Peter J Spyra

US Patent:

54368804, Jul 25, 1995

Filed:

Jan 10, 1994

Appl. No.:

8/179476

Inventors:

Clarke K. Eastman - Rochester NY
Gerald J. Smart - Penfield NY
Peter J. Spyra - Churchville NY

Assignee:

Eastman Kodak Company - Rochester NY

International Classification:

G11B 700

US Classification:

369 54

Abstract:

The present invention provides an apparatus and method for controlling laser power in an optical recording system. A recording system in accordance with the present invention includes an optical source for supplying an incident write signal to an optical medium, such that data may be recorded on the medium during an incident write pulse as a mark having a distinct reflectivity; a detector for detecting a reflection the incident write signal from the medium to provide a reflected write signal; a generator for generating a mark formation effectiveness signal from a reflected write pulse in the reflected write signal, to provide an indication of the quality of the mark; an error signal generator for generating an error signal from the mark formation effectiveness signal and a target value of the mark formation effectiveness signal; and a controller for controlling a write power level of the optical source by providing a partial correction of variation in the error signal. The quality of data recorded in the presence of certain types of system degradations, such as laser defocus and optical media tilt, is improved. The present invention also provides techniques for determining write power control voltage and error signal voltage limits, and updating the limits using an incident write signal optical detector.

US Patent:

54467160, Aug 29, 1995

Filed:

Jan 10, 1994

Appl. No.:

8/179394

Inventors:

Clarke K. Eastman - Rochester NY
James A. Perconti - Rochester NY
Gerald J. Smart - Penfield NY
Peter J. Spyra - Churchville NY

Assignee:

Eastman Kodak Company - Rochester NY

International Classification:

G11B 700

US Classification:

369 54

Abstract:

The present invention provides an apparatus and method for controlling laser power in an optical recording system in the presence of multiple system degradations. A recording system in accordance with the present invention includes an optical source for supplying an incident write signal to an optical medium, such that data may be recorded on the medium during an incident Write pulse as a mark having a distinct reflectivity; a structure for detecting a reflection of the incident write signal from the medium to provide a reflected write signal; means for generating a mark formation effectiveness signal from a reflected write pulse in the reflected write signal, to provide an indication of the quality of the mark; means for generating an error signal from the mark formation effectiveness signal and a target value of said mark formation effectiveness signal; and means for controlling a write power level of the optical source by providing a partial correction of a first type of variation in the error signal and a full correction of a second type of variation in the error signal. The first type of variations may be due to high frequency system degradations such as laser defocus and optical media tilt, while the second type of variation may be due to low frequency variations, such as changes in optical source wavelength or media sensitivity.