JPH0991858A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical disk device with which the retrieval of information of different kinds of optical disks is possible as well. SOLUTION: This optical disk device has a focus servo system for maintaining an objective lens in a focusing state at all times. A DC offset voltage is impressed on a coil for driving the objective lens from a driving circuit 36 when the objective lens is maintained in the focusing state in this focus servo system. The optical disks of the different kinds varying in recording density have transparent substrates respectively varying in thickness, therefore, the offset voltage for maintaining the objective lens in the focusing state varies. Then, the position of the objective lens and the kinds of the optical disks are specified by detecting the DC offset voltage with a DC offset detecting circuit 78.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, and more particularly to an optical disk device capable of retrieving information even for optical disks of different types.

[0002]

2. Description of the Related Art In recent years, in addition to an optical disc having a standard data recording density such as a CD (compact disc), the standard is different from the CD, the disc substrate thickness is different, and the data recording density High optical discs have been developed. Generally, in an optical disc, a recording layer is formed on a disc base made of disc-shaped transparent plastic, glass, or the like, and information is recorded on the recording layer. Usually, in this recording layer, pits conforming to the standard are formed in a reproduction-only CD or the like.

On the other hand, the optical disc apparatus is provided with an optical pickup for retrieving an information signal recorded in the recording layer of the optical disc, and an access mechanism for moving the optical pickup to a target address position on the optical disc and the optical disc. A rotation mechanism that holds and rotates the optical pickup, an access mechanism, a control circuit that controls the rotation mechanism, and a signal processing circuit that processes a reproduction signal are provided. In addition, this optical pickup is a light source such as a semiconductor laser that emits a light beam toward an optical disc,
An objective lens that focuses the light beam on the recording layer of the optical disc,
The optical detector includes a photodetector that detects the intensity of the reflected light beam from the optical disc, and an optical system that guides the light beam emitted from the semiconductor laser onto the optical disc and guides the reflected light beam from the optical disc to the photodetector. Further, the optical disc device includes a support mechanism that movably supports the optical pickup for adjusting focus and tracking, and a drive mechanism such as a magnetic circuit that drives the support mechanism.

Usually, a light beam generated from a light source such as a semiconductor laser is focused on a recording layer of an optical disc by an objective lens to record information on the optical disc or retrieve the information recorded on the optical disc. That is, a light beam is focused on the optical disc from the optical pickup facing the signal recording layer of the optical disc that is being driven to rotate, and the light beam is modulated according to the information recorded on the recording layer of the optical disc, and the information is recorded. To be searched.

In such an optical disk device, it is natural that the circuit structure according to the standard of the optical disk to be searched is adopted, and only the optical disk of a single standard can be searched. However, with the advent of high-density recording standards, conventional CDs can be used even in high-density compatible optical desk devices.
It is desired to be able to search for optical discs of standards such as, and optical disc devices compatible with both standards have been developed.

[0006]

In the optical disk device capable of searching optical disks of different standards as described above,
It is provided with a drive circuit for searching optical disks of different types and reproducing information, in particular, a reproduction signal processing circuit. In such an optical disk device, it is necessary to switch the circuit of the optical disk drive circuit according to the characteristics of the optical disk of different standards, and the circuit is switched using an external switch according to the type of the disk to be searched in advance. However, if the wrong type of optical disc to be searched is designated in advance, there is a problem that the optical disc cannot be searched.

Further, when searching different types of optical disks, there is a problem that a waveform shaping circuit is required for each optical disk because the search time of the shortest mark is different for each optical disk. The present invention is to provide an optical disk device capable of retrieving information even with different kinds of optical disks.

[0008]

According to the present invention, means for condensing a light beam toward an optical disk and means for reproducing recorded data recorded on the optical disk in response to the light beam reflected from the optical disk. A means for detecting a focus error of the focusing means in response to a light beam reflected from the optical disc, and a focusing means for the optical disc in response to the detected focus error depending on the type of the optical disc. Drive signal generating means for generating a drive signal for continuing to move to a different focus position and maintaining the focus position according to the optical disc; drive means for driving the light collecting means in response to the drive signal; An optical disc apparatus comprising: a unit for generating a signal for discriminating the type of the optical disc from a drive signal generated while being maintained at the in-focus position. It is.

