Method and apparatus for pre-compensation in an optical disc

DETAILED DESCRIPTION An improved method and apparatus for modulating a write beam signal in an optical data recording system is disclosed.
In a preferred embodiment, the amplitude of a write signal used in a write beam modulator is varied over the time during which the beam is applied.
In another preferred embodiment the time over which the write beam is applied is varied from a desired playback time such that actual playback time corresponds well with desired playback time.
In most preferred embodiments the amplitude and timing of the write signal are varied in combination.
The variations are designed to provide optimal playback response from an optical disc or the like.
In some embodiments the variations are user programmed to account for, for example, a specific media type or for particular recording conditions.
This is accomplished through the use of an array of switches or a computer program which is used to enter values in a memory register.
The memory register may be, for example, an EPROM.
In alternative embodiments the variations are controlled through the use of a ROM containing a specific pre-compensation characteristic.
The ROM may in some embodiments be a plug-in device such that the user may choose among a variety of pre-compensation characteristics.
Accordingly, in one embodiment the invention comprises signal generation means, the signal generation means providing first signals representative of signals of a first and a second state for first time periods, the first time periods substantially equal to desired times for playback of marks on a storage media; and means for adjusting the signals to provide output signals of second time periods, the output signals driving a write beam for formation of optically-detectable marks on the storage media, the optically-detectable marks providing a response to a read beam of substantially the desired playback times.
In an alternative embodiment the invention includes signal generation means, the signal generation means providing first signals of first and second states for first time periods; and means for adjusting the first signals to provide output signals of at least first, second, and third states, the output signals driving a write beam for formation of optically-detectable marks on a storage media, the optically-detectable marks providing a response to a read beam of substantially desired playback times