JPH10124914A - Optical disk reproducing device and optical disk reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce various kinds of optical disks by automatically setting a light source, a photodetector and a tracking error generating system used to obtain a best reproducing signal according to the kind of a loaded optical disk. SOLUTION: Luminous fluxes from semiconductor lasers (LDs) 3 and 4 having different oscillation wavelengths are projected to an optical disk via optical systems and photodetectors 7 and 8 output signals according to its reflected light quantities. Based on these signals, a microcomputer 35 determines the kind of the optical disk, switches changeover switches 12 and 33 and selects one of two means for generating tracking error signals. Thus, the LD 3 and 4 used for reproducing the optical disk, the gain of a reproducing system and a tracking control system are set to values most suitable for the reproduction of the optical disk. Thus, the increase of a circuit quantity is suppressed to a minimum and various kinds of optical disks are reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for reproducing an optical disk on which information data is recorded. In particular, the present invention relates to a disc reproducing apparatus and method suitable for reproducing by one apparatus by discriminating various types of optical discs on which information data is recorded from differences in reflectance.

[0002]

2. Description of the Related Art As a medium in which information data is recorded on an optical disk, for example, there is a compact disk (hereinafter, referred to as a CD). To play pits recorded on a CD,
For example, using an optical head equipped with a light source having a wavelength of 780 nm such as a laser diode and an objective lens having a numerical aperture of 0.45, laser light is focused on the pit surface of a CD, and the intensity of the reflected light is converted into an electric signal. Convert. At this time, it is necessary to perform focusing control for keeping the light spot where the laser beam is focused on the pit surface and tracking control for always tracing the pit row. Among them, for example, an error signal by the astigmatism method can be used for the focusing control, and a tracking error signal by the three spot method can be used for the tracking control. The above-described CD reproduction technology is described in detail in "Introduction to Video Discs and DAD Corona".

On the other hand, as a medium for recording information data on an optical disk by modulating the output power of a laser, for example, there is a CD write once (hereinafter, referred to as CD-R). In order to reproduce the information recorded on the CD-R, similarly to the reproduction of the CD, an optical head equipped with a laser diode having a wavelength of 780 nm and an objective lens having a numerical aperture of 0.45 is used. The laser light is condensed on the recording surface, and the intensity of the reflected light is converted into an electric signal.
However, unlike a CD, a write-once optical disc such as a CD-R has a reflective film (recording film).
And the reflectance of the recording surface greatly depends on the wavelength of the irradiated laser light. Therefore, in order to reproduce information recorded on a CD-R, it is necessary to use a laser having a wavelength of 780 nm.

There is a phase change type disk as an optical disk capable of recording and erasing. In order to reproduce information recorded on a phase change type disc, an optical head having a laser diode of a predetermined wavelength and an objective lens of a predetermined numerical aperture is used. Convert to a signal. However, the reflectivity of the recording surface of a phase-change optical disc is generally lower than that of a CD by half or less. For this reason, in order to reproduce information recorded on a phase change type disc, it is necessary to increase the gain of the reproducing system as compared with the case of reproducing a CD.

Further, as a high-density optical disk having a higher recording density than a CD, for example, there is a DVD. To reproduce pits recorded on a DVD, for example, a wavelength of 650
Using an optical head equipped with a laser diode of nm and an objective lens having a numerical aperture of 0.6, a laser beam is focused on the pit surface of a DVD in the same manner as in the reproduction of a CD, and the intensity of the reflected light is determined by an electric signal. Convert to However, in the DVD, the interval between the pit rows (track interval) is shorter than the track interval of the CD, so that the tracking error signal by the three-spot method cannot be used. That is, at three spots set at the track interval of the CD,
DVD tracking error signal cannot be obtained.
Instead, a DVD uses a tracking error signal by a phase difference method as disclosed in, for example, JP-A-57-181433, for tracking control.

As described above, there are various types of recording media for reproducing recorded information data by detecting the intensity of light reflected from an optical disk. Further, in the future, there is a possibility that a wider variety of discs such as a write-once disc of a DVD, a phase-change disc, a disc having a higher density than a DVD, and the like are mixed and distributed.

However, since the characteristics of the optical disks are different from each other as described above, there has been no optical disk reproducing apparatus that can reproduce all the optical disks by one unit.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk reproducing apparatus and a reproducing method capable of reproducing all the optical disks described above.

