JP2001006197A - Disc reproducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suitably control tracking irrespective of an eccentric amount of a disk by altering responding characteristics of an actuator system in response to the eccentric amount of the disk. SOLUTION: A microcomputer 38 inputs a frequency signal having a predetermined frequency component of a tracking error signal from an LPF 32, and decides an eccentric amount of a disk 22 based on the frequency signal. If the eccentric amount exceeds a predetermined threshold value, a gain of a driver 3 is increased, and a gain of a driver 36 is decreased. Thus, responding characteristics (responding frequency band) of an actuator system is broadened. That is, if the eccentric amount of the disk 22 is large, the responding characteristics of the actuator are extended from the case that the eccentric amount is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk reproducing apparatus, and more particularly to, for example, a DVD (Digital Versatile Disc).
c) The present invention relates to a disc reproducing apparatus which is applied to a player or a CD (Compact Disc) player and reproduces a signal recorded on a disc by an optical pickup.

[0002]

2. Description of the Related Art When a signal is reproduced from a disk such as a DVD or a CD, an optical lens provided in an optical pickup must accurately follow a track formed on the disk surface. For this reason, in the conventional disk reproducing apparatus, the minute movement in the radial direction of the optical lens is controlled by an actuator system which responds to the high frequency component of the tracking signal. Further, the optical pickup itself is controlled by a thread system which responds to a low frequency component of the tracking error signal.

[0003]

However, in the prior art, since the response characteristics of the actuator system were not changed, there was a problem that the tracking could not be controlled well due to the eccentricity of the disk. In other words, if the response characteristic (response frequency band) of the actuator system is widened, the eccentricity of the disk can be followed even when the eccentricity of the disk is large, but tracking is lost in response to a scratch on the disk surface. On the other hand, if the response characteristic of the actuator system is narrowed, the disk is not affected by scratches on the disk surface, but cannot respond to a disk having a large eccentricity.

[0004] Therefore, a main object of the present invention is to provide a disk reproducing apparatus capable of appropriately controlling tracking regardless of the eccentricity of the disk.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an optical pickup provided with an optical lens, an actuator system for controlling the position of the optical lens based on a tracking error signal, and an eccentricity of a disk based on the tracking error signal. A disc reproducing apparatus, comprising: discriminating means for discriminating; and first changing means for changing a response characteristic of an actuator system according to a discrimination result of the discriminating means.

[0006]

The actuator system controls the position of the optical lens provided on the optical pickup based on the tracking error signal. On the other hand, the determining means determines the eccentricity of the disk based on the tracking error signal, and the first changing means changes the response characteristic of the actuator system according to the result of the determination by the determining means.

In one embodiment of the present invention, in the actuator system, the first generating means generates an actuator control signal based on the tracking error signal. Also,
First gain applying means applies a first gain to the actuator control signal. On the other hand, in the first changing unit, the first gain control unit controls the first gain according to the determination result. The discrimination means compares the eccentricity amount with a predetermined threshold value, and the first gain control means increases the first gain when the eccentricity amount is larger than the predetermined threshold value.

[0008] In one aspect of the present invention, the thread system controls the position of the optical pickup based on the tracking error signal. In the thread system, the second generation means generates a thread control signal based on the tracking error signal, and the second gain control means applies a second gain to the thread control signal. In the second changing unit, the second gain control unit controls the second gain according to the result of the determination by the determination unit.
The discrimination means compares the amount of eccentricity with a predetermined threshold, and the second gain control means reduces the second gain when the amount of eccentricity is larger than the predetermined threshold.

[0009]

According to the present invention, the amount of eccentricity of the disk is determined, and the response characteristic of the actuator system is changed in accordance with the result of the determination. Therefore, tracking is appropriately controlled regardless of the amount of eccentricity of the disk. can do.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0011]

Referring to FIG. 1, a DVD player 10 of this embodiment includes an optical pickup 12 provided with an optical lens 14. The optical lens 14 is supported by the actuator 16, and the laser light output from the laser diode 18 is applied to the recording surface of the disk 22 through the optical lens 14. Light reflected from the disk surface passes through the same optical lens 14 and enters the photodiode 20. As a result, a signal corresponding to the reflected light is output from the optical pickup 12.

