JP2001325742A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of a conventional optical pickup device that the pickup device becomes large in a scale due to its structure in which a plurality of light sources and photodetectors are provided and that an output terminal is installed for each photodetector in a conventional optical pickup device for performing information recording, reproduction, etc., for a plurality of optical disks of different specifications. SOLUTION: The optical pickup device of this invention is structured such that a first and second photodetectors 71, 72 are provided which receive reflected beams respectively from beam spots formed on an optical disk by plurality of light sources placed closely to each other, and that the first and second photodetectors 71, 72 share output terminals A-F.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup device, and more particularly to an optical pickup device for recording / reproducing or erasing information on a plurality of information recording media having different specifications and standards.

[0002]

2. Description of the Related Art Techniques for recording, reproducing, or erasing information by irradiating an optical disk, which is an optical information recording medium, with a light beam have been conventionally known as CD (Compact Disk), LD (Laser Disk), Or DVD (Digital Video
Disk), which are widely used in playback devices for various optical disks.

An optical pickup device is used for recording / reproducing or erasing information on / from the optical disk. The optical pickup device includes a light source such as a semiconductor laser chip, a converging optical system including a collimator lens and an objective lens, and a photodetector that receives light reflected from the optical disk.

When information recorded on the optical disk is reproduced, a light beam emitted from the light source is converged by an objective lens to form a beam spot on a recording surface of the optical disk, and a reflected light is returned from the beam spot. By detecting the intensity of light with the photodetector, information written as pits (unevenness) on the recording surface of the optical disc can be read.

[0005] The recording density of such optical discs is becoming increasingly sophisticated, and there are many types of optical discs having different specifications and standards. For example, regarding the pit length, which is a unit in which information is recorded, a CD is about 0.83 μm, while a DVD is about 0.4 μm.
m. As for the interval (track pitch) between the rows in which the pits are formed, CD
Is 1.6 μm whereas DVD is 0.74 μm
m.

In order to detect or form pits that have been miniaturized as described above, it is necessary to reduce the spot diameter r of the beam spot formed on the recording surface of the optical disk. The spot diameter r is determined by the wavelength λ of the light beam used and the numerical aperture NA of the objective lens.
), and can be calculated by the following equation (1). Note that k in the equation is a squeezing coefficient (constant).

(Equation 1)

As can be seen from the above equation, in order to reduce the spot diameter r of the beam spot in order to perform a recording / reproducing operation on an optical disk having a higher recording density, it is necessary to use a light source capable of emitting a light beam having a short wavelength λ. It is necessary to use an objective lens having a large numerical aperture NA. However, when the numerical aperture NA of the objective lens is increased, the disturbance of the beam spot that occurs when the optical disc is inclined with respect to the objective lens tends to increase.

On the other hand, it is known that the turbulence of the beam spot is also affected by the thickness of the substrate on which the optical disk is formed, and the turbulence of the beam spot decreases as the thickness of the substrate decreases. For this reason, an optical disk having a high recording density may be thinner than the conventional substrate. For example, a CD substrate has a thickness of 1.2 mm, while a DVD substrate has a thickness of only 0.6 mm.

Here, a general optical pickup device has a configuration having one light source and one objective lens. Therefore, when an optical pickup device provided with an objective lens having a large numerical aperture NA to support an optical disk having a high recording density (for example, a DVD) is intended to perform recording and reproduction on an optical disk having a thick substrate (for example, a CD). In addition, since the beam spot is largely disturbed when the optical disc is tilted, it is not possible to ensure an accurate recording / reproducing operation.

For the above reasons, an optical pickup device compatible with an optical disk having a high recording density cannot be used commonly for an optical disk having a low recording density in many cases.
Therefore, in order to realize an optical disk device capable of recording / reproducing or erasing information from / to a plurality of optical disks having different specifications and standards, it is necessary to provide a plurality of the optical pickup devices corresponding to the respective light sources. But,
When a plurality of optical pickup devices are provided, there arises a problem that the device scale is enlarged. It is also disadvantageous in terms of cost.

