Position sensitive detection system in a read-only optical head-a novel approach

A proposal for a novel detection system is presented for the readout of a ROM optical disk system. This system has been designed for fast access by reducing the mass of the moving head to that of a lens array which is used for both focus and tracking, all other components remaining fixed. The lens array is required to move a maximum of 1 mm in the radial direction at any time. The detection system uses two pairs of position sensitive detectors and two rows of multiple light sources. An LCD shutter placed in front of the detectors allows only one spot of light to be incident on them at any one time. Component count of the system is kept to a minimum using finite plastic conjugate lens arrays (FPLAs), thereby reducing the optical component count to two pairs of objective lens arrays, two pairs of astigmatic lens arrays and a half silvered beam splitter. By using this system it is hoped that access times will be reduced considerably. Furthermore, using the constant angular velocity (CAV) method for data retrieval, the access time may be reduced to that of current magnetic hard disk system