JP3497698B2 - Focus control device for multilayer optical recording medium - Google Patents

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 device for reproducing a multilayer optical recording medium.

[0002]

2. Description of the Related Art There is a method of multiplexing information in a direction perpendicular to the disk surface in order to increase the recording density of the disk.
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 reflective layer, which is sandwiched and is close to the light irradiation surface of the disc, is formed as a semitransparent film so that light reaches the second layer.

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

More specifically, in the pickup, for example, an objective lens, which is an emission optical system for reading light and determines the focus of the reading light, is displaced and driven in the optical axis direction so that the focus of the reading light is perpendicular to the disk surface. A focus actuator that displaces at is provided. An acceleration signal, which is a focus jump start signal for moving the focus of the reading light to the target recording surface, is supplied to the focus actuator at the initial stage of the focus jump operation. Then, based on the timing of the zero cross that is sequentially detected from the focus error signal obtained during the displacement of the focus actuator in response to this acceleration signal, the supply of the acceleration signal is terminated or the displacement of the focus actuator in response to the acceleration signal. A series of operations of supplying a deceleration signal to stop the focus actuator to the focus actuator, and further ending the supply of the deceleration signal to restart the focus servo on the target recording surface are performed.

By the way, in an ordinary optical disk reproducing apparatus, focus control and tracking control are prevented from malfunctioning when recording data cannot be read properly and is lost due to scratches or dirt on the disk surface. Is provided with a dropout detection circuit. The dropout detection circuit detects that the read signal from the optical disk has dropped below a threshold value due to scratches or dirt. The focus control device stops the focus servo while the dropout detection signal from the dropout detection circuit is supplied, 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 disk, the displacement of the focus actuator given by the acceleration signal during the focus jump operation is too large and the target layer is appropriately moved to the recording surface. It may not be done. In this case, the overshoot of the focus error signal increases immediately after the deceleration signal stops and the focus jump operation ends, and the in-focus position deviates from the recording surface of the target layer. In response, the dropout detection circuit may generate a dropout detection signal. When a dropout detection signal is generated from the dropout detection circuit in this way, 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.

Therefore, an object of the present invention is to provide a focus control device for a multilayer optical recording medium, which can appropriately perform a focus jump on the multilayer optical recording medium.

[0009]

A focus control apparatus for a multilayer optical recording medium according to the present invention resumes the focus servo after temporarily canceling the focus servo and moving the focus position of the reading light to another target layer. And a dropout detection means for detecting a decrease in the read signal due to the reading light. The control section is configured to perform the dropout detection means for a predetermined time even after the focus servo is restarted by the focus jump control. The feature is that the detection of the decrease in the read signal is prohibited.

The focus control device for a multilayer optical recording medium according to the present invention performs focus jump control in which the focus servo is once released and the focus position of the reading light is moved to another target layer, and then the focus servo is restarted. A control unit,
The control unit includes a dropout detection unit that detects a decrease in the read signal due to the reading light and a dropout compensation unit that performs a predetermined compensation process on the focus error signal according to the detection of the dropout. It is characterized in that the predetermined compensation processing by the dropout compensation means is prohibited for a predetermined time even after the servo is restarted.

Further, the focus control apparatus for a multilayer optical recording medium of the present invention is a focus control for reproducing a recording medium having an information recording surface on each of at least two layers formed in a direction perpendicular to the surface. The device is a device for irradiating the recording medium with the reading light and receiving the returning light from the recording medium due to the reading light, and a reading signal indicating information recorded on the recording medium and a focusing error of the reading light with respect to the information recording surface. , A pickup means for generating a focus error signal, a zero cross detecting means for detecting a zero cross of the focus error signal, a command means for generating a focus jump command, and a reading light focused on the information recording surface according to the focus error signal. In order to perform the focus servo operation to drive the focus actuator of the pickup means, At least in response to a Jump command 2
A jump drive operation is started for the focus actuator 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 causes the recording surface of the other layer to move. Drive means for stopping the jump drive operation of the focus actuator and returning to the focus servo operation in response to the corresponding zero-cross detection time; and dropout detection means for generating a dropout detection signal when the read signal is low, Dropout compensation means for supplying a focus error signal immediately before the dropout detection signal to the drive means in response to the generation of the dropout detection signal, and a predetermined time after the focus jump command is issued and after the jump drive operation of the drive means is stopped. Dropout detection means or dropout compensation until the end of time It is characterized in that a prohibition means for prohibiting the operation of the stage.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 shows a schematic configuration of an optical disc player using a focus control device according to an 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, which is rotationally driven by the spindle motor 2 and irradiated with the reading light emitted from the pickup 3. . This reading light reaches the recording surface (reflection surface) of the first layer or the second layer through the protective layer of the disc 1, and is modulated by a so-called recording mark that carries recorded information such as pits formed on the recording surface. In response, the reflected light from the recording surface is returned to the pickup 3.