As a technique for solving such a problem and realizing recording / reproducing or erasing of information on a plurality of optical disks having different specifications and standards with a single optical pickup device, the wavelengths of emitted light beams are different. An optical pickup device including a plurality of light sources has been proposed. Note that as the plurality of light sources, a plurality of semiconductor lasers or the like may be provided, or a single semiconductor laser or the like having a plurality of light emitting points may be provided.

Here, regardless of the specifications and standards of the optical disk, in order to detect the reflected light returning from the optical disk with a single photodetector, the light emitting points of a plurality of light sources must be matched with each other. It is necessary to use a common optical system. However, since the light emitting points of the light sources cannot be completely matched, it is actually necessary to separately provide an optical component for correcting the center of the optical axis of the optical system by the distance between the light emitting positions of the light sources. Therefore, this configuration is not very practical because the number of components increases and the manufacturing process becomes complicated.

On the other hand, a configuration in which a plurality of photodetectors are provided in the optical pickup device is also conceivable. FIG. 2 is a schematic diagram showing one configuration example of a conventional optical pickup device. Here, an optical pickup device employing a three-beam method as a tracking error detection method will be described as an example.

The semiconductor laser 1 shown in FIG. 1 has two light emitting points.
The light source 11 and the second light source 12 will be called. The first
The light source 11 and the second light source 12 are arranged at positions close to each other, and have different wavelengths (for example, 650 for DVD).
(about 780 nm for a CD).

The light beam emitted from the first light source 11 is converted by the diffraction grating 2 into one 0-order light (hereinafter, referred to as a main beam) for recording and reproduction and ± 1 order light (hereinafter, a sub-beam) for tracking control. ) Are divided into two light beams. These three light beams are respectively reflected by the half mirror 3 toward the collimating lens 4. In the figure, the main beam and the sub beam are represented by the same straight line.

The light beam that has passed through the collimator lens 4 and has become a substantially parallel light beam is condensed on the optical disk 6 by the objective lens 5. Thus, a beam spot is formed on the recording surface of the optical disk 6. Note that a beam spot formed by the main beam (hereinafter, referred to as a main spot) is located on a center line of a track on which recording information is arranged. On the other hand, the beam spot formed by the two sub-beams (hereinafter, referred to as a sub-spot) is slightly shifted right or left from the center line of the track.

The reflected light from the optical disk 6 follows the optical path opposite to the above, and the objective lens 5, the collimating lens 4
And returns to the half mirror 3. And half mirror 3
The first photodetector 71 disposed on the light receiving element 7 through the
Is incident on.

On the other hand, the light beam emitted from the second light source 12 is similar to the above, and is divided into one main beam and two sub beams by the diffraction grating 2. These three light beams are respectively condensed on the optical disk 6 via the half mirror 3, the collimator lens 4, and the objective lens 5, and a beam spot (main spot and sub spot) is formed on the recording surface.

The reflected light from the optical disk 6 follows the optical path opposite to the above, and the objective lens 5, the collimating lens 4
And returns to the half mirror 3. And half mirror 3
Light detector 72 disposed on the light receiving element 7 through the
Is incident on.

Next, the configuration of the first photodetector 71 and the second photodetector 72 will be described. FIG. 3 is a schematic diagram showing a configuration example of a first photodetector 71 and a second photodetector 72 provided in a conventional optical pickup device. As described above, both the first photodetector 71 and the second photodetector 72 are disposed on the light receiving element 7.

The first photodetector 71 has six detectors 71.
a to 71f. In particular, the detectors 71 a to 71 d constitute a four-segment detector, and the four-segment detector is arranged to detect the reflected light Rx of the main spot formed by the first light source 11. The detectors 71e and 71f are the first light source 1
1 reflected light Ry, Rz of the sub spot formed by
Are respectively detected.

The detectors 71a to 71f are connected to output terminals A to F, which are connection terminals to external amplifiers, via current-voltage conversion circuits (not shown). Accordingly, the detection outputs Sa to S of the detectors 71a to 71f
After the signal f is converted into a signal by the current-voltage conversion circuit, the signal f is sent from the output terminals A to F to the external amplifier.

Similarly, the second photodetector 72 is composed of six detectors 72a to 72f. In particular, the detectors 72a to 72d constitute a four-segment detector, and the four-segment detector is arranged to detect the reflected light Rx 'of the main spot formed by the second light source. In addition, the detectors 72e and 72f
The reflected light R of the sub spot formed by the light source 12
They are arranged to detect y ′ and Rz ′, respectively.

