4/30/2023 0 Comments Dark noise equivalent power cmos![]() Of course, this wavelength puts the silicon cameras at a disadvantage with much reduced quantum efficiency compared to InGaAs cameras. Figure 3 represents the NEI vs Exposure time at 950nm. We can compare cameras equipped with Silicon and InGaAs FPA detectors, using wavelengths where both technologies are sensitive. Table 3: InGaAs FPA detectors NEI at 1550nmįigure 2: NEI of InGaAs cameras at 1550nm Notice how close all three cameras are despite the fact that the 640 Vis-SWIR has 4 times smaller pixels thanks to lower readout noise and dark current. Long exposure times are also prohibited by the large dark current that fills up the full well capacity about one second. Because the readout noise and dark current is very large compared to silicon based detectors and are not compensated by the high QE and large pixel size. Silicon based detectors NEI at 550nm and Figure 1 compare the NEI of typical EMCCD, CMOS and CCD at 550nm for exposure times ranging from 10ms up to about 15min.įigure 1: NEI of Silicon cameras at 550nmīelow is a comparison of InGaAs FPA detectors NEI at 1550nm (in Table 3 and Figure 2). Still the NEI allows for a precise comparison and ranking. For exposure times in seconds, all technologies are in a similar order of magnitude. Because the quantum efficiency is a function of wavelength and the dark current is a function of the exposure time, it is important to use the wavelength and exposure time of interest for the given application.ĮMCCDs are best for short exposure times (milliseconds) while CCDs are best for long exposure (minutes). ![]() The NEI is a powerful way of comparing different cameras. In this third and final article in the series, we look at how NEI is used to evaluate the sensitivity of wildly different cameras and to rank them for a given exposure time and wavelength. The second article, Camera Sensors for Military Use: Sensor technologies, explored the particular features and function of CCD, EMCCD and CMOS sensor and introduce the equation for Noise Equivalent Power (NEP) and Noise Equivalent Irradiance (NEI). The first article, Camera Sensors for Military Use: Design fundamentals, covered the main variables to consider: Purpose, functionality and SWaP (size, weight and power) as well as performance parameters and tradeoffs. How to choose the appropriate camera sensor for specific military application is the topic of this three-part series.
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