JP2000099955A - Method and device for focus control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly focus jump to an original recording layer prior to the occurrence of the out of focusing condition when an out of focusing occurred during a reproducing/recording of a multilayer optical disk having plural recording layers, to provide proper focusing and to restart reproducing/recording of the original recording layer. SOLUTION: An RF comparator 2 compares the levels of the envelope voltage of RF reproducing signals and a voltage value (a reference voltage VC) corresponding to the lower limit in the vicinity of a focused condition. A jump control section 3 computes the number of jumping over layers of the recording layers based on the frequencies, in which the voltage level of a focus error signal (an FE signal) exceeds the voltage value equivalent to the upper limit of the focused condition, and the frequencies in which the voltage level of the FE signal exceeds the voltage value equivalent to the lower limit of the focused condition. Then, based on the tilt of the waveforms of the FE signal when discrimination is made and determined that it is in the vicinity of a focused condition by the comparator 2, the direction of the out of focusing is detected and the focus jump is controlled based on the jumping layer number of the recording layers and the out of focusing direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus control method and a focus control apparatus applied to an optical information recording / reproducing apparatus for recording or reproducing a multi-layer optical disc having a plurality of recording layers.

[0002]

2. Description of the Related Art A focus control device provided in a conventional optical disk device will be described with reference to FIG.

[0003] As shown in FIG.
Was a single-layer optical disk. Therefore, the optical disk 51
When the focus is out of the recording layer, the servo of the track control section 68 for controlling the focus of the laser 69 to follow the track is turned off, and the focus control section 64 turns off the focus control for focusing on the recording layer.

Next, the objective lens 61 provided in the pickup device 62 is driven from bottom to top or from top to bottom. Then, a focus error signal (FE) is generated by a focus error signal generator 63 based on a signal from the pickup device 62, and when the laser 69 is focused on the recording layer, a focus control servo is performed by a focus controller 64. Is turned on to always focus the laser 69 on the recording layer.

Next, a track error signal generating section 67 generates a track error signal (TE) based on a signal from the pickup device 62, and when the focus of the laser 69 comes on the track, the track control section 68 The track servo is turned on so that the focus of the laser 69 always follows the track.

Then, based on the signal from the pickup device 62, an RF signal (RF) is generated by an RF reproduction signal generation section 65, and reproduction data is obtained by a reproduction data demodulation section 66.

By detecting the address of the track when the track is pulled in from the reproduced data at this time, the track controller 68 jumps the track to the address of the track at the time when the defocus occurs, and the defocus occurs. The reproduction data is obtained from the address of the track at the time of the reproduction.

In recent years, a multilayer optical disk having a plurality of recording layers has appeared on the market.
Discloses a focus control device for a multilayer optical disc.

[0009] The focus control device disclosed in the above-mentioned publication issues a focus error signal to a predetermined first and a second.
The focus error is detected by comparing with the reference voltage, the information of the recording layer that was controlled before the focus was lost is stored, and when the focus is lost and the other recording layer is focused, the focus is lost. By reproducing the recording layer information of the recording layer that is later focused, the current recording layer information is detected from the data of the recording layer, and the number of layers up to the original recording layer (the number of focus jumps)
Is calculated and a focus jump is performed to refocus the original recording layer.

[0010]

However, in the focus control apparatus for a single-layer optical disc having the above-mentioned conventional structure, when the focus is lost, the focus control is once turned off, and the objective lens 61 is moved upward from below. It takes time to drive from top to bottom. In addition, since the track control is turned off and on again, it takes a longer time.

Further, the focus control device disclosed in Japanese Patent Application Laid-Open No. Hei 8-185637 is effective only when the focus is out of focus and an arbitrary recording layer is in focus. If not, there is a problem that the focus cannot be returned to the original recording layer. In addition, since another recording layer is focused, an operation of reading out recording layer information of the recording layer and then re-focusing on the original recording layer is performed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a multi-layer optical disc having a plurality of recording layers, which is defocused during reproduction or recording. In the original recording layer before it came off,
It is an object of the present invention to provide a focus control method and a focus control device capable of quickly returning to the focus, returning the focus, and restarting reproduction / recording of the recording data of the recording layer before the defocus.

[0013]

According to a first aspect of the present invention, there is provided a focus control method for controlling a focus on a multilayer optical disc having a plurality of stacked recording layers. Detecting the focus state during recording or reproduction of the multi-layer optical disc, and when out of focus occurs, determines the number and direction of the jumping layers of the recording layer due to the out of focus based on the transition process of the focus state. Then, focus control is performed so as to return the focus to the original recording layer.

With the above arrangement, when a defocus occurs, the process of defocusing and flying can be detected, so that the direction of defocusing and the number of jumping layers of the recording layer can be detected. By performing a focus jump in the direction opposite to the direction moved by the defocus by the number of jump layers of the recording layer,
It is possible to refocus the original recording layer.

Therefore, even if the focus is deviated, the focus can be returned to the original recording layer without reproducing the recording layer information of the recording layer to which the flying has been performed. Further, even when the focus deviates from the recording layer and no focus is achieved on any of the recording layers, the number of moved layers can be counted and the position where the focus is in focus can be detected. Focus can be returned to the layer.

Therefore, when the focus is lost during reproduction or recording of the multilayer optical disk, the focus can be quickly returned to the original recording layer, and the reproduction or recording of the recording data of the original recording layer can be quickly resumed. it can.

