A highly sensitive, low-power, and wide dynamic range CMOS digital pixel sensor

This paper proposes a new pixel-level light-to-frequency converter (LFC) that operates at a low supply voltage, and also offers low power consumption, low area, wide dynamic range, and high sensitivity. By using the proposed LFC, a digital pixel sensor (DPS) based on a pulse-frequency-modulation (PFM) scheme has been designed and fabricated. The prototype chip, including an array of 16 × 16 DPS with pixel size of 23 × 23 μm2 and 33.5% fill factor, was fabricated in a standard 180-nm CMOS technology. Experimental results show that the pixel operates with maintained output characteristics at supply voltages down to 1 V. The pixel sensor achieves an overall dynamic range of more than 142 dB and consumes 103 nW per pixel at a supply voltage of 1 V at room light intensity. The sensitivity of the LFC is very high at the lower end of the light intensity compared to the higher end which enables the ability to capture clear images.