A time-to-first spike CMOS imager

A novel time-to-first-spike CMOS imager is presented, in which the timing of a single spike from each pixel encodes the illuminance of each pixel. This temporal representation of illuminance can widen the image sensor dynamic range to over 100 dB. To reduce power consumption, an asynchronous address-event readout technique is incorporated. The imager essentially implements a pixel-level A/D conversion and benefits from the continued process scaling to deep submicron levels. Results are shown from a 32×32 pixel imager fabricated in the 0.5 μm AMI process with measured dynamic range of 104 dB in one image. A test chip with one pixel and digital control logic has been fabricated through MOSIS using the TSMC 0.18 μm standard digital CMOS process. It has demonstrated the expected functionalities. A modified architecture is also proposed for a larger imager array.