According to a second aspect of the present invention, in order to solve the above-mentioned problem, in addition to the first aspect, the voltage level of the focus error signal is a voltage value corresponding to an upper limit of a focused state. Calculating the number of skipping layers of the recording layer based on the number of times the first focus error reference voltage is equal to or higher and the number of times that the second focus error reference voltage is equal to or lower than a voltage value corresponding to the lower limit of the focused state; And the slope of the waveform of the focus error signal when the level of the envelope voltage of the RF reproduction signal when the out-of-focus occurs becomes equal to or higher than the RF reference voltage which is the voltage value corresponding to the lower limit of the state near the focused state. And detecting the out-of-focus direction on the basis of

According to the above configuration, in addition to the operation of the configuration of the first aspect, an S-shaped waveform of a focus error signal that is generated one by one when a defocus occurs and the focal point of the laser jumps over each recording layer. By detecting the inclination of each recording layer in the vicinity of the focal point, that is, rising or falling, it is possible to determine whether the direction of defocus, that is, whether the moving direction of the laser focus is upward or downward. Can be.

Further, the S-shaped waveform of the focus error signal is compared with the first focus error reference voltage and the second focus error reference voltage, and the number of S-shaped waveforms exceeding these is added or subtracted in each direction. Thus, the number of skipped layers from the original recording layer can be detected.

At this time, if the number of jump layers obtained by comparing with the first focus error reference voltage does not match the number of jump layers obtained by comparing with the second focus error reference voltage, the focus is on the recording layer. Do not match, and the focal point is located between the recording layers, or in a region further above the uppermost layer of the multilayer recording layer or in a region further below the lowermost layer. In this case, there is a focus between the layer having the minimum number of jump layers obtained by comparison with the first focus error reference voltage and the second focus error reference voltage, and the next layer. , The moving position from the original recording layer can be detected.

Therefore, by performing the focus jump in the direction opposite to the direction moved by the defocus by the calculated number of jump layers, it is possible to refocus the original recording layer.

According to a third aspect of the present invention, there is provided a focus control apparatus for controlling a focus on a multilayer optical disc having a plurality of stacked recording layers. The focus state is detected during recording or playback, and when out of focus occurs, the number of jumping layers of the recording layer due to the out of focus and the direction thereof are determined based on the transition process of the focus state, and the focus is restored. And a control unit for performing focus control so as to return to the recording layer.

With the above arrangement, in the above-mentioned focus control device, when out-of-focus occurs, the process of out-of-focus and flying is detected to detect the out-of-focus direction and the number of jumping layers of the recording layer. Can be. Then, by performing a focus jump in the direction opposite to the direction moved by the defocus by the number of jump layers of the recording layer, it is possible to refocus the original recording layer.

Therefore, even if the focus is lost, the focus can be returned to the original recording layer without reproducing the recording layer information of the recording layer to which the flying has been performed. Further, even when the focus deviates from the recording layer and no focus is achieved on any of the recording layers, the number of moved layers can be counted and the position where the focus is in focus can be detected. Focus can be returned to the layer.

Therefore, when the focus is lost during reproduction or recording of the multilayer optical disc, the focus can be quickly returned to the original recording layer, and the reproduction or recording of the recording data of the original recording layer can be resumed quickly. it can.

According to a fourth aspect of the present invention, in order to solve the above-mentioned problem, in addition to the configuration of the third aspect, the control means further comprises: an envelope voltage of the RF reproduction signal; An RF comparator that compares the level with an RF reference voltage that is a voltage value corresponding to a lower limit, and a voltage level of a focus error signal becomes equal to or higher than a first focus error reference voltage that is a voltage value corresponding to an upper limit of a focused state. The number of times and a second voltage value corresponding to the lower limit of the focused state.
The number of skipping layers of the recording layer is calculated based on the number of times the focus error signal becomes equal to or lower than the reference voltage, and the focus error signal of the focus error signal when it is determined by the RF comparator that it is in the vicinity of the focused state. A jump control unit that detects a direction of out-of-focus based on the slope of the waveform, and controls a focus jump based on the number of jump layers of the recording layers and the direction of out-of-focus. .

According to the above construction, in addition to the operation of the construction of claim 3, an S-shaped waveform of a focus error signal which is generated one by one when defocus occurs and the laser focus jumps over each recording layer. By detecting the inclination of each recording layer in the vicinity of the focal point, that is, rising or falling, it is possible to determine whether the direction of defocus, that is, whether the moving direction of the laser focus is upward or downward. Can be.

Further, the S-shaped waveform of the focus error signal is compared with the first focus error reference voltage and the second focus error reference voltage, and the number of S-shaped waveforms exceeding these is added and subtracted in each direction. Thus, the number of skipped layers from the original recording layer can be detected.

At this time, if the number of jump layers obtained by comparing with the first focus error reference voltage does not match the number of jump layers obtained by comparing with the second focus error reference voltage, the focus is on the recording layer. Do not match, and the focal point is located between the recording layers, or in a region further above the uppermost layer of the multilayer recording layer or in a region further below the lowermost layer. In this case, there is a focus between the layer having the minimum number of jump layers obtained by comparison with the first focus error reference voltage and the second focus error reference voltage, and the next layer. , The moving position from the original recording layer can be detected.

Therefore, by performing the focus jump in the direction opposite to the direction moved by the defocus by the calculated number of jump layers, it is possible to refocus the original recording layer.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] The following will describe one embodiment of the present invention with reference to FIGS.

The focus control device according to the present embodiment is provided in an optical information recording / reproducing device for recording or reproducing a multi-layer optical disc having a plurality of recording layers. When out of focus occurs, the number and direction of the skipped recording layers are determined, and focus control is performed so as to return to the recording layer before the out of focus.

