The changing roles of analog and digital signal processing in CMOS image sensors

Throughout the years digital signal processing has been encroaching more and more into what had previously been exclusive analog circuit domains. Here we briefly summarize various lines of research in CMOS imaging sensing technology paying special attention to the gradual transition from analog to digital processing. The transition from continuous-time continuous-value pixels to digital (discrete-time binary-value) pixels could be viewed as the natural final step in the evolution of these imaging circuits in order to achieve wide dynamic range with acceptable signal to noise ratio. After data is readoff a digital pixel imager chip, digital signal processing is required to reconstruct the image for display.