Since every pixel has its own amplifier circuit for converting the electrons to a voltage signal, each pixel will have a slightly different read noise value. The final digitized signals are then read out sequentially at a pixel readout speed which normally can be set at different speeds.The analog voltages are then converted to digital signals via columns of analog to digital (A/D) converters.These pixel voltages are transferred to the column bus via a row select signal.The photo-generated charge is converted to an analog voltage for each pixel amplifier.Photons hit the sensor and generate charge (electrons).The overall process is outlined below:įigure 1: The main components of a sCMOS sensor. The readout process for sCMOS however is different, sCMOS sensors are often referred to as “Active Pixel Sensors” (APS) since each pixel has its own amplifier circuit (Figure 1). Therefore, the read noise of a CCD sensor can be described by a single readout noise value. In the case of CCD sensors, all the pixels in a sensor pass through a common architecture and are essentially subject to the same sources of noise during the readout process. In this technical note we look at some of the important aspects of read noise for sCMOS sensors. Read noise is created within the camera electronics during the readout process as the electrons are subjected to the analog to digital conversion, amplification and processing steps that enable an image to be produced. One of the main types of noise that makes up this noise floor comes from “Read Noise”. A low noise floor also allows for the widest possible dynamic range. A low noise floor means that the camera can detect signals that would otherwise have remained hidden within the noise background which helps to produce a high-fidelity image. SCMOS based cameras can provide a much lower noise floor than typical CCD based cameras. Understanding Read Noise in sCMOS Cameras
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