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Photonics Dictionary: T

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telephoto lens
A compound lens so constructed that its overall length is equal to or less than its effective focal length.
telephoto magnification -> telephoto ratio
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.
telephoto power
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...
telephoto ratio
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.
telephotography
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.
telephotometer
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...
telephotometry
The principles and techniques involved in the use of telephotometers to measure atmospheric extinction.
telepresence
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...
teleradiography
A method of taking radiographs at a distance from the object being photographed to decrease distortion.
telescope
An afocal optical device made up of lenses or mirrors, usually with a magnification greater than unity, that renders distant objects more distinct, by enlarging their images on the retina.
telescope exit pupil
The image of the aperture stop, usually the objective lens, that is produced by the eye lens. When the exit pupil of the telescope coincides with the entrance pupil of the eye of the observer, the...
telescope lens
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...
telescope mount
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...
telescopic sight -> riflescope
A small erect-image telescope for use as a sighting device on a rifle. The chief requirement is a long eye relief to avoid damage to the eye due to recoil. The power may lie anywhere between 1 and...
televise
To transform a picture or image field into a television signal for transmission.
television aperture
The term that represents the size of one of the many small elements into which a television image is necessarily broken down for transmission.
television bandwidth
The span of frequencies within which a single channel of broadcast television must fall; in the US, it is 6 MHz.
television camera
A camera containing an electronic image sensor that converts the image to an electronic signal suitable for television applications.
television line number
The value equal to the raster height divided by the half-period of a periodic test pattern.
television microscope
A device designed to enlarge the image of a microscopic object by television process. It may be a flying spot scanner that is used to scan the microscope slide, or a camera tube-microscope...
television monitor
A television receiver that receives the signals generated by a television camera directly, or remotely through a radio signal. It may be used to continuously check image and sound reception; as a...
television projection
A television display system in which the television signal is converted to an image that is projected onto either a front or rear projection screen.
television signal
The combination of the audio and visual signals that are transmitted and received at the same time, correlating the scene and sound in a television picture.
television transmitter
An electronic device used to encode video and audio signals of a television camera into radio waves that are broadcast to remote receivers. The video and audio components are transmitted...
television waveform
The graph of the oscillating variations composing the wave of a video signal.
tellurium
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...
TEM
transmission electron microscope; transverse electromagnetic
TEM00 -> transverse mode
In the context of optics and lasers, a transverse mode refers to a specific spatial pattern of the electric field within the cross-section of a laser beam. These modes represent the different...
temperature decay method -> transient calorimetric technique
A method of measuring total hemispherical emissivity of the plane surface of a solid that consists of thermally isolating a specimen of the material inside a vacuum, preheating it slightly above the...
temperature-sensitive coating
A coating having pigments that change color when exposed to heat. This effect has been widely used to monitor hot spots in mechanical parts.
tempered glass
A glass that is heated, then chilled (usually by an air blast) to set up internal stresses so that the surfaces are under compression. This strengthens the glass, since glass breaks only in tension,...
temporal coherence
A characteristic of laser output, calculated by dividing the speed of light by the linewidth of the laser beam. The temporal coherence length of different lasers thus varies from a few centimeters to...
temporal disperser -> streak camera
A streak camera is a specialized instrument used to capture and analyze ultrafast phenomena, such as extremely short pulses of light or rapidly changing events. Unlike traditional cameras that...
temporal Fourier hologram
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.
temporal response
Characteristic of deflected light power defined as the quadratic invariant function of the video signal amplitude.
tensile loading -> proof stressing
A means of testing the strength of optical fibers to ensure reliability, by applying stress to the fiber so that any flaws generated during manufacturing or handling result in breakage of the fiber.
TEO
transferred electron oscillator
TEP
transparent electrophotographic
TER
total external reflectance
tera (T)
In the SI system, prefix meaning 1012. (T).
terahertz radiation
Electromagnetic radiation with frequencies between 300 GHz and 10 THz, and existing between regions of the electromagnetic spectrum that are typically classified as the far-infrared and microwave...
terahertz spectrometer
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
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...
term coherence
A synonym for spatial coherence. See spatially coherent radiation.
terminated crossbar
An optical matrix that does not require perfection in both states of the crosspoint, so that all the optical switches can be tap-off devices in which a fraction of the optical energy is transferred...
termination
The process of attaching a device to the end of a fiber cable to enable the beam to be transmitted farther, to pass to another device and to avoid reflection.
ternary
Made up of three components; for instance yttrium, aluminum and garnet (YAG).
ternary notation
Refers to a notation system using a base of 3 and the numerical characters 0, 1 and 2.
terrestrial telescope
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...
tesla
The magnetic flux density given by a magnetic flux of one weber per square meter. (T).

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