JPH08185637A - Focus controller - Google Patents

Abstract

PURPOSE: To provide a focus controller capable of performing a re-focusing to an original recording layer even when the out-of-focus occurs while reproducing a multilayers optical disk. CONSTITUTION: This controller is provided with a first comparator 9 and a second comparator 11 to which a focus error signal is supplied through an input terminal 1. The controller is provided with an out-of-focus detection circuit 3 detecting the out-of-focus by comparing a first reference voltage 10 and a second reference voltage respectively supplied from a first reference voltage generation circuit 10 and a second reference voltage generation circuit 12 with the focus error signal by these first comparator 9 and second comparator 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer optical disc recording apparatus and a multi-layer optical disc for recording / reproducing recorded data to / from a multi-layer optical disc of a plurality of recording layers, for example, a magneto-optical recording type, a pit recording type, etc. The present invention relates to a focus control device suitable for being provided as a focus control system for a reproducing device and a multilayer optical disk recording / reproducing device, and in particular, focusing from a recording layer currently being recorded or reproduced to another recording layer due to vibration or the like during recording or reproduction. The present invention relates to a focus control device that detects an out-of-focus condition that causes an out-of-focus condition, and refocuses the original recording layer.

[0002]

2. Description of the Related Art Conventional optical disks are generally single-layer optical disks having only one recording layer. When reproduction is started, an optical disk reproducing apparatus for reproducing recorded data from a single-layer optical disk first drives a focus actuator of an optical pickup with a triangular wave of about 2 Hz in order to perform focusing. As a result, the focus of the laser beam fluctuates near the in-focus point according to the triangular wave.

Here, when such focus movement control is performed and just focus is achieved, the sum signal (RF signal) should be at or above a predetermined level and the focus error signal should be at zero level.

Therefore, the optical disk reproducing apparatus detects the RF signal, compares the RF signal with a reference voltage of a predetermined level, and detects a focus error signal. Then, the zero level of the focus error signal is detected while the RF signal exceeds the level of the reference voltage,
The focus servo is pulled in at the timing when the focus error signal becomes zero level.

Thus, the focus servo can be pulled in at the timing when the focus actuator reaches the in-focus point, and thereafter, the recording data can be reproduced while correcting the focus error.

[0006]

Here, in recent years, in order to increase the capacity of an optical disk, a multilayer optical disk 20 having a multilayer structure as shown in FIG. 7 in which a plurality of recording layers are laminated has been proposed. There is. This multilayer optical disc 20
Is formed by laminating, for example, first to fourth recording layers 61 to 64 between the transparent substrate 60 and the aluminum reflective layer 65. The first to fourth recording layers 61 to 64 have light transmittances decreasing in order, respectively, and are arranged between the first and second recording layers 61 and 62, the second and third recording layers 62, During 63
Further, spacers 66 to 68 made of transparent resin are provided between the third and fourth recording layers 63 and 64, respectively.

When recording data is reproduced from such a multi-layered optical disc 20, the reproduction is performed by focusing on a desired recording layer. It is considered that dust, scratches, etc. or impact on the reproducing device causes the recording layer to be out of focus from the desired recording layer, which causes the recording layer other than the recording layer being reproduced to come into focus and be reproduced as it is. To be Then, when such out-of-focus occurs, the focus needs to be adjusted to the original recording layer that was being reproduced.

The present invention has been made in view of the above-mentioned problems, and when defocus occurs during reproduction of an optical disc having a multilayer structure, this is detected, and the defocus is reproduced before the defocus. It is an object of the present invention to provide a focus control device that can be adjusted to the original recording layer.

[0009]

A focus control device according to the present invention is a focus control device for performing focus control on a multi-layered optical disc in which a plurality of recording layers are stacked. There is an out-of-focus detection unit that detects out-of-focus when the recording layer being recorded or reproduced is in focus by comparing the level of the supplied focus error signal with a reference signal of a predetermined level.

