A 128×128 120dB 15us Latency Asynchronous Temporal Contrast Vision Sensor

This paper describes a CMOS vision sensor which is inspired by biological visual systems. Each pixel independently and in continuous time quantizes local relative intensity changes to generate spike events. These events appear at the output of the sensor as an asynchronous stream of digital pixel addresses. These address-events signify scene reflectance change and have sub-millisecond timing precision. The output data rate depends on the dynamic content of the scene and is typically orders of magnitude lower than those of conventional frame-based imagers. By combining an active front-end logarithmic photoreceptor running in continuous time with a self-timed switched-capacitor differencing circuit, the sensor achieves an array mismatch of 2.1% in relative intensity event threshold and a pixel bandwidth of 3 kHz under 1 klux scene illumination. Dynamic range is >120 dB and chip power consumption is 23 mW. Event latency shows weak light dependency and decreases to 15 us at >1 klux pixel illumination. The sensor is built in a 0.35u 4M2P process yielding 40x40 um pixels with 9.4% fill-factor. By providing high pixel bandwidth, wide dynamic range, and preciselytimed sparse digital output, this neuromorphic silicon retina provides an attractive combination of characteristics for low-latency dynamic vision under uncontrolled illumination with low post-processing requirements.