A binary photodetector array for position sensing

Abstract The implementation and test results of a 16 × 16 CMOS photodetector array for position-sensing applications are presented. Unlike conventional position-sensitive detectors (PSDs), it can be used for simultaneous multiple spot detection with high accuracy. To decrease the signal-processing overhead characteristic of area arrays, binary detection and random access readout are used. The fill factor and pitch of the array are 30% and 50 μm, respectively. Spatial-quantization-limited position-sensing accuracy of 4.3 μm is achieved using a uniform spot of 280 μm in diameter, total signal power of about 8 nW and pulse width of 8 ms. At lower signal levels, the accuracy is decreased by the spatial noise caused by the mismatch of threshold-setting current mirrors operating in weak inversion. The array outperforms a typical largearea (~ 100 mm 2 ) lateral effect PSD (LEP) when a measurement bandwidth less than 10 kHz is used.

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