JP2006099861A - Reproduction control method for optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reproduction control method for an optical disk device, capable of reproducing a signal recorded in an optical disk by a laser beam applied from an optical pickup. <P>SOLUTION: A signal is reproduced from an optical disk 1 having signals recorded therein by a plurality of pits different in length by a laser beam emitted from a laser diode incorporated in an optical pickup 2. By comparing the levels of RF signals obtained by reproducing the pits different in length and recorded in the optical disk 1, the spot shape of the laser beam with respect to a signal track is detected, and the equalizer characteristics of the RF signal are set based on the detected spot shape. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a playback control method for an optical disc apparatus that performs a playback operation of a signal recorded on an optical disc using laser light emitted from a laser diode incorporated in an optical pickup.

  2. Description of the Related Art Optical disc apparatuses that perform a reproduction operation of a signal recorded on an optical disc by laser light emitted from a laser diode have become widespread. As an optical disk device, an apparatus using an optical disk called a CD or an apparatus using an optical disk called a DVD is generally used.

  Signals are recorded in pits having different lengths on the optical disc, and the length of such pits is specified as 3T, 4T... 11T for CD discs, and 3T, 4T. ing.

  The reproduction operation of the signal recorded on the optical disc is performed by the laser light emitted from the optical pickup. The signal reproduced by correcting the frequency of the RF signal obtained from the photodetector by a circuit called an equalizer. Digitization, that is, binarization is performed (see, for example, Patent Document 1).

  Such a frequency correction operation of the RF signal is set so that the spot shape of the laser light emitted from the optical pickup is a perfect circle or the tangential direction of the track, that is, the diameter in the tangential direction is constant. However, the direction of the laser beam spot is not constant and differs for each optical pickup.

In order to improve such a point, a technique for adjusting the spot direction of a laser beam with respect to a track on an optical disc has been developed (see, for example, Patent Document 2).
JP-A-6-36291 JP-A-8-63777

  The technique described in Patent Document 2 needs to be adjusted accurately at the time of manufacturing the optical pickup, and thus has a problem that the manufacturing cost increases. In addition, even when the optical pickup adjusted in this way is used, when it is incorporated into an optical disc apparatus, the relationship between the spot shape with respect to the track is constant due to the displacement of the mounting position and the change of the spot shape accompanying the focus control operation. It is difficult to make.

  As described above, since the relationship between the track on the optical disk and the spot shape of the laser beam is not constant, there is a problem in that an RF signal cannot be accurately extracted with the preset equalizer characteristics.

  The present invention seeks to provide a reproduction control method capable of solving such a problem.

  The present invention relates to an optical disc apparatus configured to reproduce a signal from an optical disc in which signals are recorded by a plurality of pits having different lengths by laser light emitted from a laser diode incorporated in an optical pickup. The spot shape with respect to the signal track of the laser beam is detected by comparing the level of the RF signal obtained by reproducing the pits having different lengths recorded on the optical disc, and the RF signal is detected based on the detected spot shape. It is configured to set the equalizer characteristics.

  In the present invention, the level comparison operation is performed by an RF signal obtained by reproducing the shortest pit and the longest pit recorded on the optical disc.

  The present invention further includes an equalizer characteristic data memory circuit in which a plurality of equalizer characteristic setting data corresponding to comparison values obtained by comparing the levels of the RF signals are stored, and the equalizer stored in the equalizer characteristic data memory circuit The equalizer characteristic is set by selecting the characteristic setting data based on the comparison value.

  Further, the present invention is configured to extract the RF signal for performing the level comparison operation from the input side of the equalizer circuit.

  The present invention detects a spot shape with respect to a signal track of a laser beam by comparing levels of RF signals obtained by reproducing pits having different lengths recorded on an optical disk, and based on the detected spot shape. Since the equalizer characteristic of the RF signal is set, the reproduction operation of the signal recorded on the optical disc can be performed accurately.

  Further, in the present invention, the level comparison operation is performed with the RF signal obtained by reproducing the shortest pit and the longest pit recorded on the optical disk, that is, obtained from the pit having the largest level difference to be compared. Since the level of the RF signal to be compared is compared, the spot shape detection operation can be performed accurately.

