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Photonics Dictionary: O

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O
opacity
OA
optical axis
OADM
optical add-drop module
OAET
Office of Aeronautics, Exploration and Technology
OALM
optical address light modulator
OAMP
optical-analog matrix processing
OAR
off-axis rejection; open area ratio
object
The figure seen through or imaged by an optical system. It may contain structures, natural or artificial, or it may be the real or virtual image of an object formed by another optical system. In...
object beam
In holography, the wave of light that illuminates the object to be recorded, which diffracts it to the recording medium, where it interferes with the reference beam, generating the hologram.
object conjugate -> object distance
The distance between the object and the cornea, or the first surface of the objective in an optical device.
object displacement
The movement of an object seen through a refracting prism toward the apex of a prism.
object distance
The distance between the object and the cornea, or the first surface of the objective in an optical device.
object space
In an optical system, the space between the object being viewed and the system entrance pupil.
object working distance
Distance between the front vertex of a lens and the object.
objective
The optical element that receives light from the object and forms the first or primary image in telescopes and microscopes. In cameras, the image produced by the objective is the final image. In...
objective aperture -> clear aperture
The limited light-gathering area of an optical system. The area is normally restricted to an edge or outer surface of an individual component. Also known as free aperture or objective aperture. The...
objective grating
A coarse diffraction grating that is used to form a scale of intensities to determine the relative magnitudes of stars. The grating is placed over the objective of a telescope to form a diffraction...
objective prism
1. A prism used in some instruments to bend light 90° before it enters the objective. 2. A dispersing prism located in front of an astronomical telescope objective to produce spectra of all...
oblate crystal -> negative crystal
A uniaxial, birefringent crystal such as calcite or ruby in which the velocity of the extraordinary ray surpasses that of the ordinary ray. This can also be defined as the index of refraction of the...
oblique error
The image error that results from astigmatism, coma, oblique spherical aberration, lateral color and distortion.
oblique illumination
A common technique in microscopy, oblique illumination is one in which the object is illuminated by a light source that is at an oblique angle (on the side) to the optical axis. This technique is...
oblique spherical aberration
coma, fifth order aberration with on-axis focal point variation with incident off axis ray height position
observatory dome
A hemispherical covering that is rotatable about a central axis. There is a slit opening along one side wide enough to allow a telescope to be directed at any vertical angle up to 90°.
obsidian
An acid-resistant, lustrous volcanic glass, usually black or banded.
OC
optical computing
occluder
A device that completely or partially restricts the amount of light reaching the eye.
OCCR
optical Chinese character recognition
OCDR
optical coherence domain reflectometer
OCDU
optics coupling display unit
ocean color
Refers to the characteristic hue of the ocean according to the presence and concentration of specific minerals or substances, such as chlorophyll. Atmospheric aberrations of color must be corrected...
OCM
optical countermeasure
OCO
optically coupled oscillator
OCR
optical character recognition; optical character reader
OCT
optical coherence tomography
octave
In optics, an octave typically refers to a range of frequencies or wavelengths that spans a factor of 2. In other words, when dealing with optics, an octave encompasses a doubling of frequency or...
ocular -> eyepiece
Also known as ocular. The lens system used between the final real image in a visual optical system and eye. It acts as an image magnifier. Many types of eyepieces are known; e.g., the Huygens used in...
ocular accommodation
The physical adaption of the eye lens, by means of ciliary muscle contraction, in order to maintain a clear, in focus image of light and other objects and surroundings at a given distance onto the...
ocular accommodation reflex
The eye's involuntary reaction in the process of accommodation. This reflex is most dramatic in response to looking at a distant object after having previously been focused on a near object or vice...
ocular prism
The prism used in a rangefinder to bend the lines of sight through the instruments into the eyepieces.
ocular surface
That surface of a lens located nearest to the eye.
oculometer
An electro-optical infrared tracker consisting of a beamsplitter, an illuminating source, an image dissector tube and an electronics unit, that automatically acquires and tracks particular eye...
OCV
optical character verification
OCWR
optical continuous wave reflectometer
OD
optical density; outside diameter
ODM
optical disc memory
ODN
optical distribution network
ODP
optical data processing
ODS
optical data storage
OEIC
optoelectronic integrated circuit
OEM
original equipment manufacturer

Photonics DictionaryO

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