JPH1055546A - Optical disk control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a stable focus search in a short time by making inclinations of waveforms of a search signal before and after the focus pull-in time gentle respectively. SOLUTION: A focus error signal obtained by an optical pickup 122 is inputted to a matrix amplifier 123, where a difference signal is inputted to an A/D converter 126 while a sum signal an A/D converter 129 respectively. A reference voltage Vref is added via an A/D converter 124 and an offset adjusting part 125 to an output of the converter 126 to be inputted to a phase compensating part 127, and this output signal or the sum signal via a focus pull-in part 130 is operated to drive a focus actuator 133 together with the voltage Vref. Now, a sum signal waveform is set at a prescribed level, and when the search signal waveform reaches this level, its waveform inclination is made to be gentle. A focusing point is recognized by the difference signal. That is, a search is commenced, and when the sum signal becomes equal to or more than the prescribed level, a start speed is lowered to make the inclination of the signal waveform gentle, thus performing the stable search in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical disk device for controlling focus on an optical disk.

[0002]

2. Description of the Related Art FIG. 15 is a block diagram showing the overall configuration of a conventional optical disk device. In the drawing, 1 optical disk (for example, a multilayer film disk), 2 is a disk motor, 3 is a disk motor servo circuit, 4 is a laser diode for generating a laser for writing / reading to / from the optical disk 1,
5 is an objective lens for condensing the irradiation light / reflected light of the optical disc 1, 6 is a focusing actuator for driving the objective lens 5 in the focusing direction with respect to the optical disc 1,
Reference numeral 7 denotes a tracking actuator for driving the objective lens 5 in the tracking direction with respect to the optical disc 1, reference numeral 8 denotes a photodetector for detecting reflected light from the optical disc 1 passing through the objective lens 5, and reference numeral 9 denotes a pickup feeding mechanism for feeding and moving a pickup. Reference numeral 10 denotes an automatic laser power control circuit that controls the power of irradiation light generated by the laser diode 4. Reference numeral 11 denotes a focusing servo circuit that controls the focusing of the objective lens 5 on the optical disc 1 via a focusing actuator 6.
Reference numeral 2 denotes a tracking servo circuit that controls the tracking of the objective lens 5 with respect to the optical disk 1 via the tracking actuator 7, and reference numeral 13 denotes a pickup feed servo circuit that controls the pickup feed through the pickup feed mechanism 9. Here, it is assumed that the optical pickup includes a laser diode 4, an objective lens 5, a focusing actuator 6, a tracking actuator 7, and a photodetector 8.

Here, the focusing servo keeps the relative distance between the objective lens and the signal surface of the optical disk constant with respect to the surface deflection of the optical disk, and the disk signal surface is in the range of the laser beam waist, so-called depth of focus (about ± 1 μm). )
The objective lens is controlled so as to be located in the inside. The focusing servo detects a focusing error signal from the state of light reflected from the disk, and drives the objective lens accordingly. FIG. 16 is a block diagram showing a configuration of a conventional focusing servo circuit. Reference numeral 140 denotes a photodetector in which four diodes are divided into four, and detection currents from two sets of diagonal detectors are converted into voltage signals by a current-voltage conversion circuit 141 and then output to a subtraction circuit 142, respectively. Input to generate a focusing error signal. The focusing error signal drives the focusing actuator 146 through a servo loop phase compensation circuit 143, a loop switch circuit 144, and a drive circuit / pickup UP / DOWN circuit 145. The relative position between the objective lens (not shown) and the optical disk must be kept within ± 1 μm, but it is impossible to mount the disk on a CD player with high accuracy within ± 1 μm. For this reason, it is necessary to lift the objective lens at a position distant from the disk and drive the objective lens within the servo control range, that is, until a focusing error signal is obtained. The pickup UP / DOWN signal is an objective lens drive signal for this purpose. The switch 144 is connected to an automatic focus detection signal (FO) when the objective lens enters a range where servo control can be performed, that is, an S-shaped focusing error signal negative feedback area.
A switch for closing the servo loop with the K signal).