  The present invention further includes an equalizer characteristic data memory circuit in which a plurality of equalizer characteristic setting data corresponding to comparison values obtained by comparing the levels of the RF signals are stored, and the equalizer stored in the equalizer characteristic data memory circuit Since the equalizer characteristic is set by selecting the characteristic setting data based on the comparison value, the reproduction operation of the signal recorded on the optical disc can be performed accurately.

  Further, in the present invention, the RF signal for performing the level comparison operation is extracted from the input side of the equalizer circuit, that is, the RF signal that is not affected by the equalizer circuit is used. The level detection operation can be performed under the same conditions, and therefore the spot shape detection operation can be performed accurately.

  In the present invention, the spot shape of a laser beam is detected by comparing the levels of RF signals obtained by reproducing signals recorded in pits having different lengths on an optical disk.

  FIG. 1 is a block circuit diagram showing an embodiment of an optical disk apparatus according to the present invention, and FIG. 2 is an explanatory diagram showing the relationship between a signal track of an optical disk and a laser beam spot according to the present invention.

  In FIG. 1, reference numeral 1 denotes an optical disk that is rotationally driven by a spindle motor (not shown), and is configured to be rotationally controlled so as to have a constant linear velocity, for example. Reference numeral 2 denotes an optical pickup in which a laser diode 3 for irradiating laser light is incorporated, and the laser light emitted from the laser diode 3 is reflected from the objective lens 4 for focusing the recording layer of the optical disc 1 and the optical disc 1. A laser beam is received and converted into an electrical signal, and a photodetector 5 composed of a quadrant sensor or the like, a tracking coil 6 for displacing the objective lens 4 in the radial direction of the optical disc 1, and the objective lens 4 as a signal surface of the optical disc 1 A focusing coil 7 that is displaced in the vertical direction is incorporated.

  In such a configuration, the main body of the optical pickup 2 is configured to be displaced in the radial direction of the optical disc 1 by a pickup feeding motor (not shown). Since such a driving mechanism may use a known mechanism, the description thereof is omitted.

  Reference numeral 8 denotes an optical output signal processing circuit to which an electrical signal obtained from the photodetector 5 is input as an optical signal. An RF signal that is a read signal of the focus error signal and the signal recorded on the optical disc 1 is generated and output. Since various signal generation operations by the optical output signal processing circuit 8 are performed by known circuits, description thereof is omitted.

  Reference numeral 9 denotes a tracking servo circuit to which a tracking error signal generated and output by the optical output signal processing circuit 8 is input, and supplies a tracking coil drive signal based on the input tracking error signal to the tracking coil 6. Is configured to perform a tracking control operation. Reference numeral 10 denotes a focus servo circuit to which a focus error signal generated and output by the optical output signal processing circuit 8 is input, and supplies a focusing coil drive signal based on the input focus error signal to the focusing coil 7. Is configured to perform a focus control operation.

  The focusing coil drive signal supplied from the focus servo circuit 10 to the focusing coil 7 is accompanied by a DC voltage that displaces the objective lens 4 to an operating position that is a position for focusing the recording layer of the optical disc 1 and surface vibration of the optical disc 1. In order to correct the focus shift, it is composed of a high-frequency signal that displaces the objective lens 4 at a high speed, but such a signal is well known and will not be described.

  Reference numeral 11 denotes an RF signal amplifier circuit that receives the RF signal output from the optical output signal processing circuit 8 and amplifies the signal. Reference numeral 12 denotes an equalizer circuit that receives the RF signal output from the RF signal amplifier circuit 11. Thus, the frequency of the input RF signal is corrected so that the desired reproduction signal extraction operation can be performed accurately.

  Reference numeral 13 denotes a binarization circuit that binarizes the input signal while the RF signal output from the equalizer circuit 12 is input. Reference numeral 14 denotes a reproduction signal that is binarized by the binarization circuit 13. And a digital signal processing circuit that performs digital signal processing, and is configured to demodulate various signals such as synchronization signals, position information data, and data signals recorded on the optical disc 1.

Reference numeral 15 denotes a system control circuit for controlling each operation of the optical disk apparatus, and uses the synchronization signal generated by the digital signal processing circuit 14 to control the rotation of the optical disk 1 by the spindle motor and the processing operation of the reproduction signal. Are configured to control signal transmission / reception operations with a host device such as a personal computer. Such a system control circuit 15 is configured by a microcomputer and is configured to perform various control operations based on program software stored in a flash ROM or the like provided therein.

