JPH0668506A - Optical disk reproduction device - Google Patents

Abstract

PURPOSE:To recognize and reproduce an optical disk of a different track pitch automatically. CONSTITUTION:A laser diode in an optical block 5 irradiates a laser beam to a track pitch identification information index part formed on an optical disk 1 or 2. Furthermore, a pickup in the optical block 5 reads an RF signal such as an information signal. A signal level discrimination circuit 12 discriminates a level of an RF signal detected by an optical block 5. A CPU 13 discriminates whether a track pitch of the optical disk 1 or 2 is narrow or wide depending on a level discriminated by the signal level discrimination circuit 12 to control a changeover switch 9. The tracking control based on a tracking error detected by a tracking error detection section in the optical block 5 is implemented based on a track pitch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus for reading an information signal from an optical disk which is a disk-shaped recording medium.

[0002]

2. Description of the Related Art Conventionally, there has been proposed an optical disk reproducing apparatus for reading an information signal from an optical disk which is a disk-shaped recording medium. This optical disk reproducing device irradiates a light beam having a constant optical output to the signal recording layer so that the information recording signal can be read from a disc-shaped recording medium having a signal recording layer made of a metal material. The reflected light flux is detected.

The above-mentioned optical disc has a disc substrate made of a transparent material and a signal recording layer made of a metal material adhered to the disc substrate. An optical disc having a signal recording layer made of a metal material is a recording disc dedicated to reading information signals, and writing of information signals to the recording disc is performed by means of injection molding or the like when the disc substrate is manufactured.

On the signal recording layer of the above-mentioned optical disc, the signal is recorded as one track which is connected in a "spiral shape". The distance between the tracks (referred to as track pitch) is fixed and is currently 1.6 μm.

The track pitch is an important factor for improving the recording density of the signal recorded on the signal recording layer of the optical disc as well as the size of the uneven pits forming the track. That is, the high density of the optical disc can be achieved by reducing the pit size and the track pitch.

Since the total number of tracks can be increased by decreasing the track pitch of the optical disk, the density of the optical disk can be increased. Therefore, it is considered to set the track pitch to 1.4 μm, for example.

[0007]

By the way, as described above, the track pitch is set to, for example, 1.4 in order to increase the density.
When reproducing the next-generation optical disc having a size of μm and the existing optical disc having a track pitch of 1.6 μm, an optical disc reproducing device for performing tracking according to each track pitch is required.

The track pitch is, for example, 1.6 μm,
If two types of optical disc reproducing apparatuses are required to reproduce two types of optical discs of 1.4 μm, the burden on the consumer will be heavy.

Therefore, in one type of optical disc reproducing apparatus, the track pitch is, for example, 1.6 μm or 1.4 μm.
It is conceivable to reproduce two types of optical discs, but it is necessary to adjust the tracking gain in order to perform tracking according to each track pitch.

The present invention has been made in view of the above situation, and automatically switches the tracking gain according to the track pitch of the optical disk to reproduce, for example, two kinds of optical disks having different track pitches. It is an object of the present invention to provide a possible optical disk reproducing device.

[0011]

An optical disk reproducing apparatus according to the present invention is an optical disk reproducing apparatus capable of mounting optical disks having different track pitches, and a reading means for reading an information signal from the optical disk and the track pitch. Light flux irradiating means for irradiating the track pitch identification information marking portion provided on the optical disc with a light flux for identifying the difference between the two, and a light flux detection for detecting a reflected light flux of the light flux from the track pitch identification information marking portion. Means for Solving the Problems The present invention is characterized by comprising means and a gain switching means for switching a gain relating to tracking servo control according to track pitch identification information obtained based on a detection result of the reflected light flux by the light flux detection means.

Here, the track pitch identification information marking portion provided on the optical disc marks information relating to the track pitch as an uneven pattern or code data.

