Photonics Dictionary

A filter designed to improve contrast in an imaging system. For visual and black and white photosystems, a yellow filter is used.

One area of image enhancement, accomplished by spatial filtering schemes, that usually involves attenuation of phase changes in the complex amplitude over a limited region of the Fourier spectrum of...

That contrast level that exists between two areas whose difference in brightness is just perceivable.

1. In optics, the bending of light rays toward each other, as by a convex or positive lens. 2. Turning in the eyes to view a near object. 3. In a television picture tube, the crossing of the...

A type of photoelectric proximity mode sensing incorporating a lens system to focus the light from the emitter in a small, concentrated spot at a specific point in front of the sensor. Also referred...

The curved boundary between two optical media of different refractive indices, which causes convergence.

In a pumped laser system, the ratio of output energy to pump energy.

Convex is an adjective used to describe a surface or shape that curves outward, bulges, or has a rounded and outwardly extending appearance. In the context of geometry or optics, a convex shape is...

An image-enhancement technique in which each pixel is subjected to a mathematical operation that groups it with its nearest neighbors and calculates its value accordingly.

The group of adjacent pixels on which the convolution process is carried out.

A powerful and flexible machine-learning approach that can be used in machine vision to help solve difficult problems. Inspired by biological processes, multiple layers of neurons process portions of...

A telephoto lens form noted for its lack of distortion.

The simplest lens in which all primary aberrations may be corrected. It consists of two positive crown elements on either side of, and spaced away from, a negative flint element.

A fluid used to decrease the temperature rise produced by friction or other causes.

An infrared detector that achieves a specified sensitivity through the application of certain cryogenic temperatures.

The coupled pairs of electrons that carry supercurrents through the body of a superconductor, relative to a coherent macroscopic wave function with the superconductor.

An instrument used to measure the coordinates of a point on an object such as a photographic plate.

The combination of two or more different small-molecule monomers into a polymer.

An early type of nonvacuum photocell consisting of a layer of copper oxide on a metallic substrate, with a thin transparent layer of a conductor over the oxide. When light falls on the cell, a small...

A camera mounted on an optical bench with an easel to hold the material to be copied. Magnification can be varied over a wide range by sliding the camera and easel.

A threadlike inclusion within a blank of optical glass. Rarely found in quality optical materials.

The light-conducting portion of an optical fiber, defined by the region of high refractive index.

A semispherical or conical lens created directly on the core of an optical fiber to focus light from a laser into the fiber core.

A mass-relieving method whereby material is removed through the sides of a reflector in a direction parallel to the surface. A method of cutting a cylindrical piece of material from a large piece.

The transparent front layer of the eye. Light entering the eye is refracted (converged) by the outer surface of the cornea.

The mechanical modification of the shape of the cornea to correct a vision defect.

A corner cube, also known as a corner reflector or retroreflector prism, is a type of optical device used to reflect light or electromagnetic waves back towards their source with minimal deviation in...

The removal of a slight overlap that may be found on a blank or pressing.

A compound prism formed by cementing together two 30° prisms, one of right-handed and one of left-handed quartz. It has good ultraviolet-transmitting qualities and no double refraction.

A prism formed by dividing a Nicol prism in a plane parallel to the path of vibration of the transmitted light and taking out the wedge-shaped piece. After the pieces are rejoined, the planes of...

A telescope in which a mask occults the solar disk, generating an artificial eclipse and allowing observation and recording of the sun's corona.

Solar regions characterized by low density and open magnetic fields where high-speed solar wind streams originate. Originally believed to be "M'' regions, coronal holes are the precursors of the...

A compound lens, the dimensions and materials of which have been so chosen that the lens is appreciably free of aberrations.

In rangefinders and height finders, a rotatable or sliding wedge-shaped element used to divert the line of sight precisely to correct errors in the optical system.

An optical wedge of very small angles that admits light while sealing out moisture and dirt and that may be rotated to compensate for the errors in the entire system. Correction windows are sometimes...

An optical element designed to correct each zone of a reflector or refractor for spherical aberration.

Temperature of the blackbody having chromaticity nearest to that of the test source on a specified chromaticity diagram.

A technique for removing thermal noise and drift from focal plane assemblies by sampling the system output between views of scene elements and then subtracting the resulting value from the subsequent...

Bohr's formulation that every new theoretical principle must correspond to the salient classical predecessor. The principle imposes mathematical limits on theoretical discovery and implies, for...

Translucent collector developed to compensate for the partial blocking of a flat surface's collection angle that normally occurs in spectroradiometry. The device samples radiant flux according to the...