JPH10334470A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set an optical disk and a variety of optical disks having different specifications to be a reproducing state capable of exactly reproducing information with a low error rate independent of the reflectivity of the optical disk. SOLUTION: In an optical disk device converging a light beam from a light source 1 on an optical disk 6 through a converging means and reproducing information recorded in the optical disk 6, an amplitude level decision circuit 26 for deciding the amplitude level of a signal being generated, based on a reflected light beam from the optical disk 6, is provided. The light output power of the light source 1 is changed over so as to suit for the disk in accordance with the decided output of the amplitude level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk drive capable of reading information from various types of optical disks.

[0002]

2. Description of the Related Art As is well known, a compact disk (C
As represented by D) and a laser disk (LD), an optical disk device that reproduces information using a laser beam is widely used. Recently, the optical disk device has been used as a storage device of a computer. Accordingly, the family of CDs includes not only read-only CD-ROMs, but also CD-Rs that can be written only once and CD-Rs that can rewrite recorded information.
Disks such as W have begun to spread rapidly.

[0003] These discs have different disc specifications such as a different reflectivity from conventional CDs. Conventional disc drives cannot reproduce, or even reproduce, CD-RW discs with low reflectivity. Even so, there is a problem that a large number of errors occur in read information due to a low reproduction signal level.

FIG. 15 shows a configuration of an information reproducing section of a conventional optical disk device. A laser light emitted from a semiconductor laser is emitted from a light source 1 that emits a semiconductor laser. The laser light is divided into a diffraction grating 2, a beam splitter 3 for separating reflected light, a collimator lens 4 for obtaining parallel light,
The recording layer of the optical disc 6 is irradiated as a beam spot through the objective lens 5 that obtains converged light. The reflected light reflected from the optical disk 6 enters the photodetector 8 via the objective lens 5, the collimator lens 4, the beam splitter 3, and the cylindrical lens 7. The signal photoelectrically converted by the photodetector 8 is input to an output signal processing unit 9. Photodetector 8
Has a main photodetector that receives a main light beam on a light receiving surface divided into four parts, and two sub photodetectors that receive two sub light beams on respective light receiving surfaces. The laser control unit 10 controls the laser output to keep a constant value.

The light beam indicating the focus error is applied to the reflected light of the cylindrical lens 7 so that the reflected light has an astigmatism effect, and irradiates the light receiving surface of the photodetector 8 divided into four parts. Then, a change in the shape of the light beam caused by the defocus of the minute spot on the optical disk is detected on the light receiving surface, and a focus error is determined. Based on the focus error signal, the objective lens 5 is controlled to move in the optical axis direction to control the focus. The tracking error can be detected based on two sub-light beams generated by the diffraction grating 2. That is, the reflected light of the sub light beam from the optical disk is
The light is photoelectrically converted by a sub-photodetector of the photodetector 8 and converted into a tracking error signal. On the basis of the tracking error signal, the objective lens 5 is finely controlled in a direction intersecting the track to correct the track deviation.

At this time, the laser output of the light source 1 and the output of the photodetector 8 are amplified so that the output level of the reproduced signal satisfies the S / N required for accurately reading the recorded information. The percentage is set.

In the laser control unit 10, the laser output is detected by a photodetector 11 for monitoring, and the detected output is converted into a voltage by a current-voltage conversion circuit 12 and input to a comparison circuit 13 to generate a reference voltage. It is compared with the reference voltage from unit 14. Then, the difference voltage is input to the drive circuit 15, whereby the output of the light source 1 is controlled. As a result, the laser output becomes an output proportional to the reference voltage.

[0008]

According to the above-mentioned conventional optical disk apparatus, when an optical disk having a low reflectance is loaded and reproduced, only a signal output corresponding to the reflectance is obtained. As a result, there is a problem that the reproduction signal level is low and the signal cannot be read continuously, or even if the signal is read, the quality of the reproduction signal is poor and many data errors occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk apparatus capable of accurately reproducing information with a low error rate if an optical disk has correctly recorded information irrespective of the reflectivity of the optical disk.