[0013]

In the optical disk reproducing apparatus according to the present invention, the light flux emitted from the light flux irradiating means to the track pitch identification information indicating portion provided on the optical disk is reflected by the light flux emitted from the track pitch identifying information indicating portion. Since the gain relating to the servo control of tracking is switched according to the track pitch identification information obtained by the detection means, the tracking gain according to the track pitch of the optical disc can be obtained, and for example, two types of different track pitches can be obtained. The optical disc of can be reproduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of an optical disk reproducing apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. In FIG. 1, in this embodiment, a read-only optical disk 1 or optical disk 2 having a disk substrate made of a transparent material such as polycarbonate and having a different track pitch is mounted. The optical disc 1 has a track pitch of 1.4 μm, and the optical disc 2 has a track pitch of 1.6 μm. That is, the optical disc 2 is formed with a track width of the present wide track, and the optical disc 1 is formed with a narrow track pitch of the next generation.

As shown in FIG. 2, the optical disc 1 has a main surface portion on one side as a signal reading surface 1a.
The signal reading surface 1a is formed by depositing a signal recording layer made of a metal material on the other main surface portion of the disk substrate. This signal recording layer is formed by following the so-called signal pits, which are concaves and convexes corresponding to the information signals formed on the other main surface portion of the disk substrate by means such as injection molding. That is, the reading of the information signal from the signal recording layer is performed through the signal reading surface 1a through the disc substrate.

Further, the optical disc 1 is provided with a chucking hole 1b at the center thereof for facilitating mounting and holding in the present embodiment. The reading of the information signal from the signal recording layer of the optical disc 1 is performed by focusing and irradiating the signal recording layer with a laser beam, and detecting the reflected light flux of the laser beam from the signal recording layer. On the signal recording layer, the laser beam causes a change in the amount of returning light due to a diffraction phenomenon according to the unevenness of the signal recording layer. Therefore, the information signal can be read by detecting the change in the light intensity of the reflected light flux.

On the inner peripheral side of the signal reading surface 1a of the optical disc 1, there is formed a groove portion 21 which serves as a track pitch identification information indicating portion for indicating information about the track pitch. The groove portion 21 is provided between the signal recording area on the signal recording layer and the chucking hole 1b, and identification information regarding the track pitch is marked as an uneven pattern. As shown in FIG. 3, the concave-convex pattern is formed so as to surround the chucking hole 1b over the entire circumference along the recording track 22. The groove portion 21 which is the track pitch identification information indicating portion diffracts the light flux for reading the information signal such as the laser beam when the light flux is irradiated. Therefore, the reflected light flux of the light flux in the portion where the groove portion 21 is provided has a lower light intensity than the reflected light flux of the light flux in the portion where the groove portion 21 is not provided.

As shown in FIG. 4, the optical disc 2 has a principal surface portion on one side as a signal reading surface 2a as in the optical disc 1, and a signal recording made of a metal material on the principal surface portion on the other side of the disc substrate. The layers are formed by deposition. Then, the reading of the information signal from the signal recording layer is performed by the signal reading surface 2a.
The disk substrate is used as a watermark. Further, the optical disc 2 is provided with a chucking hole 2b at the center thereof so that the optical disc 2 can be easily mounted and held in the present embodiment. The reading of the information signal from the signal recording layer of the optical disc 2 is similar to that of the optical disc 1.

In the signal recording layer of the optical disc 2, the portion corresponding to the track pitch identification information indicating portion in which the groove portion 21 of the optical disc 1 is formed, that is, the peripheral portion of the chucking hole 2b is the track pitch. Although it is an identification information display part, it is formed into a flat mirror surface. That is, the reflected light flux of the light flux at the track pitch identification information indicating portion of the optical disc 2 has a stronger light intensity than the reflected light flux of the light flux at the track pitch identification information indicating portion of the optical disc 1.

