JP2009151880A - Optical disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk unit which can execute good recording/reproducing of information continuously even when an objective lens becomes tainted. <P>SOLUTION: The optical disk unit comprises a photodetector 13 for detecting return light from an optical disk D, and a signal level detector 3 for detecting a signal level of an RF signal photoelectrically converted by the photo detector 13, and compares the level of the RF signal with an initial value of the signal level of the RF signal corresponding to the return light from the optical disk D detected by the photodetector 13 when the objective lens 11 is not tainted to output a correction signal for raising a target current to supply an semiconductor laser 9 from an APC circuit 6 only when the signal level is smaller than the initial value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus capable of continuously reproducing good information even when the objective lens of an optical pickup is soiled or the objective lens changes over time.

  An optical disc apparatus detects a return light reflected by irradiating an optical disc with laser light by using a photodetector to generate an RF (Radio Frequency) signal, and performs information reproduction and servo processing based on the RF signal. . However, when the surface of the objective lens in the optical pickup used in this optical disk device is dirty or when the objective lens changes over time, information cannot be reproduced satisfactorily. This countermeasure is described in Patent Document 1.

  That is, in Patent Document 1, an average value of gain adjustment values for an RF signal reproduced by an optical pickup is obtained, the gain average value is stored in a memory, and a defective state of the optical pickup is detected based on the gain average value. Along with this, it is described that a defect state is notified to a user before an information reading error occurs by detecting a defect state of the optical disk based on a gain adjustment value obtained when the optical disk is reproduced. .

JP 2004-206766 A

However, since the surface of the objective lens is gradually soiled, it is often not known until the stain of the objective lens is discovered. In Patent Document 1, the user is notified of a defective state before an information reading error occurs. Since the countermeasures are being sought, it is necessary for the user to cope with optical pickup defects and optical disk defects, which is bothersome for the user.
The same was true when the aging of the objective lens occurred.

  Accordingly, the present invention solves the above-described problems, and an optical disc apparatus capable of continuously reproducing good information even when the objective lens is contaminated or the objective lens is secularly changed. The purpose is to provide.

According to a first aspect of the present invention, there is provided an optical disc apparatus for reproducing information on the optical disc by irradiating an information surface of the optical disc with laser light emitted from a semiconductor laser element through an objective lens.
A laser driver circuit for supplying a current corresponding to a target value to the semiconductor laser element;
A photodetector that detects return light from the optical disc and photoelectrically converts it to generate an RF signal;
A signal level detection circuit for detecting a signal level of an RF signal photoelectrically converted by the photodetector;
Initial value data having an initial value of a variation width of the signal level of the RF signal in consideration of lot-to-lot variation for each type of the optical disc at the time of shipment is stored, and the initial value data and the level detection circuit detect the initial value data. A level comparator that compares the signal level of the RF signal and outputs an instruction signal that increases the target value of the current supplied to the semiconductor laser element only when the signal level of the RF signal is smaller than the initial value data When,
An APC circuit that outputs a correction signal to the laser driver circuit for increasing a target value of a correction current to be supplied to the semiconductor laser element based on the instruction signal;
Based on the correction signal, a limit value is set to a total current value obtained by adding a correction current supplied from the laser driver circuit to the semiconductor laser element to a current corresponding to a target value supplied to the semiconductor laser element immediately before. And an optical disc apparatus characterized by comprising:
2. The optical disc apparatus according to claim 1, further comprising a display control circuit for causing the display unit to display an abnormality when the instruction signal is output from the level comparator. provide.

According to the configuration of the present invention, the initial value data having the initial value of the signal level variation of the RF signal in consideration of the lot-to-lot variation for each type of optical disc at the time of shipment is stored. A comparison is made with the signal level of the detected RF signal, and only when the signal level of the RF signal is smaller than the initial value data, an instruction signal for increasing the target value of the current supplied to the semiconductor laser element is output. Based on the signal, a correction signal is output from the APC circuit to the laser driver circuit, and a limit value is provided for the total current value supplied to the semiconductor laser element. Even in this case, good information can be reproduced continuously.
Further, it is possible to prevent the semiconductor laser element from being deteriorated by heat.

Hereinafter, an optical disk device according to each embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing an optical disk apparatus according to the first embodiment of the present invention, and FIG. 2 is a flowchart for operating the optical disk apparatus of FIG.

  As shown in FIG. 1, the optical disc apparatus 1 according to the first embodiment of the present invention detects an optical pickup 2 that detects return light from the optical disc D and generates an RF signal, and is output from the optical pickup 2. The signal level detection circuit 3 detects the signal level of the RF signal and the RF amplifier circuit 4 shapes the waveform of the signal level of the RF signal detected by the signal level detection circuit 3.

