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Definitions: I

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Iceland spar
Also called calcite. A natural hexagonal crystal of calcium carbonate. It cleaves readily into rhomboids useful in the study of polarized light.
iconometer
An instrument in which an object's image, produced by a lens of known focal length, is used to determine the object's distance from the instrument when its size is known, or the object's size if the...
iconoscope
A camera tube that employs a high-velocity electron beam to scan a photoemissive mosaic and to store electrical charge patterns.
ideal crystal
A crystal that is devoid of any mosaic structure and that can reflect x-rays, relative to the Darwin-Ewald-Prins law.
ideal filter
Any filter in which the range of frequencies within a chosen radius suffers no attenuation and the range of frequencies outside the radius is entirely attenuated.
ideal polarization rotator
A theoretical instrument conceived of as a box that receives a beam of radiation of any arbitrary polarization angle and produces a new beam, coaxial with the incident beam, having a specified new...
ideal radiator -> blackbody
An ideal body that completely absorbs all radiant energy striking it and, therefore, appears perfectly black at all wavelengths. The radiation emitted by such a body when heated is referred to as...
identification friend or foe system
A system that transmits and receives identification codes to facilitate the discrimination between enemy and friend in a tactical situation.
idiochromatic
Pertaining to the possession of photoelectric characteristics as a result of the properties of the true crystal and not of foreign materials.
III-V material
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...
illuminance
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.)
illuminant
Source of radiation defined or specified by its spectral power distribution.
illuminant metamerism
Metamerism that occurs when the light source is changed.
illuminated
Characteristic of a surface or object that has luminous flux incident upon it.
illuminated magnifier
A magnifying lens fitted with a battery-operated lamp by which an object can be conveniently illuminated during observation.
illuminated table
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...
illumination
The general term for the application of light to a subject. It should not be used in place of the specific quantity illuminance.
illumination distribution
Generally, the orientation of rays of light striking a surface.
illuminometer
A photometric instrument used to measure the illumination falling on a surface. It may be photoelectric or visual.
image
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...
image amplifier
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...
image brightness
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...
image centroid
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...
image comparison
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...
image compression -> data compression
A method of storing digital data using techniques that consume less memory space than basic methods do. See differential pulse code modulation; run end coding; run length coding.
image conjugate -> image distance
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.
image contrast
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...
image converter
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...
image converter high-speed camera
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...
image correlation
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...
image definition area
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,...
image digitizer
See digitizer; frame grabber.
image dissector tube
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...
image distance
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.
image enhancement
The digitization process by which an image is manipulated to increase the amount of information perceivable by the human eye.
image enhancement laser
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...
image enhancing equipment
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...
image feature extraction -> feature extraction
In image processing and machine vision, the process in which an initial measurement pattern or some subsequence of measurement patterns is transformed to a new pattern feature. In image pattern...
image iconoscope
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...
image intensifier
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...
image inverter
A system of elements which rotates the optical image with respect to the optical axis by a factor of pi radians.
image isocon
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...
image jump
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...
image motion compensation
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...
image optics
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.
image orthicon
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...
image photocounting distribution
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.
image plane
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.
image plane holography
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,...
image processor
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.

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