Patent ID: 7348543

Claim:
A method for measuring a rotation angle of a rotary shaft, the method comprising: a) providing an optical encoder assembly comprising a rotating optical disk with a pattern of transparent and absorbent sections, and a mirror patterned in a predetermined pattern; b) providing at least one optical guide means having a light entrance surface, a hollow inner space, a transparent peripheral wall configured to confine light rays within itself, and a terminal peripheral rim; c) directing an optical beam emitted from a light source into the light entrance of said optical guide means such that light rays of said beam are propagated within the transparent peripheral wall of the optical guide means, emitted from its terminal peripheral rim, distributed over said rotating optical disc to overlie its pattern and propagated through its transparent sections to become incident on said predetermined pattern on said mirror; and d) translating the amount of light reflected by the said mirror and propagated backwards through the said rotating optical disk into the said optical guide means to a signal indicative of said rotation angle.