[0009]

In order to achieve the object of the present invention, an optical disk reproducing apparatus for reproducing an optical disk on which information data is optically recorded is provided with at least two light sources having different oscillation wavelengths and each light source. Light detecting means for outputting a signal corresponding to the amount of reflected light when the light beam is applied to the optical disk, and determining means for determining the type of the optical disk based on the signal corresponding to the amount of reflected light. Further, at least two tracking error signal generating means for generating different tracking error signals from the output of the light detecting means, and the tracking error signal generating means corresponding to the discrimination result of the discriminating means among the tracking error signal generating means are selected. And a tracking error signal selecting means. As a result, the wavelength of the light source used for reproducing the optical disk, the gain of the reproducing system, and the method of the tracking error signal used for the tracking control can be set to the most suitable set values for reproducing the loaded disk. Can be reproduced.

Further, an irradiation position control means for controlling the irradiation position of the light source is provided. When discriminating the type of the optical disk, the irradiation position control means sets the irradiation position of the light source to a radius of 25 mm or less of the optical disk, and reflects the light at that position. The discriminating means discriminates the type of the optical disc based on a signal corresponding to the amount of light, and emission power control means for controlling the emission power of the light source is provided. When discriminating the type of the optical disc, the type of the optical disc is determined by the emission power control means. The irradiation power at the time of discrimination is switched with the emission power at the time of reproducing the optical disc, the discriminating means discriminates the type of the optical disc, and when discriminating the type of the optical disc, the discriminating means changes the disc type while rotating the recording disk. Discriminating, by having an organic dye-based recording film, the wavelength dependence of the reflectance Can be reproduced to determine the type of the optical disc without destroying recorded on have optical disk data.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an optical disk reproducing apparatus according to the present invention. In the figure, 1
Is an optical disk, 3 is a first semiconductor laser (hereinafter, referred to as LD) as a light source having a first oscillation wavelength λ1, 4 is a second LD as a light source having a second oscillation wavelength λ2, 5, and 6 are the LDs. Are driven so as to have a predetermined light emission output, respectively.
PC, 7) and 8) are first and second photodetectors which respectively receive the light beams emitted from the LDs 3 and 4 and convert them into electric signals, and 9, 10 and 11 denote light beams from the photodetectors. I / V conversion circuits for converting an output into a voltage value, 12 and 33 are changeover switches for selectively switching among a plurality of inputs and leading to an output, and 13 and 32 are variable amplifiers whose gains can be changed according to a control signal. Circuits, 14, 17, 19, 24, 2
5, 26 and 28 are addition circuits, 15 is a variable waveform equalization circuit whose equalization coefficient can be switched according to a control signal, 16, 27,
29 is a waveform shaping circuit for shaping the waveform of the input analog signal; 18, 20, and 34 are low-pass filters;
1, 99, and 31 are subtraction circuits, 23 is a level detection circuit that compares an input signal voltage with a predetermined voltage value, and 35 is a microcomputer (hereinafter, referred to as a microcomputer).

The APC circuit 5 receives a control signal 101 from the microcomputer 35, and drives the LD 3 when the signal level is "H" level, for example. LD3 is an APC circuit 5
It oscillates at the predetermined output power set by. LD3
Of light 110 emitted from the optical disk 1 enter the optical disc 1 via the optical element, and the light flux reflected by the optical disk 1 again enters the photodetector 7 via the optical element (note that in FIG. The configuration of the optical element is omitted because it does not directly relate to the present invention). The signal of each area from the photodetector 7 is input to the I / V conversion circuit 9, I / V converted, and input to the X input terminal of the changeover switch 12.

On the other hand, the APC circuit 6 receives the control signal 102 from the microcomputer 35 and drives the LD 4 when the signal level is "H" level, for example. LD4 is AP
Oscillates at a predetermined output power set by the C circuit 6. The light beam 111 emitted from the LD 4 enters the optical disc 1 via the optical element, and the light beam reflected by the optical disc 1 enters the photodetector 8 again via the optical element. It is assumed that the photodetector 8 includes, for example, regions 2E and 2F in which ± first-order light beams of the light beam 111 diffracted by the diffraction grating are incident. The signals of the respective areas from the photodetector 8 are output to the I / V conversion circuit 10 for the areas 2A, 2B, 2C and 2D, and to the I / V conversion circuit 11 for the areas 2E and 2F.
And are subjected to I / V conversion. The output of the I / V conversion circuit 11 is input to a subtractor 31, and after taking the difference between the two signals, is input to the Z input terminal of a changeover switch 33 via a variable amplifier circuit 32. This signal is a three-spot signal which is a well-known tracking error signal.
The output of the I / V conversion circuit 10 is input to a Y input terminal of a changeover switch 12.

