Abstract: The present invention is directed to a new and improved active translation sensor which includes a first member having a fixed transmission grating, a second member having a movable linear array of light-emitting diodes disposed juxtaposition relationship with respect to one side of the fixed transmission grating, the second member being movable with respect to the other, electrical circuitry is being provided for successively applying electrical energy to each of the light-emitting diodes in a cyclical manner, a photodetector disposed on the other side of the fixed transmission on grating for detecting light transmitted through the grating, a phase detector for receiving a first signal corresponding to the phase of the circuitry for successively applying the electrical energy to the light-emitting diodes and second signal corresponding to the light detected by the photodetector and outputting a signal corresponding to the phase difference between the two signals, thereby indicating the relative linear positi