JPH10143880A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely adjust an offset in a short time even in a disk with a narrow allowable range of a focus offset voltage by gradually increasing the offset voltage with a voltage generation circuit and holding an RFS signal voltage to minimum. SOLUTION: A regenerative RF signal 111 from an optical pickup 104 becomes an RFS signal 114 through an LPF 113 constituted of resistors, capacitors to be inputted to a control circuit 119. The control circuit 119 inputs the RFS signal 114, and generates a voltage generation control signal 124 to control a voltage generation circuit 118 and to output a focus switch signal 120. Succeedingly, the voltage generation circuit 118 generates the offset voltage 122 to output it to an offset injection circuit 117. At this time, the offset voltage 122 is increased gradually, and the DC voltage of the RFS signal 114 is reduced to be made the minimum DC voltage at a prescribed voltage. When the voltage 122 is increased further, the DC voltage of the RFS signal 114 turns to increase. In such a manner, the voltage 122 is adjusted so that the DC voltage becomes the minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical disk device, and more particularly to an optical disk device for adjusting a DC offset value of a focus servo system.

[0002]

2. Description of the Related Art An optical disk apparatus requires a focus servo circuit for keeping the distance between an objective lens and an optical disk constant against warpage or vertical vibration of the optical disk. For example, when the astigmatism method is used as a method of detecting a focus error signal, a focus error signal is generated by calculating the four output signals using a four-divided detector as shown in FIG. At this time, when the information recording surface of the optical disk is the focal plane of the objective lens, the beam cross section on the quadrant detector becomes circular, and the focus error signal becomes zero.

[0003] However, an offset may occur in the focus error signal due to the detection sensitivity of the four-segment detector, the variation of the arithmetic element, and the like. Also, an offset voltage is generated due to the characteristics of the focus servo circuit. Therefore, in the state where the focus offset adjustment is not performed, it is impossible to stably reproduce the image due to the focus shift.

As a method of solving such a problem, Japanese Patent Application Laid-Open No. 8-7311, entitled "Optical Disk Device",
No. 94033, "Optical disk device" and the like have been proposed. In the former Japanese Patent Application Laid-Open No. 8-7311, "optical disk device" is a device in which focus offset adjustment is performed so that the amplitude of the sum of RF signals is maximized. This is a device for adjusting the focus offset so that the error rate is minimized.

[0005]

SUMMARY OF THE INVENTION A compact disk (hereinafter referred to as a CD) is used as a peripheral device of a computer.
-ROM drive devices are widespread. An optical disk named DVD, which has a higher density than the recording density of this CD, has been standardized, and its reproduction apparatus has been commercialized.

FIG. 10 shows an example of the byte error rate characteristics measured by us when the focus offset voltage is adjusted in the reproduction of a CD and a DVD. In the figure, the horizontal axis is the focus offset voltage value, and the vertical axis is the byte error rate. In the figure, A is the characteristic of a CD disk, B is the characteristic of a DVD disk having a thickness of about 0.62 mm, and C is the characteristic of a DVD disk having a thickness of about 0.58 mm. From this figure, it can be seen that the focus offset voltage range for stably reproducing a DVD is very narrow for a CD. It has also been found that the best point of the focus offset voltage differs depending on the thickness of the DVD.

As described above, in the case of a DVD disk, a slight offset voltage shift causes a steep change in the byte error rate, so that it is necessary to adjust the focus offset more accurately. In the above prior art, no consideration has been given to performing the focus offset adjustment with high accuracy in a short time. That is, according to the invention described in JP-A-8-7311 "Optical disc device" and JP-A-2-94033 "Optical disc device", focus offset adjustment is performed on a DVD disc having a very narrow allowable range of focus offset voltage. In this case, it is necessary to perform adjustment by gradually changing the focus offset voltage, so that there is a problem that the time required for the adjustment becomes long.

It is therefore an object of the present invention to provide a high-quality optical disk device capable of adjusting a focus offset with high accuracy in a short time even for a disk having a narrow allowable range of a focus offset voltage and stably reproducing the disk.

