JP2001023194A - Optical disk reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make more easily performable focusing without introducing a disturbance by synthesizing the level of the detection signal of a position error with the level of the detection signal of a current position error for automatically focusing. SOLUTION: After a data sampling program is executed, a peak detection program, an average value calculation program, and a level judgment program are successively called, and data on the amount of offset obtained when the execution of the average value calculation program is completed is set to a register 105 in an automatic focus control loop. At the same time, a switching signal is transmitted from an MPU 103 to a switching circuit 62 via an interface 106, and the switching circuit is connected to the side of a phase compensation loop filter 62 for initiating just focus control, thus feeding an analog voltage corresponding to the amount of offset to a signal level synthesis circuit 59 by a D/A converter 102 and forming the automatic focusing servo loop.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus, and more particularly, to a focusing servo mechanism of an optical disk reproducing apparatus, which performs focusing (automatic focus control) with a simpler circuit without injecting disturbance.
The present invention relates to an improvement in a servo mechanism that can improve the S / N ratio and eliminate the need for readjustment when exchanging an external pickup unit or the like.

[0002]

2. Description of the Related Art In recent years, in a CD-ROM device,
From double speed to 32 times speed or more, the data read speed is rapidly increased, so that
Data reading is required in a speed range of 1 × to 32 × or higher. Also, in the optical disk storage device, the storage density is twice, four times, six times,
It is increasing rapidly by eight times. In this type of optical disc reproducing apparatus, a very accurate focusing servo is required. FIG. 5 is an explanatory diagram of the focusing servo mechanism.

In FIG. 5, 1 is a focusing servo mechanism, 2 is an optical disk, 3 is a rotating mechanism, 4 is an optical system, and a laser unit 41 for irradiating the optical disk 2 with laser light is provided. And a half mirror 42. 5 is a focusing servo circuit,
Division photodetector (pickup) 51, focus position error generation circuit 52, level detection circuit 53, response waveform generation circuit 54, amplitude detection circuit 55, automatic focus adjustment controller 56, focus servo controller 57, offset amount adjustment circuit 58, signal level Level synthesizing circuit 59 for subtracting and synthesizing the signal, a disturbance oscillator 60, a signal level synthesizing circuit 61 for adding and synthesizing the signal level, a phase compensation loop filter (a so-called CR low-pass filter).
62, a search waveform generating circuit 63, a switching circuit 64, a drive amplifier 65, and a focus position adjusting mechanism 66.

Here, the four-divided photodetector 51
The sensor area is equally divided into four, and a detection signal is generated in each area. This is because the reflected light of the light beam from the optical disk 2 is received from the half mirror 42, the amount of light received on each area is converted into an electric signal, and the sum signal of the opposing sensor areas in different directions is detected by the detection signal A. , B, and outputs the detection signals A, B to the focus position error generation circuit 52.

The focus position error generation circuit 52 receives a sum signal of the detection signals A and B as a detection signal RF (a detection signal corresponding to the amount of light received by receiving a reflected light from the optical disk by a photodetector, This is a signal corresponding to the reflection level of the light reflected from the optical disk.
(Hereinafter, referred to as an RF detection signal RF).
A position error detection signal FE (FE: abbreviation for focus error) is generated as a difference signal of B. Of these signals,
The position error detection signal FE is supplied to a signal level synthesizing circuit 59,
The signal is applied to a phase compensation loop filter 62 via a signal level synthesis circuit 61. Then, the phase compensation loop filter 6
2, the low-frequency component is extracted, and in the state of the automatic focus control (hereinafter referred to as "just focus control"), the low-frequency component is added to the drive amplifier 65, and the output in the direction of correcting the focus error according to the level is the focus position. The laser unit 4 added to the adjustment circuit 66
1 is driven, the level of the position error detection signal FE decreases, and the focus position is automatically adjusted so as to be the in-focus position.
Note that the just focus control is to control in a direction in which the position error is eliminated according to the level of the position error detection signal FE.

On the other hand, the RF detection signal RF is applied to a level detection circuit 53, and it is detected whether or not it has entered the just focus control range based on the level of the RF detection signal RF. When the RF detection signal RF reaches the just focus control level, it is detected and the detection signal is input to the focus servo controller 57. The focus servo controller 57 receives the detection signal from the level detection circuit 53 and switches the switching circuit 64 to the phase compensation loop filter 62.
To the drive amplifier 65. This results in just focus control.

