Optical disk device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an optical disc device, and more particularly to a video disc device for reproducing or recording information from an optical disc (Digital Video Disc: DVD) having a plurality of signal layers.

【0002】

[Conventional technology]

A CD-ROM is an optical disc with a thickness of about 1.2 mm, and information is read out using a semiconductor laser. In this optical disc, the pickup objective lens is subjected to focus servo and tracking servo to irradiate the pit row on the signal recording surface with a laser beam to reproduce the signal. In addition, recently, the density for recording a long-time moving image is increasing.

【0003】

For example, a DVD standard has been proposed that records 4.7 Gbytes of information on one side of an optical disc with a diameter of 12 cm, which is the same as a CD-ROM. The DVD disc thickness is about 0.6 mm, and by laminating both sides, a dual-layer disc can be constructed, and one dual-layer disc can record 9.4 Gbytes of information.

【0004】

In order to reproduce a dual-layer optical disc having these two signal recording surfaces, a method of reproducing two signal recording surfaces from one side of the disc and a method of reproducing one signal recording surface from both sides of the disc can be considered. .. However, the method of reproducing one signal recording surface from both sides is complicated because it is necessary to turn over the disk when trying to reproduce the other signal recording surface after the reproduction of one signal recording surface is completed. .. Further, it is not possible to reproduce the other signal recording surface while reproducing one signal recording surface. For this reason, the method of reproducing two signal recording surfaces from one side has become the mainstream.

【0005】

FIG. 8 is a cross-sectional view showing an outline of the structure of a single-sided reading dual-layer disc. As shown in FIG. 8, the two-layer disc is a reflective recording layer B made of aluminum and having a reflectance of 70% or more, and a translucent recording layer made of gold or the like and having a reflectance of about 30%. An ultraviolet curable resin having a thickness of about 40 μm is sandwiched between these two layers, including A, as an intermediate layer C.

【0006】

In addition, since one layer of this dual-layer disc is translucent, the information of that layer is picked up (PU) by irradiating a laser beam (beam) from one side and focusing on each layer. ) Can be read through.

【0007】

By the way, in a dual-layer disc, a so-called focus jump is performed in which the beam is refocused on the other layer while the one layer is being reproduced, and the pickup is moved to reproduce the other layer. Here, the movement of this pickup is started by applying an acceleration pulse to the focus actuator included in the pickup, and the movement is stopped by applying a deceleration pulse.

【0008】

FIG. 9 is a diagram for explaining a pickup control method in a conventional focus jump. At the focus error signal FE (also called S-curve signal) shown in Fig. 9 (a), a threshold value is set to 20% of the difference in peak values (P2-P1), and when this threshold value is exceeded ( Alternatively, at position), the signal supplied to the focus actuator of the pickup is switched from the acceleration pulse shown in FIG. 9 (b) to the deceleration pulse shown in FIG. 9 (c).

【0009】

[Problems to be Solved by the Invention]

However, there are cases where the surface of the disc is scratched and a pulse cannot be obtained from the reflective surface of the disc, or a pulse cannot be obtained from the reflective surface due to surface shake or impact. Since the focus error signal FE shown in FIG. 9 is obtained by detecting a pulse from the reflecting surface of the disk with a photodetector, if P1 in FIG. 9 is detected and then P2 is not detected, the focus is reached. A deceleration pulse cannot be given to the actuator, causing a malfunction in which the focus actuator collides with the disk.

【0010】

Therefore, a main object of the present invention is to provide an optical disk device capable of preventing malfunction of focus jump.

【0011】

[Means for solving problems]

The invention according to claim 1 is an optical disk device that reproduces an optical disk in which information is recorded on signal recording surfaces of a plurality of layers, and reads information by irradiating the optical disk with a beam and detecting the reflected light. When the information reading means and the information reading means are in focus on the signal recording surface of one of a plurality of layers, the information reading means generates an acceleration signal to focus on the signal recording surface of the other layer. The information reading means is stopped according to the fact that the predetermined reflected light is not obtained from the information reading means within a predetermined time after the acceleration signal is supplied to the information reading means from the accelerating means. It is configured to include a deceleration means for generating a deceleration signal for the purpose and giving it to the information reading means.

【0012】

The invention according to claim 2 is an optical disk device that reproduces an optical disk in which information is recorded on signal recording surfaces of a plurality of layers, and reads information by irradiating the optical disk with a beam and detecting the reflected light. When the information reading means and the information reading means are in focus on the signal recording surface of one of a plurality of layers, the information reading means generates an acceleration signal to focus on the signal recording surface of the other layer. Deceleration for stopping the information reading means in response to the fact that the information reading means does not obtain a predetermined level of reflected light after the acceleration signal is supplied to the information reading means from the accelerating means. It is configured to include a deceleration means for generating a signal and giving it to the information reading means.

