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US 5,499,230 AGranted
Optical disk apparatus
AssigneeFujitsu Limited
InventorShigenori Yanagi
Life of this patent
Estimating the term…
Abstract
Signals from two light receiving sections of a 2-split photodetector are separated to the AC coupled high frequency side and the DC coupled low frequency side. Both signals are added, thereby forming a tracking error signal of a wide band. A tracking error signal is independently formed with respect to the high frequency side and can be also added to the signal on the low frequency side.
Claims22
An optical disk apparatus comprising:
- a reading optical unit for irradiating a reading beam onto an optical disk medium and for extracting a return light reflected and diffracted by a track portion of said medium;
- a photodetector having at least two-split light receiving sections, each for converting the return light extracted by said reading optical unit into a detection signal;
- a first circuit for AC coupling each of said detection signals from said two light receiving sections provided for said photodetector and separating a band on a high frequency side, for individually amplifying said detection signals in a frequency band in a range from a predetermined first cut-off frequency to a predetermined ultra high frequency, for adding the amplified signals after that, and for forming a high frequency signal that is used for demodulation of read data;
- and
- a second circuit for DC coupling each of the detection signals from said two light receiving sections provided for said photodetector, for individually amplifying said detection signals in a frequency band in a range from DC to said first cut-off frequency, for adding the detection signals individually amplified by said first circuit after that, for producing two addition signals each having a frequency band in a range from a DC component to an ultra high cut-off frequency higher than said first cut-off frequency, for performing a subtraction between said two addition signals, and for forming a tracking error signal.
2 more elements
An optical disk apparatus comprising:
- a reading optical unit for irradiating a reading beam onto an optical disk medium and for extracting a return light reflected and diffracted by a track portion of said medium;
- a photodetector having at least two-split light receiving sections, each for converting the return light of said reading optical unit into a detection signal;
- a first circuit for AC coupling each of said detection signals from said two light receiving sections provided for said photodetector and also separating a band on a high frequency side, for individually amplifying said detection signals in a frequency band in a range from a predetermined first cut-off frequency to a predetermined ultra high frequency, for adding the amplified signals after that, and for forming a high frequency signal that is used for demodulation of read data;
- a second circuit for DC coupling each of the detection signals from said two light receiving sections provided for said photodetector, for individually amplifying said detection signals in a frequency band in a range from DC to a second ultra high cut-off frequency higher than said first cut-off frequency, for performing a subtraction between said two detection signals after that, and for forming a first tracking error signal;
- and
- a third circuit for forming a differential signal from said two detection signals derived by the amplification of said first circuit, for adding said first tracking error signal from said second circuit to said differential signal after that, and for forming a second tracking error signal.
3 more elements
Dependencies are inferred from the claim text.