Photonics Dictionary

Autofluorescence refers to the natural emission of fluorescence exhibited by certain biological structures or molecules when exposed to light. Unlike fluorescence that results from the application of...

A means of adjusting the sharpness of an image automatically, with a sensor for estimating distance or contrast and a drive mechanism to adjust the lens. Active systems generate a light source to...

A CCD sensor that provides feedback to the motion control system for a telescope, allowing the telescope to follow a particular object or section of sky automatically.

The luminescence of a substance that is produced by energy within it (e.g., radioactive material).

Automated optical inspection (AOI) is a technology used in manufacturing processes, particularly in electronics, to automatically inspect and detect defects or anomalies in products. AOI systems use...

Automatic current control (ACC) refers to a system or mechanism designed to regulate and maintain a desired level of electric current in a circuit or device without manual intervention. This control...

A method of producing an essentially constant output signal from an electronic circuit despite variations in the strength of the input signal.

A system for automatic industrial process control or measurement, consisting of an optical module for image acquisition, a segmentation processor to isolate the image from its background, and an...

In fiber optics, the use of a detector to study the range of refractive indices achieved at various wavelengths. This information is calculated electronically to establish the divergence between...

A direct reading spectrograph having a photomultiplier assembly in place of a photographic plate. The output from the photomultiplier assembly is received by a microammeter or a pen recorder.

Any photographic medium that, when chemically developed, produces an exact photographic reproduction of the original.

The photographic recording of the distribution and location of radioactive substances found in a specimen. The record formed is the autoradiograph.

A microscope to which a beamsplitter and illuminated reticle have been added to measure the radius of curvature of a spherical surface by locating both surface and center and calculating the distance...

A low-power telescope placed at the eyepiece of an optical system to increase overall magnification. Most often used to evaluate image quality.

A device that utilizes avalanche multiplication of photocurrent by means of hole-electrons created by absorbed photons. When the device's reverse-bias voltage nears breakdown level, the hole-electron...

In a pulsed laser, the pulse energy in joules times the repetition rate in hertz.

A receiver for optical communications systems consisting of a symmetric binary, pulse-code-modulated transmitter, a log-normal channel and an array of independent photocounting detectors that yield...

Eye blink or head movement in response to bright light. Aversion responses such as blinking are sufficient protection from less hazardous lasers, including Class 2 lasers. An eye blink can occur, at...

In astronomy, the method of deliberately viewing objects with peripheral vision to take advantage of the eye's greater sensitivity to faint light a few degrees from the optical center.

The number of molecules in one gram mole of a substance, numerically approximated by 6.02 x 1023.

A bundle of rays that originates from an object point on the optical axis of a lens system.

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

In gradient index optics, a gradient profile in which the refractive index varies along the direction of light propagation, or optical axis. Axial gradient lenses can be used to correct spherical...

A method of designing lasers whereby the laser rod is cut into elliptical discs and cooled by running water over the disc surfaces. The cooling circuit decreases the radial temperature gradients in...

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

The propagation constant evaluated along the axis of a waveguide, that is, in the direction of transmission. Also called axial propagation wave number.

A vapor-phase oxidation process for fabricating graded-index optical fibers. It differs from outside vapor phase deposition in that the preform is developed radially rather than longitudinally. An...

An axicon is a type of optical component characterized by its conical shape and its ability to transform a collimated Gaussian beam of light into a ring-shaped beam with a gradually increasing...

A straight line, real or imaginary, passing through a body and indicating its center; a line so positioned that various portions of an object are located symmetrically in relation to the line. See...

Azadioxatriangulenium is a type of organic compound with a unique triangular molecular structure. It is often abbreviated as ADOTA. This compound belongs to the class of polycyclic aromatic...

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...

Azimuthal polarization refers to a specific polarization state of light where the electric field vector of the electromagnetic wave points along the azimuthal direction (around the propagation axis)....

Azobenzene is a chemical compound consisting of two phenyl rings linked by a N=N double bond. It is well-known for its ability to undergo reversible photoisomerization, meaning it can switch between...

Calculates the exponential growth of the least stable spatial frequency in a laser beam, and is the numerical equivalent of the nonlinear phase shift along the laser system's optical axis.

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...

The rule stating that positive uniaxial crystals have greater absorption with respect to the extraordinary component of light, whereas negative crystals have greater absorption for the ordinary...

A device containing two opposed quartz wedges of equal angle, one wedge being movable along its length by a micrometer screw. The wedges are cut so that their fast directions are along, and...

The principle stating that two diffraction screens, one being exactly the negative of the other, will form the same diffraction patterns.

A Babinet compensator that contains the controlled motion of one prism with respect to the other. This idea was introduced by Jamin.

A channel for communication with the source in an otherwise unidirectional network, such as a channel that provides interactive features in a cable television network.

The distance from the final optic within a system to the rear image point of the system. See focal length.

A CCD that has been reduced in thickness by etching so that light passes through the back layers of the CCD. This type of CCD typically has higher sensitivity, especially to blue light, and higher...

Back-side illumination (BSI) is a technology used in imaging sensors, particularly in digital cameras, where the light is allowed to enter the sensor from the back side, opposite to where the...