Patent ID: 7110120

Claim:
A movement-direction determination apparatus, comprising: a coherent light source for irradiating a light beam containing linearly-polarized light onto a moving object having a light scattering surface; converging means, located between the coherent light source and the light scattering surface, for converging the irradiated coherent light beam; a λ/4 wave plate located between the coherent light source and the light scattering surface; a light splitter for splitting scattered light reflected from the light scattering surface into a plurality of beams; and a spatial filter detector for detecting the split beams with respective predetermined phase differences, wherein the beam from the coherent light source is irradiated onto the light scattering surface through the converging means and the λ/4 wave plate, and the scattered light reflected from the light scattering surface is introduced to the spatial filter detector through the beam splitter.