JPH07129968A - Method of controlling focus and controller - Google Patents

Abstract

PURPOSE:To provide a method of controlling the drawing of high speed and stable focus control and to provide a high performance focus controller with a short starting time. CONSTITUTION:In a device converging and irradiating a light beam on a rotating disk 7, the focus control is performed so that the light beam on the disk 7 becomes a prescribed converged state. Until the disk 7 arrives at prescribed rotation for drawing the focus control, a converging lens 5 is moved to an inner periphery, and is separated from the disk 7 beforehand. After arriving at the prescribed rotation, by starting the drawing operation of the focus control from the position, the high speed and stable drawing performance is secured, and the starting time of the device is shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for optically recording a signal on a recording medium by utilizing a light beam from a light source such as a laser and reproducing the recorded signal. More particularly, the present invention relates to a focus control pull-in system and a control device for controlling the convergent state of the optical beam irradiated onto the recording medium to a predetermined convergent state.

[0002]

2. Description of the Related Art A conventional focus control apparatus records a signal by converging and irradiating an optical beam generated from a light source such as a semiconductor laser onto a disk-shaped recording medium rotating at a predetermined number of revolutions. There is an optical recording / reproducing device for reproducing. On this recording medium, minute tracks having a width of 0.6 μm and a pitch of 1.5 μm are provided in a spiral shape or a concentric shape. In order to record a signal on this track or reproduce a signal recorded on the track, in these optical recording / reproducing devices, the optical beam irradiated on the recording medium is brought into a predetermined convergent state. The focus control is performed so that

FIG. 5 is a block diagram showing a simple structure of a recording / reproducing apparatus including such a conventional focus control apparatus. Hereinafter, a conventional focus control device will be described with reference to FIG.

As shown in the figure, this conventional recording / reproducing apparatus is an optical system for irradiating a disk 7 as a recording medium with a light beam 8, a light source 1 such as a semiconductor laser, a coupling lens 2 and a polarized beam. Splitter 3, polarizing plate 4,
And a converging lens 5 and a disk motor 6 for rotating the disk 7 at a predetermined rotation speed. The light beam 8 generated from the light source 1 is collimated by the coupling lens 2. The parallel light is then reflected by the polarization beam splitter 3, passes through the polarizing plate 4, is converged by the converging lens 5, and is irradiated onto the disk 7 rotated by the disk motor 6.

This recording / reproducing apparatus further has a condenser lens 9 and a split mirror 10 as an element for receiving the reflected light from the disk 7. The reflected light from the disk 7 passes through the converging lens 5, the polarizing plate 4, and the polarization beam splitter 3, and is split into two light beams 11 and 15 in two directions by the split mirror 10 via the condenser lens 9. The light beams 11 and 15 are input to the focus control device and the tracking control device, respectively.

The focus control device comprises a photodetector 12 having a two-division structure, preamplifiers 13A and 13B, and a differential amplifier 1.
4, phase compensation circuit 18, linear motor 19, switch 3
3, drive circuit 35, focus control element (focus actuator) 36, logic circuit 40, comparator 41
And a triangular wave generator 42. Photo detector 12
Has two light receiving parts A and B, and each light receiving part A and B
Output signals from the preamplifiers 13A and 13A, respectively.
After being amplified by B, it is input to the differential amplifier 14.
Here, the knife lens detection method can be realized by the condenser lens 9 and the split mirror 10, and the output signal of the differential amplifier 14 becomes a defocus signal.

The defocus signal is supplied to the phase compensation circuit 18
Thus, the phase of the focus control system is compensated, and is input to the drive circuit 35 via the switch 33 for closing the loop of the focus control system. When the focus control system is closed by the switch 33, the drive circuit 3
A power amplifier 5 amplifies the focus shift signal from the phase compensation circuit 18 and outputs it to the focus control element 36. With such a configuration, the focus control element 36 is driven so that the light beam on the disc is always in a predetermined converged state when the focus control system is closed. The output signal of the triangular wave generator 42 is also input to the switch 33. The defocus signal is also input to the logic circuit 40 via the comparator 41. The logic circuit 40 controls opening / closing of the switch 33.

The linear motor 19 moves the converging lens 5, the focus control element 36, the polarization beam splitter 3 and the like in the direction traversing the track on the disk 7, and normally moves the converging point of the light beam to a predetermined track. When you do.

On the other hand, the other light beam 15 split by the split mirror 10 is input to a photodetector 16 having a two-division structure of the tracking controller. 2 photo detectors 16
It has two light receiving parts C and D, and the difference output signal of the output signals from the respective light receiving parts C and D becomes a track shift signal for controlling the light beam on the disk 7 to scan the track correctly. . Since the tracking control is not directly related to the present invention, detailed description will be omitted.

In the recording / reproducing apparatus having the focus control device having such a configuration, focus control is performed as follows.

First, when the disk 7 is rotated by the disk motor 6 and a predetermined rotation is reached, the switch 33 is switched to the triangular wave generator 42 side, and the focus control element 36 is driven by the triangular wave by the signal from the triangular wave generator 42. As a result, the converging lens 5 is moved up and down in the direction perpendicular to the recording surface of the disk 7. Therefore, the convergence point of the light beam on the disk 7 goes up and down. At this time, the comparator 41 detects an S-shaped defocus signal (hereinafter referred to as an S-shaped signal) that appears when the convergence point of the light beam passes through the recording surface. By detecting the S-shaped signal, the logic circuit 40 can know whether or not the convergence point of the light beam exists near the recording surface. When the convergence point exists near the recording surface, the switch 33 switches the phase compensation circuit. Switch to 18 side. In this way, by closing the focus control loop, the light beam is focus-controlled (focus pull-in) to a predetermined optimum target position.

This focus pull-in operation is shown in FIG.
This will be described with reference to FIGS. 7 and 8. FIG. 6 is a waveform diagram of the S-shaped signal appearing on the convergent lens drive signal and the focus shift signal when the focus is pulled in. FIG. 7 shows the waveform on the focus shift signal when the convergent lens 5 is moved toward and away from the disk 7. FIG. 8 is a waveform diagram showing the relationship between the S-shaped signal and the pull-in level on the protective film and recording film of the disk 7, and FIG. 8 is a simple flowchart showing the basic focus pull-in procedure in this focus control device.

As shown in FIG. 8, when the recording / reproducing apparatus is powered on, the disk motor 6 is turned on and the disk 7 is rotated in step S21. When the disk 7 reaches a predetermined rotation speed, the light source 1 is turned on in step S22, and, for example, the semiconductor laser emits light. Then, in step S23, the linear motor 19 operates to move the converging lens 5 to the inner peripheral side of the disk 7. When the above initial operation is completed, the focus pull-in operation is started.

First, as shown in FIG. 6 (a), in accordance with the output signal from the triangular wave generator 42, the converging lens 5 is lowered in step S24 to be separated from the disk 7, and then in step S24.
At 25, the converging lens 5 is raised to approach the disk 7.
While the converging lens 5 is repeatedly approached and separated, it is detected in step S26 that the S-shaped signal has reached a predetermined pull-in level. After reaching the predetermined pull-in level, the switch 33 is switched to the phase compensation circuit 18 side by the logic circuit 40, the vertical movement of the converging lens 5 is stopped in step S27, and the focus control is turned on in step S28. , The pull-in operation ends, and focus control is started.

The detection level (pull-in level) of the comparator 41 for pulling the focus is defined by the amplitudes of the S-shaped signals output by the reflection of the recording film and the reflection of the protective film of the disk 7, and is shown in FIG. As described above, the linear interval is set to be larger than the peak of the S-shaped signal of the protective film and between the peak of the S-shaped signal of the recording film and zero.

[0016]

According to the above method, the conventional focus control apparatus realizes the pull-in operation of the focus control. However, in such a conventional method, when the difference in reflectance between the protective film and the recording film of the disk 7 is small or absent, it is difficult to set the detection level of the comparator 41, which causes variations in the disk 7 and Depending on the noise level, the S-shaped signal of the protective film may be erroneously detected as the S-shaped signal of the recording film, and the switch 33 may be closed. In such a case, since the protective film portion is not in the linear range (pull-in range) of the focus, the focus cannot be pulled in, and there is a great possibility that the activation of the focus control device will be hindered.

A method for solving such a problem is disclosed in JP-A-64-89027 and JP-A-57-57.
It is proposed in Japanese Patent No. 150147.

In the method proposed in Japanese Unexamined Patent Publication No. 64-89027, first, the converging lens is moved closest to the disc so that the converging point of the light beam goes over the recording film, and is separated from the position. The recording film is surely detected by the S-shaped signal that appears first. Further, the method proposed in Japanese Patent Laid-Open No. 57-150147 counts the number of appearances of the S-shaped signal so that when the converging lens approaches, the converging point of the light beam comes to the recording film. This is a method of detecting that the position has been reached and pulling the focus.

According to these methods, the focus can be certainly pulled in at the S-shaped signal portion of the recording film. However, in practice, it is necessary to appropriately adjust the signal level of the focus shift signal in order to prevent malfunction due to saturation of the focus shift signal and a decrease in the level that occur due to variations in the reflectance of the disc. If such an adjusting operation is attempted to be introduced at the time of starting the focus control device, normally, as shown in the waveform diagram of FIG. 9 and the flowchart of FIG. 10, the converging lens is repeatedly approached (step S39) and separated (step S35). And S43) to measure the amplitude of the S-shaped signal (steps S36, S40 and S44) and the learning adjustment of the pull-in level by the comparator associated therewith (steps S37, S38, S41 and S4).
2) is required.

The speed at which the converging lens approaches or separates from the recording medium for focus pull-in is about 3 mm / s, and the focus pull-in time is 500 m in consideration of the time for moving the convergent lens in the radial direction by a linear motor or the like.
s It takes about 1 second. Since the start-up time of the recording / reproducing apparatus is about 5 seconds, the focus pull-in time accounts for a large proportion of the start-up time. Further, as described above, if the S-shaped signal measuring operation and the input gain switching operation are introduced at the time of focus pull-in in order to secure the pull-in stability, the startup time becomes very long.

In addition, for discs (especially CD and LD)
Has a large amplitude of surface wobbling (amount of surface wobbling).
± 500 μm at the outer peripheral part of the motor (acceleration of 10 m at standard speed)
/ S ²) Are also available. Convergence lens with large amount of surface runout
The relative velocity when the disk approaches and leaves the disk,
Depending on the situation, the time width that can be retracted becomes narrower and the focus
It becomes difficult to pull in. That is, S-shaped signal is detected
When the focus control is activated by
The convergence point of the
I can't pull in the focus because of the wrong movement. Was
Even if it is retracted, it will be
The overshoot of the circus shift signal becomes large,
Becomes unstable. In addition, the acceleration of surface wobbling of the disk is large.
If there is no vibration, or if there is a vibration shock from the outside, pull it in.
The possibility of failure will increase and the focus control device will
It has become inoperable and the reliability of the device has deteriorated.
It was The present invention solves the above-mentioned problems of the prior art.
Focus control that is fast and stable
Proposal of a control method for pull-in of a high-performance, short start-up time
Aiming to provide a focus control device for
It

[0022]

A focus control apparatus according to the present invention comprises rotating means for rotating a recording medium, converging means for converging and irradiating a light beam onto the recording medium rotated by the rotating means, and the converging means. First moving means for moving the convergent point of the light beam converged by the means in a direction substantially perpendicular to the recording medium surface, and the convergent point of the light beam converged by the converging means on the recording medium surface. The second moving means for moving from the innermost circumference to the outermost circumference in the direction traversing the track, the convergent state detecting means for generating a signal corresponding to the convergent state of the light beam on the recording medium, and the convergent state detecting means. The focus control means is provided to drive the first moving means according to the output signal so as to control the convergent position of the light beam on the recording medium to be substantially constant, and the focus control means detects the convergent state. Of means A detection means for detecting the amplitude of the force signal, and a timing control means for controlling the rotation means, the first moving means, and the second moving means so that the operation starts at substantially the same time, Thereby, the above object is achieved.

The focus control means responds to the amplitude detected by the detection means after the timing control means starts the operations of the rotating means, the first moving means and the second moving means. Gain switching means for switching the gain of the convergent state detecting means, and level calculating means for setting a pull-in level for bringing the focus control into an operating state in the output signal of the convergent state detecting means switched by the gain switching means. May be further provided.

When the level calculation means cannot bring the focus control into the operating state at the pull-in level initially set, the detection means detects the converged state detected by the gain switching means. The pull-in level may be set again according to the amplitude of the output signal of the means.

When the operation of the second moving means is started, first, the second moving means may be moved to the inner circumference of the recording medium.

Further, in the focus control method of the present invention, a rotating means for rotating the recording medium, a converging means for converging and irradiating a light beam onto the recording medium rotated by the rotating means, and a converging means for converging the light beam. First moving means for moving the convergent point of the light beam in a direction substantially perpendicular to the recording medium surface, and a direction in which the convergent point of the light beam converged by the converging means traverses a track on the recording medium surface. Second moving means for moving from the innermost circumference to the outermost circumference, a convergent state detecting means for generating a signal corresponding to the convergent state of the light beam on the recording medium, and an output signal of the convergent state detecting means. A focus control method in a focus control device, comprising: a focus control unit that drives the first moving unit to control the convergent position of the light beam on the recording medium to be substantially constant. It includes the step of detecting the amplitude of the output signal of the converged state detecting means, and the step of operating the rotating means, the first moving means, and the second moving means substantially at the same time. The above object is achieved.

After operating the rotating means, the first moving means, and the second moving means substantially at the same time, a step of switching the gain of the converged state detecting means in accordance with the detected amplitude, The step of setting the pull-in level for bringing the focus control into the operating state may be further included in the output signal of the converged state detecting means switched.

When the focus control cannot be operated at the pull-in level initially set,
The pull-in level may be set again in accordance with the detected amplitude of the output signal of the convergence state detecting unit whose gain has been switched.

When starting the operation of the second moving means, first, the second moving means may be moved to the inner circumference of the recording medium.

[0030]

In the focus control apparatus and method of the present invention,
Before the focus control means performs the focus control, the timing control means causes the rotating means to rotate the recording medium, and the first moving means causes the convergence point of the light beam converged by the converging means to substantially coincide with the recording medium surface. The operation of moving in the direction perpendicular to the direction and the operation of the second moving means to move the convergence point of the light beam in the direction crossing the track on the surface of the recording medium are controlled to start at substantially the same time. Therefore, since the moving time of the first moving means and the moving time of the second moving means for learning the S-shaped amplitude can overlap the starting time of the rotating means, the moving of the first moving means as a system. The time and the moving time of the second moving means can be apparently set to zero.

The gain switching means switches the gain of the convergence state detecting means in accordance with the amplitude detected by the detecting means in accordance with the reflectance and the light quantity of the light beam, and the level calculating means
Since the pull-in level for bringing the focus control into the operating state is set in the output signal of the convergent state detecting means switched by the gain switching means, the output signal of the convergent state detecting means is actually detected after the gain is switched ( The pull-in level can be set without performing learning operation.

Even if the pull-in level cannot be detected, the pull-in level is set again according to the amplitude of the output signal of the convergence state detecting means which is detected by the detecting means and which is switched by the gain switching means. Then, the level learning operation is executed at the next retry, so that the optimum gain and level are set and stable pull-in performance can be achieved.

Further, if the second moving means moves the convergence point of the light beam to the inner peripheral side where the surface wobbling of the recording medium is small, more stable focus control can be performed.

[0034]

Embodiments of the present invention will now be described in detail with reference to the drawings. In the drawings, the same members as those in the conventional example are designated by the same reference numerals.

FIG. 1 is a block diagram for explaining the configuration of an embodiment of the present invention in which a microprocessor is adapted to perform a focus control pull-in operation.

As shown in the drawing, the recording / reproducing apparatus of the present invention is a light source 1 such as a semiconductor laser, a coupling lens 2, a polarized beam, which is an optical system for irradiating a disk 7 as a recording medium with a light beam 8. Splitter 3, polarizing plate 4,
And a converging lens 5 and a disk motor 6 for rotating the disk 7 at a predetermined rotation speed. The light beam 8 generated from the light source 1 is collimated by the coupling lens 2. The parallel light is then reflected by the polarization beam splitter 3, passes through the polarizing plate 4, is converged by the converging lens 5, and is irradiated onto the disk 7 rotated by the disk motor 6.

This recording / reproducing apparatus further has a condenser lens 9 and a split mirror 10 as an element for receiving the reflected light from the disk 7. The reflected light from the disk 7 passes through the converging lens 5, the polarizing plate 4, and the polarization beam splitter 3, and is split into two light beams 11 and 15 in two directions by the split mirror 10 via the condenser lens 9. The light beams 11 and 15 are input to the focus control device and the tracking control device, respectively.

The light beam 15 is input to the photodetector 16 having a two-part structure of the tracking control device. Photo detector 16
Has two light receiving parts C and D, and each light receiving part C and D
The difference output signal of the output signals from the two becomes the track shift signal for controlling the light beam on the disk 7 to scan the track correctly. Since the tracking control is not directly related to the present invention, detailed description will be omitted.

On the other hand, the focus control device includes a photodetector 12 having a two-division structure, preamplifiers 13A and 13B, a differential amplifier 14, a gain switching circuit 17, a linear motor 19, a microprocessor 20, an AD converter 30, and a DA converter. Three
1, 32, switch 33, linear motor control circuit 34,
It is composed of a drive circuit 35, a focus actuator 36, and a laser drive circuit 38. The other light beam 11 split by the split mirror 10 is the photodetector 1
Entered in 2. The photodetector 12 has two light receiving parts A and B, and the output signals from the respective light receiving parts A and B are input to the differential amplifier 14 after being amplified by the preamplifiers 13A and 13B, respectively. Here, the knife lens detection method can be realized by the condenser lens 9 and the split mirror 10, and the output signal of the differential amplifier 14 becomes a defocus signal.

The focus shift signal is supplied to the gain switching circuit 1
7, the amplitude is changed according to the light beam light quantity corresponding to the reflectance of the disk 7 and the like, and a predetermined amplitude (gain) is obtained.
Adjusted to. Then, it is converted into a digital value by the AD converter 30 and input to the microprocessor 20.

The microprocessor 20 internally constructs a digital control system, and includes a core 21, a port 22, a phase compensation circuit 23, an S-shaped detector 24, an UP / DOWN unit 25, a motor controller 26 and a laser controller 27. Composed. The focus shift signal converted into a digital value is input to the phase compensation circuit 23 which is a digital filter including an adder, a multiplier and a delay device.
The focus shift signal in which the phase delay of the focus control system is compensated by the phase compensation circuit 23 is converted into an analog value by the DA converter 31 as a focus control signal, and is driven through the switch 33 that turns the focus control system on and off. 35 is input. The drive circuit 35 appropriately amplifies and level-converts the focus control signal to drive the focus actuator 36. In this way, the focus actuator 36 is driven so that the light beam on the disk 7 is always in a predetermined converged state.

The focus shift signal after AD conversion is processed and branched in the microprocessor 20 to realize the focus pull-in operation. The part of the microprocessor 20 that implements the focus pull-in by software and hardware will be described below.

The S-shaped detecting section 24 detects that the amplitude value of the S-shaped signal and the focus shift signal have reached a predetermined level based on the sample value of the focus shift signal after AD conversion.

The core 21 calculates the switching value of the gain switching circuit 17 for optimizing the S-shaped amplitude detected by the S-shaped detecting section 24. Further, the level at which the actual focus is drawn is calculated from the amplitude after the gain switching, and the value is output to the S-shaped detecting unit 24. Furthermore, the S-shaped detector 2
According to the result of 4, the core 21 controls the UP / DOWN unit 25 to operate the port 22, and the gain switching circuit 17
Switch the gain value of to a predetermined gain, or
The switch 33 is switched to operate the focus control. In addition to the series of focus pull-in operations (the pull-in operation will be described in detail later), the core 21 performs a filter process after the focus control is turned on or a restart when the focus control is released. Each part in the microprocessor 20 is controlled to realize the operation.

The UP / DOWN section 25 outputs a predetermined value via the DA converter 32 to move the converging lens 5 closer to or away from the disk 7 by a predetermined amount. Port 22
In addition to switching the switch 33 and switching the gain switching circuit 17, the linear motor control circuit 34 is operated by its output signal to move the converging lens 5 in the radial direction of the disk 7.

The motor control unit 26 controls the motor control circuit 37 so as to perform a part of the pull-in operation of the focus control while the disk motor 6 is activated, and realizes an optimum operation procedure.

The laser control unit 27 emits a laser beam, which is the light source 1, with a predetermined power according to a command from the core 21.
A signal from the laser control unit 27 is input to the laser drive circuit 38 and drives the laser light source 1.

In the present invention, the start-up of the disk motor 6 and a part of the focus pull-in operation are simultaneously executed,
After that, in order to emit a laser beam and continue the focus pull-in operation, the state of each part is managed by the core 21 and its operation is controlled.

Further, in the present invention, the core 21 controls the linear motor control circuit 34, so that the pull-in operation of the focus control can be realized in the inner peripheral portion with less surface wobbling.
Compared to the outer peripheral portion of the disk 7, the inner peripheral portion has a smaller amount of surface wobbling and the relative speed between the converging lens 5 and the disk 7 during the retracting operation is smaller, so that stable focus retracting can be realized. Further, since the CD and MO discs are spirals from the inner circumference to the outer circumference (that is, the innermost circumference position is address 0), in the case of a system that starts up and reads the address 0 and the control track and index areas in the vicinity, It is possible to further shorten the start-up time of the focus control device.

In the focus control device having such a structure, the operation at the time of focus pulling that can be realized by the microprocessor 20 will be described with reference to FIGS. 2 and 3. FIG. 2 shows a flowchart of focus pull-in executed by the microprocessor 20, and FIG.
FIG. 3 shows a waveform diagram showing an S-shaped signal appearing on the convergent lens drive signal and the focus shift signal when the focus is pulled in, and the positional relationship between the disc 7 and the convergent lens 5 at that time.

As shown in FIG. 2, when the power of the recording / reproducing apparatus is turned on, the microprocessor 20 is activated in step S1.
The core 21 in the inside operates the motor control unit 26 to rotate the disk motor 6 and sends a rotation command DMO.
An N signal is sent to rotate the disk 7 at a predetermined rotation speed. Since the disk motor 6 requires a rising time of about 1 second to reach a predetermined rotation speed, the disk motor 6
Immediately after the rotation command, in step S2, a signal is sent from the port 22 to the linear motor control circuit 24 to move the converging lens 5 to the inner peripheral side where the surface runout of the disk 7 is small. Immediately after that, in step S3, a predetermined value is output from the UP / DOWN unit 25, and the drive circuit 35 and the focus actuator 3 are output.
6, the converging lens 5 is lowered from the initial position A to the farthest point B as shown in FIG. When the recording / reproducing apparatus is installed horizontally, the convergent lens 5 is normally in a position lowered by its own weight, and therefore, the S-shaped signal does not appear in the focus shift signal during this descent. Therefore, the amplitude of the S-curve signal cannot be measured during this descent, and after moving to the farthest point B, S
The signal amplitude is measured and the pull-in level is detected.

Here, the time required for each of the steps S1 to S3 is (starting time of the disk motor 6 (step S1))
> (Moving time of linear motor 19 (step S2))>
Since there is a relationship of (falling time of the converging lens 5 (step S3)) and each is several hundred milliseconds or more, the timing of the command from the microprocessor 20 is as shown in FIG. It is considered to be almost simultaneous.

The motor control unit 26 detects that the disk 7 has reached a predetermined rotation speed. At this time,
Normally, the movement of the linear motor 19 and the converging lens 5 has been completed, and after the laser light source 1 is made to emit light in step S4, the actual pull-in operation of focus control is started at the position of the innermost circumference. Since each of steps S1 to S3 is controlled separately, the laser light source 1 emits light (step S
4) may be before the movement of the linear motor 19 and the converging lens 5 (steps S2 and S3) is completed.

As shown in FIG. 3, since the converging lens 5 is already located at the farthest point B, the converging lens 5 is gradually moved closer to the disk 7 toward the closest point D in step S5. At the same time, in step S7, the S-shaped detecting unit 24 samples the focus shift signal, and when the convergence point of the optical beam approaches the recording surface as in the conventional case, the focus point C is shown in FIG. The amplitude of the S-shaped signal appearing as shown in is measured. The S-shaped detector 24 measures the amplitude of the S-shaped signal, and when it is detected in step S7 that the converging lens 5 reaches the uppermost point D, the core 21 responds to the measured amplitude value in step S8. The gain of the gain switching circuit 17 is switched by outputting a predetermined signal from the port 22. At this time, the S-shaped signal corresponding to the gain switched by the gain switching circuit 17 has an optimum amplitude for the S-shaped detection unit 24 in the microprocessor 20 to reliably detect the pull-in level.

After switching the amplitude level of the S-shaped signal, in step S9, the UP / DOWN section 25 causes the converging lens 5 to move.
Is gradually lowered from the closest point D, and in step S10,
The S-shaped detector 24 measures the S-shaped amplitude of the focus shift signal. During this measurement, when the S-shaped detector 24 detects that the focus shift signal reaches the pull-in level 1 in step S11, the core 21 stops the operation of the UP / DOWN unit 25 in step S12. Then, the descending operation of the converging lens 5 is stopped. At the same time, in step S13, the port 22 outputs a signal to switch the switch 33, thereby closing the focus control loop and operating the focus control of the light beam on the disk 7.

Normally, the pull-in level 1 which is the reference value can be detected only by moving the converging lens 5 up and down once in steps S1 to S13. However, when the amplitude of the S-shaped signal in step S6 is not measured with sufficient accuracy due to variations in the disk 7, the head, etc., FIG.
As shown in step S11, the pull-in level 1 may not be detected in step S11. Even in such a case, the S-shaped detection unit 24 constantly samples the focus shift signal. Therefore, if the pull-in level 1 cannot be detected and the farthest point F, which is the same position as the point B, is reached in step S14, It is possible to measure the amplitude of the S-shaped signal when the convergent lens 5 descends as shown in FIG. Therefore, step S
At 15, the core 21 executes a correction calculation with the pull-in level 1 as a reference to calculate the pull-in level 2 for the S-curve amplitude measured at that time, and sets the value in the S-curve detector 24.

Thereafter, in step S16, UP / DOWN
The N section 25 gradually raises the converging lens 5 from the farthest point F toward the closest point G again, and the S-shaped detector 24 measures the amplitude of the S-shaped signal output at this time. In step S17, the core 21 confirms whether the set gain value of the gain switching circuit 17 is appropriate, and then in step S1.
If it is not appropriate in step 8, the gain value of the gain switching circuit 17 is switched by the port 22, and the pull-in level 2 of the S-shaped detector 24 is corrected and updated accordingly.

Thereafter, the process returns to step S9, the convergent lens 5 is gradually lowered from the closest point G again, and the output of the focus shift signal sampled by the S-shaped detector 24 is again output as shown in FIG. When the set pull-in level 2 is reached (when the focus point H is reached), the core 21 moves to U
The P / DOWN unit 25 is made inoperative, and the descent of the converging lens 5 is stopped. At the same time, by outputting a signal from the port 22 and switching the switch 33, the loop for focus control is closed, and the operation of the phase compensation circuit 23, which is a digital filter, is started, whereby the light beam on the disk 7 Activate focus control.

The focusing lens 5 for learning the moving time of the linear motor 19 and the S-shaped amplitude, which has been time-consuming if the pull-in operation of the focus control of the focus control device is realized by the above-described procedure. Since the moving time of 1 can overlap the starting time of the disk motor 6, the moving time of the linear motor 19 and the moving time of the converging lens 5 can be apparently set to 0 as a system. Further, in a normal state, even if the pull-in level is the reference value, the gain of the control loop becomes almost appropriate only by switching the gain according to the reflectance and the light amount of the light beam and appropriately adjusting the S-shaped amplitude value. , The pull-in operation is sufficiently possible. Therefore, it is possible to simplify the learning process that has been conventionally performed. Even if the pull-in level cannot be detected, the level learning operation is executed at the next retry, so that the optimum gain and level are set and stable pull-in performance can be achieved.

Therefore, the pull-in time of the focus control can be greatly shortened, and the pull-in stability can be secured.

In the present embodiment, the case where the converging lens is moved to the inner peripheral side of the disk where the influence of the surface wobbling is small in the initial stage has been described. (When reading data)
Immediately after the disk motor 6 is commanded to rotate, an outer peripheral movement signal may be sent to the linear motor control circuit 24 so that the linear motor 19 moves the converging lens 5 to the outer periphery of the disk 7.

In the present invention, the case where the converging lens 5 is separated from the disc 7 is explained first. However, when the reflectance of the disc 7 to be reproduced is almost constant, the S-shaped signal by the protective film on the surface of the disc 7 is shown. If there is almost no, the converging lens 5 is first
May be configured to approach the disk 7.

[0063]

As is apparent from the above description, according to the focus control apparatus and the control method of the present invention, the moving time of the converging lens for learning the S-shaped amplitude and the moving time of the linear motor are determined by Since it can overlap the motor start-up time, the moving time of the converging lens and the moving time of the linear motor can be apparently set to 0 as a system. Therefore, the time until the focus control is started can be shortened.

Further, since the pull-in level can be set without actually detecting (learning operation) the defocus signal after switching the gain, the time required for pull-in can be shortened.

Even if the pull-in level cannot be detected, the level learning operation is executed at the next retry, so that the optimum gain and level are set and stable pull-in performance can be achieved.

Further, at the time of start-up, the linear motor moves the convergence point of the light beam to the inner peripheral side where the surface wobbling of the disk is small, so that more stable focus control can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a focus control device for explaining the configuration of an embodiment of the present invention in which a microprocessor is adapted to perform focus control pull-in.

FIG. 2 is a flowchart showing a processing flow of a pull-in operation of focus control according to the embodiment of the present invention.

3A and 3B are waveform diagrams of a lens drive signal and a focus shift signal for explaining a pull-in operation of focus control, and a diagram showing a convergent lens position at each stage.

FIG. 4 is a waveform diagram of a lens drive signal and a focus shift signal for explaining a pull-in operation of focus control.

FIG. 5 is a block diagram showing a configuration of a conventional focus control device.

FIG. 6 is a waveform diagram for explaining a pull-in operation of conventional focus control.

FIG. 7 is a waveform diagram for explaining a pull-in operation of conventional focus control.

FIG. 8 is a flowchart showing a processing flow of a conventional focus control pull-in operation.

FIG. 9 is a waveform diagram showing an operation when a learning operation is added to stabilize the pull-in operation of the conventional focus control.

10 is a flowchart showing a processing flow of the operation shown in FIG.

[Explanation of symbols]

 6 disk motor 7 disk 8 light beam 12 photodetector 14 differential amplifier 17 gain switching circuit 19 linear motor 20 microprocessor 21 core 22 port 23 phase compensation circuit 24 S-shaped detection section 25 UP / DOWN section 26 motor control 27 laser control Part 33 Switch 34 Linear motor control circuit 35 Drive circuit 36 Focus actuator 37 Motor control circuit 38 Laser drive circuit

Claims (8)

[Claims] 1. A rotating means for rotating a recording medium, a converging means for converging and irradiating a light beam onto the recording medium rotated by the rotating means, and a converging point of the light beam converged by the converging means. First moving means for moving in a direction substantially perpendicular to the medium surface, and a convergence point of the light beam converged by the converging means from an innermost circumference to an outermost circumference in a direction traversing a track on the recording medium surface. Second moving means for moving, convergent state detecting means for generating a signal corresponding to the convergent state of the light beam on the recording medium, and the first moving means for responding to the output signal of the convergent state detecting means. A focus control unit that is driven to control the convergent position of the light beam on the recording medium to be substantially constant, and the focus control unit detects the amplitude of the output signal of the convergent state detecting unit; , The times Means, first moving means, and the operation start of the second moving means and a timing control means for controlling so as to be substantially at the same time, the focus control device. 2. The focus control means sets the amplitude detected by the detection means after the timing control means starts the operations of the rotating means, the first moving means, and the second moving means. In accordance with the gain switching means for switching the gain of the convergence state detecting means, and the output signal of the convergence state detecting means switched by the gain switching means, the level calculation for setting the pull-in level for bringing the focus control into the operating state. The focus control apparatus according to claim 1, further comprising: 3. The convergence calculated by the detection means and switched by the gain switching means when the level calculation means cannot bring the focus control into an operating state at the pull-in level initially set. The focus control device according to claim 2, wherein the pull-in level is set again in accordance with the amplitude of the output signal of the state detection means. 4. The focus control device according to claim 1, wherein when the operation of the second moving means is started, the focus control device is first moved to the inner circumference of the recording medium. 5. A rotating means for rotating a recording medium, a converging means for converging and irradiating a light beam onto the recording medium rotated by the rotating means, and a converging point of the light beam converged by the converging means is recorded. First moving means for moving in a direction substantially perpendicular to the medium surface, and a convergence point of the light beam converged by the converging means from an innermost circumference to an outermost circumference in a direction traversing a track on the recording medium surface. Second moving means for moving, convergent state detecting means for generating a signal corresponding to the convergent state of the light beam on the recording medium, and the first moving means for responding to the output signal of the convergent state detecting means. What is claimed is: 1. A focus control method in a focus control device, comprising: a focus control unit that is driven to control a convergent position of a light beam on the recording medium to be substantially constant. A focus control method comprising: a step of detecting a width; and a step of operating the rotating means, the first moving means, and the second moving means substantially at the same time. 6. After operating the rotating means, the first moving means, and the second moving means substantially at the same time,
Switching the gain of the convergent state detecting means according to the detected amplitude; and setting a pull-in level for bringing the focus control into an operating state in the output signal of the convergent state detecting means whose gain has been switched. The focus control method according to claim 5, further comprising: 7. Depending on the detected amplitude of the output signal of the converged state detecting means, the gain of which has been switched when the focus control cannot be brought into the operating state at the pull-in level initially set. 7. The focus control method according to claim 6, wherein the pull-in level is set again. 8. When the operation of the second moving means is started, first, the second moving means is moved to the inner circumference of the recording medium.
The described focus control method.