JP2000357342A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable handiness and low cost by providing an optical pickup device with an optical path separating element for plurally dividing a laser beam and with a two-dimensional array photodetector in which a photodetecting part is plurally arrayed in matrix as a means for detecting an objective lens position for an optical information recording medium. SOLUTION: A diffused beam emitted from a semiconductor laser 1 being a light source, is divided into plural optical paths with a diffraction grating 54 which is an optical path separating element made to be a parallel beam with a collimator lens 2, passing through a beam splitter 55, a 1/4 wavelength plate, and forming a beam spot on the recording face of an optical disk 8 which is an optical information recording medium converged with an objective lens 7. The converged beam is reflected on the optical disk face, returned on the same optical path, reflected on the joined face of the beam splitter, and refracted at 90 deg.. Then, the beam passes through a detecting lens 12 and a cylindrical lens 13 for an astigmatic method, entering a two-dimensional array photodetector 3. Thus, the optimum structure is provided for the optical pickup device to which the pattern structure of a light receiving part is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a versatile optical pickup device capable of interchangeably writing and reading information signals on and from a plurality of types of disk-shaped optical recording media. This is advantageous for application to optical information recording / reproducing devices such as CD-R writers and DVD players.

[0002]

2. Description of the Related Art In a conventional optical pickup device,
An optical path separating element such as a diffraction grating or hologram on the optical path and a beam reflected by the optical information recording medium surface to detect a tracking error, focus error, or tilt error of a condensed beam on an optical information recording medium such as an optical disk Many are configured with light receiving elements having a plurality of light detecting units for receiving light. As a device for detecting a tracking error, there is, for example, a device described in Japanese Patent Application Laid-Open No. 57-205833 of a so-called three-beam system. FIG. 1 shows a conventional optical pickup device using a three-beam method and a push-pull method. In FIG. 1, a laser beam emitted from a light source 1 such as a semiconductor laser is collimated by a collimator lens 2 and is incident on a diffraction grating 54 which is an optical path separating element. And two sub-beams. After passing through the beam splitter 55, these beams are condensed by the objective lens 7 on the optical disk 8 as an optical information recording medium as shown in FIG. The reflected light from the optical disk 8 travels backward through the incident optical path, passes through the objective lens in the reverse direction, is reflected by the beam splitter 55, passes through the detection lens 12 and the cylindrical lens 13, and is received by the photodetector 56. You.

FIG. 3 shows a light receiving portion pattern of the photodetector 56 of FIG. 1 and an arrangement of spots on the light receiving portion. Photodetector 56
Are light-receiving units 61 to 64 divided into four parts and independent light-receiving units 6
5 and 66. The main beam 58 reflected by the optical disk 8 forms a spot 67 substantially at the center of the four divided light receiving units 61 to 64, and obtains a focus error signal by the astigmatism method. In addition, 2 reflected on the optical disc 8
The two sub-beams are independent light-receiving units 65 and 6 respectively.
The spots 68 and 69 are separately formed on 6 and a track error signal is obtained from the calculation of {V (65) -V (66)} by the three-beam method. It should be noted that the above arithmetic expression is based on the light receiving unit 65,
This means a difference between outputs according to the amount of light received by the light receiving unit 66. In such an optical pickup device, the pattern of the light receiving portion of the photodetector for detecting the beam reflected from the optical information recording medium uses a pattern specific to the optical pickup device. For example, in the case of the three-beam method and the astigmatism method as shown in FIG.
The light receiving portion pattern of the photodetector 55 includes light receiving portions 61 to 64 for receiving the main beam spot 67.
And a pattern divided into six parts like the sub-beam spots 68 and 69, each having a different position and area. Further, for example, Japanese Patent Application Laid-Open No. 7-192
As disclosed in Japanese Patent Publication No. 306, there is also known an example in which a beam is separated into seven beams by a diffraction grating and a photodetector having 11 light receiving unit patterns is used.

