Optical disc device and optical disc discriminating method
First Claim
1. An optical disc device comprising:
- a laser light source for radiating a laser light beam illuminated via an objective lens on a signal surface of an optical disc;
laser light intensity detection means for detecting the light intensity of the laser light radiated from said laser light source;
automatic power controlling means for controlling a laser output of said laser light source so that a detection output by said laser light intensity detection means will be constant for two laser light intensities corresponding to two types of optical discs having different numbers of signal surfaces and unique reflectivities;
return light detection means for detecting the return light of the laser light beam radiated by said laser light source and reflected by the signal surface of said optical disc;
focusing control means for displacing said objective lens along the optical axis responsive to the focusing error signals generated on the basis of a detection output of said return light detection means for controlling the focusing state of a beam spot of said laser light on the signal surface of said optical disc; and
controlling means for controlling a closed-loop gain of said automatic power controlling means to a gain in meeting with the reflectivity of the optical disc based on a detection output of said return light detection means which prevails when focusing is applied to the signal surface of the optical disc by said focusing control means, wherein said laser light intensity varies depending on the closed loop gain.
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Accused Products
Abstract
An optical disc device including a laser light source for radiating a laser light beam illuminated via an objective lens on a signal surface of an optical disc, a laser light volume detection unit for detecting the light volume of the laser light radiated from the laser light source, an automatic power controlling unit for controlling a laser output of the laser light source so that a detection output by the laser light volume detection unit will be constant, a return light detection unit for detecting the return light of the laser light beam radiated by the laser light source and reflected by the signal surface of the optical disc, a focusing control unit for displacing the objective lens along the optical axis responsive to focusing error signals generated on the basis of a detection output of the return light detection unit for controlling the focusing state of a beam spot of the laser light on the signal surface of the optical disc and a controlling unit for controlling the closed-loop gain of the automatic power controlling means to a gain in meeting with the reflectivity of the optical disc based on a detection output of the return light detection unit which prevails when focusing is applied to the signal surface of the optical disc by the focusing control unit.
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Citations
33 Claims
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1. An optical disc device comprising:
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a laser light source for radiating a laser light beam illuminated via an objective lens on a signal surface of an optical disc;
laser light intensity detection means for detecting the light intensity of the laser light radiated from said laser light source;
automatic power controlling means for controlling a laser output of said laser light source so that a detection output by said laser light intensity detection means will be constant for two laser light intensities corresponding to two types of optical discs having different numbers of signal surfaces and unique reflectivities;
return light detection means for detecting the return light of the laser light beam radiated by said laser light source and reflected by the signal surface of said optical disc;
focusing control means for displacing said objective lens along the optical axis responsive to the focusing error signals generated on the basis of a detection output of said return light detection means for controlling the focusing state of a beam spot of said laser light on the signal surface of said optical disc; and
controlling means for controlling a closed-loop gain of said automatic power controlling means to a gain in meeting with the reflectivity of the optical disc based on a detection output of said return light detection means which prevails when focusing is applied to the signal surface of the optical disc by said focusing control means, wherein said laser light intensity varies depending on the closed loop gain. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An optical disc device comprising:
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a laser light source for radiating a laser light beam illuminated via an objective lens on a signal surface of an optical disc;
laser light light detection means for detecting the light intensity of the laser light radiated from said laser light source;
automatic power controlling means for controlling a laser output of said laser light source so that a detection output by said laser light intensity detection means will be constant for two laser light intensities corresponding to two types of optical discs having different numbers of signal surfaces and unique reflectivities;
return light detection means for detecting the return light of the laser light beam radiated by said laser light source and reflected by the signal surface of said optical disc;
focusing control means for displacing said objective lens along the optical axis responsive to the focusing error signals generated on the basis of a detection output of said return light detection means for controlling the focusing state of a beam spot of said laser light on the signal surface of said optical disc; and
controlling means for controlling a closed-loop gain of said automatic power controlling means based on a detection output of said return light detection means which prevails when focusing is applied to the signal surface of the optical disc by said focusing control means, wherein said laser light intensity varies depending on the closed loop gain. - View Dependent Claims (10, 11)
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12. An optical disc device, comprising:
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a laser light source for radiating a laser light beam illuminated via an objective lens on a signal surface of an optical disc;
a monitor photodiode for detecting the light intensity of the laser light radiated from said laser light source;
an automatic power control circuit for controlling a laser output of said laser light source so that a detection output detected by said monitor photodiode will be substantially constant for two laser light intensities corresponding to two types of optical discs having different numbers of signal surfaces and unique reflectivities;
a reflected light photodetector for detecting light emitted from the laser light source and reflected by the signal surface of said optical disc;
a servo processor for displacing said objective lens along the optical axis responsive to focusing error signals generated on the basis of a detection output of said reflected light photodetector for controlling the focusing state of a beam spot of said laser light beam on the signal surface of said optical disc; and
a system processor for controlling a closed-loop gain of said automatic power control circuit based on a detection output of said reflected light photodetector which varies depending on the reflectivity of the optical disc and which prevails when focusing is applied to the signal surface of the optical disc by said servo processor, wherein said laser light intensity varies depending on the closed loop gain. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. An optical disc device comprising:
