JPH1125469A - Focus controller for multi-layer optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute appropriate focus jump in a multi-layered optical recording medium by inhibiting the detection of the lowering of readout signals using a dropout detecting means for a specified period of time after the control section resumes the focus servo using focus jump control. SOLUTION: A microcomputer 8 controls various sections based on the instructions of an operation section 18 and conducts a focus jump operation to reliably move the focal position from the first layer to the second one of a two-layer optical disk 1. Next, the computer 8 closes a focus servo loop and since then a focus actuator 30 conducts the stationary focus servo operation which makes the focal position of the readout light follow the recording surface of the second layer. Then during a specified period of time after a zero-cross detection circuit 6 detects the fourth zero-cross point of the focus error signal FE, a computer 8 inhibits the dropout detection circuit 20 from detecting the lowering of readout signals. By this, focus jump can be appropriately executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus control device provided in a reproducing apparatus for reproducing a multilayer optical recording medium.

[0002]

2. Description of the Related Art In order to increase the recording density of a disk, there is a method of multiplexing information in a direction perpendicular to the disk surface.
A multi-layer optical disc enables such multiplexed information recording in the vertical direction. For example, in the case of a two-layer optical disc, the first layer and the second layer form a spacer region as shown in FIG. The first layer of the reflective layer, which is formed between the layers and is close to the light irradiation surface of the disk, is formed as a translucent film so that light reaches the second layer.

In the reproduction of such a multilayer optical disk, when switching the layer from which recorded information is to be read, it is necessary to perform a focus jump operation for immediately adjusting the focus to the next read layer by a focus control device. Usually, a focus jump operation for shifting the focus of the reading light from the information recording surface of one layer to the information recording surface of the other layer is performed based on zero-cross detection of a focus error signal generated based on the output of the pickup. Done.

More specifically, the pickup has a focal point of the reading light in a direction perpendicular to the disk surface by driving, for example, an objective lens for determining the focal point of the reading light emitting optical system in the optical axis direction. Is provided. An acceleration signal as a focus jump start signal for moving the focus of the reading light to a target recording surface is supplied to the focus actuator at an early stage of the focus jump operation. Then, the supply of the acceleration signal is terminated or the displacement of the focus actuator in response to the acceleration signal is stopped based on the zero-cross timing sequentially detected from the focus error signal obtained during the displacement of the focus actuator in response to the acceleration signal. A series of operations of supplying a deceleration signal for stopping the deceleration to the focus actuator, or terminating the supply of the deceleration signal and restarting the focus servo on the target recording surface are performed.

By the way, in a normal optical disk reproducing apparatus, when recorded data cannot be read properly and is lost due to scratches or dirt on the disk surface, focus control and tracking control do not malfunction. Is provided with a dropout detection circuit. The dropout detection circuit detects that the read signal from the optical disc has dropped below the threshold value due to scratches, dirt, or the like. The focus control device stops the focus servo while the dropout detection signal is being supplied from the dropout detection circuit, and holds and outputs the focus error signal immediately before the dropout detection signal is generated.

A configuration using such a dropout detection circuit is also conceivable in a reproducing apparatus for reproducing the above-mentioned multilayer optical disk.

[0007]

However, in the focus control device for a multilayer optical disc, the displacement of the focus actuator given by the acceleration signal during the focus jump operation is too large, and the movement of the target layer to the recording surface is appropriate. May not be performed. In this case, the overshoot of the focus error signal increases immediately after the generation of the deceleration signal stops and the focus jump operation ends, and the focus position deviates from the recording surface of the target layer. Accordingly, the dropout detection circuit may generate a dropout detection signal. When the dropout detection signal is generated from the dropout detection circuit, the focus control device stops the focus servo and holds the focus error signal immediately before the dropout detection signal is generated. It becomes difficult to focus on the object.

An object of the present invention is to provide a focus control device for a multilayer optical recording medium that can appropriately perform a focus jump in a multilayer optical recording medium.