  Reference numeral 16 denotes an RF signal level detection circuit that receives the RF signal output from the RF signal amplification circuit 11 and detects the level of the signal. The shortest pit recorded on the optical disc 1, for example, a 3T signal and the longest signal It is configured to detect the level of an RF signal obtained from a pit, for example, a 14T signal. Such a level detection operation by the RF signal level detection circuit 16 is a level detection operation control output from the system control circuit 15 when a 3T signal and a 14T signal are recognized from the signal obtained by the digital signal processing circuit 14. This is done based on the signal.

  Reference numeral 17 denotes a first level memory circuit whose operation is controlled by the system control circuit 15, and is configured to store the level L1 of the RF signal corresponding to 3T detected by the RF signal level detection circuit 16. Yes. Reference numeral 18 denotes a second level memory circuit whose operation is controlled by the system control circuit 15, and is configured to store the level L2 of the RF signal corresponding to 14T detected by the RF signal level detection circuit 16. Yes.

  The system control circuit 15 is configured to calculate the ratio R from L2 / L1 when the RF signal levels L1 and L2 are stored in the first level memory circuit 17 and the second level memory circuit 18. Yes.

  Reference numeral 19 denotes a laser drive circuit whose operation is controlled by the system control circuit 15, and is configured to supply a drive current that is irradiated from the laser diode 3 with a laser beam having an output suitable for performing a reproduction operation during the reproduction operation. Has been.

  Reference numeral 20 denotes an equalizer characteristic setting circuit whose operation is controlled by the system control circuit 15 and has an action of changing and setting the frequency characteristic of the equalizer circuit 12 that performs the frequency correction operation of the RF signal. An equalizer characteristic data memory circuit 21 is incorporated in the system control circuit 15 and is calculated based on levels L1 and L2 corresponding to 3T and 14T pits detected by the RF signal level detection circuit 16. Equalizer characteristic data for performing a frequency correction operation according to the value of the ratio R is stored as table data.

  The frequency characteristic setting operation for the equalizer circuit 12 by the equalizer characteristic setting circuit 20 is performed based on table data obtained from the equalizer characteristic data memory circuit 21.

  As described above, the optical disk apparatus according to the present invention is configured. Next, the operation will be described. When the reproduction operation of the signal recorded on the optical disk 1 is performed, the rotation control operation of the spindle motor is performed, and the optical disk 1 is rotationally driven at a predetermined linear velocity. Such a control operation for keeping the linear velocity constant includes a synchronization signal read from the optical disc 1 and a synchronization signal generated from a synchronization signal generation circuit (not shown) connected to be controlled by the system control circuit 15. Are synchronized with each other, but since such operations are well known, the description thereof will be omitted.

The drive signal supplied to the laser diode 3 for reproducing the signal recorded on the optical disc 1 is set so as to obtain a laser output necessary for performing the reproducing operation. The laser light emitted from the laser diode 3 is collected by the objective lens 4 and focused on the signal surface of the optical disc 1. Such focusing operation is performed by a servo operation by the focus servo circuit 10. Is called.

  The focus control operation by the focus servo circuit 10 is performed using a signal obtained from the photodetector 5 irradiated with laser light reflected from the signal surface of the optical disc 1. A signal obtained from the photodetector 5 is input to the optical output signal processing circuit 8, a focus error signal is generated based on the signal, and the focus error signal is input to the focus servo circuit 10. When such a focus error signal is input to the focus servo circuit 10, a drive signal for displacing the objective lens 4 in the direction of decreasing the level of the focus error signal is supplied from the focus servo circuit 10 to the focusing coil 7. . As a result of supplying such a drive signal to the focusing coil 7, an operation of focusing the laser beam on the signal surface of the optical disc 1, that is, a focus control operation can be performed.

