In cameras that are designed for use in less stringent bright-light applications, a camera designer may focus, for example, on reducing the size/cost of the camera while permitting some tradeoffs in read noise.ĭark shot noise results from the fact that even if there is no light at all falling on a pixel, the photodiode “faucet” still has a small flow of “leakage” electrons that are generated thermally. In cameras that are designed for use in low-light scientific imaging applications, everything, from size/enclosure design to circuit board layout is done with the goal of minimizing noise, with read noise being a primary concern. Read Noise also depends very significantly on the camera design techniques. Read noise can depend on the choice of the imaging technology, for example cameras with sCMOS image sensors typically have a lower read noise as compared with most CCD or CMOS cameras. The temporal variation represented by “read noise” is a function of the imager used, the clock rate and the level of care taken by the camera designer to protect the signal from interference. For this reason, different cameras that use the same imager may have different values for their read noise. Some of these factors are dependent upon the imager, but it is also a function of the design, partitioning and layout of the camera electronics. It includes the temporal variations introduced in the process of transferring charges from each pixel, converting charges to a voltage waveform and then digitizing the waveform. Although it is typically specified as a number of electrons (for example, read noise = 2e –), it is an aggregate of several different non-idealities. Read noise is a term used to describe the temporal variation caused by non-idealities in the measurement process.
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