FIG. 17 is a block diagram showing a configuration of a conventional automatic focus detection circuit for obtaining a FOK signal and an operation waveform thereof. First, the switch 144 in FIG. 17 is connected to the a side, and when a pickup UP / DOWN signal is input, the actuator 146 is driven and the objective lens moves up and down. The pickup UP / DOWN signal level is set so that the objective lens always passes through the in-focus position. When the added output from the adder 147 corresponding to the sum of the output signals of the pickup light detector 144 is viewed as an output signal (shown in the drawing) of the waveform equivalent circuit 148, a signal that increases as the objective lens approaches the disk. Becomes The AC component in the signal is a component due to a minute surface wobble of the disk and a signal component of the recording pit. On the other hand, the reproduced signal of the signal is a signal whose DC component is cut by the capacitor. The signal and the signal are error-amplified by an error amplifier 149 having a voltage gain of 1,
The DC component of the output signal of the photodetector 140 is extracted. The signal FOK is detected by comparing the signal with a reference voltage Vref for setting the servo pull-in range. FIG.
Switch 144 is connected to the b side when the control signal is "High", and when the FOK signal is detected, that is, when the objective lens enters the focusing servo control range by the pickup UP / DOWN signal. ,
The switch is connected to the b side to close the focusing servo. That is, the UP / DOWN control of the pickup is stopped simultaneously with the detection of the FOK signal.

[0005]

When performing a normal focus search, it is preferable that the operation of the focus actuator at the time of focus pull-in be performed earlier. If the focus search takes a long time, for example, when an optical disc is loaded on a personal computer or a player, extra time is required until image information is obtained. Further, when focus control is lost due to scratches on the optical disk or vibration of the optical disk device, information may be interrupted until the focus control is restored. Conventionally, a method of pooling video information in memory has been used,
This also has a problem that the video is interrupted on the way because the memory capacity is limited. Therefore, it is necessary to shorten the time from the loading to the reproduction by shortening the time of the focus search, and to perform the focus control stably without being affected by scratches or vibration. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an optical disk control device capable of shortening the time for focus search and performing reliable and stable focus control.

[0006]

An optical disk control device according to the present invention is a device for performing focus control of an optical disk by digital arithmetic processing. The slope of the ramp waveform has a plurality of slopes, and the slope of the ramp waveform changes at a timing when the level of the amount of light reflected from the optical disk exceeds a predetermined value.

Further, in the search operation of the focus actuator at the time of focus pull-in, the slope of the ramp waveform applied to the focus actuator has a plurality of slopes, and the change in the slope of the ramp waveform is the same as that in the previous search operation. This is performed slightly before the applied voltage near the focus detection.

In addition, a reference voltage value of a circuit for generating the focus error signal input from outside of the arithmetic circuit is input to an input portion of the digital filter in the arithmetic unit at the time of focus pull-in until the focus is detected. It is something to input.

Furthermore, the focus error signal before the focus pull-in input to the digital arithmetic unit is compared with a reference voltage in a focus error signal generation circuit different from the arithmetic circuit, and the comparison value is stored. The focus control loop after pull-in is closed by a focus error signal obtained by correcting the DC level of the focus error signal with the stored value.

In addition, an RF signal obtained from an information track of the optical disk after the focus pull-in is input to the arithmetic unit, and an RF signal amplitude obtained by envelope detection of the RF signal is passed through a disk rotation frequency, so that a flaw or a longest pit length or While passing through a filter that removes relatively high frequency fluctuation components such as preformat information, the RF signal amplitude at a predetermined angle on the disk is filtered based on the disk rotation information obtained from the FG from the disk motor. The focus offset amount is measured by measuring the signal after passing through, and the focus offset amount is increased / decreased each time the disk is rotated to search for a focus offset amount that maximizes the RF signal amplitude.

Further, after the focus is pulled in, a reproduction signal from the optical disk is input to a PLL circuit for data detection, and a high-pass filter for cutting a DC component to an output of the phase comparator in the PLL circuit, and an output fluctuation of the phase comparator. While inputting the amount of jitter obtained through a low-pass filter for observing the amount to the arithmetic unit, passing the amount of jitter through a disk rotation frequency,
The signal passes through a filter that removes a fluctuating component of a relatively high frequency such as a flaw, a longest pit length, or preformat information, and the jitter at a predetermined angle on the disk is determined based on disk rotation information obtained from a disk motor FG. The amount is measured from the signal after passing through the filter, and the focus offset amount is increased / decreased for each rotation of the disk to search for the focus offset amount that minimizes the jitter amount.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a block diagram showing an overall configuration of a focus control system in the optical disc control device according to the first embodiment. In the figure, 120 is an optical disk, 12
1 is a disk motor, 122 is an optical pickup, 123
Is a matrix amplifier, and 124, 126 and 129 are A
/ D converter, 125 is an offset adjustment unit, 127 is a phase compensation unit, 128 is a changeover switch, 130 is a focus pull-in unit, 131 is a D / A converter, 132 is a focus actuator driver, 133 is a focus actuator, and 134 is a digital 2 shows an arithmetic unit. Also,
FIG. 2 is a diagram showing operation waveforms in a search operation of the focus actuator at the time of focus pull-in. Here, as shown in the figure, the slope of the ramp waveform (search signal waveform) applied to the focus actuator 133 has a plurality of slopes, and the change in the slope of the ramp waveform is the amount of reflected light from the optical disc 120. This is performed at a timing when the level exceeds a predetermined value. In the drawing, (a) is a search signal waveform, (b) is a sum signal waveform,
(C) shows a difference signal waveform. FIG. 3 is a flowchart showing the flow of a signal at the time of focusing.