Further, the focus control apparatus according to the present invention is a recording layer detecting means for detecting a recording layer currently being recorded or reproduced, and a recording currently being recorded or being reproduced detected by the recording layer detecting means. When out-of-focus is detected by the storage means for storing the original recording layer information indicating the layer and the out-of-focus detection means, the original recording layer information is read from the storage means and is recorded or reproduced by the out-of-focus. The recording layer which is recorded or reproduced by the defocus from the data of the recording layer and is recorded or reproduced before the defocus occurs based on the detected data and the original recording layer information. And a control means for performing focus control so as to refocus.

[0011]

A focus control device according to the present invention is a focus control device for performing focus control on a multi-layered optical disk having a plurality of recording layers stacked, wherein the out-of-focus detection means externally performs the recording or reproduction. By comparing the level of the supplied focus error signal with a reference signal of a predetermined level, it is possible to detect an out-of-focus state where the recording layer being recorded or reproduced is focused on another recording layer.

Further, in the focus control device according to the present invention, when the recording layer detecting means detects the recording layer which is currently being recorded or reproduced, the storage means stores this as the original recording layer information.

When the out-of-focus detection means detects out-of-focus, the control means reads out the original recording layer information from the storage means, and from the data of the recording layer recorded or reproduced by the out-of-focus operation. A recording layer that is being recorded or reproduced due to the defocus, and based on the detection data and the original recording layer information, the recording layer that was recorded or reproduced before the defocus is refocused. Focus control as follows.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a focus control device according to the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, the focus control apparatus according to the embodiment of the present invention includes an input terminal 1 for a focus error signal to which an external focus error signal during recording or reproduction is supplied, and the input terminal. An out-of-focus detection circuit 3 for detecting out-of-focus based on a focus error signal supplied via 1 and a recording layer designating section 5 for designating a recording layer for reproducing or recording.

Further, the focus control device focuses the original recording layer on the memory 6a for storing the original recording layer data indicating the recording layer designated by the recording layer designating section 5 and the out-of-focus state. An acceleration / deceleration pulse generation circuit 7 for outputting an acceleration / deceleration pulse for re-application, a focus error signal supplied via the input terminal 1 during the recording or reproduction, and an acceleration / deceleration pulse from the acceleration / deceleration pulse generation circuit 7 Changeover switch 8 for switching and outputting
And a system controller 6 that controls the changeover of the changeover switch 8 based on the detection output from the out-of-focus detection circuit 3.

The focus control device according to the embodiment having such a structure can be applied as the focus control unit 36 of the optical disk reproducing device as shown in FIG.

The operation of the focus control apparatus (focus control section 36) according to this embodiment will be described below including the operation of the optical disk reproducing apparatus.

First, in FIG. 2, when reproduction is started, a laser beam is emitted from the laser light source 21. This laser beam is collimated by the collimator lens 22 and is incident on the diffraction grating 23.

The optical disk reproducing apparatus is adapted to detect a tracking error by the so-called three-spot method. Therefore, the diffraction grating 23 splits the laser beam into zero-order light and ± first-order light and emits the light. The laser beam divided into three is incident on the polarization beam splitter 24.

The polarization beam splitter film 24a of the polarization beam splitter 24 has a characteristic of transmitting the so-called P-polarized component light and reflecting the S-polarized component light having a polarization direction orthogonal to the P-polarized component. There is. Since most of the laser beam has a P-polarized component, most of the laser beam incident on the polarization beam splitter 24 passes through the polarization beam splitter 24. The laser beam transmitted through the polarization beam splitter 24 is incident on the quarter wavelength plate 25. The quarter-wave plate 25 circularly polarizes the laser beam of the P-polarized component, which is linearly polarized light, and emits it. The circularly polarized laser beam is focused by the objective lens 26 and applied to the multilayer optical disc 20.

Next, the single layer optical disc 20 is irradiated with a laser beam to generate reflected light. This reflected light is made incident on the quarter-wave plate 25 via the objective lens 26, is made into linearly polarized light of the S-polarized component by the quarter-wave plate 25, and is made incident on the polarization beam splitter 24.