It is another object of the present invention to provide an optical disk apparatus capable of accurately reproducing information with a low error rate regardless of the reflectance even for various types of optical disks having different specifications (for example, different substrate thicknesses).

[0011]

According to the present invention, in order to achieve the above object, the name of an optical disk loaded in an apparatus is determined from a signal generated from the optical disk based on reflected light, and the reflectance is low. When it is determined that an optical disk is loaded, the laser output is increased. Also, when a gain switching function is provided for the output of the photodetector that detects the reflected light from the optical disk, by using this function together, even for an optical disk whose reflectance is significantly low, A read signal output level is obtained at an appropriate level.

This prevents the quality of the reproduced signal from deteriorating.
Information can always be reproduced accurately. The signals used to determine the family name of the optical disc include a playback signal,
Any one of a focus error signal, a tracking error, and the like, or a signal obtained by combining these can be used.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an embodiment of the present invention, and FIG. 2 is a timing chart shown to explain the operation. FIG. 3 shows another embodiment of the present invention, and FIG. 4 is a timing chart shown for explaining the operation of the apparatus shown in FIG.

The optical disk apparatus shown in FIGS. 1 and 3 detects the light reflection level of the loaded optical disk, and when it is determined that the reflectance is low, increases the laser output of the light source to reduce the signal output. Try to prevent. The difference between the two devices is the difference in the method of setting the laser output, and the purpose is the same. Therefore, the same parts are denoted by the same reference numerals.

The optical disk 6 is held by a chucking means such as a magnet chuck with respect to a spindle motor fixed to a base (not shown), and is stably rotated by the spindle motor during reproduction.

A laser light emitted from a semiconductor laser is emitted from a light source 1, and the laser light is obtained as a diffraction grating 2, a beam splitter 3 for separating reflected light, a collimator lens 4 for obtaining parallel light, and a focused light. The recording layer of the optical disc 6 is irradiated as a beam spot through the objective lens 5. The reflected light reflected from the optical disk 6 enters the photodetector 8 via the objective lens 5, the collimator lens 4, the beam splitter 3, and the cylindrical lens 7. The signal photoelectrically converted by the photodetector 8 is input to an output signal processing unit 9. The photodetector 8 includes four main photodetectors that receive a main light beam on a light receiving surface arranged so as to be divided into four parts, and two photodetectors that are arranged before and after the main photodetector. It has two sub-photodetectors received on the surface. The output signal processing unit 9 has a current-voltage conversion circuit 9a for converting a current signal from each photodetector into a voltage.
The output of a is input to the output signal operation circuit 9b.

In the output signal calculation circuit 9b, a focus error signal, a tracking error signal, and a reproduction signal are obtained by subjecting an output signal from each photodetector to a predetermined calculation process.

The light beam indicating the focus error is applied to the reflected light of the cylindrical lens 7 so that the reflected light has an astigmatism effect. Then, a change in the shape of the light beam caused by the defocus of the minute spot on the optical disk is detected on the light receiving surface, and a focus error is determined. Based on the focus error signal, the objective lens 5 is controlled to move in the optical axis direction to control the focus. The tracking error can be detected based on two sub-light beams generated by the diffraction grating 2. That is, the reflected light of the sub light beam from the optical disk is
The tracking error signal is obtained by photoelectrically converting the two sub-photodetectors of the photodetector 8 and taking the difference. On the basis of the tracking error signal, the objective lens 5 is finely controlled in a direction intersecting the track to correct the track deviation. The reproduction signal is obtained by adding the outputs of the four main photodetectors.

In the laser control section 20, the laser output is detected by a photodetector 21 for monitoring, and the detected output is converted into a voltage by a current / voltage (I / V) conversion circuit 12 and input to a servo circuit 23. Then, the reference voltage is compared with the reference voltage from the reference voltage generator 24. And the difference voltage is the driving circuit 1
5 to control the output of the light source 1. As a result, the laser output becomes an output proportional to the reference voltage. Here, the reference voltage of the reference voltage generator 24 can be switched by a determination output from the signal level determination circuit 26. Signal level determination circuit 26
For example, the reproduction signal is input to the.

