JPH10124883A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control acceleration voltage properly stably against wobbling and noise at the time of layer jump by eliminating high-frequency components such as noise of a driving signal and detecting zero-crossing point of a focussing error signal with histeresis. SOLUTION: A driving signal for a pickup 3 from a focus control circuit 8 is inputted in LPF 14 through a changeover switch 19b. Then, high frequency components such as noise are eliminated but low frequency such as wobbling are not, with the signal supplied to an adder 17. In the movement to other focussing point on a recording surface, a micro computer 13 switches the changeover switch 19a, 19b to the jump side, setting the rising/falling voltage of a specific value in a circuit 15, 16 for setting such voltage value. After that, it is switched to the rising voltage side and supplied to the pickup 3. Then, a focus zero crossing detector 12 detects the zero crossing point of a focussing error signal with histeresis, switching it to the falling voltage side by the micro computer 13. Consequently, the focusing point is surely moved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for optically reproducing / recording / reproducing a signal from a disk, and more particularly to reproducing / recording / reproducing a disk having two or more recording surfaces on one side. The present invention relates to an optical disk device that can perform the operation.

[0002]

2. Description of the Related Art Currently, standardized digital video discs (hereinafter referred to as DVDs) include a single-sided single layer,
There are single-sided, double-sided, and double-sided discs. Conventional discs, for example, a compact disc (hereinafter referred to as a CD) and a laser disc (hereinafter referred to as L
D) has only one recording surface on one side, but in order to increase the recording capacity of a DVD, a two-layer disk having two recording surfaces on one side (hereinafter simply referred to as a two-layer disk) is used. Exists.

FIGS. 2A and 2B are views showing such a two-layer disc. FIG. 2A shows a 0.6 mm 2
A single-sided two-layer disc in which a recording surface is made on each of the discs, and a disc with a high-reflectance film made of aluminum and a disc with a reflective film made of translucent gold are stuck together with high accuracy. Is shown. FIG. 2B shows that a 0.6 mm disk is
This figure shows a double-sided double-layer disc in which information is laminated with high precision and information is multiplexed in the depth direction of the laminated discs.

In the case of this double-layer disc, information is recorded on the recording surface of each layer, and as shown in FIG. 2D, the drive signal of the pickup is gradually increased (in this case, the drive of the pickup is performed). When the signal is increased, the objective lens also increases in the direction approaching the disk), and in the focus error signal shown in FIG. 2C, the lower layer (hereinafter referred to as the 0th layer) is in focus. A point (hereinafter, referred to as a focal point) appears at a certain pickup position, and when the pickup is further raised, the focal point of an upper layer (hereinafter, referred to as a first layer) is shifted to a position of the 0th layer pickup. Appears even further up. In short, in the case of a two-layer disc, the focus of each layer is adjusted by raising and lowering the position of the pickup.

[0005] In the case of a CD or LD, it is necessary to focus on only one recording surface.
In the case of a two-layer disc having two surfaces on which information is recorded on one side, if the focal point is not moved from the recording surface of the layer that is already in focus to the recording surface of another layer, the recording of another layer is performed. Information cannot be read. In general, the focal point movement between layers (hereinafter, referred to as a layer jump) is performed by slightly shifting the position of the pickup by applying a rising voltage or a falling voltage to the pickup driving voltage. Such a conventional technique is described, for example, on page 66 of "A Book Understands All About DVD" (Nihon Jitsugyo Shuppansha, written by Yojiro Igawa).

[0006]

In the above-mentioned prior art, when a layer jump is performed from another state where the focus is already in focus to another layer, the pickup voltage is increased by applying a rising voltage or a falling voltage to the pickup driving voltage. , But how to apply these voltages is not specified.