The pickup 3 not only emits the reading light but also receives the reflected light from the disk 1 and performs photoelectric conversion to generate various electric signals according to the quantity and / or state of the reflected light. Of the electric signal emitted by the pickup 3, a read signal (so-called RF signal (Radio signal) mainly having a signal component corresponding to the recorded information on the disk 1 is used.
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 the final audio or video signal or computer data signal from the RF signal, and derives such a reproduced signal to the outside of the player, for example.

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 generated 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 the irradiation position of the reading light is controlled so as to coincide with the center of the recording track of the disk according to the tracking error signal.

As an example of a mode of generating the 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. There is a configuration in which a four-division photo detector receives light. The light-receiving surface of the four-division photodetector has four light-receiving sections divided by two straight lines orthogonal to each other at the light-receiving center, and the received reflected light is the light-receiving surface according to the focus state of the read light with respect to the recording surface of the disc. On the basis of changing the shape and intensity of the light receiving section, the photoelectric conversion signals of the light receiving sections located point-symmetrically with respect to the light receiving center are added, and the signal corresponding to the difference between the two added signals is used as the focus error signal. It outputs it.

In one example of the mode for generating the read signal, when the above-mentioned four-division photodetector is used, it can be derived from the sum of the photoelectric conversion signals of all the light receiving portions, but it may be obtained from another detector. good. As shown in FIG. 3, the focus error signal is a zero level output when the relative distance between the objective lens of the pickup 3 and each of the first and second layers is at the reference value, and the focus error signal changes depending on the displacement from the reference value. The output level has an S-shaped characteristic that continuously changes, and the polarities of the focus error signals of the respective layers are opposite to each other between the adjacent first and second layers. Also, in the center between the layers,
An uncertain region where a focus error signal cannot be obtained occurs.

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

A zero-cross detection circuit 6 and an equalizer 7 are connected to the output of the focus error generation circuit 5. 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 the zero cross detection signal FZ corresponding to the detection result is detected.
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.
2 and.

The microcomputer 8 uses the focus actuator 30 based on the zero-cross detection signal FZC.
A kick pulse FKP for accelerating and displacing in a predetermined direction, a brake pulse FBP for decelerating the focus actuator 30 in the middle of the displacement by this kick pulse to stop the displacement in the predetermined direction, and a jump status signal FJUMP. Occur. Both the pulses FKP and FBP are jump pulse generation circuits 13
In addition, the jump status signal is supplied to the 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 the kick pulse FKP and the brake pulse. The FBP is given a corresponding polarity. Jump pulse generation circuit 13
The output pulse of 1 is supplied to the adder 10.

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

The specific construction of the dropout detection circuit 20 is, as shown in FIG. 4, first and second peak detection circuits 21 and 22, which respectively receive RF signals, and these detection circuits 2.
And a comparison circuit 23 which compares the levels of the output signals of 1 and 22 and outputs the signal of the comparison result. The first peak detection circuit 21 detects the peak of the RF signal with a predetermined time constant, for example, as shown in FIG.
For the RF signal shown in (a), a detection output D1 having a waveform as shown in FIG. 5 (b) along the upper envelope of the RF signal is generated. The second peak detection circuit 22 has a first
The peak of the RF signal is detected with a time constant larger than the time constant for detection in the peak detection circuit 21, and as shown in FIG. 5 (b), the peak of the RF signal is much higher than that of the detection output D1. A detection output D2 having a level fluctuation that is slow with respect to the peak fluctuation is generated. The comparison circuit 23 compares the respective levels of the detection outputs D1 and D2, and as shown in FIG. 5C, a high level drop is generated while the level of the detection output D1 is lower than the level of the detection output D2. The 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 from the operation unit 18 the focus jump command signal FTRIG for moving the focus position of the reading light to the recording surface of the other layer, the microcomputer 8 performs the processing executed up to that point. By interrupting, 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 opens the focus servo loop (step S1). Specifically, the jump status signal FJUMP causes the on / off switch 11 of the hold circuit 9 to be turned off by raising the jump status signal FJUMP.
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 make it equal to 0 (step S2), and then raises the kick pulse FKP (step S3).