The operation specific to the present invention will be described with reference to FIG. Now, it is assumed that an optical disk having a low reflectance is loaded in the apparatus. It should be noted that a timing control signal is given from a system control unit (not shown) to the circuits of each unit. When the laser light source 1 is turned on, the reference voltage of the optical output (1a) level is supplied from the reference voltage generator 24 to the servo circuit 23.
Supplied to Then, the servo circuit 23 and the drive circuit 25
Controls the laser output of the light source 1 so that the reference voltage becomes equal to the output voltage from the current-voltage conversion circuit 22. Next, focus control is turned on. Then, a reproduced signal that changes according to the relative eccentricity between the disk and the pickup is obtained. After it is confirmed that the focus control is operating normally, the tracking control is turned on. Then, a reproduced signal of an envelope having a constant amplitude is obtained. When the tracking control becomes stable, the signal level is determined.

The signal level determining circuit 26 determines the signal level of the reproduced signal. The determination is performed by comparing a preset disc reflectivity determination level with a reproduction signal level. In this example, since an optical disk having a low reflectance is loaded, the reproduction signal level is lower than the disk reflectance determination level. At this time, the signal level determination circuit 26 obtains a low level determination output. Then, the reference voltage generator 24 supplies the reference voltage of the optical output (2a) level to the servo circuit 23. Then, the servo circuit 23 and the drive circuit 25 control the laser output of the light source 1 so that the reference voltage and the output voltage from the current-voltage conversion circuit 22 become equal. The light output (2a) level is set to about twice the light output (1a) level.

After switching the light output intensity in this manner, a second signal level determination is performed after a while. At this time, since the reproduction signal (signal level judgment signal) is larger than the disc reflectance judgment level, the signal level judgment circuit 26
Is at a high level. At this time, switching to the reference voltage is not performed, and signal reproduction in the normal reproduction mode is performed.

If the reflectivity of the optical disc loaded in the optical disc apparatus is at the level of an ordinary read-only optical disc, that is, if the reflectivity is high, the signal level judgment circuit 26 performs the first signal level judgment. Since the determination output is at the high level, the reference voltage is not switched, and signal reproduction in the normal reproduction mode is performed from the beginning.

Further, by controlling the laser power in accordance with the reflectivity as described above, it is possible to prevent the laser unit from generating unnecessary heat.

FIG. 3 shows another embodiment of the present invention.
The difference from the device of FIG.
The switching of the reference voltage is not performed. The output of the current / voltage conversion circuit 22 is input to the servo circuit 23 via the gain switching section 27, and the signal level determination signal from the signal level determination circuit 26 is used as a control signal for the gain switching section 22. It is that you are. Other parts are the same as those of the apparatus of FIG. 1 described above.

The operation specific to this apparatus will be described with reference to FIG. Now, it is assumed that an optical disk having a low reflectance is loaded in the apparatus. It should be noted that a timing control signal is given from a system control unit (not shown) to the circuits of each unit. When the laser light source 1 is turned on, a gain setting voltage for setting the light output (1a) level is supplied to the servo circuit 23. Then, the servo circuit 23 and the drive circuit 25
Controls the laser output of the light source 1 so that the reference voltage and the set voltage from the current-voltage conversion circuit 22 become equal. Next, focus control is turned on. After it is confirmed that the focus control is operating normally, the tracking control is turned on. Then, a reproduced signal of an envelope having a constant amplitude is obtained. When the tracking control becomes stable, the signal level is determined.