Further, according to the present invention, the condensing means for condensing the first light beam toward the optical disc and the recording data recorded on the optical disc in response to the first light beam reflected from the optical disc. And a light source means for irradiating the optical disc with a second light beam, and a means for detecting the second light beam reflected from the optical disc to determine the type of the optical disc. A featured optical disk device is provided.

Furthermore, there is a shortest mark as the recording data, and the shortest mark has a focusing means for focusing a light beam toward an optical disc which differs depending on the type of the optical disc.
A means for rotating the optical disc, a means for reproducing the recording data recorded on the optical disc in response to the light beam reflected from the optical disc, a means for generating an identification signal according to the type of the optical disc, and a means for responding to the identification signal. An optical disk device is provided, which is a means for setting the number of rotations, and a setting means for setting the reproduction time of the shortest mark searched at the set number of rotations to be constant regardless of the type of the optical disk. It

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical disk device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an optical disk device for searching an optical disk compatible with high density recording according to an embodiment of the present invention. FIG. 2 shows an optical disc of high-density recording type which is loaded in the optical disc device shown in FIG.

In the optical disk device shown in FIG. 1, the optical disk 10 is placed on a spindle motor 12 driven by a motor drive circuit 11, and is rotated by the spindle motor 12. Optical discs of high-density recording type capable of high-density recording compared with CDs (compact discs) have various structures. For example, as shown in FIG. 2, recording is performed on a transparent substrate 14 having a thickness of 0.6 mm. A pair of structures 18, in which the layers, that is, the reflection layers 16 are formed, are prepared, and the pair of structures 18 are adhered to each other via the adhesive layer 20 so that the recording layer 16 is enclosed therein. In the optical disc 10 having such a double-sided structure, a center hole 22 into which the spindle of the spindle motor 12 is inserted is provided at the center thereof, and a clamping area 24 for holding the optical disc 10 at the time of rotation is provided around the center hole 22. Stipulated in. As described above, the high-density recording type optical disc 10 has a structure in which the structures 18 are laminated, and the transparent base of each structure 18 has a thickness of 0.6 mm.
It is. On the other hand, an ordinary CD (compact disc) has a single-layer structure in which a recording layer, that is, a reflective layer is provided on a transparent substrate, and the thickness of the transparent layer is the same as that of the high-density recording compatible optical disc 10. It is thicker than the other and has 1.2 mm.

The periphery of the optical disk 10 is usually defined as a lead-out area 26 in which no information is recorded, and a data recording area 28 is defined between the inner circumference of the lead-out area 26 and the outer circumference of the clamping area 24. There is. In the recording layer 16 of the data recording area 28, tracks are usually formed in a spiral shape as an area for recording data,
The continuous track is divided into a plurality of sectors, and preformatted data such as address data is recorded in advance in each sector as a physical state change such as a pit and main sector data is recorded in each sector as necessary. Similarly, sub-image data and audio data are recorded as physical state changes such as pits. This read-only optical disc 1
0 means that pit rows are formed in advance on the transparent substrate 14 by a stamper, a reflective layer is formed on the surface of the transparent substrate 14 on which the pit rows are formed by vapor deposition, and the reflective layer is formed as the recording layer 16. Become.

