line of sensor sites and then delivers the image data to the device's output circuitry.

The distortion of an image formed by a cathode-ray tube, caused by unbalanced deflection voltages or deflection voltages that are not symmetrically aligned with the resultant anode potential.

Computation of tristimulus values by integrating or summing, over the visible wavelength region, the product of the relative spectral power of a CIE standard source, the reflectance of the object...

A device used to produce numerical integrations for colorimetry.

The values of the three standard or matching stimuli necessary to provide a match with the light under trial, in a specified trichromatic system.

An evacuated bulb containing a tungsten filament that is heated by passing an electric current through it. In domestic light bulbs the inside of the bulb is frosted to soften shadows. In projection...

A system that is complete and self-contained, needing no further additions to permit its operation.

A compound crystal having two or more crystals or crystal sections that, when regularly positioned, are in reverse position relative to the other sections. When viewed, these crystals appear to be...

Twisted intramolecular charge transfer (TICT) is a phenomenon observed in certain organic molecules containing electron-donor and electron-acceptor groups that are linked together within the same...

A form of liquid crystal widely used in displays, achieved by sandwiching a liquid crystal material between two substrates whose inside surfaces have been prepared with a special coating that aligns...

A set of samples used in the analysis of multielement thin films.

The equivalent f number of a fictitious lens that has a circular opening and 100 percent transmittance, which would give the same central illumination as the lens being considered: where...

An instrument designed to measure the rate of rotation of components, such as shafts.

The series of interference bands that appear in the spectrum when a specified glass plate is inserted into a spectroscope, from the side of the blue portion of the spectrum, so that the plate...

The law stating that the brightness of an object that is examined through a slotted disc, rotating over a critical frequency, is proportional to the angular aperture divided by the opaque sectors.

A waveguide having a characteristic that is altered continuously with the distance traveled, relative to the axis of its path.

1. The anode or anticathode of an x-ray tube that emits x-rays when bombarded by electrons. 2. The screen in a television imaging tube that is scanned by an electron beam to determine the...

Measurement estimated from the position of the image's centroid.

Angular tracking measurement estimated from the properly normalized image second-moment tensor.