  Further, the optical disc apparatus 1 stores the initial value data at the time of shipment of the signal level of the RF signal corresponding to the type of the optical disc D in the memory 15A of the digital signal processing block 15, and the initial value data and the signal level detection circuit 3 A comparison is made with the signal level of the detected RF signal, and when the signal level is smaller than the initial value data, it is determined that the objective lens 11 is dirty or that the objective lens 11 has changed over time, and the semiconductor laser element in the optical pickup 2 9 is supplied to the semiconductor laser device 9 only when the level comparator 5 that outputs an instruction signal for raising the target value of an APC (Automatic Power Control) that supplies a correction current to the circuit 9 and the level comparator 5 outputs the instruction signal. An APC circuit 6 for outputting a correction signal for raising the target value of the correction current to be increased by one step, and the semiconductor laser element 9 based on the correction signal And a target current value which is provided in the laser driver circuit 7 and is supplied to the semiconductor laser element 9 immediately before the correction current having a target value higher by one step corresponding to the correction signal. It is determined whether or not the total current value when added to (current corresponding to the target value) exceeds three times the target current value supplied to the semiconductor laser element 9 in order to obtain the above-described initial value data. And a determination circuit 8.

Furthermore, the optical disc apparatus 1 is shaped by a servo signal processing block 14 for generating servo signals such as a focus error signal and a tracking error signal based on the RF signal output from the optical pickup 2 and the RF amplifier circuit 4. The signal level and servo signal processing block 14 comprises a digital signal processing block 15 for digital signal processing of the servo signal.
The optical pickup 2 has a polarization separation surface 10A that transmits part of the laser light emitted from the semiconductor laser element 9 and reflects the other to one side and reflects the return light from the optical disk D to the other side. And a polarizing beam splitter 10.

  The optical pickup 2 is emitted from an objective lens 11 that condenses the laser light that has passed through the polarizing beam splitter 10 onto the information surface of the optical disc D, and the semiconductor laser element 9 that is reflected by the polarization separation film 10A of the polarizing beam splitter 10. A front monitor diode 12 that detects and photoelectrically converts laser light, and a photodetector that detects the return light from the optical disc D reflected by the polarization separation film 10A of the polarization beam splitter 10 and photoelectrically converts it to generate the RF signal described above. 13.

Here, the initial value data at the time of shipment refers to a value having a width of ± 20% with reference to the value of the RF signal of the reference optical disk determined at the time of shipment.
In other words, the initial value data at the time of shipment is a value having a variation of ± 20% with respect to the value of the RF signal of the reference optical disk determined at the time of shipment as the initial value data. The initial value data may be arbitrarily determined depending on the type of optical disk such as DVD-ROM or DVD-RW.
For example, the initial value data can be determined to be ± 20% for a DVD-ROM and ± 25% for a DVD-RW.

Next, the operation will be described.
As shown in FIG. 2, a laser beam having a power based on the current output from the laser driver circuit 7 is emitted from the semiconductor laser element 9 (step S1). Next, the laser beam is transmitted through the polarization separation surface 10A of the polarization beam splitter 10 and condensed on the information surface of the optical disc D by the objective lens 11 (step S2).

Next, the return light from the information surface of the optical disk D is reflected by the polarization separation surface 10A of the polarization beam splitter 10 via the objective lens 11 and detected by the photodetector 13 (step S3).
Next, the signal level of the RF signal generated by photoelectric conversion by the photodetector 13 is detected by the signal level detection circuit 3 (step S4).
Here, the initial value data at the time of shipment determines the reference optical disc for each type of the optical disc D, and performs the steps (step S1) to (step S4) for the reference optical disc to detect the signal level of the RF signal. The value obtained in this way is used as a reference value, and is determined to be ± 20% with respect to this reference value. This initial value data is stored in the memory 15 A of the digital processing signal block 15.

Next, the signal level of the RF signal output from the signal level detection circuit 3 is not adhered to the objective lens 11 corresponding to each type of the optical disc D by the level comparator 5, is not contaminated, or is not changed over time. It is determined whether or not it is larger than the initial value data at step S5 (step S5).
When the signal level of the RF signal is greater than or equal to the initial value data, it is determined that the objective lens 11 is not contaminated, is not contaminated, or is not subject to secular change, and the reproduction is continued (step). S6).

When the signal level of the RF signal is smaller than the initial value data, it is determined that the objective lens 11 is contaminated, contaminated, or the objective lens 11 is aged, and the level comparator 5 sends an instruction signal to the APC circuit 6. And a correction signal for increasing the target value of the correction current supplied from the APC circuit 6 to the semiconductor laser element 9 by one step is output to the laser driver circuit 10 (step S7).
Next, in response to this correction signal, the total current value obtained by adding the correction current supplied from the laser driver circuit 7 to the semiconductor laser element 9 to the target current value supplied to the semiconductor laser element 9 immediately before is the initial value data. In order to obtain the above, it is determined whether or not the target current value to be supplied to the semiconductor laser element 9 exceeds three times (step S8).

