JP2009076120A - Signal reproduction device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal reproducing unit enabling stable reproduction by detecting defects in an optical disk more accurately than before. <P>SOLUTION: A plurality of thresholds (upper-side envelope thresholds 1, 2 and lower-side envelope thresholds 1, 2) for comparing an upper-side envelope 35 with the lower one 36 are used, to obtain a defect state more accurately, and improve reproduction stability by optimally controlling each circuit block. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides a method for detecting defects in an optical disc in a signal reproducing apparatus by detecting a defective area using a plurality of detection threshold values for each of an upper envelope and a lower envelope and controlling each circuit from the detection result. Therefore, more stable reproduction is possible.

  In recent years, optical disk devices have penetrated not only the information-related field but also the field of consumer equipment, and in order to achieve a large capacity, the laser wavelength has been shortened and the recording medium has been made more dense. . However, as the density increases, defects such as dirt and scratches on the optical disk greatly affect the data reproduction capability, and even when there are defects, more stable reproduction is required. Further, there are various defects such as black spots (defects in the dark level direction) and missing mirrors (defects in the bright level direction), and stable reproduction may not be possible unless the defect area detection is enhanced.

  In this way, as a conventional technique for detecting a defect area, the upper envelope and lower envelope of the RF signal are used, each envelope is compared with a predetermined threshold value, the defect area is detected, and a defect detection flag is set. , Each circuit block was controlled.

  A conventional detection method will be described with reference to FIGS. An output signal from the optical pickup 2 that irradiates the optical disc 1 with a laser and receives reflected light is input to the RF signal processing circuit 4 to generate an RF signal necessary for reproduction. The output of the RF signal processing circuit 4 is input to the AGC circuit 5 and controlled so that the amplitude becomes constant with respect to the amplitude variation of the input, and the AGC-RF signal 11 is output. The AGC-RF signal 11 is input to the slice circuit 6 and binarized. The binarized output is input to the PLL circuit 7 and a clock 12 proportional to the rotation speed is output. Further, an output signal from the AGC circuit 5 is input to the envelope detection circuit 8, and an upper envelope 15 and a lower envelope 16 are extracted. The extracted upper envelope 15 and lower envelope 16 are input to the defect detection circuit 9 to generate a flag (BDO detection flg) for detecting the dark defect portion by comparing the upper envelope with the upper envelope threshold. Then, a flag (Mirror detection flg) for detecting a bright defect portion is generated by comparing the lower envelope with the lower envelope threshold. When the extracted upper envelope falls below the upper envelope threshold as shown in FIG. 6 (a), it is detected that a defect in the dark level direction exists, and BDO detection flg is output, as shown in FIG. 6 (b). When the lower envelope exceeds the lower envelope threshold, it is detected that there is a defect in the light level direction, and a Mirror detection flg is output.

However, depending on the defect, such as when there is irregular reflection due to scratches as shown in FIG. 6C, the amount of reflected light returns to the optical pickup, so the level of the amount of scratches may be intermediate between the bright side and the dark side. In this case, if there is one threshold value for each of the upper envelope and the lower envelope, (BDO detection flg, Mirro detection flg) in FIG. 6 (d) = (0, 0) and the defective portion cannot be detected. It is not recognized as a defective part and is recognized as a normal waveform. For this reason, each part cannot operate optimally, and reproduction may become unstable. Further, if the upper envelope threshold value and the lower envelope threshold value are not set appropriately, even a small defect may be detected and the reproduction stability may be impaired.
Japanese Patent Laid-Open No. 10-40546 JP2003-178468

  In the prior art, depending on the defect, the amount of light in the defective part may take an intermediate position between the bright side and the dark side. In this case, if the threshold values of the upper envelope and the lower envelope are one each, it is regarded as a defect. As a result, there was a problem that optimal control could not be performed and reproduction was unstable.

  Therefore, an object of the present invention is to provide a signal reproducing apparatus that can reproduce more stably by detecting a defect of an optical disk more accurately than a conventional method.

  In order to solve the above-described problems, the signal reproducing apparatus of the present invention provides a plurality of threshold values for defect detection with respect to the upper envelope and the lower envelope, thereby more accurately determining the defect state. Can be detected, and the reproduction capability can be improved.

  Specifically, the signal reproducing apparatus according to claim 1 of the present invention includes an optical pickup means for reproducing a medium on which information is recorded, a pickup driving means for driving the optical pickup, and the optical pickup means. An RF signal processing means for extracting a signal necessary for reproduction from the signal obtained from the above, an AGC means for making the output amplitude of the RF signal processing means constant, and an output for binarizing the output of the AGC means Slicing means, PLL means for generating a clock according to the rotational speed from the slicing means, envelope detecting means for extracting the upper and lower envelopes of the signal obtained from the AGC means, and the envelope Defect detection means for detecting defects by comparing the upper envelope and the lower envelope with a plurality of threshold values for the output of the detection means, and from the detection result of the defect detection means It is obtained by allowing at least one control of the AGC means and the slicing means and said PLL means and the pickup driving means.