1 will be described. A focus error signal obtained from the optical pickup 122 is supplied to the A / D converters 126 and 1 via a matrix amplifier 123.
29. The focus error signal output from the A / D converter 126 is added to the reference voltage Vref via the A / D converter 124 and the offset adjustment unit 125, and is added to the phase compensation unit 127. This output signal is switched to one of the focus error signals via the focus pull-in unit 130 by the changeover switch 128 and input to the D / A converter 131. This signal is Vr
ef is input to the actuator driver 132, and an output signal from the actuator driver 132 drives the focus actuator 133 to perform focus control. Here, at the time of pull-in of the focus search, there is a situation in which the lower the speed at which the focus actuator is driven, the easier the pull-in. However, if the driving speed of the focus actuator at the time of pull-in is low, the slope of the search signal waveform becomes gentle, and the pull-in time of the focus search becomes long. Conversely, if the speed at which the focus actuator is driven is increased, pull-in is difficult, and the focus search is performed many times, which also causes the focus search pull-in time to be long. Therefore, as in the case of the search signal waveform in FIG. 2A, a method is conceivable in which the slope of the search signal waveform is made gentle only before and after the pull-in in the focus search. This sets a predetermined level to the sum signal waveform of FIG. 2B, and when this level is reached, the slope of the search signal waveform of FIG. Here, the focus of the focus is shown in FIG.
It can be determined from the difference signal of (c). This operation will be described with reference to FIG. 3. First, a search is started to detect whether the sum signal is at a certain level or more. If the level is equal to or higher than the predetermined level, the slope of the search signal waveform is reduced by lowering the rising speed. Here, it is determined whether or not the focus control is being performed. If the focus control is being performed stably, the focus pull-in operation ends. When the focus control is not performed, the search is started again. As described above, by making the slope of the search signal waveform gradual only before and after the focus pull-in, the focus search can be performed stably in a short time.

Embodiment 2 FIG. FIG. 4 shows a block diagram of the internal configuration of a normal focus control system arithmetic unit in the optical disc control apparatus according to the second embodiment and a search waveform at the time of normal focus search. FIG. (B) shows the difference signal waveform.
In the figure, reference numeral 14 denotes an A / D converter, and reference numeral 15 denotes a unit of gain.
(G / 1) element, 16 is a changeover switch, 17, 1
9, 21, 23, 25 and 27 are gain elements and 18, 2
0, 24, and 26 are delays (delays) indicating values before one operation.
Element, 22 is a gain (G) element, 28 is a D / A converter,
Reference numeral 29 denotes a driver, and reference numeral 30 denotes a focus actuator. FIG. 5 shows that in the search operation of the focus actuator at the time of focus pull-in, the slope of the ramp waveform applied to the focus actuator has a plurality of slopes, and the change in the slope of the ramp waveform is the same as that in the previous search operation. FIG. 7A shows a signal waveform at the time of a focus search performed just before an applied voltage near the focus detection. FIG. 7A shows a search signal waveform, and FIG. It is. FIG. 6 is a flowchart showing the flow of a signal at the time of focusing.

