Photonics Dictionary

1. The basic unit of length in the metric system, equal to 39.37 in. or 3.28 ft. 2. Any device or instrument used for measuring. The term often appears in conjunction with the quantity it measures,...

Device which measures the index of refraction of glass as well as the dispersion over visible range.

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

A measuring device that uses a light-sensitive cell or detector to determine the amount of light transmitted by a substance.

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...

An accelerometer is a sensor or transducer that measures the rate of change of velocity of an object, or in simpler terms, it measures acceleration. Accelerometers are widely used in various...

A device that measures the intensity of photochemically active radiation, particularly from the sun. One form of this instrument determines the fluorescence initiated by the radiation.

An apparatus used to determine the degree of adaptation of the eye under different conditions.

A system used for measuring direct solar radiation.

An instrument designed to measure the numerical aperture of an objective.

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...

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...

A device used to measure power loss in fiber optic connectors, cables or systems.

1. Calculated distance between two exactly opposed points on a beam at a chosen fraction of peak power (typically 1/e2). 2. The diameter of a circular aperture that will pass a specified percentage...

Device used to measure the numerical aperture of a microscope, composed of a 14-mm-thick glass block with numerical aperture gradations carved onto its lower surface.

A device used to compare the luminous intensities of two sources by locating a point between the two light sources where the produced flux densities are equal. The luminous intensities of the two...

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

A thermometric instrument used for the detection and measurement of radiant energy. Its essential component is a short narrow strip covered with a dead black absorbing coating and mounted at the...

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 instrument for measuring the brightness (luminance) of a scene. It may be a spot meter, covering an area of a degree or less, or an averaging meter, covering a broad area of the scene. Brightness...

An instrument used to measure the change of heat content of a system by measuring microwave power in terms of generated heat.

An instrument incorporating an infrared detector assembly, used to analyze carbon dioxide gases and in medical applications to monitor air exchange in the lungs of patients on ventilators or under...

A type of comparator with a telescope equipped with a cross wire mounted on a vertical sliding column. It is used to measure vertical distances on fairly near objects.

A light-sensitive detector having a chemical compound that reacts when exposed to light. It is used in photochemistry and relies on the chemical reaction to determine the amount of incident radiation.

An instrument for measuring the vertical angle of an object. It usually contains an accurately made protractor, a sensitive level bubble, and a sighting device, such as a small telescope.

A closed-loop system that compensates for thermal blooming by optimizing only one parameter: the amplitude of the phase correction.

A device containing two photocells behind deep red and blue filters to measure color temperatures. The amplifier gain is adjusted to give a set reading of one photocell; the reading of the other is a...

A colorimeter is a device used to measure and quantify the color characteristics of an object or a light source. It provides objective and standardized color information, typically expressed in terms...

A photometer that uses a set of color filters to measure the intensity of light in various regions of the spectrum.

A device used to project a reference spectrum next to a spectrum to be analyzed to provide visual comparison.

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

An instrument designed to measure the proportion of light emitted by a source in the blue region of the spectrum.

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

1. An instrument used to measure the opacity or density of dyes, pigments or dispersed particles that form an image in or on a medium, such as a photographic film. 2. A device used to measure the...

In an optical rangefinder, the system of wedges that rotate in opposite directions to aid in the detection of deviation in the image axis.

A device that produces an interferogram that can be directly related to the temperature gradient and thereby provides a direct measure of the convective heat transfer coefficients.

A measurement device used to study the structure of matter using the diffraction of electromagnetic radiation.

An instrument used to measure expansion of solids, liquids and gases.

A telescopic system having an eyepiece, a reticle and an objective. The instrument measures wavefront power in diopters.

A device that provides simple and reliable laser power and energy measurement. Essentially a heat flux sensor producing an output proportional to the power, rather than the energy input.

A colorimeter using a spinning disc made of different colored sections for colorimetric analysis.

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...