Abstract: Receiver circuits are provided for detecting a target light source. The circuits include a photocell arranged to detect light impinging thereupon, and a biasing circuit that maintains a constant reverse voltage across, the photocell irrespective of the photocell output. This maintains the capacitance of the photocell at a substantially constant value, and results in faster response times from the photocell. Further, the present invention provides circuits for effectively removing ambient conditions such as daylight from the output. Also, the present invention reduces the amount of signal loss between the photocell output and an amplifier due to loading at the input stage of the amplifier.

Abstract: A light detection system is provided including a switching circuit connected to an inductor shunted across a photoelectric cell and operative to switch between a light detection state and a charge storage state, wherein the light detection state causes a majority of current flowing through the inductor to bypass the charge storage circuit, and wherein the charge storage state causes a majority of current flowing through the inductor to pass through the charge storage circuit. In one embodiment of the present invention, the switching circuit is changed to the light detection state during a first period of time during which the laser beam is in the vicinity of the photoelectric cell and to the charge storage state during a second period of time during which the laser beam is remote from the photoelectric cell.