If the total current value exceeds three times the target current value supplied to the semiconductor laser element 9 to obtain initial value data, the reproduction is not performed (step S9).
When the total current value is less than three times the target current value supplied to the semiconductor laser element 9 to obtain the initial value data, the process returns to (Step S5) and the signal level of the RF signal is higher than the initial value data. It is determined whether it is larger or equal, and the same operation as described above is performed.

As described above, according to the first embodiment of the present invention, the signal level of the RF signal is free from contamination of the objective lens 11 corresponding to the type of the optical disc D, no contamination, or no change in the objective lens 11 over time. Only when the initial value data is smaller than the initial value data, the laser driver circuit 7 outputs a correction signal for raising the target value of the correction current supplied from the APC circuit 6 to the semiconductor laser element 9 by one step, and based on this correction signal, A determination circuit for providing a limit value to the total current value obtained by adding the correction current supplied from the laser driver circuit 7 to the semiconductor laser element 9 to the target current value supplied to the semiconductor laser element 9 immediately before. Therefore, it is possible to continue to reproduce good information.
Even if it is determined in (Step S5) that the signal level of the RF signal is lower than the initial value data, in (Step S8), three times the current value supplied to the semiconductor laser element 9 to obtain the initial value data. In the case of exceeding the limit, the total current value supplied to the semiconductor laser element 9 is limited, so that excessive current can be supplied to the semiconductor laser element 9 to prevent deterioration of the semiconductor laser element 9 due to heat. .

  Furthermore, according to the first embodiment of the present invention, whether or not the signal level of the RF signal is higher than the initial value data and the target that the total current value supplies to the semiconductor laser device 9 to obtain the initial value data. Since it is possible to reproduce the optical disk D by determining whether or not the current value exceeds three times, in the case where there is no contamination of the objective lens 11, no contamination, or no change over time of the objective lens 11 The present invention is not limited to this and can be widely applied.

Next, a second embodiment of the present invention will be described.
As shown in FIG. 3, the optical disk apparatus according to the second embodiment of the present invention is abnormal based on the instruction signal described above in the digital signal processing block 15 of the optical disk apparatus 1 according to the first embodiment. A display control circuit 16 is provided for causing the display unit 17 to display a message to inform the user that the object lens 11 needs to be cleaned, and the like.
According to the second embodiment, since an error is displayed on the display unit 17, it is possible to prevent an error from occurring in advance when information is reproduced.
If it is determined in step S8 described in each embodiment that the total current value is equal to three times the target current value supplied to the semiconductor laser element 9 to obtain initial value data, the reproduction is performed as it is. To continue.
In step S8, the total current value is compared with the target current value supplied to the semiconductor laser element 9 to obtain initial value data, but the total current value is not limited to three times. As long as it is below the maximum rated current, any setting can be made. Note that the determination circuit 8 may be provided outside the laser driver circuit 7.

1 is a schematic diagram showing an optical disc apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a flowchart for explaining the operation of the optical disk device in FIG. 1. It is the schematic which shows the optical disk apparatus based on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical disk apparatus, 2 ... Optical pick-up, 3 ... Signal level detection circuit, 4 ... RF amplifier circuit, 5 ... Level comparator, 6 ... APC circuit, 7 ... Laser driver circuit, 8 ... Judgment circuit, 9 ... Semiconductor laser element DESCRIPTION OF SYMBOLS 10 ... Polarizing beam splitter, 11 ... Objective lens, 12 ... Front monitor diode, 13 ... Photo detector, 14 ... Servo signal processing block, 15 ... Digital signal processing block, 15A ... Memory, 16 ... Display control circuit, 17 ... Display part .

Claims (2)

In an optical disc apparatus for reproducing information on the optical disc by irradiating an information surface of the optical disc with laser light emitted from a semiconductor laser element through an objective lens,
A laser driver circuit for supplying a current corresponding to a target value to the semiconductor laser element;
A photodetector that detects return light from the optical disc and photoelectrically converts it to generate an RF signal;
A signal level detection circuit for detecting a signal level of an RF signal photoelectrically converted by the photodetector;
Initial value data having an initial value of a variation width of the signal level of the RF signal in consideration of lot-to-lot variation for each type of optical disc at the time of shipment is stored, and the initial value data and the level detection circuit detect the initial value data. A level comparator that compares the signal level of the RF signal and outputs an instruction signal that increases the target value of the current supplied to the semiconductor laser element only when the signal level of the RF signal is smaller than the initial value data When,
An APC circuit that outputs a correction signal to the laser driver circuit for increasing a target value of a correction current to be supplied to the semiconductor laser element based on the instruction signal;
Based on the correction signal, a limit value is set to a total current value obtained by adding a correction current supplied from the laser driver circuit to the semiconductor laser element to a current corresponding to a target value supplied to the semiconductor laser element immediately before. An optical disc apparatus comprising: a determination circuit provided with an optical disc device.   2. The optical disc apparatus according to claim 1, further comprising a display control circuit that causes the display unit to display an abnormality when the instruction signal is output from the level comparator.

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