Tradeoffs in Imager Design with Respect to Pixel Defect Rates

Previously we have shown that image sensors are continuously subject to the development of in-field permanent defects in the form of hot pixels. Based on laboratory measurements of defect rates in 21 DSLRs and 10 cell phone cameras, we show in this paper that the rate of these defects depends on the technology (APS or CCD) and on design parameters the like of imager area, pixel size, and gain (ISO). Comparing different sensor sizes has shown that the defect rate does not scale linearly. Comparing different pixel sizes has demonstrated that defect rates grow rapidly as pixel area shrinks. Finally, increasing the image sensitivity (ISO) causes the defects to be more noticeable, thus increasing the defect rate. These defect rate trends result in interesting tradeoffs in imager design, allowing the designer to determine the specific imager parameters based on the imager's designated function and reliability requirements.