Photonics Dictionary

Broadband radiation emitted by a laser that does not transmit through the optical element. It can be removed by filtering.

In image processing, methods of reducing image defects that result from false data. Techniques include sampling, linear intensity, filtering a high-resolution image to produce a low-resolution image,...

A confocal resonator, also known as a confocal cavity or confocal laser resonator, is a type of optical resonator configuration used in laser systems. The term confocal in this context refers to the...

Technique that uses high-pass filtering to reduce the local average to zero for all regions of the picture and then applies a gain factor equal to the reciprocal of the local standard deviation to...

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...

A sudden, brief increase in current or voltage in a circuit that can damage sensitive components and instruments. Preventive measures include slow-starter circuits, filtering and static control.

Digital signal processing (DSP) refers to the manipulation and analysis of signals, which are representations of physical quantities that vary over time or space. In the context of DSP, these signals...

In image processing, any operation that strengthens information about the edges of objects displayed. Three types of spatial filtering are used: shift and difference, gradient and Laplacian.

An etalon is an optical device that consists of two parallel reflecting surfaces separated by a precise and known distance. It operates based on the principle of optical interference and is used to...

A function used in a convolution filtering operation. The image to be filtered is convolved with the filtering kernel to obtain the enhanced image.

A holographic grating is a type of diffraction grating that is produced using holographic recording techniques. It consists of a periodic structure of alternating transparent and opaque regions,...

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

A lock-in amplifier is a specialized electronic instrument used to extract and measure small signals embedded in noise or interference. It is particularly useful in fields such as spectroscopy,...

Machine vision, also known as computer vision or computer sight, refers to the technology that enables machines, typically computers, to interpret and understand visual information from the world,...

In image processing, a method of local smoothing by replacing each pixel with the median gray level of neighboring pixels.

Metasurfaces are two-dimensional arrays of subwavelength-scale artificial structures, often referred to as meta-atoms or meta-elements, arranged in a specific pattern to manipulate the propagation of...

A computer-generated, phase-and-amplitude, off-axis hologram made by a multi-exposure technique that uses three computer generated transmission masks. Each mask controls one fixed-phase component of...

Derivative of the half-tone screen process involving the fabrication of a binary pulse-width modulated copy of the continuous-level input using a halftone screen and spatial-filtering single...

A filtering device that detects what is new in a scene of interest. Often compared to that of a temporal high pass filter, these filters will remove elements that appear repeatedly throughout an...

An optical assembly refers to a collection of optical components that are carefully arranged and aligned to perform a specific function within an optical system. These components may include lenses,...

An optical filter is a device that selectively transmits or blocks specific wavelengths, or colors, of light. Optical filters are used to control the spectral content of light in various...

The optical Fourier transform is a mathematical operation applied to optical signals that involves transforming a spatial domain representation of an image into its corresponding frequency domain...

A photonic integrated circuit (PIC) is a compact and integrated device that incorporates multiple photonic components and functions on a single chip, similar to the way electronic integrated circuits...

In digital image processing, a subcategory of frame processing that treats each pixel in terms of its relationship to adjacent pixels. Perceived brightness trends facilitate spatial filtering.

A filtering method that restores a blurred image by setting its power spectrum equal to that of the original image.

Raster scanning is a technique used in imaging and scanning systems to systematically capture and process information from a two-dimensional area or surface. It involves moving a sensor or scanning...

In image processing, the enhancement of an image by increasing or decreasing its spatial frequencies.

A laser capable of generating light pulses that last only a few femtoseconds. This can be achieved by nonlinear filtering to increase bandwidth and compress the pulse or by passive mode-locking or...

Volume Bragg gratings (VBGs) are specialized optical elements that consist of periodic variations in refractive index throughout the volume of a transparent material, typically a photosensitive glass...

A method that embraces the classical approach to image restoration and attempts to minimize the mean square difference between the original ungraded signal and the restoration.

The removal of the zero-order component of the Fourier spectrum distribution of an object with a small, opaque absorber or reflector in the Fourier plane, to produce images that appear bright on a...