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Photonics Dictionary: P

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Prandtl number
Ratio of the molecular diffusion coefficients of momentum in terms of heat; used in convection studies.
PRC
photorefractive crystal
precision aperture
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...
preform
A glass structure from which an optical fiber waveguide may be drawn.
prefusing
A step before fusion splicing that involves cleaning the fiber end with low-current electricity.
prelasing
When uncontrolled laser energy leaks from a laser cavity prematurely, it causes serious damage to optical components and significant downtime for repair.
Prentice's rule
A method of determining prism power at any point on a lens. Prism power equals the product of the dioptric power and the distance, in centimeters, from the optical center.
presbyopia
A state in which the human eye has very little or no power of accommodation. A common and normal condition in the eyes of those age 50 and older.
pressing
A blank having basic surface curves attained by forming heat-softened glass that is pressed in a mold.
pressure broadening -> collision broadening
The broadening of spectral lines due to the collision of radiating particles with one another and the resulting interruption of the radiative process.
pressurization
Injecting a gas (usually nitrogen) with a very low moisture content into the body of an optical instrument to create a positive internal pressure. This prevents the entrance of moisture, which could...
PRF
pulse repetition frequency
PRI
pulse repetition interval
primary chromatic aberration
Also referred to as primary color, this is the classic chromatic aberration of a single element caused by the variation of index of refraction as a function of wavelength.
primary coating
In a waveguide, the material in intimate contact with the cladding surface, applied to preserve the integrity of that surface.
primary colors
A set of three colored lights which, when mixed, give the sensation of white light. The set used in color television, for example, is red, green, blue (RGB).
primary fluorescence
Fluorescence produced as a result of the intrinsic property of the material itself or the doping of the material with trace elements.
primary spectrum
The first-order spectrum formed by a diffraction grating.
principal axis
A straight line connecting the curvature centers of the refracting lens surfaces. In a mechanical sense, a line joining the centers of a lens as it is placed in a mount. The principal axis is the...
principal E-plane
The plane in which the axis of maximum radiation and the electric vector are contained.
principal focus -> focal point
That point on the optical axis of a lens, to which an incident bundle of parallel light rays will converge.
principal plane
In a lens or lens system, that surface at which the projections of an entering and exiting ray intersect. Also known as the equivalent refracting surface, the principal plane is most often not...
principal point
The intersection of the principal plane and the optical axis of a lens.
principal point of focus -> focal point
That point on the optical axis of a lens, to which an incident bundle of parallel light rays will converge.
principal ray
The ray of an oblique pencil beam that passes through the center of the pupils. It is the effective axis of the oblique beam. Also called the chief ray.
principal section
A plane passing through a crystal that has the optic axis of the crystal and the light ray under consideration.
principle of least time -> Fermat's principle
The principle that a light ray extending from one point to another will, after any number of reflections and refractions, follow the path requiring the least transit time. This is also known as the...
printer
A photographic enlarger with a fixed negative plane and a fixed paper plane, often using a roll of paper that is advanced automatically between exposures. The lens is interchangeable to suit a range...
prism apex
The thin edge of a refracting prism; the line of intersection of two refracting surfaces of a prism.
prism base
The thick edge of a refracting prism.
prism binoculars
A pair of telescopes with prismatically erected images, mounted side by side with the eyepieces at the interocular distance of the observer. This separation is adjustable with a convenient millimeter...
prism chromatic resolving power
The chromatic resolving power of a prism is invariably stated for the case in which parallel rays of light are incident on the prism, in which the prism is oriented at the angle of minimum deviation...
prism coupler
An instrument that measures the angle at which a prism can couple laser light into an optical waveguide; used to determine the thickness and refractive index of thin films in integrated optical...
prism ghost
The ghost image formed by a prism.
prism power
The power, expressed in prism diopters, that is the linear displacement, in centimeters, produced by the prism one meter away.
prism spectrograph -> spectrograph
An optical instrument for forming the spectrum of a light source and recording it on a film. The dispersing medium may be a prism or a diffraction grating. A concave grating requires no other means...
prism
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...
prismatic
Describing a prism, or the effects produced by prisms.
prismatic spectrum
The spectrum formed by a dispersing prism or a dispersing prism system.
prismograph
A graphical device used to measure prism power.
PRK
photorefractive keratectomy
PRM
pulse rate modulation
PRNU
photoresponse nonuniformity
probe
Acronym for profile resolution obtained by excitation. In its simplest form, probe involves the overlap of two counter-propagating laser pulses of appropriate wavelength, such that one pulse...
probe card
A probe card is a testing device used in the semiconductor manufacturing industry to evaluate and test the electrical characteristics of integrated circuits (ICs) on a wafer. Its primary function is...
process camera
A photographic camera designed to produce reproduction film of visual information (pictures, line drawings, graphs) for printing purposes.
process control
The collection and analysis of data relevant to monitoring the rate and quality of industrial production, either continuously or in batches. Corrections can be made manually or automatically, via a...
process lens
A lens that is symmetrical and designed to work between 1:1 and about 4:1. It covers a field of about ±20° at f/8 or f/10, and may have a focal length up to about 30 in., although the usual...
processed hologram
A superposition of many zone plates, each reconstructing a real and virtual point image at the appropriate locations upon illumination by a reference beam.
profile dip -> index dip
The decrease in the refractive index at the center of a fiber's core, caused by certain fabrication techniques. Also called profile dip.

Photonics DictionaryP

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