[0009]

In order to achieve the above object, the present invention provides a focus error signal detecting means, a focus servo loop means, and a voltage generating stepwise changing voltage as time passes. Voltage generating means for holding one of the voltages that change in the voltage, and injecting means for injecting the output of the voltage generating means into the focus servo loop means, the output voltage of the voltage generating means After a first adjustment step (coarse adjustment step) of changing the first change voltage with a first change voltage, the second change voltage is equal to or smaller than the first change voltage. A second adjustment process (fine adjustment process) for changing the output voltage of the voltage generating means is performed, and one of the voltages that change with the second change voltage in the second adjustment process is held. The said And configured to inject an offset voltage over Kas servo loop means.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration and operation of an optical disk device according to a first embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram of an optical disk apparatus according to the present invention.

Reference numeral 101 denotes a disk such as a CD or a DVD. On the disk 101, signal information is recorded as a pit string (not shown). The signal information on the disk 101 is optically read by the optical pickup 104.
Read signal 107 output from optical pickup 104
Transmits a signal to the tracking error detection circuit 108, the focus error detection circuit 109, and the RF amplifier circuit 110, respectively.

The tracking error signal 127 detected by the tracking error detection circuit 108 is a phase compensation circuit,
It is applied to the optical pickup 104 via a tracking servo circuit 106 including a drive circuit, and forms a tracking servo loop.

The focus error signal 126 detected by the focus error detection circuit 109 passes through an offset injection circuit 117, a switch 121, a phase compensation circuit, and a focus servo circuit 105 including a drive circuit. Form.
The switch 121 switches between closing and not closing the focus servo loop according to the state of the focus switching signal 120.

The RF amplifier circuit 110 reproduces a signal corresponding to the information recorded on the disk 101,
Output as 1.

The rotation control circuit 112 controls the reproduction RF signal 11
1 and outputs a rotation error signal.
The disk motor 1 that is transmitted to the disk motor 102 via the motor driver 103 and rotates the disk 101
02 to form a spindle servo loop for rotating the disk 101.

The demodulation / reproduction circuit 115 outputs the reproduction RF signal 11
1, the modulation of the information recorded on the disk 101 is decompressed and output as a reproduction signal 116.

The control circuit 119 receives the RFS signal 114 of the reproduced RF signal 111 that has passed through the LPF 113, and outputs a voltage generation control signal 124 of a voltage generation circuit 118 and a focus switching signal 120. The LPF 113 can be composed of a resistor and a capacitor.

The voltage generation circuit 118 receives the voltage generation control signal 124 from the control circuit 119 and receives the offset voltage 1
22 is output to the offset injection circuit 117.

Hereinafter, the operation of FIG. 1 will be described. Prior to that, the RFS signal 114 of FIG.
7 and the operation of the voltage generation circuit 118 will be described in order.

First, the relationship between the RFS signal 114 and the byte error rate will be described with reference to FIG. FIG. 2A is a characteristic diagram showing an example of a byte error rate when the offset voltage 122 is adjusted, and FIG.
FIG. 9 is a characteristic diagram illustrating an example of a DC voltage of the RFS signal 114 when 2 is adjusted. In FIG. 2A, the horizontal axis represents the offset voltage 122, and the vertical axis represents the byte error rate.
In (b), the horizontal axis is the offset voltage 122, and the vertical axis is R
5 shows a DC voltage value of the FS signal 114. The lower the byte error rate when reading the information on the disc, the more stable the reproduction can be performed. In FIG. 2A, when the offset voltage 122 is gradually increased, the byte error rate decreases and reaches the minimum byte error rate e1 at a certain voltage v1, and when the offset voltage 122 is further gradually increased, the byte error rate increases. Rates begin to increase. When the offset voltage 122 in FIG. 2B is v1, the DC voltage of the RFS signal 114 has a minimum value. That is, in this example, the offset voltage 122 that minimizes the DC voltage of the RFS signal 114 may be adjusted to v1.