By the way, in order to perform a layer jump, the pickup is moved to another layer from a state where the focus is already in focus. At this time, the following problem occurs. (1) A rising voltage or a falling voltage is applied to the pickup driving voltage. If the value of the applied voltage is large, the pickup moves more than expected and far exceeds the focal point of another layer. If it is too small, it will not reach the focal point of other layers. (2) The drive voltage of the pickup is swung up and down in synchronism with the wobble of the disk in order to always focus on the focal point. (3) Since the pickup drive voltage also has many noise components, the influence of noise is greatly affected when a rising voltage or a falling voltage is applied.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to always provide a proper rise in a surface jump and noise when performing a layer jump. Voltage and falling voltage can be applied,
It is an object of the present invention to provide an optical disk device capable of controlling a rising voltage or a falling voltage necessary for moving to another layer by appropriately detecting a switching point of a layer and performing a layer jump stably.

[0009]

According to the present invention, there is provided an optical disk apparatus for optically reproducing or recording / reproducing a disk having two or more layers having a recording surface on one side. An objective lens for focusing the laser beam on the recording surface of the optical disk, moving means for moving the objective lens in a direction substantially perpendicular to the disk surface, and focusing the objective lens on the recording surface of the disk, and an objective lens Means for generating a focus error signal from a signal obtained from the microcomputer, focus control means for generating a pickup drive signal (focus drive signal) for focusing the objective lens from the focus error signal, and a noise component of the focus drive signal A low-pass filter that removes, and a means for adding a constant voltage for finely moving the objective lens, Means for controlling voltage switching for raising or lowering the pickup, and means for detecting a switching point of a layer on the recording surface from a focus error signal, and When moving to the focal point of the layer, a rising voltage or a falling voltage is added to the pickup drive signal from which the noise component has been removed, and the rising voltage and the falling voltage are switched at the switching point of the layer on the recording surface. . As a result, the layer jump can be stably performed without being affected by surface runout or noise.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an optical disk device according to one embodiment of the present invention. FIG.
Wherein 1 is a disc having two or more recording surfaces on one side,
2a is a clamper, 2b is a turntable, 3 is a pickup, 4 is a lead screw, 5 is a thread motor, 6
Is a spindle motor, 7 is a signal processing circuit, 8 is a focus control circuit, 9 is a tracking control circuit, 10 is a thread control circuit, 11 is a spindle control circuit, 12 is a focus zero cross detector, and 13 is a microcomputer (hereinafter referred to as a microcomputer). , 14 is a low-pass filter (hereinafter referred to as LPF), 15 is a rising voltage value setting circuit,
16 is a falling voltage value setting circuit, 17 is an adder, 18 is a voltage changeover switch, 19a is a changeover switch, 19b
Is a changeover switch, and 26 is a previous value holding circuit.

Next, the operation of this embodiment will be described. The disc 1 set on the turntable 2b is fixed to the turntable 2b by a clamper 2a, and the disc 1 rotates as the spindle motor 6 rotates.

The microcomputer 13 supplies a light emission control signal to the semiconductor laser in the pickup 3 in order to read information from the disk 1.

FIG. 3 shows a configuration example of the semiconductor laser and the optical system of the pickup 3 and a configuration example of the focus error signal detecting means of the signal processing circuit 7.

In FIG. 3, reference numeral 20 denotes an objective lens, 21 denotes a half prism, 22 denotes a semiconductor laser, 23 denotes a condenser lens, 24 denotes a photodetector, and 25 denotes an error calculator (error amplifier).

The light beam emitted by the semiconductor laser 22 passes through the half prism 21 and is focused by the objective lens 20 to form a beam spot on the disk 1. The laser reflected light from the disk 1 passes through the objective lens 20 again, is reflected by the half prism 21, and is condensed by the condenser lens 23.
To connect a spot to the photodetector 24.

A specific configuration example for detecting a focus error signal in the photodetector 24 will be described.
As shown in FIG. 3, the photodetector 24 has four areas A,
B, C, and D, which are electrically connected in pairs on a diagonal line.

