Photonics Dictionary

A prism made up of two air-spaced components. It has the ability to revert, and not invert, an image, and can be used in convergent, divergent and parallel light. May be rotated to compensate for...

An instrument that uses optical filtration in order to measure the transmittance for a discrete range or specific number of wavelengths.

Measures the absorption or sample transmittance over a range of specified wavelengths. Sample may be placed within the device and the transmission measured to an accuracy of given percent. The...

Experimental method of measuring the transmission of a given sample as a function of the wavelength.

Fraction absorption over a specified range of wavelengths.

An optical illusion in which distant objects are lighter in tone and less distinct in outline than those closer to the observer because of the atmospheric diffusion of light.

The angular spectrum approach is a mathematical and computational technique used in the field of optics to analyze and simulate the propagation of optical waves, particularly in the context of wave...

The spectrum of the light produced by vaporizing an element in an electric arc.

The particular orientation of the image, such as normal, canted, inverted or reverted.

With respect to pictorial displays, the ratio of the width to the height. The television standard in the US is 4:3. High-definition or wide-screen television will have a ratio of 16:9.

In an astigmatic grating, the image of the entrance slit located at the primary focus.

An instrument that photographs the spectra of an extraterrestrial object.

The process of using a spectrograph with a telescope to acquire information on an astronomical object's speed and physical characteristics.

The unchanging nature of spectral reflectance as vegetational density increases to the point where additional increases in leaf area index or biomass do not cause a change in the spectral reflectance.

An atomic absorption spectrometer (AAS) is an analytical instrument used to determine the concentration of specific chemical elements in a sample by measuring the absorption of light at...

The analysis of the atomic structure of a sample by means of a source radiation that is absorbed and emitted by the sample with lines corresponding to the number and arrangement of atoms. Generally a...

Spectrometric analysis of the distinct and characteristic spectra of atoms of elements. The atoms are energized to emit radiant energy, which, when dispersed by a prism or diffraction grating,...

The analysis of fluorescence emitted by discrete atoms, in flames, that have absorbed radiation from an external source. It is used to study the physical and chemical processes that arise from...

Attenuated total reflectance (ATR) spectroscopy is a technique used in analytical chemistry to obtain IR spectra of samples. It is particularly useful for analyzing solid and liquid samples without...

Attosecond-pump attosecond-probe spectroscopy (APAP) is an advanced technique in ultrafast spectroscopy that allows scientists to study the dynamics of electronic processes occurring on extremely...

The energy analysis of electrons released in a secondary step following initial excitation or ionization.

A spectrograph in which the refracted beam returns almost along the path traveled by the incident beam, and is brought to a focus by the lens that collimates the incident beam.

Automated optical inspection (AOI) is a technology used in manufacturing processes, particularly in electronics, to automatically inspect and detect defects or anomalies in products. AOI systems use...

A system for automatic industrial process control or measurement, consisting of an optical module for image acquisition, a segmentation processor to isolate the image from its background, and an...

A direct reading spectrograph having a photomultiplier assembly in place of a photographic plate. The output from the photomultiplier assembly is received by a microammeter or a pen recorder.

A spectrum that originates from molecules and that is composed of bands which, in turn, consist of many closely spaced lines. Band spectra are used to determine nuclear spin and statistics, and...

An instrument for the detection of the energy distribution of b-particles and secondary electrons.

A spectrophotometer having a pair of identical collimators with two Glan polarizing prisms, one fixed in azimuth and the other rotatable, set in one collimator. A Brace prism serves as the dispersive...

An emission spectrum consisting of bright bands against a dark background.

That viewpoint at which the angular subtenses of points in the picture are identical to angular subtenses of the original points in the scene, at the camera lens.

A type of spectroscopy used extensively in the analysis of biological samples. Because most biologically synthesized molecules, such as proteins, are optically active, circular dichroism spectroscopy...

A device used for the comparison of spectra used, in turn, for the comparison of elements, such as the absorption lines in the spectra of stars and the spectra of elements in the stars being observed.

In analysis, a reference spectrum, having predetermined wavelengths, that is used to determine the wavelengths of another spectrum through comparison of the two.

The radiation spectrum of matter found in condensed states, liquid or solid, that is continuous and not a line spectrum. The details of this spectrum are almost independent of the matter emitting the...

The spectrographic analysis of matter that is in a cooled state. Generally, a mechanical refrigerator is used to lower the temperature of the sample, allowing isolation and study of the sample and...

A system that applies a crystal as a diffracting agent to photograph the spectrum.

A device designed to measure crystal properties by analysis of crystal diffraction.

A small mass spectrometer, with a limited mass range, equipped with an analyzer to generate a cycloidal-path beam of the sample.

A spectrum having some lines that are darker than others or that contrast against a light, continuous-spectrum background.

The measurement of the spectrum bands formed by a spectroscopic sample, based on the differences between the sample and the reference cell it is placed in.

A spectrograph that uses a diffraction grating as its dispersive element in place of a prism, and yields greater resolving power, more dispersion and a linear spectrum.

In spectroscopy, the parallel bands that vary in lightness and darkness or color, and that are formed when light is diffracted by a sample.

Diffuse reflectance spectroscopy (DRS) is a nondestructive analytical technique used to investigate the optical properties of materials, particularly in the field of spectroscopy. Unlike traditional...

A small handheld instrument consisting of a slit and collimator that feeds light into a small direct-vision dispersing prism. The eye is placed behind the prism to observe the spectrum of a colored...

A spectrum of component wavelengths whose values are separate from each other.

A spectroscope having a divided circle and a means for the rapid reversal of prisms for the measurement of refractive index of the prism for a specific wavelength.

A spectrophotometer that measures the amount of ozone in the atmosphere through a comparison of solar energy at two wavelengths in the ozone's absorption band. This comparison is achieved by...