The signal output from the optical pickup 12 is applied to a TE detection circuit 26. TE detection circuit 26
Detects tracking deviation based on the above signal,
A tracking error signal (TE signal) is output. TE
The signal is input to the actuator phase compensation filter 28, and the actuator phase compensation filter 28 generates a signal for stabilizing the actuator servo, that is, an actuator control signal. The driver 30 applies a predetermined gain to the actuator control signal output from the actuator phase compensation filter 28 and outputs the signal to the actuator 16. The actuator 16 is driven by an actuator control signal to which a predetermined gain has been applied, whereby the optical lens 14 moves in the radial direction of the disk 22.

The output of the actuator phase compensation filter 28 is also supplied to a thread phase compensation filter 34 via an LPF 32. Thread phase compensation filter 34
Generates a thread control signal based on an input from the LPF 32. The generated thread control signal is the driver 3
6 and receives a predetermined gain. The sled control signal provided with the predetermined gain is output to the sled motor 24, and the sled motor 24 rotates in response to such a sled control signal. Thread phase compensation filter 34
Attenuates frequency components related to the eccentricity of the disk 22. In other words, it is difficult to synchronize the operation of the actuator 16 with the operation of the sled motor 24,
When the sled motor 24 is driven based on the eccentric component of 2, the movements of the actuator 16 and the sled motor 24 vary. For this reason, the eccentric component is attenuated from the output of the LPF 32 by the thread phase compensation filter 34. The sled motor 24 moves the optical pickup 12 in the radial direction of the disk 22 in response to such a sled control signal.

The actuator phase compensation filter 2
8, a driver 30 and the actuator 16 form an actuator system, and the actuator phase compensation filter 28, LPF 32, thread phase compensation filter 3
4. A thread system is formed by the driver 36 and the thread motor 24.

The frequency signal output from the LPF 32 is
The data is also input to the microcomputer 38 via an A / D converter (not shown). The microcomputer 38 starts the processing of the flowchart shown in FIG. 2 simultaneously with the start of the reproduction of the disk 22, and controls the gains of the drivers 30 and 36 based on the frequency signal input from the A / D converter.

The microcomputer 38 first initializes the count value N of the counter 38a in step S1, and then in step S3 sets the maximum data value D _MAX and the minimum data value D _MIN to “127” and “−128”, respectively. set.
In step S5, the current count value N is set to the maximum count value N
Compare with _MAX . Here, if N < _NMAX , the microcomputer 38 proceeds from step S5 to step S7, and takes in the current data value of the frequency signal. The microcomputer 38 subsequently compares the current data value and the maximum data value D _MAX in step S9. Then, the process proceeds directly to step S13 if the current data value ≦ D _MAX, if the current data value> D _MAX, the process proceeds after updating the maximum data value D _MAX to the current data value in step S11 to step S13.

In step S13, the current data value is compared with the minimum data value D _MIN . If the current data value ≧ D _MIN , the process directly proceeds to step S17, where the counter 38a
It is incremented, but if the current data value <D _MIN, increments the counter 38a in step S17 after updating the D _MIN to the current data value in step S15. After finishing the process in step S17, the microcomputer 38 returns to step S5. In this way, until the count value N reaches the maximum count value N _MAX, step S7~S
Step 17 is repeated.

The level of the frequency signal output from the LPF 32 changes according to the eccentricity of the disk 22, as shown in FIG. On the other hand, the maximum count value N _MAX is
It is set corresponding to the second rotation period _Td . Count value N
Reaches the maximum count value _NMAX , the microcomputer 38 proceeds from step S5 to step S19, and obtains the eccentricity amount P according to equation (1).

[0019]

[Number 1] P = D _MAX -D _MIN microcomputer 38 further the calculated eccentricity P is compared with a threshold value P _TH (= 255) at step S21. And P
If> P _TH , a high-level switching signal is output in step S23, and if P ≦ P _TH , a low-level switching signal is output in step S25. Microcomputer 3
8 then terminates the process.

Referring to FIG. 4, drivers 30 and 36
Will be described. In the driver 30, the resistor R1
And one end of the resistor R2 are connected via a switch SW1. The other end of the resistor R1 and the other end of the resistor R2 are commonly connected to one input terminal (inverting terminal) of the operational amplifier OP1. The other end of the resistor R1 is connected to the output terminal of the operational amplifier OP1 via the resistor R3. Further, one end of the resistor R2 is connected to the actuator phase compensation filter 28, and the other input end of the operational amplifier OP1 is grounded.

