Photonics Dictionary

That point in the electromagnetic spectrum at which an optical system focuses the most chemically effective rays.

Transformation of an image, such as a change in position or scale, that does not alter the linearity of the original image.

An optical system with object and image points at infinity. Literally, "without a focal length."

A coating that is capable of stopping the condensation of moisture on an optical surface.

An atomic force microscope (AFM) is a high-resolution imaging and measurement instrument used in nanotechnology, materials science, and biology. It is a type of scanning probe microscope that...

A means of adjusting the sharpness of an image automatically, with a sensor for estimating distance or contrast and a drive mechanism to adjust the lens. Active systems generate a light source to...

The distance from the final optic within a system to the rear image point of the system. See focal length.

Fraction of light counter propagating collinear with the incident source. Processes considering backscattering are Raman, Brillouin, Rayleigh and Mie.

A two-part lens that has a different focal length for each part. Generally, it is used in eyeglasses to correct for both near and far vision.

Theoretical calculation of the cross section for a nuclear reaction given in the vicinity of a single resonance level in the compound nucleus.

The Casimir force is a quantum phenomenon that results in an attractive force between two closely spaced uncharged conductive surfaces. This force arises from the quantum vacuum fluctuations of the...

A confocal resonator, also known as a confocal cavity or confocal laser resonator, is a type of optical resonator configuration used in laser systems. The term confocal in this context refers to the...

A microscope design that involves apertures inserted in conjugate plane positions inside the microscope, with one aperture in front of the illumination source and the other at the focal position in...

An interferometer formed by two similar concave spherical mirrors arranged with the center of one sphere on the other mirror. In this instrument the field is more concentrated by the axis of the...

A system that determines whether an image is in or out of focus by means of a source of illumination at the conjugate focal point, which reflects off the target; the return beam is mediated by masks...

A formula indicating that, for an imaging lens system, the image brightness for off-axis points will fall off at a rate proportional to the cos4 of the off-axis field angle.

A high-quality focuser that uses rollers rather than gears and offers smooth, precise motion while reducing or eliminating image shift and backlash.

The progressive defocusing of a cathode-ray tube display image that occurs when the deflected electron beam impinges on the cathode-ray tube screen at a slant.

A spatial light modulator consisting of a metallized polymer film stretched over an array of metal-oxide semiconductor field-effect transistors (MOSFETs). Each mirror element in the film can be...

Any of the constants that relate the tendency of the director to remain parallel to restoring torques throughout the media. The three constants of importance in liquid crystal displays are: splay --...

The exact mathematical description of the interactions of matter and intense electromagnetic fields, such as those that occur when laser sources are used to excite flame gases for spectroscopic...

The range of image distances that corresponds to the range of object distances covered by the depth of field.

In a camera, the focusing of an image on the screen located at the camera's film plane. Once the image is in complete focus, the recording medium is inserted in place of the screen.

A composite derived from aluminum alloy powder and silicon carbide, used as an optical substrate in air- and spacecraft applications. It is as light as aluminum but exhibits greater strength and...

A mathematical transformation used in image and video compression that changes two-dimensional representation of data into data defined by the frequency content. Adapted in JPEG and MPEG standards.

All formulas that present the index of refraction as a function of a wavelength of electromagnetic radiation. Also called dispersion equation, Cauchy formula, Hartmann formula.

A mass spectrometer utilizing both radial electrostatic and magnetic field analyzers to improve the focusing and increase resolution.

A mode of laser printing in which each pixel is printed four times, providing sharper lines and a continuous tone from one-quarter the amount of image data, compared with single-raster output.

In image processing, a segmentation algorithm for isolating a region in an image by following its edge.

An electrochemical process of metal fabrication using an electrolyte, an anode to supply the metal, and a control of the electrical current and of the deposit of metal on the matrix of a reflector.

The use of an applied electrical field to focus a cathode-ray tube's electron beam.

An image intensifier that uses electrostatics to amplify and focus the electronic image.

A fiber optic preform is a cylindrical glass rod or tube used as the starting material for manufacturing optical fibers. It serves as the precursor from which optical fibers are drawn. The process of...

A microscope in which laser light is delivered through single-mode fibers that replace the pinhole usually used in confocal microscopy. When the Gaussian mode is imaged from the fiber output onto the...

A wide-field multiobject spectroscopy system used in astronomy, in which a bundle of low-loss optical fibers positioned on the target images is rearranged at its other end into a linear array along...

A transformer that is designed to regulate the amount of current that passes through an electron tube's filament.

Describes devices that are not provided with a means of focusing.