An Enhanced Dynamic-Range CMOS Image Sensor Using a Digital Logarithmic Single-Slope ADC

Many kinds of wide-dynamic-range (DR) CMOS image sensors (CIS) have been developed, such as a multiple sampling, a multiple exposure technique, etc. However, those techniques have some drawbacks of noise increasing, large power consumption, and huge chip area. In this brief, a new digital logarithmic single-slope analog-to-digital converter (SS-ADC) with a digital counter is described. Since the proposed scheme is easily implemented with a simple algorithm, we can reduce power consumption and chip area drastically. Further, the logarithmic SS-ADC enhances the DR by 24 dB. The proposed ADC, which has been fabricated using a 0.13-mu m CIS process, achieves a signal-to-noise-plus-distortion ratio of 57.6 dB at 50 kS/s.