As shown in FIG. 1, the focus control device according to the present embodiment includes an A / D converter 1, an RF comparator 2, a jump control unit 3, a jump drive unit 4, and a switching unit 5. It is configured. Note that the RF comparator 2 and the jump control unit 3 constitute control means.

The A / D converter 1 outputs an analog focus error signal (hereinafter referred to as "FE signal") (F).
E) is sampled and converted into a digital signal p1.

The RF comparator 2 compares the envelope voltage of the RF signal (RF) with a reference voltage (RF reference voltage) VC which is a voltage value corresponding to the lower limit of the state near the focused state. Is high when the envelope voltage level is higher than the reference voltage VC, and is low when the envelope voltage level is lower than the reference voltage VC.
Is output to the jump control unit 3. That is, the RF comparator 2 outputs the signal p2 of H when the laser 7 (described later) is near the focal point of an arbitrary recording layer, and outputs the signal p2 of L when it is between the recording layers.

The jump control unit 3 includes an A / D converter 1
And the signal p1 obtained by sampling the FE signal at
Based on the signal p2 from the comparator 2, the number and direction of out-of-focus layers are detected, and the number and direction of focus jump layers for returning to the original recording layer are calculated.
To the jump driving unit 4 and the switching unit 5. The jump control unit 3 can be constituted by, for example, a CPU.

The jump driving section 4 generates a pulse for driving the focus jump based on the information on the number of layers and the direction of the focus jump inputted as the signal p3 from the jump control section 3, and outputs the switching section 5 as the signal p4. Output to

The switching section 5 inputs the FE signal to the focus driver during reproduction or recording of the multi-layer optical disc based on the signal p3 of the jump control section 3, while the out-of-focus occurs and returns to the original recording layer. When the focus jump is performed to return, a signal p4 from the jump driving means 4 is switched to be output to the focus driver.

FIG. 2 shows an example of a multi-layer optical disc which is recorded and reproduced by the optical information recording and reproducing apparatus according to the present embodiment.

Four-layer optical disk (multi-layer optical disk) 21
Are the first recording layer (recording layer) 2 in order from the objective lens 6 side.
1a (first layer), second recording layer (recording layer) 21b (second layer)
), A third recording layer (recording layer) 21c (third layer), and a fourth recording layer (recording layer) 21d (fourth layer). FIG. 2 shows a state where the laser 7 is irradiated by the objective lens 6 and the first recording layer 21a is focused.

Hereinafter, the operation of the focus control apparatus according to the present embodiment will be described with reference to FIGS. 3 to 7 for the following three cases. [1] From the state in which the focus is on the first layer, fly two layers upward by vibration or the like, and focus on the third layer (FIG. 5). [2] Focus on the third layer When two layers fly down by vibration or the like from the state in which they have moved, and have passed the first layer and returned to the first layer (FIG. 6) [3] The state in which the focus is on the fourth layer When the camera flies upward due to vibration or the like, and becomes out of focus (FIG. 7)

[1] From the state where the focus is on the first recording layer 21a, two layers fly upward and focus on the third recording layer 21c.
It moves as shown in FIG.

With the movement of the objective lens 6, the voltage VFE of the FE signal and the envelope voltage of the RF signal change as follows.

As shown in FIG. 5B, the voltage VFE of the FE signal varies between the focal point of the first recording layer 21a and the second recording layer 21a.
An S-shaped waveform is drawn between the focal point b and the focal point of the second recording layer 21b and the focal point of the third recording layer 21c. That is, due to the movement of the objective lens 6, the voltage VFE of the FE signal draws two S shapes.

As shown in FIG. 5C, the envelope voltage of the RF signal has a waveform which becomes maximum near the focal point of the first recording layer 21a, the second recording layer 21b, and the third recording layer 21c. Draw.

Then, the RF comparator 2 compares the envelope voltage of the RF signal with the reference voltage VC, and outputs an H signal when the envelope voltage level of the RF signal is higher than the reference voltage VC, and an L signal when the envelope voltage level is lower than the reference voltage VC. p2 is output to the jump control unit 3.

That is, as shown in FIG. 5D, the output of the RF comparator 2 is transmitted from the laser 7 to the recording layer (the first recording layer 21).
a, H when near the focal point of the second recording layer 21b and the third recording layer 21c), between the recording layers (the first recording layer 21a and the second recording layer 21b, the second L is between the recording layer 21b and the third recording layer 21c).

Next, the operation of performing focus control in the above state will be described with reference to the flowcharts of FIGS. The following control operation is performed by the jump control unit 3
Done by

First, the upper pulse counter U, the lower pulse counter D, and the timer M are reset (S0).

Next, it is determined whether the timer M has exceeded the invariable time T of the focus error signal (S1). Here, since the timer M is reset and does not exceed the invariable time T of the focus error signal (NO),
Proceed to step S2.

The non-change time T of the focus error signal is determined in advance by an experiment. The method of determining the non-change time T of the focus error signal is set to be equal to or longer than the cycle of the S-shaped waveform of the last FE signal when the focus is lost due to vibration or the like. For example, it is set to twice the period of the S-shaped waveform of the last FE signal when the focus is lost.

Then, the FE signal is sampled by the A / D converter 1, and its voltage (FE voltage VFE) is measured by the jump control unit 3 (S2).

In step S2, when no defocus has occurred, the FE voltage VFE is between the reference voltage (first focus error reference voltage) VA and the reference voltage (second focus error reference voltage) VB (reference voltage VB ≦ F
E voltage VFE ≦ reference voltage VA). Then, in this case, the process returns to step S1 without doing anything.