As described above, the polarization beam splitter film 24a of the polarization beam splitter 24 has a characteristic of reflecting the light of the S polarization component. For this reason, the reflected light of the S-polarized component that has entered the polarization beam splitter 24 is reflected by the polarization beam splitter 24 and is applied to the photodetector 29 via the focusing lens 27 and the collimator lens 28.

The photodetector 29 is shown in FIG.
As shown in (1), the first photodetector 45 receives the reflected light of the zero-order light and the second and third photodetectors 46 and 47 receive the reflected light of the ± first-order lights.

The light receiving region of the first photodetector 45 is radially divided into four equal parts (light receiving region A to light receiving region D) about the optical axis. Further, each of the second and third photodetectors 46 and 47 has only one light receiving region (light receiving region E and light receiving region F).

Each of the photodetectors 45 to 47 forms a light amount detection signal corresponding to the light amount of the reflected light received in each light receiving region, and these are detected as a tracking error detection unit 30, a focus error detection unit 31, and an RF signal detection unit. Supply to 32.

The tracking error detector 30 outputs light amount detection signals from the light receiving areas E and F of the second and third photodetectors 46 and 47, respectively, to "E" and "F".
As a result, the tracking error signal is detected based on the following arithmetic expression.

Tracking error signal = EF In this way, the tracking error signal detected by the tracking error detector 30 is the current / voltage conversion circuit (I / F).
V conversion circuit) 33. The I / V conversion circuit 3
3 converts the tracking error signal supplied in the form of a current into a voltage, and converts this into a tracking driver 3
Supply to 9. The tracking driver 39 uses the tracking coil 4 according to the tracking error signal.
Drive 0.

As a result, the objective lens 26 can be driven in the direction for correcting the tracking error, and the recorded data can be always reproduced in the just track state.

Next, the focus error detector 31
Is configured to detect a focus error by, for example, a so-called astigmatism method, and the light amount detection signals from the respective light receiving areas A to D of the first photodetector 45 are respectively set to “A to D”, and the following arithmetic expression is used. The focus error signal is detected based on

Focus error signal = (A + D) − (B + C) The focus error signal thus detected by the focus error detection unit 31 is converted into a voltage by the I / V conversion circuit 34, and the focus control unit 36 described later is described. Is supplied to the focus driver 41 via the. The focus driver 41 drives the focus coil 42 according to the focus error signal.

As a result, the objective lens 26 can be driven in the direction in which the focus error is corrected, and the recorded data can be always reproduced in the just-focused state.

Next, the RF signal detector 32 sets the light amount detection signals from the respective light receiving regions A to D of the first photodetector 45 as "A to D", and outputs the RF signal based on the following arithmetic expression. To detect.

RF signal = A + B + C + D The RF signal thus detected by the RF signal detector 32 is converted into a voltage by the I / V conversion circuit 35 and supplied to the recording data detector 37. Recording data detection unit 3
Reference numeral 7 detects, based on the RF signal, only the recording data from which, for example, the reproduction signal of the servo pattern has been removed, and supplies this to an external device such as a computer device or a speaker device via an output terminal 38.

As a result, it is possible to record the record data reproduced from the multi-layer optical disc 20 on another recording medium, obtain an acoustic output corresponding to the record data, and the like.

Here, the multilayer optical disc 20 is shown in FIG.
As shown in FIG. 1, between the transparent substrate 60 having a thickness of 1.16 to 1.2 mm formed of a transparent member such as polycarbonate and the aluminum reflective layer 65 formed of aluminum, for example, the first to fourth recordings are performed. It is configured by stacking layers 61 to 64. The first to fourth recording layers 61 to 64 have light transmittances decreasing in order, respectively, and are arranged between the first and second recording layers 61 and 62, the second and third recording layers 62, Spacers 66 to 68 made of transparent resin are provided between 63 and between the third and fourth recording layers 63 and 64, respectively.

