Integrated CMOS Sensor Array for Optical Heterodyne Phase Sensing

A heterodyne interferometric CMOS 8 × 8 phase sensor array was developed to measure the spatial phase distribution of an optical wavefront. This sensor is suitable for measuring rapidly changing surface profiles and characterizing fast turbulence. Using an acousto-optic modulation frequency of 80 MHz and beat frequency of 10 kHz, the system calculates 8-bit phase data at each location in the array at a rate equal to the beat frequency. The phase computation is performed locally, digitized, and stored in 8-bit SRAM. Implemented in a 0.5-μm 2P3M CMOS process, the measured RMS phase error is 1.49^° (1 LSB) and mismatch has σ = 4.76^° (3.4 LSB). Experimental results, in agreement with theory, validate the proposed approach.