The reference voltage VA is a voltage value corresponding to the upper limit of the focused state. The reference voltage VB is a voltage that is a voltage value corresponding to the lower limit of the focused state. Reference voltage V
C is a voltage value corresponding to the lower limit of the state near the focused state. And how to determine the reference voltages VA, VB, VC is
It is as follows. The reference voltage VA is between the in-focus level of the FE signal and the peak voltage of the upper amplitude, for example,
1/0 between the in-focus level and the peak voltage of the upper amplitude
The voltage of 4 is set to the level of the value added to the in-focus level. The reference voltage VB is obtained by subtracting a quarter of the voltage from the in-focus level of the FE signal to the lower amplitude bottom voltage, for example, from the in-focus level to the lower amplitude bottom voltage, from the in-focus level. Set to the level of the value. Reference voltage V
C is R at the level of the reference voltages VA and VB of the FE signal.
RF when the FE signal is equal to or lower than the F envelope voltage and the FE signal is a peak voltage having an upper amplitude and a bottom voltage having a lower amplitude.
Set to a voltage value equal to or higher than the envelope voltage.

On the other hand, when the focus is deviated upward in step S2, the FE voltage VFE exceeds the reference voltage VA (FE voltage VFE> reference voltage VFE).
A). Then, in this case, the process proceeds to step S3. Also,
When the focus is shifted downward, the FE voltage VFE becomes lower than the reference voltage VB (FE voltage VFE <reference voltage VFE).
B). Then, in this case, the process proceeds to step S8.

Here, the focus is on the first recording layer 21a.
Because it is flying upward from the state that matches
If the voltage VFE exceeds the reference voltage VA, step S3
Proceed to.

Then, the timer M is reset (S
3). Subsequently, the timer M is started (S4).

Further, the region where the output of the RF comparator 2 is H,
That is, the jump controller 3 detects the rising edge of the FE signal from the sample value of the FE signal near the focal point of the first recording layer 21a (between t1 and t2) (S
5). Here, if it is determined that the focus is out of focus (rise), the process proceeds to step S6, and if it is determined that the focus is out of focus (fall), the process proceeds to step S7.

Here, the focus is on the first recording layer 21a.
Since the airplane is flying upward from the state of (2), the counter U of the upper pulse is counted up by one (S6).

Then, the process proceeds to a step S12A. The FE signal is sampled by the A / D converter 1 and its voltage (FE
The voltage VEF) is measured by the jump control unit 3. While the FE voltage VEF exceeds the reference voltage VA, step S1
Repeat 2A. The FE voltage VFE is equal to the reference voltage V
If it becomes less than A, the process returns to step S1. When the timer M does not exceed the invariable time T of the focus error signal (S1 (NO)), the FE voltage VFE is measured (S1).
2) When the FE voltage VFE becomes lower than the reference voltage VB (VFE <VB), the timer M is reset (S8),
The timer M is started (S9).

Further, the region where the output of the RF comparator 2 is H,
That is, the jump control unit 3 detects the rising of the gradient of the FE signal from the sample value of the FE signal near the focal point (between t3 and t4) of the second recording layer 21b (S
5). That is, it is determined that the focus is out of focus (rising) (S10), and the counter D of the lower pulse is counted up by one (S11).

Then, the process proceeds to a step S12A. The FE signal is sampled by the A / D converter 1 and its voltage (FE
The voltage VEF) is measured by the jump control unit 3. And
Since the FE voltage VFE is higher than the reference voltage VB,
It returns to step S1.

The same operation is performed until the third recording layer 21c is focused, and then when the timer M exceeds the invariable time T of the focus error signal (S1 (YE
S)), and proceed to A (FIG. 4).

At this point, the upper pulse counter U = +
2, the lower pulse counter D = + 2. That is, as shown in FIG. 5 (e), from time t1 to time t2
, The counter U of the upper pulse is incremented by 1, and the counter D of the lower pulse is incremented by 1 between time t3 and time t4.
Between time t5 and time t6, the upper pulse counter U is further incremented by one, and between time t7 and time t8, the lower pulse counter D is incremented by one. Therefore, the counter U of the upper pulse and the counter D of the lower pulse are both the number of layers of the difference between the original recording layer and the current recording layer, and the direction is +
Therefore, it can be determined that the focus is deviated upward by two layers.

Proceeding to step S13 in FIG. 4, | UD |
Since = 0, the sign of U is determined (S14). Since U is positive, the objective lens 6 performs a focus jump downward by | U | layer, and returns to the original recording layer (S15).

Thereafter, a track jump is made to the track where the reproduction data is interrupted (S20), and data reproduction is resumed (S21).

[2] When the focus is on the third recording layer 21c, it jumps two layers downward, passes through the first recording layer 21a and returns again, and is focused on the first recording layer 21a. In this case, the objective lens 6 moves as shown in FIG.

With the movement of the objective lens 6, the voltage VFE of the FE signal and the envelope voltage of the RF signal change as follows.

As shown in FIG. 6B, the voltage VFE of the FE signal varies between the focal point of the third recording layer 21c and the second recording layer 21c.
After drawing an S-shaped waveform between the focal point b and the focal point of the second recording layer 21b and the focal point of the first recording layer 21a, two lower pulses are generated.

As shown in FIG. 6C, the envelope voltage of the RF signal is such that the envelope voltage becomes maximum near the focal point of the third recording layer 21c, the second recording layer 21b, and the first recording layer 21a. Draw.

Then, as shown in FIG. 6D, the output of the RF comparator 2 is transmitted from the laser 7 to the recording layer (the first recording layer 21).
a, H when near the focal point of the second recording layer 21b and the third recording layer 21c), between the recording layers (the third recording layer 21c and the second recording layer 21b, the second (Between the recording layer 21b and the first recording layer 21a, below the first recording layer 21a)
When it is at L.

