Tracking control system for use in an optical reading apparatus

• US 5,060,216 A
• Filed: 10/01/1990
• Issued: 10/22/1991
• Est. Priority Date: 04/25/1990
• Status: Expired due to Term

• Current Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Original Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Inventors: Nishitsuka, Mitsuru, Suzuki, Toshio
• Primary Examiner(s): Envall, Jr., Roy N.
• Assistant Examiner(s): Tran, Thang V.
• Application Number:
  US07/591,176
• Time in Patent Office: 386 Days
• Field of Search: 369/44.41, 369/44.42, 369/44.34-44.39, 369/124, 369/109, 369/32, 369/44.14, 250/201.4, 250/201.5
• US Class Current: 369/44.41
• CPC Class Codes: G11B 7/0906 Differential phase difference systems
• CPC Class Codes: G11B 7/0941 Methods and circuits for servo gain or phase compensation during operation for initialising servos G11B7/0945
• CPC Class Codes: G11B 7/0948 specially adapted for detection and avoidance or compensation of imperfections on the carrier, e.g. dust, scratches, dropouts G11B7/095 takes precedence

Abstract

In the tracking control unit of an optical information reading apparatus to perform "Heterodyne Method", electric signals from the respective quadrant-separated subdetectors are inputted to a first adder to obtain a reference sum total signal whose phase is 0°. Regarding phase difference, the sum total signal is compared with a first electric signal from an arbitrary one of the quadrant-separated subdetectors and a second electric signal from the other of the subdetectors located in the diagonal relationship with respect to the arbitrary subdetector, respectively, to produce a first and a second phase compared result signals which are added to each other by a second adder whereby a precise tracking control can be attained irrespective of the existence of any scratch or stain.

Claims

1. In an optical information reading apparatus comprising light beam irradiation means for irradiating a light beam onto a signal track on an information recording surface of an information recording medium, photo detector means including quandrant-separated subdetectors for applying photoelectric conversion to a reflected light beam from said information recording surface to output electric signals, and tracking control means for conducting a follow-up control of an irradiation position onto said track of the light beam from said light beam irradiation means on the basis of said electric signals,

the improvement in which said tracking control means includes:

a first adder for adding all electric signals outputted from said quandrant-separated subdetectors;

a first phase comparator for making a phase comparison between a first electric signal outputted from one of a pair of subdetectors located at diagonal positions of said quandrant-separated subdetectors of said photo detector means and a sum total signal of electric signals outputted from said first adder to output a first phase compared result signal;

a second phase comparator for making a phase comparison between a second electric signal outputted from the other of subdetector located at said diagonal positions and said sum total signal to output a second phase compared result signal; and

a second adder for adding said first and second phase compared result signals to output a tracking control signal.

2. An optical information reading apparatus as set forth in claim 1, wherein said first adder outputs a radio frequency signal for information recorded on an optical disk.

3. A optical information reading apparatus as set forth in claim 1, wherein said tracking control means includes a waveform shaping circuit for shaping waveforms of said sum total signal and said first and second electric signals.

4. In an optical information reading apparatus comrpising light beam irradiation means for irradiating a light beam onto a signal track on an inforamtion recording surface of an information recording medium, photo detector means including quadrant-separated subdetectors for applying photoelectric conversion to a reflected light beam from said information recording surface to output electric signals, and tracking control means for conducting a follow-up control of an irradiation position onto said track of the light beam from said light beam irradiation means on the basis of said electric signals,

the improvement in which said tracking control means includes:

a first adder for adding all electric signals outputted from said quandrant-separated sub detectors;

a first phase comparator for making a phase comparison between a first electric signal outputted from one of a pair of subdetectors located at diagonal positions of said quandrant-separated subdetectors of said photo detector means and an adjacent sum signal of electric signals outputted from a pair of adjacent subdectectors of said quadrant-separated subdetectors to output a first phase compared result signal;

a second phase comparator for making a phase comparison between a second electric signal outputted from the other of said subdetectors located at said diagonal positions and said adjacent sum signal to output a second phase compared result signal; and

a second adder for adding said first and second phase compared result signals to output a tracking control signal.

5. An optical information reading apparatus as set forth in claim 4, wherein said first adder outputs a radio frequency signal for information recorded on an optical disk.

6. An optical information reading apparatus as set forth in claim 4, wherein said tracking control means includes a waveform circuit for shaping waveforms of said adjacent sum signal and said first and second electric signals.