The signal level determining circuit 26 determines the signal level of the reproduced signal. The determination is performed by comparing a preset disc reflectivity determination level with a reproduction signal level. In this example, since an optical disk having a low reflectance is loaded, the reproduction signal level is lower than the disk reflectance determination level. At this time, the signal level determination circuit 26 obtains a low level determination output. Then, the gain switching unit 27 supplies the set voltage of the optical output (2a) level to the servo circuit 23. Then, servo circuit 2
3. The drive circuit 25 includes the reference voltage and current / voltage conversion circuit 22.
The laser output of the light source 1 is controlled so that the set voltages from the light sources become equal.

After switching the light output in this way, the signal level is determined a second time after a while. At this time, since the reproduction signal (signal level judgment signal) is higher than the disc reflectivity judgment level, the output of the signal level judgment circuit 26 is at a high level. At this time, switching to the reference voltage is not performed, and signal reproduction in the normal reproduction mode is performed.

In the above embodiment, the reproduction signal is input to the signal level determination circuit 26, but a focus error signal or a tracking error signal may be used. FIG. 5 shows an example of input and output of the signal level determination circuit 26 when a focus error signal is used. In this case, the laser output is set at the time of the focus search before the focus control of FIGS. 2 and 4 is performed.

FIG. 6 shows an example of input and output of the signal level judgment circuit 26 when a tracking error signal is used. In this case, the focus control of FIGS. 2 and 4 is stabilized, and before the next tracking control is performed, a tracking error signal is determined and the laser output is set.

In the present invention, a focus error signal, a tracking error signal, an information reproduction signal, etc. may be used alone, or a plurality of these signals may be used in combination. This makes it possible to enhance the determination ability.

In the above embodiment, it is assumed that the optical disk device is a disk reproduction device of the CD family series, and a case where a loaded optical disk has a different reflectance has been described. This is because CD-DA and CD-R, which have high reflectivity, in the disk family of the CD family.
OM, CD-R discs with low reflectivity
This is because there is a D-RW.

However, the present invention can be used not only for such a disk device but also as a function for automatically setting an optimum laser beam for an optical disk device for reproducing an optical disk having different specifications.

[0034] DVDs have emerged from CDs, which have been common as conventional disks. CDs and DVDs have different specifications such as different disk thicknesses and recording densities, and it is impossible to reproduce both optical disks with the same optical disk device as before. Therefore, an optical head device having a function of covering a difference in the thickness of a disk has been developed. For example, Japanese Patent Application Laid-Open No. 6-195743 by the present applicant discloses a technique in which two laser light sources having different wavelengths are prepared as light sources and each light source is switched according to a difference in specifications.

The present invention can be applied to such an optical disk device. The optical disk device shown in FIG. 7 will be described. This optical disk device includes an objective lens 5
Dichroic prism 5
0 is used. This dichroic prism 50
Has a function of guiding the laser light from the light source 1 and the laser light from the light source to the same optical path on the disk side, and also has a function of guiding the reflected light reflected from the disk side to the respective emitting sides. Have.

The laser light for CD is emitted from the light source 1, passes through the dichroic prism 50, and irradiates the disk via the objective lens 5. The light reflected from the disc is transmitted to the objective lens 5, the dichroic prism 5
The light passes through 0, passes through the beam splitter 3, passes through the cylindrical lens 7, and enters the photodetector 8. The configuration for a CD is the same as in the above-described embodiment.

The laser output setting section 61 and the disc discriminating circuit 62 correspond to, for example, the signal servo circuit 23, the reference voltage generating section 23, the signal level judging circuit 26 and the like in FIG. The laser light for DVD is emitted from the light source 41 and enters the objective lens 5 via the beam splitter 43, the collimator lens 44, and the dichroic prism 50.
The light reflected from the disk passes through the objective lens 5, the dichroic prism 50, the beam splitter 43, and the cylindrical lens 47, and enters the photodetector 48.
The output of the photodetector 48 is converted into a voltage signal by a voltage-current conversion circuit 49a, and is input to an output signal calculation circuit 49b.

Reference numeral 121 denotes a monitor photodetector. The detection output of the photodetector 121 is a current-voltage conversion circuit 12.
The signal is converted into a voltage signal at 2 and input to the laser output setting unit 126. The laser output setting section 126 corresponds to the servo circuit 23 and the reference voltage generation section 24 in FIG.

The above-described optical disk device can determine the type of the optical disk having different specifications, determine the CD-RW having a low reflectance included in the CD series, and set an appropriate laser beam for this.

The disc discriminating operation will be described with reference to FIGS. First, when a disc is loaded in the apparatus, the apparatus is set to a mode for reproducing the thin optical disc 70. Although the figure shows a thin optical disk (DVD) and a CD at the same time, it goes without saying that either one is actually loaded. Since the mode is the reproduction mode of the thin optical disk, the light source 41 is turned on. Thereafter, the objective lens 5 is scanned in the optical axis direction to obtain an operation called focus search. When this focus search is performed, a focus error signal called an S-shaped curve can be obtained near the information recording surface (near the focal position) of the optical disk loaded in the optical disk device. By comparing the focus error signal with the reflectance determination level, an optimal light source and laser output can be set. FIG.
Indicates that the light source 41 is first turned on, then the light source 41 is turned off, the light source 1 is turned on, and the laser output is switched in the direction of increasing the power and increasing the gain.

FIG. 9 schematically shows the relationship between each laser beam of the light source 1 and the light source 41 and the focus error signal. The thin optical disk 70 includes a one-layer disk and a two-layer disk. When a single-layer disc is loaded, the signal output is large and a single S-shaped curve is obtained. Meanwhile, 2
In the case of a layered disc, the signal output is small because the reflectance is low, and a double S-shaped curve is obtained. On the other hand, CD
When the laser light of the light source 41 is used, the signal output is extremely small irrespective of the reflectance of the loaded disk due to the spherical aberration due to the difference in the thickness of the disk. Becomes Further, when a disk having a low reflectance is loaded, the signal output becomes smaller.

As described above, depending on the type of disc, S
Difference in the size of the curve and one or two S curves
Since there is a difference between the two types, it is possible to determine whether a CD-series disc is loaded or a thin optical disc is loaded. When it is determined that a CD-series disc is loaded, the operation is switched from the light source 41 to the light source 1 to obtain the operation described with reference to FIGS. Can be set.

The above-described disc discrimination method is a method in which the light source 41 for a thin optical disc is first turned on to obtain an S-shaped curve. However, the determination is not limited to this, and another method may be used.

That is, the description will be made with reference to FIG. Now, it is assumed that a compact disk (CD) 6 is loaded in the optical disk device. In this state,
When a light source for one CD is turned on and a focus search operation (operation of gradually moving the objective lens 5 from a position sufficiently far from the optical disk) is performed, a focus error signal 203 is obtained. At the same time, when the light source for the other DVD is turned on and the focus search operation is performed,
A focus error signal 204 is obtained. Here, the focus error signals are compared, and the relationship that the amplitude ratio is the focus error signal 203> the focus error signal 204 is obtained, so that the type of the loaded disc can be determined. This is because (the focus error signal 204 is small), even if the CD is irradiated with the laser light of the optical system on the light source 41 side optimized for the thin optical disk, the reflected light from the CD having a large thickness has a large spherical aberration. As a result, the output amplitude of the focus error signal decreases. This focus error signal 2
The relationship between 03 and 204 does not change even if a CD-RW having a lower reflectance than a normal CD is loaded in the optical disk device.

Next, a case where a thin optical disk is loaded in the optical disk device will be described. Also in this case, as described above, each light source is turned on, and the focus search operation is performed in each reproduction system. When the light source on the CD side is turned on, the focus error signal 20
1 is obtained and when the light source on the DVD side is turned on,
A focus error signal 202 is obtained.

In this case, the focus error signal 20
2> focus error signal 201 This signal output relationship does not change even if the thin optical disk has two layers. Therefore, by examining the magnitude relationship between the focus error signal a on the signal processing side for the CD and the focus error signal b on the signal processing side for the thin optical disc, it is possible to determine which disc is mounted.

In setting the laser output, the same control as in the above-described embodiment is executed. The above embodiment has an advantage that two focus error signals can be obtained simultaneously by simultaneously operating the signal processing system on the CD side and the signal processing system on the DVD side. The two focus error signals a and b have an appearance difference Δd.
2, Δd1, it is necessary to perform amplitude comparison and the like in consideration of this difference.

FIG. 11 shows still another embodiment of the present invention. Parts corresponding to those of the optical disk device of FIG. 7 are denoted by the same reference numerals. The laser light emitted from the light source 1 is applied to the optical disk via the diffraction grating 2, the dichroic prism 50, the collimator lens 4, the dichroic prism 51, and the objective lens 5. Light source 4
The laser light emitted from 1 is applied to the optical disk via the dichroic prism 50, the collimator lens 4, the dichroic prism 51, and the objective lens 5.

The light reflected from the optical disk is input to the photodetector 8 via the objective lens 5, dichroic prism 51, condenser lens 52, and cylindrical lens 53. The photoelectric conversion output detected by the photodetector 8 is voltage-converted by a current-voltage conversion circuit 9a, and the voltage signal is input to an output signal calculation circuit 9b via a gain switching section 9c.
In the output signal calculation circuit 9b, a tracking error signal for a CD and a tracking error signal for a thin optical disk are generated, and a focus error signal and a reproduction signal are generated.

The focus error signal at the time of the focus search of the output signal calculation circuit 9b is input to the disc discrimination circuit 54. The disk determination circuit 54 can output an on / off control signal for the first light source 1 and an output switching signal. The disc discriminating circuit 54 can output an on / off control signal for the second light source 41, and can also supply a gain switching signal to the gain switching section 9c.

The optical disk device of FIG. 11 differs from the optical disk device of FIG. 7 in that although it has two light sources, the system for detecting the reflected light from the optical disk is of the type shown in FIG.
In this case, a CD and a thin optical disk are commonly used. First, when reproducing a thin optical disk, the gain switching section 9 is used.
The level of the signal input to the output signal operation circuit 9b is increased by increasing the gain of c. Further, when reproducing an optical disk having a low reflectance in the CD reproduction mode, the gain of the gain switching section 9c is increased and the output of the light source 1 is increased. Thereby, higher quality signal reproduction can be obtained.

FIGS. 12 and 13 are signal waveform diagrams for explaining the operation until the laser output and the reproduction mode are determined when a CD having a low reflectivity is mounted on the optical disk device.

That is, when a disc is loaded into the apparatus, the apparatus is set to a mode for reproducing the thin optical disc 70. Although the figure shows a thin disk (DVD) and a CD at the same time, it goes without saying that either one is actually loaded. Since the mode is the reproduction mode of the thin optical disk, the light source 41 is turned on. Thereafter, the objective lens 5 is scanned in the optical axis direction to perform a focus search. When this focus search is performed, a focus error signal called an S-shaped curve can be obtained near the information recording surface (near the focal position) of the optical disk loaded in the optical disk device. By comparing the focus error signal with the reflectance determination level, an optimal light source and laser output can be set. In the example of FIG. 12, the light source 41 is first turned on, and then the light source 41 is turned off.
This indicates that the light source 1 has been turned on, and there has been a switch in the direction of increasing the power of the laser output and increasing the gain.

FIG. 13 schematically shows the relationship between each laser beam of the light source 1 and the light source 41 and the focus error signal. The thin disk 70 includes a one-layer disk and a two-layer disk. When a single-layer disc is loaded, the signal output is large and a single S-shaped curve is obtained. On the other hand, in the case of a two-layer disc, the signal output is small because the reflectance is low, and a double S-shaped curve is obtained. On the other hand, CD
When the laser light of the light source 41 is used, the signal output is extremely small irrespective of the reflectance of the loaded disk due to the spherical aberration due to the difference in the thickness of the disk. Becomes Further, when a disk having a low reflectance is loaded, the signal output becomes smaller.

As described above, depending on the type of disc, S
Difference in the size of the curve and one or two S curves
Since there is a difference between the two types, it is possible to determine whether a CD-series disc is loaded or a thin optical disc is loaded. When it is determined that a CD-series disc is loaded, the operation is switched from the light source 41 to the light source 1 to obtain the operation described with reference to FIGS. Can be set.

The above-described disc discriminating method is a method of first turning on the light source 41 for a thin disc to obtain an S-shaped curve. However, the determination is not limited to this, and another method may be used.

FIG. 14 shows an example of a method for determining the type of a disk. In this method, the two light sources 1 and 41 are turned on, and a focus search operation for gradually approaching a position sufficiently far from the optical disk is performed. In this case, an S-shaped curve signal as shown in FIG. 14B can be obtained. That is, when a CD disc is loaded, the focus error signals 207 and 208 of the S-shaped curve are used.
Can be obtained. At this time, the focus error signal 207 is greater than the focus error signal 208. This is because when the light source 1 optimized for a thin optical disk is turned on, the reflected light from a CD having a large disk thickness has a large spherical aberration, so that the output amplitude of the focus error signal becomes small. It is. This magnitude relationship does not change even when a CD-RW having a lower reflectivity than a normal CD is mounted on an optical disk device.

On the other hand, when a thin optical disk is loaded, focus error signals 205 and 206 are obtained. At this time, the relationship of focus error signal 205 <focus error signal 206 is satisfied. The relationship of this signal is
Even when a two-layered thin optical disk is loaded, the signal level of both is reduced, but the magnitude relationship remains the same.

From the above-described principle, at the same time, the first light source and
The focus search operation is performed by simultaneously turning on the second light source, and the type of the mounted optical disc can be determined based on the magnitude relationship between the levels of the focus error signal and the order of appearance. After the type of the optical disc is determined as described above, the optimum laser output power is set as in the embodiment described above.

[0060]

As described above, according to the present invention,
Regardless of the reflectivity of the optical disc, it is possible to set a state in which information can be accurately reproduced with a low error rate on an optical disc on which information is correctly recorded. In addition, it is possible to obtain a state in which information can be accurately reproduced with a low error rate regardless of the reflectance even for various types of optical disks having different specifications (for example, different substrate thicknesses).

[Brief description of the drawings]

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

FIG. 2 is a timing chart shown for explaining the operation of the device of FIG. 1;

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

FIG. 4 is a timing chart shown for explaining the operation of the device of FIG. 3;

FIG. 5 is a timing chart shown for explaining still another operation example of the device of the present invention.

FIG. 6 is a timing chart shown for explaining still another operation example of the device of the present invention.

FIG. 7 is a diagram showing still another embodiment of the present invention.

FIG. 8 is a signal waveform diagram shown for explaining the operation of the device of FIG. 7;

9 is a signal waveform diagram shown for explaining the operation of the device of FIG. 7;

FIG. 10 is an explanatory diagram for explaining a disk discriminating operation of the apparatus of FIG. 7;

FIG. 11 is a diagram showing still another embodiment of the present invention.

FIG. 12 is a signal waveform diagram shown for explaining the operation of the device of FIG. 11;

FIG. 13 is a signal waveform diagram shown for explaining the operation of the device of FIG. 11;

14 is an explanatory diagram shown to explain a disk discriminating operation of the apparatus of FIG. 11;

FIG. 15 is a diagram showing a conventional optical disk device.

[Explanation of symbols]

1, 41: light source, 2: diffraction grating, 3, 43: beam splitter, 4, 44: collimator lens, 5: objective lens, 6: optical disk, 7, 47: cylindrical lens, 8, 48: photodetector, 9 ... output signal processing unit, 21 ...
Monitoring photodetectors, 22, 122 ... current-voltage conversion circuits,
23: servo circuit, 24: reference voltage generator, 25, 12
5: drive circuit, 26: signal level determination circuit, 27: gain switching unit, 50: dichroic prism, 61, 126
... Laser output setting unit, 62 ... Disk discriminating circuit, 70 ...
Thin optical disk.

Claims (7)

[Claims] 1. A light source and an optical disk apparatus for focusing a light beam from the light source on an optical disk via a focusing means and reproducing information recorded on the optical disk, wherein the light beam is reflected on the optical disk based on the reflected light from the optical disk. An optical disc apparatus comprising: an amplitude level determining unit that determines an amplitude level of a signal generated by the above; and a switching unit that switches an optical output intensity of the light source according to an output of the amplitude level determining unit. 2. The signal used for the amplitude determination by the amplitude level determination means is one of an information reproduction signal, a focus error signal, and a tracking error signal, or a plurality of signals obtained by combining these. An optical disk device according to the above. 3. The change in the amplitude level of a signal used for the amplitude determination by the amplitude level determination means is caused by a difference in reflectance between optical disks having different purposes, and the switching means outputs the maximum signal output. The signal amplitude level of the other optical disc is set to 1 for the signal amplitude level of the obtained optical disc.
2. The optical disk device according to claim 1, wherein the optical output intensity of the light source is controlled to such an extent that the light output intensity is suppressed to within 1/2. 4. A first and a second light source; light beam combining means for combining light beams from the first and second light sources on substantially the same optical path; A light beam converging means for converging a light beam from the light source, and converging a light beam from the second light source on a second optical disc having a thickness different from that of the first optical disc and having a high recording density; Light detection means for receiving reflected light from the first and second optical discs; and a light beam emitted from the second light source and generated based on reflected light from a mounted optical disc currently mounted on the apparatus. First determining means for determining the amplitude level of the read signal, and determining the type of the mounted optical disk by the first determining means. If it is determined that the optical disk is the first optical disk, the first optical disk is replaced with the second light source. The first light Second determining means for determining an amplitude level of a signal generated based on reflected light from the mounted optical disk obtained by emitting a light beam from the optical disk, and the first determining means according to an output of the second determining means. Means for controlling the light output intensity of the light source and / or the amplification of the output of the light detecting means for receiving the reflected light. 5. A first and second light source; a light beam combining means for combining light beams from the first and second light sources on substantially the same optical path; A light beam converging means for converging a light beam from the light source, and converging a light beam from the second light source on a second optical disc having a thickness different from that of the first optical disc and having a high recording density; First and second light detecting means for respectively receiving the reflected light from the first and second optical discs; and light beams simultaneously emitted from the first and second light sources, Determining means for comparing and determining the amplitude levels of the first and second signals based on the first and second reflected lights obtained from the optical disk mounted on the current apparatus obtained based on the light source; and the light beam focusing means Of the objective lens in the direction of the optical axis Based on the predetermined condition determination result of the determination unit obtained as described above, either one of use of the first or second light source and one of the output of the first or second light detection unit An optical disk device comprising: a control unit for determining a selection. 6. A first and a second light source; a light beam combining means for combining light beams from the first and the second light sources on substantially the same optical path; A light beam converging means for converging a light beam from the light source, and converging a light beam from the second light source on a second optical disc having a thickness different from that of the first optical disc and having a high recording density; First and second light detecting means for respectively receiving reflected light from a mounted optical disk currently mounted on the apparatus; and light beams simultaneously emitted from the first and second light sources, Determining means for comparing and determining the amplitude levels of the first and second signals based on the first and second reflected lights from the mounted optical disk obtained based on the light source, and an objective lens of the light beam focusing means. Control the movement in the axial direction, Control means for determining use of either the first or second light source based on the obtained predetermined condition determination result of the determination means, and using an output of the light detection means as a reproduction signal. An optical disc device characterized by the above-mentioned. 7. An optical disk device, wherein the optical output intensity of a laser light source for irradiating the optical disk can be switched in a plurality of stages according to the difference in the reflectance of the optical disk mounted on the device.