On the other hand, compact discs (CDs) and DVs
Many optical information recording media having different transparent substrate thicknesses, such as D, can be recorded or reproduced by one optical pickup device. This type is equipped with multiple objective lenses corresponding to the substrate thickness in order to focus the beam to the vicinity of the diffraction limit on the optical information recording medium even if the substrate thickness is different, and restricts the aperture of the objective lens Various methods are known, such as those having a function of performing the above-mentioned operations and those having a diffraction grating. However, when the three-beam method is used in an optical pickup device having a compatible recording / reproducing means such as a CD and a DVD, the track pitch is different between the CD and the DVD. Therefore, a sub-beam suitable for each track pitch is generated by the optical path separating element. As the number of sub-beams increases, the number of light-receiving patterns of the photodetector must also increase. In addition, when the target optical information recording medium is changed and the apparatus is adapted to the medium, the separation pattern in the optical path separation element must be changed, and the light receiving unit pattern of the photodetector is also changed accordingly. This necessitates high costs and a long development period. Also D
As shown in the example, for example, the track pitch of DVD-R is 0.8 μm while the track pitch of VD is 0.74 μm.
Whenever the format of the optical information recording medium is newly standardized, it is necessary to generate a sub-beam suitable for each format and increase the number of light receiving unit patterns of the photodetector. Further, depending on the format standard, it may be difficult to generate an appropriate sub-beam and increase the number of light receiving unit patterns of the photodetector.

In the conventional optical pickup device, the astigmatism method {V (61 + V (64)}) shown in FIG.
The focus error signal obtained by − {V (62) + V (63)} is ± 0 in the case of FIG. 3, while the position of the photodetector is the reflected beam from the optical information recording medium as shown in FIG. In the case of deviation from light, {V (61 + V (64)}}
> {V (62) + V (63)}, and there is a problem that an offset corresponding to the amount of deviation is generated and accurate focus correction cannot be performed. Further, there may be a case where correction of a focus error, a tracking error, a tilt error, or the like cannot be performed due to a variation in separation performance of the optical path separating element or an insufficient position adjustment of the optical path separating element and the photodetector. The beam and photodetector assembly position must be adjusted with very high accuracy,
Increased costs due to increased man-hours for adjustment were inevitable.

[0006]

SUMMARY OF THE INVENTION The present invention provides a versatile configuration by arranging two-dimensionally a plurality of light receiving portion patterns of a photodetector for detecting a reflected beam from an optical information recording medium, When adapting an optical pickup to different types of optical information recording media, it is possible to respond simply by changing the processing method of the signals generated by the individual light receiving elements arranged without replacing the photodetector itself. It is an object of the present invention to provide a low-cost, versatile optical pickup device.

[0007]

Means taken to solve the problem are means for recording or reproducing information by irradiating a laser beam condensed by an objective lens onto an optical information recording medium; An optical pickup device having means for detecting the position of the objective lens with respect to the optical information recording medium by reflected light from the recording medium; As a means for detecting the position of the objective lens, a two-dimensional array photodetector in which a plurality of photodetectors are arranged in a matrix is provided. This is to enable error detection and to easily perform error correction.

[0008]

[Embodiment 1] Embodiment 1 is an optical pickup device according to the above solution, wherein the optical pickup device comprises a plurality of optical path separating elements.
That is, necessary optical path separating elements can be selected and used. A second embodiment is that the optical pickup device according to the above-described solution includes a plurality of optical path separating elements and a plurality of objective lenses, and each of them can be selected and used in an arbitrary combination. In a third embodiment, an optical pickup device according to the above-described solution includes a plurality of optical path separating elements and a plurality of light sources having different wavelengths, and is close to a diffraction limit even when the transparent substrate thickness of the optical information recording medium or the light source wavelength is different. That is, an optical system for condensing light is provided, and an optical path separating element can be arbitrarily selected. Further, in a fourth embodiment, the optical pickup device according to the first, second, or third embodiment detects a type of an optical information recording medium to be recorded or reproduced, and separates an optical path suitable for the optical information recording medium. That is, an element can be automatically selected and used. The fifth embodiment is directed to the optical pickup device according to the first, second, third, and fourth embodiments, in which the light receiving operation range on the two-dimensional array photodetector and the initial value of the incident laser light are different. The shift amount in the set state is detected by a two-dimensional array photodetector, and the light receiving calculation range is reset according to the shift amount.

