Photonics Dictionary: E

A measure of film speed sensitivity to light.

An instrument used to measure the light from a scene to be photographed and to indicate the camera lens and shutter settings required to expose the film correctly. The exposure time required in a...

The length of time during which the receiver is irradiated.

A radiation source that, unlike the point source, can be resolved by the naked eye into a geometrical image.

1. A strainmeter capable of measuring the change in the relationship between two reference points, provided that the points are separated by at least 20 to 30 m. 2. An instrument used to determine...

The ejection of electrons from the surface of a solid by the absorption of a sufficient amount of photons.

1. The near total absorption of plane-polarized light by a polarizer that has an axis perpendicular to the plane of polarization. 2. The decrease in the intensity of a diffracted beam resulting from...

A type of exposure meter that artificially reduces the light admitted in a sequence of known fractions until a value is reached that is equivalent to the proper exposure.

The ratio of the power of a plane-polarized beam that is transmitted through a polarizer placed in its path with its polarizing axis parallel to the beam's plane, as compared with the transmitted...

The lowest anode voltage at which a gas tube can sustain a discharge.

A cement used to reduce crosstalk in fiber optic bundles or plates.

A ray that has a nonisotropic speed in a doubly refracting crystal. It does not necessarily obey Snell's law upon refraction at the crystal surface.

Radiation that is emitted by a source outside the Earth and its atmosphere.

Extreme ultraviolet (EUV) refers to a specific range of electromagnetic radiation in the ultraviolet part of the spectrum. EUV radiation has wavelengths between 10 and 124 nanometers, which...

A photodetector composed of a semiconductor material whose responsive properties can be altered by the addition of impurities to the basic material. Copper- and mercury-doped germanium are both...

A type of optical fiber loss resulting from the misalignment of fibers in a splice or connector.

Synonym of extrinsic fiber loss.

Photoconductivity due to the addition of impurities or external causes.

The properties exhibited by a semiconductor as the result of its modification by imperfections and impurities in the crystal.

The organ of vision or light sensitivity.

The area in a 2-D or 3-D microdisplay viewer within which the eye can move and still see the entire image.

A shield of rubber, plastic or metal used to protect the eyes of the observer from stray light and wind, and to maintain the proper eye distance.

The lens of an eyepiece nearest the observer's eye.

A pattern on an oscilloscope display that consists of a string of shapes that resemble eyes. Because the pattern becomes more closed with increasing distortion and interference, an open eye diagram...

Also termed eye distance. The distance between the vertex of the last optical surface of a visual optical system and the system's exit pupil.

Instruments used by ophthalmologists and optometrists to study the eye. There are, for instance, the ophthalmoscope to observe and photograph the retina; the retinoscope and optometer to determine...

An optical device used to monitor movement of the human eye.

Wavelengths between 400 and 1400 nm (VIS to NIR) are focused onto the retina by the cornea. Because the retina is sensitive to light, these wavelengths can be damaging even at low energies. It is the...

Also known as ocular. The lens system used between the final real image in a visual optical system and eye. It acts as an image magnifier. Many types of eyepieces are known; e.g., the Huygens used in...