As a result, the jump pulse generating circuit 13
Generates a jump pulse FP having a positive high level corresponding to this kick pulse, the adder 10
Represents 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 hold circuit 9, and the drive signal FD corresponding to this addition output is output from the driver amplifier 17 to the focus actuator. Is supplied to 30. Therefore, during the generation period of the kick pulse FKP, the actuator 30 is forcibly accelerated in the direction in which the focus position of the reading light moves to the newly targeted recording surface of the second layer. Along with this, the focus error signal FE increases in absolute value of the level as the in-focus position of the read light moves away from the recording surface of the first layer, which has been following up to that point, and reaches a minimum value (see Vmin in FIG. 7). After passing through, it will show a valley-shaped change that returns to zero level again.

With the rise of such a kick pulse,
The microcomputer 8 activates a window timer formed in its internal circuit or program to cause the kick pulse or the status signal FJUMP.
The clocking of a predetermined time tw is started from the rising of (step S4). In FIG. 7, such a clocking operation state is shown 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-cross detection signal FZC received from the zero-cross detection circuit 6. More specifically, the zero-cross detection signal FZC
These are not counted even when not only the falling edge but also the rising edge. 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-crossing point ZC1 as shown in FIG. 7 is ignored.

Since the control for ending the kick pulse during this predetermined time tw is not performed based on the zero-cross detection, even if the focus error signal fluctuates during the predetermined time tw due to a scratch or the like and an abnormal zero-cross is exhibited. ,
It is possible to surely succeed in the jump operation to the target recording surface without accidentally ending the kick pulse early.

When the window timer measures the predetermined time tw, the microcomputer 8 releases the masking, monitors the zero-cross detection signal FZC, and detects its rising edge (step S5). The masking for the predetermined time tw described above is performed by the focus error signal FE.
Is crossed over the first zero-cross detection point ZC1 when the level changes from the vicinity of the zero level to the minimum value Vmin. Therefore, the microcomputer 8 executes 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 detection circuit 6 detects the zero-cross of the focus error signal FE as follows. That is, with respect to 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, and the positive level of the focus error signal FE has a predetermined level. It is detected that a zero cross occurs when the threshold value + Vth is crossed. Regarding the absolute values of the threshold values −Vth and Vth, it is determined that the focus error signal FE is far away from near the zero level, and the focus error signal FE reaches sufficiently near the zero level from the relatively large absolute value level. A value that can be judged to have been set is set.

In step S5, the second zero-cross point Z
When C2 is detected, the microcomputer 8 causes the kick pulse FKP to fall (step S6). As a result, the jump pulse generation circuit 13 causes the output jump pulse FP to fall to the zero level, so that the adder 1
0 obtains an addition output of a level obtained by adding the zero level indicated by the jump pulse FP and the hold level supplied from the hold circuit 9, and thus the output level of the hold circuit 9. Accordingly, the focus actuator 30 has
The drive signal FD whose level has dropped sharply is supplied from the driver amplifier 17, but since there is a moment of inertia of drive due to the kick pulse FKP issued earlier, the focus actuator 30 reduces the speed of the reading light while reducing the speed. The displacement for moving the focal position to the target recording surface is continued.

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

When the third zero-cross point ZC3 is detected,
The microcomputer 8 raises the brake pulse FBP (step S8). As a result, the jump pulse generation circuit 13 further lowers the output jump pulse FP to the negative low level, so that the adder 10
The driver amplifier 17 is supplied with an addition output of a level obtained by adding the low level indicated by the jump pulse FP and the hold level output from the hold circuit 9. Along with this, the focus actuator 30 is supplied with a drive signal FD for stopping the movement of the reading light focusing position to the target recording surface until then, and the focus actuator 30 is
The displacement speed will be gradually reduced.

