Abstract: An apparatus for the measurement of optical sensor performance includes a light emitter, a focuser and a controller. The optical sensor comprises a plurality of pixels, which may be arranged as a pixel array. The light emitter projects a light spot onto the sensor. The focuser focuses the light spot onto a specified portion of the sensor in accordance with a control signal. The controller analyzes an output signal of the optical sensor, and generates the control signal to an accuracy substantially confining the light spot to a single pixel in accordance with the analysis.