If the thickness of each of the spacers 66 to 68 is large, the image forming characteristics are adversely affected. Therefore, the thickness of each of the spacers 66 to 68 needs to be within a range that can be compensated by the image forming characteristics of the objective lens, and in the case of the present embodiment, the thickness is, for example, 35 to 40 μm. Recording data is recorded in pits on each of the recording layers 61 to 64.

When reproducing recorded data from such a multi-layer optical disc 20, first, it is necessary to focus on a desired recording layer prior to reproduction. For this reason,
The user specifies the recording layer to be reproduced by the recording layer specifying unit 5.

When the user designates a desired recording layer, the system controller 11 stores the recording layer designation data in the memory 6a and enters the focus search mode to focus on the designated recording layer.

Specifically, the system controller 1 described above
When the focus search mode 1 is set to the focus search mode, the focus coil 42 is supplied with a triangular wave signal of, for example, about 2 Hz to drive the objective lens 26, the focus error signal obtained thereby is detected, and the focus error signal is set to a predetermined value. Compare with reference signal. As mentioned above,
Since the multilayer optical disc 20 has four recording layers, four comparison pulses corresponding to the recording layers can be obtained by comparing the focus error signal with a predetermined reference signal. The system controller 11 is
The number of pulses is counted, and after the comparison pulse of the recording layer designated by the user is detected, the focus servo is pulled in at the timing when the focus error signal first becomes zero level.

As a result, the focus servo can be applied to the designated recording layer, and the recording data recorded in the designated recording layer can be reproduced.

Next, since the multi-layered optical disc 20 has four recording layers, if the disc reproducing apparatus is vibrated or scratches or dust adheres to the disc, the disc is currently being reproduced. This causes a problem that the recording layer other than the recording layer is in focus, which hinders accurate reproduction of the recorded data.

Therefore, in the disc reproducing apparatus, the focus control section 36 detects the out-of-focus state during the reproduction.

That is, the focus error signal detected by the focus error detector 31 during reproduction is input to the non-inverted input of the first comparator 9 in the out-of-focus detection circuit 3 via the input terminal 1 shown in FIG. Terminal and second
Are respectively supplied to the inverting input terminals of the comparator 11.

At the inverting input terminal of the first comparator 9 and the non-inverting input terminal of the second comparator 11, the first reference voltage of a predetermined level from the first reference voltage generating circuit 10 and Second reference voltages of a predetermined level are respectively supplied from the second reference voltage generating circuit 12.

The first reference voltage is set to a positive level capable of detecting a focus error signal when defocus occurs, and the second reference voltage causes defocus. If the focus error signal is set to a negative level that can be detected.

The first comparator 9 compares the first reference voltage with the positive level focus error signal and supplies the first comparison pulse to the system controller 6. Further, the second comparator 11 compares the second reference voltage with a focus error signal of negative level and supplies the second comparison pulse to the system controller 6.

When the defocus occurs, the first
And the second comparator 9, 10 should provide the first and second comparison pulses.

Therefore, the system controller 6 is
Operates to detect out-of-focus by detecting the first and second comparison pulses and to refocus on the original recording layer based on the flowchart shown in FIG.

That is, this flowchart starts when the reproduction of the recorded data recorded on the multilayer optical disc 20 is started, and the process proceeds to step S1.

In step S1, the system controller 6 detects the presence or absence of the first and second comparison pulses supplied from the first and second comparators 9 and 11 to detect the presence or absence of defocus. If it is detected that there is no out-of-focus, this step S1 is repeated, and if out-of-focus is detected, the process proceeds to step S2.

Until out-of-focus is detected, the system controller 6 controls the changeover switch 8 so as to select the selected terminal 8a by the selection terminal 8c, and outputs the focus error signal obtained during reproduction as described above. Although it is supplied to the focus driver 41, when the out-of-focus state is detected, in step S2,
The changeover switch 8 is switched and controlled so as to select the selected terminal 8b by the selection terminal 8c, and the related parts are controlled so as to stop the output of the reproduced record data, and the process proceeds to step S3.