Each of the detectors 72a to 72f is connected to an output terminal A 'to F' which is a connection terminal to an external amplifier via a current-voltage conversion circuit (not shown). Therefore, the detection output S of each of the detectors 72a to 72f
The signals a ′ to Sf ′ are sent out from the output terminals A ′ to F ′ to the external amplifier after signal conversion by the current-voltage conversion circuit.

[0025]

With the optical pickup device having the above-described structure, it is possible to realize recording / reproducing or erasing of information on a plurality of optical disks having different specifications and standards by a single optical pickup device. However, in the conventional configuration, as shown in FIG. 3, the output terminal is provided for each of the plurality of photodetectors, so that the device scale is increased, and the size and weight of the device strongly demanded by the user are reduced. Is unsuitable for achieving

Further, as the number of the output terminals increases, the wiring from the light receiving element to the external amplifier becomes more complicated, so that there is a problem that the working time required for processing the device becomes longer.

The present invention has been made in view of the above problems, and has an optical pickup device capable of recording, reproducing, or erasing information on a plurality of information recording media of different standards while having a small and simple configuration as compared with the related art. It is intended to provide.

[0028]

In order to achieve the above object, in an optical pickup device according to the present invention, a plurality of light sources close to each other and light beams emitted from each light source are converged on an information recording medium. A converging optical system, and a plurality of light detectors for receiving reflected light from the information recording medium, and a light for recording, reproducing, or erasing information on a plurality of information recording media having different standards. In the pickup device, at least one of the plurality of photodetectors may be used.
The pair is configured to share the output terminal.

In the optical pickup device having the above structure,
When each of the photodetectors includes a plurality of detectors, at least one set of the detectors may share an output terminal between the photodetectors. Further, when any one of the plurality of light sources is on, the remaining light sources may be off. Further, among the photodetectors sharing an output terminal, it is preferable that a connection switching means for connecting only the photodetector that has received the reflected light from the information recording medium to the output terminal is provided.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The overall structure and operation of an optical pickup device according to the present invention are substantially the same as those of the conventional optical pickup device shown in FIG. A detailed description will be given focusing on the configuration and operation of the first photodetector 71 and the second photodetector 72, which are characteristic parts of the present invention.

FIG. 1 is a schematic diagram showing one configuration example of a first photodetector 71 and a second photodetector 72 provided in an optical pickup device according to the present invention. As with the previous configuration,
Both the first photodetector 71 and the second photodetector 72 are arranged on the light receiving element 7.

The first photodetector 71 has six detectors 71.
a to 71f. In particular, the detectors 71 a to 71 d constitute a four-segment detector, and the four-segment detector is arranged to detect the reflected light Rx of the main spot formed by the first light source 11. The detectors 71e and 71f are the first light source 1
1 reflected light Ry, Rz of the sub spot formed by
Are respectively detected.

Similarly, the second photodetector 72 is composed of six detectors 72a to 72f. In particular, the detectors 72a to 72d constitute a four-segment detector, and the four-segment detector is arranged to detect the reflected light Rx 'of the main spot formed by the second light source. In addition, the detectors 72e and 72f
The reflected light R of the sub spot formed by the light source 12
They are arranged to detect y ′ and Rz ′, respectively.

Here, in the optical pickup device according to the present invention, switch elements 8a to 8f for connecting only one of the first photodetector 71 and the second photodetector 72 to the output terminals A to F. Is provided.

Each of the detectors 71a to 71f constituting the first photodetector 71 is connected to one input terminal of the switch element 8a to 8f, and each of the detectors 72a to 72f constituting the second photodetector 72 is Switch element 8
a to 8f are connected to other input terminals. The common output terminals of the switch elements 8a to 8f are connected to output terminals A to F, which are connection terminals to external amplifiers, via a current-voltage conversion circuit (not shown).

Therefore, when the switch elements 8a to 8f are switched to the first photodetector 71 side, the outputs Sa to Sf of the detectors 71a to 71f constituting the first photodetector 71 output the currents minus the currents. After the signal is converted by the voltage conversion circuit, it is sent from the output terminals A to F to the external amplifier.

On the contrary, when the switch elements 8a to 8f are switched to the second photodetector 72, the outputs S of the detectors 72a to 72f constituting the second photodetector 72 are changed.
After the signals a ′ to Sf ′ are converted by the current-voltage conversion circuit, the signals are sent from the output terminals A to F to the external amplifier.

The switching operation of the switch elements 8 a to 8 f is controlled by the detector 9. Here, the second
An example in which the switching elements 8a to 8f are switched according to the presence or absence of the output Se 'obtained from the detector 72e constituting the photodetector 72 will be described.
The detector is not limited to e, and any detector that can detect reflected light may be used.

Here, in the optical pickup device of this embodiment, when the first light source 11 is turned on, the second light source 1 is turned on.
2 is turned off, and when the second light source 12 is turned on, the first light source 11 is turned off.

With such a configuration, when the first light detector 71 detects the reflected lights Rx, Ry, Rz, the second light detector 72 detects the reflected lights Rx ′, Ry ′, Rx.
z 'is not detected. Conversely, the second photodetector 72
When the reflected light Rx ′, Ry ′, and Rz ′ are detected in the above, the first photodetector 71 does not detect the reflected light Rx, Ry, and Rz.

The detector 9 in this embodiment is
When the output Se 'is detected, the switch elements 8a to 8f
Is switched to the second photodetector 72 side, and when the output Se ′ is not detected, the switch elements 8 a to 8 f are switched to the first photodetector 7.
It is configured to switch to the first side.

With this configuration, it is not necessary to provide an output terminal for each of the plurality of photodetectors or each of the plurality of detectors, so that the scale of the apparatus can be reduced, and the apparatus can be reduced in size and weight. Can contribute to.
Also, by reducing the number of the output terminals, the wiring from the light receiving element to the external amplifier can be simplified, so that the working time required for processing the device can be shortened.

In particular, in the case of the optical pickup device having the above-described structure, the switch element 8a of the detector 9 can be selected simply by selecting which of the first light source 11 and the second light source 12 is turned on.
８8f will be switched. Therefore, the first
Since no separate control signal is required to connect either the photodetector 71 or the second photodetector 72 to the output terminals A to F, the device can be configured more simply.

In the case where the optical disk 6 set in the optical pickup device is a medium on which reading and writing are performed by a light beam emitted from the first light source 11, even if the first optical disk 6 is used as a medium,
Even if both the light source 11 and the second light source 12 are turned on, the reflected light from the optical disk 6 hardly returns to the second photodetector 72. Conversely, when the optical disk 6 is a medium on which reading and writing are performed by the light beam emitted from the second light source 12, the first optical detector 71 includes the optical disk 6
The reflected light from is hardly returned.

Therefore, even if the first light source 11 and the second light source 12 are both turned on during the operation of the optical pickup device, the switch element 8a by the detector 9 described above is used.
It is possible to realize the switching control of .about.8f. However, in order to more reliably prevent interference of signals transmitted to the output terminals A to F and mixing of noise, the second light source 12 is turned off when the first light source 11 is turned on, as described above. When the second light source 12 is turned on, the first light source 1
It is desirable to have a configuration in which 1 is turned off.

The information signal RF, the focus error signal FES, and the tracking error signal TES derived based on each signal sent from the output terminals A to F to the external amplifier are as follows (2) to (4). ) Expression.

(Equation 2)

Here, a to f in the above equation are output terminals A to A from the first photodetector 71 or the second photodetector 72, respectively.
The output signal sent to F is shown. That is, if the switch elements 8a to 8f are switched to the first photodetector 71 side, a to f in the above equations are the outputs Sa to Sf, respectively.
Will be shown. On the other hand, if the switch elements 8a to 8f are switched to the second photodetector 72 side, a
To f indicate outputs Sa 'to Sf', respectively.

As described above, in the optical pickup device of the present embodiment, the first photodetector 71 and the second photodetector 72
Are connected to the output terminals A to F to process the signal output from the light receiving element 7 to derive the information signal RF, the focus error signal FES, and the tracking error signal TES. The same circuit can be used. Therefore, unlike the conventional case, it is not necessary to provide a plurality of signal processing circuits on the output side of the light receiving element 7, so that the reliability of the device can be improved and the cost can be reduced.