When the disk 1 and the objective lens 20 are at the focal position, if the position of the photodetector 24 is set such that the beam spot incident on the photodetector 24 becomes a circle, the position of the photodetector 24 on the diagonal line is reduced. The output obtained by amplifying the added output by the error amplifier 25 becomes zero. Here, when the disc 1 is shifted up and down with respect to the focal position of the objective lens 20, the light detector 2
Using the fact that the beam spot incident on the beam spot 4 becomes vertically long or horizontally long, the error amplifier 25 detects a focus error signal as shown in FIG. (So-called astigmatism method).

In FIG. 4, the horizontal axis represents the distance between the objective lens and the disk, and the vertical axis represents the signal level. The S-curve of the focus error signal has a characteristic of zero crossing at the point where the objective lens is focused on the disk recording surface. Note that the polarity of the S-shaped curve may be reversed depending on the difference in the input to the error calculator 25, but in such a system, the concepts of the signal level and the disk displacement may be reversed. Needless to say.

The focus error signal generated by the error calculator 25 is supplied to a focus control circuit 8, where the focus control circuit 8 performs feedback control for the feedback control near the zero cross point in the S-shaped curve of the focus error signal. A drive signal for the pickup 3 is generated and output. This output signal is supplied to the changeover switch 19a. The changeover switch 19a is switched to a steady state at a steady state in accordance with a command from the microcomputer 13, and is supplied as a drive signal for the pickup 3. The pickup 3 is controlled in a vertical direction by the drive signal of the pickup 3 to realize focus control of a feedback loop, and always keeps a state of being in focus.

On the other hand, the tracking error signal generated by the signal processing circuit 8 is supplied to a tracking control circuit 9,
The tracking control circuit 9 generates a drive signal for feedback control of the pickup 3 in the tracking direction. The drive signal of the pickup 3 is supplied to the inside of the pickup 3, whereby the pickup 3
Is finely controlled in the tracking direction, realizes tracking control of a feedback loop, and always keeps on a pit on the recording surface of the disk 1.

The drive signal output from the tracking control circuit 9 is also supplied to a thread control circuit 10,
The sled control circuit 10 generates a drive signal for controlling the sled motor 6 in accordance with the deviation of the pickup 3 in the tracking direction, supplies the drive signal to the sled motor 6, and moves the sled motor 6.

The signal processing circuit 7 supplies rotation cycle information read from the disk 1 to the spindle control circuit 11, and generates a signal for driving the spindle motor 6 in the spindle control circuit 11 based on the rotation cycle information. To the spindle motor 6.

The above is a state in which the focus, the tracking, the spindle, and the sled are controlled at the focal point in the steady state.

Here, the disk 1 has the DV
In the case of the single-sided dual-layer disc D, it may be necessary to switch the focus position from the layer on the current recording surface to the layer on another recording surface. For example, if the position of the pickup 3 is on the focal point of the recording layer of the 0th layer, and it is desired to bring the focal point to the recording surface of the 1st layer from this state, in other words, the lower layer (0
A case where the focal point is jumped from the layer) to the upper layer (one layer) will be described.

First, the drive signal of the pickup 3 output from the focus control circuit 8 in the state where the focus is on the recording surface of the zeroth layer in the steady state is changed over by the changeover switch 19b.
In the steady state, the changeover switch 19b is switched to the steady side, and the drive signal of the pickup 3 output by the focus control circuit 8 is supplied to the previous value holding circuit 26 as it is. The previous value holding circuit 26 always holds the value until the value changes, and supplies the held value to the LPF 14.

The LPF 14 has a frequency characteristic that removes the high-frequency component (noise component) of the signal for driving the pickup 3 but does not remove the low-frequency component such as the surface shake described later. Remove the component and adder 17
To supply. In the normal state, the operation up to the LPF 14 described above is always performed.

Here, when moving to the focal point on the recording surface of one layer, the microcomputer 13 switches the changeover switches 19a and 19b to the jump side. As a result, the changeover switch 19b is opened, so that the feedback loop that has been controlling the pickup 3 becomes an open loop and the control is disconnected. In addition, the microcomputer 13 sets constant rising voltage values and falling voltage values in the rising voltage value setting circuit 15 and the falling voltage value setting circuit 16 in order to raise the recording surface to one layer. Furthermore, the microcomputer 13 issues an instruction to switch the voltage changeover switch 18 to the increased voltage value side.