[0009]

The two-dimensional array photodetector in which a plurality of photodetectors are arranged in a matrix as a means for detecting the position of the objective lens with respect to the optical information recording medium is employed. , It is possible to detect a tracking error, a focus error, and the like. Even when the optical path separating element, objective lens, and light source are selected in any combination, signal detection is performed in all situations by simply selecting the light receiving calculation range of the light detection unit without changing the photodetector itself. Can be performed. Also, even when the beam spot deviates from the light receiving calculation range on the light detection unit due to a position shift of the optical path separation element or the photodetector, the shift amount of the shift is detected and the light receiving calculation range is electrically moved. Thus, signal detection that is not different from normal can be performed. Further, even when the beam spot is displaced from the light receiving calculation range on the photodetector due to a position shift of the optical path separating element or the photodetector, the shift amount of the shift is detected and the light receiving calculation range is electrically moved. As a result, signal detection that is not different from normal can be performed.

[0010]

Next, an embodiment will be described with reference to the drawings. [First Embodiment] The first embodiment is an embodiment of an optical pickup device (the invention according to claim 1) according to the above-mentioned solving means, and its configuration is shown in FIG. This is shown in FIG.
This is an optical pickup device using a two-dimensional array detector instead of the conventional photodetector shown in FIG. A divergent beam emitted from a semiconductor laser 1 as a light source is collimated by a collimator lens 2 and divided into a plurality of optical paths by a diffraction grating 54 as an optical path separating element. A beam splitter 55 and a 波長 wavelength plate (not shown) ), And are condensed by the objective lens 7 to form a beam spot on the recording surface of the optical disc 8 as an optical information recording medium. The condensed beam is reflected on the optical disk surface, returns on the same optical path, and is reflected on the joint surface of the beam splitter.
It is bent at 0 °. Thereafter, the light passes through the detection lens 12 and the cylindrical lens 13 for the astigmatism method (not necessary when the astigmatism method is not used), and enters the two-dimensional array photodetector 3.

FIG. 6 shows an example of a two-dimensional array photodetector. The light receiving unit pattern is a two-dimensionally arranged mesh, and each cell corresponds to one light receiving unit. In the example of FIG.
And × 1250 light receiving units in a total length of 50 are provided. This 2
Components such as the shape, area, number of arrays, and light receiving portion patterns of the dimensional array photodetector do not necessarily have to be those shown in FIG. 6, but may be configured to be optimal for the applied optical pickup device. When the tracking error and the focus error are detected by the three-beam method and the astigmatism method,
Each component in FIG. 5 is arranged so that three beams are incident on the two-dimensional array photodetector as shown in FIG. And 2
The light receiving operation range of the three-dimensional array photodetector 3 is set to the light receiving unit 61 in FIG.
As in the arrangement of ~ 66, if the light receiving calculation range 71 in Fig. 7 is set, exactly the same signal detection can be performed.

Also, as shown in FIG. 8, the beam spot 70 largely deviates from the initially set light receiving calculation range 71 due to variations in the diffraction function of the diffraction grating, insufficient adjustment of the positions of the diffraction grating, the photodetector, and the like. In this case, if the shift amount of the beam spot is detected by the two-dimensional array photodetector and the light receiving calculation range is electrically shifted as shown in FIG. 9 according to the shift amount, the same as in the case of FIG. It is possible to perform signal detection. In addition, when the number of separations in an optical path separation element by a diffraction grating or the like is increased to four or more, focus error detection not based on the astigmatism method or tilt error detection with respect to the incident optical axis of a disk is performed, and two-dimensional array light detection is performed. The light receiving calculation range may be appropriately set within the entire light receiving range of the device.

Another embodiment of the optical pickup device provided with a two-dimensional array detector according to the solving means is shown in FIGS. 10 and 11 show an example in which the collimator lens is omitted. In FIG. 11, the diffraction grating 54 is installed behind the beam splitter 55. 12 and 13 show examples in which a light source and a two-dimensional array photodetector are integrated into one.
3, the beam splitter is omitted. Figures 12 and 1
The integrated element 4 in 3 has, for example, a shape as shown in FIG. In FIG. 14, reference numeral 31 denotes a semiconductor laser as a light source, 32 denotes a reflection mirror, and 33 denotes an output beam.

[Second Embodiment] The second embodiment is an example of an optical pickup device (invention according to claim 2) according to the first embodiment and having a plurality of optical path separating elements, and the configuration thereof is shown in FIG. Is shown in In the example having a plurality of optical path separating elements shown in FIG. 15, the basic optical path of the optical system is the same as that of the first embodiment, but the optical path separating unit can be arbitrarily selected. I have. Multiple optical path separation elements 5
Examples of No. 7 are shown in FIGS. A plurality of optical path separating elements 57
Are translated or rotated to obtain the beam incident area 59.
The required optical path separation function can be selected by arranging the selected optical path separation unit 58.

[Third Embodiment] The third embodiment is an example of the optical pickup device according to the second embodiment (the invention according to claim 3). Although not shown, a plurality of optical path separating elements and a plurality of objective lenses can be simultaneously provided. A plurality of objective lenses are examples of a plurality of optical path separation elements.
As in the case of 6 to 18, a configuration in which a required objective lens can be arbitrarily selected by parallel movement or rotational movement can be adopted. According to this, the plurality of optical path separation elements and the plurality of objective lenses can be translated or rotated to select the required optical path separation function and the objective lens in any combination.

[Fourth Embodiment] The fourth embodiment is an example of an optical pickup device according to the third embodiment (the invention according to claim 4), and the configuration thereof is shown in FIG. In addition to the configuration of the example shown in FIG. 15, another light source 5 having a different wavelength, a dichroic prism 53 for synthesizing beams from the collimator lens 2 and the two light sources, and a transparent optical information recording medium are provided. Even if the substrate thickness or the light source wavelength is different, a plurality of optical systems or objective lenses 11 for condensing light to near the diffraction limit are provided. According to this, a light source having a necessary wavelength, an optical path separating element, an optical system or an objective lens can be arbitrarily selected. The example shown in FIG. 20 is another example in which a two-dimensional array photodetector is newly provided in addition to the configuration in FIG. 19, and the example shown in FIG. 21 is further provided with a plurality of light separating elements. This is an example.

[Fifth Embodiment] The fifth embodiment is an example of an optical pickup device according to the fourth embodiment (the invention according to claim 5), and its flowchart is shown in FIG.
The flow shown in FIG. 22 corresponds to the optical information recording medium used.
Optimal conditions are automatically set, and a means for separately detecting the type of the optical information recording medium used in the optical pickup device is provided, so that the optimum optical path separation for the detected type of the optical information recording medium is provided. It is possible to automatically select an element, an objective lens, or a light source, and perform information recording / reproduction under conditions optimal for the optical information recording medium to be used.

As an example of the means for detecting the type of the optical information recording medium to be used, the difference in the spherical aberration caused by the difference in the thickness of the transparent substrate of the optical information recording medium is used to calculate the light reception of the two-dimensional array photodetector. A method for specifying an optical information recording medium by appropriately setting a range and detecting a substrate thickness, a method for detecting an optical information recording medium by detecting a substrate thickness by a separately provided substrate thickness detecting element, an optical information recording medium A method of optically reading information for specifying the type of the optical information recording medium recorded in advance in a part of the optical information recording medium with a two-dimensional array photodetector or a separately provided detector and specifying the type of the optical information recording medium. can give.

[0019]

The effects of the present invention are apparent from the above description, but the effects of the present invention are summarized as follows for each claimed invention. According to the first aspect of the present invention, the provision of the two-dimensional array photodetector enables optical information recording even when the number and arrangement of the separation beams by the optical path separation element are changed. Since there is no need to change the photodetector for detecting the reflected light from the medium, the development period can be shortened and the development cost can be reduced. Further, the shape, area, and arrangement of the light receiving calculation range can be freely changed within the light receiving range of the two-dimensional array photodetector, which is excellent in versatility. Further, since one beam is detected by a plurality of light receiving units, not only the intensity of the beam but also the shape of the beam can be detected. Further, even when the beam position is shifted due to a variation in the separation performance of the optical path separating element and insufficient position adjustment of the optical path separating element and the photodetector, the shift amount is detected by the two-dimensional array photodetector and the light receiving calculation range is determined. It is possible to shift, and it is possible to greatly reduce the adjustment time and cost in the manufacturing process.

According to the second aspect of the present invention, since a plurality of optical path separating elements are provided in the optical pickup device, the plurality of optical path separating elements are provided according to the type or use of the optical information recording medium to be used. An appropriate optical path separation element can be selected and used, and information recording / reproducing of various types of optical information recording media can be easily performed by a single optical pickup device.

According to the third aspect of the present invention, since a plurality of objective lenses are provided in the optical pickup device, the present invention is applicable to optical information recording media having different transparent substrate thicknesses. And information recording / reproducing of more kinds of optical information recording media becomes possible.