As shown in FIG. 1, in the optical disc reproducing apparatus for reproducing data from the optical disc 10 as described above, the optical disc 10 is searched by the optical disc 10 by the disc drive unit 30 for driving the optical disc. That is,
The optical disc 10 is placed on a spindle motor 12 driven by a motor drive circuit 11, and is rotated by the spindle motor 12. Optical disk 10
An optical head, that is, an optical pickup 32 for condensing a light beam, that is, a laser beam on the optical disc 10 is provided below the optical disc 10. The optical head 32 is mounted on a guide mechanism (not shown) so as to be movable in the radial direction of the optical disk 10 in order to search the information recording area 25, particularly the data recording area 28, and is driven by the drive circuit 37. The feed motor 33 driven by the drive signal moves the optical disk 10 in the radial direction. The objective lens 34 is held on the optical disc 10 so as to be movable along its optical axis.
In response to the drive signal from the focus drive circuit 36, the focus lens is moved in the optical axis direction, the objective lens 34 is always maintained in the focus state, and a minute beam spot is formed on the recording layer 16. The objective lens 34 is held so that it can be finely moved in the radial direction of the optical disc 10, is finely moved in response to a drive signal from the track drive circuit 38, and is always maintained in a tracking state so that the recording layer 16 of the optical disc 10 is maintained. The upper track is tracked with a light beam.

In the optical head 32, the light beam reflected from the optical disk 10 is detected, and the detected detection signal is supplied from the optical head 32 to the servo processing circuit 44 via the head amplifier 40. The servo processing circuit 44 generates a focus signal, a tracking signal and a motor control signal from the detection signal, and supplies these signals to the drive circuits 36, 38 and 11, respectively. Therefore, the objective lens 34 is maintained in the focus state and the tracking state, the spindle motor 12 is rotated at a predetermined rotation number, and the light beam causes the track on the recording layer 16 to be a light beam, for example, a constant linear velocity. Tracked in. System CP
When a control signal as an access signal is supplied from the U section 50 to the servo processing circuit 44, a movement signal is supplied from the servo processing circuit 44 to the drive circuit 37, and the optical head 32 is moved along the radial direction of the optical disc 10. A predetermined sector of the recording layer 16 is accessed, reproduction data is amplified by the head amplifier 40 and output from the disk drive unit 30. The output reproduction data is stored in the data RAM unit 56 via the system processor unit 54. The disk drive unit 30 and the system processor unit 54 are controlled by the system CPU unit 50 which is controlled by a program recorded in the system ROM and RAM unit 52. The reproduction data stored in the data RAM unit 56 is processed by the system processor unit 54 and classified into video data, audio data and sub-picture data. The video data, the audio data and the sub-picture data are respectively recorded in the video decoder unit 58, It is output to the audio decoder unit 60 and the sub-picture decoder unit 62 and decoded.
The decoded video data, audio data, and sub-picture data are converted into a video signal, an audio signal, and a sub-picture signal as an analog signal by the D / A and reproduction processing circuit 64, and are mixed to be a video signal and a sub-picture. The signal is supplied to the monitor 6, and the audio signal is supplied to the speaker 8. As a result, the monitor unit 6
The image is displayed on the screen and the sound is reproduced from the speaker unit 8.

Next, referring to FIG. 3, the head amplifier 40, the data processing circuit 42, and the servo processing circuit 4 shown in FIG.
4 will be described in detail. As shown in FIG. 3, the spindle motor 12 is controlled by the disc motor servo circuit 11 so that the disc 10 is moved to the system control circuit 5.
It is rotated at a predetermined rotation speed designated by 2. The optical pickup 32 has the objective lens 34 of the optical pickup 32 controlled by the optical pickup control circuit 50 including the servo processing circuit 44 and the drive circuits 36, 37 and 38 as described above.
Is directed to the target track and is maintained in a focused track state and a focused state. The detection signal detected by the optical pickup 32 is output from the optical pickup 32 as a signal whose intensity is also modulated because the intensity of the light beam is modulated in the pits formed on the track of the optical disc 10. The output detection signal is amplified by the preamplifier circuit 54, and the waveform of the amplified detection signal is adjusted by the waveform shaping circuit 56 and input to the PLL circuit 58. The PLL circuit 58 generates a sync pulse from the sync information included in the detection signal and supplies the sync pulse together with the detection signal to the discrimination circuit 60. Discrimination circuit 6
At 0, the detection signal is discriminated by the sync pulse to detect the code string. That is, the discrimination circuit 60 detects whether or not there is a reproduction pulse signal in the time zone determined by the discrimination circuit 60, that is, in the detection window, and generates a code string signal. The signal of this code string is demodulated into a data bit string in the decoder, and the demodulated data pit string is input to the error correction circuit 64 to cause an error in the signal due to a defect such as dust or scratches generated on the optical disk 10. Is corrected and output as reproduced data.