  The first threshold value of the upper envelope of the defect detection means is larger than the second threshold value, the first threshold value of the lower envelope of the defect detection means is larger than the second threshold value, and the upper threshold value of the defect detection means. It is desirable to increase the AGC response gain when the first envelope threshold or the second lower envelope threshold is exceeded.

  Furthermore, the first threshold value of the upper envelope of the defect detection means is greater than the second threshold value, the first threshold value of the lower envelope of the defect detection means is greater than the second threshold value, and the upper threshold value of the defect detection means. When the first threshold of the envelope or the second threshold of the lower envelope is exceeded, it is desirable to increase the gain of the response of the data slicing means.

  According to the present invention, it becomes possible to detect the defect of the optical disc more accurately than the conventional method, and to reproduce more stably.

By performing the defect detection by comparing the upper envelope with a plurality of thresholds, and by performing the defect detection by comparing the lower envelope with a plurality of thresholds, the purpose of improving the reproduction capability of the defective portion, Detailed defect detection is possible, and each circuit is realized by optimal control.
(Embodiment 1)
FIG. 1 is a block diagram of an optical disc apparatus showing a method according to Embodiment 1 of the present invention. The signal reproducing apparatus shown in FIG. 1 reproduces an RF signal or the like from an optical pickup means 22 for reading information from an optical disc 21, a pickup driving means 23 for driving the optical pickup means 22, and a signal output from the optical pickup means 22. An RF signal processing circuit 24 that generates a necessary signal, an AGC circuit 25 that outputs an AGC-RF signal 31 in which the signal amplitude of the RF signal is constant regardless of a change in the amount of light, and an output of the AGC circuit are binarized. A slice circuit 26; a PLL circuit 27 that generates a clock according to the rotational speed from the binarized data; and an envelope detector 28 that extracts an upper envelope and a lower envelope from the output signal of the AGC circuit 25; The upper envelope and the lower envelope are each provided with a defect detection circuit 29 that compares a plurality of predetermined thresholds to detect defects and controls each circuit in accordance with the defect information.

  The detection method in Embodiment 1 is demonstrated using FIG. 1 and FIG.

  First, the optical disk 21 is activated, and the optical pickup 22 is controlled by the pickup driving means 23 to reproduce the optical disk 1. The reproduction signal is generated as an RF signal by the RF signal processing circuit 24 and controlled to always have a predetermined amplitude by the AGC circuit 25 to generate an AGC-RF signal 31. The AGC-RF signal 31 is input to the slice circuit 26 and binarized. The binarized output is input to the PLL circuit 27, and the PLL circuit 27 generates a clock 32 corresponding to the rotation speed.

  The AGC-RF signal 31 is also input to the envelope detection circuit 28. The envelope detection circuit 28 detects the upper envelope 35 and the lower envelope 36 of the AGC-RF signal, and when there is a defect (Black dot = BDO) on the dark side, the upper envelope as shown in FIG. When the line 35 and the lower envelope 36 are output and there is a defect (Mirror) on the bright side, when the upper envelope 35 and the lower envelope 36 are output as shown in FIG. The upper envelope 35 and the lower envelope 36 as shown in FIG.

  The defect detection circuit 29 compares the upper envelope 35 with the upper envelope threshold 1 and outputs BDO detection flg1 = 1 when the upper envelope becomes equal to or lower than the upper envelope threshold 1. Similarly, the upper envelope 35 and the upper envelope threshold 2 are compared, and when the upper envelope becomes equal to or lower than the upper envelope threshold 2, BDO detection flg2 = 1 is output. Further, the lower envelope 36 and the lower envelope threshold 1 are compared, and when the lower envelope becomes equal to or higher than the upper envelope threshold 1, Mirror detection flg1 = 1 is output. Similarly, the lower envelope 36 and the lower envelope threshold 2 are compared, and when the lower envelope becomes equal to or higher than the lower envelope threshold 2, Mirror detection flg2 = 1 is output.

  Therefore, as shown in FIG. 2 (d), the defect detection circuit 29 has a dark side when (BDO detection flg1, BDO detection flg2, Mirror detection flg1, Mirror detection flg2) = (1,1,0,0). Judged as a defect (BDO). Similarly, if (BDO detection flg1, BDO detection flg2, Mirror detection flg1, Mirror detection flg2) = (0,0,1,1), it is determined that the defect is a bright side (Mirror). When (BDO detection flg1, BDO detection flg2, Mirror detection flg1, Mirror detection flg2) = (1,0,0,1), it is determined that the defect is a flaw (irregular reflection).

  Using this detection result, at least one of the circuits (pickup drive circuit 23, AGC circuit 25, slice circuit 26, and PLL circuit 27) necessary for reproducing the optical disk is controlled to stabilize the reproduction of the optical disk.

Also, by combining the detection results of BDO detection flg1, BDO detection flg2, Mirror detection flg1, and Mirror detection flg2, it becomes possible to recognize the state of the AGC-RF waveform and to control each circuit in detail. The reproduction performance at the defective part is improved.
(Embodiment 2)
This embodiment shows an example in which the gain of the response of the AGC circuit 25 is increased when the upper envelope threshold value 1 or the lower envelope threshold value 2 of the defect detection circuit 1 in FIG. 1 is exceeded.

