Photonics Dictionary: D

A frame taken to identify electronic noise in a CCD imaging device. A dark frame is recorded without exposing the CCD to any external light by, for example, leaving the shutter of a CCD camera...

A photomicrographic recording technique that utilizes dark-field illumination to render an image of an object having a refractive index much like that of the medium holding it. The object may be...

A digital camera is a device that captures and records still images or video in digital format. Unlike traditional film cameras, which use photographic film to capture and store images, digital...

Digital holographic microscopy (DHM) is an advanced imaging technique that combines holography and digital image processing to capture and reconstruct three-dimensional images of objects. This method...

A write-once optical disc storage system in which the optical head reads continuously while writing to check the accuracy of the stored data. Data recorded erroneously are then rewritten at another...

In a camera, the focusing of an image on the screen located at the camera's film plane. Once the image is in complete focus, the recording medium is inserted in place of the screen.

A circuit incorporated into counter systems that records only pulses that have amplitudes between two preselected limits.

The formation of an interferogram by means of two holograms on the same recording medium, often used for determining small changes in an object. One hologram produces a primary image that constitutes...

A hologram having an object wave that has been transmitted through the transparent object media to a mirror, reflected again and recorded on a medium.

Interferometric measurement of the interference pattern recorded when a complex object is illuminated by two laser pulses that interfere and form the pattern to be evaluated.

Holographic recording whereby the object is illuminated by two pulses, separated by a time interval, from a Q-switched laser source. Each pulse is divided into reference and object beams, and...

A technique used in astronomy that requires a radio telescope to be directed at a point in the sky west of the object under observation. The Earth's rotation causes the object to drift through the...

A type of streak camera that uses film wrapped around a drum, which moves at a constant speed to record the changing shape of a short-lived event, such as a lightning flash.

An image-processing device that scans in a straight line parallel to the axis of a rotating cylinder to which the material to be recorded is affixed.

A type of erasable data storage device that uses a medium deposited on the disc in two layers, each dyed to absorb a different wavelength of laser light. To record data, the lower layer is heated by...

The superimposition of a pilot object on each hologram. The fixed relative position of the scanning and pilot beam during the recording process ensures that sensing and fixing the pilot beam position...