Next, the operation of the offset injection circuit 117 and the voltage generation circuit 118 will be described with reference to FIG. FIG. 3 shows the offset injection circuit 117 in FIG.
FIG. 2 is a configuration diagram illustrating an example of a voltage generation circuit 118. In the figure, a voltage generation circuit 118 includes a register 301 to which an output voltage generation control signal 124 of a control circuit 119 is input, and a D / A conversion circuit 302 to which an output of the register 301 is input. The voltage generation circuit 118 converts the value held in the register 301 into an analog voltage by the D / A conversion circuit 302 according to the voltage generation control signal 124, and transmits the output as an offset voltage 122 to the offset injection circuit 117.

The offset injection circuit 117 includes a resistor 3
03, a resistor 304, a resistor 305, and an amplifier 306. The offset injection circuit 117 includes resistors 303 and 30
When the values of 4, 305 are R1, R2, R3, respectively, the focus error signal 126 is transmitted to the offset injection circuit output 123 as -R2 / R1, and the offset voltage 122 is transmitted as -R2 / R3. In this example, the offset injection circuit output 123
Although the phase is inverted up to this point, an in-phase output may be used.

Next, the operation of the first embodiment of the present invention when performing the offset adjustment will be described with reference to FIGS. FIG. 4A shows the offset voltage 122 and the RFS
FIG. 4 is a diagram showing a relationship between DC voltages of a signal 114. In the figure, the offset voltage 122 is v1, v2, v3, v
RFS signal 1 at 4, v5, v6, v7, v8, v9
The 14 DC voltages are respectively r1, r5, r4, r3, r
2, r1, r1, r2, and r4. In this case, the offset voltage 122 should be adjusted near the voltage v1. FIG. 4B is a waveform chart showing the operation of the first embodiment of FIG. 1, and shows the waveforms of the offset voltage 122 and the RFS signal 114. The horizontal axis in the figure is time.

At time t1, the offset voltage 12
When 2 is set to the voltage v2, the DC voltage of the RFS signal 114 is the voltage r5. When the offset voltage 122 is increased to the voltage v5 at time t2, the RFS signal 11
4 becomes the voltage r2. Then, when the offset voltage 122 is increased to the voltage v9 at time t3, RF
The DC voltage of the S signal 114 becomes the voltage r4. At this time, r
Since 5> r2 and r4> r2, R shown in FIG.
It can be seen that the signal passed through the minimum point of the DC voltage characteristic curve of the FS signal 114, and the coarse adjustment section 401 in the first adjustment process was performed.
To end. After time t4, the process proceeds to the fine adjustment section 402, which is the second adjustment process. At time t4, the offset voltage 122 is set to the voltage v3 between the voltages v5 and v2 by the voltage generation control signal 124. Next, at time t5, when the offset voltage 122 is increased to the voltage v4, RFS
The DC voltage of the signal 114 becomes the voltage r3. Then, when the offset voltage 122 is raised to the voltage v5 at the time t6, the DC voltage of the RFS signal 114 becomes the voltage r2. Then, at time t7, the offset voltage 122 is changed to the voltage v.
6, the DC voltage of the RFS signal 114 becomes the voltage r1
Becomes Then, at time t8, the offset voltage 12
When 2 is increased to the voltage v7, the DC voltage of the RFS signal 114 becomes the voltage r1. When the offset voltage 122 is increased to the voltage v8 at time t9, the RFS signal 114
Becomes a voltage r2. At this time, r4> r1, r
2> r1, the RFS signal 11 shown in FIG.
4, the offset voltage 122 is set by the voltage generation control signal 124 at time t10 so as to be a voltage v1 between the voltages v6 and v7, and the offset voltage 122 is set at time t11. The fine adjustment section 402, which is the second adjustment process, ends. After time t11,
Offset voltage 12 set at the end of fine adjustment section 402
2 is maintained.

