Photonics Dictionary: P

An array of lines in the infrared region of the emission spectrum of atomic hydrogen. Their wave numbers are expressed by the equation: where represents the wave number in the reciprocal centimeters,...

A Peltier cooler, also known as a thermoelectric cooler (TEC) or thermoelectric module, is a solid-state device that uses the Peltier effect to transfer heat between two electrical junctions. It can...

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...

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...

Photobleaching is a phenomenon in which the fluorescence of a fluorophore (a fluorescent molecule or dye) is permanently reduced or eliminated upon prolonged exposure to light. This process occurs...

Photodynamic inactivation (PDI) is a therapeutic approach that utilizes the combination of light, a photosensitizer, and molecular oxygen to induce cell death or inactivate microorganisms. This...

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

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.

Also known as electronic photometer. A photometer with a photocell, phototransistor or phototube for measuring the intensity of light.

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

A prism used in a photometer for the adjacent comparison of separate luminance.

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 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,...

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...

Plasmonics is a field of science and technology that focuses on the interaction between electromagnetic radiation and free electrons in a metal or semiconductor at the nanoscale. Specifically,...

A device attached to the end of an alignment telescope that detects and calculates a plane mirror's rotation axis that is perpendicular to the line of sight. The device is adaptable for evaluation of...

A polygonal mirror, also known as a multifaceted mirror or facet mirror, is a type of optical component used in various laser systems, optical scanners, and imaging devices. It consists of a flat or...

Positioning generally refers to the determination or identification of the location or placement of an object, person, or entity in a specific space or relative to a reference point. The term is used...

A device designed to measure electromotive force or electrical difference potential.

Laws that predict the maximum power output as a function of tube diameter for a hydrogen cyanide laser of a given discharge length and cavity losses, all other parameters being optimized.

An accurately produced hole of any size and shape that is used as a masking device in an optical system. Pinhole apertures of accurate diameters often are produced by laser beam penetration or by...

A prism is a geometric optical element with flat, polished surfaces that refract light. It is typically a solid, transparent object with at least two flat surfaces that are inclined relative to each...

An instrument for measuring the diameter of the human eye pupil.

An instrument for measuring the intensity of solar radiation.