Source width insensitive optical position sensor

Several position sensors that achieve high-resolution position sensing based on moment calculation of the detected photocurrents from a sensing array have recently been described in the literature. These sensors generally have transfer functions that are independent of source intensity, but are dependent on source shape and size relative to the sensing arrays. This is detrimental in astronomical sensing applications where the sensing array may not be able to completely capture the diffuse source under observation, or where the source may be fluctuating with time. This paper describes a modified sensor system which decreases the errors due to source size variations by subtracting a normalizing current from each photocurrent before processing. The concept is verified using a commercial 1.2 /spl mu/m CMOS process.<
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