Photonics Dictionary: D

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damped least squares

An organizational method used in optical design computer programs. The technique produces one number (merit function) to measure the state of correction of an optical system. This number, which is...

deflection under static load

For an optical table, the amount of displacement that occurs when a heavy load is placed or moved on the surface. To measure deflection under static load, a 113-kg (250 lb) weight is placed in the...

densitometer

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...

density -> optical density

A measure of the transmittance through an optical medium. Optical density equals the log to the base 10 of the reciprocal of the transmittance. where τλ is transmittance. In spectroscopy,...

diffraction efficiency

Diffraction efficiency is a measure of how effectively a diffractive optical element (DOE) or diffraction grating directs light into specific diffraction orders or achieves a desired optical effect....

diffraction grating

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...

diffraction velocimeter -> laser velocimeter

A system that uses a continuous-wave laser to measure the velocity of an object by focusing the laser beam on the object, perpendicular to its direction of motion. An optical grating receives...

diffuse reflectance spectroscopy

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...

diopter

A unit of optical measurement that expresses the refractive power of a lens or prism. In a lens or lens system, it is the reciprocal of the focal length in meters. For example, if a lens has a focal...

distributed feedback laser

A distributed feedback laser (DFB laser) is a type of semiconductor laser diode designed to emit coherent, narrow-bandwidth light with precise control over the wavelength. It achieves this through a...

dots per inch

A measurement of the spatial resolution of a line or area array in an optical character recognition scanning device.

Photonics DictionaryD

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