  Although the focus control operation is performed as described above, the tracking control operation can be performed in the same manner. That is, when the spot of the laser light emitted from the laser diode 3 deviates from the signal track on the optical disc 1, a tracking error signal having a level corresponding to the magnitude of the deviation is output from the optical output signal processing circuit 8. When such a tracking error signal is input to the tracking servo circuit 9, a driving signal for displacing the objective lens 4 in the direction of decreasing the level of the tracking error signal is supplied from the tracking servo circuit 9 to the tracking coil 6. . As a result of supplying such a drive signal to the tracking coil 6, an operation of causing the laser light to follow a signal track provided on the signal surface of the optical disc 1, that is, a tracking control operation can be performed.

  As a result of the above-described focus control operation and tracking control operation being performed, the signal recorded on the signal track of the optical disc 1 can be read. A signal track of the optical disc 1 is recorded with a plurality of pits having different lengths, and an RF signal corresponding to the length of the pits is generated by the optical output signal processing circuit 8 to generate an RF signal amplification circuit. 11 is output.

  The RF signal input to the RF signal amplifier circuit 11 is input to the equalizer circuit 12 after being amplified. When an RF signal is input to the equalizer circuit 12, the RF signal is frequency corrected by the equalizer circuit 12 and then input to the binarization circuit 13. As a result, the RF signal is binarized by the binarization circuit 13.

  The signal binarized by the binarization circuit 13 is input to the digital signal processing circuit 14, and demodulation operation is performed by the digital signal processing circuit 14. The data signal demodulated by the digital signal processing circuit 14 is output to a personal computer or the like via the system control circuit 15.

  As described above, the reproduction operation in the present embodiment is performed. Next, the laser beam spot shape recognition operation according to the present invention will be described.

  FIG. 2 shows the relationship between the pits P formed on the signal track of the optical disc 1 and the laser light spot S. FIG. The shape of the spot S of the laser beam is generally an ellipse, and FIG. 2A shows the case where the shape of the spot S is an ellipse and the major axis direction coincides with the track direction. In FIG. 2C, when the spot S has an ellipse shape and the major axis direction is inclined by about 45 degrees with respect to the track direction, FIG. This is a case where the major axis direction is perpendicular.

The spot S of the laser beam acting to reproduce the pit P formed on the optical disc 1 is a portion overlapping the pit P in FIG. 2, and the length direction of the pit P is apparent from each state. That is, the effective length L which is the length in the tangential direction is different.

  The present invention improves the deterioration of the reproduction characteristics due to the difference in the effective length L caused by the difference in the shape of the spot S. That is, the frequency correction characteristic by the equalizer circuit 12 is changed according to the change in the effective length L.

  Next, an operation for detecting the shape of the spot S that causes the effective length L to be different will be described. When an operation for reproducing a signal recorded on the optical disk 1 by pit formation is performed, an RF signal is output from the optical output signal processing circuit 8 as described above.

  The RF signal output from the optical output signal processing circuit 8 is input to the RF signal amplifier circuit 11, amplified, input to the equalizer circuit 12, and input to the RF signal level detection circuit 16. In such a state, the RF signal level detection circuit 16 is in a state of performing an operation of detecting the level of the input RF signal. Further, the RF signal input to the equalizer circuit 12 is frequency-corrected and then input to the binarization circuit 13 to be binarized. In such a case, the frequency correction characteristic of the equalizer circuit 12 is The reference correction characteristic is set so as to be in the middle of the correction characteristic range by the equalizer characteristic setting circuit 20.

  In such a state, since the level detection operation by the RF signal level detection circuit 16 and the digital signal processing operation by the digital signal processing circuit 14 for the signal output from the binarization circuit 13 are performed, 3T by the digital signal processing circuit 14 is performed. Signal and 14T signal detection operations are performed.

  When the 3T signal is detected by the digital signal processing circuit 14, a control operation is performed by the system control circuit 15, and the level L1 of the RF signal detected by the RF signal level detection circuit 16 at that time is used as the first level memory circuit. The operation to be stored in 17 is performed. Similarly, when the 14T signal is detected, the control operation by the system control circuit 15 is performed, and the operation of storing the level L2 of the RF signal detected by the RF signal level detection circuit 16 in the second level memory circuit 18 at that time. Is done.

  When the storage operation of level L1 in the first level memory circuit 17 and the storage operation of level L2 in the second level memory circuit 18 are performed, the level ratio R of the RF signal is set to L2 by the arithmetic processing operation by the system control circuit 15. / L1.