In FIG. 4B, the change voltage of the offset voltage 122 in the coarse adjustment section 401, which is the first adjustment step, and in the fine adjustment section 402, which is the second adjustment step, is smaller in the fine adjustment section 402. But the fine adjustment section 402
To the last offset voltage 122 in the coarse adjustment section 401.
And a voltage between the voltage and a voltage obtained by adding the first change voltage to the voltage, the coarse adjustment section 4 which is the first adjustment process.
The adjustment can be performed even when the change voltage of the offset voltage 122 of the first adjustment process is equal to the change voltage of the offset voltage 122 of the fine adjustment section 402 which is the second adjustment process.

Although the offset voltage 122 in the fine adjustment section 402, which is the second adjustment process, is set to the voltage v1 between the voltages v6 and v7 in the same figure, it can be set to the voltage v6 or the voltage v7. is there.

Further, in FIG.
1 and the offset voltage 122 in the fine adjustment section 402
The voltage change direction is only the increasing direction, but may be the decreasing direction. Further, the direction of the voltage change of the offset voltage 122 may be increased or decreased or decreased and increased.

Next, the coarse adjustment section 401 in FIG.
The voltage v2 of the offset voltage 122 set first will be described with reference to FIG. FIG. 5 shows the focus error signal 126 when the focus servo loop in FIG. 1 is not closed, the offset voltage 122 is set to the reference voltage 501, the objective lens is brought close to the disk 101, and the output of the offset injection circuit. FIG. In the figure, the horizontal axis indicates the amount of defocus, and the vertical axis indicates the amplitude of the focus error signal 126 and the output 123 of the offset injection circuit. The offset injection circuit output 123 is obtained by transmitting the focus error signal 126 with the transmission gain of the offset injection circuit 117. In this figure, it is shown by the transmission gain of the phase inversion and attenuation. Voltage generation circuit 118 at time t1 in FIG.
The offset voltage 122 is set such that the offset voltage 122 observed at the offset injection circuit output 123 becomes a voltage between the positive peak p1 and the negative peak p2 of the waveform of the offset injection circuit output 123 in FIG. The voltage 122 is set. In this way, the focus offset can be stably adjusted without causing a defocus in the coarse adjustment section 401.

According to the configuration of the optical disc apparatus as the first embodiment of the present invention, after the first adjustment step (coarse adjustment step) of changing the output voltage of the voltage generation means with the first change voltage, A second adjustment step (fine adjustment step) of changing the output voltage of the voltage generating means with a second change voltage equal to the first change voltage or smaller than the first change voltage; Since the offset voltage is injected into the focus servo loop means so as to hold a voltage between two voltage values of the voltage that changes with the second change voltage in the second adjustment process, the focus offset voltage is Even for a disk with a narrow allowable range, the focus offset can be accurately adjusted in a short time and the disk can be reproduced stably.

Hereinafter, the configuration and operation of an optical disk device according to a second embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a block diagram showing a second embodiment of the optical disk apparatus of the present invention. Elements assigned the same numbers as those in FIG. 1 are the same as those in FIG. The components different from those in FIG. 1 are a clock recovery circuit 601 and a jitter detection circuit 602.
It is. The clock recovery circuit 601 outputs the reproduced RF signal 111
The clock 604 synchronized with. The jitter detection circuit 602 detects the amount of jitter, which is the time difference between the reproduced RF signal 111 and the clock 604, and inputs the amount of jitter to the control circuit 119 as a JITOUT signal 603 converted into a voltage.

The operation of FIG. 6 will be described below. Prior to that, the JITOUT signal 603 in FIG. 6 will be described.

First, the relationship between the JITOUT signal 603 and the byte error rate will be described with reference to FIG. FIG. 7 (a)
FIG. 7B is a characteristic diagram illustrating an example of a byte error rate when the offset voltage 122 is adjusted, and FIG. 7B is a characteristic diagram illustrating an example of the JITOUT signal 603 when the offset voltage 122 is adjusted. In FIG. 7A, the horizontal axis represents the offset voltage 122, and the vertical axis represents the byte error rate.
In (b), the horizontal axis is the offset voltage 122, and the vertical axis is J
It shows the DC voltage value of the ITOUT signal 603.