As a simpler configuration example than the above-described embodiment, the first configuration without the switch elements 8a to 8f can be used.
The photodetector 71 and the second photodetector 72 can be simply connected in parallel to the output terminals A to F. According to this configuration, it is possible to further reduce the size and weight of the device as compared with the above configuration. However, in view of the interference of signals transmitted to the output terminals A to F and the mixing of noise, the configuration of the above embodiment can be reduced. It is desirable to adopt it.

Further, in the above embodiment, the optical pickup device provided with two light sources and two light detectors has been described as an example. However, the present invention is not limited to this. The present invention is applicable to an optical pickup device having a detector. In that case, it is not always necessary to share the output terminal among all the photodetectors. If at least one set of photodetectors shares the output terminal, the object of reducing the number of output terminals can be achieved. .

When each photodetector is constituted by a plurality of detectors, it is not always necessary to share the output terminal among all the detectors, and at least one set of detectors shares the output terminal among the photodetectors. With the configuration, the object of reducing the number of output terminals can be achieved.

In the above-described embodiment, the optical pickup apparatus adopting the three-beam method as the tracking error detection method has been described as an example. However, the type of the tracking error detection method is not the essence of the present invention. The invention can be applied to an optical pickup device employing any tracking error detection method such as a push-pull method.

[0053]

In the optical pickup device according to the present invention, a plurality of light sources which are close to each other, a converging optical system for converging a light beam emitted from each light source on an information recording medium, An optical pickup device having a plurality of photodetectors for receiving reflected light and recording, reproducing, or erasing information on a plurality of information recording media having different standards; , At least one set shares the output terminal. When each of the photodetectors includes a plurality of detectors, at least one set of the detectors may share an output terminal between the photodetectors.

With such a configuration, it is not necessary to provide an output terminal for each of the plurality of photodetectors or each of the plurality of detectors. Therefore, the scale of the apparatus can be reduced, and the size and weight of the apparatus can be reduced. Can contribute to.
Also, by reducing the number of the output terminals, the wiring from the light receiving element to the external amplifier can be simplified, so that the working time required for processing the device can be shortened.

Further, when any one of the plurality of light sources is turned on, the remaining light sources may be turned off. With such a configuration,
Since it is possible to prevent a mixed signal from being input to the output terminal shared by a plurality of photodetectors or to prevent noise from being mixed, it is possible to more accurately detect an information signal and an error signal. .

Further, among the photodetectors sharing the output terminal, it is preferable to have a connection switching means for connecting only the photodetector that has received the reflected light from the information recording medium to the output terminal. . With such a configuration, a separate control signal is not required to select the photodetector, so that the device can be configured more simply.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration example of a first photodetector 71 and a second photodetector 72 provided in an optical pickup device according to the present invention.

FIG. 2 is a schematic view showing one configuration example of a conventional optical pickup device.

FIG. 3 is a schematic diagram illustrating a configuration example of a first photodetector 71 and a second photodetector 72 provided in a conventional optical pickup device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser 11 1st light source 12 2nd light source 2 Diffraction grating 3 Half mirror 4 Collimating lens 5 Objective lens 6 Optical disk 7 Light receiving element 71 1st photodetector 71a-f detector 72 2nd photodetector 72a-f Detector 8a- f switch element 9 detector

Claims (4)

[Claims] 1. A plurality of light sources close to each other, a converging optical system for converging a light beam emitted from each light source on an information recording medium, and a plurality of photodetectors for receiving reflected light from the information recording medium. In an optical pickup device for recording, reproducing, or erasing information on a plurality of information recording media having different standards, at least one of the plurality of photodetectors shares an output terminal. An optical pickup device, characterized in that: 2. An optical pickup according to claim 1, wherein each of said photodetectors comprises a plurality of detectors, and at least one set of detectors shares an output terminal between each of said photodetectors. apparatus. 3. The optical pickup device according to claim 1, wherein when any one of the plurality of light sources is turned on, the other light sources are turned off. . 4. The photodetector sharing an output terminal,
4. The optical pickup device according to claim 1, further comprising connection switching means for connecting only a photodetector that has received reflected light from the information recording medium to the output terminal. .