That is, the track pitches of the optical disc 1 and the optical disc 2 can be identified by the presence or absence of the groove portion 21. In the above description, since the optical disc 1 is provided with the groove portion 21 and the optical disc 2 is not provided, the light flux in the track pitch identification information indicating portion, which is the peripheral portion of the chucking holes 1b, 2b. By comparing the light intensities of the reflected light fluxes of the above, the optical disc 1 having a narrow track pitch (1.4 μm) and the wide track pitch (1.6 μm)
The optical disc 2 can be discriminated.

The present embodiment is configured to use the above-mentioned optical disc 1 and optical disc 2 as a recording medium. As shown in FIG. 1, this embodiment has a disc table 3 for mounting and mounting either the optical disc 1 or the optical disc 2. The disc table 3 is formed in a substantially disc shape, and a positioning protrusion provided at the center is inserted into the chucking holes 1b and 2b to position and hold the optical disc 1 or the optical disc 2. The table 3 is rotatable by a spindle motor 4.

Further, in this embodiment, the signal reading surface 1a or the signal reading surface 2a of the optical disk 1 or the optical disk 2 mounted on the disk table 3 is used.
An optical block 5 is provided so as to face the. The optical block 5 includes a reading means for reading an information signal from the optical disc 1 or the optical disc 2, a luminous flux radiating means for radiating a luminous flux to the track pitch identification information indicating portion, and a track pitch identification information indicating portion. A light flux detecting means for detecting a reflected light flux of the light flux, a tracking error detecting means for detecting a tracking error signal from a detection signal from the light flux detecting means, and a focus error detecting means for detecting a focus error signal from the detection signal. is there.

The optical block 5 has a laser diode which serves as a light source, a photodetector, an objective lens, a tracking error detection circuit, and a focus error detection circuit. The light flux emitted from the laser diode is guided to various optical devices in an optical pickup device (not shown) in the optical block 5, and is guided by the objective lens to the optical disc 1 or the optical disc 2.
The light is focused and irradiated on the signal recording surface of. This objective lens can be moved and operated in two directions of an optical axis direction and a direction orthogonal to the optical axis direction by an objective lens driving device (not shown). The light beam condensed by the objective lens on the signal recording surface of the optical disk 1 or the optical disk 2 is re-incident on the objective lens as a reflected light beam reflected by the signal recording surface. The light intensity of this reflected light flux is detected by the photodetector. The photodetector is
The light intensity of the reflected light flux is output as an electric signal.

Then, the tracking error detection circuit detects a tracking error signal from the electric signal corresponding to the light intensity detected by the photodetector, and supplies the tracking error signal to a tracking servo system described later.
Further, the focus error detection circuit detects a focus error signal from the electric signal corresponding to the light intensity and supplies the focus error signal to a focus servo system (not shown).

The electric signal output from the photodetector of the optical block 5 is supplied to the tracking error detection circuit and the focus error detection circuit, and the output terminal 1
6 and a signal level determination circuit 12 described later.
The information signal read from the optical disk 1 or the optical disk 2 is output from the output terminal 16.

The tracking servo system has an automatic gain control (AGC) circuit 6 for preventing a tracking error signal from changing due to reflectance, and a narrow track pitch, that is, when the optical disc 1 is mounted. The first servo amplifier circuit 7 for giving the servo amplification gain G _a to the tracking error signal, and the servo amplification gain G _{b for the} tracking error signal when the track pitch is wide, that is, when the optical disc 2 is mounted.
A second servo amplifying circuit 8 for giving the following, a changeover switch 9 as a gain changing means for changing over two tracking control signals which are the outputs of the first servo amplifying circuit 7 or the second servo amplifying circuit 8, and the above It comprises a phase compensation circuit 10 for causing the tracking drive coil of the objective lens drive device to perform the phase compensation for tracking through the tracking drive circuit 11 according to the tracking control signal selected by the changeover switch 9.

