We present a novel self-powered chip to detect the direction of incident light. This chip directly provides digitized output without the need of any off-chip power supply or optical or mechanical components. The chip was implemented in a standard 0.5 μm CMOS process. A microscale metal baffle was created by stacking all metal layers, contacts, and vias available in the process to produce on-chip shadowing. N-well/p+ photodiode arrays are located on both sides of the baffle to sense light. The photocurrent generated by a photodiode depends on the size of the photodiode and the shadowing. The shadowed area depends on the incident angle of the light. A current mirror circuit is used to compare the currents generated by the photodiodes on the opposite sides of the baffle and, consequently, provide a digital signal to indicate the incident light angle. Compared with the ideal linear digital light-angle detector with the same resolution, the presented sensor achieved the maximum error of only 2 deg over 110 deg test range.
© 2014 Optical Society of America
Original Manuscript: January 29, 2014
Revised Manuscript: March 23, 2014
Manuscript Accepted: March 27, 2014
Published: April 21, 2014
Hongyi Wang, Tao Luo, Zhijian Lu, Hongjiang Song, and Jennifer Blain Christen, "CMOS self-powered monolithic light-direction sensor with digitalized output," Opt. Lett. 39, 2618-2621 (2014)