A flying-spot scanner used to study the electrical properties of semiconductor materials and devices is described. The instrument automatically deflects a collimated light beam in a raster pattern and focuses the raster on the photosensitive semiconductor surface. The electrical output from the semiconductor is amplified and used to form an image of the photoresponse of the sample on a cathode ray tube. The resolution of the system referred to the sample is about 5 μ. © 1968 The American Institute of Physics.