In this paper, a velocity measurement method using the spatialfilter is presented. Luminous emitance of the surface passing throughthe moving spatial filter and optical set is projected to the activearea of photo-detector. The velocity determination is based on thefrequency spectrum evaluation of the photo-detector output signal. Theformula for velocity computing is derived first. Then, correctness ofvelocity evaluation in dependence on the surface and measuring systemproperties is discussed.