New types of position sensitive device for accurate sensing

A PSD (semiconductor image position sensitive device) is useful for position sensing in an automation system, robotics, and so on. In present PSDs, the produced photocurrent flows into the dividing resistance and the bright spot position is calculated from the output currents of dividing resistance. When the existing background lights surround the target image, their photocurrent affects the image position calculation, and sensing errors are produced. We propose a new type of PSD in which the surrounding photocurrent produced by background lights can be subtracted and do not flow into the dividing resistance. The subtractions are made from individual photosensitive elements through the ideal diode which can prevent the interaction between photocurrent. In addition, for simplicity in manufacturing, a different type of PSD without the interaction prevention diode is also considered. We have performed computer simulations and it was confirmed that the proposed method would be useful. In addition, we also propose a new type of PSD which can detect the position of a black target image on light background by adopting a similar method.