At first, the switching circuit 64 is a search waveform generating circuit 63 for generating a lamp voltage for searching the just focus point by the focus servo controller 57 (this circuit is a so-called lamp voltage generating circuit, In order to search for the focal position, a signal for continuously moving the focal position toward or away from the disk is generated.) The focus servo controller 57 sets the search waveform according to the rotational driving of the optical disk 2. The generation circuit 63 is activated to generate a ramp voltage to drive the drive amplifier 65. As a result, the drive amplifier 65 drives the focus position adjusting mechanism 66,
By moving a focusing lens built in the laser unit 41 by the focus position adjusting mechanism 66 in accordance with the lamp voltage, the focal position of the laser light emitted from the laser unit 41 to the optical disc 2 is raised from the lowest point. Then, the level of the RF detection signal RF increases and enters a state in which just focus control can be performed in accordance with the detection signal of the level detection circuit 53 for detecting the level. At this time, the switching of the switching circuit 64 by the focus servo controller 57 is performed. Is performed.

The pickup unit has a four-divided photodetector, a laser unit 41 having a laser light source and a lens inserted in the optical path of the laser light source, and a focus position adjusting mechanism 66 for moving the lens back and forth. By moving the focusing lens movable along the optical axis of the laser light of the laser light source provided in the laser unit 41 by the focus position adjusting mechanism 66, the laser light is output from the laser light source to the irradiation surface of the optical disk 2. The focal position of the laser beam can be moved back and forth. Here, either the drive amplifier 65 or the focus position adjusting mechanism 66 receives the signal synthesized from the signal level synthesizing circuit 61 via the phase compensation loop filter 62, and receives the position error detection signal FE.
A so-called negative feedback control is formed, which generates an output for driving the focusing lens in the direction of decreasing.

Therefore, when the switching circuit 64 is switched to the phase compensation loop filter 62, the focusing servo mechanism 1 starts just focus control. At this time, the automatic focus adjustment controller 56 receiving the signal from the focus servo controller 57 activates the disturbance oscillator 60. The output signal of the disturbance oscillator 60 is, for example, 1 k
A triangular wave of about Hz is generated as a disturbance signal. The disturbance signal passes through a signal level synthesizing circuit 61 and is output from a focus position error generating circuit 52 as a position error detection signal F.
E, which is added to the phase compensation loop filter 62, and the drive amplifier 65 controls the focus position adjusting mechanism 66 in response to this, so that the laser unit 4
The focal position of the laser light irradiated from 1 moves slightly up and down, and the RF detection signal RF at that time is input to the response waveform generation circuit 54. And here the response waveform is generated,
The amplitude is detected by the amplitude detection circuit 55 and input to the automatic focus adjustment controller 56. The focus automatic adjustment controller 56 estimates an unbalance amount of the sensitivity of the four-divided sensor area of the four-divided photodetector 51 from the amplitude of the response waveform and outputs a signal for generating an offset corresponding to the unbalance amount to the offset amount. The signal is sent to the adjustment circuit 58. Then, the disturbance signal of the disturbance oscillator 60 is stopped.

The offset amount adjusting circuit 58 generates an output corresponding to the offset amount in accordance with the input signal, and the output is applied to a signal level synthesizing circuit 59 as a negative input (-), and the signal level synthesizing is performed. The position error detection signal FE is combined with the position error detection signal FE by the circuit 59 and the level of the position error detection signal FE is subtracted by the offset (the result is added when the offset amount is negative). Thereby, the unbalance amount of the sensitivity of the sensor area is corrected. Then, the subtracted position error detection signal FE is added to the phase compensation loop filter 62 to form an automatic focusing servo loop. As a result, in the focusing servo mechanism 1, an output to the just-focus position is generated from the phase compensation loop filter 62 in accordance with the position error detection signal FE, and the offset amount adjustment circuit 58
The laser beam emitted from the laser unit 41 is focused on the optical disc 2 by correcting the detected position shift caused by the sensitivity imbalance by the output of the offset amount from.