In the optical pickup control circuit 50, the detection signal from the optical pickup 32 is forwarded as shown in FIG.
It is supplied to the residue error signal generator 72 and the LD and tracking servo circuit 74. In the LD and tracking servo circuit 74, a laser control signal that stabilizes the output of a semiconductor laser as a laser source provided in the optical pickup 32 is generated from the detection signal, and a track on the optical disc 10 is tracked and controlled by the laser beam. A tracking error signal for
Be fed back to. A semiconductor laser drive circuit (not shown) is driven in response to the laser control signal to stabilize the output from the semiconductor laser, and a tracking drive signal is generated from the track drive circuit 34 in response to the tracking error signal to generate the objective lens 34. Is moved and the track is tracked.

In addition, the focus signal generator 72 generates a focus error signal from the detection signal, and the focus error signal is compensated by the compensating circuit 76 to drive the drive circuit 3.
A focus driving signal is generated from the objective lens 34.
Is driven. The objective lens 34 is usually fixed to a lens barrel by a coil (not shown) to which a focus driving signal is supplied, and this coil gives a magnetic field to the permanent magnet (not shown). ) Is included in the magnetic circuit. Normally, the objective lens 34 is located at the home position in the optical axis direction, and when the focus driving signal is supplied to the coil, the objective lens 34 is moved in the optical axis direction to the focus position. Therefore, the DC bias drive signal, that is, the DC offset voltage is continuously applied to the coil while the objective lens 34 is arranged at the focus position. As described above, the high-density recording type optical disc 10 has a transparent substrate having a thickness of 0.6 mm, while the CD (compact disc) has a transparent substrate having a thickness of 1.2 mm, which is thicker than this. ing. Therefore, when focusing on the high-density recording compatible optical disk 10 and focusing on the CD, the optical path length of the laser beam at the time of focusing changes, and the focus position of the objective lens 34 also changes. As a result, the DC offset voltage supplied to the coil at the time of focusing differs when focusing on the high-density recording compatible optical disc 10 and when focusing on the CD.
This DC offset voltage changes when the type of optical disk changes.

This offset voltage is detected by the DC offset detection circuit 78, and the detected offset voltage is
The position detection circuit 80 converts the signal into a position signal related to the focus position of the objective lens 34. If it is determined from this position signal that the objective lens 34 is located at the focus position for the high-density recording compatible optical disc 10, the optical pickup 54 performs a search for the high-density recording compatible optical disc 10. In addition, the objective lens 34 moves from the position signal to the CD for the CD.
If it is found that the optical disc 54 is located at the waste position, it means that the optical pickup 54 is performing a search for the CD. This position signal is supplied to the system control device 52, and based on this position signal, as described above, in the system control device 52, the optical disk mounted on the spindle motor 12 is the high density recording compatible optical disk 10. Alternatively, the circuit system is switched to the reproduction system corresponding to the disc determined by discriminating whether the disc is a CD.

Next, another embodiment of the optical disk device capable of discriminating the loaded optical disk will be described with reference to FIGS. 4 and 5.
This will be described with reference to FIG. 4 and 5, the block circuits described in FIG. 3 are denoted by the same reference numerals as those in FIG. 3 and their description is omitted.

The apparatus shown in FIG. 4 is provided with a disc discriminating circuit 88 for directly optically detecting the thickness of the transparent substrate of the optical disc instead of detecting the DC offset voltage of the focus error signal. The disc discriminating circuit 88 includes a light source 8 which emits a light beam toward the optical disc 34.
2 and a detector 84 for detecting the reflected beam from the optical disc 34, and a signal detection circuit 86 for generating a signal for discriminating the optical disc by the detection signal from the detector 84.
Is provided. The detection signal from the signal detection circuit 86 is supplied to the system control unit 52 as in the embodiment of FIG. 3, and the system control unit 52 switches the circuit system to the reproduction system according to the type of optical disc.