The changeover switch 12 receives the control signal 103 from the microcomputer 35. For example, when the signal level is "L" level, the X input terminal is selected and connected to the output terminal. Is at the "H" level, the Y input terminal is selected and connected to the output terminal. The output of the changeover switch 12 is supplied to adders 14, 17, 19, 24, 25, 26, 2 through a variable amplifier circuit 13.
8, respectively. The adder 14 adds all the signals in the four areas, and the added signal is used as the variable waveform equalizer 1
5 is input. The output of the variable waveform equalizing circuit 15 is data sliced by a waveform shaping circuit 16 and subsequently passed to a digital signal processing circuit. Further, adders 17 and 19
In this case, signals of two regions each having a diagonal positional relationship among signals of four regions are added. The outputs of the two adders 17 and 19 are input to a subtractor 21 via low-pass filters 18 and 20, respectively, and the difference between the two signals is calculated to obtain a focusing error signal 105 by a well-known astigmatism method. obtain.

On the other hand, the outputs of the low-pass filters 18 and 20 are also input to an adder 22, and the added sum signal is input to a level detection circuit 23. Level detection circuit 23
Then, the voltage peak value of the input signal is compared with a predetermined threshold value, and the magnitude determination signal 106 is output to the microcomputer 35.

In addition, the adders 26 and 28 add signals of two areas, each of which has a positional relationship parallel to a track on the optical disc 1 among signals of four areas. The outputs of both adders are input to a subtractor 26, and a difference between the two signals is obtained to obtain a push-pull signal 107 which is a well-known tracking error signal. The push-pull signal 107 is input to the X input terminal of the changeover switch 33.

Further, the adders 26 and 28 add signals of two regions, each of which has a diagonal positional relationship among the signals of the four regions. The output signals of both adders are input to waveform shaping circuits 27 and 29, respectively, and shaped into digital signals. The output signals of the two waveform shaping circuits are input to a phase comparison circuit 30, and a voltage proportional to the phase difference between the two signals is output, so that a phase difference method (hereinafter referred to as DPD) signal, which is a well-known tracking error signal, is output. Obtain 108.
Although omitted in the figure, if necessary,
Before addition is performed by the adders 26 and 28, for example, the phase relationship between the signal from the A region and the signal from the C region is matched using a variable delay line or the like. Similarly, the phase relationship between the signal from the region B and the signal from the region D is matched to remove a so-called offset component of the tracking error signal. Also, if necessary, before waveform shaping by the waveform shaping circuits 27 and 29, waveform equalization is performed using a waveform equalizing circuit to detect a phase difference with a high S / N over the entire RF signal band. To be able to do The DPD signal 108 thus obtained is input to the Y input terminal of the changeover switch 33.

As described above, the three kinds of tracking error signals of the push-pull signal 107, the DPD signal 108, and the spot signal 109 are input to the changeover switch 33, and the signal corresponding to the selection control signal 112 from the microcomputer 35 is input. Are selectively connected to the output. The output of the changeover switch 33 becomes a tracking error signal via a low-pass filter 34.

An optical disk capable of reproducing various types of optical disks by having the above-described configuration and setting a light source and the like to be used in accordance with the loaded optical disk so that each switch is optimal. It becomes a playback device. In addition, an increase in the amount of circuits due to such multi-disk compatibility can be minimized.

Next, the procedure for setting the above-mentioned changeover switch and the like during the initial setting operation will be described. FIG. 2 is a diagram showing signal waveforms of respective units in the block diagram of FIG. 1, and FIG. 3 is a setting table of each changeover switch according to the output of the level detection circuit 23 and a gain changeover of the variable amplifier circuit. The operation when various disks are mounted will be described in detail with reference to both drawings.

The following five cases are considered as types of the optical disk 1. That is, (1) an optical disk having an aluminum reflective film or the like and having low reflectance wavelength dependency and high reflectance, and (2) an optical disk having an organic dye-based layer and having extremely large reflectance wavelength dependency, The second wavelength λ2 (LD
(3) The first wavelength λ1 (LD3) of an optical disc set so as to obtain an optimum reflectance at an oscillation wavelength of (4) and a disc having an organic dye-based layer and having extremely large reflectance wavelength dependency. (4) an optical disk having a phase change film or a semi-transmissive film and having a low reflectance wavelength dependency and a low reflectivity; 5) when no optical disk is loaded.

When the optical disk 1 is mounted on the turntable, first, the microcomputer 35 sets the control signal 101 to "H" level and the control signal 102 to "L" level. As a result, the APC circuit 5 is turned on, and the LD 3 oscillates at the first wavelength λ1 with a predetermined output power. At this time, the selection direction of the changeover switch 12 is set to the X input terminal side. Here, an objective lens (not shown) is driven in a direction approaching the optical disc 1 (only the control voltage for the objective lens position is shown in FIG. 2). Time t = T1
At 1, the light spot on the optical disc 1 is in focus, and the amount of light returning to the photodetector 7 is also maximum. At this time, the maximum value of the input signal of the level detection circuit 23 is V11X, V12X, V13X, V14X, V14X, as shown in FIG.
It becomes 0. Note that, in FIG. 5, as an example of V12X, a level smaller than the threshold value Vth1 is shown for convenience, but there is no particular problem even if V12X> Vth1.

