| US 7,551,524 B2 | ||
| Methods and apparatus to compensate for power output variations over time | ||
| Kevin L. Colbum, Greeley, Colo. (US); D. Mitchel Hanks, Fort Collins, Colo. (US); Lawrence N. Taugher, Loveland, Colo. (US); Greg J. Lipinski, Loveland, Colo. (US); and Andrew L Van Brocklin, Corvallis, Colo. (US) | ||
| Assigned to Hewlett-Packard Development Company, L.P., Houston, Tex. (US) | ||
| Filed on Feb. 04, 2005, as Appl. No. 11/51,307. | ||
| Prior Publication US 2006/0176800 A1, Aug. 10, 2006 | ||
| Int. Cl. G11B 11/00 (2006.01) | ||
| U.S. Cl. 369—13.27 [369/47.53] | 55 Claims |
| 1. A method of compensating for variations in laser power output over time in a system using a laser to record visible marks
on an optical disc, the method comprising:
(a) applying a test light beam from the laser to the optical disc to determine a test value of an optical parameter;
(b) determining a difference between the test value and a predetermined reference value for the optical parameter; and
(c) adjusting the laser power output to compensate for the difference;
wherein the step of applying a test light beam comprises applying the light beam to a reflective surface on the optical disc
to generate a test SUM signal and wherein the reflective surface is more reflective at a visible light wavelength than at
a non-visible wavelength of the test light beam.
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