  As for the level of the RF signal output from the optical output signal processing circuit 8, the level L1 obtained from the 3T signal having the shortest pit length is the smallest, and the level L2 obtained from 14T being the longest pit length is the largest. Further, the level of the RF signal changes corresponding to the effective length L of the spot S with respect to the pit P. That is, as the effective length L becomes shorter, a greater change in reflected light can be obtained, and the level of the RF signal increases.

  On the other hand, the ratio of the effective length L of the spot S to the length of the pit P changes according to the size of the effective length L. However, since the pit length is defined by the recording standard of the optical disc 1, 3T And the length of 14T becomes constant. As a result, the level of the RF signal obtained from the 3T and 14T pits varies depending on the effective length L of the spot S, and the rate of change is also different.

When the L1 value is LA1 and the L2 value is LA2 when the effective length L of the spot S is LA, the ratio RA is LA2 / LA1, and the effective length L of the spot S is LB. When the value of L1 is LB1 and the value of L2 is LB2, the ratio RB is LB2 / LB1. Then, the ratios RA and RB obtained in this way are different as the effective length L of the spot S is different.

  When the ratio of the RF signal level obtained from 3T and 14T is obtained with a constant pit length, the effective length L of the laser light spot S relative to the pit can be detected. Further, since the shape of the laser light spot S in the optical pickup 2 is determined at the time of manufacturing the optical pickup 2, the shape of the spot S with respect to the signal track of the laser light is detected by detecting the effective length L. I can do it.

  Since the shape of the spot S with respect to the signal track can be detected in this way, the effective length L can be recognized. Accordingly, the equalizer characteristic data for setting the frequency correction characteristic of the equalizer circuit 12 so as to obtain an optimum equalizer characteristic for binarizing the RF signal reproduced by each spot having the effective length L at the time of manufacturing the optical disc apparatus. It is possible to store the equalizer characteristic data memory circuit 21 as table data and select and use the data to set the equalizer correction characteristic of the equalizer circuit 12 to an optimum characteristic for reproducing a signal from the optical disc 1. I can do it.

  In the present embodiment, the level of the RF signal obtained by reproducing the shortest pit and the longest pit recorded on the optical disc 1 is detected, but other pits can of course be used. The frequency correction operation of the equalizer circuit 12 can be performed by a high-pass filter or a band-pass filter, and the filter characteristic change setting operation can also be performed digitally.

1 is a block circuit diagram showing an embodiment of an optical disc apparatus according to the present invention. It is explanatory drawing which shows the relationship between the pit formed in the signal track | truck of an optical disk, and the spot of a laser beam.

Explanation of symbols

1 Optical disc
2 Optical pickup
3 Laser diode
5 photodetectors
8 Optical output signal processing circuit 11 RF signal amplification circuit 12 Equalizer circuit 13 Binary circuit 14 Digital signal processing circuit 15 System control circuit 16 RF signal level detection circuit 17 First level memory circuit 18 Second level memory circuit 20 Equalizer characteristic setting Circuit 21 Equalizer characteristic data memory circuit

Claims (4)

A reproduction control method for an optical disc apparatus configured to reproduce a signal from an optical disc in which signals are recorded by a plurality of pits having different lengths by laser light emitted from a laser diode incorporated in an optical pickup. Yes, the spot shape with respect to the signal track of the laser beam is detected by comparing the level of the RF signal obtained by reproducing the pits having different lengths recorded on the optical disc, and the RF signal is detected based on the detected spot shape. A reproduction control method for an optical disc apparatus, characterized in that the equalizer characteristic is set. 2. The reproduction control method according to claim 1, wherein the level comparison operation is performed by an RF signal obtained by reproducing the shortest pit and the longest pit recorded on the optical disc. An equalizer characteristic data memory circuit storing a plurality of equalizer characteristic setting data corresponding to the comparison value obtained by comparing the RF signal levels is provided, and the equalizer characteristic setting data stored in the equalizer characteristic data memory circuit is compared with the comparison value. The reproduction control method according to claim 1, wherein the equalizer characteristic is set by making a selection based on the selection. 2. The reproduction control method according to claim 1, wherein an RF signal for performing the level comparison operation is extracted from an input side of the equalizer circuit.

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