A new method for measuring plural light-spot positions in a spatially continuous manner using a sensor array

Optical measurement systems often need to detect the positions of plural li ght spots illuminated by various types of light sources. The applications u sing these systems usually require the measurement performance to be fast, of high accuracy and capable of simultaneously detecting plural points. In this paper, we propose a new method for the measurement of plural light-spo t positions that satisfies all three of the requirements listed above. The basic principle of the method is to detect which of the sensor elements pro duces the peak value and to calculate the actual peak positions of the ligh t spot by employing an analogue interpolating circuit. We have designed and built a prototype position-sensor system that implements the proposed meth od. The experimental results are as follows: (i) the relative error is at m ost 1.6%; (ii) the sampling time is 9.5 mu s times the number of detected s pots; and (iii) the proposed method is insensitive to background light. In addition, with this method one can measure other properties with physical s pot-like positions such as pressure and ultrasound.