Photonics Dictionary: T

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...

See honeycomb table; indexing table.

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

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

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...

In television, a lateral displacement of the lines from their normal position due to the instability of a synchronizing circuit. Visually, it appears as though parts of the images had been torn away.

There are three types of telecentric lenses: -Image-space telecentric lenses are those in which the aperture stop is located at the front focus, resulting in the chief rays being parallel to the...

A compound lens so constructed that its overall length is equal to or less than its effective focal length.

The ratio between the focal length of a lens having a longer focal length than that of the standard lens used with a camera, and the focal length of the standard lens. It is used to provide an...

In a telephoto lens, the ratio of the overall length to the focal length of the lens. It is generally about 0.8 to 0.9 in magnitude.

1. A method of photographing distant objects with a lens of long focal length. 2. The reproduction of photographs over a distance by means of electricity.

An instrument used to measure the luminance (brightness) of a distant object. The object is viewed through a small telescope, and a mirror in the focal plane reflects an internal illuminated surface...

The principles and techniques involved in the use of telephotometers to measure atmospheric extinction.

The use of head-mounted displays and body-operated remote actuators to control distant machinery. Provides a virtual environment for humans to control devices, robots, etc., in a hostile real...

A method of taking radiographs at a distance from the object being photographed to decrease distortion.

A telescope lens is a primary optical component of a telescope system that gathers and focuses light to form an image. It is typically a curved, transparent piece of glass or other optical material...

The base used to hold an astronomical telescope. It may be either altazimuth, with horizontal and vertical axes of rotation, or equatorial, with one axis parallel to the Earth's axis of rotation and...

The material favored for study of interaction of high-acoustic intensities with free carriers. Tellurium is the semiconductor with the largest piezoelectric constants. Tellurium oxide is the material...

Teloscopy, while not a commonly used term, could be understood in the context of principles related to telescopes and their applications in observation and measurement. If we interpret teloscopy as...

A coating having pigments that change color when exposed to heat. This effect has been widely used to monitor hot spots in mechanical parts.

A technique used to suppress extreme noise amplification during digital image reconstruction that relies on smoothing and differentiation of the data by simplified least squared procedures.

A terahertz spectrometer is a scientific instrument used to measure and analyze the properties of materials in the terahertz frequency range, typically spanning from about 0.1 to 10 terahertz (THz),...

Terahertz (THz) refers to a unit of frequency in the electromagnetic spectrum, denoting waves with frequencies between 0.1 and 10 terahertz. One terahertz is equivalent to one trillion hertz, or...

An electron tube that has an anode, a cathode, a control electrode and another electrode (usually a screen grid).

A photoconductive cell that uses thallium oxysulfide as the light-sensitive medium.

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....

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...

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 (TIMs) are substances or compounds used to enhance the thermal conductivity between two surfaces in contact. These materials are primarily employed in electronic devices,...

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...

A diode electron tube that contains a heated cathode.

The emission of free electrons by a rise in temperature of the cathode alone.

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...

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...

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...

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 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...

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...