Photonics Dictionary

Pertaining to or as a function of wavelength. Spectral quantities are evaluated at a single wavelength.

The wavelength interval in which radiant intensity is at least 50 percent of the maximum spectral value.

Average wavelength usually determined for light-transmitting devices by taking a weighted average for each wavelength of the spectral energy distribution of incident light, transmittance of the...

Spectral domain optical coherence tomography is an imaging technique used in medical diagnostics, particularly in ophthalmology, to visualize and analyze the internal structures of biological...

Spectral flow cytometry is an advanced flow cytometry technique that expands the capabilities of traditional flow cytometry by utilizing spectral information from fluorochromes to enhance...

With respect to color photography, the measurement, at a given wavelength, of the way the color film modulates the radiant flux in the optical system containing the film.

Irradiance per unit wavelength interval at a given wavelength, expressed in watts per unit area per unit wavelength interval.

A narrow range of emitted or absorbed wavelengths.

A slight displacement in the position of a spectral line because of an alteration in frequency, as a result, in turn, of a cause such as the Doppler effect.

Ratio of the luminous flux in a beam of radiation to the spectral radiant flux in the same beam at a given wavelength.

Ratio of the radiant flux at a particular wavelength lm to that at any other wavelength l, such that both radiations produce equally intense luminous sensations. The wavelength lm is chosen so that...

When, for example, a beam of monochromatic light passes through a diffraction grating, the emergent rays that have remained undeviated are included in the zero spectral order. The light flux in the...

The relative power emitted by a source as a function of wavelength. It determines the color-rendering properties of the source.

Any pyrheliometer that has a filter placed over its sensor to limit the range of solar radiation it will detect; used to determine the distribution of solar radiation over its visible and into its...

Radiance per unit wavelength interval at a given wavelength, expressed in watts per steradian per unit area per wavelength interval.

Spectral repeatability refers to the consistency and reproducibility of spectral measurements across multiple trials or instances. It is a measure of how well a measurement instrument or system can...

Measure of a detector's signal during exposure to radiation of a constant power level and varying wavelength.

A classification of particular regularities that occur in the spectra of many atoms.

A spectral signature, in the context of remote sensing and spectroscopy, refers to the unique pattern or characteristic spectral response of a material or object across different wavelengths of the...

A measure of the wavelength extent of a spectrum.

A wavelength region of relatively high transmittance, surrounded by regions of low transmittance.

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

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.

The line from a spark or other very hot source that has greater intensity than that of a line produced by an arc or flame source. Also called an enhanced line.

The frequency space between consecutive transmission peaks in the transmission spectrum of a Fabry-Perot interferometer or etalon. The free-spectral range is inversely proportional to the distance...

Hyperspectral imaging is an advanced imaging technique that captures and processes information from across the electromagnetic spectrum. Unlike traditional imaging systems that record only a few...

A hyperspectral imaging camera is a sophisticated imaging device capable of capturing and processing data across a wide range of wavelengths within the electromagnetic spectrum, typically from...

Hyperspectral resolution refers to the level of detail or granularity in the spectral information captured by a hyperspectral imaging system. In hyperspectral imaging, the electromagnetic spectrum is...

Spectra that originate from atoms; they are composed of lines having irregular spacing and intensity.

A spectrometric instrument that detects radiation simultaneously in multiple channels, sorts it spectrally from the deep ultraviolet to the infrared, digitizes the information and stores it for...

Multispectral imaging is a technique that involves capturing and analyzing images at multiple discrete spectral bands within the electromagnetic spectrum. Unlike hyperspectral imaging, which acquires...

The use of narrow bandpass filters and special photographic emulsions to discern features of a surface that would not be easily recognizable with regular black-and-white or color photographic methods.

An instrument used to record the emittance or reflectance of an object by scanning with discrete spectral resolution over a wide spectral band, or recording many discrete spectral bands...

A color whose hue is not produced by a single wavelength in the visible spectrum, but is instead produced by mixing the longest (red) and shortest (blue) wavelengths of the spectrum such as any...

The wavelength at which a lamp radiates its highest intensity.

An emission spectrum is a graphical representation or a characteristic pattern of the wavelengths or frequencies of light emitted by a source, such as an atom, molecule, or celestial object. It shows...

A perfect diffuser that exists only as a concept, or a white with known spectral characteristics used as a reference in measuring absolute reflectance.

An absorption peak refers to a sharp increase or spike in the absorption of electromagnetic radiation at a particular wavelength or energy level. It is a distinctive feature in the absorption...

Photographing of terrain on the ground and objects in the air by cameras mounted in aircraft; utilized in satellites, multispectral scanning and intricate data handling systems.

The ratio of radiant energy reflected from a rough surface to that incident on it. Usually, the radiant energy is total solar energy; thus, it is not a spectral quantity.

A spectral phenomenon in which the degree of the photoresponse of an illuminated semiconductor is determined by the wavelength composition of the incident light.

An APD detector, or avalanche photodiode detector, is a type of photodetector used to detect light or optical signals by converting incoming photons into electrical current. It operates based on the...

A camera designed to record astronomical objects (e.g., stars, planets, nebulae, galaxies) and their spectra.

The use of photographs to record astronomical objects and phenomena for purposes of physical observation and measurement of motion, radiation and spectra.

An instrument that photographs the spectra of an extraterrestrial object.

Compilation of the Air Force Cambridge Research Laboratories that contains values of the line parameters of the 1-0 bands of 12C16O. Because of the high accuracy of this record, calculated spectra...