JPH08287478A - Focus controller - Google Patents

Abstract

PURPOSE: To provide a focus controller with stable focus drawing operation and an excellent control characteristic and realizing a stable focus control loop in the focus controller for the device recording or reproducing information on at least two kinds or above of optical recording media. CONSTITUTION: This controller is provided with noise removal means 17-1, 17-2 provided with at least two kinds or above of noise removal characteristics and switching the noise removal characteristics by a characteristic switch signal. By generating the characteristic switch signal according to an output of a recording medium identification means 16 identifying the kinds of two kinds or above of recording media, a noise component superimposed on a focus error signal is eliminated without attenuating the focus error signal, and the stable focus drawing operation is performed by precisely measuring the focus error signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for recording or reproducing at least two types of optical recording media (hereinafter referred to as disks) represented by read-only and recordable / reproducible optical disks. The present invention relates to a focus control device.

[0002]

2. Description of the Related Art In recent years, optical discs have a high recording density, a long life of the medium because they can be recorded and reproduced in a non-contact manner, and random access is much faster than a medium such as a tape. There are many proposals such as a CD and a VLP as an example, and an image file, a data file, a document file as a recording and reproducing device.

FIG. 5 shows a block diagram of a conventional focus control device in the above device. The operation of the conventional focus control device will be described with reference to FIG. In FIG. 5, reference numeral 50 denotes an optical head for irradiating a disk with a light beam, which drives the objective lens by a drive signal to move the focus position of the light beam and outputs the deviation of the focus position as a focus error signal. . Further, 51 is a gain varying means for changing the gain of the focus error signal output from the optical head, 52 is a compensating means for stabilizing the focus control loop, and 53 is an up / down means for generating a signal for moving the objective lens of the optical head up and down. Signal generating means, 54
Is a switching means for switching the outputs of the compensating means 52 and the up / down signal generating means 53, 55 is a driving means for amplifying the output of the switching means 54 to drive the optical head, and 57 is a noise removing means included in the output of the gain varying means 51. Noise removing means, 58 is a focus error signal amplitude measuring means for measuring the output amplitude of the noise removing means 57, and 59 is a pull-in timing generating means for outputting a switching signal to the switching means.

First, the pull-in timing generating means 59 issues a command to the switching means 54 to select the output of the up / down signal generating means 53. The up / down signal generating means 53 outputs a command signal for moving the objective lens of the optical head 50 up and down, for example, a triangular wave signal or a rectangular wave signal, and the command signal is input to the driving means 55 through the switching means 54. Then, the electric power is amplified by the driving means and then input to the optical head. The objective lens of the optical head 50 moves up and down according to the output signal of the up / down signal generating means 53, and outputs the deviation of the focal position of the light beam as a focus error signal. The focus error signal is shown in Figure 3.
This is the signal shown in (a), and noise is superimposed due to the influence of the address portion, data pits, and the like on the disc. The focus error signal output from the optical head 50 passes through the gain varying means 51, the noise component is attenuated by the noise removing means 57, and is input to the pull-in timing generating means 59 and the focus error signal amplitude measuring means 58. The focus error signal amplitude measuring means 58 measures the signal amplitude of the focus error signal, inputs the measurement result to the gain changing means 51, and outputs the focus error signal amplitude measured so that the amplitude of the focus error signal becomes an appropriate level. Accordingly, the gain of the gain changing means 51 is changed.
The output of the focus error signal amplitude measuring means 58 is input to the pull-in timing generating means 59 to set the focus pull-in level for generating the timing for closing the focus control loop. Similarly, the up / down signal generating means 53 outputs the up / down command signal again, and the optical head 50 is passed through the switching means 54 and the driving means 55.
In addition, the focal position of the optical head 50 moves. The focus error signal is input to the pull-in timing generating means 59 through the gain varying means 51 and the noise removing means 57, compared with the focus pull-in level set in advance, and pulled in from the pull-in timing generating means 59 when reaching a predetermined level. The command is output to the switching means 54, the output of the up / down signal generating means 53 is cut off, the output of the compensating means 52 is selected, and the focus control loop is closed. The focus error signal, which is the deviation of the focus position of the light beam, passes through the gain varying means 51, the compensating means 52, the switching means 54, and the driving means 55 in this order, and the optical head 5
The objective lens is moved so that the deviation of the focal position is eliminated by inputting 0. With the above operation, the focus control loop is closed and the focus of the light beam is focused on the disc.

[0005]

However, in the above-mentioned conventional focus control device, the characteristic of the noise removing means for removing the noise component from the focus error signal on which the noise is superimposed due to the influence of the address part or the data pit on the disk. Is the same regardless of the type of disc, so when using multiple types of discs, it is sufficient when the frequency of the noise component that is superimposed on the focus error signal differs depending on the disc type and the amount of surface wobbling of the disc differs. In some cases, the noise component cannot be removed or the basic component of the focus error signal is attenuated, so that the amplitude of the focus error signal cannot be accurately measured. For example, when a recordable and reproducible optical disc and a reproduction-only optical disc such as a CD are used as the disc, generally, the recordable and reproducible optical disc corresponds to the recording operation, so that the surface wobbling amount can be suppressed smaller than that of the reproduction-only optical disc. ing. However, address information is carved on the disc, and a noise component of a relatively low component is superimposed on the focus error signal. On the other hand, in a read-only optical disc such as a CD, the noise component superimposed on the focus error signal is mainly due to pits on the disc, and its frequency component is relatively high. However, the standard value of the amount of surface wobbling is larger than that of an optical disk capable of recording and reproducing. in this case,
If the cutoff frequency of the noise removing means is set low so that the noise component contained in the recordable / reproducible optical disk can be sufficiently removed, the surface deflection amount is large in the read-only optical disk, so that the speed at which the focal position of the light beam fluctuates becomes large. As shown in FIG. 3, the frequency of the basic component of the focus error signal output in an S-shape becomes high, and the noise removing means having a low cutoff frequency attenuates the basic component of the focus error signal itself, so that the correct component is accurate. It is not possible to measure the focus error signal amplitude. On the contrary, if the cutoff frequency of the noise elimination means is set high so that the basic component of the focus error signal is not attenuated in the read-only disc, the noise in the focus error signal due to the address part of the recording / playback optical disc cannot be attenuated sufficiently. , The focus error signal cannot be measured accurately.

Therefore, in the conventional focus control device,
When using multiple types of discs, the focus error signal amplitude cannot be accurately measured, and errors occur in the pull-in level and gain variable means settings that are set by the focus error signal amplitude, resulting in stable focus control. However, there are problems that the pull-in operation cannot be performed, the gain of the focus control loop cannot be made appropriate, the control performance deteriorates, and the control system becomes unstable.

The present invention solves the above-mentioned conventional problems, and stabilizes an apparatus for recording or reproducing at least two types of optical recording media represented by read-only and read-write type optical disks. An object of the present invention is to provide a focus control device which is excellent in various focus pull-in operations and control characteristics and which realizes a stable focus control loop.

[0008]

In order to solve the above problems, a focus control apparatus of the present invention records at least information on an optical recording medium represented by at least two types of read-only and read / write type optical disks. Alternatively, in a device that performs either reproduction, an optical head that irradiates a recording medium with a light beam, drives an objective lens to move the focal position of the light beam, and outputs the deviation of the focal position as a focus error signal, and a focus Compensating means for stabilizing the control loop, up-down signal generating means for generating a command signal for moving the objective lens of the optical head up and down, and switching means for switching between the compensating means and the output of the up-down signal generating means. Drive means for amplifying the output of the switching means and driving the optical head; Of noise of at least two types of noise signals, and a noise removing means for switching the noise removing characteristics by a characteristic switching signal, a comparing means for comparing the focus error signal with a constant voltage value, and the comparing means. A pulse width measuring means for measuring the pulse width, a calculating means for generating a characteristic switching signal according to the measured value of the pulse width, and an output of the calculating means or a recording medium identification for identifying two or more types of optical recording media. Have means,
The output of the recording medium identification means is used as the characteristic switching signal, and a timing generation means for determining a focus pull-in position by a noise-free focus error signal and generating a focus pull-in timing is provided.

[0009]

With the above structure, even when a plurality of types of recording media are used, the type of the recording medium is discriminated by the recording medium discriminating means, or the focus error signal is compared with a constant voltage value, and the pulse output from the comparing means. Since the characteristics of the noise removing means are changed according to the width measurement value, even if the frequency of the noise component superimposed on the focus error signal differs depending on the recording medium of different types, or the fundamental frequency component of the focus error signal differs, The noise component can be sufficiently removed without attenuating the basic component of the error signal.

For example, when a recordable / reproducible optical disc and a read-only optical disc such as a CD are used, when the recordable / reproducible optical disc is used, the cutoff frequency of the noise removing means is set low. It is possible to sufficiently remove the noise due to the address portion on the disk, and since the amount of surface wobbling is small, the moving speed of the focal position of the light beam is not large, and the basic component of the S-shaped focus error signal is the noise removing means. The focus error signal amplitude can be measured accurately without being attenuated by, and when the read-only optical disc is used, the basic component of the focus error signal is not attenuated by setting the cutoff frequency of the noise elimination means high, In addition, since the frequency band of the noise component that is superimposed on the focus error signal is high, the noise Can be removed can be measured accurate focus error signal amplitude.

Therefore, since the amplitude of the focus error signal can be accurately measured even when a plurality of discs are used, it is possible to accurately set the pull-in level and the gain varying means set by the focus error signal amplitude. it can. As a result, stable and excellent control performance can be realized by stable pull-in operation of focus control and appropriate gain setting of the focus control loop.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a focus control device according to the present invention, and FIG. 2 is a noise removing means 17-1, 17 shown in FIG.
2 and a circuit diagram of the noise removal characteristic switching means, FIG. 3 is a waveform diagram of a focus error signal, and FIG. 4 is a focus pull-in timing diagram in the embodiment.

In FIG. 1, 10 is an optical head for irradiating a disk with a light beam, which drives an objective lens 10a by a drive signal to move the focus position of the light beam, and a focus error signal which is a deviation of the focus position. Is output. Further, 11 is a gain varying means for changing the gain of the focus error signal output from the optical head to set the focus error signal amplitude to an appropriate level and adjusting the gain of the focus control loop, and 12 is a stable focus control loop. Compensating means, 13 is an up-down signal generating means for generating a signal for moving the objective lens of the optical head up and down, 14 is a switching means for switching the outputs of the compensating means 12 and the up-down signal generating means 13, and 15 is a switching means 14. Driving means for amplifying the output to drive the optical head, 16 is a disc identifying means for discriminating the type of the disc, 17-1 and 17-2 are noise removing means for removing noise contained in the output of the gain varying means 11, 20 Is a noise removal feature that switches appropriate noise removal means according to the output of the disc identification means 16. Switching means, 1
Reference numeral 8 is a focus error signal amplitude measuring means for measuring the output amplitude of the focus error signal noise-removed by an appropriate noise removing means, and 19 is a pull-in timing generating means for outputting a switching signal to the switching means 14.

First, the disc identifying means 16 identifies the type of disc to be used. The noise removing means 17-1 or 17 depending on the identification result of the disc identifying means.
-2 is set by the noise elimination characteristic switching means 20 so that the noise elimination characteristic becomes appropriate. For example, as in a recording / reproducing optical disk, noise of a relatively low frequency component is superimposed on the focus error signal due to the address portion engraved on the disk, and since the disk surface shake amount is not large, the focus of the light beam due to surface shake of the disk In the case of an optical disc in which the moving speed is low, that is, the frequency component of the basic component of the focus error signal is low, the noise removing means 1
Set the cutoff frequency of 7 low. Further, like a read-only optical disk such as a CD, the noise component superimposed on the focus error signal is due to the information pits already recorded and has a high frequency band, but the amount of surface wobbling of the disk is large, so the focus of the light beam is large. The movement speed of the position is high, and S
When the frequency of the basic component of the character-shaped focus error signal is high, the cutoff frequency of the noise removing means is set high. As a specific circuit example, a resistor R1 capacitor C1 as shown in FIG. 2, a resistor R2 capacitor C2 and a buffer amplifier A2 which have the same configuration as the buffer amplifier A1 but have different values,
Further, the signal of A1 and A2 can be constituted by the switch of the switching means for switching according to the output of the disc identification means, but the invention is not limited to this.

Next, the pull-in timing generating means 19 issues a command to the switching means 14 to select the output of the up / down signal generating means 13. The up / down signal generating means 13 outputs a command signal for moving the objective lens 10a of the optical head 10 up and down, for example, a triangular wave signal or a rectangular wave signal as shown in FIG. 4B, and the command signal is switched. It is inputted to the driving means 15 through the means 14, is power-amplified by the driving means, and is then inputted to the optical head. The objective lens 10a of the optical head 10 moves up and down according to the output signal of the up / down signal generating means 13 and outputs the deviation of the focal position of the light beam as a focus error signal as shown in FIG. 4 (e). When the focus error signal is enlarged, it has a waveform as shown in FIG. 3A, and noise is superimposed due to the influence of the address portion and data pits on the disk 1. The focus error signal output from the optical head 10 passes through the gain varying means 11 and is noise-removed by the noise removing means 17-1, 17-2, and the focus error signal is switched by the noise removing characteristic switching means 20 for switching the appropriate noise removing means. The noise component is attenuated without attenuating the basic component of the above, and is input to the pull-in timing generating means 19 and the focus error signal amplitude measuring means 18. The focus error signal amplitude measuring means 18 measures the signal amplitude of the focus error signal and inputs the measurement result to the gain varying means 11 to obtain the focus error signal amplitude measured so that the amplitude of the focus error signal becomes an appropriate level. The gain of the gain changing means 11 is changed accordingly. Further, the outputs of the focus error signal amplitude measuring means 18 and the disc identifying means 16 are inputted to the pull-in timing generating means 19 to set the focus pull-in level for generating the timing for closing the focus control loop in consideration of the time delay at the time of switching the pull-in operation. Set. Similarly, the up / down signal generating means 13 outputs the up / down command signal again, and the switching means 14,
It is applied to the optical head 10 through the driving means 15, and the focal position of the optical head 10 moves. The focus error signal is input to the pull-in timing generating means 19 through the gain varying means 11 and the noise removing means 17, is compared with the focus pull-in level set previously, and is pulled in by the pull-in timing generating means 19 when a predetermined level is reached. A command is output to the switching means 14, the output of the up / down signal generating means 13 is cut off, the output of the compensating means 12 is selected, and the focus control loop is closed. A focus error signal, which is the deviation of the focus position of the light beam, is sequentially input to the optical head 10 through the gain varying means 11, the compensating means 12, the switching means 14, and the driving means 15, and the objective lens is moved so as to eliminate the deviation of the focus position. Let By the above operation, the focus control loop is closed, the focus of the light beam is focused on the disc, and thereafter the information recording / reproducing operation is performed.

Although a specific example of the disc identifying means in the above embodiment is not shown, the disc containing cartridge is used as a recording / reproducing type by utilizing the discriminating hole of the cartridge containing the disc.
A disc without a cartridge is identified as a read-only disc such as a CD, or the reflectance of the disc recording surface is measured using a photocoupler or the amount of reflected light while the objective lens of the optical head is up or down is measured. There is a method of identifying a low recording type as a recording / reproducing type and a high reflectance type as a reproducing only type. As another method, the S-shaped focus error can be pulsed at an appropriate specific voltage level, for example, a point where 0V is crossed, and the pulse width can be measured and calculated to replace the identification means. This is a method focusing on the amount of surface wobbling, not the type of disk. When the pulse width is short, the surface wobbling is large because the S-shaped detection distance is passed in a short time, and conversely long. In this case, the surface wobbling is small, and when the pulse width is less than a certain pulse width, the disc identification means can be replaced by switching to a high cutoff frequency of the noise elimination means.

Even when a plurality of types of discs are used as described above, since the disc types are discriminated by the disc discriminating means and the characteristics of the noise eliminating means are changed, the discs of different types are superimposed on the focus error signal. Even when the frequency of the noise component to be generated is different or the surface wobbling amount of the disc is different, the noise component can be sufficiently removed without attenuating the basic component of the focus error signal.

For example, when a recordable / reproducible optical disc and a read-only optical disc such as a CD are used, when the recordable / reproducible optical disc is used, the cutoff frequency of the noise removing means is set low. It is possible to sufficiently remove the noise due to the address portion on the disk, and since the amount of surface wobbling is small, the moving speed of the focal position of the light beam is not large, and the basic component of the S-shaped focus error signal is the noise removing means. The focus error signal amplitude can be measured accurately without being attenuated by, and when the read-only optical disc is used, the basic component of the focus error signal is not attenuated by setting the cutoff frequency of the noise elimination means high, In addition, since the frequency band of the noise component that is superimposed on the focus error signal is high, the noise Can be removed can be measured accurate focus error signal amplitude.

Therefore, even when a plurality of discs are used, the amplitude of the focus error signal can be accurately measured, so that the pull-in level set by the focus error signal amplitude and the gain varying means can be set accurately. it can. As a result, stable and excellent control performance can be realized by stable pull-in operation of focus control and appropriate gain setting of the focus control loop.

When the noise removal characteristics are switched as described above, the detection delay time slightly changes depending on the characteristics of the removing means, and therefore, in conjunction with the switching, the comparator level for pulsing the S-shape in the pull-in timing generating means. It is an effective means for stabilizing the pull-in that the pull-in detection time is absorbed by changing the.

Further, although the present embodiment has been described by using the optical disk device, it is applied to an optical card or the like having a large number of tracks for recording and reproducing information, and applying this to a device for recording and reproducing by using light. It is also obvious that it is possible.

[0023]

As described above, according to the present invention, even when a plurality of types of discs are used, the types of the discs are discriminated by the disc discriminating means and the characteristics of the noise eliminating means are changed. Even if the frequency of the noise component superimposed on the focus error signal differs depending on the disc, or the amount of surface wobbling of the disc differs, the noise component can be sufficiently removed without attenuating the basic component of the focus error signal. Since the amplitude of the focus error signal can be accurately measured even when using a disc, it is possible to accurately set the pull-in level and the gain varying means set by the focus error signal amplitude. Focus control pull-in operation and appropriate focus control loop gain setting. By those that can achieve excellent control performance stable.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a focus control device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of noise elimination means 17-1 and 17-2 and noise elimination characteristic switching means shown in FIG.

FIG. 3 is a waveform diagram of a focus error signal

FIG. 4 is a timing chart of focus pull-in in the first embodiment.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Optical head 11 Gain varying means 12 Compensating means 13 Up-down signal generating means 14 Switching means 15 Driving means 16 Disk identifying means 17-1 Noise removing means 1 17-2 Noise removing means 2 18 Focus error signal amplitude measuring means 19 Pulling timing Generating means 20 Noise removal characteristic switching means 50 Optical head 51 Gain varying means 52 Compensating means 53 Up-down signal generating means 54 Switching means 55 Driving means 57 Noise removing means 58 Focus error signal amplitude measuring means 59 Pull-in timing generating means

Claims (10)

[Claims] 1. An optical head that irradiates a recording medium with a light beam to drive an objective lens to move the focus position of the light beam, and outputs the deviation of the focus position as a focus error signal, and a stable focus control loop. Compensating means, an up / down signal generating means for generating a command signal for moving the objective lens of the optical head up and down, a switching means for switching between the compensating means and the output of the up / down signal generating means, and the switching means. Driving means for amplifying the output of the optical head and driving the optical head, and noise removing means for switching at least two types of noise of the focus error signal and switching the noise removing characteristics by a characteristic switching signal; The focus pull-in position is determined by the focus error signal Focus control apparatus comprising: a timing generation unit pull generates a ring. 2. The focus error signal amplitude measuring means for measuring the amplitude of the focus error signal noise-removed by the noise removing means, and the gain varying means between the optical head and the compensating means. 2. The focus control device according to claim 1, wherein the focus pull-in position is determined by the output of the amplitude measuring means. 3. The focus according to claim 1, further comprising recording medium identification means for identifying two or more types of optical recording media, and the output of the recording medium identification means being a characteristic switching signal. Control device. 4. The focus control device according to claim 3, wherein the output of the recording medium identification means is determined by a recording / reproducing optical recording medium or a reproduction-only optical recording medium. 5. The focus control device according to claim 3, wherein the output of the recording medium identification means is determined by a recording format. 6. A focus control apparatus according to claim 3, wherein the output of said recording medium identification means is determined by the reflectance of the optical recording medium. 7. The focus control device according to claim 3, wherein the output of the recording medium identification means is determined by the frequency band of noise of the optical recording medium. 8. Comparing means for comparing a focus error signal with a constant voltage value, pulse width measuring means for measuring the pulse width of the comparing means, and calculation for generating a characteristic switching signal according to the measured value of the pulse width. 8. The focus control device according to claim 1, further comprising means, wherein the output of the arithmetic means is the characteristic switching signal. 9. A comparing means for comparing a focus error signal output from the noise removing means with a constant voltage value, a pulse width measuring means for measuring a pulse width of the comparing means, and a characteristic according to the measured value of the pulse width. It has a calculation means for generating a switching signal, and is fixed to one of the noise elimination characteristics until the pulse width measurement result is obtained, and after the pulse width measurement result is obtained, the output of the calculation means is used as the characteristic switching signal. The focus control device according to any one of claims 1 to 7, wherein the noise removal characteristic is switched according to a measurement result. 10. The focus control device according to claim 2, wherein the focus pull-in position is determined by the output of the recording identifying means and the focus error signal amplitude measuring means.