Photonics Dictionary

A lens aberration that causes axial light rays having different wavelengths to focus at various points along the axis.

A paraxial light ray that extends from an object point on the optical axis.

1. In astronomy, the angle measured clockwise (eastward) in a horizontal plane, usually from north (true north, Y-north, grid north or magnetic north). 2. With relation to the plane-polarized light...

A cathode-ray display where information is represented visually as spots. Each spot's location is represented by a horizontal coordinate showing its bearing angle, and a vertical coordinate showing...

Backscatter refers to the phenomenon in which radiation or waves are scattered backward, opposite to the direction of the incident beam. This occurs when the incident radiation encounters a target or...

Fraction of light counter propagating collinear with the incident source. Processes considering backscattering are Raman, Brillouin, Rayleigh and Mie.

An opaque shielding device designed to reduce the effect of stray light on an optical system.

1. A bundle of light rays that may be parallel, converging or diverging. 2. A concentrated, unidirectional stream of particles. 3. A concentrated, unidirectional flow of electromagnetic waves.

1. A geometrical arrangement of two or more light beams for use in laser shows, object detection or other applications requiring arrayed multiple beams. 2. A mathematical 2 X 2 or 3 X 3 matrix for...

1. That action occurring when light passes through an optical interface at other than normal incidence, i.e., refraction. 2. The curving of a path of light that passes close by a massive object, due...

An instrument for the detection of the energy distribution of b-particles and secondary electrons.

An instrument designed to produce very hard x-rays by the acceleration of electrons in a varying magnetic field.

An imaging technique that labels all gray pixels as either black or white before processing begins.

Birefringence is an optical property of certain materials that causes them to exhibit different refractive indices for light of different polarizations. In other words, when light passes through a...

Characteristic of a reflector that reflects light along a different line or lines than that of the incident ray.

A ground-based navigation beacon that emits pulsed signals which are picked up by aircraft making an instrument (blind) approach in landing. The signal is transmitted to the aircraft's L-scan...

The loss of focus of a camera sensor because of excessive brightness, characterized by the enlargement of spot size and halation on a cathode-ray tube.

A blue diode laser is a type of semiconductor laser that emits light in the blue wavelength range of the electromagnetic spectrum, typically between 400 and 500 nanometers. Diode lasers are compact,...

A technique in which a beam of x-rays is directed against a crystal, the atoms of which, because of their lattice arrangement, reflect the ray in the same way as a series of plane surfaces. If the...

The scattering of x-rays by the regularly spaced atoms in a crystal. The angle at which the reflection occurs is known as the Bragg angle.

The law expressing the condition under which a crystal will reflect a beam of x-rays with the greatest amount of distinction or resolution and, at the same time, denoting the angle at which the...

A parallel plate of glass in such a position that the refracted and reflected rays of incident parallel light are mutually perpendicular. In this situation the reflected light is plane polarized, and...

The manual shifting bias control of a cathode-ray tube that determines both the average brightness and the contrast of a picture.

The degree to which a pixel in a digital image represents the analog brightness of the corresponding point in the original image. It is dependent largely on the number of bits devoted to representing...

A conical or cylindrical package of light rays emanating from a common point on the object.

A convex lens that brings an incident bundle of rays to a focus to produce intense heat at the focus.

A light-tight box that receives light from an object or scene and focuses it to form an image on a light-sensitive material or a detector. The camera generally contains a lens of variable aperture...

A shower of cosmic rays whereby a high-energy electron produces one or more photons that convert into electron pairs, the secondary electrons producing the same effects as the primary. As the process...

An instrument consisting of a high-voltage vacuum tube used to form hard x-rays or high-speed ion beams. By partitioning the tube into separate sections, the total voltage is divided.

A cathode-ray tube, driven by a computer, that receives impulses of information from the computer and displays it in a series of lines, circles, curves or other graphic forms to be viewed by the user.

A term used in data processing to describe a cathode-ray tube that displays graphic or character data.

A plane that lies at right angles to the tube axis that has the deflection center.

Envelopes for cathode-ray tubes are made by blowing glass in the same manner as light bulbs. They have a fairly flat end face to carry the phosphor material applied internally.

A fiber optic end plate constructed by drawing a bundle of parallel fibers embedded in glass and cutting it into thin slices. These slices are assembled in a plane and heated to produce a...

A high-quality, narrow-angle lens of high aperture designed for low magnification in the recording of cathode-ray tube images.

The luminous trace formed on the cathode-ray tube screen by the motion of the electron beam.

A vacuum tube with an electron gun at one end and a fluorescent screen at the other. Electrons emitted from a heated filament are accelerated by a series of annular anodes at progressively higher...

A surface that envelops a bundle of rays or bundle of normals to the wave surface. It may be observed as a hollow, luminous cusp in a turbid medium.

A CCD camera, or charge-coupled device camera, is a type of digital camera that utilizes a CCD image sensor to capture and record images. CCD cameras are widely used in various applications,...

A CCD image sensor, or charge-coupled device image sensor, is a type of electronic device used to convert optical images into electronic signals. It is a key component in digital cameras, camcorders,...