Patent ID: 7027196

Claim:
A tilt servo apparatus, comprising: means for generating a reconstructing beam and projecting the reconstructing beam onto a digital storage medium to generate a reflected beam reflected by the digital storage medium tilted within a tilt range; a holographic plate for storing a first and a second hologram, wherein the first hologram is an interference pattern between a first tilt reference beam projected at a first tilt reference angle and a first tilt signal beam projected at a first tilt signal angle and the second hologram is an interference pattern between a second tilt reference beam projected at a second tilt reference angle and a second tilt signal beam projected at a second tilt signal angle, and diffracting the reflected beam with the first and the second hologram to generate a first and a second holographic diffracted beam, respectively; a first and a second detector for generating a first and a second detected signal by detecting the first and the second holographic diffracted beam, respectively; means for generating a tilt servo signal based on the first and the second detected signal; and means for compensating a tilt error of the digital storage medium by using the tilt servo signal.