The signal level discriminating circuit 12 discriminates the signal level of the electric signal sent from the photodetector and sends the result to the central processing unit (CPU) 13. The CPU 13 controls the objective lens driving device in the optical block 5 via the tracking servo system based on the signal level discrimination by the signal level discriminating circuit 12. That is, the CPU 13 serves as identification means for identifying the track pitch identification information based on the detection result of the reflected light flux by the photodetector in the optical block 5. Further, the CPU 13 controls the output light of the laser diode in the optical block 5 via the amplifier 14. Further, the CPU 13 controls the rotation speed of the spindle motor 4 via the amplifier 15.

In the discriminating mode for discriminating whether the disc mounted on the disc table 3 is the optical disc 1 having a narrow track pitch or the optical disc 2 having a wide track pitch, that is, discriminating the track pitch. First, the CPU 13 sends the optical pickup device in the optical block 5 to a position facing the track pitch identification information indicating portion, that is, to the innermost side of the optical disc 1 or the optical disc 2.
Then, the CPU 13 causes the laser diode to emit a luminous flux having a constant light output. At this time, the optical disc 1 or the optical disc 2 may be rotated by the disc table 3 or may be stopped.

The light flux emitted to the track pitch identification information marking portion returns to the optical pickup side as a reflected light flux with a light amount corresponding to the state of the uneven pattern portion of the track pitch identification information marking portion. Then, the reflected light flux is converted into an electric signal according to the light amount by the photodetector. The output signal of the photodetector, which has a level corresponding to the light amount of the reflected light flux, is sent to the signal level determination circuit 12. This signal level discrimination circuit 12
The electric signal is compared with a predetermined reference level, and the result of this comparison is sent to the CPU 13. The CPU 13 discriminates whether the track pitch is narrow or wide based on the comparison result with the predetermined level of the electric signal sent from the signal level discrimination circuit 12.

For example, when the optical disk mounted on the disk table 3 is the first optical disk 1 having a narrow track pitch, the CPU 13 causes the CPU 13 to determine that the electric signal sent from the signal level discriminating circuit 12 has a predetermined value. By obtaining the comparison result of being lower than the reference level, it is identified that the track pitch of the optical disk 1 is narrow, and the movable contact 9c of the changeover switch 9 is brought into contact with the fixed contact 9a.
Then, the tracking control signal from the first servo amplifier circuit 7 is supplied to the phase compensation circuit 10. This phase compensation circuit 10 uses the tracking drive circuit 1 based on the tracking control signal corresponding to a narrow track pitch.
The tracking drive coil is subjected to tracking phase compensation via 1.

Further, for example, when the optical disk mounted on the disk table 3 is the optical disk 2 having a wide track pitch, the CPU 13 causes the CPU 13 to determine the electric signal sent from the signal level discriminating circuit 12 as a predetermined reference. A comparison result that the level is higher than the level is obtained, it is identified that the track pitch of the optical disk 2 is wide, and the movable contact 9c of the changeover switch 9 is brought into contact with the fixed contact 9b.
Then, the tracking control signal from the second servo amplifier circuit 8 is supplied to the phase compensation circuit 10. The phase compensation circuit 10 uses the tracking drive circuit 1 based on the tracking control signal corresponding to a wide track pitch.
The tracking drive coil is subjected to tracking phase compensation via 1.

Here, when the track pitch is different,
Well known about one of the reasons why the tracking gain changes
It will be explained based on the tracking by the three-beam method.
It First, the method called the three-beam method is shown in FIG.
The diffraction grating 31 is placed in the forward path of the light flux so that
The first-order diffracted light is created and the objective lens 32
The optical disc on which the track 34 on which the tracks 33 are arranged is formed
Light spot G on top ₊, Light spot G₀And light spots
G_-The three light spots of
G₊And G_-Method for tracking error detection
Is. That is, the light spot G₊On the photo detector
The signal detected from the reflected light spot is I₊, Again, light
Pot G_-Detection from reflected light spot on photo detector
I_-Then, the tracking error signal I
_tIs I_t= I₊-I_- Becomes

Track by the three-beam method as described above
For tracking optical discs with different pitches
The details will be described below. FIG. 6A shows between tracks of width T
Track pitch t_p0Tracking error signal when the range is wide
It shows the case of trying to detect an issue. In FIG. 6A,
Light spot G ₊, Light spot G₀And light spot G_-of
An inclined line and a light spot G shown by a chain line connecting the center points₀
Angle from the center point of the track to the baseline indicated by the broken line in the track direction
Is θ₀And the above light spot G₊And light spot G_-
Is not on the next track.