On the other hand, in the driver 36, one end of the resistor R4 and one end of the resistor R5 are connected via the switch SW2, and the other end of the resistor R4 and the other end of the resistor R5 are connected to the output terminal of the operational amplifier OP2. Is done. Operational amplifier OP2
Is connected to one end of the resistor R5 and the other end of the resistor R6, and the other input terminal of the operational amplifier OP2 is grounded. Further, one end of the resistor R6 is connected to the thread phase compensation filter 34.

The switching signal output from the microcomputer 38 is supplied to a switch SW1 provided in the driver 30 and a switch SW2 provided in the driver 36. Each of the switches SW1 and SW2 is turned on when the switching signal is at a high level, and is turned off when the switching signal is at a low level.

However, the configurations of the drivers 30 and 36 are different from each other as described above. Therefore, the gain β1 of the operational amplifier OP1 is expressed by Expression 2 when the switch SW1 is on, and is expressed by Expression 3 when the switch SW1 is off. On the other hand, the gain β2 of the operational amplifier OP2 is expressed by Expression 4 when the switch SW2 is on, and is expressed by Expression 5 when the switch SW2 is off.

[0024]

## EQU2 ## β1 = (R1 + R2) · R3 / R1 · R2

[0025]

## EQU3 ## β1 = R3 / R2

[0026]

## EQU4 ## β2 = R4 · R5 / (R4 + R5) · R6

[0027]

Β2 = R5 / R6 If the eccentricity of the disk 22 is large, the switches SW1 and SW2 are turned on. As a result, the gain β1 of the driver 30 is greater than when the switch SW1 is off, and the gain β2 of the driver 36 is greater than the switch SW1.
2 is smaller than in the off state.

The transfer function of the actuator phase compensation filter 28 is C _ACT (S), the transfer function of the driver 30 is G _ACT (S), the transfer functions of the LPF 32 and the thread phase compensation filter 34 are C _SLED (S), _Assuming that the transfer function of the driver 36 is G _SLED (S), FIG. 1 is equivalent to FIG. In FIG. 5, xa denotes the actuator 16
Xs indicates the amount of movement of the optical pickup 12, and as a result, xt indicates the amount of movement of the optical lens 14. Further, e indicates a disturbance including eccentricity, and xd indicates a tracking shift.

For this reason, the transfer characteristic (transfer characteristic of the actuator system) when xd is input and xa is output is represented by Equation 6, and the transfer characteristic (thread) when xd is input and xs is output. The transfer characteristic of the system) is expressed by Expression 7.

[0030]

Xa = xd · C _ACT (S) · G _ACT (S)

[0031]

Xs = xd · C _ACT (S) · C _SLED (S) · G _SLED (S) When the disturbance e is included, xa is expressed by Expression 8, and xs
Is represented by Equation 9.

[0032]

Xa = e · C _ACT (S) · G _ACT (S) / [1+
C _ACT (S) ｛G _ACT (S) + C _SLED (S) · G
_SLED (S)｝]

[0033]

Xs = e · C _ACT (S) · C _SLED (S) · G
_SLED (S) / [1 + C _ACT (S) ｛G _ACT (S) + C _SLED
(S) · G _SLED (S)｝] The transfer characteristic shown in _Equation 6 is represented by the curve A in FIG. 6A and FIG. 7A, and the transfer characteristic shown in Equation 7 is shown in FIG. In the case of being represented by the curve B of FIG. 7 (A), the transfer characteristic shown in Equation 8 is represented by the curve C of FIG. 6 (B) and FIG. 7 (B), and the transfer characteristic shown in Equation 9 is shown in FIG. And a curve D in FIG.

Here, when G _ACT (S) increases, curve A shifts to curve A ′ as shown in FIG.
Further, as shown in FIG. 6B, the curve C shifts to the curve C ′, and the curve D shifts to the curve D ′. That is, G
The response characteristic (response frequency band) of the actuator system becomes wider than before _ACT (S) increases, and the response characteristic of the thread system shifts to a lower band. On the other hand, when G _SLED (S) decreases, curve B shifts to curve B ′ as shown in FIG. Further, as shown in FIG. 6B, the curves C and D shift to the curves C ″ and D ″, respectively. That is, even when G _SLED (S) decreases, the response characteristic (response frequency band) of the actuator system becomes wide, and the response characteristic of the thread system shifts to a lower range.