As shown in FIG. 3, when the upper envelope 35 and the lower envelope 36 are output, (BDO detection flg1, BDO detection flg2, Mirror detection flg1, Mirror detection flg2) = (1,0,0,0) Alternatively, a detection result of (BDO detection flg1, BDO detection flg2, Mirror detection flg1, Mirror detection flg2) = (0,0,0,1) is obtained. At this time, by increasing the gain of the AGC circuit 25, it is possible to amplify the amplitude of the defective portion and obtain a signal amplitude substantially equivalent to the portion having no defect, and thus stable reproduction is possible.
(Embodiment 3)
This embodiment shows an example in which the gain of the response of the data slicing means 26 is increased when the upper envelope threshold value 1 or the lower envelope threshold value 2 of the defect detection circuit 1 in FIG. 1 is exceeded.

  As shown in FIG. 4, when the upper envelope 35 and the lower envelope 36 are output, (BDO detection flg1, BDO detection flg2, Mirror detection flg1, Mirror detection flg2) = (1,0,0,0) Alternatively, a detection result of (BDO detection flg1, BDO detection flg2, Mirror detection flg1, Mirror detection flg2) = (0,0,0,1) is obtained. At this time, by increasing the gain of the DSL circuit 26, the responsiveness to the binarization at the defective portion is improved, so that stable reproduction is possible.

  As described above, the optical disk apparatus according to the present invention can grasp the defect of the optical disk more accurately than the conventional system, and can improve the reproduction capability.

1 is a block diagram of an optical disc apparatus showing a method according to Embodiment 1 of the present invention. (A) Waveform diagram in the dark side defect portion when the method for implementing the optical disc device according to the present invention is applied (b) Waveform diagram in the bright side defect portion when the method for implementing the optical disc device according to the present invention is applied (c) FIG. 4 is a waveform diagram of a flaw (diffuse reflection) defect portion when the method for implementing an optical disk device according to the present invention is applied. (D) A diagram showing a defect output flag state when the method for implementing an optical disk device according to the present invention is shown Waveform diagram when the optical disc apparatus according to the present invention is applied to the second embodiment Waveform diagram when the optical disc apparatus according to the present invention is applied to the third embodiment A block diagram showing a method of implementing a conventional optical disc apparatus (A) Waveform diagram in the dark side defect portion when the conventional optical disc device implementation method is applied (b) Waveform diagram in the bright side defect portion when the conventional optical disc device implementation method is applied (c) Conventional optical disc Waveform diagram at a flaw (diffuse reflection) defect portion when the apparatus implementation method is applied (d) A figure showing a defect output flag state when an implementation method of a conventional optical disc apparatus is shown

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Optical pick-up 3 Pickup drive circuit 4 RF signal processing circuit 5 AGC circuit 6 Slice circuit 7 PLL circuit 8 Envelope detection circuit 9 Defect detection circuit 10 Control signal 11 AGC-RF signal 12 Clock 15 Upper envelope 16 Lower envelope Line 21 Optical disk 22 Optical pickup 23 Pickup drive circuit 24 RF signal processing circuit 25 AGC circuit 26 Slice circuit 27 PLL circuit 28 Envelope detection circuit 29 Defect detection circuit 30 Control signal 31 AGC-RF signal 32 Clock 35 Upper envelope 36 Lower side envelope

Claims (3)

Optical pickup means for reproducing a medium on which information is recorded;
Pickup driving means for driving the optical pickup;
RF signal processing means for extracting a signal necessary for reproduction from the signal obtained from the optical pickup means;
AGC means for making the output amplitude of the RF signal processing means constant;
Slicing means for binarizing the output of the AGC means;
PLL means for generating a clock according to the rotation speed from the slicing means,
An envelope detection means for extracting an upper envelope and a lower envelope of the signal obtained from the AGC means;
For the output of the envelope detecting means, the upper envelope and the lower envelope are respectively compared with a plurality of threshold values, and defect detecting means for detecting defects,
A signal reproducing apparatus capable of controlling at least one of the AGC means, the slicing means, the PLL means, and the pickup driving means from the detection result of the defect detecting means. The first threshold of the upper envelope of the defect detection means is greater than a second threshold, the first threshold of the lower envelope of the defect detection means is greater than a second threshold, and the upper envelope of the defect detection means 2. The signal reproducing apparatus according to claim 1, wherein when the first threshold value of the line or the second threshold value of the lower envelope is exceeded, the gain of the AGC response is increased. The first threshold of the upper envelope of the defect detection means is greater than a second threshold, the first threshold of the lower envelope of the defect detection means is greater than a second threshold, and the upper envelope of the defect detection means 2. The signal reproducing apparatus according to claim 1, wherein when the first threshold value of the line or the second threshold value of the lower envelope is exceeded, the gain of the response of the data slicing means is increased.

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