Method and apparatus for determining the rate of angular rotation of a rotating object

Abstract

A method and apparatus for determining the rate of angular rotation of a rotating object comprising directing a beam of substantially coherent electromagnetic radiation towards the rotating object (80); detecting speckles generated by electromagnetic radiation (60) scattered from the object; and determining the transit time of the detected speckles; wherein the field of electromagnetic radiation (60) scattered from the object is Fourier-transformed by an optical Fourier-transforming system (20); and subjective speckles (71) of the Fourier-transformed electromagnetic radiation (70) are detected in at least two detection regions (12, 13) positioned in a detector plan (9) substantially parallel with and located in or near the Fourier-plane (10) of the Fourier-transforming system (20).

Dependencies are inferred from the claim text.