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a laser light source for radiating a laser light beam illuminated via an objective lens on a signal surface of an optical disc;
a monitor photodiode for detecting the light intensity of the laser light radiated from said laser light source;
an automatic power control circuit for controlling a laser output of said laser light source so that a detection output detected by said monitor photodiode will be substantially constant for two laser light intensities corresponding to two types of optical discs having different numbers of signal surfaces and unique reflectivities;
a reflected light photodetector for detecting light emitted from the laser light source and reflected by the signal surface of said optical disc;
a servo processor for displacing said objective lens along the optical axis responsive to focusing error signals generated on the basis of a detection output of said reflected light photodetector for controlling the focusing state of a beam spot of said laser light beam on the signal surface of said optical disc; and
a system processor for controlling a closed-loop gain of said automatic power control circuit based on a detection output of said return light photodetector which prevails when focusing is applied to the signal surface of the optical disc by said servo processor, wherein said laser light intensity varies depending on the closed loop gain. - View Dependent Claims (21, 22)
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23. A method for discriminating a type of an optical disc loaded in an optical disc device and controlling an output of a laser light source based on the discriminated disc type, comprising the steps of:
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radiating a laser light beam from said laser light source via an objective lens on a signal surface of said optical disc;
detecting an emitted light intensity of the laser light radiated from said laser light source;
controlling a laser output of said laser light source so that the detected light intensity will be substantially constant for two laser light intensities corresponding to two types of optical discs having different numbers of signal surfaces and unique reflectivities;
detecting a reflected light intensity of the laser light radiated from the laser light source and reflected by the signal surface of said optical disc;
displacing said objective lens along the optical axis responsive to focusing error signals generated on the basis of the detected reflected light intensity;
controlling the focusing state of a beam spot of said laser light on the signal surface of said optical disc; and
controlling a closed-loop gain based on the detected reflected light intensity which varies depending on the reflectivity of the optical disc and which prevails when focusing is applied to the signal surface of the optical disc, wherein said laser light intensity varies depending on the closed loop gain. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
determining the reflectivity of the optical disc from the signal level of the detected reflected light intensity; and
controlling the closed-loop gain based on the determined reflectivity of the optical disc.
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25. The method of claim 23, further comprising the steps of:
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discriminating the type of the optical disc based on the detected reflected light intensity; and
switching the closed-loop gain to a gain corresponding to the discriminated optical disc type.
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26. The method of claim 25, wherein said discriminating step includes the step of discriminating between a single-layer disc having a sole signal surface and a double-layer disc having two signal surfaces based on the detected reflected light intensity.
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27. The method of claim 23, further comprising the steps of:
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discriminating the type of the optical disc based on the focusing error signals during focusing searching of said objective lens; and
switching the closed-loop gain to a gain corresponding to the discriminated optical disc type.
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28. The method of claim 27, wherein the discriminating step includes the step of discriminating between a single-layer disc having a sole signal surface and a double-layer disc having two signal surfaces based on said focusing error signals.
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29. The method of claim 28, wherein said switching step includes the step of lowering the closed-loop gain if the discriminated disc type indicates the double-layer disc to a lower value than if the discriminated disc type indicates the single-layer disc.
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30. The method of claim 23, further comprising the steps of:
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discriminating between a double-layer disc having a first reflectivity and a single layer disc having a second reflectivity lower than said first reflectivity based on the focusing error signals during focusing searching of said objective lens; and
lowering the closed-loop gain if the discriminated disc type indicates the double-layer disc to a lower value than if the discriminated disc type indicates the single-layer disc.
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31. A method for discriminating a type of an optical disc loaded in an optical disc device and controlling an output of a laser light source based on the discriminated disc type, comprising the steps of:
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radiating a laser light beam from said laser light source via an objective lens on a signal surface of said optical disc;
detecting an emitted light intensity of the laser light radiated from said laser light source;
controlling a laser output of said laser light source so that the detected light intensity will be substantially constant for two laser light intensities corresponding to two types of optical discs having different numbers of signal surfaces and unique reflectivities;
detecting a reflected light intensity of the laser light radiated from the laser light source and reflected by the signal surface of said optical disc;
displacing said objective lens along the optical axis responsive to focusing error signals generated on the basis of the detected reflected light intensity;
controlling the focusing state of a beam spot of said laser light on the signal surface of said optical disc;
controlling a closed-loop gain of a power control circuit of said laser light source based on the detected reflected light intensity which prevails when focusing is applied to the signal surface of the optical disc, wherein said laser light intensity varies depending on the closed loop gain. - View Dependent Claims (32, 33)
discriminating between a single-layer disc having a sole signal surface and a double-layer disc having two signal surfaces based on the detected reflected light intensity; and
lowering the closed-loop gain if the discriminated disc type indicates the double-layered disc to a lower value than if the discriminated disc type indicates the single-layered disc.
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33. The method of claim 31, comprising the steps of:
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discriminating between a single-layer disc having a sole signal surface and a double-layer disc having two signal surfaces based on the detected reflected light intensity; and
switching the closed-loop gain to a gain associated with each signal surface.
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Specification