Computer simulations of effects of disk tilt and lens tilt on push-pull tracking error signal in an optical disk drive

We quantify the effects of disk tilt and objective lens tilt on the push-pull tracking error signal of an optical disk data storage system. For a grooved disk, such as a recordable compact disk that operates at a laser wavelength of λ, it is found that disk tilt produces a tracking offset of 0.05λ per degree of tilt, whereas objective lens tilt produces an offset of 0.012λ per degree of tilt. The amplitude of the tracking error signal decreases by 2.5% at the disk tilt angle of 0.3° and by 5% at the objective lens tilt of 0.3°. We achieved these simulations with the computer program DIFFRACT, which performs a combination of diffraction and ray-tracing calculations through the entire optical path, from the light source to the detectors.