Next, the operation will be described with reference to the drawings. First, the focus error signal is input to the A / D converter 14 and, via the changeover switch 16, the gain element 17,
The signal is input to a filter composed of 19 and 21 and delay elements 18 and 20. Then, the filtered signal is passed through a gain element 22 and further to a gain element 23,
The signal is input to a D / A converter 28 via a filter composed of 25, 27 and delays 24, 26. The output signal from the D / A converter 28 is input to the driver 29 and drives the focus actuator 30. Further, the focusing voltage is input to one element 15 of the gain, and is input to a filter composed of gain elements 17, 19, 21 and delay elements 18, 20 via a changeover switch 16 until the focus loop is closed. Here, the DC component of the focus voltage passes through the gain component 1 and gain component 22, resulting in the same gain. The search signal waveform of the normal focus search obtained from the above configuration is shown in FIG.
(A). FIG. 4B shows the focal point by a difference signal waveform, and a voltage at the focal point can be obtained by performing a normal focus search. Referring to FIG. 5, as shown in FIG. 4, first, the focus search is performed quickly (large) so as not to intentionally pull in the focus search.
By performing at a speed, a voltage at the focal point can be obtained. The voltage at the in-focus point is stored, and as shown in FIG. 5A, when the focus search is performed again, the slope of the search signal waveform is gradually changed near the in-focus point. Here, if the focus control is not performed, the search signal waveform is rapidly lowered as shown in FIG. As described above, at the time of the first focus search,
The focus search is performed at a fast (large) speed so as not to be pulled in, the voltage of the focal point at this time is stored, and in the second focus search, the gradient of the search voltage near the stored focal point is calculated. By making the change gradual, the focus search can be performed quickly and reliably. FIG. 6 is a flowchart showing the flow of signals at the time of focus pull-in. In the first focus search, rise and fall are performed at a relatively fast (large) speed, and the voltage at the time of focusing is stored. . Here, the focus loop is not closed. Next, the focus search is started, and the starting speed is reduced near the focal point. Thereafter, it is determined whether or not the focus control has been performed. If the focus control has been performed, the focus pull-in is terminated, and if the focus control has not been performed, the focus search is started again. As described above, it is possible to reduce the time from loading an optical disc to a personal computer or an optical disc player to obtaining image information, and the time until focus control is restored even if focus control is lost due to scratches or device vibration. Thus, even when compared with a conventional method of storing image information in a memory so that the image information is not interrupted on the way, it is possible to recover out-of-focus sufficiently quickly and reliably.

Embodiment 3 FIG. 7 is a block diagram showing an internal configuration of a calculation unit of a focus control system in the optical disc control device according to the third embodiment. In the figure, 31 is an A / D converter, 32 is a noise filter, 33 is a register, 34 is an A / D converter, 35 is a changeover switch, 3
6, 38, 40, 41, 43, and 45 are gain elements,
7.39, 42 and 44 are delay elements, 46 is a D / A converter, 47 is a driver, and 48 is a focus actuator.

Next, the operation will be described. Reference voltage Vr
ef is input to the A / D converter 31 and the noise filter 3
2 and stored in the register 33. The stored signal is supplied to the A / D converter 3 by the changeover switch 35.
4 is switched to one of the converted focus error signal. Either of these signals is passed through a digital filter composed of gain elements 36, 38, 40 and delay elements 37, 39, and further passed through a gain element 4
Input is made to a digital filter composed of 1, 43, 45 and delay elements 42, 44, and this output is converted by a D / A converter 46, and a focus actuator 48 is driven via a drawer 47. I have. First, before applying focus control, that is,
Vref is passed through the digital filter in advance just before the focus is pulled. This is because when the initial values of the delay elements 37, 39, 42 and 44 are 0,
This is because the transient response of the digital filter is degraded and becomes difficult to pull in. A general digital filter of the IIR type is used. However, if a value of 0 is set in the delay portion in the IIR type digital filter, a fixed offset amount is added at the time of focus pull-in. In the embodiment 3, until the voltage of Vref is reached, only the transient response of the IIR filter is
The pull-in operation is delayed. In this case, if the focus is pulled in, by using the switch 35 to switch to the focus error signal that has been A / D-converted, the transient response of the digital filter can be performed more quickly than starting from zero. it can. Further, for example, when Vref is set to 2.5 V, the power supply voltage fluctuates due to the temperature characteristics, the loading motor and the disk motor, and may fluctuate from 2.5 V. is there. Further, the same effect can be obtained by storing the reference voltage Vref filtered by the noise filter 32 in the register 33 and setting the value of this register as the initial value of the delay elements 37, 39, 42, 44.

