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8,236 terms
Photonics Dictionary
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PCM
pulse code modulation; phase-conjugate mirror
PCMI
photochromic microimage
PCR
photoconductive relay; polymerase chain reaction
PCS
plastic-clad silica; photon correlation spectroscopy
PCT
photon-coupled transistor
PCVD
plasma chemical vapor deposition
PDA
photodiode array; postdeflection acceleration
PDCR
polarization-dependent coupling ratio
PDG
polarization-dependent gain
PDIO
photodiode
PDL
polarization-dependent loss
PDLC
polymer dispersed liquid crystals
PDM
pulse duration modulation
PDP
parallel detection polychromator
PDS
photodischarge spectroscopy
PDT
photodynamic therapy
PE
processing element
peak spectral emission
The wavelength at which a lamp radiates its highest intensity.
peak wavelength
The wavelength at which the radiant intensity of a source is maximum.
PEC
photoelectric cell
Pechan prism
A prism made up of two air-spaced components. It has the ability to revert, and not invert, an image, and can be used in convergent, divergent and parallel light. May be rotated to compensate for...
pedestal component
Present in photocurrent burst, it is the low frequency pulse that corresponds to the light scattered from the beams in the absence of heterodyne mixing.
peel point
In a fiber optic guided missile, the point at which the optical fiber pays out from the bobbin on which it is wound.
pel
Contraction of "picture element." See pixel.
pellicle mirror
A thin, stretched plastic membrane cemented to a rigid supporting ring. It may be coated to act as a beamsplitter, for example, in a color camera; it is so thin that no perceptible image doubling...
Pellin-Broca prism
A form of dispersing prism, often used in monochromators, that consists of a common right-angle prism with a 30° dispersing prism attached to each of its square faces. The spectrum formed by the...
Peltier cooler
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...
Peltier effect
See thermoelectric cooling.
PEM
photoelectromagnetic
pencil beam
In astronomy, the main lobe of an antenna pattern that has a small angular extent in two mutually perpendicular directions. Invisible in space, it would resemble a searchlight beam.
Penning discharge
A standard source of high-charge-state ions for accelerators that has an external magnetic field oriented perpendicularly to the two cathode faces. Also called Philips ionization gauge.
penta prism
A five-sided prism containing two reflecting surfaces at 45° to each other, and two refracting faces perpendicular to the entering and emerging beams. The deviation angle of 90° is...
pentamirror
A pentamirror is an optical component found in SLR cameras, composed of multiple flat mirrors arranged in a pentagonal configuration. Its primary function is to redirect light from the camera lens to...
pentaprsim
A pentaprism is a five-sided glass prism used in optical devices, particularly in SLR cameras, to deviate the path of light by 90 degrees and ensure that the image seen through the viewfinder is...
penumbra
A source of light will not cast a distinct shadow of an interfering, opaque object, but will cast a shadow having two parts: 1. the umbra, or the central, totally dark part of the shadow; and 2. the...
perceived color
The apparent color, as seen by the human eye, as distinguished from color as a measurable property of light.
perfect crystal
A crystalline substance in which all planes are parallel, or approximately parallel.
perfect diffuser
A surface that obeys Lambert's cosine law and has a reflectance of unity.
perfect lens
A theoretical, ideal lens capable of producing perfect images. Used as a lens design and analysis tool to image collimated output from an afocal system.
perimeter
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eye test apparatus
Instruments used by ophthalmologists and optometrists to study the eye. There are, for instance, the ophthalmoscope to observe and photograph the retina; the retinoscope and optometer to determine...
perimetry
The analysis of retinal zones in which different hues can be detected. Also called campimetry.
periodic wave
A wave of radiant energy in which each point of the wave is repeatedly displaced at equal time intervals.
peripheral
Near the boundary or edge of the field of an optical system; the outer fringe.
peripheral response
In a charge-coupled device, the detection of charge collected by the transport register rather than by the image-sensing elements.
peripheral vision
The ability to see over large angles of view.
periplan eyepiece
A well-corrected flat-field eyepiece with good eye relief. Similar to a Huygenian.
periscope
An optical instrument designed to displace the line of sight in a vertical direction. For submarines and other military uses the periscope is a long tube containing prisms at both ends and...
periscopic lens
Two simple meniscus lenses arranged symmetrically on either side of the aperture stop, providing reduced coma, lateral color and distortion.
permanent magnetic focusing
The focusing of an electron beam by a magnetic field that permanently retains the majority of its magnetic properties.
permeability
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...
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Photonics Dictionary
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