Photonics Dictionary

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...

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

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

A microcircuit whose passive components consist of a ceramic-metal combination deposited on a given substrate by screening and firing processes.

A type of recording material, usually a photodielectric polymer, offering in situ development mechanisms because of its density storage capabilities, high diffraction efficiencies and excellent noise...

A two-dimensional hologram.

A concept used for purposes of preliminary calculations and analysis. In theory it is a lens whose axial thickness is zero.

A circuit whose passive components are deposited on a given substrate by sputtering or vacuum processes.

Thin-film coatings are layers of material applied to the surface of an object or substrate, typically to modify its optical, electrical, or mechanical properties. These coatings are composed of thin...

Thin-film deposition equipment refers to machinery and tools used in the process of depositing thin layers of material onto a substrate surface. This technique is commonly employed in various...

Calculations of lens aberrations whereby the first two terms of the series expansion are the only ones employed. This theory provides the six aberrations of Seidel.

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

Thomson scattering is a phenomenon in physics where electromagnetic radiation, such as light, is scattered by charged particles. It is named after the British physicist J.J. Thomson, who first...

A laser having a material, such as ruby, that has an energy state structure of three levels: the ground state (1) wherein excitation applied to the material raises ions in the material into the...

Three-photon microscopy is an advanced imaging technique that belongs to the family of multi-photon microscopy methods. It is used in biological and medical research to capture high-resolution images...

1. In visual perception, the minimum value of stimulus that can be perceived on the average. 2. In optical detection systems, that signal level at which the probability of detection is 50 percent.

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

The minimum driving current corresponding to lasing threshold at a specified temperature. (Ith).

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.

1. Voltage at which a PN junction begins to pass a current. 2. In a solid-state lamp, the voltage at which light is first emitted.

The greatest wavelength of radiation for a specified surface for the emission of electrons.

The process of defining a specific intensity level for determining which of two values will be assigned to each pixel in binary processing. If the pixel's brightness is above the threshold level, it...

An arc discharge tube having a grid that is used to start the discharge through an atmosphere of inert gas or vapor at low pressure.

A method of scanning in which a frame transfer device produces a continuous video image of a moving object by means of a stack of linear arrays aligned with and synchronized to the movement of the...

The time domain is a concept used in signal processing and analysis to describe signals in terms of their behavior over time. In the time domain, signals are represented as functions of time, showing...