Embodiment 4 FIG. 8 is a block diagram showing an internal configuration of a calculation unit of a focus control system which is an optical disc control device according to the fourth embodiment, in which a focus error signal is centered on the reference voltage Vref.
In the figure, 49 is an A / D converter, 50 is a noise filter, 51 is a register, 52 is an A / D converter, and 53 and 5
5,57,58,60,62 are gain elements, 54,5
6, 59, 61 are delay elements, 63 is a D / A converter,
Reference numeral 64 denotes a driver, and 65 denotes a focus actuator. FIG. 9 is a flowchart showing a signal flow when the configuration shown in FIG. 8 is used.

Next, the operation will be described with reference to the drawings. First, Vref converted by the A / D converter 49 is
The difference between the focus error signal converted by the A / D converter 52 and the focus error signal is input to the noise filter 50.
This output is stored in the register 51, and this output is further added to the A / D converted focus error signal.
This added signal is passed through a digital filter composed of gain elements 53, 55, 57 and delay elements 54, 56, and gain elements 58, 60, 62 and delay element 59,
It is input to the digital circuit constituted by 61. This output is input to a driver 64 via a D / A converter 63 to drive a focus actuator 65. In this case, when performing focus pull-in stably, the focus error signal may be adjusted so that the focus error signal is centered on Vref. Assuming that the focus error signal is output around Vref, the output of the driver 64 becomes 0 when the input is Vref. When the voltage input to the driver 64 is higher than Vref, the current of +
5 if the voltage input to the driver 64 is lower than Vref,
5 flows. The original focus error signal is also Vr
ef. However, it is usually difficult to obtain a focus error signal centered on Vref due to variations in the gain of the matrix amplifier and variations in the offset of the operational amplifier. Therefore, the difference between the A / D-converted Vref and the A / D-converted focus error signal is obtained, and the signal filtered by the noise filter 50 is added to the focus error signal so that the Vref center is not disturbed by noise components. Focus error signal must be V
ref center. Further, a series of operations will be described based on the flowchart of FIG. First, Vre
f is measured, and this value is temporarily set to A. Next, the focus error signal before the pull-in is measured, and this value is temporarily set to B. Here, AB is stored in the register 68, and this value is temporarily set to C. The value of C is added to the focus error signal to perform a focus pull-in operation. Here, it is determined whether or not a predetermined level is continuously obtained as the sum signal level. When the focus pull-in is completed, the focus pull-in is completed. If the focus pull-in operation has not been completed, it is determined whether the focus pull-in operation has been tried a predetermined number of times. If the focus pull-in operation has been tried, the value of C is changed, and the focus pull-in operation is performed again. In addition, when a predetermined number of tries have not been performed, the focus pull-in operation is performed again. From the above, temporarily
Even if the focus error signal is obtained at the center of Vref, even if the actuator driver is not driven at the center of Vref, or if a predetermined offset is required at the time of pulling in due to shaft friction or the posture of the actuator, stable pull-in is performed. Operation is realized.

Embodiment 5 As described above, by always obtaining the focus error signal at the center of the reference voltage Vref, the pull-in operation can be performed extremely stably. However, the servo offset amount after the pull-in is always optimized. Do not mean. This is because the offset at the time of pull-in and the offset level after the pull-in do not always match due to the imbalance of the focus sensor or the search polarity at the time of pull-in. Therefore, an offset adjustment method after pull-in will be described below. FIG. 10 is a block diagram showing the internal configuration of the arithmetic unit of the focus control system in the optical disk control device according to the fifth embodiment, which is configured to perform offset adjustment so that the sum signal is maximized. In the figure, 66 is an A / D converter, 67 is a noise filter, 68 is a register, 69 is an A / D converter, 70, 72, 74, 75, 77, 79 are gain elements, 71, 73, 76, 78 are Delay element,
80 is a D / A converter, 81 is a driver, 82 is a focus actuator, 83 is an A / D converter, 84 is a noise filter, 85 is a GIO (general purpose input / output port), 86 is a sample circuit, and 87 is a hill-climbing algorithm. Show. FIG. 11 is a flowchart showing a signal flow when the configuration of FIG. 10 is used.