The output from the rising voltage value setting circuit 15 is supplied to an adder 17. Then, the signal from which the high-frequency noise component has been removed by the LPF 14 and the increased voltage value are added by the adder 17 and output, and supplied to the changeover switch 19a. The addition signal supplied to the changeover switch 19a is supplied to the pickup 3 through the changeover switch 19a because the changeover switch 19a is switched to the jump side.

As a result, the pickup 3 starts rising by the drive voltage to which the rising voltage value has been added. Here, the focus error signal output from the signal processing circuit 7 is supplied to the focus zero cross detector 12, which detects a point where the focus error signal crosses zero (center) and supplies it to the microcomputer 13. I do. When detecting the zero crossing point, the microcomputer 13 sets the falling voltage value in the falling voltage value setting circuit 16 and issues an instruction to switch the voltage switch 18 to the falling voltage value side. At this time, the microcomputer 13
Then, the time (time A) during which the rising voltage value is applied is measured.

The output from the falling voltage value setting circuit 16 is supplied to an adder 17. Then, the adder 17 adds the signal from which the high-frequency component has been removed by the LPF 14 and the falling voltage value, and outputs the result. At this time, since the layer jump is being performed, the changeover switches 19a and 19b remain switched to the jump side. The addition signal supplied to the changeover switch 19a is
Is supplied to the pickup 3 through the
This time, the pickup 3 is lowered. This falling voltage value is applied by applying a reverse voltage to the pickup 3 which has been rising so far to apply a brake, and the pickup 3
Work to stop the rise. After applying the falling voltage value for a certain period of time (time A × K; K is a constant) which is a multiple of the application time of the rising voltage value, the microcomputer 13 switches the changeover switch 19a to focus on the recording surface of one layer. , 19b
Is switched to the steady side.

As a result, the control of the pickup 3 which has been in the open loop is controlled by the feedback loop using the focus error signal again, and the feedback control is performed so as to be drawn to the focal point of the recording layer of one layer. .

By the above-described operation, the state of being at the focal point of the recording layer of layer 0 is changed to the state of being at the focal point of layer 1.

The state of the above-described layer jump operation will be described with reference to FIG. FIGS. 5A and 5B show a focus error signal at the time of ascending and descending, a driving signal of the pickup 3, and a switching polarity of the changeover switches 19a and 19b. The axis is the voltage value. In this case, it is assumed that the pickup 3 rises when the pickup driving voltage value is increased, and falls when the pickup voltage value is decreased.

FIG. 5A shows that the position of the focal point is changed from 0 layer to 1 layer.
When the focus error signal is in the focused state on the recording surface of the lower layer (layer 0) in the case where the focus error signal is raised to the layer, the focus error signal is almost zero. At this time, the pickup drive signal is also controlled by the feedback loop, and becomes constant at a certain voltage value.

Here, the changeover switches 19a, 19b
Is changed from the steady side to the jump side, the control of the feedback loop is cut off, and at the same time, a constant rising voltage is applied.
Then, since the pickup 3 starts to rise, the focal point in the 0 layer goes out of focus, and the focus error signal goes down the valley. As you continue to climb, you will cross this valley. As the rising voltage continues to be applied, the focus error signal goes up the valley and a zero cross point appears. At this zero cross point, the rising voltage is switched to the falling voltage. Further, the microcomputer 13 measures the time (time A) during which the rising voltage is applied.

With the application of a constant falling voltage, the acceleration of the pickup 3 caused by the rising voltage changes from the rising direction to the falling direction. However, the pickup 3 keeps rising for a while, stops and starts to fall. After a multiple of the time during which the rising voltage is applied (time A × K; K is a constant), the application of the falling voltage is stopped, and the changeover switches 19a, 1
9b is switched to the stationary side. At this point, since the pickup 3 is near the focal point of the first layer, the focus control of the feedback loop based on the focus error signal is performed, and the pickup 3 is drawn to the focal point of the recording surface of the first layer.

