15 February 2012 Projecting the rate of in-field pixel defects based on pixel size, sensor area, and ISO
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Abstract
Image sensors continuously develop in-field permanent hot pixel defects over time. Experimental measurements of DSLR, point and shoot, and cell phone cameras, show that the rate of these defects depends on the technology (APS or CCD) and on design parameters like imager area, pixel size, and gain (ISO). Increased image sensitivity (ISO) enhances defects appearance and sometimes results in saturation. 40% of defects are partially stuck hot pixels, with an offset independent of exposure time, and are particularly affected by ISO changes. Comparing different sensor sizes with similar pixel sizes showed that defect rates scale linearly with sensor area, suggesting the metric of defects/year/sq mm. Plotting this rate for different pixel sizes (7.5 down to 1.5 microns) shows that defect rates grow rapidly as pixel size shrinks. Curve fitting shows an empirical power law with defect rates proportional to the pixel size to the power of -2.1 for CCD and to the power of -3.6 for CMOS. At 7um pixels, the CCD defect rate is ~2.5 greater than for CMOS, but for 2.4um pixels the rates are equal. Extending our empirical formula to include ISO allows us to predict the expected defect development rate for a wide set of sensor parameters.
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Glenn H. Chapman, Glenn H. Chapman, Jenny Leung, Jenny Leung, Rohit Thomas, Rohit Thomas, Ana Namburete, Ana Namburete, Zahava Koren, Zahava Koren, Israel Koren, Israel Koren, } "Projecting the rate of in-field pixel defects based on pixel size, sensor area, and ISO", Proc. SPIE 8298, Sensors, Cameras, and Systems for Industrial and Scientific Applications XIII, 82980E (15 February 2012); doi: 10.1117/12.910096; https://doi.org/10.1117/12.910096
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