FIG. 6B shows a track between tracks having a width T.
Pitch t_p1Detects tracking error signal when the distance is narrow
Here is the case to try. In FIG. 6B, the optical spot
G ₊, Light spot G₀And light spot G_-The center point of
Inclination line and light spot G shown by the chain line₀Center point of
From the track direction to the baseline indicated by the broken line is θ₁so
Yes, the above light spot G₊And light spot G_-Next to
Not hanging on the rack. However, as shown in A of FIG.
Angle θ₀As it is (the optical spot shown by the broken line in B of FIG. 6)
G₊And light spot G_-) Tracking error signal
Is there a light spot on the next track?
Will end up. From this, the track pitch was different
Sometimes, if you do not change the arrangement angle of each light spot,
It turns out that the tracking gains also differ.

As described above, according to the present embodiment, the narrow or wide track pitch of the optical disk 1 or the optical disk 2 mounted on the disk table 3 can be identified, and the tracking servo can be performed based on the identification information. Since it is controlled, tracking can be performed according to the track pitch.

Needless to say, the present invention is not limited to the above-mentioned embodiment. For example, the track pitch identification information indicating portion is constituted by using code data instead of the concavo-convex pattern. You may.

[0037]

In the optical disk reproducing apparatus according to the present invention, the reading means reads the information signal from the optical disk, and the luminous flux irradiating means tracks provided on the optical disk for identifying the difference in track pitch. The pitch identification information marking portion is irradiated with a luminous flux, the luminous flux detection means detects the reflected luminous flux of the luminous flux from the track pitch identification information marking portion, and the gain switching means is based on the detection result of the reflected luminous flux in the luminous flux detection means. Since the gain relating to the servo control of tracking is switched according to the track pitch identification information obtained as described above, the tracking gain can be automatically selected according to the track pitch of the optical disc. Therefore, for example, two types of optical discs having different track pitches can be reproduced.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining a configuration of an embodiment of an optical disc reproducing device.

FIG. 2 is a diagram showing a configuration of an optical disc having a narrow track pitch that is mounted in this embodiment.

FIG. 3 is a diagram showing a configuration of a track pitch identification information marking portion of an optical disc having a narrow track pitch mounted in this embodiment.

FIG. 4 is a diagram showing a configuration of an optical disc having a wide track pitch that is mounted in this embodiment.

FIG. 5 is a diagram for explaining tracking control by a three-beam method.

FIG. 6 is a diagram for explaining a change in tracking gain due to a difference in track pitch.

[Explanation of symbols]

 1 ... Optical disc with narrow track pitch 2 ... Optical disc with wide track pitch 3 ... Disc table 4 ... Spindle motor 5 ... Optical block 6 ... ..Automatic gain control circuit (AGC) 7 ... First servo amplifier circuit 8 ... Second servo amplifier circuit 9 ... Changeover switch 10 ... Phase compensation circuit 11 ... ..Tracking drive circuit 12 ... Signal level determination circuit 13 ... Central processing unit (CPU)

Claims (1)

[Claims] 1. An optical disk reproducing apparatus in which optical disks having different track pitches can be mounted, and a reading means for reading an information signal from the optical disk, and a reading means provided on the optical disk for identifying the difference between the track pitches. Light flux irradiating means for irradiating the track pitch identification information marking portion with a light flux, light flux detecting means for detecting the reflected light flux of the light flux from the track pitch identifying information marking portion, and detection of the reflected light flux in the light flux detecting means. An optical disk reproducing apparatus, comprising: a gain switching unit that switches a gain relating to tracking servo control according to track pitch identification information obtained based on the result.