Similarly, FIG. 5B shows that the position of the focal point is 1 point.
In the case of lowering from the layer to the zero layer, when the focus is on the recording surface of the upper layer (one layer), the focus error signal is almost zero. At this time, the pickup drive signal is also controlled by the feedback loop, and becomes constant at a certain voltage value.

Here, the changeover switches 19a, 19b
Is changed from the steady side to the jump side, the control of the feedback loop is cut off, and at the same time, a constant falling voltage is applied.
Then, since the pickup 3 starts descending, the focal point in one layer goes out and the focus error signal goes up the mountain. As you continue descending, you will cross this mountain. When the falling voltage is further applied, the focus error signal goes down the mountain and a zero cross point appears. At this zero cross point, the falling voltage is switched to the rising voltage. Further, the microcomputer 13 measures the time (time A) during which the falling voltage is applied.

By the application of a constant rising voltage, the acceleration of the pickup 3 caused by the falling voltage changes from the falling direction to the rising direction, but for a while the pickup 3 keeps falling, stops and starts rising. After a multiple of the time during which the falling voltage is applied (time A × K; K is a constant), the application of the rising voltage is stopped and the changeover switches 19a, 1
9b is switched to the stationary side. At this point, since the pickup 3 is near the focal point of the 0th layer, the focus control of the feedback loop based on the focus error signal is performed, and the pickup 3 is drawn to the focal point of the recording surface of the 0th layer.

As described above, the appearance of the peaks and valleys of the focus error signal may be completely reversed depending on the polarity of the error calculator 25 as described above. In that case, the appearance is reversed. Needless to say, it can be considered as.

In this embodiment, as described above, a rising voltage value or a falling voltage value is applied to the output signal from the focus control circuit 8. This is to prevent the influence of surface runout. The disk 1 has a phenomenon called surface runout, which is caused when the disk 1 is not completely flat but has a warp or curve, or the disk surface of the loaded disk is affected by the mechanical accuracy of the turntable 2b. This occurs when the axis is not perpendicular to the rotation axis of the spindle motor 6.

In the focused state, the control is always performed so that the distance from the position of the objective lens of the pickup 3 to the recording surface of the disc is constant. Appears to wave along the surface runout. That is, the position of the pickup 3 also undulates. Since the distance from the in-focus state of the current layer to the in-focus point of another layer is constant, when a layer jump is performed, applying a rising voltage value or a falling voltage value to the focus error signal at the time of focusing, A certain amount of rise and fall can be made from the focal point.

This is shown in FIGS. 6A and 6B. The horizontal axis represents time, and the vertical axis represents the voltage value of the focus error signal. As shown in FIG. 6 (a), when in the valley component of surface runout, a rising voltage value or a falling voltage value is applied from that position,
As shown in FIG. 6 (b), when you are in the component of the runout mountain,
A rising voltage or a falling voltage is applied from that position. As a result, a stable layer jump can be realized without being affected by the runout of the disk 1.

In the present embodiment, as described above, the drive signal of the pickup 3 generated from the focus error signal by the focus control circuit 8 is replaced by the LPF 14 from which high frequency components (noise components) have been removed. The rising voltage and the falling voltage are added, and the effect of passing through the LPF 14 will be described.

FIGS. 7A and 7B show the case where a rising voltage is applied to the output signal from the focus control circuit 8 which does not pass through the LPF 14. FIG. In the state where noise is added to the center voltage value of the output signal, a voltage is applied to this noise component in FIG. 7A, but when a voltage is applied to the valley of the noise component, the voltage is applied. In practice, a value lower than the voltage value is applied, and the pickup 3 cannot be sufficiently raised. On the other hand, when a voltage is applied to the peak of the noise component as shown in FIG.
In practice, a value higher than the applied voltage value is applied, so that the pickup 3 is lifted more than necessary, and an acceleration is applied that exceeds the focal point of the next layer. That is, the applied voltage value is not constant due to the influence of noise.

