Photonics Dictionary

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

An instrument for measuring the brightness (luminance) of a scene. It may be a spot meter, covering an area of a degree or less, or an averaging meter, covering a broad area of the scene. Brightness...

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 graduated range of stimuli perceived as having equivalent differences of 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...

A figure of merit corresponding to the amount of light seen by a viewer through binoculars. A higher number indicates a brighter image in low-light situations. The relative brightness value is...

A brightness, superimposed on the image of the retina, that decreases its contrast and that often results in decreased visibility.

A high-brightness, short-duration source in which low-pressure gas initiates the discharge to vaporize material from the tube wall, leading to a high-pressure discharge of ionized wall material.

The perceived brightness difference between light and dark areas on a target.

The perceived brightness of an object being viewed at some distance, especially through an optical instrument.

A digitized image consisting of just two brightness levels, as black and white, represented in memory as zeros and ones.

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 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,...

Chip-on-board (COB) lights refer to a type of LED lighting technology where multiple LED chips are directly mounted onto a substrate, typically a printed circuit board (PCB), without the need for...

The qualities of color associated with hue and saturation, but not brightness or lightness.

The sensations of hue and saturation, taken together, but not brightness or lightness.

The attribute of visual experience that can be described as having quantitatively specifiable dimensions of hue, saturation, and brightness or lightness. The visual experience, not including aspects...

Aspect of vision permitting the observer to distinguish among stimuli by their hue, saturation, and brightness or lightness.

Selection of specific brightness values or minimum threshold levels as contingencies for the display of digital data.

The apparent difference in brightness between light and dark areas of an image. For a light target against a dark background, contrast is computed as follows: where Lt is the luminance of the...

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

A formula indicating that, for an imaging lens system, the image brightness for off-axis points will fall off at a rate proportional to the cos4 of the off-axis field angle.

A method of resampling in which a 16-pixel neighborhood around a given pixel from the original image is used to calculate the final brightness value of that pixel in the corrected image.

A method of coding image data by storing in memory only differences in brightness of each pixel from that of its nearest horizontal neighbors: that is, it is the change in brightness rather than the...

A cathode-ray tube that increases the brightness or size of an image or forms a visible image from invisible radiation. The focal plane for the optical image is a large, light-sensitive, cold...

An instrument used to measure the light from a scene to be photographed and to indicate the camera lens and shutter settings required to expose the film correctly. The exposure time required in a...

A free-electron laser (FEL) is a type of laser that generates coherent, high-intensity electromagnetic radiation by using a beam of accelerated electrons as the lasing medium. Unlike traditional...

Also known as amplification. 1. The increase in a signal that is transmitted from one point to another through an amplifier. A material that exhibits gain rather than absorption, at certain...

Gallium nitride-based light-emitting diodes (GaN-based LEDs) are semiconductor devices that emit light when an electric current passes through them. These LEDs are constructed using gallium nitride...

A photometer used to measure sky brightness and polarization associated with zodiacal light, background starlight, F-region airglow and spacecraft corona.

In image processing, machine vision and television, discrete brightness values quantized for a group of pixels. They can range from white, through various shades of gray, to black.

Image enhancement operations that involve altering gray-scale values. For instance, brightness sliding involves adding or subtracting an identical brightness value to or from each pixel in an image;...

A halogen lamp, also known as a tungsten halogen, quartz-halogen, or quartz iodine lamp, is an incandescent lamp that uses a tungsten filament surrounded by a small amount of halogen gas, such as...

High dynamic range (HDR) refers to a technology that allows for a broader and more dynamic range of luminosity in visual content, such as images or videos. It is particularly associated with displays...

A special form of microscope that utilizes interference for observing and measuring the phase and optical thickness in completely transparent objects and specimen. The object is placed in one beam...

Indication of emission brightness with degree of emission from an optical source.

A perfectly diffusing surface; the intensity of the light emanating in a given direction from any small surface component is proportional to the cosine of the angle of the normal to the surface. The...

The laser output refers to the generated and emitted light produced by a laser system. This output is characterized by several key properties that distinguish lasers from other light sources. These...

The luminance portion of a composite video signal, i.e., the portion of the signal that corresponds to the brightness of the image apart from any color value, giving a monochrome, or gray scale,...

A lumen is a unit of measurement used to quantify the amount of luminous flux, which is the perceived power of light. In other words, the lumen measures the total amount of visible light emitted by a...

Luminous flux emitted from a surface per unit solid angle per unit of area, projected onto a plane normal to the direction of propagation. Also known as brightness and luminous sterance.

An objective measure of an object's brightness that is derived from the ratio of the luminance of its lightest section to that of its darkest section.

The illusory appearance of a light or dark band at a line of brightness contrast that enhances the edge between the two contrasting regions. This effect can create the appearance of graduated...

Machine vision lighting refers to the use of specific lighting techniques and equipment in the field of machine vision, which is a technology that enables machines to capture and interpret visual...

In astronomy, the relative brightness of a celestial body. Originally a scale from 1 to 6, where 1 represented the brightest and 6 the faintest visible night sky objects. This scale has been expanded...