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Photonics Dictionary: P

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profile dispersion
In an optical waveguide, that dispersion attributable to the variation of refractive index profile with wavelength. The profile variation has two contributing factors: variation in refractive index...
Measurement of surface roughness or quality through the use of a diamond-pointed stylus connected to a coil in an electric field. As the stylus is traced across the surface, a current is created that...
programmable logic controller
In computerized industrial process control, the element that determines the choice and sequence of operations dependent on varying conditions.
projecting core coupler
A device that couples a light source to an optical fiber by projecting an image of the source and the fiber core onto a screen where they can be superimposed by micropositioners.
projection moire topography
A contour mapping technique that involves projection of a grating onto an object to produce a shadow grating that is observed through another grating. Therefore, the size of the object to be measured...
projection pointer
A device used to project a small area of light on a screen for indication.
projection printer -> 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...
projection thermography
The measurement of surface temperature by a thermograph that forms a pattern of the heat radiated by the surface on a luminescent screen.
projection x-ray microscope
A microscope that uses an extremely fine x-ray focal point to produce an enlarged photographic image of a sample. Also known as an x-ray shadow microscope.
prolate crystal -> positive crystal
A uniaxial, birefringent crystal having an ordinary ray with a higher velocity than the extraordinary ray.
Pockels readout optical memory; programmable read-only memory
proof strength
The minimum amount of strength characteristic of an optical fiber, as determined by proof stressing; expressed in thousands of pounds of pressure per square inch.
proof stressing
A means of testing the strength of optical fibers to ensure reliability, by applying stress to the fiber so that any flaws generated during manufacturing or handling result in breakage of the fiber.
proof-of-concept system
An assembly of prototype instruments, equipment and/or software designed to perform all the functions of a concept or idea which, when operated as a system, produce evidence, results or data...
propagation constant
For an electromagnetic field mode varying sinusoidally with time at a given frequency, the logarithmic rate of change, with respect to distance in a given direction, of the complex amplitude of any...
protective bevel
The removal of a sharp edge on an optical element by grinding, to prevent accidental chipping of that edge during subsequent handling.
protective coating
A film applied to a coated or uncoated optical surface primarily for protecting this surface from mechanical abrasion, from chemical corrosion, or from both. For example, a thin layer of silicon...
proximal scanning
Technique using a fiber optic assembly to illuminate an opaque object and transmit an image back from it without a lens system on the distal end.
proximity effect
The underexposure caused by the diffraction of light passing through small openings spaced closely together in masks used in photolithography.
proximity probe
A noncontact sensor used in the remote measurement of position, speed or other variables of moving parts.
proximity-focused image tube
A planar photocathode and a planar phosphor screen mounted in a close-spaced parallel configuration in an evacuated enclosure so that the ensemble of photoelectrons emitted from each photocathode...
proximity-mode sensing
A method of sensing by transmitting energy from the sensor and detecting the energy after it has been reflected by the object in its path.
position-sensing detector; pseudo-second derivative
power spectrum equalization
A method used to approximate the values of the homogeneous second derivatives at each iteration in the course of lens design and that excels the rate of convergence of the damped least squares method...
In image processing, generating a color image from monochrome data by assigning a color to each of the gray levels.
Coded image obtained optically with a nonredundant pinhole array imaging aperture.
pseudoscopic image
An image that is reversed contour or inside-out.
point spread function
pounds per square inch
pounds per square inch absolute
pounds per square inch gauge
phase-shift keying
photon scanning tunneling microscope
photoconductive thermoplastic
pulse transfer function
phototherapeutic keratectomy
photon tunneling microscope; pulse transmission mode
public telecommunications operator
post, telephone and telegraph
An astronomical body that emits radiation concentrated by a strong magnetic field into two beams that rotate, giving a pulsing effect.
pulse amplification
The compression and intensification of a laser pulse of a specific width into a smaller pulse width. A spherical cavity, in conjunction with a beam compressor, is efficient for pulse amplification....
pulse analyzer
The instrument used to analyze a pulsed electromagnetic wave to determine its time, amplitude, duration and shape, and to display this information in some appropriate form, either visually or...
pulse code modulation
System of information coding in which the signal is sampled 8000 times per second and the samples quantized by referring them to a series of preset 8-bit codes. Thus digitized, the signal is sent to...
pulse compression
A means of achieving higher peak powers and more efficient harmonic generation by narrowing the pulse width and thus increasing the frequency bandwidth of the output of CW mode-locked lasers....
pulse counter detector
A device designed to detect frequency-modulated signals by forming a unidirectional pulse from each sine wave. The direct current of the pulse is proportional to the frequency of the...
pulse duration
The lifetime of a laser pulse, generally defined as the time interval between the halfpower points on the leading and trailing edges of the pulse.
pulse energy thermography -> pulse video thermography
A noncontact, nondestructive method of measuring defects in thin composite materials, using a xenon flashtube to generate heat in a sample. A thermal imaging system detects differences in the rates...
pulse forming network
A series of capacitors and inductors connected to the flashlamp in a pumped Nd:YAG laser system in order to regulate the pulse shape of the current delivered to the lamp at a given operating voltage.

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