A system for determining a distance to a target object or a displacement of a target object monitors electrical characteristics of a semiconductor laser aimed at the object. Light emitted from the laser is reflected from a surface of the object back into the laser. The amount of reflected light reaching the laser affects electrical characteristics of the laser. Because the amount of reflected light reaching the laser depends on the distance to the target object, the electrical characteristics of the semiconductor laser provide an indication of the distance to the target object. Also, a change in the electrical characteristics can be used to determine an amount of displacement of a target object. A system embodying the invention could also include an optical detector array which can be focused on a target object by monitoring electrical characteristics of one or more semiconductor lasers. A plurality of semiconductor lasers could be arranged in a two dimensional or a three dimensional array such that the semiconductor lasers are located at different distances from a target surface. By monitoring the electrical characteristics of the plurality of semiconductor lasers, one can determine both an amount and a direction of a displacement of a target object relative to the semiconductor laser array.