Photonics Dictionary: I

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

A type of refractometer designed to measure the refractive indices of liquids. A section of the instrument is immersed into the sample being measured.

Fluorescence formed when atoms of one element collide with excited atoms of another.

The ratio of the velocity of light in a vacuum to the velocity of light in a refractive material for a given wavelength.

A device used to accelerate the electrons in a free-electron laser by supplying electrical energy to the electron beam through a series of transformers.

In a microscope, a space reserved to accommodate an optical filter or polarizer.

An infrared source, set in a stationary position, that is used as a reference in certain navigational systems.

That angle found between a pair of adjacent faces of a crystal.

Describing the standard television method of raster scanning in which the image is the product of two fields, each of which is a series of successively scanned lines separated by the equivalent of...

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...

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

Pertaining to the possession of photoelectric characteristics as a result of the properties of the true crystal and not of foreign materials.

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.)

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

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.

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

An electro-optic system using, in general form, an evacuated glass envelope with a semitransparent photocathode at one end and a luminescent screen at the other for the amplification of an optical...

Often referred to as the geometric center of a given image or image plane, the centroid of an image is a fixed point located at the intersection of all of the hyperplanes of symmetry within that...

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...

Also referred to as image visibility, the contrast of an image is the variation in the intensity of an image formed by an optical system, where the image pixels are defined on a gray scale scheme of...

An electron tube that employs electromagnetic radiation to produce a visual replica of an image produced on its cathode. Electrons ejected from the cathode by the incident radiation are accelerated...

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...

An electron tube that is used as a camera tube for a television system. When the picture to be transmitted is focused on a photosensitive surface, electrons are emitted from each section of the...

The distance from the last surface of a lens system to the image. For a thin lens system, this distance is equivalent to the distance from the rear nodal point of a lens to the image.

A semiconductor platelet laser that emits a coherent image by means of plane optical pumping over the platelet surface, and that uses laser threshold characteristics to produce a pronounced threshold...

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 system of elements which rotates the optical image with respect to the optical axis by a factor of pi radians.

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 hologram in which the image of an object, or the object itself, is located near the hologram recording plane, for optimum image reconstruction. Because the images are close to the hologram plane,...

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...

An eyepiece having a special prism arrangement linked to a micrometer screw to allow reading of the angular relations between the two prism segments to be varied. When the prism faces are parallel,...

A modified form of an image-retaining panel that can be used in subdued daylight. This is achieved by adding a layer of zinc oxide between the panel's phosphor layer and its rear electrode. The zinc...

Any arrangement of a bundle of optical fibers that alters the shape of the image. For example, by systematic regulation of the spacing of the fibers from the entrance end to the exit end, a...

A camera system in which the image formed on the fluorescent screen of an image converter tube in the system is recorded by photography or direct contact printing from the face of the tube.

The science of producing, recording, storing, transmitting and displaying visual images by any system (photographic, video, facsimile, etc.) in any form.

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...

Term synonymous with refractive index liquid, but related more to tank or chamber immersion of crystals, fibers, lenses, photoelastic models, etc.