As described above, when the amount of eccentricity of the disk 22 is large, the microcomputer 38 outputs a high-level switching signal, and as a result, the gain β1 increases and the gain β2 decreases. Gain β1 is G _ACT (S)
Since the corresponding gain β2 corresponds to G _{SLE D} (S),
When the eccentric amount of the disk 22 is large, G _ACT (S) increases and G _SLED (S) decreases. The response characteristic (response frequency band) of the actuator system becomes wider than the curves C ′ and C ″, and the response characteristic of the thread system also shifts to a lower range than the curves D ′ and D ″.

According to this embodiment, when the eccentricity of the disk is large, the response characteristics of the actuator system are expanded. Therefore, even when a disk with a large eccentricity is reproduced, the actuator system is quickly eccentric. Respond to For this reason, tracking deviation can be prevented. When the eccentricity of the disk is large, the response characteristic of the thread system shifts to a lower range, so that the optical pickup can be prevented from being shaken due to the eccentricity.

On the other hand, if the eccentricity of the disk is small, the response characteristics of the actuator system return to the original, so that the actuator system does not respond to scratches on the disk surface.
Good tracking becomes possible. When the eccentricity of the disk is small, the response characteristic of the thread system also returns to the original, so that the pull-in time after the search operation does not become long.

In this embodiment, both the gains β1 and β2 are switched according to the amount of eccentricity of the disk 22. However, the response characteristics of the actuator system and the thread system are changed only by switching one of the gains β1 and β2. Therefore, one of the switches SW1 and SW2 may be omitted, and the other switch may be controlled by a switching signal from the microcomputer 38.

In this embodiment, the actuator system and the thread system are constituted by a filter and a driver, but these tracking systems are constituted by a DSP (Digital).
Needless to say, it may be constituted by a signal processor.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart showing a part of the operation of the embodiment in FIG. 1;

FIG. 3 is an illustrative view showing one portion of an operation of the embodiment in FIG. 1;

FIG. 4 is a circuit diagram showing a driver.

FIG. 5 is a block diagram equivalent to the embodiment of FIG. 1;

FIG. 6A is a graph showing transmission characteristics of an actuator system and a thread system that do not include a disturbance, and FIG. 6B is a graph showing transmission characteristics of an actuator system and a thread system that include a disturbance.

7A is a graph showing transmission characteristics of an actuator system and a thread system that do not include a disturbance, and FIG. 7B is a graph showing transmission characteristics of an actuator system and a thread system that include a disturbance.

[Explanation of symbols]

 Reference Signs List 10 DVD player 12 Optical pickup 14 Optical lens 16 Actuator 26 TE detection circuit 28 Actuator phase compensation filter 32 LPF 34 Thread phase compensation filter 30, 36 Driver 38 Microcomputer

Claims (5)

[Claims] 1. An optical pickup provided with an optical lens, an actuator system for controlling the position of the optical lens based on a tracking error signal, a discriminating means for discriminating an eccentricity of a disc based on the tracking error signal, and A disk reproducing apparatus comprising: a first changing unit that changes a response characteristic of the actuator system according to a result of the determination by the determining unit. 2. The actuator system according to claim 1, wherein the actuator system includes: a first generating unit that generates an actuator control signal based on the tracking error signal; and a first gain applying unit that applies a first gain to the actuator control signal. 2. The disk reproducing apparatus according to claim 1, wherein the first changing unit includes a first gain control unit that controls the first gain according to the determination result. 3. The discriminating means includes a comparing means for comparing the eccentricity with a predetermined threshold, and the first gain control means increases the first gain when the eccentricity is larger than the predetermined threshold. 3. The disk reproducing apparatus according to claim 2, further comprising a gain increasing unit. 4. A sled system for controlling a position of the optical pickup based on the tracking error signal, wherein the sled system generates a sled control signal based on the tracking error signal, and 2. The method according to claim 1, further comprising: a second gain applying unit that applies a second gain to the thread control signal, wherein the second changing unit includes a second gain controlling unit that controls the second gain according to the determination result. 2
The disc reproducing device according to the above. 5. The discriminating means includes a comparing means for comparing the eccentricity amount with a predetermined threshold value, and the second gain control means reduces the second gain when the eccentricity amount is larger than the predetermined threshold value. 5. The disc reproducing apparatus according to claim 4, further comprising a second gain decreasing means.