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Photonics Dictionary

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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...

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

scalar diffraction theory

Scalar diffraction theory is a simplified approach used to describe the propagation of electromagnetic waves, particularly light, as they encounter obstacles or apertures. It is termed "scalar"...

Schmidt camera

A camera that consists of a concave spherical mirror with an aspheric plate situated at the center of curvature of the mirror. The purpose of the plate is to correct the spherical aberration of the...

Shack-Hartmann wavefront sensor

The Shack-Hartmann wavefront sensor is an optical device used for measuring the wavefront aberrations of an optical system. It is widely used in adaptive optics systems to correct distortions and...

slit

An aperture, usually rectangular in shape, with a large length-to-width ratio, and a fixed or adjustable shape through which radiation enters or leaves an instrument. The aperture is generally small...

snooperscope

An instrument used for viewing in low levels of illumination by means of infrared radiation. A high-aperture lens forms an image of distant objects on the photocathode of an infrared-sensitive image...

soft-focus lens

A lens that exhibits spherical aberration when used at large aperture settings, and that forms an image with a slightly blurred outline.

Sonnar lens

A photographic objective that uses the thick meniscus principle to obtain its power. It is designed to photograph small fields at large apertures.

stop down

To reduce the size of a lens aperture, which increases the depth of field.

symmetrical lens

A lens system made up of two sets of similar lenses, each of which compensates for many of the aberrations produced by the other. The lens sets are arranged symmetrically on either side of the...

Talbot's bands

The series of interference bands that appear in the spectrum when a specified glass plate is inserted into a spectroscope, from the side of the blue portion of the spectrum, so that the plate...

Talbot's law

The law stating that the brightness of an object that is examined through a slotted disc, rotating over a critical frequency, is proportional to the angular aperture divided by the opaque sectors.

telecentric lens

There are three types of telecentric lenses: -Image-space telecentric lenses are those in which the aperture stop is located at the front focus, resulting in the chief rays being parallel to the...

telescope exit pupil

The image of the aperture stop, usually the objective lens, that is produced by the eye lens. When the exit pupil of the telescope coincides with the entrance pupil of the eye of the observer, the...

thermal imaging

The process of producing a visible two-dimensional image of a scene that is dependent on differences in thermal or infrared radiation from the scene reaching the aperture of the imaging device.

uniformly redundant array

Array used in coded-aperture imaging experiments with two-beam CO2 lasers that provide an artifact-free process, faithful reproduction of the true image, and more photon collection than the pinhole...

upper rim ray -> 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...

V-number -> 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,...

VAFF

variable-aperture far-field

variable-focus condenser

An Abbe condenser in which the upper lens element is fixed. The lower lens may focus the illumination between the elements so that it emerges from the fixed lens as a large-diameter parallel bundle....

vignetting

In an optical system, the gradual reduction of image illuminance as the off-axis angle increases, resulting from limitations of the clear apertures of elements within the system.

wedge spectrograph

A spectrograph in which the flux density transmitted through the entrance aperture is regulated by an optical wedge or similar device.

wide-field fluorescence microscopy

Wide-field fluorescence microscopy uses either naturally occurring structures or staining with fluorescent tags that are activated by specific wavelengths of light and then emits a different...

Winston cone

Specified curved optic intended for maximum collection of light, including off-axis rays, before leaving the exit aperture.

zonal aberration

Spherical or chromatic aberration in a lens having a wide aperture. It is present because the refracting power varies for different zones concentric at the axis. This is the residual when the lens...

Photonics Dictionary

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