![]() As a first estimate of the impact of the dark current one can find the curve fitted to the complete distribution. The lesser gain serves to accentuate the two peaks. 3(b), we present the data obtained for a gain of 0 dB. A clearer view of this bimodality shows up at the smaller gain. The first observation is that there is a bimodal distribution. ![]() Figure 3(a) gives the distribution of the dark current at the largest gain (12 dB), based on a linear fit of the dark count versus exposure time, for times longer than the longest frame time (133.3 ms). 2 that the dark count indeed increases linearly with the frame time. As is borne out by the experiments, we see in Fig. The dark current accumulated in the sense node depends linearly on the frame time. One would assume that the dark count collected in the photodiode of a particular pixel is the same for the different frame rates since the exposure time is fixed. The dark count of Pixel 13 is almost the same for all four frame rates. 2 produces a dark count of 52 DN at a frame time of 16.7 ms and about 3 times as much (155.1 DN) at a frame time of 133.3 ms. For example, for the same exposure time of 10 ms, Pixel 9 in Fig. Pixels were selected to give a representative sample of dark currents in the sense node. 2, the data for a 10 ms exposure at four different frame rates are plot- ted. To investigate the dark current generated in the two different regions, we varied the frame rate. In this CMOS sensor, one needs to keep track of two dark current generation rates. Hence, it is necessary to differentiate between dark count generation in the photodiode and dark count generation in the sense node. However, a careful analysis reveals that almost all of the pixels in this chip have a slight kink at the nominal frame time revealing that most have some dark current generated in the sense node. other words, the dark current in the sense node is small compared to that of the photodiode.
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