[0011]

FIG. 6 is a diagram illustrating the detection signals A and B of the four-divided photodetector 51 and the amount of offset. The level of the detection signal A is large, and the level of the detection signal B is low. It is a small case. The vertical axis is the voltage [V] indicating the detection level, and the horizontal axis is the distance [μm] from the reference position to the focal point. Thereby, the detection signals A and B
The zero-cross point C of the position error detection signal FE, which is a difference signal from the detection signal A, shifts to the right side of the drawing with respect to the peak position P of the RF detection signal RF, which is the sum signal of the detection signals A and B.
If the detection signals A and B are opposite, it shifts in the opposite direction. By the way, in the conventional focus control as described above, just focus setting of the light source for the optical disc cannot be performed unless the focus control loop enters the just focus control. However, when receiving the external vibration, the light receiving position of the four-segment photodetector 51 shifts, so that the automatic focusing servo loop cannot be maintained in the jazz focus control.

In order to form an automatic focusing servo loop, it is necessary to set an offset amount.
Therefore, a circuit for generating a disturbance signal is indispensable. Therefore, it is necessary to adjust the level of the disturbance signal so that the automatic focusing servo loop does not deviate. Therefore, it becomes difficult to adjust the offset amount. In addition, in the vicinity of the focus point where the signal waveform for searching the Justov focal position is generated, the level of the response waveform to the disturbance signal becomes small. Is dependent on the four-segment photodetector 51 and requires re-adjustment when parts are replaced. Moreover, the adjustment takes time. An object of the present invention is to solve such problems of the prior art, and it is possible to perform focusing with a simpler circuit without disturbing injection, to improve an S / N ratio, and to improve external An object of the present invention is to provide an optical disk reproducing apparatus that does not require readjustment when a pickup component or the like is replaced.

[0013]

A feature of an optical disk reproducing apparatus for achieving the above object is that a reflected light from an optical disk is received by a photodetector, and a detection signal of a received light amount corresponding to the received light amount and a focus position error. And a focus servo controller switches to an automatic focus loop in accordance with the level of the detection signal of the amount of received light, and controls in a direction in which the position error is eliminated in accordance with the detection signal of the position error. An optical disc reproducing apparatus having a focus servo mechanism for automatically focusing laser light from a laser light source with respect to an optical disc; and a signal generating circuit for generating a signal for advancing or retreating a focal position of the laser light with respect to the optical disc. ,
A maximum value detection circuit that detects the maximum value of the detection signal of the received light amount, and a level holding circuit that holds a level of the position error detection signal at this time according to the detection signal from the maximum value detection circuit. The focus servo controller drives the signal generation circuit to cause the maximum value detection circuit to detect the maximum value without switching to the automatic focus loop, and then performs control to switch to automatic focus control. The level of the position error detection signal held in the holding circuit and the level of the current position error detection signal are combined to perform automatic focusing. According to another aspect of the present invention, in the above-mentioned optical disc reproducing apparatus, a level holding circuit is provided to detect a focus position error when a detection signal corresponding to a received light amount is at a maximum value without switching to an automatic focus loop. Is taken as an offset amount and held in a level holding circuit in advance, and the held level is used in the just focusing servo state to automatically focus.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical disk focus servo mechanism described in the prior art, that is, a photodetector receives reflected light from an optical disk, generates an RF detection signal RF and a position error detection signal FE, and performs RF detection. The focus servo controller switches to the automatic focus loop in accordance with the level of the signal RF and enters the automatic focus control. The focus position of the laser light is slightly moved in accordance with the position error detection signal FE, and the light from the laser light source is moved to the optical disk. In the focus servo mechanism that automatically focuses on the focus, the maximum peak position of the RF detection signal RF corresponds to the focus position. Therefore, if the state of the automatic focus control is entered near the maximum peak position, the automatic focus is controlled by the automatic focus loop control. Matching is possible. Note that the detection signal R
At the focal point position corresponding to the maximum peak position of F,
The level of the position error detection signal FE should originally be “0”, and the difference from “0” is an offset generated due to the imbalance in sensitivity of the sensor area.

As a specific example of the level holding circuit, for example, a storage circuit for storing a level can be used. In this case, the level of the position error detection signal FE is stored corresponding to the maximum peak position of the RF detection signal RF, and the level stored in the just focusing servo state is used as an offset amount to calculate the position error detection signal FE. Can be combined into levels. Further, the maximum value detection circuit may be a maximum peak value and a minimum peak value detection circuit, and a circuit holding an average value of the maximum peak and the minimum peak value may be used as a specific example of the level holding circuit. In this case, the maximum peak value and the minimum peak value of the level of the position error detection signal FE are detected, the average value thereof is calculated, and this is combined with the level of the position error detection signal FE as an offset amount. I have.