Next, the operation of performing focus control in the above state will be described with reference to the flowcharts of FIGS.

First, the upper pulse counter U, the lower pulse counter D, and the timer M are reset (S0).

Next, it is determined whether or not the timer M has exceeded the non-change time T of the focus error signal (S1). Here, since the timer M is reset and does not exceed the invariable time T of the focus error signal (NO),
Proceed to step S2.

Then, the FE signal is sampled by the A / D converter 1, and its voltage (FE voltage VFE) is measured by the jump control unit 3 (S2).

In step S2, if no defocus has occurred, the FE voltage VFE is changed to the reference voltage VA.
And reference voltage VB (reference voltage VB ≦ FE voltage VFE ≦
Reference voltage VA). Then, in this case, the process returns to step S1 without doing anything.

On the other hand, when the focus is shifted downward in step S2, the FE voltage VFE becomes lower than the reference voltage VB (FE voltage VFE <reference voltage VFE).
B). Then, in this case, the process proceeds to step S8.

Here, the focus is on the third recording layer 21c.
Because it is flying downward from the state that fits,
Voltage VFE becomes lower than reference voltage VB, and the process proceeds to step S8.

Then, the timer M is reset (S
8). Subsequently, the timer M is started (S9).

Further, the area where the output of the RF comparator 2 is H,
That is, the vicinity of the focal point of the third recording layer 21c (from t9 to t10)
The jump controller 3 detects the falling edge of the FE signal from the sample value of the FE signal during the period (S1) (S1).
0). Here, if it is determined that the focus is out of focus (rise), the process proceeds to step S11. If it is determined that the focus is out of focus (fall), the process proceeds to step S12.

Here, the focus is on the third recording layer 21c.
, Since it is flying downward, the counter D of the lower pulse is counted down by one (S1).
2).

Then, the process proceeds to a step S12A. The FE signal is sampled by the A / D converter 1 and its voltage (FE
The voltage VEF) is measured by the jump control unit 3. Step S12A is repeated while the FE voltage VEF is lower than the reference voltage VB. When the FE voltage VFE becomes equal to or higher than the reference voltage VB, the process returns to step S1. When the timer M does not exceed the invariable time T of the focus error signal (S
1 (NO)), the FE voltage VFE is measured (S2), and the FE
When the voltage VFE exceeds VA (VFE> VA), the timer M is reset (S3), and the timer M is started (S4).

Further, the jump controller 3 sets the slope of the FE signal from the region where the RF comparator output is H, that is, the sample value of the FE signal in the vicinity of the focal point of the second recording layer 21b (between t11 and t12). Detect falling (S
5). That is, it is determined that the focus is shifted downward (falling) in the downward direction (S5), and the counter U of the upper pulse is counted down by one (S7).

Then, the process proceeds to a step S12A. The FE signal is sampled by the A / D converter 1 and its voltage (FE
The voltage VEF) is measured by the jump control unit 3. And
Since the FE voltage VFE is lower than the reference voltage VA,
It returns to step S1.

Similarly, the counter U for the upper pulse and the counter D for the lower pulse sequentially count down in the order of the second recording layer 21b and the first recording layer 21a.
2. Counter D = -2.

Further, when passing through the first recording layer 21a (between t17 and t18), that is, the first recording layer 21a
FE voltage VFE becomes lower than VB (S2 (VFE <VB)) and the slope falls (S10 (fall)), the counter D of the lower pulse is counted down (S12) and the lower pulse Counter D =
-3.

However, since the focus has returned to the first recording layer 21a, the first recording layer 21a between t19 and t20.
FE voltage VFE is lower than VB (S2 (VFE <VB)) and the slope rises (S10 (rising)) near the focal point of (2), so that the counter D of the lower pulse is counted up (S11), and the counter D = -2.

When the timer M exceeds the non-change time T of the focus error signal (S1 (YES)), A
Proceed to (FIG. 4).

At this point, the upper pulse counter U = −
2. The lower pulse counter D = -2. That is, as shown in FIG. 6E, from time t9 to time t1
Between 0, the counter D of the lower pulse is decremented by 1 and the time t1
From 1 to time t12, the upper pulse counter U is decremented by one, and from time t13 to time t14, the lower pulse counter D is further decremented by one, and from time t15 to time t16
In between, the counter U of the upper pulse is further decremented by one. Thereafter, the counter D of the lower pulse is decremented by 1 between time t17 and time t18, but from time t19 to time t
One is added between 20. Therefore, the counter U for the upper pulse and the counter D for the lower pulse are both the number of layers of the difference between the original recording layer and the current recording layer, and the direction is-, so that the focus is shifted downward by two layers. You can judge that it is off.

Going to step S13 in FIG. 4, | UD |
Since = 0, the sign of U is determined (S14). Since U is negative, focus jump of the objective lens 6 upward by | U | layer is performed, and the original recording layer is returned (S16).

Thereafter, a track jump is performed to the track where the reproduced data is interrupted (S20), and data reproduction is resumed (S21).

[3] When the focus is on the fourth recording layer 21d and the focus jumps upward and becomes out of focus, the objective lens 6 is moved to the state shown in FIG.
Move as shown.

With the movement of the objective lens 6, the voltage VFE of the FE signal and the envelope voltage of the RF signal change as follows.

As shown in FIG. 7B, the voltage VFE of the FE signal draws one upper pulse.

Further, as shown in FIG. 7C, the envelope voltage of the RF signal draws a waveform which is maximum near the focal point of the fourth recording layer 21d and becomes smaller thereafter.