[0009]

SUMMARY OF THE INVENTION A focus control apparatus for a multilayer optical recording medium according to the present invention resumes focus servo after once releasing focus servo and moving a focus position of read light to another target layer. And a drop-out detecting means for detecting a drop in the read signal due to the reading light, wherein the control section performs the predetermined time after the focus servo is resumed by the focus jump control. It is characterized in that detection of a decrease in the read signal is prohibited.

The focus control apparatus for a multilayer optical recording medium according to the present invention performs focus jump control for once releasing the focus servo, moving the focus position of the read light to another target layer, and then restarting the focus servo. A control unit;
The control unit includes: a dropout detection unit configured to detect a drop in the read signal due to the reading light; and a dropout compensation unit configured to perform a predetermined compensation process on the focus error signal in accordance with the detection of the dropout. It is characterized in that the predetermined compensation processing by the dropout compensating means is prohibited for a predetermined time even after the servo is restarted.

Further, the focus control apparatus for a multilayer optical recording medium according to the present invention has a focus control for reproducing a recording medium having an information recording surface in each of at least two layers formed in a direction perpendicular to the surface. An apparatus for irradiating a recording medium with a reading light, receiving a return light from the recording medium by the reading light, reading a signal indicating information recorded on the recording medium, and a focusing error of the reading light with respect to the information recording surface. Pickup means for generating a focus error signal indicating zero, a zero cross detection means for detecting a zero cross of the focus error signal, a command means for generating a focus jump command, and focusing the read light on the information recording surface according to the focus error signal. The focus servo operation for driving the focus actuator of the pickup means is performed to At least in response to a Jump command 2
The jump drive operation of the focus actuator is started to move the focus position of the reading light from the recording surface of any one of the two layers to the recording surface of the other layer, and the zero-cross detection means starts the jump driving operation on the recording surface of the other layer. A drive unit that stops the jump drive operation of the focus actuator and returns to the focus servo operation in response to a corresponding zero-cross detection time, a dropout detection unit that generates a dropout detection signal when the read signal is reduced, A drop-out compensating means for holding the focus error signal immediately before the drop-out detection signal is generated and supplying the focus error signal to the driving means according to the generation of the drop-out detection signal; Dropout detection means or dropout compensation until time elapses It is characterized in that a prohibition means for prohibiting the operation of the stage.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows a schematic configuration of an optical disk player using the focus control device according to one embodiment of the present invention. In FIG. 2, the disc 1 loaded (set) in the player is the two-layer optical disc shown in FIG. 1, and is driven to rotate by a spindle motor 2 and irradiated with read light emitted from a pickup 3. . This reading light reaches the recording surface (reflection surface) of the first layer or the second layer via the protective layer of the disk 1 and is modulated by so-called recording marks, such as pits, formed on the recording surface. Then, the light is reflected from the recording surface and returns to the pickup 3.

The pickup 3 not only emits reading light but also performs photoelectric conversion for receiving reflected light from the disk 1 and generating various electric signals according to the amount and / or state of the reflected light. Of the electric signals emitted by the pickup 3, a read signal (a so-called RF signal (Radio signal) mainly having a signal component corresponding to information recorded on the disc 1)
Frequency) is amplified by the RF amplifier 4 and then transmitted to a read signal processing system (not shown). The read signal processing system reproduces a final audio or video signal or computer data signal from the RF signal, and derives such a reproduced signal to, for example, the outside of the player.

The focus error generation circuit 5 generates a focus error signal FE for the recording surface of the reading light based on another electric signal emitted by the pickup 3. Still another electric signal emitted by the pickup 3 is supplied to a tracking servo system (not shown). In the tracking servo system, a tracking error signal is generated based on the electric signal, and control is performed such that the irradiation position of the reading light coincides with the center of the recording track of the disk in accordance with the tracking error signal.

