Mark Allan Rhoades

US Patent:

48233307, Apr 18, 1989

Filed:

May 4, 1987

Appl. No.:

7/052128

Inventors:

Nelson K. Arter - Longmont CO
Mark G. Call - Longmont CO
Mark L. Rhoades - Longmont CO

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G11B 712

US Classification:

369 45

Abstract:

Error compensation in a feedback servo system. The feedback servo loop in, for example, a head positioning circuit in an optical disk data recording and retrieval system is provided with a compensation signal to correct for misalignment or other errors. The head in such a system must be dynamically maintained at a best focus position but, through use and transporting, the alignment of the head position error detecting system can be disturbed. In some cases, the loop circuit parameters may drift from their original values. To correct for errors introduced from such causes, the head is positioned at best focus and the focus error (head position error) signal is sensed. A correction signal is supplied which cancels out the sensed value while the system is operating.

US Patent:

48993271, Feb 6, 1990

Filed:

May 4, 1987

Appl. No.:

7/052115

Inventors:

Keith A. Bates - Lafayette CO
Russell A. Budd - Longmont CO
Millard A. Habegger - Boulder CO
Mark L. Rhoades - Longmont CO

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G11B 708
G11B 2100
H04N 576

US Classification:

369 45

Abstract:

Error correction in a feedback servo system. The feedback servo loop in, for example, a head positioning circuit in an optical disk data recording and retrieval system is provided with means for forcing the feedback signal to zero when the head is positioned at best focus as determined by a peak in the laser monitoring diode. The head in such a system must be dynamically maintained at a best focus position but, through use and transporting, the alignment of the head position error detecting system can be disturbed. In some cases, the loop circuit parameters may drift from their original values. To correct for errors introduced from such causes, the head is positioned at best focus and the focus error (head position error) signal is sensed. A correction system forces the sensed value to zero, e. g, by adjusting the gain of amplifiers used in the feedback loop.