Then, the RF comparator 2 compares the envelope voltage of the RF signal with the reference voltage VC, and outputs an H signal when the envelope voltage level of the RF signal is higher than the reference voltage VC, and an L signal when the envelope voltage level is lower than the reference voltage VC. p2 is output to the jump control unit 3.

That is, as shown in FIG. 7D, the output of the RF comparator 2 is transmitted from the laser 7 to the recording layer (the fourth recording layer 21).
When the focus is in the vicinity of the focal point of d), H is set, and when the focus is lost thereafter, L is set.

Next, the operation of performing focus control in the above state will be described with reference to the flowcharts of FIGS.

First, the counter U for the upper pulse, the counter D for the lower pulse, and the timer M are reset (S0).

Next, it is determined whether the timer M has exceeded the invariable time T of the focus error signal (S1). Here, since the timer M is reset and does not exceed the invariable time T of the focus error signal (NO),
Proceed to step S2.

Then, the FE signal is sampled by the A / D converter 1, and its voltage (FE voltage VFE) is measured by the jump control section 3 (S2).

In step S2, when no defocus has occurred, the FE voltage VFE is changed to the reference voltage VA.
And reference voltage VB (reference voltage VB ≦ FE voltage VFE ≦
Reference voltage VA). Then, in this case, the process returns to step S1 without doing anything.

On the other hand, when the focus is deviated upward in step S2, the FE voltage VFE exceeds the reference voltage VA (FE voltage VFE> reference voltage VFE).
A). Then, in this case, the process proceeds to step S3.

Here, the focus is on the fourth recording layer 21d.
Because it is flying upward from the state that matches
If the voltage VFE exceeds the reference voltage VA, step S3
Proceed to.

Then, the timer M is reset (S
3). Subsequently, the timer M is started (S4).

Further, the output of the RF comparator 2 is in the H range,
That is, the vicinity of the focal point of the fourth recording layer 21d (from t21 to t2)
2), the jump control unit 3 detects the rising edge of the FE signal from the sample value of the FE signal (S2).
5). When it is determined that the focus is out of focus (rising), the process proceeds to step S6, and when it is determined that the focus is out of focus (fall), the process proceeds to step S7.

Here, the focus is on the fourth recording layer 21d.
Since the airplane is flying upward from the state of (2), the counter U of the upper pulse is counted up by one (S6).

Then, the process proceeds to a step S12A. The FE signal is sampled by the A / D converter 1 and its voltage (FE
The voltage VEF) is measured by the jump control unit 3. While the FE voltage VEF exceeds the reference voltage VA, step S1
Repeat 2A. The FE voltage VFE is equal to the reference voltage V
If it becomes less than A, the process returns to step S1. Since the timer M exceeds the non-change time T of the focus error signal without focusing (S1 (YES)), A (FIG. 4)
Proceed to.

At this point, the upper pulse counter U = +
1, the lower pulse counter D = 0. That is, as shown in FIG. 6E, from time t21 to time t
The counter U of the upper pulse is incremented by 1 during the period 22.

Proceeding to step S13 in FIG. 4, | UD |
= 1, it is determined whether U or D is positive or negative (S1
7). Since U is positive, the objective lens 6 is moved downward, | U |
And focus jump to the minimum value of | D | by +0.5 layers, and return to the original recording layer (S18). If the out-of-focus occurs in the downward direction and the focus remains out of focus, the counter U or the counter D becomes negative (S17), and the minimum value 0 of | U | and | D | The focus jumps upward by the number of layers, and returns to the original recording layer (S19).

Thereafter, a track jump is performed to the track where the reproduction data is interrupted (S20), and data reproduction is resumed (S21).

As described above, the focus control device according to the present embodiment includes four stacked recording layers 21a to 21a.
1d is a focus control device for controlling the focus on the four-layer optical disc 21 having the focus state during recording or reproduction of the four-layer optical disc 21, and when the out-of-focus state occurs, the focus state is detected. Based on the transition process, the number of jumping layers of the recording layer due to defocus and the direction thereof are determined, and focus control is performed so as to return the focus to the original recording layer.

Thus, in the above-mentioned focus control device, when the out-of-focus state occurs, the process of the out-of-focus state and the flying process can be detected, so that the direction of the out-of-focus state and the number of jumping layers of the recording layer can be detected. . Then, by performing a focus jump in the direction opposite to the direction moved by the out-of-focus by the number of jumping layers of the recording layer, it is possible to refocus the original recording layer.

Therefore, even if the focus is lost, it is possible to return the focus to the original recording layer without reproducing the recording layer information of the recording layer to which the recording has been skipped. Further, even when the focus deviates from the recording layer and no focus is achieved on any of the recording layers, the number of moved layers can be counted and the position where the focus is in focus can be detected. Focus can be returned to the layer.

Therefore, when the focus is lost during the reproduction or recording of the multilayer optical disc, the focus can be quickly returned to the original recording layer, and the reproduction or the recording of the recording data of the original recording layer can be quickly restarted. it can.

Further, the focus control device according to the present embodiment controls the envelope voltage of the RF reproduction signal and the RF reference voltage VC, which is the voltage value corresponding to the lower limit of the state near the focused state, as the control means. The RF comparator 2 to be compared, the number of times the voltage level of the FE voltage VFE becomes equal to or higher than the first focus error reference voltage VA which is a voltage value corresponding to the upper limit of the focused state, and the voltage corresponding to the lower limit of the focused state The number of skipping layers of the recording layer is calculated based on the number of times that the value becomes equal to or less than the second focus error reference voltage VB, which is the value. The direction of out-of-focus is detected based on the gradient of the waveform of the FE signal, and the focus position is determined based on the number of skipping layers of these recording layers and the direction of out-of-focus. And a jump control unit 3 for controlling the pump.