As an example of a mode for generating a focus error signal, as a light receiving system of the pickup 3, the reflected light from the disk is transmitted through a cylindrical lens to give astigmatism to the reflected light, and the reflected light after the transmission is transmitted. Is received by a four-segment photodetector. The light-receiving surface of the four-divided photodetector has four light-receiving portions divided by two straight lines orthogonal to each other at the light-receiving center, and the received reflected light is received according to the focusing state of the read light with respect to the recording surface of the disk. Based on the change in the shape and the intensity at the point, the photoelectric conversion signals of the light receiving units positioned point-symmetrically with respect to the light receiving center are added together, and a signal corresponding to the difference between the two added signals obtained as a focus error signal is obtained. It outputs.

In one example of a mode for generating a read signal, when the above-described four-segment photodetector is used, the read signal can be derived from the sum of the photoelectric conversion signals of all the light receiving units, but can be obtained from another detector. good. The focus error signal is output at a zero level when the relative distance between the pickup 3 and the objective lens in each of the first and second layers is at a reference value, as shown in FIG. 3, and varies according to the displacement from the reference value. The output level has an S-shaped characteristic that changes continuously, and the polarity of the focus error signal of each layer is opposite between the adjacent first and second layers. In the middle between the layers,
There is an undefined area where a focus error signal cannot be obtained.

There are three methods for generating the tracking error signal.
Although there is a beam method, when a tracking error is obtained by a single light beam, there is also a method called a phase difference method or a push-pull method. The pickup 3 has a built-in focus actuator 30 for moving an objective lens for irradiating the disk 1 with read light emitted from a light source in the optical axis direction. The focus actuator 30 displaces the objective lens in a direction perpendicular to the surface of the disk 1 according to the level and polarity of a drive signal described later.

The output of the focus error generation circuit 5 is connected to a zero cross detection circuit 6 and an equalizer 7. The zero-cross detection circuit 6 detects that the level of the focus error signal FE output from the focus error generation circuit 5 has passed two threshold values ± Vth close to zero level, and a zero-cross detection signal FZ according to the detection result.
C is generated and supplied to the microcomputer 8. The equalizer 7 performs waveform equalization processing on the supplied focus error signal FE, and supplies the equalized focus error signal to the adder 10 via the hold circuit 9.
The hold circuit 9 includes an on / off switch 11 and a capacitor 1
And 2.

The microcomputer 8 controls the focus actuator 30 based on the zero-cross detection signal FZC.
A kick pulse FKP for accelerating and displacing in a predetermined direction, and a brake pulse FBP and a jump status signal FJUMP for decelerating the focus actuator 30 being displaced by the kick pulse to stop the displacement in the predetermined direction are generated. Occur. The pulses FKP and FBP are both supplied to the jump pulse generation circuit 13.
The jump status signal is supplied to a control input terminal of the on / off switch 11.

The jump pulse generation circuit 13 generates a jump pulse composed of a kick pulse FKP and a brake pulse FBP in response to a pulse generation command signal and a pulse generation stop command signal from the microcomputer 8, and generates the jump pulse FKP and the brake pulse. FBP is given a corresponding polarity. Jump pulse generation circuit 13
Are supplied to the adder 10.

The adder 10 adds the signal from the hold circuit 9 and the jump pulse from the jump pulse generation circuit 13 and supplies the added output to the driver amplifier 17. The driver amplifier 17 generates a drive signal according to the output of the adder 10 and supplies the drive signal to the focus actuator 30. A dropout detection circuit 20 is connected to an output line of the pickup 3 to the RF amplifier 4. The dropout detection circuit 20 detects a dropout of the RF signal from the pickup 3 and generates a dropout detection signal during the detection period of the dropout.

As shown in FIG. 4, a specific configuration of the dropout detection circuit 20 is as follows: first and second peak detection circuits 21 and 22 for receiving RF signals, respectively;
A comparison circuit 23 compares the levels of the output signals 1 and 22 and outputs a signal of the comparison result. The first peak detection circuit 21 detects the peak of the RF signal with a predetermined time constant.
With respect to the RF signal shown in (a), a detection output D1 having a waveform as shown in FIG. 5B along the upper envelope of the RF signal is generated. The second peak detection circuit 22 includes a first
The peak detection of the RF signal is performed with a time constant larger than the time constant for detection in the peak detection circuit 21. As shown in FIG. 5B, the detection of the RF signal is far more than the detection output D1. A detection output D2 having a level fluctuation slow to a peak fluctuation is generated. The comparison circuit 23 compares the levels of the detection outputs D1 and D2, and as shown in FIG. 5C, a high level drop occurs while the level of the detection output D1 is lower than the level of the detection output D2. An out detection signal DOC is generated. The dropout detection signal is supplied to the microcomputer 8.