Next, the microcomputer 35 sets the control signal 101 to "L" level and the control signal 102 to "H" level. As a result, the APC circuit 6 is turned on, and the LD 4 oscillates at a predetermined output power at the second wavelength λ2. At this time, the selection direction of the changeover switch 12 is set to the Y input terminal side. Here, the objective lens is driven again in a direction to approach the optical disc 1. At time t = T12,
The light spot on the optical disk 1 is in focus, and the amount of light returning to the photodetector 8 is also maximum. The maximum value of the input signal of the level detection circuit 23 at this time is as described in the above (1) to (5).
In the case of (1), as shown in FIG.
1Y, V12Y, V13Y, V14Y, and 0. Note that, in FIG. 5, for convenience, V13Y is a level lower than the threshold value Vth1, but there is no particular problem even if V13Y> Vth1.

On the other hand, the level detection circuit 23 compares a predetermined threshold value with the maximum value of the input signal, and if the predetermined threshold value is larger, the "L" level is determined. If the maximum value is larger, an “H” level is output to the microcomputer 35. Note that a plurality of threshold values can be set. For example, in the case of the present embodiment, two threshold values Vth1 are set.
And Vth2 are set.

FIG. 3A summarizes the relationship between the maximum value of the input signal and Vth1 and Vth2 shown in FIG. 2E. Here, the microcomputer 35 sets the light source to be used, the connection of the changeover switch 12, and the setting of the switching gain of the variable amplifier circuits 13 and 32, as shown in FIG. That is, in the case of (2), the APC circuit 6 is driven (using the LD 4), and the changeover switch 12 is connected to the X input terminal side. In the case of (3), the APC circuit 5 is driven (using the LD3), and the changeover switch 12 is connected to the Y input terminal side. On the other hand, in the cases of (1) and (4), there is no difference in the output of the level detection circuit 23 regardless of which of the light sources LD3 and LD4 is used. Therefore, either light source may be used. However, if an optimal light source based on a reproduced signal is specified by a digital signal processing unit (not shown), it is followed. In the case of (4), the gain of the variable amplifier circuits 13 and 32 is set to G2 (G1
<G2). Further, in the case of (5), it is considered that the optical disk is not loaded, and the reproducing operation is not performed until the so-called disk ejecting operation is performed, that is, both the light sources LD3 and LD4 are turned off.

The connection direction of the changeover switch 33 can be set by the following two methods. one,
In the above cases (1) to (5), a tracking error signal to be used is determined in advance.
As an example, (1) a DPD signal, (2) a three-spot signal, (3) a DPD signal, (4) a push-pull signal,
(5) No particular setting is made, and the most suitable setting is set on the assumption of the type of the optical disc mounted in the end. Thereby, according to the output of the level detection circuit 23,
The connection direction of the changeover switch 33 is set. The other is a method of detecting the amplitude of a tracking error signal at the time of crossing a track by each method, and selecting a tracking error signal having the maximum amplitude value at this time. First, only the focusing control is performed, and the objective lens is vibrated in a direction perpendicular to the pit row. For example, although not shown, a level detection circuit for inputting the output of the LPF 34 is provided, and the connection setting of the changeover switch 33 is such that the X input terminal, the Y input terminal, and the Z input terminal are switched in a time sharing manner. The input terminal from which the amplitude value is obtained may be set as the final connection direction of the changeover switch 33.

By the above operation, the above-mentioned (1) to (5)
In this case, it is possible to select an optimal light source, a gain, and a method of generating a tracking error signal.

FIG. 4 is a diagram showing signal waveforms at various parts in the block diagram of FIG. 1, and is an example using timing different from that in FIG.

When the optical disk 1 is mounted on the turntable, first, the microcomputer 35 sets both the control signals 101 and 102 to "H" level. As a result, the APC circuits 5 and 6 are both turned on, and the LD 3 oscillates at the first wavelength and the LD 4 oscillates at the predetermined output power at the second wavelength. Further, the changeover switch 12 switches the selection direction between the X input terminal side and the Y input terminal side for a predetermined period ΔT1 and ΔT2. Here, an objective lens (not shown) is driven in a direction to approach the optical disc 1.
At time t = T21, the light spot on the optical disk 1 is in focus, and the amount of light returning to the photodetectors 7 and 8 is also maximum. At this time, the maximum value of the input signal of the level detection circuit 23 in the above-mentioned cases (1) to (5) is (1) is V21X, V21Y,
(2) is V22X, V22Y, (3) is V23X, V2
3Y, (4) is V24X, V24Y, and (5) is 0,0. Here, V21X = V11X, V21Y = V11
Y, V22X = V12X, V22Y = V12Y, V23
X = V13X, V23Y = V13Y, V24X = V14
Since X and V24Y = V14Y, the subsequent operation is the same as the operation described with reference to FIGS. Note that FIG.
Similarly, the magnitude relationship between V22X and V23Y and Vth1 does not matter in particular.

