High-performance photo detector for correlative feeble lighting using pixel-parallel sensing

We have developed a high-performance photo detector, which can detect a feeble projected light with pulse modulation in strong ambient light from other light sources. It is useful to expand the application field of the three-dimensional measurement system using a light-section method. A correlation circuit and a current-mode suppression circuit of constant illumination allow high sensitivity, high selectivity, and adaptive suppression of background illumination. A logarithmic-response circuit is employed to avoid saturation for wide dynamic ranges. The photo detector can quickly detect the modulated light by pixel-parallel sensing. It has advantages for some applications which require availability in various background illuminations and safe light projection for human eyes. The photo detectors have been developed and successfully tested. The high sensitivity under -18-dB signal-to-background ratio (SBR) is realized over the 47.2-dB dynamic range. The minimum SBR is -22.8 dB and the potential frame rate is 2000 fps. In addition, the photo detector shows high selectivity in a multiple-lighting system due to the suppression of orthogonally modulated light.