The operation will be described with reference to FIG. 10. The reference voltage Vref converted by the A / D converter 66 is A / D
The difference from the focus error signal converted by the D converter 69 is input to the noise filter 67. This output is stored in the register 68. The sum signal is A /
The signal is converted by the D converter 83 and input to the sample circuit 86 via the noise filter 84. Further, the motor F
The G signal is input to the GIO, and this output is
6 is input. Here, the output of the sample circuit 86 to which the two signals are input is added to the A / D-converted focus error signal via the hill-climbing algorithm circuit 87. This signal is further added to the signal stored in the register 68, and the added signal is added to the gain elements 70, 72,
The signal is inputted to a digital circuit composed of gain elements 75, 77, 79 and delay elements 76, 78 via a digital filter composed of 74 and delay elements 71, 73. This output is input to a driver 81 via a D / A converter 80, and is output to a focus actuator 82.
Is driven. A series of operations will be described based on the flowchart of FIG. First, when the focus pull-in operation is completed, the track pull-in operation is completed. Next, the sum signal level is measured at a specific position (angle) within one cycle of the disk, and the focus offset is set to +
Shift in the direction. It is determined whether the sum signal level has increased due to the shift in the + direction. If the sum signal level has increased, the focus offset is again shifted in the + direction. If the sum signal level has not increased, the focus offset is shifted in the negative direction. If the sum signal level has increased, the focus offset is shifted again in the negative direction. If the sum signal level has not increased, the offset value is shifted. Is held in the previous state, and the position where the sum signal becomes maximum is detected, and the offset adjustment is completed. This is because, as described in the fourth embodiment, even if the focus error signal is obtained at the Vref center, it is not always the best point of the focal point. For example, when the mounting position of the sensor of the optical pickup is shifted, or when the disc is tilted and tilted, optically shifting occurs. Not necessarily. Also, since the reflected light amount obtained as a sum signal has a periodic fluctuation with respect to the rotation of the disk, the hill-climbing algorithm changes depending on the position to be detected. Must. Therefore, it is necessary to input the motor FG signal and take a sample in the sample circuit 86. From the above, by adjusting the offset so that the reproduction signal amplitude, which is the sum signal (reflected light amount), is maximized, the reproduction signal amplitude of the shortest pit length is approximately considered to be the maximum, so that the focus point can be adjusted. Find the best points.

Embodiment 6 FIG. FIG. 12 is a block diagram showing the internal configuration of the arithmetic unit of the focus control system in the optical disk control device according to the sixth embodiment, which is configured to perform offset adjustment so as to minimize the jitter amount. In the figure, 88 is an A / D converter, 89 is a noise filter,
90 is a register, 91 is an A / D converter, 92, 94, 9
6,97,99,101 are gain elements, 93,95,9
8, 100 are delay elements, 102 is a D / A converter, 1
03 is a driver, 104 is a focus actuator,
105 is an A / D converter, 106 is a noise filter, 10
7 is a GIO (general purpose input / output port), 108 is a sample circuit, and 109 is a hill-climbing algorithm. FIG. 13 is a diagram showing the amount of jitter, in which 110 is a phase comparator, 111 is a high-pass filter, 112 is a detection circuit,
Reference numeral 113 denotes a low-pass filter. FIG. 14 shows FIG.
6 is a flowchart showing a signal flow when the configuration of FIG. 2 is used.

Next, the operation will be described with reference to the drawings. First, A
Voltage Vref converted by A / D converter 88
Is input to the noise filter 89 by taking the difference from the focus error signal converted by the A / D converter 91. This output is stored in the register 90. The jitter amount is converted by the A / D converter 105 and input to the sample circuit 108 via the noise filter 106. Further, the motor FG signal is input to the GIO 107, and the output is input to the sample circuit 108. Here, the output of the sample circuit 108 to which the two signals are input is added to the A / D-converted focus error signal via the hill-climbing algorithm circuit 109. This signal is further added to the signal stored in the register 90, and the added signal is added to gain elements 92, 94, 96 and delay elements 93,
The signal is input to a digital filter composed of gain elements 97, 99, 101 and delay elements 98, 100 via a digital filter composed of 95. This output is input to the driver 103 via the D / A converter 102, and drives the focus actuator 104. The amount of jitter will be described with reference to FIG. 13. The amount of jitter is obtained by comparing the PLL clock with the binary data by the phase comparator 110, and is indispensable for detecting data. Here, the output from the phase comparator 110 is returned to the PLL loop, and is input to the high-pass filter 111 to cut the DC component. Then, the jitter amount is obtained via the detection circuit 112 and the low-pass filter 113. . A series of operations will be described based on the flowchart of FIG. First, when the focus pull-in operation is completed, the track pull-in operation is completed. Next, the jitter amount is measured at a specific position (angle) within one cycle of the disk, and the focus offset is shifted in the + direction. It is determined whether the level of the jitter amount has decreased due to the shift in the + direction. When the level of the jitter amount decreases, the focus offset is shifted again in the + direction. If the level of the jitter amount has not decreased, the focus offset is shifted in the negative direction, and the level of the jitter amount is detected again.If the level of the jitter amount has decreased, the focus offset is shifted again in the negative direction, and If the level of the amount has not decreased, the offset value is kept at the previous state,
The position where the amount of jitter is minimized is detected, and the offset adjustment is completed. Here, since the data error is almost proportional to the amount of jitter, minimizing the amount of jitter is a condition for detecting the best focus position and performing a stable focus search. Also, the pattern of the shortest pit in the eye pattern may not come to the center of the eye pattern due to variations in the depth of the data pits on the disk. This is a case where the asymmetry is deviated. In such a case, the reliability is higher when the position where the jitter amount is the smallest is detected than when the position where the sum signal is the largest.