In step S3, the system controller 6 reads out the recording layer designation data stored in the memory 6a and, based on the reproduction data of the recording layer reproduced after the out-of-focus state, defocuss the same. The reproduced recording layer is detected by. And
The recording layer designation data is compared with the data indicating the recording layer reproduced by the defocus, and the process proceeds to step S4.

In step S4, the system controller 6 skips a number of layers to perform focus adjustment (focus jump) in order to refocus on the recording layer that was reproduced before the defocus, based on the comparison result. The recovery data indicating whether to perform is performed and the process proceeds to step S5.

In step S5, the system controller 6 performs a focus jump based on the restoration data, refocuses the recording layer that was being reproduced before the defocus, and proceeds to step S6.

Specifically, for example, if the recording layer that was being reproduced before the defocus is the third recording layer 63 and the defocus causes the second recording layer 63 to be in focus, the system controller is used. 6 is shown in FIG.
(E) The changeover switch 8 is controlled so as to select the selected terminal 8b by the selection terminal 8c by the low level pulse shown at time t1 to time t7.
The acceleration / deceleration pulse generation circuit 7 is controlled so as to generate a high-level acceleration pulse from time t1 to time t3 in FIG. The acceleration pulse is supplied to the focus coil 42 via the changeover switch 8. As a result, the objective lens 26 is moved in the disc direction, and a focus error signal as shown in FIG. 5C is generated.

The out-of-focus detection circuit 3 shown in FIG.
As shown in (c), the focus error signal is compared with the first and second reference voltages. As a result, while the focus error signal is at a level equal to or higher than the first reference voltage, a high level comparison pulse as shown at time t2 to time t3 in FIG. 5A is supplied to the system controller 6. It will be.

The system controller 6 is shown in FIG.
The falling edge of the comparison pulse shown at time t3 in (a) is detected, and at this timing, the acceleration / deceleration pulse generation circuit is arranged to stop the output of the acceleration pulse as shown at time t3 in FIG. Control 7

By supplying the acceleration pulse to the focus coil 42, as can be seen from the focus error signal shown at time t2 to time t3 in FIG. 5C, the focus that matches the second recording layer 62 is obtained. However, once it comes off, it starts to fit on the third recording layer 63, and the level of the focus error signal gradually becomes zero level as shown between time t3 and time t4 in FIG. Since the lens 26 moves a little due to inertia or the like even after the supply of the acceleration pulse is stopped, this time the focus is the third position.
Then, the focal point of the recording layer 63 is exceeded and a negative focus error signal is generated.

The out-of-focus detection circuit 3 shown in FIG.
As shown in time t4 to time t5 in (c), when the level of the negative focus error signal becomes equal to or lower than the level of the second reference voltage, as shown in time t4 to time t5 in FIG. A comparison pulse is formed and supplied to the system controller 6.

The system controller 6 is shown in FIG.
The acceleration / deceleration pulse generation circuit detects the rising edge of the comparison pulse at time t4 in (b) and outputs a deceleration pulse as shown at time t4 to time t6 in FIG. Control 7

The output time of this deceleration pulse is the time required to restore the focus once out of focus at the time of this focus jump, and it is determined in advance by experiments or the like.

As a result, the objective lens 26 is moved in the direction opposite to the disc direction, and the focus once deviated from the third recording layer 63 is refocused on the third recording layer 63.
Then, the system controller 6 stops the output of the deceleration pulse at time t6 shown in FIG. 5D, and then supplies a high level pulse to the changeover switch 8 at time t7 shown in FIG. 5E. Then, the selected terminal 8a is selected and controlled to end the focus jump.

In this example, the focus jump of one layer is performed. However, when the focus jump of two or more layers is performed, the focus jump operation described above is repeatedly performed.

Upon completion of such a focus jump, the system controller 6 proceeds to step S6. The memory 6a also stores, for example, address data of the recording layer that was reproduced before the defocus. Therefore, the system controller 6 determines, in step S6, based on the address data.
The recording track that was being reproduced before the out of focus is detected, and the tracking driver 39 and the like shown in FIG. 2 are controlled so as to perform the track jump to this recording track, and the process proceeds to step S7.

