Time-of-Flight Range Image Sensor

Time-of-Flight (TOF) Method

TOF range imaging is one of 3-D image capture methods and the range L is determined by sensing the roundtrip time of flight for the light.

Pixel Circuit for TOF Range Image Sensor

A pixel structure of the sensor employs single layer polysilicon gates on thick field oxide. Using these single layer polysilicon gates, the sensor achieves high-speed charge transfer essential for TOF range imaging like CCD and can divide signal charge depending on delay time into two floating diffusion (FD) in each pixel (x-x’ direction). small duty cycle for the transfer gates and light source control pulse and the charge draining structure (y-y’ direction) drastically reduce the effect of background illumination. Using this sensor, we can get a video rate (30fps) gray scale image and range image, simultaneous. The minimum range resolution at 30frames/s and the light pulse width of 25ns is 5.0mm. The resolution at 3frames/s, which corresponds to the averaging with 10 samples, is 1.7mm.

Pixel Circuit for TOF Range Image Sensor	Gray Scale Image	Range Image

Applications

Automobile, Robot vision systems, Security, Medical and so on.

References

1. S. Kawahito, et al.,"A CMOS time-of-flight range image sensor with gates-on-field-oxide structure", IEEE Sensors Journal, accepted, 2006.
2. I. A. H. Izhal, et al., "A CMOS time-of-flight range image sensor with gates on field oxide structure", Proc. 4th IEEE Int. Conf. Sensors, pp.141-144, Nov. 2005.
3. T. Ushinaga, et al., "A QVGA-Size CMOS Time-of Flight Range Image Sensor with Background Light Charge Draining Structure", Proc. IS&T/SPIE 18th Annual Symposium, Conf.# 6056, Session-1, 605604.1-8, San Jose, U.S.A., Jan.2006.
4. T. Sawada, et al., "A time-of-flight range image sensor with background light charge draining structure", Proc. 5th Int. Conf. Global Research and Education, vol. 1, pp. 67-74, 2006.