Varying the rate at which data appear on an optical disc rotated at a constant linear velocity to prevent unauthorized duplication of the disc

An optical disc to which data are recorded in the form of optically detectable patterns for subsequent access by a disc readback system having a motor configured to rotate the disc at a nominally constant linear velocity, a readback head assembly configured to transduce the optically detectable patterns and readback recovery circuitry configured to obtain frequency lock on a frequency of the optically detectable patterns, the disc comprising:

• a data placement zone to which first data are written to produce a first data rate as a frequency at which the first data pass the readback head assembly as the disc is rotated at a selected linear velocity;
• a velocity disruption zone adjacent the data placement zone to which second data are written to produce a second data rate as a frequency at which the second data pass the readback head assembly as the head is rotated at the selected linear velocity, wherein the second data rate is different from the first data rate;
• and
• a data rate profile zone to which information is stored in relation to variation between the first and second data rates to facilitate authentication of the disc by the readback system.

A method for writing data to an optical disc in the form of optically detectable patterns for subsequent access by a disc readback system having a motor configured to rotate the disc at a nominally constant linear velocity, a readback head assembly configured to transduce the optically detectable patterns and readback recovery circuitry configured to obtain frequency lock on a frequency of the optically detectable patterns, the method comprising steps of:

• (a) providing input data to be written to the disc;
• (b) modulating the input data to provide a data modulation signal at a nominal frequency;
• (c) selecting a data rate profile in relation to desired variation in frequencies at which different portions of the input data are to appear on the disc;
• and
• (d) using the data modulation signal to write the input data to the disc while varying at least a selected one of the nominal frequency of the data modulation signal and a linear velocity of the disc in relation to the selected data rate profile to prevent unauthorized duplication of the disc.

A system for writing data to an optical disc in the form of optically detectable patterns, comprising:

• a write assembly adjacent the disc;
• a motor configured to rotate the disc at a selected linear velocity;
• an encoder which modulates input data to form a data modulation signal at a nominal modulation frequency;
• and
• a control circuit, coupled to the motor and the encoder, which variably adjusts at least a selected one of the disc linear velocity and the modulation frequency in accordance with a data rate profile to write the input data to the disc, wherein the data rate profile is selected in relation to desired variation in frequencies at which different portions of the input data are to appear on the disc to authenticate the disc as an authorized copy.