【0013】

In the invention according to claim 3, the accelerating means according to claim 1 or 2 stops the information reading means by the decelerating means, and then generates an acceleration signal again and gives the information reading means to the information reading means.

【0014】

In the invention according to claim 4, the information reading means of claim 1 outputs an S-shaped curve signal as a signal indicating focusing, and the deceleration means does not obtain an S-shaped curve signal within a predetermined time. A deceleration signal is generated accordingly.

【0015】

In the invention of claim 5, the predetermined time of claim 1 is the time required to focus on the signal recording surface of the other layer by the acceleration signal when focusing on any of the plurality of layers. It is chosen several times.

【0016】

In the invention according to claim 6, the reflected light at a predetermined level according to claim 2 is selected to be a fraction of the level of the reflected light obtained from the information reading means.

【0017】

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, the single-sided read DVD dual-layer disc 1 is rotationally driven by the spindle motor 2, and the information recorded on the disc 1 is read by the pickup 3. A signal such as a focus error signal FE is output from the pickup 3, amplified by the head amplifier 4, and given to the A / D converter 5 to convert an analog signal into a digital signal. This digital signal is given to DSP (digital signal processor) 6.

【0018】

ROM7 and RAM8 are connected to DSP6. ROM7 stores the program for controlling the DSP, and RAM8 stores the information obtained from the disk 1. The DSP 6 executes a program stored in the ROM 7 and controls to specify the position of the pickup 3 by an acceleration signal or a deceleration signal based on the information stored in the RAM 8. The DSP 6 outputs a digital signal for its control to the D / A converter 9, and the D / A converter 9 converts the digital signal into an analog signal and gives it to the driver 10. The driver 10 controls the pickup 3 by the acceleration signal and the deceleration signal.

【0019】

FIG. 2 is a diagram showing the configuration of the pickup shown in FIG. In FIG. 2, pickup 3 includes, for example, a semiconductor laser 31 that emits a laser beam with a wavelength of 635 nm. The laser beam from the semiconductor laser 31 is incident on the liquid crystal panel 32, the polarizing surface is rotated, and the laser beam is incident on the half mirror 33. The half mirror 33 half-reflects the laser beam and causes it to enter the collimator lens 34, and the collimator lens 34 makes the laser beam parallel light and reflects it at 90 ° by the mirror 35. Then, the reflected laser beam passes through the polarizing plate 36, is focused by the objective lens 37, and irradiates the signal recording surface of the disk.

【0020】

The laser beam reflected by the signal recording surface returns through the objective lens 37, the polarizing plate 36, the mirror 35, and the collimator lens 34, is half-transmitted by the half mirror 33, and is focused and detected by the photodetector 38. .. The photodetector 38 is divided into four light receiving surfaces a to d, and a + b + c + d is the output light amount P, and (a + c)-(b + d) is the focus error signal FE ( It is output as an S-shaped curve signal).

【0021】

The liquid crystal panel 32 is configured by sandwiching a TN type liquid crystal between two pieces of glass with a transparent electrode. When a voltage is applied to the transparent electrode, a voltage is applied to the TN type liquid crystal, and the polarization plane of the laser beam is rotated. It passes through the TN type liquid crystal without being used. When no voltage is applied to the transparent electrode, the laser beam is rotated 90 ° in its polarized light and passes through the TN liquid crystal.

【0022】

FIG. 3 is a diagram showing a driving mechanism of an objective lens for focusing and tracking. In FIG. 3, the objective lens 37 shown in FIG. 3 is held by the lens holder 40, the focus coil 41 is wound around the lens holder 40, and both end surfaces of the focus coil 41 in the Y direction. Is provided with tracking coils 42a and 42b. The lens holder 40 is attached to the fixing base 44 via the leaf spring 43. Further, a yoke 46, 47 and a permanent magnet 48 are attached to the yoke base 45, and the tip of the yoke 47 is inserted into the space between the lens holder 40 and the focus coil 41.

【0023】

When the focus coil 41 is driven, the lens holder 40 moves in the Z direction due to the action of the magnetic flux of the permanent magnet 47 and the magnetic flux generated by the current flowing through the focus coil 41 so that the laser beam is focused on the signal recording surface of the disk. Is controlled by. When the tracking coils 42a and 42b are driven, the lens holder 40 is tracked in the Y direction.

【0024】

FIG. 4 is a flowchart for explaining the operation of the embodiment of the present invention, and FIG. 5 is a diagram for explaining the operation of the embodiment of the present invention.

