Effects Of A Shading Band In The Data Path Of An Optical Drive

Efforts to improve the density of data recorded onto optical media have included shaping the function of the optical system. Several authors have described various methods for shaping th transfer e transfer function. Reference 1 contains a summary of the various techniques and plots of the transfer functions. In this paper, we describe the effects of a simple shading band in the data path of an optical drive. One effect of the shading band is to shape the transfer function of the optical system. This is similar to the technique of applying electronic equalizing filters for better frequency response. A second effect of the shading band is to decrease the noise associated with the laser and the medium. In our work, we implement a shading band in a commercial optical disk drive. The relevant parameters to this study are: shading band width = 30% of the pupil diameter, medium velocity = 5.7 m/s, NA = 0.55, and λ = 0.78 nm. We used a standard 130 mm magneto-optic disk with a plastic substrate. The following sections briefly describe the theory associated with using the shading band and the results of our experiments.