Since the amount of displacement of the zero-cross point of the position error detection signal FE corresponds to the offset generated due to the imbalance in the sensitivity of the sensor area, in the latter case,
Offset correction can be performed by shifting the zero cross point to the position of the average of the maximum peak value and the minimum peak value of the level of the position error detection signal FE. As described above, according to the present invention, the level of the detection signal for the focus position error when the detection signal corresponding to the received light amount is the maximum value is sampled as the offset amount without switching to the automatic focus loop by providing the level holding circuit. The level is held in a level holding circuit in advance, and the held level is used in the just focusing servo state to automatically focus. In the above two cases, the storage of the offset amount or the calculation of the average value based on the position error detection signal FE is performed when the automatic focusing servo is not performed. Thus, there is no influence of disturbance noise, and no disturbance oscillator is required. As a result, focusing can be performed with a simpler circuit without injection of disturbance, the S / N ratio can be improved, and readjustment is not required when external pickup components are replaced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, the same components as those in FIG. 5 are denoted by the same reference numerals. The description of the components will be omitted. In FIG. 1, reference numeral 10 denotes a focusing servo mechanism.
0, the response waveform generation circuit 54, the amplitude detection circuit 55, and the focus automatic adjustment controller 56 in FIG.
Is not provided. Instead, a maximum value detection circuit 11 and a level storage circuit 12 are provided. Also,
A focus servo controller 570 is provided instead of the focus servo controller 57. The focus servo controller 570 sends an automatic focusing servo OFF control signal SOFF (hereinafter, referred to as a servo OFF control signal SOFF) to the level detection circuit 53 and the level storage circuit 12 in addition to the processing functions of the focus servo controller 57 in FIG. I do. The level detection circuit 53 receiving the servo OFF control signal SOFF stops its operation. Further, the level storage circuit 12 which has received the servo OFF control signal SOFF is set to a state in which the input signal is stored.

The focus servo controller 570 includes:
First, a servo OFF control signal SOFF is generated, and an offset value is collected and stored in the level storage circuit 12 in a state where the focus control is not performed (hereinafter referred to as a focusing servo OFF state). Perform control to enter. The maximum value detection circuit 11 is a circuit that receives the RF detection signal RF output from the focus position error generation circuit 52 and detects the maximum value thereof. For example, a hold circuit that holds the immediately preceding voltage and a hold circuit that holds this voltage It comprises a circuit and a comparator for comparing the current voltage with the voltage of the hold circuit, and generates a detection signal when the current voltage falls below the immediately preceding voltage. Then, the voltage value held by the hold circuit is
Reset is performed by the detection signal, the state becomes the expected state, and only the detection signal is output. Note that this circuit does not react to an instantaneous level drop such as noise.

The level storage circuit 12 is a so-called sample-and-hold circuit, and receives the position error detection signal FE output from the focus position error generation circuit 52 and receives the servo OFF control signal SOFF. The current level of the position error detection signal FE is stored in accordance with the detection signal from the CPU 11. In addition, servo OF
When the F control signal SOFF is not received, the stored level is output according to the detection signal from the maximum value detection circuit 11. Note that the output of the level stored in the level storage circuit 12 is not a detection signal from the maximum value detection circuit 11 but a control signal from the focus servo controller 570 to the switching circuit 64 in accordance with switching to just focus control. The reception may be performed as shown by a dotted line. In short, the output of the held level may be performed in the just focus control state.

Next, the focus servo operation of the focusing servo mechanism 10 will be described. First, the focus servo controller 570 outputs the servo OFF control signal SOFF
And drives the search waveform generation circuit 63. As described with reference to FIG. 5, initially, the switching circuit 64
The focus servo controller 570 sets the search waveform generation circuit 63 side. The focus servo controller 570 activates the search waveform generation circuit 63 to generate a ramp voltage and drive the drive amplifier 65.
At this time, the optical disk 2 may be rotating,
It does not have to rotate.

The drive amplifier 65 drives a focus position adjusting mechanism 66, and the focus of the laser beam emitted from the laser unit 41 to the optical disk 2 by the focus position adjusting mechanism 66 via the drive amplifier 65 in accordance with the lamp voltage. Raise the position from the lowest point. At this time, the level detection circuit 53 outputs the servo OFF control signal SOFF
, The operation of the switching circuit 64 is not switched to the just focus control. When the focus position of the laser beam is moved from the lowermost point to the uppermost point and one search (or a plurality of searches) is completed, the maximum value detection circuit 11 detects the RF detection signal RF near the just focus point. The maximum value is detected, and the level storage circuit 12 receives this detection signal. As a result, the level of the position error detection signal FE at this time is stored in the level storage circuit 12.

Next, the focus servo controller 57
A value of 0 stops the servo OFF control signal SOFF and drives the search waveform generation circuit 63. At this time, the level detection circuit 53 is activated. The level storage circuit 12
Are set to output the stored level. Therefore, the focus servo controller 570 switches the switching circuit 64 to the just focus control in response to the detection signal of the level detection circuit 53 that detects the level of the RF detection signal RF, that is, the connection to the phase compensation loop filter 62 is performed. Will be Then, the offset value stored in the level storage circuit 12 is output to the signal level synthesis circuit 59 in response to the detection signal of the maximum value detection circuit 11 or the switching signal to the just focus control. As a result, an automatic focusing servo loop is formed, and the phase compensation loop filter 62 generates an output corresponding to the just focus position according to the position error detection signal FE.
At this time, the shift of the detection position due to the imbalance of the respective sensitivities of the sensor areas of the four-divided photodetector 51 is corrected by the output of the offset amount from the level storage circuit 12, and the irradiation laser light from the laser unit 41 is changed. The irradiation surface of the optical disk 2 is focused.

FIG. 2 is an explanatory diagram of the operation, and FIG.
FIG. In the above embodiment, the offset amount (offset level) stored at the maximum value of the RF detection signal RF detected by the maximum value detection circuit 11
Becomes ΔOF. Since the just focus position corresponds to the maximum peak position P, if the level is subtracted from the position error output FE by ΔOF, the position P of the maximum peak value becomes the “0” level of the position error output FE.
Automatically set to just focus position.

FIG. 3 shows another embodiment, in which a maximum / minimum peak detection circuit 11a for the level of the position error detection signal FE is provided in place of the maximum value detection circuit 11 of FIG. Minimum position error detection signal F
An average value detection circuit 12a for calculating or detecting the average value of the peak level of E is provided. The average value detection circuit 12a has a hold circuit that receives the maximum and minimum peak levels output from the maximum and minimum peak detection circuits 11a and holds these levels, similarly to the level storage circuit 12, and outputs the servo OFF control signal SOFF. In response, the maximum and minimum peak levels are held in each hold circuit, and the average value of the held voltage levels is output when the servo OFF control signal SOFF is stopped.

This average value is output to the signal level synthesizing circuit 59 as an offset amount, and is output to the position error detection signal FE.
Is subtracted from the average value. As a result, an automatic focusing servo loop is formed, and the position error detection signal FE
, The phase compensation loop filter 62 generates an output at the just focus position. Note that the average value held in the average value detection circuit 12a is determined by the servo OFF
When the control signal SOFF is received, the previous hold value is reset. As the operation, the maximum peak level P1 (see the vertical axis) and the minimum peak level P2 (see the vertical axis) are detected in the position error detection signal FE in FIG. 2, and the average level is offset by Δof = (P1 + P
2) Output as / 2. The vicinity of the position P of the maximum peak value corresponds to the “0” level of the position error detection signal FE, and is automatically set to the just focus position. Note that the focus servo controller 57
The focusing servo operation of 0 is the same as in FIG.

The focusing servo mechanism 10a shown in FIG.
Is an example in which the level detection circuit 53, the servo focus controller 570, the maximum / minimum peak detection circuit 11a, and the average value detection circuit 12a in FIG. 3 realize their respective functions by the MPU and the program processing executed by the MPU. It is. Therefore, the level detection circuit 5 of FIG.
3. An offset setting control device 100 is provided in place of the servo focus controller 570, the maximum / minimum peak detection circuit 11a, and the average value detection circuit 12a. This device 1
00 and the focus position error generation circuit 52,
An A / D conversion circuit (A / D) 101 for converting an analog value into a digital value is provided. Between the device 100 and the signal level synthesizing circuit 59, a digital value is converted into an analog value. A D / A conversion circuit (D / A) 102 is provided.

Offset setting control data processing device 100
Has an MPU 103, a memory 104, a register 105 for setting an offset amount, and an interface 106, which are interconnected by a bus 107. The memory 104 stores a focus servo processing program 110, a data collection program 111, a peak detection program 112, and an average value calculation program 11
3, and the level determination program 114 are stored,
A work area 115 is provided. The search waveform generation circuit 63 is activated via the interface 106. Here, the focus servo processing program 110 and the data collection program 111 are programs for realizing the function of the focus servo controller 570, and the peak detection program 112 includes a maximum / minimum peak value detection circuit 11
The average value calculation program 113 is a program for implementing the functions of the average value detection circuit 12a, and the level determination program 1
14 is a program for realizing the function of the level detection circuit 53.

MPU 1 of offset setting control device 100
03 executes a focus servo processing program 110 in response to a start signal from an external system control device. 10
Reference numeral 8 denotes a start signal input terminal. When the start signal is received, the focus servo processing program 110
First, the data of the register 105 is reset to “0”. Thus, when the automatic focusing servo loop is not formed, the servo OF of each of the above-described embodiments is used.
The state is the same as when the F control signal is generated. At this time, no switching signal is sent from the MPU 103 to the switching circuit 64 via the interface 106.
Therefore, it is not in the just focus control state. That is, in the connection in the initial state, the switching circuit 62 is connected to the search waveform generation circuit 63 side. Note that a start signal from an external system control device input to the start signal input terminal 108 is sent out at a predetermined cycle in accordance with a timing to be focused when the power is on and in an operating state.

The focus servo processing program 110 includes:
When this program is executed by the MPU 103, the data in the register 105 is reset and the data collection program 111 is called. Data collection program 111
Activates the search waveform generation circuit 63. At this time, the state is the same as when the servo OFF control signal of each of the above embodiments is generated. After the execution of the data collection program 111, the peak detection program 112, the average value calculation program 11
3. Then, the level determination program 114 is sequentially called, and the data of the offset amount obtained by the end of the execution of the average value calculation program 113 is set in the register 105 in the automatic focus control loop. At the same time, a switching signal is sent from the MPU 103 to the switching circuit 62 via the interface 106. As a result, the switching circuit 62 is connected to the phase loop filter 62 side, and enters just focus control.

As a result, an analog voltage corresponding to the offset amount is applied to the signal level synthesizing circuit 59 by the D / A 102, and an automatic focusing servo loop is formed as in the embodiment of FIG. This corresponds to the state when the servo OFF control signal stops. The data collection program 111 is called by the focus servo processing program 110, and when this program is executed by the MPU 103, the MPU 103
Activates the search waveform generation circuit 63 via the interface 106, sequentially collects sampling data from the A / D 101 at a predetermined cycle, and stores the sampling data in the work area 11 of the memory 104.
Read in 5. When one search is completed, the activation of the search waveform generation circuit 63 is stopped. Then, the focus servo processing program 110 calls the peak detection program 112. MPU 10
3, when executed on the work area 11
The maximum peak value and the minimum peak value are detected from the data of No. 5 and stored in a predetermined area of the memory 104.

When this is completed, the focus servo processing program 110 next calls the average value calculation program 113. The average value calculation program 113 uses the MPU 10
When the processing is executed in step 3, the sum of the maximum peak value and the minimum peak value stored in a predetermined area of the memory 104 is obtained, and the result is divided by 2 to calculate an average value. At this time, instead of the averaging, a square mean taking a square route may be used.
The focus servo processing program 110 sets the obtained average value in the register 105 as an offset value. Then, the level determination program 114 is called. In addition,
The setting of the average value in the register 105 is performed when an automatic focusing servo loop is formed, as described later. The level determination program 114 determines that this program is an MPU
When executed by the MPU 103, the MPU 103 activates the search waveform generation circuit 63 via the interface 106, sequentially acquires sampling data from the A / D 101 at a predetermined cycle, and reads the sampling data into the work area 115 of the memory 104. Then, it is determined whether or not the read data value is within a predetermined range forming an automatic focusing servo loop. When the frequency falls within this range, the start of the search waveform generation circuit 63 is stopped, the average value is set in the register 105, and a switching signal is output to the switching circuit 64. As a result, an automatic focusing servo loop is formed so that automatic focusing can be performed. Since the processing contents of each processing program have been described in detail according to the processing order, the overall flowchart is omitted here.

The above-described processing corresponds to the embodiment of FIG. 3, but can also be realized by the program processing in the embodiment of FIG. For details, see A / A instead of peak detection program 112 and average value calculation program 113.
A maximum value detection processing program for receiving the RF detection signal RF via the D conversion circuit and detecting the maximum value of the level of the RF detection signal RF may be provided corresponding to the maximum value detection circuit 11. What is necessary is just to store the level of the detected maximum value. In the above case, the search waveform generating circuit 63 is not programmed for the sake of explanation. However, since this function is also a simple function of generating a ramp voltage, it can be realized by program processing. It is.

As described above, in the embodiment, the storage of the offset amount or the calculation of the average value based on the position error detection signal FE is performed when the automatic focusing servo is not performed. However, this is performed prior to the automatic focusing servo control. This may be performed every time, or the storage of the offset amount or the calculation of the average value may be performed periodically at a predetermined cycle. In the embodiment, the focal position of the laser beam is continuously moved forward by raising the focal position of the laser beam with respect to the optical disk from the lowest point. May be moved backward to descend from the uppermost point. Further, the signal level synthesizing circuits 59 and 61 for synthesizing the level of the position error detection signal with another signal level according to the embodiment are configured such that when the signal to be synthesized is negative, the addition synthesis is a subtraction synthesis. Since addition and synthesis are performed, either an addition or subtraction signal level synthesis circuit can be used.

[0034]

According to the first aspect of the present invention, the level of the position error detection signal FE is stored in correspondence with the maximum peak position of the RF detection signal RF, and the stored level is offset in the automatic focusing servo state. In the second invention, the maximum peak value and the minimum peak value of the level of the position error detection signal FE are detected, and the average value is calculated. , Using this as an offset amount, the position error detection signal FE
Combined to the level. In these two inventions, since the storage of the offset amount or the calculation of the average value based on the position error detection signal FE is performed when the automatic focusing servo state is not performed, there is no influence of disturbance noise.
Also, no disturbance oscillator is required. As a result, focusing can be performed with a simpler circuit without injection of disturbance, and S / N
The ratio can be improved, and readjustment is not required when external pickup parts are replaced.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment focusing on a focusing servo mechanism of an optical disc reproducing apparatus to which the present invention is applied.

FIG. 2 is a detection waveform diagram at the time of the focusing operation.

FIG. 3 is a block diagram of another embodiment of the present invention.

FIG. 4 is a block diagram of still another embodiment of the present invention in which focusing servo control is performed by program processing.

FIG. 5 is an explanatory diagram of a conventional focusing servo mechanism.

FIG. 6 is an explanatory diagram of detection signals A and B of a four-divided photodetector and an offset amount.

[Explanation of symbols]

1, 10 focusing servo mechanism, 2 optical disk, 3 rotation mechanism, 4 optical system, 5 focusing servo circuit, 11 maximum value detection circuit, 11a maximum / minimum peak detection circuit, 12 level storage circuit, 12a ... Average value detection circuit, 41 ... Laser unit, 42 ... Half mirror, 51 ... Four-division photodetector (pickup),
52: focus position error generation circuit, 53: level detection circuit, 54: response waveform generation circuit, 55: amplitude detection circuit, 56: automatic focus adjustment controller, 57: focus servo controller, 58: offset amount adjustment circuit, 59: synthesis Circuit, 60 disturbance oscillator, 61 synthesis circuit, 62 phase compensation loop filter, 63 search waveform generation circuit, 64 switching circuit, 65 drive amplifier,
66: Focus position adjustment mechanism.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D117 AA02 DD03 DD10 DD12 DD16 FF01 FF03 FF09 FX01 FX08 5D118 AA13 AA14 AA15 AA18 AA20 BA01 BF02 BF16 CA07 CB01 CB05 CD02 CD11

Claims (11)

[Claims] A photodetector receives reflected light from an optical disc and generates a detection signal of a light reception amount corresponding to the light reception amount and a detection signal of a position error regarding a focus position error, and a level of the detection signal of the light reception amount. In response, the focus servo controller switches to an automatic focus loop, and controls in a direction in which the position error disappears in accordance with the position error detection signal to automatically focus the laser light from the laser light source on the optical disc. An optical disc reproducing apparatus having a focus servo mechanism, comprising: a signal generating circuit for generating a signal for moving a focal position of the laser beam forward or backward with respect to the optical disc; and a maximum for detecting a maximum value of the detection signal of the amount of received light. Value detection circuit and the position error at this time in accordance with a detection signal from the maximum value detection circuit. A level holding circuit for holding the level of the detection signal of the error, the focus servo controller drives the signal generation circuit to detect the maximum value by the maximum value detection circuit without switching to the automatic focus loop. Then, control for switching to the automatic focus control is performed. In the automatic focus control, the level of the position error detection signal held in the level holding circuit and the level of the current position error detection signal are combined. An optical disc reproducing apparatus characterized in that automatic focusing is performed by performing the focusing. 2. A signal level synthesizing circuit for synthesizing a signal level of the position error detection signal with a level of an output signal obtained from the level holding circuit, wherein the level holding circuit detects the position error. 2. The optical disk reproducing apparatus according to claim 1, wherein the storage circuit stores a signal level, and an output signal of the storage circuit is generated when the automatic focus loop is switched. 3. The maximum value detection circuit is a maximum peak value and a minimum peak value detection circuit for detecting a maximum peak value and a minimum peak value of the position error detection signal, and the level holding circuit is configured to detect the maximum peak value. And an average value holding circuit that receives the maximum peak value and the minimum peak value from the minimum peak value detection circuit, calculates and holds an average value of the peak values, and outputs an average signal of the average value holding circuit. 2. The optical disk reproducing apparatus according to claim 1, wherein the optical disk reproducing apparatus is generated in a state where the mode is switched to a focus loop. 4. At least the maximum value detection circuit, the level holding circuit, and the focus servo controller,
2. The optical disk reproducing apparatus according to claim 1, wherein the functions are realized by a processor and a processing program executed by the processor. 5. The optical disk reproducing apparatus according to claim 2, wherein at least the maximum value detection circuit, the storage circuit, and the focus servo controller realize their functions by a processor and a processing program executed by the processor. 6. The processor according to claim 3, wherein at least said maximum peak value and minimum peak value detection circuit, said average value holding circuit, and said focus servo controller are implemented by a processor and a processing program executed by said processor. An optical disk reproducing apparatus according to claim 1. 7. The optical disk reproducing apparatus according to claim 1, wherein the signal generating circuit generates a signal waveform for searching for the focal position by moving the focal position toward or away from the optical disk. 8. A laser unit having the laser light source and a focusing lens movable along the optical axis of the laser light of the laser light source; a drive circuit; and a lens driven by the drive circuit to move the lens. A focus position adjustment mechanism for moving the focus position by performing the operation, a loop filter, and a switching circuit for selecting any one of the output of the search waveform generation circuit and the output of the loop filter and sending the output to the drive circuit. 8. The optical disc reproducing apparatus according to claim 7, wherein the focus servo controller switches to the automatic focus loop by switching the switching circuit from an output of the search waveform generation circuit to an output of the loop filter. 9. A signal level synthesizing circuit for synthesizing a signal level of the position error detection signal with a level of an output signal obtained from the level holding circuit, wherein the level holding circuit detects the position error. 9. The optical disk reproducing apparatus according to claim 8, wherein the storage circuit stores a signal level, and an output signal of the storage circuit is generated when the automatic focus loop is switched. 10. The maximum value detecting circuit is a maximum peak value and a minimum peak value detecting circuit for detecting a maximum peak value and a minimum peak value of the position error detection signal, and the level holding circuit is configured to detect the maximum peak value. And an average value holding circuit that receives the maximum peak value and the minimum peak value from the minimum peak value detection circuit, calculates and holds an average value of the peak values, and outputs an average signal of the average value holding circuit. 9. The optical disk reproducing apparatus according to claim 8, wherein the optical disk reproducing apparatus is generated in a state where the mode is switched to a focus loop. 11. A photodetector receives reflected light from an optical disk, and generates a detection signal of a light reception amount corresponding to the light reception amount and a detection signal of a position error regarding a focal position error, and a level of the detection signal of the light reception amount. In response, the focus servo controller switches to an automatic focus loop, and controls in a direction in which the position error disappears in accordance with the position error detection signal to automatically focus the laser light from the laser light source on the optical disc. In an optical disc reproducing apparatus having a focus servo mechanism, a level holding circuit is provided, and the level of the position error detection signal when the light reception amount detection signal is at a maximum value without switching to the automatic focus loop is set as a position error offset. The level is held in the level holding circuit, and the held level is An optical disc reproducing apparatus characterized in that when the mode is switched to a dynamic focus loop, the offset is generated as the offset amount and the focus is automatically adjusted.