Therefore, LP for removing high-frequency noise components
By passing through F14, as shown in FIG. 7 (c), a rising voltage can always be applied to the center voltage value, so that the acceleration due to the voltage application to the pickup 3 can be made constant and stable. Layer jump can be realized. However,
The LPF 14 has a frequency characteristic that does not remove the low-frequency surface vibration component, and does not remove the high-frequency noise component but does not remove the low-frequency surface vibration component.

Further, in this embodiment, the focus zero-cross detector 12 detects a point crossing zero (center) of the focus error signal, and detects the position of the center with hysteresis. That is, the position shifted from the center is set as the zero cross point. This is shown in FIG.
As shown in (a), since there is a flat portion between the focus error signal on the 0th layer and the appearance of the focus error signal on the 1st layer and the influence of noise, the layer changes at the focus zero crossing point. Is difficult to detect, and the lower or higher than the original zero-cross point is set as the zero-cross point with hysteresis, so that it can be reliably detected that the layer has moved to another layer.

FIG. 8 shows a state of the layer jump when the focus zero cross detector 12 has hysteresis in the schematic diagram of the layer jump shown in FIG.
FIGS. 8A and 8B show a focus error signal when ascending and descending, a pickup drive signal, and a switching polarity of the changeover switches 19a and 19b. The horizontal axis represents time, and the vertical axis represents time. It is a voltage value. The dotted line indicates the amount of hysteresis of the focus zero cross detector 12.

FIG. 8A shows a case where the focus position is raised, and the pickup 3 is raised by applying the rising voltage as described above. If you continue to apply a rising voltage,
The focus error signal goes up the valley and a zero-cross point appears.
With the hysteresis of 2, a zero cross point is detected above the center position. At the zero cross point having this hysteresis, the rising voltage is switched to the falling voltage. And
The focus control of the feedback loop is performed by the focus error signal near the focal point of the recording surface of the first layer.
It is drawn to the focal point of the recording surface of the layer.

FIG. 8B shows the case where the focus position is lowered, and the pickup 3 is lowered by applying the falling voltage as described above. If you continue to apply the falling voltage,
The focus error signal goes down the mountain and a zero-cross point appears.
With the hysteresis of 2, the zero cross point is detected below the center position. At the zero cross point having the hysteresis, the falling voltage is switched to the rising voltage. And
The focus control of the feedback loop is performed by the focus error signal near the focal point of the recording surface of the 0th layer,
It is drawn to the focal point of the recording surface of the layer.

By detecting the zero-cross point with the hysteresis of the focus zero-cross detector 12 as described above, it is possible to detect that the layer to be jumped to the layer to be surely jumped without being affected by the noise. It is possible to switch from a voltage or a falling voltage to a rising voltage.

Each control at the time of the layer jump is performed by the microcomputer 13, and the control algorithm P at that time is used.
The AD diagram is shown in FIG. With this algorithm, the microcomputer 13 can control the layer jump stably.

As described above, according to the present embodiment, when performing a layer jump, it is possible to always apply an appropriate acceleration voltage with respect to surface runout and noise. By properly detecting layer transition points,
By controlling a rising voltage or a falling voltage necessary for moving to another layer, it is possible to realize an optical disk device capable of performing a layer jump stably.

[0054]

According to the present invention, the following effects can be obtained. (1) When performing a layer jump, it is possible to always apply an appropriate acceleration voltage with respect to surface runout and noise, and a layer jump can be stably performed. (2) It is possible to detect a switching point of a layer and control an acceleration voltage necessary for moving to another layer.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical disc device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an outline of a two-layer disc and a layer jump.

FIG. 3 is an explanatory diagram illustrating a configuration example of a semiconductor laser and an optical system of a pickup, and a configuration example of a focus error signal detection unit of a signal processing circuit.

