For fixed pattern noise in video projectors see Screen door effect. Fixed pattern noise is the term given to a particular noise pattern on digital imaging sensors often noticeable during longer exposure shots where particular pixels are susceptible to giving brighter intensities above the general background noise.

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  • For fixed pattern noise in video projectors see Screen door effect. Fixed pattern noise is the term given to a particular noise pattern on digital imaging sensors often noticeable during longer exposure shots where particular pixels are susceptible to giving brighter intensities above the general background noise. Fixed pattern noise (FPN) is a general term that identifies a temporally constant lateral non-uniformity (forming a constant pattern) in an imaging system with multiple detector or picture elements. It is characterised by the same pattern of 'hot' (brighter) and cold (darker) pixels occurring with images taken under the same illumination conditions in an imaging array. This problem arises from small differences in the individual responsitivity of the sensor array (including any local postamplification stages) that might be caused by varations in the pixel size, material or interference with the local circutry. It might be affected by changes in the environment like different temperatures, exposure times etc. The term "fixed pattern noise" is usually referred to two parameters. One is the DSNU (dark signal non-uniformity, which is the offset from the average across the imaging array at a particular setting but no external illumination and the PRNU, which describes the gain or ratio between optical power on a pixel versus the electrical signal output. Latter can be described as the local, pixel dependent photo response non-linearity and is often simplified as a single value measured at almost saturation level to permit a linear approximation of the non-linear pixel response. Sometimes pixel noise as the average deviation from the array average under different illumination and temperature conditions is specified. Pixel noise therefore gives a number (commonly expressed in rms that identifies FPN in all permitted imaging conditions, which might strongly deteriorate if additional electrical gain is included. In practice, a long exposure emphasizes the inherent differences in pixel response so they may become a visible defect, degrading the image. Although FPN does not change appreciably across a series of captures, it may vary with integration time, imager temperature, imager gain and incident illumination, it is not expressed in a random spatial distribution, occurring only at certain, fixed pixel locations.
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  • For fixed pattern noise in video projectors see Screen door effect. Fixed pattern noise is the term given to a particular noise pattern on digital imaging sensors often noticeable during longer exposure shots where particular pixels are susceptible to giving brighter intensities above the general background noise.
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  • Fixed-pattern noise
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