As in the case of the RFS signal 114 shown in FIG. 2, the lower the byte error rate when reading information from the disk, the more stable the reproduction can be performed. FIG. 7 (a)
, When the offset voltage 122 is gradually increased, the byte error rate decreases and reaches the minimum byte error rate e2 at a certain voltage v10, and when the offset voltage 122 is further gradually increased, the byte error rate starts increasing. . When the offset voltage 122 in FIG. 7B is v10, the JITOUT signal 603 is output.
Has a minimum value. That is, in this example, JITO
The offset voltage 122 that minimizes the DC voltage of the UT signal 603 may be adjusted to v10.

Therefore, when the offset voltage 122 is adjusted, the DC voltage of the JITOUT signal 60 has a U-shaped characteristic similarly to the case of the DC voltage of the RFS signal 114 shown in FIG. It is possible to adjust the focus offset by using the DC voltage of the RFS signal 114 and the method.

According to the configuration of the optical disk device as the second embodiment of the present invention, after the first adjustment step (coarse adjustment step) of changing the output voltage of the voltage generating means with the first change voltage, A second adjustment step (fine adjustment step) of changing the output voltage of the voltage generating means with a second change voltage equal to the first change voltage or smaller than the first change voltage; Since the offset voltage is injected into the focus servo loop means so as to hold one of the voltages that change with the second change voltage in the second adjustment process, the tolerance range of the focus offset voltage is narrow. As for, the focus offset can be accurately adjusted in a short time, and the disc can be reproduced stably.

Hereinafter, the configuration and operation of an optical disk device according to a third embodiment of the present invention will be described with reference to FIG.

FIG. 8 is a block diagram showing a third embodiment of the optical disk apparatus of the present invention. Elements denoted by the same reference numerals as those in FIGS. 1 and 6 are the same as those in FIGS. Figure 1,
A component different from FIG. 6 is a disc discriminating circuit 125. The disc discrimination circuit 125 outputs the focus error signal 1
26 and the reproduction RF signal 111, and disc type is discriminated, and a disc discrimination signal 128 is output to the control circuit 119.

The operation of FIG. 8 will be described below.

When the disc 101 is a CD, the disc discrimination circuit 125 discriminates the disc 101 from a CD, and performs focus offset adjustment using the RFS signal 114. The adjustment method in this case can be performed by the same method as described in the operation of the configuration diagram of FIG. On the other hand, if the disc 101 is a DVD, the disc discrimination circuit 125 discriminates the disc 101 from a DVD,
Focus offset adjustment is performed using the TOUT signal 603. The adjustment method in this case can be performed by the same method as described in the operation of the configuration diagram of FIG.

On the contrary, the disk 101 is
If it is determined that the disk 101 is a CD, the focus offset adjustment can be performed using the JITOUT signal 603 when the disc 101 is determined to be a CD.

According to the configuration of the optical disk device as the third embodiment of the present invention, after the first adjustment step (coarse adjustment step) of changing the output voltage of the voltage generation means with the first change voltage, A second adjustment step (fine adjustment step) of changing the output voltage of the voltage generating means with a second change voltage equal to the first change voltage or smaller than the first change voltage; Since the offset voltage is injected into the focus servo loop means so as to hold one of the voltages that change with the second change voltage in the second adjustment process, the tolerance range of the focus offset voltage is narrow. As for, the focus offset can be accurately adjusted in a short time, and the disc can be reproduced stably.

[0044]

According to the present invention, after the first adjustment step (coarse adjustment step) of changing the output voltage of the voltage generating means with the first change voltage, the output voltage is equal to or equal to the first change voltage. A second adjustment process (fine adjustment process) for changing the output voltage of the voltage generating means with a second change voltage smaller than the first change voltage is performed, and the second adjustment process uses the second change voltage in the second adjustment process. Since the offset voltage is injected into the focus servo loop means so as to hold one of the changing voltages, the focus offset can be adjusted accurately in a short time even for a disk with a narrow allowable range of the focus offset voltage. In addition, it is possible to provide an optical disk device for stably reproducing a disk.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical disc device as a first embodiment of the present invention.

