Flat-field correction

Flat-field correction

Flat-field correction is a technique used to improve quality in digital imaging. The goal is to remove artifacts from 2-D images that are caused by variations in the pixel-to-pixel sensitivity of the detector and/or by distortions in the optical path. It is a standard calibration procedure in everything from pocket digital cameras to giant telescopes.

Flat fielding refers to the process of compensating for different gains and dark currents in a detector. Once a detector has been appropriately flat-fielded, a uniform signal will create a uniform output (hence flat-field). This then means any further signal is due from the phenomenon being detected and not a systematic error.

A flat-field consists of two numbers for each pixel, the pixel's gain and its dark current (or dark frame). The pixel's gain is how the amount of signal given by the detector varies as a function of the amount of light (or equivalent). The gain is almost always a linear variable, as such the gain is given simply as the ratio of the input and output signals. The dark-current is the amount of signal given out by the detector when there is no incident light (hence dark frame). In many detectors this can also be a function of time, for example in astronomical telescopes it is common to take a dark-frame of the same time as the planned light exposure. The gain and dark-frame for optical systems can also be established by using a series of neutral density filters to give input/output signal information and applying a least squares fit to obtain the values for the dark current and gain.

See also

* Dark frame
* Bias frame

External links

* [http://odin.physastro.mnsu.edu/spect_flat.html Flat-Field Correction]


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • Field electron emission — It is requested that a diagram or diagrams be included in this article to improve its quality. For more information, refer to discussion on this page and/or the listing at Wikipedia:Requested images. Field emission (FE) (also known as field… …   Wikipedia

  • Астрофотография — Астрофотография, астрография, астрономическая фотография  способ проведения астрономических наблюдений, основанный на фотографировании небесных тел с использованием астрографов. Преследует две основные цели: Исследовательские. Преимущество… …   Википедия

  • Dark frame — A dark frame is a photography technique to identify noise in a CCD imaging device. This is done by recording without exposing the CCD, usually by leaving the shutter closed and putting the CCD in a dark room. These dark frames are then subtracted …   Wikipedia

  • Bias frame — Much like a dark frame, a bias frame is an image obtained from an optical CCD or CMOS sensor, with no actual exposure time. The image so obtained only contains noise due to the electronics that elaborate the sensor data, and not noise from… …   Wikipedia

  • Dark-frame subtraction — In digital photography, dark frame subtraction is a way to minimize image noise for pictures taken with long exposure times. It takes advantage of the fact that a component of image noise, known as fixed pattern noise, is the same from shot to… …   Wikipedia

  • microscope — /muy kreuh skohp /, n. 1. an optical instrument having a magnifying lens or a combination of lenses for inspecting objects too small to be seen or too small to be seen distinctly and in detail by the unaided eye. 2. (cap.) Astron. the… …   Universalium

  • Hubble Space Telescope — Infobox Space telescope name = Hubble Space Telescope (HST) caption = The Hubble Space Telescope as seen from Space Shuttle Discovery during its second servicing mission (STS 82) organization = NASAESASTScI alt names = nssdc id =… …   Wikipedia

  • Photographic lens — A photographic lens (also known as objective lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media… …   Wikipedia

  • Maksutov telescope — A 150mm aperture Maksutov Cassegrain telescope. The Maksutov is a catadioptric telescope design that combines a spherical mirror with a weakly negative meniscus lens in a design that takes advantage of all the surfaces being nearly spherically… …   Wikipedia

  • optics — /op tiks/, n. (used with a sing. v.) the branch of physical science that deals with the properties and phenomena of both visible and invisible light and with vision. [1605 15; < ML optica < Gk optiká, n. use of neut. pl. of OPTIKÓS; see OPTIC,… …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”