Optical scanning system with wavelength shift correction

Claim 1

An optical scanning system including a spinner having formed thereon at least one plane linear diffraction grating having a constant grating period d, a stationary wavelength compensation diffraction grating having properties identical to said grating formed on said spinner surface, said stationary grating placed in a plane parallel and in optical alignment with said spinner grating, a collimated reconstruction light source of wavelength λ r which provides a beam of light directed at an angle of incidence θ i onto said compensation grating, said grating diffracting said beam at a diffraction angle of θ d , said incidence angle θ i ≃θ d ≃45°, and the ratio of λ r to spacing d having a value between 1 and 1.618, means for rotating said spinner so that the spinner grating rotates through some rotation angle and diffracts a portion of the incident light at diffraction angle θ d , and optical means to focus said diffracted beams as a linear scan line on an image plane.