As a result, an out-of-focus occurs, and the slope of the S-shaped waveform of the focus error signal generated one by one when the laser focus jumps over each recording layer near the focal point of each recording layer, ie, By detecting rising or falling, it is possible to determine the out-of-focus direction, that is, whether the focus of the laser is moving upward or downward.

The S-shaped waveform of the focus error signal is compared with the first focus error reference voltage VA and the second focus error reference voltage VB, and the number of S-shaped waveforms exceeding the reference voltages VA and VB is determined in the direction. By separately performing addition and subtraction, the number of skipped layers from the original recording layer can be detected.

At this time, if the number of jump layers obtained by comparing with the first focus error reference voltage VA does not match the number of jump layers obtained by comparing with the second focus error reference voltage VB, the recording layer Focus on the area between the recording layers or between the recording layers, or above the top layer of the multilayer recording layer or below the bottom layer. Become. In this case, there is a focus between the layer having the minimum number of jump layers obtained by comparison with the reference voltage VA and the reference voltage VB, and the next layer. Can be detected.

Therefore, by performing a focus jump by the calculated number of jump layers in the direction opposite to the direction of the movement due to the defocus, it is possible to refocus the original recording layer.

The present embodiment does not limit the scope of the present invention, and various changes can be made within the scope of the present invention. That is, in the above-described embodiment, the focus control device according to the present invention has been described as an optical disk reproducing device, but this may be applied to, for example, an optical disk recording device or an optical disk recording and reproducing device. The optical disk may be another optical disk such as an optical disk or a magneto-optical disk in which recording data is formed in a pit shape in advance, as long as the optical disk has a multilayer structure.

[0122]

As described above, the focus control method according to the first aspect of the present invention is a focus control method for controlling the focus on a multilayer optical disc having a plurality of stacked recording layers. The focus state is detected during recording or playback, and when out of focus occurs, the number of jumping layers of the recording layer due to the out of focus and the direction thereof are determined based on the transition process of the focus state, and the focus is restored. Focus control so as to return to the recording layer.

Therefore, even if the focus is deviated, the focus can be returned to the original recording layer without reproducing the recording layer information of the recording layer to which the flying has been performed. Further, even when the focus deviates from the recording layer and no focus is achieved on any of the recording layers, the number of moved layers can be counted and the position where the focus is in focus can be detected. Focus can be returned to the layer.

Therefore, when the focus is lost during reproduction or recording of the multilayer optical disc, the focus can be quickly returned to the original recording layer, and the reproduction or recording of the recording data of the original recording layer can be quickly restarted. It has the effect of being able to.

A focus control method according to a second aspect of the present invention
As described above, in addition to the configuration of claim 1, the number of times the voltage level of the focus error signal becomes equal to or higher than the first focus error reference voltage which is a voltage value corresponding to the upper limit of the focused state, and The second voltage value corresponding to the lower limit
Calculating the number of skipping layers of the recording layer based on the number of times the focus error reference voltage or less, and when the level of the envelope voltage of the RF reproduction signal when out of focus occurs, the level of the envelope voltage near the in-focus state Detecting the out-of-focus direction based on the gradient of the waveform of the focus error signal when the voltage becomes equal to or higher than the RF reference voltage which is the voltage value corresponding to the lower limit.

Therefore, in addition to the effect of the configuration of claim 1, each of the S-shaped waveforms of the focus error signal generated one by one when the defocus occurs and the laser focus jumps over each recording layer. By detecting the inclination of the recording layer near the focal point, that is, rising or falling, it is possible to determine whether the direction of defocus, that is, whether the direction of movement of the laser focus is upward or downward. .

The S-shaped waveform of the focus error signal is compared with the first focus error reference voltage VA and the second focus error reference voltage VB, and the number of S-shaped waveforms exceeding the reference voltages VA and VB is determined in the direction. By separately performing addition and subtraction, the number of skipped layers from the original recording layer can be detected.

Therefore, by performing a focus jump by the calculated number of jump layers in a direction opposite to the direction in which the focus layer has moved due to the out-of-focus state, it is possible to refocus the original recording layer.

A focus control device according to a third aspect of the present invention
As described above, a focus control device that controls focus on a multilayer optical disc having a plurality of stacked recording layers, detects a focus state during recording or reproduction of the multilayer optical disc, and detects a defocus. When it occurs, the control unit performs a focus control so as to determine the number of skipped layers and the direction of the recording layer due to the defocus based on the transition process of the focus state based on the transition process of the focus state and to return the focus to the original recording layer. is there.

Therefore, even if the focus is out of focus, the focus can be returned to the original recording layer without reproducing the recording layer information of the recording layer to which the flying has been performed. Further, even when the focus deviates from the recording layer and no focus is achieved on any of the recording layers, the number of moved layers can be counted and the position where the focus is in focus can be detected. Focus can be returned to the layer.

Therefore, when the focus is lost during reproduction or recording of the multilayer optical disc, the focus can be quickly returned to the original recording layer, and the reproduction or recording of the recording data of the original recording layer can be quickly resumed. It has the effect of being able to.

A focus control device according to a fourth aspect of the present invention
As described above, in addition to the configuration of the third aspect, the control unit compares the level of the envelope voltage of the RF reproduction signal with the level of the RF reference voltage that is a voltage value corresponding to the lower limit of the state near the focused state. The RF comparator and the number of times that the voltage level of the focus error signal becomes equal to or higher than a first focus error reference voltage which is a voltage value corresponding to the upper limit of the focused state;
The number of jumping layers of the recording layer is calculated based on the number of times the voltage falls below the second focus error reference voltage, which is the voltage value corresponding to the lower limit of the focused state, and the RF comparator is used to calculate the number of layers in the vicinity of the focused state. Based on the slope of the waveform of the focus error signal when it is determined that
It is configured to include a jump control unit that detects a direction of out-of-focus and controls a focus jump based on the number of jump layers of these recording layers and the direction of out-of-focus.