In the deceleration process of such an 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 detection of the fourth zero-cross point ZC4. The focus error signal FE increases in level as the focus of the reading light approaches the target recording surface from the position corresponding to the third zero-cross point ZC3, and after reaching the maximum value (see Vmax in FIG. 7), it changes again. Then, the level gradually decreases and the zero level is exhibited when the focus of the reading light has just reached the target recording surface. Therefore, the fourth zero-cross point ZC
4 will be detected.

When the fourth zero-cross point ZC4 is detected,
The microcomputer 8 lowers the brake pulse FBP (step S10) and jump status signal F
The 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. Further, the microcomputer 8 turns on the switch 11 and controls so that the focus error signal from the equalizer 7 is relayed to the driver amplifier 17 via the adder 10. Therefore, the focus actuator 30 will thereafter perform a steady focus servo operation that causes the focus position of the reading light to follow the target recording surface based on the focus error signal FE.

The microcomputer 8 carries out step S11.
It is determined whether or not a fixed time Tc has elapsed from the execution of (step S12). This fixed time Tc is the focus error signal F after the fourth zero-cross point ZC4 is detected.
As indicated by the symbol A in FIG. 7, E is set to a time slightly longer than the maximum time considered as the time until it converges near the zero level after overshooting. When the microcomputer 8 determines that the fixed time has elapsed, it sets the flag FRAG to 1 (step S1).
3).

Thus, the focus jump operation is completed, and the microcomputer 8 shifts to a mode for reproducing the recorded information on the target recording surface, for example. In addition to the focus jump operation, the microcomputer 8 performs a dropout compensation operation at every predetermined timing. In the dropout 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, the flag FRAG remains set to 1 in step S13 of the focus jump operation,
Since it is in the initial state, the focus jump operation is not performed. Therefore, the microcomputer 8 determines whether or not the dropout detection circuit 20 outputs the dropout detection signal (step S22). If the dropout detection signal is not output, this dropout compensation operation is immediately terminated. When the dropout detection signal is output, the FE hold signal is generated (step S23). The FE hold signal causes the on / off switch 11 of the hold circuit 9 to turn off, and the storage 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. The supply of the hold level of the hold circuit 9 to the adder 10 is
The process continues until it is determined in step S22 that the dropout detection signal is not output.

On the other hand, if the microcomputer 8 determines in step S21 that FRAG = 0, the flag F is set in step S2 of the focus jump operation.
RAG is set to 0, which means that the focus jump operation is in progress. 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 such 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 detected. Hold operation is prohibited. Therefore,
After the fourth zero-cross point ZC4 is detected, the focus error signal FE is retained by the dropout detection until the focus error signal FE overshoots and converges to near the zero level, as indicated by the symbol A in FIG. Is prohibited, so that a sufficient control amount can be obtained, the focus control operation can be prevented from becoming unstable, and the focus position can be rapidly converged on the target recording surface.

In the above-described embodiment, the fixed time Tc is the maximum time that can be considered after the fourth zero-cross point ZC4 is detected until the focus error signal FE overshoots and converges to near the 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. 9, the microcomputer 8 executes step S12.
If it is determined that the fixed time has passed in step S14, it is determined whether or not the dropout detection signal is generated (step S14), and it is confirmed that the dropout detection signal is not generated, and then the process proceeds to step S13. With flag FRA
Set 1 to G.

Further, although the two-layer optical disc has been described in the above embodiments, the present invention is not limited to this, and the present invention can be applied to a focus control device of a device for reproducing another multilayer optical recording medium including a multilayer optical disc having three or more layers. Can be applied. Furthermore, in the above-described embodiment, the dropout compensation operation is prohibited during the fixed time Tc, but the dropout compensation operation may be prevented by prohibiting the dropout detection operation.

[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. Therefore, the focus jump can be appropriately performed in the multilayer optical recording medium.

[Brief description of drawings]

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

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

FIG. 3 is a diagram showing an indefinite region of a focus error signal.

