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8,289 terms
Photonics Dictionary
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perimeter
->
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 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...
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...
perovskite
The term perovskite refers to a specific crystal structure commonly found in various materials. Perovskite structures have a cubic arrangement of oxygen ions, forming a framework within which other...
perpendicular
->
normal
Sometimes referred to as the surface normal or 'surface norm'; the normal is an axis that forms right angles with a surface that light is incident upon or with other lines. The normal is used to...
perspective distortion
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...
PES
photoelectric scanner
PET
pulse energy thermography; positron emission tomography
peta
In the SI system, prefix meaning 1015.
petrographic microscope
A microscope equipped with a polarizer, an analyzer and a Bertrand lens to focus on the upper focal plane of the objective. It is used chiefly by mineralogists and crystallographers for...
petrographic specimen preparation
The grinding and polishing of rock samples, to a thickness of less than 0.05 mm, for study with petrographic microscopes. When mounted on a slide and protected with a cover, these samples, examined...
petrography
The study of and classification of rocks.
Petzval surface
A paraboloidal surface on which the image is located when there is no astigmatism.
PFC
point focusing and centering
PFM
piezoresponse force microscopy; pulse frequency modulation
PFN
pulse forming network
PGA
professional graphics adapter
PGD
planar gas discharge
PHA
pulse height analyzer
phage
A phage, short for bacteriophage, is a type of virus that infects and replicates within bacteria. Phages are composed of genetic material (either DNA or RNA) surrounded by a protein coat. They are...
PHAROS
phased-array optical scanner
pharyngoscope
An optical system used to examine the pharynx.
phase
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 angle
1. The angle between two vectors that represent two simple periodic quantities that vary sinusoidally and that have the same frequency. 2. See phase.
phase annulus
A term for the ring-shaped stop in a phase contrast microscope. The phase annulus limits the amount of light that reaches the phase plate from the direction of the specimen and retards the light by a...
phase conjugation
The use of a reflective device, which can be fashioned from a variety of materials including gases, solids, dyes, aerosols, semiconductor crystals and plasmas, to replicate a laser beam by reversing...
phase contrast microscopy
Phase contrast microscopy is an optical microscopy technique that enhances the contrast of transparent and colorless specimens, making it possible to visualize fine details and internal structures...
phase distrortion
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...
phase hologram
A hologram that is formed on a recording medium by changing the phase of the illuminating wave in correspondence with the recording exposure. It may be formed by contact printing onto a resist...
phase mask
In optics and photolithography, a phase mask refers to a device that modifies the phase of light waves passing through it. The phase mask is used to control the spatial distribution of the light's...
phase matching
Phase matching is a crucial concept in the field of optics, particularly in nonlinear optics and the generation of coherent light. It refers to the condition where the phases of two or more waves,...
phase position
->
phase angle
1. The angle between two vectors that represent two simple periodic quantities that vary sinusoidally and that have the same frequency. 2. See phase.
phase separation
->
leaching
The process of removing some of the constituents of a glass surface by chemical action.
phase shifting
A technique used to generate a phase shift between reference and sample light beams. The phase shift can be performed through the use of a mirror that is moved along the optic axis by a piezoelectric...
phase velocity
For a particular mode in a waveguide, the ratio of the angular frequency to constant phase.
phase-change optical disc
An erasable data recording and storage medium that uses a laser to heat the crystalline surface of the disc to a certain temperature, at which it becomes amorphous and records a bit of information;...
phase-contrast generation
Microscopy technique to convert the phase structure of the wave transmitted or reflected by the specimen into a corresponding intensity structure in the image plane.
phase-contrast microscope
A microscope that has an annular stop in the lower focal plane of the condenser, and a quarter-wave retarding and absorbing ring in the upper focal plane of the objective that just fills the image of...
phase-locked loop
A circuit that uses feedback to synchronize the phase of a voltage-controlled oscillator with the phase of an incoming or reference signal.
phase-only filter
A type of matched filter that responds only to the phase of incoming light; the output has a much greater intensity than that of a classical matched filter, which responds to phase and amplitude. The...
phase-shift keying
A method of coding information in a communications system where the shift in the phase of an electromagnetic wave represents a particular bit or character.
PHB
photochemical hole burning
PHD
pulse height distribution
phenotype
In biology, particularly genetics and evolutionary biology, the phenotype refers to the observable characteristics or traits of an organism, resulting from the interaction of its genetic makeup...
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Photonics Dictionary
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