On the other hand, when the microcomputer 8 receives the focus jump command signal FTRIG for moving the focus position of the reading light to the recording surface of another layer from the operation unit 18, the microcomputer 8 executes the processing that has been executed up to that point. At the interruption, the focus jump operation shown in FIG. 6 is started. In this focus jump operation, it is assumed that the focus position is moved from the recording surface of the first layer of the disc 1 to the recording surface of the second layer.

The microcomputer 8 first releases the focus servo loop (step S1). Specifically, by raising the jump status signal FJUMP, the jump status signal FJUMP causes the on / off switch 11 of the hold circuit 9 to be turned off.
The accumulation level of the capacitor 12 of the hold circuit 9 at that time, that is, the focus error signal level immediately before turning off is held and output to the adder 10. Then, the microcomputer 8 resets the flag FRAG to be equal to 0 (step S2), and then starts the kick pulse FKP (step S3).

Thus, the jump pulse generating circuit 13
Generates a jump pulse FP having a high positive polarity level corresponding to the kick pulse.
Forms an addition output of a level obtained by adding the positive high level indicated by the jump pulse FP and the holding level supplied from the holding circuit 9, and a drive signal FD corresponding to the addition output is supplied from the driver amplifier 17 to the focus actuator. 30. Accordingly, during the period in which the kick pulse FKP is generated, the actuator 30 is forcibly accelerated in the direction in which the focus position of the reading light moves to the new target recording surface of the second layer. Accordingly, as the focus position of the reading light moves away from the recording surface of the first layer which has been following the focus error signal FE, the absolute value of the level increases, and the minimum value (see Vmin in FIG. 7) After that, a valley-shaped change that returns to the zero level again is exhibited.

With the start of the kick pulse,
The microcomputer 8 activates a window timer formed in the internal circuit or the program to generate the kick pulse or the status signal FJUMP.
From the rising edge of the predetermined time tw (step S4). In FIG. 7, such a timing operation state is indicated by a high-level pulse waveform FW.

A predetermined time t by this window timer
During w, the microcomputer 8 does not respond to the zero-crossing detection signal FZC received from the zero-crossing detection circuit 6. More specifically, the zero-cross detection signal FZC
Are not counted even if not only the falling edge but also the rising edge arrives. Therefore, this predetermined time t
During w, the falling and rising edges of the zero-cross detection signal FZC, which is the zero-cross detection timing, are masked. Therefore, the predetermined time t
During w, at least the zero cross point ZC1 as shown in FIG. 7 is ignored.

Since the control for terminating the kick pulse during the predetermined time tw is not performed based on the detection of the zero cross, even if the focus error signal fluctuates during the predetermined time tw due to a flaw or the like, an abnormal zero cross is exhibited. ,
The kick pulse does not end prematurely by mistake, and the jump operation to the target recording surface can be surely succeeded.

When the window timer has counted the predetermined time tw, the microcomputer 8 releases the masking, monitors the zero-cross detection signal FZC, and detects the rising edge (step S5). The masking for the predetermined time tw is performed by the focus error signal FE.
Is changed from near the zero level to the minimum value Vmin, the detection is performed across the first zero crossing detection point ZC1. Therefore, the microcomputer 8 determines in this step S5
At the second zero cross point ZC2, that is, the rising edge of the zero cross detection signal FZC is detected instead of the falling edge.

The zero-cross detecting circuit 6 detects the zero-cross of the focus error signal FE as follows. That is, for the negative polarity level of the focus error signal FE, it is detected that a zero cross has occurred when the level crosses a predetermined threshold value -Vth. It is detected that a zero cross has occurred when the signal crosses the threshold value + Vth. It is determined that the absolute values of the threshold values -Vth and Vth are such that the focus error signal FE is far away from the vicinity of the zero level, and the focus error signal FE has sufficiently reached the vicinity of the zero level from the relatively large absolute value level. A value that can be determined to have been set is set.

In step S5, the second zero cross point Z
When C2 is detected, the microcomputer 8 lowers the kick pulse FKP (Step S6). As a result, the jump pulse generation circuit 13 causes the output jump pulse FP to fall to the zero level.
0 is an addition output of the sum of the zero level indicated by the jump pulse FP and the hold level supplied from the hold circuit 9, that is, the output level of the hold circuit 9 is obtained. Accordingly, the focus actuator 30 has
The drive signal FD, whose level has dropped sharply, is supplied from the driver amplifier 17. However, since there is a moment of inertia of the drive due to the kick pulse FKP generated earlier, the focus actuator 30 can reduce the speed and reduce the speed of the read light. The displacement for moving the focus position to the target recording surface is continued.

Thereafter, the microcomputer 8 monitors the zero-cross detection signal FZC and detects the falling edge (step S7). This is the third zero cross point Z
This corresponds to detection of C3. The focus error signal FE is
Immediately after entering the focus control range for the target recording layer of the second layer, the third zero-cross point ZC exceeding the threshold + Vth is exceeded.
3 will be detected.

When the third zero cross point ZC3 is detected,
The microcomputer 8 starts up the brake pulse FBP (step S8). As a result, the jump pulse generation circuit 13 further lowers the output jump pulse FP to a low level of negative polarity.
The sum output of the low level indicated by the jump pulse FP and the hold level output from the hold circuit 9 is supplied to the driver amplifier 17. Accordingly, a drive signal FD for stopping the movement of the focus position of the read light to the target recording surface is supplied to the focus actuator 30, and the focus actuator 30
The displacement speed is gradually reduced.

In such a deceleration process of the actuator, the microcomputer 8 outputs the zero-cross detection signal F
The ZC is monitored, and its rising edge is detected (step S9). This corresponds to the detection of the fourth zero cross point ZC4. The focus error signal FE increases in level as the focal point of the reading light approaches the target recording surface from the position corresponding to the third zero-cross point ZC3, and after a maximum value (see Vmax in FIG. 7), the focus error signal FE turns around. The level gradually decreases, and when the focus of the reading light has just reached the target recording surface, the zero level is exhibited.
4 will be detected.

When the fourth zero cross point ZC4 is detected,
The microcomputer 8 causes the brake pulse FBP to fall (step S10) and the jump status signal F
JUMP is lowered to close the focus servo loop (step S11). As a result, the jump pulse generation circuit 13 raises the output jump pulse FP to zero level. Also, the microcomputer 8 turns on the switch 11 and controls the focus error signal from the equalizer 7 to be relayed to the driver amplifier 17 via the adder 10. Therefore, the focus actuator 30 thereafter performs a steady focus servo operation of following the focus position of the read light with respect to the target recording surface based on the focus error signal FE.

The microcomputer 8 determines in step S11
It is determined whether or not a predetermined time Tc has elapsed from the execution of (Step S12). This fixed time Tc is equal to or shorter than the focus error signal F after the fourth zero cross point ZC4 is detected.
As indicated by reference character A in FIG. 7, E is set to a time slightly longer than the maximum time that can be considered as the time required until the convergence to the vicinity of the zero level after the overshoot. If the microcomputer 8 determines that the predetermined time has elapsed, it sets 1 to the flag FRAG (step S1).
3).

Thus, the focus jump operation is completed, and the microcomputer 8 shifts to, for example, a mode for reproducing the recorded information on the target recording surface. Further, the microcomputer 8 performs a dropout compensation operation at predetermined timings separately from the focus jump operation. In the drop-out compensation operation, the microcomputer 8 first sets the flag FRA as shown in FIG.
It is determined whether G is equal to 1 (step S21).
If FRAG = 1, whether the flag FRAG remains set to 1 in step S13 of the focus jump operation,
Since this is the initial state, the focus jump operation is not performed. Accordingly, the microcomputer 8 determines whether or not the dropout detection circuit 20 outputs a dropout detection signal (Step S22). If the dropout detection signal has not been output, this dropout compensation operation is immediately terminated. If the dropout detection signal has been output, an FE hold signal is generated (step S23). The FE hold signal causes the on / off switch 11 of the hold circuit 9 to be turned off, and the accumulation level of the capacitor 12 of the hold circuit 9 at that time, that is, the focus error signal level immediately before the off state is held and output to the adder 10. The supply of the hold level of the hold circuit 9 to the adder 10 is as follows.
The process is continued until it is determined in step S22 that the dropout detection signal is not output.

On the other hand, if it is determined in step S21 that FRAG = 0, the microcomputer 8 determines in step S2 of the focus jump operation that the flag F
RAG is set to 0, which means that the focus jump operation is being performed. Therefore, at this time, the dropout compensation operation is immediately terminated, and the holding level of the focus error signal level is not given to the adder 10.

As a result of this dropout compensation operation, even if a dropout is detected during the focus jump operation period in which FRAG = 0 is set, it is ignored, and the focus error signal level due to the dropout detection is determined. Holding operation is prohibited. Therefore,
After the fourth zero-crossing point ZC4 is detected, the focus error signal FE is held by the dropout detection operation until the focus error signal FE overshoots and converges to around the zero level as indicated by reference numeral A in FIG. Is prohibited, a sufficient control amount can be obtained, the focus control operation is prevented from becoming unstable, and the in-focus position can be quickly converged on the target recording surface.

In the above-described embodiment, the predetermined time Tc is the maximum time that can be considered as the time from when the fourth zero cross point ZC4 is detected until the focus error signal FE overshoots and converges to near zero level. Although it is set slightly longer than the time, the fixed time Tc may be set shorter than the maximum time. In this case, as shown in FIG.
If it is determined that the predetermined time has elapsed, it is determined whether a dropout detection signal has been generated (step S14), and after confirming that no dropout detection signal has been generated, the process proceeds to step S13. With the flag FRA
G is set to 1.

In the above-described embodiment, a two-layer optical disc has been described. However, the present invention is not limited to this, and the present invention may be applied to a focus control device of an apparatus for reproducing another multi-layer optical recording medium including a multi-layer optical disc having three or more layers. Can be applied. Further, in the above-described embodiment, the dropout compensation operation is prohibited during the fixed time Tc, but the dropout detection operation may be prohibited so that the dropout compensation operation does not occur.

[0042]

According to the present invention, until the focus position of the reading light is stabilized on the recording surface of the target layer by the focus jump, even if the dropout of the reading signal is detected, the focus error signal immediately before the detection is detected. Is not held, so that the focus jump can be appropriately performed in the multilayer optical recording medium.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of a two-layer optical disc.

FIG. 2 is a block diagram illustrating a configuration of a focus control device according to the present invention.

FIG. 3 is a diagram illustrating an undefined area of a focus error signal.

FIG. 4 is a block diagram illustrating a dropout detection circuit.

FIG. 5 is a waveform chart showing an operation of the dropout detection circuit.

FIG. 6 is a flowchart illustrating a focus jump operation.

FIG. 7 is a waveform diagram showing a focus jump operation.

FIG. 8 is a flowchart illustrating a dropout compensation operation.

FIG. 9 is a flowchart showing another focus jump operation.

[Description of Signs of Main Parts]

 DESCRIPTION OF SYMBOLS 1 Double-layer optical disk 2 Spindle motor 3 Pickup 4 RF amplifier 5 Focus error generation circuit 6 Zero cross detection circuit 7 Equalizer 8 Microcomputer 9 Hold circuit 13 Jump pulse generation circuit 20 Dropout detection circuit 30 Focus actuator

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor A. Blood Show, Kawagoe City, Saitama Prefecture 25-1, Nishimachi, Yamada, Pioneer Corporation Kawagoe Factory (72) Inventor Hitoshi Yamazaki 25, Nishimachi, Yamada, Kawajie, Saitama Prefecture 251, Pioneer Kawagoe Factory (72) Inventor Kawana Kazushige Kawagoe City, Saitama Prefecture 25-1, Nishimachi, Yamada, Pioneer Corporation Pioneer Corporation Kawagoe Factory (72) Inventor Masakazu Takahashi 25-25, Nishimachi, Yamada Character, Kawagoe City, Saitama Prefecture 1 Pioneer Corporation Kawagoe Factory

Claims (7)

[Claims] 1. A focus control apparatus for a multilayer optical recording medium, comprising: a focus jump control for releasing a focus servo once, moving a focus position of read light to another target layer, and restarting the focus servo. And a drop-out detecting means for detecting a decrease in a read signal due to the read light, wherein the control section detects the drop-out for a predetermined time after the focus servo is resumed by the focus jump control. A focus control device for a multilayer optical recording medium, wherein the detection of a decrease in the read signal by means is prohibited. 2. A focus control apparatus for a multi-layer optical recording medium, comprising: a focus jump control for releasing a focus servo once, moving a focus position of read light to another target layer, and restarting the focus servo. A control unit, a dropout detection unit that detects a dropout of a read signal due to the readout light, a dropout compensation unit that performs a predetermined compensation process on a focus error signal in accordance with the detection of the dropout,
A focus control device for a multilayer optical recording medium, wherein the control unit prohibits the predetermined compensation processing by the dropout compensating means for a predetermined time after the focus servo is resumed by the focus jump control. . 3. A focus control device for reproducing a recording medium having an information recording surface in each of at least two layers formed in a direction perpendicular to the surface, wherein the recording medium is irradiated with reading light. Receiving the return light from the recording medium by the reading light to generate a reading signal indicating information recorded on the recording medium and a focus error signal indicating a focusing error of the reading light with respect to an information recording surface. Pickup means; zero-cross detection means for detecting a zero-cross of the focus error signal; command means for generating a focus jump command; and the pickup means for focusing the read light on an information recording surface in accordance with the focus error signal. Focus servo operation for driving the focus actuator of Starting a jump drive operation for the focus actuator to move the focus position of the read light from the recording surface of one of the at least two layers to the recording surface of the other layer in response to the command. A driving unit that stops the jump driving operation and returns to the focus servo operation in response to a zero crossing detection point corresponding to the recording surface of the other layer by the zero crossing detection unit; Dropout detection means for generating a dropout detection signal when the dropout detection signal is generated, and in response to the generation of the dropout detection signal, dropout compensation means for holding the focus error signal immediately before the generation and supplying the focus error signal to the driving means, A predetermined time after the focus jump command is issued and after the jump drive operation of the driving unit is stopped A focus control device for a multilayer optical recording medium, comprising: a prohibition unit that prohibits the operation of the dropout detection unit or the dropout compensation unit until a time point between the two. 4. The predetermined time is a fixed time slightly longer than a maximum predicted time from when a zero cross corresponding to the recording surface of the other layer is detected to when the focus error signal overshoots and converges to near zero level. 4. The focus control device for a multilayer optical recording medium according to claim 3, wherein: 5. The multilayer according to claim 3, wherein said prohibiting means releases the operation of said dropout compensating means when said dropout detection signal is not generated after said predetermined time has elapsed. Focus control device for optical recording media. 6. The predetermined time is a fixed time slightly shorter than a maximum predicted time from when a zero cross corresponding to the recording surface of the other layer is detected to when the focus error signal overshoots and converges to near zero level. The focus control device for a multilayer optical recording medium according to claim 5, wherein: 7. The multilayer optical system according to claim 3, wherein said dropout detection means generates a dropout detection signal when a peak level or an amplitude level of said read signal has fallen below a threshold value. Focus control device for recording media.