In step S7, the system controller 6 determines whether or not the focus jump and the track jump have been completed on the recording layer before defocus and the recording track of the recording layer. If NO, the above-mentioned step is executed. Control each part to repeat the focus jump and the track jump of S5 and step S6,
If YES, the process proceeds to step S8.

In step S8, the system controller 6 controls each part so as to restart the output of the reproduced record data, and terminates all the routines shown in this flowchart.

As described above, the focus control apparatus according to this embodiment can detect the out-of-focus state during reproduction and restore it. For this reason, it is possible to prevent the inconvenience of unintentionally reproducing the record data of the recording layer due to the defocus, and it is possible to accurately reproduce the record data.

In the above description of the embodiments, the focus control device according to the present invention is applied to the optical disc reproducing device, but this may be applied to, for example, an optical disc recording device or an optical disc recording / reproducing device. .

Further, the recording layer designating data indicating the recording layer designated by the operation of the recording layer designating unit 5 is stored in the memory 6a, and when out of focus occurs, this memory 6a is stored.
The recording layer designation data is read out from the recording layer to detect the recording layer that was being reproduced before the out-of-focus state. For each recording layer of the multilayer optical disc 20, the recording layer indicating the recording layer is recorded. Record layer data,
The recording layer data obtained at the time of reproduction may be stored in the memory 6a to detect the recording layer that was being reproduced before being out of focus.

Further, although the optical disc 20 is an optical disc in which recording data is previously formed in a pit shape, it may be other optical disc such as a magneto-optical disc as long as it has a multi-layer structure. is there.

[0072]

The focus control device according to the present invention can detect the out-of-focus state where the recording layer being recorded or reproduced is focused on another recording layer.

Further, it is possible to detect the defocus and refocus the original recording layer.

[Brief description of drawings]

FIG. 1 is a block diagram of a focus control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an optical pickup device provided with the focus control device according to the embodiment.

FIG. 3 is a schematic diagram of a photodetector provided in the optical pickup device.

FIG. 4 is a flowchart for explaining the operation of the focus control apparatus according to the above embodiment.

FIG. 5 is a time chart for explaining a refocusing operation of the focus control device according to the embodiment.

FIG. 6 is a schematic diagram for explaining the structure of a multilayer optical disc.

FIG. 7 is a diagram for explaining how a focus moves with respect to each recording layer of a multilayer optical disc.

[Explanation of symbols]

 1 Focus Error Signal Input Terminal 3 Out of Focus Detection Circuit 5 Recording Layer Designating Section 6 System Controller 6a Memory 7 Acceleration / Deceleration Pulse Generation Circuit 8 Changeover Switch 9 First Comparator 11 Second Comparator 10 First Reference Voltage Generation Circuit 12 Second reference voltage generating circuit 20 Multi-layer optical disc 61-64 First to fourth recording layers

Claims (2)

[Claims] 1. A focus control device for performing focus control on a multi-layer optical disc having a plurality of recording layers laminated, wherein a focus error signal and a reference signal of a predetermined level supplied from the outside by the recording or reproducing. The focus control device has an out-of-focus detection unit that detects out-of-focus state in which another recording layer is focused during recording or reproduction by performing level comparison. 2. A recording layer detecting means for detecting a recording layer currently being recorded or reproduced, and original recording layer information indicating the recording layer currently being recorded or reproduced detected by the recording layer detecting means. When the out-of-focus is detected by the storage means and the out-of-focus detection means, the original recording layer information is read from the storage means, and the out-of-focus information is read from the data of the recording layer recorded or reproduced by the out-of-focus. The recording layer that is being recorded or reproduced is detected by, and the focus control is performed based on the detection data and the original recording layer information so as to refocus the recording layer that was being recorded or reproduced before the defocus occurs. The focus control device according to claim 1, further comprising: