JPH1153739A - Focusing servo device and optical recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely pull in a focusing servo by allowing a focus lens to detect the inclinations of positions more approaching a focusing point than a position where a focus error expresses the extremal value and closing a focusing servo loop when the inclinations are within a preliminarily set range or a focal position. SOLUTION: After an inclination detecting circuit 12 detects a peak position from a signal S11 in which a focus error signal FE is subjected to an A/D conversion, it outputs a signal in which inclinations are calculated with a prescribed time interval. When a dicision circuit 13 or a focal position detecting circuit 14 discriminate that inclinations of the signal FE from signal S12 are within the preliminarily set range or a focusing point, they outputs a start signal S13 or S14. As a result, an input register 16 applies the signal S11 to a drive signal generating circuit 18 via a servo filter 17 by receiving the start signal S15 to be outputted by an OR gate 15 to turn a focusing servo on. Thus, the focusing servo is surely pulled in with a simple circuit without being affected by a disk and light receiving elements or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a CD (Compact Dis
c) A focus servo device used for an optical disk device such as a player and a magnetic recording / reproducing device using the same.

[0002]

2. Description of the Related Art Optical disc players such as CDs
The player generates a so-called RF signal based on the reflected light of the laser light applied to the disk surface. This RF
The signal is a signal generated by converting the intensity of the reflected light into a voltage through a light receiving element such as a photodetector, the reflected light of the light applied to the disk surface. When the pit on the disk surface is irradiated with light, the RF signal
The reflected light is attenuated to a low level, and when a portion other than the pits is irradiated with light, most of the light is reflected, so that the level is high.

The RF signal is generated by an RF amplifier. The RF amplifier generates a focus error signal FE used for driving a focus actuator and a tracking error signal TE used for driving a tracking actuator. And these RF signals,
The focus error signal FE and the tracking error signal TE are supplied to a servo circuit, which controls the driving of the focus actuator and the tracking actuator.

An optical pickup for irradiating a laser beam onto a disk surface is provided with a focus lens for converging the laser beam to a desired position on the disk, and a servo circuit connects the focus lens and the disk to a predetermined position. A focus servo system circuit for turning on / off the focus servo to maintain the distance is provided.

As this type of focus servo device,
Generally, the one disclosed in Japanese Patent Publication No. 63-13261 is known. This focus servo device has the same polarity as the focus error signal FE as shown in FIG. 5 and is generated when the focus lens is located at a point farther from the disc than the in-focus position. The reference voltage Vref having a small absolute value is compared with the focus error signal FE, and the state is changed from one state to another state.
Alternatively, a comparator that generates an output signal that changes from another state to one state, and a comparator at a position where the focus lens is closer to the in-focus position than when the focus error signal FE indicates one extreme value. And a switch for detecting a point at which the output signal changes and outputting a control signal, and a switch for closing the focus servo loop in accordance with the control signal.

According to the focus servo device having such a configuration, the time when the focus servo loop is started, that is, when the focus servo is turned on, is determined by the focus error signal FE itself having a so-called S-shaped characteristic and the comparator. Nearby points that are slightly further away from the disk are detected and determined. For this reason, it is possible to suppress the influence of the disk, the light receiving element, and the like, and perform the pull-in to the focus servo.

[0007]

However, in the above-described focus servo device, the focus error signal F
Since the focus servo is turned on by detecting a point near the in-focus position based on the comparison result between E and the reference voltage Vref, the focus servo always has an S-shaped characteristic due to the influence of the fluctuation of the focus error signal FE and the like. It may not be possible to detect a point near the focal point that follows the focus error signal FE, and there may be variations in the detection of a point near the focal point. As a result, it is difficult to say that the focus servo can be accurately drawn. Also,
Although a circuit for compensating the variation can be provided, this has disadvantages such as a complicated circuit and an increase in circuit scale.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reliably focus without being affected by a disk, a light receiving element, and the like without inviting a complicated circuit and an increase in circuit scale. It is an object of the present invention to provide a focus servo device and an optical recording / reproducing device that can perform servo pull-in.

[0009]

In order to achieve the above object, the present invention relates to a focus servo device for converging light emitted from a light source to a recording medium surface via a focus lens. Becomes zero when the focus lens is at the in-focus position, and when the focus lens is positioned before and after the in-focus position, signals having different polarities are generated, and the signals having the different polarities pass through one extreme value. Means for generating a focus error signal having a characteristic of approaching zero as the distance from the in-focus position increases, and wherein the focus lens is closer to the in-focus position than the position when the focus error signal indicates the one extreme value. An inclination detecting means for detecting an inclination at at least one position, and Out the slope and a means for closing the focus servo loop when it reaches or focused position when falls within the range set in advance.

In the present invention, the one extreme value at which the inclination detecting means starts the inclination detection is a peak value of a focus error signal.

Further, according to the present invention, a focus error signal obtained in accordance with a reflected light level of light applied to a recording medium surface via a focus lens is input to a servo filter in a servo-on state, and the focus filter is connected to the focus lens. A focus servo device for obtaining a drive output for maintaining a predetermined distance from a recording medium surface, comprising: an analog / digital converter for converting an analog focus error signal into a digital focus error signal; A tilt detecting circuit for detecting, at a predetermined time interval, a tilt at a position where the focus lens is closer to the in-focus position than a position at which the focus error signal indicates one extreme value, and the tilt detecting circuit detects the tilt. When the slope falls within the preset range, the first activation signal A focus determination circuit for determining whether a focus position has been reached based on a detection result of the tilt detection circuit, and outputting a second start signal when the focus position has been reached; and An input register that receives the first or second start-up signal, inputs a digital focus error signal from the analog / digital converter, and inputs the digital focus error signal to the servo filter at a predetermined timing.

The present invention is also an optical recording / reproducing apparatus for performing at least a reproducing operation of data recording and reproducing by converging light emitted from a light source to a recording medium surface via a focus lens. When the focus lens is at the in-focus position, it becomes zero. When the focus lens is located before and after the in-focus position, signals having different polarities are generated, and the signals having different polarities represent one extreme value. Means for generating a focus error signal having a characteristic of approaching zero as the distance from the in-focus position increases, and wherein the focus lens is located closer to the in-focus position than the position when the focus error signal indicates the one extreme value. An inclination detecting means for detecting an inclination at at least one approached position, and It can, detected inclination and a focusing servo device and a means for closing the focus servo loop when it reaches or focused position when falls within the range set in advance.

The present invention also relates to an optical recording / reproducing apparatus for performing at least a reproducing operation of recording and reproducing data by converging light emitted from a light source onto a recording medium surface via a focus lens, It becomes zero when the focus lens is at the in-focus position according to the reflected light level of the light applied to the recording medium surface via the lens, and has a polarity when the focus lens is located before and after the in-focus position. An RF amplifier for generating an analog focus error signal having a characteristic in which different signals are generated and each of the signals having different polarities approach zero as the distance from the focus position increases through one extreme value; An analog / digital converter for converting a signal into a digital focus error signal; A tilt detection circuit that receives a focal focus error signal, and detects at a predetermined time interval a tilt at a position where the focus lens is closer to the in-focus position than a position when the focus error signal indicates one extreme value; A determination circuit for outputting a first activation signal when the inclination detected by the inclination detecting means falls within a preset range; and determining whether the in-focus position has been reached based on the detection result by the inclination detecting means. A focus position detection circuit for determining and outputting a second start signal when the focus position is reached, and receiving a digital focus error signal from the analog / digital converter upon receiving the first or second start signal And an input register for inputting the signal to the servo filter at a predetermined timing and holding the focus lens and the recording medium surface at a predetermined distance. And a servo circuit for.

According to the present invention, according to the reflected light level of the light emitted from the light source and applied to the recording medium surface via the focus lens, the value becomes zero when the focus lens is at the in-focus position. Focus signals having different polarities are generated when they are positioned before and after the in-focus position, and the respective signals having different polarities approach zero as the distance from the in-focus position increases through one extreme value. An error signal is generated and input to the inclination detecting means. In the inclination detecting means, the focus lens outputs a focus error signal of one extreme value,
For example, an inclination at at least one position closer to the in-focus position than the position at which the peak value is shown is detected. Then, when the detected inclination falls within a preset range, the focus servo loop is closed. Thereby, the focus lens and the recording medium surface are adjusted so as to maintain a predetermined distance (focus distance). If there is no inclination within the set range before the focus point is reached, the focus servo loop is forcibly closed when the focus point is reached.

[0015]

FIG. 1 is a system block diagram showing a configuration example of an optical disc player to which a tracking servo circuit according to the present invention is applied.

In FIG. 1, the information recorded on the disk 1 is
It is read by the optical pickup 2. The optical pickup 2 includes a focus actuator that drives a focus lens (objective lens) in the optical axis direction so as to converge a light beam irradiated on the disk 1 on the disk surface, and a light beam spot converged on the disk surface. And a photodetector that receives a reflected light beam from the disk surface based on the three light beams irradiated on the disk 1 and the like, and is provided so as to be movable in the radial direction of the disk 1. I have.

The photodetector built in the optical pickup is shown in FIG.
As shown in the figure, of the three light beams, four integrated photodiodes A to D for receiving the reflected light beam based on the main beam, and receiving the reflected light beams based on the two light beams on both sides thereof And a pair of photodiodes E and F. Each output of the four photodiodes A to D and each output of the pair of photodiodes E and F are supplied to the RF amplifier 3.

The RF amplifier 3 outputs focus error signals FE and R used for driving a focus actuator based on the outputs of the four photodiodes A to D.
An F signal is generated, and a tracking error signal TE used for driving the tracking actuator is generated based on each output of the pair of photodiodes E and F. Then, these RF signal, focus error signal FE and tracking error signal TE are
Output to Note that the RF signal is also output to a reproduction processing system (not shown) and used for demodulation of digital data.

For example, as shown in FIG. 5, the focus error signal FE becomes zero when the focus lens is at the focal point, and has different polarities when the focus lens is located before and after the focal point of the focus lens. Each signal has a characteristic of approaching zero as it goes away from the focal point through one extreme value.

The digital servo circuit 4 generates a signal FOK indicating that the RF signal generated by the RF amplifier 3 has exceeded a certain level based on the reflected light, and supplies the signal FOK to the tracking servo system and the focus servo system. Signal F
OK is set to a high level when the RF signal exceeds a certain level, and is set to a low level when reflected light cannot be obtained for some reason and the RF signal becomes below a certain level. In the focus servo system, the signal FOK is used to confirm that reflected light from the disk surface is obtained to a certain extent when performing a focus search operation. Further, in the tracking servo system, it is used for correction control of imbalance such as the sensitivity of the photodiodes E and F. Specifically, when the signal FOK is at the low level, the correction operation is stopped.

The focus servo system converts a focus error signal FE, which is an analog signal, into a digital signal,
On the basis of this digital signal, a portion from a position indicating one extreme value of the focus error signal (a position where the inclination is zero) to at least a focus position (a position where the inclination is the maximum in the negative direction) is divided into a plurality on the time axis. For each division unit, the slope of the focus error signal is calculated, and when the calculated slope is within a preset range, it is recognized as a near-focus point area, and the focus servo loop is started, that is, the focus servo is turned on. To drive the focus actuator to perform focus adjustment.

The system controller 5 is composed of a microprocessor and controls the entire system such as the control of the digital servo circuit 4.

FIG. 3 is a block diagram showing an embodiment of the focus servo circuit of the optical disk player according to the present invention, and constitutes a part of the digital servo circuit 4. That is, the focus servo circuit 10 controls the A / D
It comprises a converter 11, a tilt detection circuit 12, a determination circuit 13, a focus position detection circuit 14, an OR gate 15, an input register 16, a focus servo filter 17, and a drive signal generation circuit 18.

The A / D converter 11 converts the focus error signal FE, which is an analog signal from the RF amplifier 3, into a digital signal, and converts it into a signal S11 as a signal S11.
2 and input register 16.

The inclination detecting circuit 12 is provided with the A / D converter 1
1, one extreme value of the focus error signal, specifically, a peak position is detected on the time axis, and as shown in FIG. 4, the focus error signal is detected at a predetermined unit time interval from the peak position. (Minus inclination), and outputs the result to the determination circuit 13 and the in-focus position detection circuit 14 as a signal S12. In addition,
This inclination calculation is performed at least up to the in-focus position where the inclination is maximum.

The determination circuit 13 receives the signal S12 from the inclination detection circuit 12, and determines whether or not the inclination of the focus error signal obtained for each division unit is within a preset inclination range. If the obtained inclination is within the set range, it is recognized as a near-focus point area, and the focus servo loop is started, that is, a pulse-like first start signal S13 for turning on the focus servo.
Is output.

The in-focus position detecting circuit 14 receives the signal S12 from the tilt detecting circuit 12, determines whether or not the in-focus position has been reached. 2 is output.

The OR gate 15 takes the logical sum of the first activation signal S13 from the determination circuit 13 and the second activation signal S14 from the focus detection circuit 14 and the second activation signal S14 to obtain an OR signal 16 as an activation signal S15. Output to

The input register 16 is held in a clear state when the activation signal S15, that is, the first activation signal S13 by the determination circuit 13 and the second activation signal S14 by the focus position detection circuit 14, are inactive. In response to the start signal S15, that is, the first start signal S13 or the second start signal S14, the clear terminal is turned off to be in the operating state, and the 8-bit digital signal S11 output from the A / D converter 11 (focus) An error signal is fetched, and the fetched digital signal is output to the servo filter 17 in synchronization with a clock.

Next, the operation of the focus servo system in the above configuration will be described. Laser light emitted from the optical pickup 2 via the focus lens is applied to the disk 1, and the reflected return light is received by the photodetector of the optical pickup 2. The outputs of the four integrated photodiodes A to D and the outputs of the pair of photodiodes E and F are supplied to the RF amplifier 3.

In the RF amplifier 3, the focus error signal FE used for driving the focus actuator is determined based on the outputs of the four photodiodes A to D.
And an RF signal are generated, and a tracking error signal TE used for driving the tracking actuator is generated based on each output of the pair of photodiodes E and F. Then, the RF signal, the focus error signal FE, and the tracking error signal TE are output to the digital servo circuit 4. The RF signal is also output to a reproduction processing system (not shown) and used for demodulating digital data.

In the digital servo circuit 4, the input register 16 is in a clear state. The focus error signal FE, which is an analog signal, is output from the A / D converter 1
1, where it is converted into a digital signal S11 and output to the inclination detection circuit 12 and the input register 16.

The inclination detecting circuit 12 detects the peak position of the focus error signal on the time axis based on the digital signal S11 from the A / D converter 11, and from the peak position, the inclination of the focus error signal at a predetermined unit time interval. (Negative slope) is obtained, and the result is signal S1.
2 is output to the determination circuit 13 and the in-focus position detection circuit 14.

In the determination circuit 13, the inclination detection circuit 1
In response to the signal S12 of step S2, it is determined whether or not the inclination of the focus error signal obtained for each division unit is within a preset inclination range. As a result of this determination, if the obtained inclination is within the set range, it is recognized as a near-focus point area, and a pulse-like first start signal S13 for starting the focus servo loop.
Is generated and output to the OR gate 15.

The focus position detection circuit 14 receives the signal S12 from the inclination detection circuit 12, and determines whether or not the focus position has been reached. As a result, if it is determined that the in-focus position has been reached, a pulsed second activation signal S14 is output to the OR gate 15.

Then, from the OR gate 15, the judgment circuit 1
3 or the focus detection circuit 1
4 is output to the input register 16 as a start signal S15.

The input register 16 receives the start signal S15 for the first time, that is, normally receives the first start signal S1.
However, if the first activation signal S13 is not output even if the detected inclination does not fall within the set range and the focus position is reached, the second activation signal S14 is changed to the activation signal S15.
Is first input, the clear terminal is turned off and the operating state is established, and the 8-bit digital signal S11 (focus error signal) output from the A / D converter 11 is captured. Then, the fetched digital signal is output to the servo filter 17 in synchronization with the clock, and a drive output is obtained by the drive signal generation circuit 18 based on the output signal of the servo filter 17. As a result, drive control of the focus actuator is performed, and the position of the focus lens is adjusted to the in-focus position.

As described above, according to this embodiment, the peak position which is one extreme value of the focus error signal is detected on the time axis based on the digital signal S11 from the A / D converter 11, and this peak is detected. In response to a signal S12 from the inclination detection circuit 12 for obtaining the inclination of the focus error signal at predetermined unit time intervals from the position, the inclination of the focus error signal obtained for each division unit is set to a predetermined inclination. It is determined whether or not it is within the range, and if the obtained inclination is within the set range, it is recognized as a near-focus point area and a first start signal S13 for starting the focus servo loop is generated. A decision circuit 13 for outputting a signal S1 from the inclination detection circuit 12
2 to determine whether or not the camera has reached the in-focus position, and if it is determined that the in-focus position has been reached, the in-focus position detection circuit 14 which outputs a second activation signal S14 in the form of a pulse; An OR gate 15 which takes a logical sum of the first start signal S13 by the circuit 13 and the second start signal S14 by the focus detection circuit 14 and outputs the result to the input register 16 as a start signal S15; When the signal S15 is inactive, the signal is held in the clear state. Upon receiving the start signal S15, the clear terminal is turned off to be in the operating state, and the 8-bit digital signal S11 output from the A / D converter 11 (focus error signal) ), And the input register 16 for outputting the fetched digital signal to the servo filter 17 in synchronization with the clock is provided. Start loop, i.e. when to turn on the focus servo is near point away from the disk slightly is determined is detected than the focused position. Even if no point near the in-focus position is detected, control is performed so that the focus servo is always turned on when the in-focus position is reached. Since the focus servo is turned on by detecting the inclination of the focus error signal having the S-characteristics instead of comparing with the reference voltage and detecting the point near the focus position, the focus error signal FE
Irrespective of the fluctuation of the focus error signal FE, the detection of the point near the in-focus position following the focus error signal FE can be performed without variation. As a result, there is an advantage that the focusing servo can be accurately performed without being affected by the disk, the light receiving element, and the like, and the circuit can be simplified and the circuit scale can be reduced.

[0039]

As described above, according to the present invention,
There is an advantage that the focus servo can be reliably pulled in without being affected by the disk, the light receiving element, and the like. Further, there is an advantage that the circuit can be simplified and the circuit scale can be reduced.

[Brief description of the drawings]

FIG. 1 is a system block diagram showing a configuration example of an optical disc player to which a focus servo device according to the present invention is applied.

FIG. 2 is a layout diagram of photodiodes in the optical pickup of FIG. 1;

FIG. 3 is a block diagram showing one embodiment of a focus servo circuit of the optical disc player according to the present invention.

FIG. 4 is a diagram for explaining a function of a tilt detection circuit according to the present invention.

FIG. 5 is a waveform chart for explaining a focus error signal.

[Explanation of symbols]

1 disk, 2 optical pickup, 3 RF amplifier,
4: Digital servo circuit, 5: System controller,
DESCRIPTION OF SYMBOLS 10 ... Focus servo circuit, 11 ... A / D converter, 12 ... Inclination detection circuit, 13 ... Judgment circuit, 14 ... Focusing point position detection circuit, 15 ... OR gate, 16 ... Input register, 17 ... Servo filter, 18 ... Drive Signal generation circuit.

Claims (5)

[Claims] 1. A focus servo device for converging light emitted from a light source to a recording medium surface via a focus lens, wherein the focus servo device becomes zero when the focus lens is at a focal point, and A focus error having such characteristics that signals having different polarities are generated when the signal is located before and after the in-focus position, and that the signals having different polarities approach zero as the distance from the in-focus position increases through one extreme value. Means for generating a signal; inclination detection means for detecting an inclination at at least one position where the focus lens is closer to the in-focus position than a position when the focus error signal indicates the one extreme value; Based on the detection result by the tilt detection means, the detected tilt falls within the preset range. Means for closing the focus servo loop when the camera reaches a focus position. 2. The focus servo device according to claim 1, wherein the one extreme value at which the inclination detection means starts inclination detection is a peak value of a focus error signal. 3. A focus error signal obtained in accordance with a reflected light level of light applied to a recording medium surface via a focus lens is input to a servo filter in a servo-on state. A servo output device for obtaining a drive output for holding a digital focus error signal at a predetermined distance, comprising: an analog / digital converter for converting an analog focus error signal into a digital focus error signal; A tilt detection circuit for detecting, at predetermined time intervals, a tilt at a position closer to the focal point than the position at which the focus error signal indicates one extreme value, and the tilt detected by the tilt detection circuit is preset. Time for outputting the first activation signal when the value falls within the specified range. A focus position detection circuit that determines whether or not the focus position has been reached based on the detection result of the inclination detection circuit, and outputs a second activation signal when the focus position has been reached; In response to the first or second start signal, the analog /
A focus servo device comprising: an input register that inputs a digital focus error signal from a digital converter and inputs the digital focus error signal to the servo filter at a predetermined timing. 4. An optical recording and reproducing apparatus for performing at least a reproducing operation of data recording and reproducing by converging light emitted from a light source onto a recording medium surface via a focus lens, wherein the focus lens is When the focus lens is located at the focal position, it becomes zero. When the focus lens is located before and after the in-focus position, signals having different polarities are generated, and the signals having the different polarities pass through one extreme value. Means for generating a focus error signal having the property of approaching zero as the distance from the position increases;
Inclination detecting means for detecting an inclination at at least one position where the focus lens is closer to the in-focus position than a position at which the focus error signal indicates the one extreme value, and a detection result of the inclination detecting means. Based on
A focus servo device having means for closing the focus servo loop when the detected inclination falls within a preset range or reaches a focal point. 5. An optical recording / reproducing apparatus for performing at least a reproducing operation of data recording and reproducing by converging light emitted from a light source to a recording medium surface via a focus lens, wherein According to the reflected light level of the light applied to the recording medium surface, the focus lens becomes zero when the focus lens is at the in-focus position, and signals having different polarities are generated when the focus lens is located before and after the in-focus position. An RF amplifier for generating an analog focus error signal having a characteristic that each signal having a different polarity approaches zero as the distance from the in-focus position passes through one extreme value, and digitally focuses the analog focus error signal. An analog / digital converter for converting to an error signal and the digital focus An inclination detection circuit for receiving an error signal and detecting, at a predetermined time interval, an inclination at a position where the focus lens is closer to the in-focus position than a position at which the focus error signal indicates one extreme value; A determination circuit for outputting a first activation signal when the inclination detected by the detection circuit falls within a preset range; and determining whether or not the focus position has been reached based on the detection result of the inclination detection circuit. A focus position detecting circuit for outputting a second start signal when the focus position is reached, and a digital focus error signal by the analog / digital converter upon receiving the first or second start signal. A servo circuit having an input register for inputting the signal to the servo filter at a predetermined timing and holding the focus lens and the recording medium surface at a predetermined distance. Optical recording reproducing apparatus equipped with and.