Photonics Dictionary: P

A point cloud is a set of data points in a three-dimensional coordinate system, where each point represents a specific location in space. These points are typically obtained through various sensing...

1. With respect to angular subtense, a source of light, such as a star, that is very small. In a lab, a point source may be simulated by imaging a large source onto and through a pinhole, or by...

An established point on which the observer's eye is focused.

In digital image processing, a subcategory of frame processing that transforms pixel brightness and contrast through use of a mapping function. Point processing can be single-image (simple contrast...

A lamp, usually incandescent, that has a very compact filament, permitting a greater concentration of emitted light, aided by the use of small apertures and appropriate reflectors.

The point spread function (PSF) is a fundamental concept in imaging that describes the response of an imaging system to a point source or point object. It characterizes how a single point of light is...

A crystal diode whose rectifying activity is determined by the touching of the crystal to a finely pointed wire surrounded by a material of opposite type.

A device used in solar systems to direct mirror-reflected sunlight to a heat absorber and heat-driven engine, which turns a generator to produce electricity.

A method of producing magnified images by x-rays. The specimen is placed close to a point source of x-rays; the magnification achieved is the ratio of source-image to source-object distance....

A Huygenian eyepiece containing a pointer at its focal plane that is used -- when viewing an object through the eyepiece -- for specific designation.

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...

In a fiber optic guided missile, the point at which the optical fiber pays out from the bobbin on which it is wound.

The intersection of the principal plane and the optical axis of a lens.

A device used to project a small area of light on a screen for indication.

A telescope so manufactured that the image remains erect and the position of the eyepiece is unchanged as the line of sight is pointed in any horizontal direction.

A concave mirror that has the form of a paraboloid of revolution. The paraboloidal mirror may have only a portion of a paraboloidal surface through which the axis does not pass, and is known as an...

The angular difference in the direction of an object as seen from two points of observation. The angle subtended at the object by the base length of a rangefinder.

The optical phenomenon that causes relative motion between two objects when the eyepoint is moved laterally. When parallax appears in a telescope between the image and reticle, this indicates the...

Having coincident focal points.

Totally coherent radiation is produced by a purely monochromatic point source. In the real world the energy will have a limited bandwidth and the point source will subtend some angle resulting in...

Particle acceleration refers to the process by which charged particles, such as electrons or protons, gain kinetic energy and increase their velocity. This acceleration can occur in various natural...

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...

A wave of radiant energy in which each point of the wave is repeatedly displaced at equal time intervals.

The distortion that is the result of viewing a print from a point other than the center of perspective. The center of perspective is that viewpoint at which the angular subtenses of points in the...

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...

Phase distortion refers to a change in the phase relationships between different frequency components of a signal. In the context of signal processing, it occurs when the phase response of a system...

A phonon is a quantum of vibrational energy associated with the periodic motion of atoms or molecules in a crystalline lattice. In simpler terms, phonons are quanta of lattice vibrations in a solid...

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...

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...

The force that stimulates the emission of an electrical current when photovoltaic action creates a potential difference between two points.

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...

The photographic recording of the heat radiation emitted from various points on the object as corresponding density variations on fast infrared film.

Photonic crystals are artificial structures or materials designed to manipulate and control the flow of light in a manner analogous to how semiconductors control the flow of electrons. Photonic...

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...

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...

Phototoxicity refers to the harmful effects caused by exposure to light, particularly intense or ultraviolet (UV) light, on living cells or organisms. This phenomenon is often associated with the...

Photovoltaic (PV) refers to a technology that converts sunlight directly into electricity using semiconductors. The term "photovoltaic" is derived from the words "photo," meaning light, and...

A pixel, short for "picture element," is the smallest controllable element of a digital image or display. It is a fundamental unit that represents a single point in a raster image, which is a grid of...

Locus of points on a chromaticity diagram that includes the chromaticities of blackbody radiators.