The detection method shown in FIG. 4 is based on the principle shown in FIG. The light beam emitted from the light source 84 to the transparent layer 14 of the optical disc 34 as shown in FIG.
Although reflected by the reflective layer 16 and incident on the photodetector 86,
The high-density recording type optical disc 10 has a transparent substrate having a thickness of 0.6 mm, whereas a CD (compact disc)
Has a transparent base 1.2 mm thicker than this, the reflected light beam is incident on different areas of the detector 86. That is, as shown by the solid line in FIG. 5, the transparent substrate 14-1 of the optical disc 10 compatible with high density recording.
Since the thickness of the transparent base plate 14-2 of the CD indicated by and the broken line is different, the refraction positions where the light beams incident at the same incident angle are refracted by the transparent base plates 14-1 and 14-2, respectively. Is different for each transparent substrate 14-1, 14-2,
Also, the positions of the light beams from which the light beams appear from the transparent substrates 14-1 and 14-2 are the same as those of the transparent substrates 14-1 and 14-2, respectively.
-It is different for each 2. Therefore, even if the light beams emitted from the same light source 84, in other words, the same light spot, are irradiated on different areas on the detector 86 if the types of optical disks are different. In other words, different object points are produced on the detector 86. Therefore, if the irradiation position of the light beam on the detector 86 is known, the type of the optical disc 34 can be determined.

In the embodiment shown in FIG. 5, an example in which the light beam is incident on the transparent substrate regardless of whether the optical disc 10 is a high density recording type or a CD, is explained. Since the optical disc 10 has a laminated structure, a transparent substrate is provided on both sides, but in a CD, the transparent substrate is provided on only one side. Therefore, in the case of a CD, the reflectance on the back surface is lowered, and this reflectance is lowered, in other words, the light intensity of the reflected light beam is lowered by the detection system shown in FIG. May be determined. Normally, in a CD, a label or the like is provided on the back surface thereof, so it is more effective to discriminate the disc based on the difference in reflectance.

When the type of the optical disc is determined as described above, the system control circuit 52 rotates the optical disc at a rotation speed according to the type of the disc and reproduces information from the optical disc. That is, when the optical disc is a high density recording type optical disc 10 as shown in FIG. 6, the discrimination signal 1 is given from the system control circuit 52 to the disc reproduction speed setting circuit 90, and in response to the discrimination signal 1. Then, the first reproduction speed setting circuit 92 is operated. Therefore, the first reproduction speed setting circuit 92 generates a first reproduction speed setting signal, and the disk motor rotation speed control circuit 96 generates a first rotation speed setting signal based on this signal, thereby performing system control. It is given to the disk motor servo circuit 11 via the circuit 52. As a result, the spindle motor 12 is rotated at the first rotation speed, and the pits of the optical disc are searched at the first reproduction speed. Similarly, the optical disc is C
If it is D, the discrimination signal 2 is the system control circuit 52.
Is supplied to the disc reproducing speed setting circuit 90, and the second reproducing speed setting circuit 94 is operated in response to the discrimination signal 1. Therefore, from the second reproduction speed setting circuit 94,
A reproduction speed setting signal is generated, and a second rotation speed setting signal is generated from the disk motor rotation speed control circuit 96 based on this signal and applied to the disk motor servo circuit 11 via the system control circuit 52. As a result, the spindle motor 12 is rotated at the second rotation speed, and the pits of the optical disc are searched at the second reproduction speed. Here, the first
The relationship between the reproduction speed and the second reproduction speed, that is, the relationship between the first rotation speed and the second rotation speed is that the minimum pit length recorded on the optical disk, that is, the reproduction time of the shortest mark is of a high-density recording type. It is set to be the same whether it is on the optical disc 10 or on the CD. By setting the first reproduction speed and the second reproduction speed in this way, waveforms can be shaped by the common waveform shaping circuit 56 even for optical disks of different types, and the circuit can be simplified.

