Photonics Dictionary

In optics, an image is the reconstruction of light rays from a source or object when light from that source or object is passed through a system of optics and onto an image forming plane. Light rays...

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...

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...

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...

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,...

See digitizer; frame grabber.

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.

The digitization process by which an image is manipulated to increase the amount of information perceivable by the human eye.

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...

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...

A camera tube similar in design to the iconoscope. However, the image formed in the image iconoscope is projected on a photocathode that emits photoelectrons to be focused on a material, forming the...

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.

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...

Any form of lens, optical system (camera, telescope, microscope, etc.), or opto-electronics utilized for the purpose of producing an image of a given object.

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 plane in which an image is formed. A real image formed by a positive lens would be visible upon a screen located in this plane.

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 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...

The multiple storage of a single image.

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

A type of electroluminescent display that will record and maintain an irradiated image on its phosphor screen, provided a DC potential is applied to the screen. Used to record x-ray images, the...

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...

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

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...

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.

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 distance between the last vertex of a lens and the image.

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...

Photogrammetric compensation for incidental camera movement (which prevents attainment of true vertical photographs) whereby the imagery is copied in an oblique plane camera system.

That image remaining on the detector after the primary stimulus has been removed. In the visual system, the after-image commonly appears as the complementary color of the primary stimulus.