Tracking error signal detector
First Claim
1. An apparatus for detecting a tracking error signal from recorded bit information of a high density optical record carrier on which a laser beam is emitted to a data track area to produce a reflection beam carrying the recorded bit information on the optical record carrier, said apparatus comprising:
- a divided photodetector having a first divided portion and a second divided portion disposed in a light path of the reflection beam from the optical record carrier, said divided photodetector producing a first photodetector signal from said first divided portion and a second photodetector signal from said second divided portion, wherein said first photodetector signal and said second photodetector signal both contain the recorded bit information;
a phase comparison means for detecting a phase difference between said first and said second photodetector signals, and for producing a phase difference signal which is a tracking error signal;
a first low-order phase lead filter located between said first divided portion and said phase comparison means for amplifying a high frequency component of said first photodetector signal and shifting a phase of the high frequency component of said first photodetector signal; and
a second low-order phase lead filter located between said second divided portion and said phase comparison means for amplifying a high frequency component of said second photodetector signal and shifting a phase of said high frequency component of said second photodetector signal in substantially a same amount and in a same direction as the high frequency component of said first low-order phase lead filter;
wherein said first and second low-order phase lead filters are characterized by a transfer function G=Go (1+jf/f5), wherein Go is a gain and f5 is a cut-off frequency which is set at an approximate middle of a frequency band of the recorded bit information.
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Accused Products
Abstract
An apparatus for outputting a tracking error signal based on the time change in the intensity distribution of a laser beam diffracted by the data pits is provided for an optical reproduction system using an optical record carrier on which data is recorded with a high recording density. The photodetector is divided orthogonally into four parts, and boost filters having identical characteristics are disposed for the output signal of one pair of diagonally located photodetector elements and for the output signal of the other pair of diagonally located photodetector elements. The detection gain of the short mark reproduction signal can thus be increased above the detection gain of the long mark reproduction signal to prevent the loss of short marks and improve the S/N ratio of the tracking error signal.
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Citations
5 Claims
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1. An apparatus for detecting a tracking error signal from recorded bit information of a high density optical record carrier on which a laser beam is emitted to a data track area to produce a reflection beam carrying the recorded bit information on the optical record carrier, said apparatus comprising:
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a divided photodetector having a first divided portion and a second divided portion disposed in a light path of the reflection beam from the optical record carrier, said divided photodetector producing a first photodetector signal from said first divided portion and a second photodetector signal from said second divided portion, wherein said first photodetector signal and said second photodetector signal both contain the recorded bit information; a phase comparison means for detecting a phase difference between said first and said second photodetector signals, and for producing a phase difference signal which is a tracking error signal; a first low-order phase lead filter located between said first divided portion and said phase comparison means for amplifying a high frequency component of said first photodetector signal and shifting a phase of the high frequency component of said first photodetector signal; and a second low-order phase lead filter located between said second divided portion and said phase comparison means for amplifying a high frequency component of said second photodetector signal and shifting a phase of said high frequency component of said second photodetector signal in substantially a same amount and in a same direction as the high frequency component of said first low-order phase lead filter; wherein said first and second low-order phase lead filters are characterized by a transfer function G=Go (1+jf/f5), wherein Go is a gain and f5 is a cut-off frequency which is set at an approximate middle of a frequency band of the recorded bit information. - View Dependent Claims (2, 3, 4, 5)
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Specification
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- Resources
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Current AssigneeMatsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
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Original AssigneeMatsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
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InventorsKanda, Yoshihiro, Ishibashi, Hiromichi, Yamaguchi, Osamu
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Primary Examiner(s)Psitos, Aristotelis M.
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Assistant Examiner(s)FABER, ALAN
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Application NumberUS08/561,920Time in Patent Office1,028 DaysField of Search369/44.41, 369/44.35, 369/44.29, 369/44.36, 369/124, 369/50, 369/59, 250/202, 324/76.77, 324/76.82US Class Current369/44.35CPC Class CodesG11B 7/0901 for track following only G1...G11B 7/0941 Methods and circuits for se...
