Patent ID: 7120097

Claim:
A radiation beam recording system for exposing a photoresist master disc having a photoresist layer formed over a substrate for making a hybrid optical recording disc having a read only (ROM) portion and a writable portion, comprising: a) means for modulating an intensity of a laser beam having a wavelength selected to provide activating radiation to expose a pattern in the photoresist layer formed over the substrate of the master disc between a lower intensity for exposing a groove in the photoresist layer and a higher intensity for exposing the groove and a pattern of depressions in the groove in the photoresist layer; b) means for frequency-modulating the intensity-modulated beam with a wobble-frequency to cause the exposed groove to be a continuously frequency-modulated wobbled groove; c) a modulation control system for controlling the intensity modulation and the frequency modulation of the beam to form a continuously frequency-modulated exposed groove with exposed depressions in the ROM portion of the exposed groove, said continuously frequency-modulated exposed groove having one segment for storing and erasing data and another segment for storing read only data; d) means for rotating the photoresist master disc during exposure to the laser beam, and means for radially translating the master disc so that the laser beam incident on the photoresist layer will trace a continuous exposed spiral groove; and e) wherein said modulation control system includes a clock, an ATIP generator connected to the clock and operative to generate a frequency-modulating ATIP signal, an EFM generator connected to the clock and operative to generate an intensity-modulating EFM signal in correspondence with digital data input signals, and means for controlling temporal relationships between and among the ATIP generator and the EFM generator so that respective ATIP signals and EFM signals are temporally correlated to provide concurrent operation of the intensity- and frequency modulation of the laser beam, the means for controlling temporal relationships include a first logic circuit means for creating flag pulses directed from the EFM generator to the ATIP generator, or vice versa, and a second logic circuit means for creating flag pulses directed from the ATIP generator to the EFM generator, or vice versa.