As described above, by using the timing of this embodiment, the objective lens can be moved in the optical axis direction only once, and the light source to be used, the connection of the changeover switch 12, and the switching of the variable amplifier circuits 13 and 32 can be achieved. The time required to set the gain can be reduced as compared with the case of FIG. In this example, the periods ΔT1 and ΔT2 are set to be sufficiently shorter than the period ΔT3 in which the signal changes with the movement of the objective lens in the optical axis direction. Further, for convenience of explanation, the time when V21X is taken and the time when V21Y are taken are the same time (time t = T21).
21Y is not necessarily at the same time. That is, if a value near the maximum value can be detected, there is no problem in achieving the object of the present invention.

FIG. 5 is a block diagram showing a second embodiment of the optical disk reproducing apparatus according to the present invention. In this figure, the difference from the block diagram shown in FIG.
2. A level detection circuit 36 having an error signal as an input is provided instead of the level detection circuit 23.

FIG. 6 is a diagram showing signal waveforms at various parts in the block diagram of FIG. (A), (b),
The signals shown in (c) and (d) are the same as those described with reference to FIG. Time t = T31
At, the light spot on the optical disc 1 is in focus,
Near the time, the error signal input to the level detection circuit 36 has a maximum value and a minimum value. The amplitude value obtained from (maximum value)-(minimum value) is V31 as shown in FIG. 6E in the above-mentioned cases (1) to (5).
X, V32X, V33X, V34X, 0. Also,
Similarly, at time t = T32, V31Y,
V32Y, V33Y, V34Y, and 0.

Here, if Vth1 and Vth2 are set so that V31X>Vth2>V34X>Vth1> V32X, the light source to be used, connection of the changeover switch 12, and The switching gain of the variable amplifier circuits 13 and 32 can be set. The level detection circuit 36
The light source to be used, the connection of the changeover switch 12, and the setting of the switching gain of the variable amplifier circuits 13 and 32 can also be performed by comparing the extreme value of the error signal, which is the input of the above, with a predetermined threshold value. It is more preferable to switch the light source or the like by comparing the amplitude value obtained from (maximum value)-(minimum value) so that there is no erroneous detection even if the offset is applied.

FIG. 7 is a block diagram showing a third embodiment of the optical disk reproducing apparatus according to the present invention. In this figure, the point different from the block diagram shown in FIG. 1 is that the variable amplifier circuits 13 and 32 are eliminated, and the set value of the output power can be changed in the APC circuits 5 and 6 by inputting an external control signal. That is, the variable APC circuits 38 and 39 have been changed.

In this embodiment, the operation after the optical disk is mounted is exactly the same as the operation described with reference to FIG. 2 or FIG. The feature of this embodiment is that the gain switching is performed not by the variable amplifier circuit but by switching the output power of the LD3 or LD4. Thereby, the circuit amount can be reduced as compared with the case where the variable amplifier circuit is used after the I / V converter. Also, I
There is also an advantage that the characteristics of the circuit portion after the / V converter can be made constant irrespective of the gain switching selection mode.

By the way, in each of the above embodiments, the recording type optical disk, that is, the above (2), (3), (4)
When the optical disk is mounted, it is necessary to prevent data on the disk from being erroneously destroyed during the initial setting operation shown in FIGS. In particular, (2), (3)
Since the organic dye-based recording layer is made of a material or the like on the assumption that reproduction is performed at a predetermined wavelength, the reflectance is low and the absorption rate is high at wavelengths other than the predetermined wavelength. In FIG.
As an example of the disk of (2), the spectral characteristics of the reflectance and the absorptance of the disk in which λ2 = 780 nm, which is the same as the reproduction wavelength of a CD, are shown. The reflectance around the wavelength of 780 nm is 70% or more, while the reflectance is, for example, LD3.
Wavelength λ1 = 650 nm, the wavelength 650 nm
The reflectance around 20% or less. On the other hand, the absorptance is not more than 20% near 780 nm, but is not less than 70% near 650 nm, which is about 3 to 5 times. This means that at a wavelength of 650 nm, data can be recorded on the recording layer with a laser output that is one third to one fifth of the laser output at a wavelength of 780 nm. In other words, similarly, the data recorded on the recording layer is destroyed by the laser output of 1/3 to 1/5. Therefore, if the upper limit of the reproduction laser output at a wavelength of 780 nm is P1 mW, the wavelength 65
The upper limit of the reproduction laser output at 0 nm is (P1 / 3 to P
1/5) mW. Here, P1 as the upper limit of the laser output when reproducing a CD or the like is usually 1 mW.
Therefore, the upper limit of the reproduction laser output at a wavelength of 650 nm may be set to 0.33 mW or less. More preferably, the value at which the photodetector can detect the reflected light is at least 0.0
Since the power is about 1 mW, the emission power of the laser at the time of disc discrimination may be set to 0.01 mW or more and 0.03 mW or less.

As for the disk of the above (3), the spectral characteristics of the reflectance and the absorptance of the disk in which λ1 = 650 nm, for example, have a predetermined reflectance near a wavelength of 650 nm, while the LD4 has a predetermined reflectance. Wavelength λ2
The reflectance around = 780 nm generally differs from its predetermined reflectance. Here, for example, assuming a disk having a low reflectance near the wavelength of 780 nm, the absorption is 650 nm.
It is low near the wavelength and high near the wavelength of 780 nm. Therefore, when the upper limit of the reproduction laser output at the wavelength of 650 nm is P2 mW, the upper limit of the reproduction laser output at the wavelength of 780 nm needs to be set lower than P2 mW.

From this, at least during the above-mentioned initial setting operation, the output power of the LD 3 and LD 4 is set to the minimum value among the upper limit values of the reproduction laser outputs of all the discs that may be mounted. , 1/3 to 1 /
It must be set to 5 or less.

As a method for measuring the amount of light emitted from the optical head 2, there is a method as shown in FIG.

FIG. 11 is a diagram showing a method for measuring the amount of light emitted from the optical head 2. Referring to FIG.
Is a photodetector for entering light, 302 is a support member for supporting the photodetector 301, and 303 is a so-called optical power meter. The measuring method is described below. The position of the support member 302 is adjusted so that all the convergent light emitted from the objective lens or the like of the optical head enters the plane of the photodetector 301. That is, the position of the support member is adjusted so that the positional relationship shown in FIGS. For example, in the positional relationship shown in (c), all light emitted from the optical head is detected by the photodetector 30.
Since the light is not incident on 1, a value lower than the actual amount of emitted light is measured. Next, the sensitivity of the optical power meter is corrected (in the optical power meter described later, when the wavelength of the received light is input as numerical data, the correction is automatically performed), and the displayed value is read.

As the optical power meter 303,
For example, Advantest OPTICALPOWER MULTIMETER TQ
8215, as a plug-in unit including the photodetector 301 and the support member 302, for example, OPTICAL BLO
There is CK TQ82021.

As a method of preventing the recorded data from being destroyed, it is effective to perform the above-described initialization operation in an area other than the information recording area. For example, in the case of the above-mentioned disc (2), in the case of a CD-R which is compatible with a CD as an example, the information recording area used by the user is r = 25 to 58 mm when the disc radius is r. is there. Therefore, if the initial setting operation is performed at r ≦ 25 mm or r ≧ 58 mm, even if the recording layer is damaged, the data in the information recording area can be prevented from being destroyed. More preferably, the reproduction of the optical disk is usually performed from the inner peripheral side to the outer peripheral side. Therefore, the optical pickup 2 may be set to r ≦ 25 mm in order to save the trouble of moving the optical pickup 2 when discriminating the disk.

Further, if the above-mentioned initial setting operation is performed while rotating the optical disk, the light beam emitted from the optical pickup 2 will not be applied to one point of the information recording area. The recorded data will not be destroyed.

In the meantime, in each of the above-described embodiments, after the initial setting operation has been completed and the setting of the respective changeover switches has been determined, when performing the disk reproducing operation, the output power of the LD3 and LD4 is initialized. You may make it switch to higher power than inside. As a result, it is possible to prevent the reproduction signal S / N from being reduced due to circuit noise or the like.

FIG. 9 shows an example of an APC circuit capable of switching output power used at this time. In the figure, 2
01 is a laser diode, 202 is a photodetector to which a part of the output light of the laser diode is incident, 203 is a variable resistor capable of setting a plurality of resistance values according to a control signal, 2
04 is a reference voltage V1, 205 is a differential amplifier circuit, and 206 is a drive circuit. The operation will be described below.

