Photonics Dictionary

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

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...

A detector-Dewar assembly typically refers to a combination of a detector and a Dewar flask used in scientific instruments, particularly in the field of infrared spectroscopy or other applications...

Diamond turning, also known as diamond machining or diamond cutting, is a precision machining process used to produce high-quality optical surfaces and components with extremely tight tolerances. It...

Diamond turning refers to a precision machining process used to produce complex optical components, particularly lenses and mirrors, from materials such as metals, plastics, and crystalline materials...

A flanged or plain ring with a restricted aperture, located in an optical system at any of several points, that cuts off marginal light rays not essential to image formation. Diaphragms are used as...

A dichroic mirror, also known as a dichroic beamsplitter or interference filter beamsplitter, is an optical device that selectively reflects or transmits light based on its wavelength. Dichroic...

A diffraction grating is an optical component consisting of a surface with a periodic structure of equally spaced, parallel grooves or rulings. These rulings act as an array of closely spaced slits...

An instrument that can preselect intervals, often in increments of 1, 10 or 100 ns, for the generation of electronic pulses by means of front-panel switches. Also called a time-delay generator.

Digital signal processing (DSP) refers to the manipulation and analysis of signals, which are representations of physical quantities that vary over time or space. In the context of DSP, these signals...

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

The adjustment of the eyepiece of an instrument to provide accommodation for the eyesight differences of individual observers. The axial distance through which the eyepiece must be moved, to provide...

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

The vertical angular disparity between the lines of sight of the left and right systems in a binocular instrument. Dipvergence is plus when the right image is below the left image.

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...

Dispersion refers to the phenomenon where different wavelengths (colors) of light travel at different speeds when passing through a medium. This variation in the speed of light for different colors...

1. In optics, the bending of rays away from each other. 2. In lasers, the spreading of a laser beam with increased distance from the exit aperture. Also called beam spread. 3. In a binocular...

A defect of a binocular instrument causing two images to be seen separately instead of being fused. It is caused when the optical axes of the two telescopes are not parallel. In minor cases, the eyes...

A spectrophotometer in which the beam emitted by the radiation source is split into beams that travel through the sample and a reference cell and are subsequently recombined to fall on the detector....

A gradual change in the output of a circuit or instrument over time.

An instrument that uses a photoelectric system to determine the size and volume of dust particles in a given unit of air.

A radar system that uses electro-optic rather than microwave instrumentation and methods to perform its acquisition and tracking functions.

An electron instrument used to reflect an electron beam totally.

An instrument that serves to produce an enlarged electron image on a fluorescent screen by focusing an infrared image of a distant object upon a photosensitive cathode.

A nonmagnetic instrument utilizing an electrofocus and deflection tube with a photocathode for imaging purposes. The optical image is converted into a photoelectric output at the photocathode and is...

An instrument used to print an optical image on a specially treated paper. Light and dark portions of the original image are illustrated by electrostatically charged and uncharged portions of the...

The term "embedded laser" typically refers to a laser device that is integrated or embedded into a larger system or structure. In this context, "embedded" implies that the laser is an integral part...

The entrance slit, also known simply as the slit, is an essential component in optical instruments such as spectrometers and monochromators. It is a narrow opening or aperture through which light...

An etalon is an optical device that consists of two parallel reflecting surfaces separated by a precise and known distance. It operates based on the principle of optical interference and is used to...

Etaloning is an optical phenomenon that occurs in imaging systems, particularly in devices such as spectrometers, interferometers, and cameras. It is characterized by the appearance of interference...

An instrument used to measure the light from a scene to be photographed and to indicate the camera lens and shutter settings required to expose the film correctly. The exposure time required in a...

1. A strainmeter capable of measuring the change in the relationship between two reference points, provided that the points are separated by at least 20 to 30 m. 2. An instrument used to determine...

Instruments used by ophthalmologists and optometrists to study the eye. There are, for instance, the ophthalmoscope to observe and photograph the retina; the retinoscope and optometer to determine...

Also known as ocular. The lens system used between the final real image in a visual optical system and eye. It acts as an image magnifier. Many types of eyepieces are known; e.g., the Huygens used in...

The effect discovered by Faraday in 1845 whereby nonoptically active materials or substances become capable of rotating the polarization plane of polarized radiation (light) passed through them when...

A fiber optic spectrometer is a device used for measuring the spectral content of light. It utilizes optical fibers to transmit light from a source to a spectrometer unit, where the light is...

A fiber-coupled LED (light-emitting diode) refers to an LED device that is optically coupled to an optical fiber for the purpose of efficient light transmission. In this configuration, the LED serves...

An optical instrument consisting of an objective lens, a coherent (usually flexible) fiber bundle and an eyepiece to examine the output of the fiber bundle.

An image-forming instrument in which a strong electrostatic field causes cold emission of electrons from a sharply rounded point or from an object that is located on that point. The electrons are...

1. A lens situated at or near the plane of an internal image to project the aperture of a previous objective or erector upon the aperture of a following lens. 2. A lens at or near the plane of a...

The field of view (FOV) refers to the extent of the observable world or the visible area that can be seen at any given moment through a device, such as an optical instrument, camera, or sensor. It is...

An instrument designed to place nongraphic information, usually generated by a computer, onto photographic film. The information is generally encoded as a series of opaque and translucent spots, or...

An interferometer spectrometer designed to measure thicknesses of thin films or layers by recording the interferogram and by having a computer within the instrument to establish the distance between...

Any of a number of instruments that uses a flame to vaporize a solution of the chemical being analyzed so that light may be passed through the vapor. Monochromation of the transmitted light is...

An instrument designed to give a visual indication to the pilot when the plane has strayed from a specific flight path.

Flow cytometry is a powerful technique used in biology and medicine for the quantitative analysis of the physical and chemical characteristics of cells and particles suspended in a fluid. The method...