FIG. 4 is an explanatory diagram showing a focus error signal with respect to a disk displacement.

FIG. 5 is an explanatory diagram showing a focus error signal and a pickup drive signal at the time of a layer jump.

FIG. 6 is an explanatory diagram showing a surface runout component and an applied voltage.

FIG. 7 is an explanatory diagram showing noise components and applied voltages.

FIG. 8 is an explanatory diagram showing a focus error signal and a pickup drive signal in a layer jump when detecting a zero cross having hysteresis.

FIG. 9 is an explanatory diagram showing an example of a layer jump control algorithm in the microcomputer.

[Explanation of symbols]

 Reference Signs List 1 disc having two or more recording surfaces on one side 2a clamper 2b turntable 3 pickup 4 lead screw 5 thread motor 6 spindle motor 7 signal processing circuit 8 focus control circuit 9 tracking control circuit 10 thread control circuit 11 spindle control circuit 12 focus zero cross Detector 13 Microcomputer (microcomputer) 14 Low-pass filter (LPF) 15 Rising voltage value setting circuit 16 Falling voltage value setting circuit 17 Adder 18 Voltage switch 19a Switch 19b Switch 20 Objective lens 21 Half prism 22 Semiconductor laser 23 Condenser lens 24 Photodetector 25 Error calculator 26 Previous value holding circuit

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Jiro Higashi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Within the Visual Information Media Division, Hitachi, Ltd. Gochome No. 20, No. 1 Semiconductor Division, Hitachi, Ltd.

Claims (3)

[Claims] An optical disk apparatus for optically reproducing or recording / reproducing a disk having two or more layers having a recording surface on one surface, comprising: an objective lens for focusing a laser beam on a recording surface of the disk; Moving means (3) for moving the objective lens in a direction perpendicular to the recording surface of the disk so as to focus the objective lens on the recording surface of the disk; and means (14) for removing a noise component of a signal for driving the objective lens. Means for switching between a constant voltage value for driving the objective lens required to temporarily bring the objective lens closer to the disk surface and a constant voltage value for driving the objective lens required to move the objective lens away from the disk surface (18) ) And the signal to drive the objective lens with the noise component removed,
Means (1) for adding the switched constant voltage value
7) means for detecting a switching point of a layer generated when the objective lens is moved to a layer having another recording surface by temporarily moving the objective lens closer to or away from the disk surface from a layer having a certain recording surface. (12); and (13) means for controlling the means for switching the constant voltage value in accordance with a detection signal from the means for detecting a switching point of the layer, and (13), wherein one surface has a recording surface. For a disc having two or more layers, a signal obtained by adding a constant voltage value to a drive signal of the objective lens from which a noise component has been removed from the focal point of the recording surface of a certain layer is given to the moving means of the objective lens. The objective lens is forcibly moved to another layer, and at the switching point of the layer generated at the time of this movement, a constant voltage value applied to the moving means of the objective lens is controlled so that the objective lens is moved to another layer. Focus on recording surface Optical disc apparatus being characterized in that as drawn. 2. The means (12) according to claim 1, wherein the means (12) for detecting a switching point of the layer generated when the objective lens moves from a layer having a certain recording surface to a layer having another recording surface comprises An optical disc device for detecting, with hysteresis, a zero cross point of an S-shaped curve of a focus error signal in a point aberration method. 3. The device according to claim 1, wherein the means for controlling the means for switching the constant voltage value detects a switching point of the layer when moving from the disk surface to another layer in the back. Until this is done, switch to a constant voltage value that drives the objective lens closer to the disk, and when a layer switching point is detected, switch to a constant voltage value that drives the objective lens away from the disk. When moving from the back of the disc to another layer on the surface, the voltage is switched to a constant voltage value for driving the objective lens away from the disc until a switching point of the layer is detected. When the switching point is detected, control is performed to switch to a constant voltage value for driving the objective lens so as to approach the disk. Disk device.