FIG. 2 is a characteristic diagram illustrating measurement results of a byte error rate and an RFS signal with respect to an offset voltage according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram of an offset injection circuit and a voltage generation circuit as a first embodiment of the present invention.

FIG. 4 is a waveform chart showing an operation of offset adjustment according to the first embodiment of the present invention.

FIG. 5 is a waveform chart showing an output of an offset injection circuit according to the first embodiment of the present invention.

FIG. 6 is a configuration diagram of an optical disk device as a second embodiment of the present invention.

FIG. 7 is a characteristic diagram showing measurement results of a byte error rate and a JITOUT signal with respect to an offset voltage according to a second embodiment of the present invention.

FIG. 8 is a configuration diagram of an optical disc device as a third embodiment of the present invention.

FIG. 9 is a diagram illustrating the principle of focus error detection by the astigmatism method.

FIG. 10 is a characteristic diagram showing byte error rates with respect to offset voltages of different types of DVD disks and CD disks.

[Explanation of symbols]

101: disk, 102: disk motor, 103:
Motor driver, 104: optical pickup, 105: focus servo circuit, 106: tracking servo circuit, 107: read signal, 108: tracking error detection circuit, 109: focus error detection circuit, 11
0: RF amplifier circuit, 111: reproduced RF signal, 112:
Rotation control circuit, 113: LPF, 114: RFS signal,
115 demodulation circuit, 116 reproduction signal, 117 offset injection circuit, 118 voltage generation circuit, 119 control circuit, 120 focus switching signal, 121 switch
122: offset voltage, 123: offset injection circuit output, 124: voltage generation control signal, 125: disk discrimination circuit, 126: focus error signal, 127: tracking error signal, 128: disk discrimination signal, 60
1: clock recovery circuit, 602: jitter detection circuit, 60
3: JITOUT signal

Claims (5)

[Claims] 1. An optical disc apparatus for irradiating an information recording medium with laser light and reproducing information by reflected light of the laser light, comprising: a focus error signal detecting means for detecting a focus error signal; and a focus error signal detecting means. Focus servo loop means for performing focus servo based on a focus error signal from the apparatus; and voltage generating means for generating a voltage that changes stepwise as time passes and holding one of the voltages that change stepwise. And an injecting means for injecting the output of the voltage generating means into the focus servo loop means, wherein a first adjusting step of changing the output voltage of the voltage generating means with a first change voltage After the generation of the voltage at a second change voltage that is equal to or less than the first change voltage Performing a second adjustment step of changing the output voltage of the stage, and maintaining a voltage between two voltage values of the voltages that change with the second change voltage of the second adjustment step. An optical disk device characterized by injecting an offset voltage into said focus servo loop means. 2. An optical disk device according to claim 1, wherein a voltage obtained by adding said first change voltage to a last output voltage of said voltage generation means changed by said first change voltage; After presetting the output voltage of the voltage generating means to be a voltage between the last output voltage changed by the first change voltage and the voltage obtained by subtracting the first change voltage, the second output voltage The output voltage of the voltage generating means is changed by the change voltage, and an offset voltage is applied to the focus servo loop means so as to hold a voltage between two voltage values of the voltage changing by the second change voltage. An optical disk device characterized by being injected. 3. The optical disc device according to claim 1, wherein the output voltage of the voltage generating means observed at the output of the offset injecting means is the focus error observed at the output of the offset injecting means. An optical disk device, wherein the output voltage of the voltage generating means is set in advance so that the voltage becomes lower than the positive peak voltage of the signal, and then the output voltage of the voltage generating means is changed. 4. The optical disc device according to claim 1, wherein the output voltage of the voltage generating means observed at the output of the offset injection means is the focus error observed at the output of the offset injection means. An optical disk device characterized in that after setting an output voltage of said voltage generating means in advance so as to be higher than a negative peak voltage of a signal, the output voltage of said voltage generating means is changed. 5. The optical disk device according to claim 1, wherein at least a CD is used as the information recording medium.
An optical disc device characterized by being able to reproduce a DVD.