[0024]

According to the present invention, the slope of the search signal waveform is smoothed before and after the focus is pulled, so that stable and reliable focus pull-in is always performed, and the slope of the focus search voltage as a whole is steep to spend the focus search. Saved time. Further, by switching the inclination of the search voltage at the level of the sum signal, even if there is a variation in the friction of the shaft or the sensitivity of the actuator, it is possible to reliably switch the point of change in the inclination from a focal point to a position before a predetermined point. It has become possible.

In the first search, the search is performed at a high speed without pulling in the focus, so that the in-focus voltage can be learned,
In the second focus pull-in, the slope of the search signal waveform is made gentle near the focal point, and if the pull-in fails,
The time spent on focus search has been shortened by lowering it all at once. Similarly, by switching the slope of the search voltage at the level of the sum signal, even if there is a variation in the friction of the shaft or the sensitivity of the actuator, the point of change in the slope can be reliably determined at a position before a predetermined point from the focal point. It is now possible to switch.

Further, by inputting the reference voltage Vref to the digital filter immediately before performing the focus pull-in, the characteristics of the focus pull-in operation can be improved without being affected by the transient response of the digital filter.

Further, when the focus error signal is
By adjusting the focus error signal so that the focus error signal is located at the center of ref, the characteristics of the focus pull-in operation can be improved without being affected by the transient response of the digital filter. Further, even with respect to drift and offset of the servo matrix amplifier, since a focus error signal is obtained at the center of the reference voltage of the servo circuit, there is no unnecessary offset during servo pull-in, and stable pull-in is realized.

Further, another offset adjustment is performed at the time of pull-in and after the pull-in, and the offset is adjusted so that the sum signal (reflected light amount) becomes maximum after the pull-in, so that the offset is not affected by optical deviation. The quality of the reproduced signal after focusing can be improved.

By adjusting the offset so that the jitter amount is minimized, the quality of the reproduced signal after focusing can be improved even when the asymmetry is shifted.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a focus control system in an optical disc control device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing signal waveforms at the time of a focus search in the optical disc control device according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing a signal flow at the time of focus pull-in in the optical disc control device according to the first embodiment of the present invention;

FIG. 4 is a block diagram showing an internal configuration of an arithmetic unit of a focus control system in an optical disc control device according to a second embodiment of the present invention, and a diagram of a search waveform during a normal focus search.

FIG. 5 is a diagram showing a search signal waveform and a difference signal waveform in the optical disc control device according to the second embodiment of the present invention.

FIG. 6 is a flowchart showing a signal flow at the time of pulling a focus in the optical disc control device according to the second embodiment of the present invention;

FIG. 7 is a block diagram illustrating an internal configuration of a calculation unit of a focus control system in an optical disc control device according to a third embodiment of the present invention.

FIG. 8 is a block diagram illustrating an internal configuration of a calculation unit of a focus control system in an optical disc control device according to a fourth embodiment of the present invention.

FIG. 9 is a flowchart showing a signal flow in the optical disc control device according to the fourth embodiment of the present invention.

FIG. 10 is a block diagram illustrating an internal configuration of a calculation unit of a focus control system in an optical disc control device according to a fifth embodiment of the present invention.

FIG. 11 is a flowchart showing a signal flow in the optical disc control device according to the fifth embodiment of the present invention.

FIG. 12 is a block diagram showing an internal configuration of a calculation unit of a focus control system in an optical disc control device according to a sixth embodiment of the present invention.

FIG. 13 is a diagram illustrating a jitter amount in the optical disc control device according to the sixth embodiment of the present invention.

FIG. 14 is a flowchart showing a signal flow in the optical disc control device according to the sixth embodiment of the present invention.