[0025]

As described above, in the optical disc apparatus of the present invention, the types of optical discs can be discriminated even if they are different types of optical discs, and information can be searched appropriately according to the type. it can. Further, since the shortest marks are reproduced in the same reproduction time even in different optical disks, different optical disks can be waveform-shaped by a common waveform-shaping circuit, and the circuit configuration of the optical disk device can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram of an optical disk device for searching for an optical disk compatible with high density recording according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a high-density recording compatible optical disc loaded in the optical disc device shown in FIG.

3 is a block diagram showing an example of a circuit configuration of the optical disc device shown in FIG. 1. FIG.

FIG. 4 is a block diagram showing another embodiment of the circuit configuration of the optical disk device shown in FIG.

5 is an explanatory diagram for explaining the principle of the optical disc discriminating method in the optical disc device shown in FIG. 4. FIG.

6 is a block diagram showing still another embodiment of the circuit configuration of the optical disk device shown in FIG. 1. FIG.

[Explanation of symbols]

 10 ... Optical disc 14 ... Transparent substrate 32 ... Optical pickup 34 ... Objective lens 50 ... Optical pickup control circuit 56 ... Waveform shaping circuit 72 ... Focus error signal generation circuit 78 ... DC offset detection circuit 80 ... Position detection circuit 82 ... Light source 84 Photodetector 86 Signal detection circuit 90 Disc playback speed setting circuit 92 First playback speed setting circuit 94 Second playback speed setting circuit

Claims (8)

[Claims] 1. A means for converging a light beam toward an optical disc, a means for reproducing recorded data recorded on the optical disc in response to the light beam reflected from the optical disc, and a light beam reflected from the optical disc. Responsive to the focus error of the focusing means, and in response to the detected focus error, the focusing means is moved relative to the optical disc to a different focusing position depending on the type of the optical disc. Drive signal generating means for generating a drive signal for continuing to maintain the focus position according to the above, drive means for driving the condensing means in response to the drive signal, and while maintaining the focus position. An optical disc apparatus comprising: a unit for generating a signal for discriminating the type of the optical disc from the generated drive signal. 2. Further comprising: rotating means for rotating the optical disk; and means for setting a rotating speed according to the type discriminating signal to rotate the rotating means at the set rotating speed. The optical disk device according to claim 1. 3. Condensing means for converging a first light beam toward the optical disc; means for reproducing recorded data recorded on the optical disc in response to the first light beam reflected from the optical disc; An optical disk device comprising: a light source unit for irradiating an optical disk with a second light beam; and a unit for detecting the second light beam reflected from the optical disk to determine the type of the optical disk. 4. The discriminating means is a second disc from the optical disc.
4. The optical disk device according to claim 3, further comprising a detector for detecting the irradiation position of the light beam and the circuit for generating a signal for discriminating the type of the optical disk according to the detection signal from the detector. 5. The discriminating means is a second disc from the optical disc.
4. An optical disc apparatus according to claim 3, further comprising a detector for detecting the light intensity of the light beam of 1. and a circuit for generating a signal for discriminating the type of the optical disc in accordance with a detection signal from the detector. 6. A rotating means for rotating the optical disc, and a means for setting a rotating speed according to the type discrimination signal and rotating the rotating means at the set rotating speed. The optical disk device according to claim 3. 7. The recording data has a shortest mark, and the shortest mark is condensed from a condensing means for condensing a light beam toward an optical disc which differs depending on the type of the optical disc, a means for rotating the optical disc, and a reflection from the optical disc. Means for reproducing recording data recorded on the optical disc in response to the light beam, means for generating an identification signal according to the type of the optical disc, and means for setting the number of rotations according to the identification signal,
An optical disc apparatus comprising: setting means for selecting the reproduction time of the shortest mark searched at the set rotation speed to be constant regardless of the type of the optical disc. 8. The optical disk device according to claim 7, wherein the generating means identifies the type of the optical disk and generates an identification signal.