Data Sampling in an Optical Storage Device Having Focus Dither
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
A low cost optical storage device, using removable optical storage media, such as a multitrack disk or card, is constructed and arranged to provide nominal focus of a detector head on the media. The head is moved back and forth, i.e., dithered, at a known high frequency in the direction of its optical axis, so as to bring the head into true media focus a number of times for each media track data cell. A detector responds to the magnitude of the energy reflected from the media in order to determine when the head is in focus on the media. The binary (Image Omitted) data content of each data cell is sampled only when the head is in focus. A tracking servo (not shown) is provided to insure that the head follows the media track being read. However, a focusing servo is not necessary. In Fig.