Patent ID: 7911912
Filing Date: 2011-03-22
Classification: G11B

Abstract:
1. An optical disc recording apparatus for generating a modulation signal having a signal level switched at a period which is an integral multiple of a basic period in accordance with main information and controlling an optical beam applied to an optical disc based on said modulation signal to successively form, on said optical disc, pits and lands or marks and spaces having lengths which are represented by integral multiples of a basic length corresponding to said basic period, wherein a sequence of data based on auxiliary information is modulated by a signal represented by a combination of a sequence of pseudo-random numbers and a predetermined periodic signal, and recorded traces of said pits or said marks are changed depending on the modulated sequence of data, thereby recording said auxiliary information on said optical disc, the optical disc recording apparatus comprising: a first modulation signal generating unit configured to generate a first modulation signal having a signal level switched at a period which is an integral multiple of said basic period in accordance with said main information; a second modulation signal generating unit configured to modulate said first modulation signal with a signal based on the sequence of data based on said auxiliary information; a recording beam modulating unit configured to modulate said optical beam with a signal output from said second modulation signal generating unit; and an optical system for applying said optical beam to said optical disc; said second modulation signal generating unit comprising: a pseudo-random number generating unit configured to generate a pseudo-random number; a periodic signal generating unit configured to generate said predetermined periodic signal, said periodic signal generating unit including a counter configured to count channel clock pulses output from a phase lock loop circuit, the counter being cleared by a frame clock pulse output from a synchronous detecting circuit, the counter supplying the most significant bit of the counter value as a toggle signal to an exclusive-OR circuit; an auxiliary information modulating unit configured to modulate the sequence of data based on said auxiliary information with a signal represented by a combination of the random number from said pseudo-random number generating unit and the predetermined periodic signal from said periodic signal generating unit; and a modulation signal processing unit configured to modulate said first modulation signal to slightly change the recorded traces of said pits or said marks, based on the modulated sequence of data from said auxiliary information modulating unit.