【0025】

In this embodiment, after giving an acceleration signal to the pickup 3, the focus jump is controlled and the timer count is started, and if a certain period of time has elapsed, the focus jump is performed in the opposite direction. More specifically, as shown in FIG. 5, the disc has an N-1 layer, an N layer, and an N + 1 layer, and after the pickup 3 has a focus jump from the N-1 layer to the N layer. , Focus jump to N + 1 layer.

【0026】

DSP6 outputs an acceleration signal at the timings a to b of the focus error signal FE shown in FIG. 5 in order to make a focus jump from the N layer to the N + 1 layer. This acceleration signal is converted into an analog signal by the D / A converter 9, amplified by the driver 10, and the focus coil 41 shown in FIG. 3 is driven. At this time, DSP6 starts after resetting the built-in timer. This timer may be configured by hardware such as a counter, or may be one that counts time by software.

【0027】

DSP6 determines whether the count value of the timer exceeds the predetermined value Tout. If Tout is not exceeded, the level of the focus error signal FE is detected. Then, if the level of the focus error signal FE is the zero cross point shown at point c in FIG. 5, the focus jump ends. However, if the timer exceeds Tout, it is regarded as abnormal and a reverse jump is started to prevent the pickup 3 from colliding with the disk surface. Here, if the time required for the focus jump from the N layer to the N + 1 layer is, for example, 2 msec, Tout is selected, for example, several times as long as 5 msec.

【0028】

FIG. 6 is a block diagram showing a second embodiment of the present invention. In this embodiment, after the acceleration signal is output for the focus jump, when the light amount level exceeds a predetermined value, the focus jump is performed in the opposite direction. Therefore, as shown in FIG. 6, not only the focus error signal FE but also the light intensity signal p is output from the head amplifier 4, converted into a digital signal by the A / D converter 10, and given to the DSP 6. Other than that, the configuration is the same as in Fig. 1.

【0029】

FIG. 7 is a flowchart for explaining the operation of the second embodiment of the present invention. Next, the operation of this embodiment will be described with reference to FIG. 5 of the first embodiment. First, similarly to the first embodiment, the DSP 6 applies an acceleration signal to the D / A converter 9 to control the focus jump. The acceleration signal is converted into an analog signal by the D / A converter 9, amplified by the driver 10, and given to the focus coil 41 of the pickup 3. The photodetector 38 detects the reflected light from the disk, and the head amplifier 4 outputs the light amount signal p and the focus error signal FE. Each signal is converted into a digital signal by A / D converters 10 and 5 and given to DSP6. DSP6 measures the light intensity signal p and compares it with the predetermined light intensity value Pout shown in FIG. If the light intensity signal p is smaller than the predetermined light intensity value Pout, the level of the focus error signal in the N + 1 layer is detected. If the level is the zero cross point at point c shown in Fig. 5, the focus lamp is terminated.

【0030】

However, if the light intensity signal p exceeds the light intensity value Pout, it is determined to be abnormal, a reverse jump is started, and the pickup 3 is prevented from colliding with the disc.

【0031】

[Effect of the invention]

As described above, according to the present invention, when an acceleration signal is applied to focus on the signal recording surface of the other layer while focusing on the signal recording surface of any layer of the optical disc. When the reflected light is not obtained within a predetermined time or when the reflected light of a predetermined level is not obtained, a deceleration signal is given to the information reading means to decelerate the light, thereby preventing the optical disc from colliding with the optical disk. be able to.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows one Embodiment of this invention.

[Figure 2]

It is a figure which shows the structure of the pickup shown in FIG.

[Fig. 3]

It is a figure which shows the drive mechanism of the objective lens for focusing and tracking.

[Fig. 4]

It is a flowchart for demonstrating operation of one Embodiment of this invention.

[Fig. 5]

It is a figure for demonstrating operation of one Embodiment of this invention.

[Fig. 6]

It is a block diagram which shows the 2nd Embodiment of this invention.

[Fig. 7]

It is a flowchart for demonstrating operation of 2nd Embodiment of this invention.

[Fig. 8]

It is sectional drawing which shows the outline of the structure of the single-sided reading double-layer disc.

[Fig. 9]

It is a timing diagram for demonstrating the control method of the pickup in the conventional focus jump.

[Explanation of symbols]

1 Dual-layer disk 2 spindle motor 3 pickup 4 head amp 5,10 A / D converter 6 DSP 7 ROM 8 RAM 9 D / A converter 10 driver 31 semiconductor laser 32 LCD panel 33 Half mirror 34 Collimator lens 35 mirror 36 Polarizing plate 37 Objective lens 38 photodetector 40 lens holder 41 Focus coil 42a, 42b tracking coil 44 Fixed base 45 York base 46,47 York 48 Permanent magnet