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Photonics Dictionary

Clear All Filters xapertures x
lens mount
The metal tube that maintains the optical components of a lens in proper relationship. Some lenses are mounted in metal cells, which in turn are screwed to the front and rear of a shutter or lens...
limiting aperture
The maximum circular area over which radiance and radiant exposure can be averaged.
LNA
launch numerical aperture; low-noise amplifier
machine vision lens
A machine vision lens is a specialized optical lens designed for use in machine vision systems, which are used for automated inspection, measurement, and quality control in industrial applications....
marginal rays
Also referred to as the axial ray (or a-ray), a marginal ray originates from the axial point of the object and passes through the edge or margin of the entrance pupil (or aperture stop) of the lens...
masks for evaporation/deposition
In the context of thin film deposition processes such as evaporation or sputtering, masks are used to selectively deposit material onto substrates, creating patterns or structures with precise...
MCF
mutual coherence function — The mutual coherence function is a complex quantity that is the time-averaged value of the cross correlation function of a light field at two points within an aperture with a time delay that relates the path difference to the point of observation of the interference fringes. The mutual coherence function is the key function in coherence theory and the study of partially coherent light.
member
In a lens system, a group of elements considered as an entity; either a front or rear member depending on whether it is before or after the aperture stop.
microaperture
A small opening or slit in a mask.
microscope
An instrument consisting essentially of a tube 160 mm long, with an objective lens at the distant end and an eyepiece at the near end. The objective forms a real aerial image of the object in the...
microscope immersion fluid
The liquid used in microscopy to fill the space between the high-power objective lens and the microscope slide in order to increase the numerical aperture (NA) or collecting power in object space of...
microscope objective
The lens located at the object end of a microscope tube. A wide range of objectives is available, including simple achromats, the color-corrected apochromats and the flat-field objectives. Objectives...
minimum spot size
The smallest linear diameter to which a laser or other beam of radiant energy is capable of being focused, depending on the quality of the focusing optics, aperture and focal length, beam irradiance...
moving aperture technique
Method for reducing laser speckle in which the object field comes from a real diffuse object or the reconstructed object field from a hologram. During recording of the image, an aperture is moved in...
multiple slits
The series of equally spaced parallel slits that make up a scanning aperture in place of a single slit, in the scanning of a repetitive pattern.
NA
numerical aperture
near-field diffraction -> Fresnel diffraction
1. Also known as near-field diffraction. The field of radiation sent through an aperture in an absorbing screen at large distances as compared with the wavelength and the dimensions of the aperture,...
near-field region
The area closest to an aperture or source where the diffraction pattern differs substantially from that observed at an infinite distance, or more specifically, the far field. Also referred to as the...
normalized frequency
Also referred to as the V number in fiber optics; the normalized frequency is a dimensionless quantity, denoted by the symbol V, given by: where a is waveguide core radius, l is wavelength in vacuum,...
numerical aperture
The sine of the vertex angle of the largest cone of meridional rays that can enter or leave an optical system or element, multiplied by the refractive index of the medium in which the vertex of the...
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...
oil-immersion objective
A form of high-power microscope objective where the space between the object and the first element is filled with an oil having the same index as that element. This form reduces losses, increases the...
optical bench
A support for optical parts comprising a solid bed that permits precise longitudinal movement of one component relative to the others, and a number of sliders equipped with holders for lenses, lamps,...
optical caliper
A device for measuring linear dimensions. The optical caliper generally consists of two circularly mounted mirrors whose angular positions are monitored by an autocollimator, and that are capable of...
optical rail -> optical bench
A support for optical parts comprising a solid bed that permits precise longitudinal movement of one component relative to the others, and a number of sliders equipped with holders for lenses, lamps,...
overfill
The condition of the numerical aperture or beam diameter of the laser, LED, or other optical source being larger than the optical fiber core or other driven source. Also called overfilled launch...
paraxial
Characteristic of optical analyses that are limited to infinitesimally small apertures. Also called first-order or Gaussian optics.
periscopic lens
Two simple meniscus lenses arranged symmetrically on either side of the aperture stop, providing reduced coma, lateral color and distortion.
Petzval lens
A high-speed, narrow-field lens consisting of two achromats spaced about the aperture stop. Its uses include portrait photography and motion picture projection.
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 translation
The propagation or hindrance of waves reaching each aperture of the interferometer because of atmospheric turbulence.
pinhole camera
A lensless photographic camera that uses a small sharp-edged hole as its aperture. The light passed by this aperture onto the camera's film plane produces a soft-edged image that has a wide field of...
plastic jackets
The direct cladding used for fused silica cores to create large numerical aperture fibers and used as overcoats to glass-clad fibers to reduce microbend loss and increase mechanical protection.
point source lamp
A lamp, usually incandescent, that has a very compact filament, permitting a greater concentration of emitted light, aided by the use of small apertures and appropriate reflectors.
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...
pseudohologram
Coded image obtained optically with a nonredundant pinhole array imaging aperture.
pulse reduction factor
Factor that relates the pulse spread occurring in a graded-index fiber to that of an equivalent step-index fiber having an identical refractive index difference between core and cladding (that is, an...
pupil
1. In the eye, the opening in the iris that permits light to pass and be focused on the retina. 2. In a lens, the image of the aperture stop as seen from object and image space.
RA
reduced aperture
rail -> optical bench
A support for optical parts comprising a solid bed that permits precise longitudinal movement of one component relative to the others, and a number of sliders equipped with holders for lenses, lamps,...
Ramsden circle -> exit pupil
In a lens or other optical system, the image of the aperture stop as seen from image space.
rapid rectilinear lens
A double meniscus system in which two achromatized meniscus lenses are arranged symmetrically on either side of the aperture stop, reducing or eliminating distortion, coma and lateral color.
Rayleigh criterion of resolving power
When a lens system with a circular aperture is free of aberrations, the image of a point object will appear as a disc of finite size surrounded by concentric rings. When two points are separated such...
rear operating aperture
The restricting opening at the rear of a lens or prism that is commonly defined as the maximum diameter of the emergent cone for the specified field of view, at infinity focus.
refracted near-field scattering method -> refracted ray method
The technique for measuring the index profile of an optical fiber by scanning the entrance face with the vertex of a high numerical aperture cone and measuring the change in power of refracted...
refracted ray method
The technique for measuring the index profile of an optical fiber by scanning the entrance face with the vertex of a high numerical aperture cone and measuring the change in power of refracted...
relative aperture
The ratio of the diameter of the entrance pupil in an optical system to the equivalent focal length of that system. The relative aperture is denoted as a fraction in which f, the equivalent focal...
rim ray
A ray of an image-forming bundle that passes through the edge of the entrance pupil or aperture stop. Usually used in connection with meridian rays, an upper rim ray is one that passes through the...
Ritchey-Common test
An interferometric method for describing the surface shape of large coated or uncoated optical flats. The procedure uses a commercially available small-aperture phase-shifting interferometer for...
SAR
synthetic aperture radar

Photonics Dictionary


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