When the ON / OFF control signals 101 and 102 become “H” level, the drive circuit 206 starts outputting a drive current and drives the laser diode 201. When the driven current exceeds a predetermined threshold current, the laser diode 201 starts laser oscillation. In the photodetector 202, a part of the oscillating light amount is incident, and a current proportional to the incident light amount flows. The current and the variable resistor 203
Is connected to one input of the differential amplifier circuit 205, and the reference voltage V1 is connected to the other input of the differential amplifier circuit 205. The drive circuit 206 drives the laser diode 201 so that the output of the differential amplifier circuit 205 becomes zero, so that a desired laser output power can be obtained. Here, if, for example, the resistance value R1 of the variable resistor 203 is set to 前 of the previous value by the output power control signals 113 and 114, the operation is performed so that the current flowing through the photodiode 202 becomes twice the previous value. Will be. As a result, the output power of the laser diode 201 is doubled.

FIG. 10 shows an APC capable of switching output power.
It is another example of the circuit. The difference from FIG.
Reference numeral 3 denotes a fixed resistor 207 and reference voltage 204 denotes a variable voltage source whose voltage can be set according to a control signal. The output power control signals 113 and 114 allow the reference voltage value V
By changing 1, the output power of the laser diode 201 can be switched.

Next, a specific example of the set values of the threshold values Vth1 and Vth2 in the level detection operation will be described. Assuming that the disc of the above (4) is, for example, a CD-E having a data format compatible with the CD, the reflectance is about 15 to 25%, or the disc of the above (4) is, for example, 2%. Assuming a layered DVD disk, the reflectance is about 18 to
30%. On the other hand, as the discs (1), (2) and (3), for example, CD, CD-R, DVD, DV
When DR is assumed, the reflectance is about 45% or more (however, CD-R and DVD-R are reflectance at a predetermined wavelength, respectively). Therefore, Vth2 is set to 30 to 45% in terms of reflectance. Further, Vth1 should be set to 15% or less in terms of reflectance since it is sufficient to be able to determine the above-mentioned state (5) in which no disk is mounted.

In each of the embodiments described above, the LDs 3 and 4 and the photodetectors 7 and 8 are arranged on one optical head 2, but the present invention is not limited to this. Instead, two optical heads each having one set of LD and photodetector may be provided. Further, the present invention is applicable even when the number of LDs and photodetectors is three or more. Furthermore, if the light from each light source can be accurately detected, it is not necessary to provide a photodetector as a pair with each light source.

A dedicated APC circuit is provided for each LD. However, in addition to such a configuration, only one shared APC circuit is provided and connected to each LD via a changeover switch. You may do it. In this case, the timing described with reference to FIG. 4 cannot be used, but the present invention can be applied to other cases.

[0052]

According to the present invention, a light source, a photodetector, and a tracking error generation method to be used can be set so as to obtain the best reproduction signal according to the type of the loaded optical disk. Various types of optical disks can be reproduced. In addition, an increase in the amount of circuits accompanying multi-disk compatibility can be minimized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical disk reproducing apparatus according to the present invention.

FIG. 2 is a signal waveform diagram of each part in FIG.

FIG. 3 is a correspondence table of signal levels of respective parts and setting contents in each optical disc.

FIG. 4 is a signal waveform diagram of each unit in FIG. 1;

FIG. 5 is a block diagram showing a second embodiment of the optical disk reproducing apparatus of the present invention.

FIG. 6 is a signal waveform diagram of each part in FIG.

FIG. 7 is a block diagram showing a third embodiment of the optical disk reproducing apparatus of the present invention.

FIG. 8 is a characteristic diagram showing an example of spectral characteristics of an optical disc.

FIG. 9 is a circuit block diagram illustrating an example of a variable APC circuit.

FIG. 10 is a circuit block diagram showing another example of the variable APC circuit.

FIG. 11 is a diagram showing a positional relationship between an optical head and an optical power meter detection unit.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroshi Endo 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Visual Information Media Division of Hitachi, Ltd. (72) Inventor Jiro Higashi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd. Visual Information Media Division (72) Inventor Koichiro Nishimura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture, Japan Inside Multimedia System Development Headquarters, Hitachi, Ltd. (72) Koichi Hirose Totsuka-ku, Yokohama-shi, Kanagawa 292 Yoshidacho Co., Ltd. Multimedia System Development Division, Hitachi, Ltd.

Claims (14)