FIG. 15 is a block diagram showing the overall configuration of a conventional optical disc device.

FIG. 16 is a block diagram showing a configuration of a conventional focusing servo circuit.

FIG. 17 is a block diagram showing a configuration of a conventional automatic focus detection circuit for obtaining a FOK signal, and a diagram showing operation waveforms thereof.

[Explanation of symbols]

Reference Signs List 1 optical disk (multilayer film disk), 2 disk motor, 3 disk motor servo circuit, 6 focusing actuator, 7 tracking actuator, 11 focusing servo circuit, 12
Tracking servo circuit, 30 focus actuator, 32 noise filter, 33 register,
48 focus actuator, 50 noise filter, 51 register, 65 focus actuator, 66 A / D converter, 67 noise filter, 68 register, 82 focus actuator, 84 noise filter, 86 sample circuit, 87 hill climbing algorithm circuit, 89 noise filter, 90 register, 104 focus actuator, 106 noise filter, 108
Sample circuit, 109 hill climbing algorithm circuit,
110 phase comparator, 111 high-pass filter,
112 detection circuit, 113 low-pass filter, 1
20 optical disk, 125 offset adjustment unit, 1
27 phase compensation unit, 130 focus pull-in unit,
132 actuator driver, 133 focus actuator, 134 digital operation unit.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshinobu Ishida 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation

Claims (6)

[Claims] 1. An apparatus for performing focus control of an optical disc by digital arithmetic processing, wherein a ramp waveform applied to the focus actuator has a plurality of gradients in a search operation of the focus actuator at the time of focus pull-in. An optical disk control device wherein the slope of the ramp waveform is changed at a timing when the level of the amount of reflected light from the optical disk exceeds a predetermined value. 2. An apparatus for performing focus control of an optical disc by digital arithmetic processing, wherein a ramp waveform applied to the focus actuator has a plurality of gradients in a search operation of the focus actuator at the time of focus pull-in. An optical disk control device wherein the change in the slope of the ramp waveform is performed slightly before the applied voltage near the focus detection in the previous search operation. 3. An apparatus for performing focus control of an optical disk by digital arithmetic processing, wherein the input unit of a digital filter in an arithmetic unit for performing the digital arithmetic processing until a focus is detected at the time of focus pull-in is provided. An optical disk control device for inputting a reference voltage value of a circuit for generating a focus error signal input from outside of an arithmetic unit. 4. An apparatus for performing focus control of an optical disk by digital arithmetic processing, wherein said focus error signal before focus pull-in input to a digital arithmetic unit for performing said digital processing and a different focus from said arithmetic unit. Comparing the reference voltage in the error signal generation circuit, storing the comparison value, and closing the focus control loop after the pull-in with the focus error signal obtained by correcting the DC level of the focus error signal with the stored value. An optical disk control device characterized by the above-mentioned. 5. An apparatus for performing focus control of an optical disk by digital arithmetic processing, wherein an RF signal obtained from an information track of the optical disk after focusing is input to an arithmetic unit for performing the digital arithmetic processing, The RF signal amplitude obtained by envelope detection of the signal is passed through the disk rotation frequency, passed through a filter that removes relatively high frequency fluctuation components such as flaws, longest pit lengths, or preformat information, and obtained from the FG from the disk motor. R at a predetermined angle on the disk based on the disk rotation information obtained
The F signal amplitude is measured from the signal after passing through the filter, and the focus offset amount is increased / decreased each time the disk is rotated.
An optical disk control device for searching for a focus offset amount at which the RF signal amplitude has a maximum value. 6. An apparatus for performing focus control of an optical disk by digital arithmetic processing, wherein a read signal from the optical disk is read by a P for data detection after focusing is performed.
The amount of jitter that is input to the LL circuit and that is obtained through a high-pass filter that cuts a DC component at the output of the phase comparator in the PLL circuit and a low-pass filter that observes the amount of output fluctuation of the phase comparator is calculated as The digital signal is input to an arithmetic unit that performs digital arithmetic processing, and the jitter amount is passed through the disk rotation frequency, and is passed through a filter that removes relatively high frequency fluctuation components such as flaws, longest pit lengths, or preformat information. Based on the disk rotation information obtained from the FG of the motor, the jitter amount at a predetermined angle on the disk is measured from the signal after passing through the filter, and the focus offset amount is increased or decreased for each rotation of the disk. Characterized by searching for a focus offset amount that minimizes Disk controller.