PI Physik Instrumente - Semiconductor Applications 5/24 ROS LB

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74 terms

Photonics Dictionary

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luminance

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.

brightness -> luminance

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.

luminance factor

Ratio of the luminance of a specimen to that of a perfect reflecting or transmitting diffuser identically illuminated.

luminance meter

A type of photometer calibrated in luminance units (candles per square unit, or lamberts). In photography an exposure meter contains a luminance meter to record the average luminance of a scene.

luminance range

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.

absolute luminance threshold

The minimum value of luminance for vision. The value may vary with age as well as dark adaption period. (Measured range approximately log luminance -3 through 2.) About 10 -2 ml at the fovea, 10 -5...

additivity of luminance

The luminance of a mixture of lights is the sum of the luminances of the component lights in the mixture.

apparent luminance

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

background luminance

The intensity of the light in the scene behind an object being viewed.

constant luminance encoder

A device used in broadcast CCD cameras to improve definition in heavily saturated colors by band-limiting the color difference signals after gamma correction.

illuminance

Luminous flux incident per unit area of a surface; luminous incidence. (The use of the term "illumination" for this quantity conflicts with its more general meaning.)

uniform luminance area

In a cathode-ray tube, the region wherein a display on the tube keeps 70 percent or more of its luminance at the center of the viewing area.

apostilb

A unit of luminance equal to 1/p candela per square meter.

atmospheric attenuation

The reduction in luminance of a light beam due to absorption and scattering as it passes through the atmosphere.

binocular threshold

The absolute luminance threshold for detection by the two eyes.

brightness meter

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...

cascade method

A heterochromatic photometric process using successive comparison of similar chromaticities and the calculation of relative luminances of unlike chromaticities as the product of ratios of luminances...

cathode dark space

The area of low-level luminance lying between the cathode and the negative glow in a glow-discharge, cold-cathode tube.

chrominance

The difference between any color and a reference color having equal luminance and a specified chromaticity.

colorimetric purity

Ratio, to the luminance of a test color, of the luminance of the spectrum color that matches the test color when mixed with white light.

comb filter

A filter that passes a series of wavelength regions that are at equal distances from one another, such that its output resembles the teeth of a comb. In video transmission, a comb filter is used to...

composite video

A type of video signal in which the luminance and chrominance portions of the signal, or the luma and chroma, have been combined according to standards such as NTSC, PAL or SECAM.

contrast

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...

cosine emission law -> Lambert's cosine law

Flux per unit solid angle leaving a surface in any direction is proportional to the cosine of the angle between that direction and the normal to the surface. A material that obeys Lambert's cosine...

cosine law of illumination

Law relating the illuminance (or irradiance) of a surface to the cosine of the angle, q, between the normal to the surface and the direction of the incident wave.

Craik-O'Brien effect

Observed when alterations in the luminous sterance at the contour of an object create the illusion of the outer zones appearing darker than the inner regions, despite the consistent luminance of the...

dark discharge

In a gas, an electrical discharge that has no luminance.

display primaries -> receiver primaries

Also known as display primaries. Colors formed by a television receiver that are of constant chromaticity and variable luminance, and that, mixed in certain proportions, form other colors. Red, green...

equiluminous colors

Colors differing only in chromaticity but not in luminance.

etendue

A product of the area of a light beam (normal to its direction of propagation) and the solid angle that the beam includes; flux per unit radiance or luminance. Alternative terms: geometric extent,...

Fechner ratio

The differential luminance threshold divided by the luminance.

Ferry-Porter law

The law stating that the critical fusion frequency is approximately proportional to the logarithm of the luminance and the area.

flicker photometry

Heterochromatic photometry that depends on the elimination of chromatic flicker at a lower frequency than luminance flicker.

footcandle

Unit of illuminance equal to one lumen per square foot. (fc).

footlambert

Unit of luminance equal to 1/p candela per square foot. (fl).

foveal vision -> photopic vision

Vision by means of retinal cones; color vision. Relatively high levels of luminance are required for photopic vision.

geometric extent -> etendue

A product of the area of a light beam (normal to its direction of propagation) and the solid angle that the beam includes; flux per unit radiance or luminance. Alternative terms: geometric extent,...

heterochromatic photometry

Light measurement by comparison of the luminances of unlike chromaticities.

high-gain screen

A screen with a reflected or transmitted light beam that is confined to a much smaller bundle than was received by the screen, thereby resulting in a higher luminance.

highlight

The portion of a reproduced image having the greatest luminance.

illumination

The general term for the application of light to a subject. It should not be used in place of the specific quantity illuminance.

image 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...

inverse square law

The law stating that the illuminance (or irradiance) from a point source varies as the inverse square of the distance between the source and the receiver.

Lambert's cosine law

Flux per unit solid angle leaving a surface in any direction is proportional to the cosine of the angle between that direction and the normal to the surface. A material that obeys Lambert's cosine...

lambert

A unit of luminance equal to 1/p candela per square centimeter. (l).

lambertian surface

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...

Liebmann effect

The visual perception of contrasting forms is more difficult if the forms have the same luminance but different chromaticities, than if the forms have the same chromaticity but different luminances.

luma

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,...

lux

SI unit of luminous incidence or illuminance, equal to 1 lumen per square meter.

mesopic vision

Vision at intermediate levels of luminance between photopic and scotopic vision, where both retinal cones and retinal rods are stimulated for visual use in dim, low light situations. See also...

Photonics Dictionary