Therefore, in addition to the effect of the configuration of claim 3, each of the S-shaped waveforms of the focus error signal generated one by one when the defocus occurs and the focus of the laser jumps over each recording layer. By detecting the inclination of the recording layer near the focal point, that is, rising or falling, it is possible to determine whether the direction of defocus, that is, whether the direction of movement of the laser focus is upward or downward. .

Also, the S-shaped waveform of the focus error signal is compared with the first focus error reference voltage VA and the second focus error reference voltage VB, and the number of S-shaped waveforms exceeding the reference voltages VA and VB is determined in the direction. By separately performing addition and subtraction, the number of skipped layers from the original recording layer can be detected.

Therefore, by performing a focus jump by the calculated number of jump layers in the direction opposite to the direction in which the focus has moved out of focus, it is possible to refocus the original recording layer.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically showing a configuration of a focus control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram schematically showing a configuration of a four-layer optical disc which is recorded or reproduced by an optical information recording / reproducing apparatus including the focus control device shown in FIG.

FIG. 3 is a first half of a flowchart for explaining the operation of the focus control device shown in FIG. 1;

FIG. 4 is a flowchart illustrating the operation of the focus control device shown in FIG. 1, and is a latter half of the flowchart shown in FIG. 3;

5A and 5B are explanatory diagrams of the operation of the focus control device shown in FIG. 1, wherein FIG. 5A is an explanatory diagram showing a movement position of an objective lens, and FIG. 5B is a waveform diagram of a voltage level of an FE signal; (C) is a waveform diagram of the envelope voltage of the RF signal, (d) is a waveform diagram of the output signal of the RF comparator, and (e) is a diagram illustrating a change in the counter value counted by the jump control unit. FIG.

6A and 6B are explanatory diagrams of the operation of the focus control device shown in FIG. 1; FIG. 6A is an explanatory diagram showing a moving position of an objective lens; FIG. 6B is a waveform diagram of a voltage level of an FE signal; (C) is a waveform diagram of the envelope voltage of the RF signal, (d) is a waveform diagram of the output signal of the RF comparator, and (e) is a diagram illustrating a change in the counter value counted by the jump control unit. FIG.

7A and 7B are explanatory diagrams of the operation of the focus control device shown in FIG. 1; FIG. 7A is an explanatory diagram showing a moving position of an objective lens; FIG. 7B is a waveform diagram of a voltage level of an FE signal; (C) is a waveform diagram of the envelope voltage of the RF signal, (d) is a waveform diagram of the output signal of the RF comparator, and (e) is a diagram illustrating a change in the counter value counted by the jump control unit. FIG.

FIG. 8 is an explanatory diagram showing an outline of a configuration of an optical disc device including a conventional focus control device.

[Explanation of symbols]

 Reference Signs List 2 RF comparator 3 Jump controller 21 Four-layer optical disk (multilayer optical disk) 21a First recording layer (recording layer) 21b Second recording layer (recording layer) 21c Third recording layer (recording layer) 21d Fourth recording layer (recording) Layer) VFE Voltage level of focus error signal VA reference voltage (first focus error reference voltage) VB reference voltage (second focus error reference voltage) VC reference voltage (RF reference voltage)

Claims (4)

[Claims] 1. A focus control method for controlling a focus on a multilayer optical disc having a plurality of stacked recording layers, wherein a focus state is detected during recording or reproduction of the multilayer optical disc, and a defocus is detected. When this occurs, the number of jumping layers of the recording layer due to defocus and the direction thereof are determined based on the focus state transition process,
A focus control method comprising performing focus control so as to return focus to an original recording layer. 2. The number of times that the voltage level of a focus error signal becomes equal to or higher than a first focus error reference voltage which is a voltage value corresponding to an upper limit of a focused state, and a voltage value corresponding to a lower limit of a focused state. (2) calculating the number of skipping layers of the recording layer based on the number of times the focus error voltage is equal to or less than the reference voltage; and Based on the slope of the waveform of the focus error signal when the voltage becomes equal to or higher than the RF reference voltage which is a voltage value corresponding to the lower limit of
Detecting the out-of-focus direction. 3. A focus control device for controlling a focus on a multilayer optical disc having a plurality of stacked recording layers, wherein a focus state is detected during recording or reproduction of the multilayer optical disc, and defocus is detected. When this occurs, the number of jumping layers of the recording layer due to defocus and the direction thereof are determined based on the focus state transition process,
A focus control device, comprising: a control unit that performs focus control so as to return focus to an original recording layer. 4. An RF comparator for level-comparing an envelope voltage of an RF reproduction signal with an RF reference voltage which is a voltage value corresponding to a lower limit of a state near a focus state, the control means comprising: The number of times that the voltage level becomes equal to or higher than the first focus error reference voltage which is a voltage value corresponding to the upper limit of the focus state, and the number of times the voltage level becomes equal to or lower than the second focus error reference voltage which is the voltage value corresponding to the lower limit of the focus state The number of jump layers of the recording layer is calculated based on the above, and the focus is determined based on the inclination of the waveform of the focus error signal when the RF comparator determines that the state is in the vicinity of the focused state. Detect the direction of deviation,
4. The focus control device according to claim 3, further comprising: a jump control unit that controls a focus jump based on the number of skipping layers of the recording layers and a direction of defocus.