[Claims] 1. An optical disk reproducing apparatus for reproducing an optical disk on which information data is optically recorded, comprising: at least two light sources having different oscillation wavelengths; and a reflected light amount when the light beam of each light source is irradiated on the optical disk. An optical disc reproducing apparatus comprising: a light detecting means for outputting a signal corresponding to the signal; and a discriminating means for discriminating the type of the optical disc based on a signal corresponding to the amount of reflected light. 2. At least two tracking error signal generating means for generating a different tracking error signal from an output of the light detecting means, and the tracking error corresponding to the determination result of the determining means among the respective tracking error signal generating means. 2. An optical disk reproducing apparatus according to claim 1, further comprising a tracking error signal selecting means for selecting a signal generating means. 3. A moving means for moving each of the light sources in the optical axis direction, wherein the discriminating means comprises a signal corresponding to a reflected light amount when each of the light sources irradiating the light beam is moved by the moving means. 3. The optical disk reproducing apparatus according to claim 1, wherein the type of said optical disk is determined by comparing each of the maximum values with a predetermined value. 4. A moving means for moving each of said light sources in the direction of the optical axis, and a focusing device for generating a focusing signal for focusing a light beam from each of said light sources on said optical disk based on a signal corresponding to said amount of reflected light. Signal generating means, and the discriminating means compares each extreme value or amplitude value of the focusing signal when the light source irradiating the light beam is moved by the moving means with a predetermined value. 3. The optical disk reproducing apparatus according to claim 1, wherein the type of the optical disk is determined. 5. A light source selecting means for selecting one of the light sources, wherein the light source selecting means sets one of the light sources to the reflected light amount when determining the type of the optical disk. 5. The optical disk reproducing apparatus according to claim 3, wherein a light source different from said one light source is selected after moving to a position where a maximum value, an extreme value or an amplitude value of a corresponding signal can be detected. . 6. A light source selecting means for selecting one of the light sources, wherein the light source selecting means, when judging the type of the optical disk, takes longer than the time when the moving operation of each light source by the moving means is completed. 5. The optical disk reproducing apparatus according to claim 3, wherein a light source for irradiating the optical disk with a light beam in a short time is switched. 7. At least two light sources having different oscillation wavelengths move in the direction of the optical axis, each of the light sources generates a signal corresponding to the amount of reflected light of a light beam irradiated on the optical disk, and the maximum value of each of the signals And discriminating the type of the optical disc by comparing the optical disc with a predetermined value to reproduce the information of the optical disc. 8. At least two light sources having different oscillation wavelengths move in the optical axis direction, and a light beam from each light source is applied to the optical disk by a signal corresponding to a reflected light amount of a light beam emitted from each light source to the optical disk. Generating a focusing signal for focusing by focusing on each other, discriminating the type of the optical disc by comparing an extreme value or an amplitude value of each focusing signal with a predetermined value, and reproducing the information of the optical disc. An optical disk reproducing method characterized by the above-mentioned. 9. When determining the type of the optical disk, one of the light sources moves to a position where a maximum value, an extreme value or an amplitude value of a signal corresponding to the amount of reflected light can be detected, and then the one light source and 9. The method according to claim 7, wherein a different light source is selected. 10. A light source for irradiating the optical disk with a light beam in a time shorter than a time for completing the movement operation of each light source when determining the type of the optical disk. An optical disk reproducing apparatus according to claim 1. 11. A recording disk reproducing apparatus for reproducing a recording disk on which information data is optically recorded, wherein at least two light sources having different oscillation wavelengths and a light beam of each of the light sources is irradiated onto the recording disk. Light detection means for outputting a signal corresponding to the amount of reflected light, and determination means for determining the type of the recording disk based on a signal corresponding to the amount of reflected light when illuminating the recording disk with each light source,
And an irradiation position control means for controlling an irradiation position of the light source.When determining the type of the recording disk, the irradiation position control means sets the irradiation position of the light source to a radius of 25 mm or less of the recording disk, and at this position. A recording disc reproducing apparatus, wherein the discriminating means discriminates the type of the recording disc based on a signal corresponding to the amount of reflected light. 12. A recording disk reproducing apparatus for reproducing a recording disk on which information data is optically recorded, wherein at least two light sources having different oscillation wavelengths and a light beam of each light source are applied to the recording disk. Light detection means for outputting a signal corresponding to the amount of reflected light, and determination means for determining the type of the recording disk based on a signal corresponding to the amount of reflected light when illuminating the recording disk with each light source,
An emission power control unit for controlling the emission power of the light source, and when determining the type of the recording disk, the irradiation power when determining the recording disk by the emission power control unit is used when reproducing the recording disk. A recording disc reproducing apparatus, wherein the discrimination means discriminates the type of the recording disc by switching to an emission power. 13. The recording disk reproducing apparatus according to claim 12, wherein an output power P for determining said recording disk satisfies 0.01 mW ≦ P ≦ 0.33 mW. 14. A recording disk reproducing apparatus for reproducing a recording disk on which information data is optically recorded while rotating the recording disk by a rotating means, wherein at least two light sources having different oscillation wavelengths and the luminous flux of each light source are recorded. Light detection means for outputting a signal corresponding to the amount of reflected light when illuminating the disk, and discrimination for determining the type of the recording disk based on a signal corresponding to the amount of reflected light when illuminating the recording disk by each of the light sources Means for determining the type of the recording disk, wherein the determining means determines the type of the recording disk while the rotating means rotates the recording disk.