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8,289 terms
Photonics Dictionary
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ns x
positive dielectric anisotropy
The dielectric coefficient parallel to the director in a liquid crystal display (LCD), rather than perpendicular to the director.
positive spherical aberration
->
spherical aberration
Spherical aberration is an optical aberration that occurs when light rays passing through a lens or curved optical surface do not converge or diverge to a single focal point. Instead of focusing to a...
positron
->
electron
A charged elementary particle of an atom; the term is most commonly used in reference to the negatively charged particle called a negatron. Its mass at rest is me = 9.109558 x 10-31 kg, its charge is...
positron emission tomography
A medical imaging device that uses a ring of crystal/photomultiplier tube assemblies encircling the patient to detect gamma rays emitted by positrons colliding with electrons.
positronium
Basically, a hydrogen atom with two alterations, positronium is the lightest atom in the universe and has an extremely light positron in its nucleus that replaces hydrogen's proton so that its atomic...
posterization
In image processing, the effect caused by large jumps between gray levels, rather than a gradual change.
pot
potentiometer
potassium titanyl phosphate
A crystalline material with a high electro-optic coefficient, capable of operating at short wavelengths, with applications in laser, optical disc, printing and microwave systems.
potentiometer
A device designed to measure electromotive force or electrical difference potential.
potting
->
imbedding material
A thermoplastic or thermosetting material used to hold an object fixed and keep it from deterioration. In microcircuitry, the process of imbedding is known as potting.
powder camera
A camera system that uses a fine powder to diffract x-rays from the specimen. A beam of monochromatic x-rays passes through a collimator onto the specimen. Diffracted x-rays are recorded on the film...
powder radiography
A technique used in radiography to determine a crystal's structure by obtaining radiographs of it in powder form, normally by the use of a powder camera that forms an image of the crystal's x-ray...
power
With respect to a lens, the reciprocal of its focal length. The term power, as applied to a telescope or microscope, often is used as an abbreviation for magnifying power.
power average
For a pulsed laser, the product of the energy per pulse (joule) and the pulse frequency (hertz); expressed in watts.
power efficiency
The ratio of emitted power to input power.
power flow equation
Optical fiber channel characterization scheme based on three assumptions; the discrete mode spectrum can be replaced by a continuum; the loss due to coupling between guided and radiation modes...
power modulation
Power modulation refers to the intentional variation of power levels in a signal, often in the context of electronic communication systems. This modulation technique is used to encode information...
power ratio
->
radiant power
The time rate of flow of radiant energy, expressed in watts (W), and carries the units of Joule per second (J/s). The prefix often is dropped and the term "power" used.
power scanning laws
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.
power spectrum equalization
A filtering method that restores a blurred image by setting its power spectrum equal to that of the original image.
power supply
Refers to the voltage and current necessary for the operation of circuit devices.
Poynting vector
In remote sensing technology, this represents the intensity of energy flow in the direction of wave propagation.
PP junction
A transition boundary between two regions having different properties in a P-type semiconducting material.
ppb
parts per billion
PPF
polarization-preserving fiber
PPFD
photosynthetic photon flux density
PPKTP
periodically poled potassium titanyl phosphate
PPLN
periodically poled lithium niobate
ppm
pulses per minute; parts per million
PPM
pulse position modulation
pps
pulses per second
PPSLT
periodically poled stoichiometric lithium tantalate
PR
power ratio; photoreflectance
Prandtl number
Ratio of the molecular diffusion coefficients of momentum in terms of heat; used in convection studies.
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.
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Photonics Dictionary
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