Photonics Dictionary: P

Parallel scanning refers to a method of acquiring data or images simultaneously from multiple sources or in parallel, rather than sequentially scanning each source one after another. This approach is...

A whole-flow-field technique providing instantaneous velocity vector measurements in a cross-section of a flow that is seeded with micron-sized particles. CCD or CMOS cameras and laser light sheets...

Typically represented by the Greek letter μ, magnetic permeability is the measure of a material's ability to generate and sustain a magnetic field within itself when an external magnetic field is...

In optics and photonics, "phase" refers to a property of electromagnetic waves, such as light, that describes the position of a wave at a given point in time within its oscillation cycle. More...

With respect to a traveling plane wave at a known frequency, the space rate of decrease of phase of a field component in the direction of propagation, measured in radians per unit length.

A phase-modulated sensor is a type of sensor that uses modulation of the phase of a signal to measure changes in a physical quantity. In such sensors, variations in the phase of the signal are...

In biology, particularly genetics and evolutionary biology, the phenotype refers to the observable characteristics or traits of an organism, resulting from the interaction of its genetic makeup...

A method for remote measurement of the temperature of moving surfaces in harsh environments by using a laser to stimulate fluorescence of thermographic phosphors and then measuring the decay times by...

Periodic interruptions of a light beam incident on an absorbing medium that produce heat, expansion and acoustic wave generation. Since the amplitude of this wave is proportional to the absorbed...

A method for obtaining the optical absorption spectra of solids, semisolids, liquids and gases. PAS is inherently insensitive to reflection or scattering from the sample, analyzes opaque samples and...

An instrument used to detect and measure radiant energy by the formation of a chemical reaction.

A photographic recording instrument that measures deviation from the vertical of a drilled well or mine.

Photoconductive antenna (PCA) is a semiconductor element that generates or detects high-frequency electromagnetic signals. Compact PCAs based on gallium arsenide (GaAs) or indium gallium arsenide...

A photodetector, also known as a photosensor or photodiode, is a device that detects and converts light into an electrical signal. Photodetectors are widely used in various applications, ranging from...

A photodiode detector is a semiconductor device that converts light into an electrical current. It operates based on the principle of the photoelectric effect, where photons of light incident on the...

Photoelastic equipment and supplies refer to instruments and materials used in photoelasticity, a technique used to analyze stress distribution and behavior in materials. photoelastic equipment...

A system having a photoelectric detector for the measurement of three quantities related by linear combination to tristimulus values of a sample.

The measurement and analysis of color using a photoelectric instrument having three filters with broad spectrum bands.

A device used to count objects that pass a given point by allowing each object to obstruct a beam of light falling on a photocell. Slow counting rates can be recorded by a mechanical counter, but...

A device consisting of a microammeter, a photovoltaic cell and a battery. It is used for the measurement of scene brightness and the determination of correct exposure for photographic processes.

The use of photoelectric sensors to detect and measure the intensity of a light source. This application, as compared to human observation, results in higher speeds of operation, a greater...

An instrument used to measure the temperature of a source through the use of photoelectric cells to detect and measure the intensity of the light emitted by the source.

An instrument that uses a photocell to detect and measure the intensity of incident light.

A photoelectric photometer used to measure the reflectance of a surface.

A system that consists of a spectrophotometer with a photoelectric detector for measurement of radiant energy.

A photometer that uses a photoemissive tube to detect and measure light. See photoelectric photometry.

Photogrammetry is a technique used to obtain accurate three-dimensional measurements of objects and environments through the analysis of photographs or imagery. It involves extracting information...

A form of photometric measurement, often used with light sources that are transparent or fluctuating, in which a photographic plate is used to obtain a record of a source's relative intensities over...

The use of photographic recording equipment to measure radiant energy. With this procedure, many measurements of radiant energy can be recorded simultaneously and permanently.

A measure of the ability of a photographic system to record fine detail. Usually stated in terms of cycles per millimeter on the processed film.

The measurement of the responsivity of photographic media and of the relations between exposure and density of developed images.

A measure of the total light passed by a shutter during an exposure, compared with the light that could be passed by an idealized, infinitely fast shutter fully open for the same extreme time.

Pertaining to the measurement of the intensity of light.

Photocells of various kinds used to measure photometric quantities; i.e., intensity, luminance and illuminance. Meter readings are used to express illuminance and, by calibration, to measure...

Photometry is the branch of science that deals with the measurement of light, particularly in terms of its intensity and the way the human eye perceives it. It involves the quantification of visible...

A photomultiplier tube (PMT) is a highly sensitive vacuum tube that detects and amplifies low levels of light. It is widely used in various applications where high sensitivity, fast response times,...

A type of laser spectroscopy used to measure short-lived isotopes by observing sudden bursts of fluorescence resulting from repetitive excitation of an atom or molecule.

An infrared detector in which radiation passes through a doped germanium crystal, creating a voltage drop that can be measured in terms of incident intensity.

Photoplethysmography (PPG) is a non-invasive optical technique used to detect changes in blood volume in tissues. It measures variations in light absorption caused by the pulsatile nature of blood...

A camera equipped with angular scales in altitude and azimuth. The scale readings are imprinted on the film when an exposure is made. The exact point indicated by the scale readings is shown by...

A tachometer consisting of a light source, rotating perforated wheel and phototransistor to measure the rates of rotation of components. The phototransistor counts the flashes formed when the wheel,...

Piezoresistance is a phenomenon in materials science and physics where the electrical resistance of a material changes in response to applied mechanical stress or strain. This change in resistance...

A PIN photodiode is a type of photodetector or semiconductor device used to convert light signals into electrical signals. The name "PIN" is derived from the arrangement of the three semiconductor...

A vacuum gauge designed to measure very high degrees of vacuum by thermal conduction.

Pixel pitch refers to the distance between the centers of two adjacent pixels on a display screen or imaging sensor. It is typically measured in millimeters and is a crucial specification in...