Photonics Dictionary: I

Luminous flux incident per unit area of a surface; luminous incidence. (The use of the term "illumination" for this quantity conflicts with its more general meaning.)

Source of radiation defined or specified by its spectral power distribution.

Metamerism that occurs when the light source is changed.

Characteristic of a surface or object that has luminous flux incident upon it.

A magnifying lens fitted with a battery-operated lamp by which an object can be conveniently illuminated during observation.

A desklike apparatus with an opal glass surface illuminated from beneath by fluorescent tubes. It is equipped with roll holders for aerial films and a low-power microscope or some form of...

The general term for the application of light to a subject. It should not be used in place of the specific quantity illuminance.

Generally, the orientation of rays of light striking a surface.

The light formed by visible radiation that, in traveling from light source to object, undergoes one or more reflections. In microscopy, it is the light that falls on the object at right angles to the...

A device that combines electronic and optical techniques to form a monitored infrared signal between 1 and 14 µm. It contains an internal modulator to amplitude-modulate the output signal, an...

With reference to absorbance, absorptance, transmittance and the like, the processes occurring within a specimen between the entry and exit surfaces.

The effect in which photons are absorbed and excite the electrons; the electrons move from the valence band to the conduction band (intrinsic photoeffect), from the valence band to impurity levels or...

The creation of free electrons within a solid by the absorption of a sufficient amount of photons. The effect produces an increase in the conductivity of the solid.

A material that is present or added to a sample undergoing spectroscopic analysis, to serve as an intensity reference for spectral measurements.

A spectral line of an internal standard; used to compare radiant energy of the line being analyzed.

A nonoptical surface, within lenses and lens mounts, that contributes largely to flare by reflecting light into the image space. As a result, such surfaces, so located, are finished with a dull...

The ratio of the radiant power transmitted to the second surface of a medium to the corresponding radiant power that has just passed through the first surface. Internal transmittance does not denote...

A unit of measurement of luminous intensity based on a physical standard, a set of calibrated carbon filament lamps. The old candle unit was superseded by the new candle or candela.

Free of coma.

Also called calcite. A natural hexagonal crystal of calcium carbonate. It cleaves readily into rhomboids useful in the study of polarized light.

A system that transmits and receives identification codes to facilitate the discrimination between enemy and friend in a tactical situation.

In semiconductor physics and materials science, the term "III-V materials" refers to compounds composed of elements from group III and group V of the periodic table. More specifically, these...

A photometric instrument used to measure the illumination falling on a surface. It may be photoelectric or visual.

The apparent luminance of the image as seen through an optical system. This brightness of the image is determined by the brightness of the object, as well as the transmittance and etendue - or light...

A method used in imaging to detect subtle differences between two apparently similar pictures. It can be achieved by superimposing the negative of one photograph over a contact print of another, by...

A camera that uses an image converter tube in such a way that voltage waveforms applied to internal electrodes cause the original image to be switched on and off very rapidly, thus offering time...

A machine vision technique that compares a template of the desired image (the correlation kernel) with the actual camera image of an object and generates a new image (the correlation image) that...

In computer graphics, the coordinated two-dimensional or three-dimensional area of increased resolution where graphics entities may be defined. The screen represents a viewing window for this area,...

Complex devices, often involving a computer, in which a photograph is scanned by a point of light, the amplitude of the electrical signal being modified electronically before being recorded on...

An image intensifier, also known as an image intensification tube or image intensification device, is a specialized electronic device used to amplify low-light-level images to make them visible to...

A television camera tube that preceded the development of the vidicon tube and incorporated a method to separate reflected and scattered portions of the return beam so that only the scattered...

In optics, the term image jump refers to a displacement or shift in the apparent position of an image when a change occurs in the optical system. This phenomenon is often observed in certain types of...

The active control of various aspects (optical element position, airspace thickness, etc.) of an optical system that compensates for unwanted movement of the image that is caused by mechanical and...

A camera tube widely used in television broadcasting. It consists of three sections within a single vacuum envelope. 1. A photosensitive film sometimes called the photocathode. The scene to be...

Photon flow created by imaging of light into a detector array; IPD is the electrical signal used by the image processor in a laser radar angular tracking system.

A device embodying a microprocessor that converts an image to digital form and then further enhances the image to prepare it for computer or visual analysis.

A measure of the closeness with which an optical image is capable of resembling the original object. The factors that affect image quality are lens aberrations, diffraction, dirt and stray light...

Filtering procedures aimed at estimating the original image by removing the blurring and noise suppression that occur during image processing.

A method used to compare two pictures of the same subject taken at different times. See image comparison.

The processing of an image or portion of an image by transform coding and analysis. Fourier, Hadamand, Kronecker and Eigenvector transforms are applicable to image transformation.

Complex devices, often involving a computer, in which a photograph is scanned by a point of light, the amplitude of the electrical signal being modified electronically before being re-recorded on...

A radiation detector with its active medium mounted within a lens that focuses the radiation signal. The improvement in detector performance is a function of the indices of refraction of the lens...