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

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

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

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

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

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

[Explanation of symbols for main parts]

1 2 layer optical disc 2 spindle motor 3 pickups 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

Continuation of front page (72) Inventor A. Bloodsho 1 25 Nishimachi, Yamada, Kawagoe, Saitama Prefecture Pioneer Co., Ltd., Kawagoe Factory (72) Inventor Hitoshi Yamazaki 1 25 Nishimachi, Yamada, Kawagoe City, Saitama Prefecture Pioneer, Kawagoe Factory (72) Inventor Kamo Kaname 25-1 Nishimachi, Yamada, Daigo, Kawagoe, Saitama Prefecture Pioneer Co., Ltd., Kawagoe Factory (72) Inventor Masakazu Takahashi 25, Nishimachi, Kawagoe, Saitama Prefecture, 1 Pioneer, Kawagoe Factory (56) Reference Documents JP-A-4-19871 (JP, A) JP-A-62-167626 (JP, A) JP-A-4-295631 (JP, A) JP-A-3-116450 (JP, A) JP-A-11- 7637 (JP, A) JP-A-4-265521 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B ^7/ 08-7/ ¹⁰ G11B ^7/ 00-7/013

Claims (7)

(57) [Claims] 1. A focus control device for a multi-layer optical recording medium, wherein focus servo is once released and the focus position of read light is moved to another target layer, and then the focus jump control is restarted. And a dropout detection unit that detects a decrease in the read signal due to the reading light, wherein the control unit detects the dropout for a predetermined time even after the focus servo is restarted 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 the means is prohibited. 2. A focus control device for a multi-layer optical recording medium, wherein focus servo is once released and the focus position of read light is moved to another target layer, and then the focus jump control is restarted. A dropout detecting means for detecting a dropout of a read signal due to the reading light; a dropout compensating means for performing a predetermined compensation process on a focus error signal according to the detection of the dropout;
A focus control device for a multilayer optical recording medium, wherein the control section prohibits the predetermined compensation processing by the dropout compensation means for a predetermined time even after the focus servo is restarted by the focus jump control. . 3. A focus control device for reproducing a recording medium having an information recording surface on each of at least two layers formed in a direction perpendicular to the surface, the recording medium being irradiated with reading light. In addition, the return light from the recording medium due to the reading light is received to generate a read signal indicating information recorded on the recording medium and a focus error signal indicating a focusing error of the reading light with respect to the information recording surface. Pickup means, zero-cross detection means for detecting zero-cross of the focus error signal, command means for generating a focus jump command, and the pickup means for focusing the reading light on an information recording surface according to the focus error signal. The focus servo operation that drives the focus actuator of the In response to the command, a jump drive operation is started for the focus actuator to move the focus position of the reading light from the recording surface of one of the at least two layers to the recording surface of the other layer, Driving means for stopping the jump drive operation and returning to the focus servo operation in response to a zero cross detection time point corresponding to the recording surface of the other layer by the zero cross detection means; Dropout detection means for generating a dropout detection signal when the dropout detection signal is present, dropout compensation means for holding the focus error signal immediately before the generation of the dropout detection signal and supplying the focus error signal to the drive means, At a predetermined time after the focus jump command is issued and after the jump drive operation of the drive means is stopped A focus control device for a multi-layer optical recording medium, comprising: a prohibition unit that prohibits the operation of the dropout detection unit or the dropout compensation unit until a lapse of time. 4. The predetermined time is a fixed time slightly longer than the maximum predicted time from the time of detection of a zero cross corresponding to the recording surface of the other layer until the focus error signal overshoots and converges near a zero level. The focus control device for a multilayer optical recording medium according to claim 3, wherein 5. The multilayer according to claim 3, wherein the prohibiting means releases the operation of the dropout compensating means when the dropout detection signal is not generated after the predetermined time has elapsed. Focus control device for optical recording medium. 6. The predetermined time is a fixed time slightly shorter than the maximum predicted time from the time of detection of a zero cross corresponding to the recording surface of the other layer until the focus error signal overshoots and converges near a zero level. The focus control device for a multilayer optical recording medium according to claim 5, wherein 7. The multi-layered light according to claim 3, wherein the dropout detection means generates the dropout detection signal when the peak level or the amplitude level of the read signal is lower than a threshold value. Focus control device for recording medium.