Apparatus for determining the velocity and direction of a moving object, the apparatus comprising: a coherent light (L) source arranged to generate an incident beam (B) of coherent light; an optical imaging system arranged to receive light reflected from a moving object passing through the incident beam and to focus the reflected light into a magnified image of the moving image; a first optical mask (M) through which the magnified image is projected, the mask having a first region of alternating opaque and non-opaque areas having a first spacing and second region of alternating opaque and non-opaque areas having a second spacing different from the first spacing; a first light detector (D) arranged to receive the light signal transmitted through the optical mask, the light signal comprising a series of pulses, and to calculate the velocity and direction of the moving object as a function of the pulse frequency and the spacing of the opaque areas of the optical mask.