According to the fourth aspect of the present invention, since a plurality of light sources having different wavelengths are provided in the optical pickup device, the present invention is applicable to an optical information recording medium having wavelength dependence. This makes it possible to record / reproduce information on more types of optical information recording media.

[Effect of the invention according to claim 5] According to the structure of claim 5, since means for detecting the type of optical information recording medium to be used is provided, it is possible to cope with many types of optical information recording media. In addition, it is possible to perform recording and reproduction optimal for the optical information recording medium very easily. [Advantage of the invention according to claim 6] According to the configuration of claim 6, even if the beam position is shifted due to the dispersion of the separation performance of the optical path separating element, the insufficient adjustment of the position of the optical path separating element and the photodetector, etc. Since the shift amount can be detected by the two-dimensional array photodetector and the light receiving calculation range can be shifted, the adjustment time and cost of the manufacturing process can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of a conventional optical pickup device.

FIG. 2 is a schematic diagram showing a state of a conventional spot.

FIG. 3 is a diagram showing a conventional arrangement relationship between a light receiving unit pattern and a spot.

FIG. 4 is a diagram showing an arrangement relationship when the position of a conventional photodetector is shifted.

FIG. 5 is a plan view of an optical pickup device according to one embodiment of the present invention.

FIG. 6 is a diagram illustrating a light detection unit of the two-dimensional array light detector.

FIG. 7 is a diagram showing an arrangement relationship between a light receiving calculation range of a two-dimensional array photodetector and spots.

FIG. 8 is a diagram showing an arrangement relationship when a spot is shifted.

FIG. 9 is a diagram showing a state after the light receiving calculation range is appropriately shifted.

FIG. 10 is a plan view of an optical pickup device in which a collimator lens is omitted.

FIG. 11 is a plan view of another example of the optical pickup device in which the collimator lens is omitted.

FIG. 12 is a plan view of an optical pickup device in which a light source and a two-dimensional array photodetector are integrated.

FIG. 13 is a plan view of another example of the optical pickup device in which the light source and the two-dimensional array photodetector are integrated.

FIG. 14 is a diagram showing an element in which a light source and a two-dimensional array photodetector are integrated into one.

FIG. 15 is a plan view of an optical pickup device including a plurality of optical path separation elements.

FIG. 16 is a schematic diagram showing a plurality of optical path separation elements.

FIG. 17 is a schematic view showing another example of a plurality of optical path separation elements.

FIG. 18 is a schematic diagram showing still another example of a plurality of optical path separation elements.

FIG. 19 is a plan view of an optical pickup device in which light sources having different wavelengths are newly provided.

FIG. 20 is a plan view of another example of the optical pickup device in which light sources having different wavelengths are newly provided.

FIG. 21 is a plan view of still another example of the optical pickup device in which light sources having different wavelengths are newly provided.

FIG. 22 is a flowchart showing a procedure for automatically setting optimum conditions. Description of reference numerals in FIGS. 1 to 22 1, 5, 31: light source (semiconductor laser) 2: collimator lens 3: two-dimensional array photodetector 4: light source and two-dimensional array photodetector integrated element 7: objective lens 8: Optical disc 11: Plurality of objective lenses (plurality of optical systems) 12: Detection lens 13: Cylindrical lens 32: Reflection mirror 33: Outgoing beam 53: Dichroic prism 54: Diffraction grating (optical path separation element) 55: Beam splitter 56: Light Detector 67: Plural optical path separating elements 58: Optical path separating section 59: Beam incident area 61 to 66: Light receiving section 67: Spot (main beam spot) 68: Spot (+ 1st-order sub-beam spot) 69: Spot (-1st-order sub-beam) Spot) 70: Beam spot 71: Light receiving calculation range

Claims (6)

[Claims] A means for irradiating a laser beam condensed by an objective lens onto the optical information recording medium to record or reproduce information; and a means for reflecting the light from the optical information recording medium to the objective information lens with respect to the optical information recording medium. An optical path separating device for splitting a laser beam into a plurality of light beams, and a plurality of photodetection units arranged in a matrix as means for detecting the position of the objective lens with respect to an optical information recording medium. An optical pickup device comprising a two-dimensionally arranged photodetector. 2. The apparatus according to claim 1, further comprising a plurality of optical path separating elements, wherein said optical path separating elements can be selectively used.
Optical pickup device. 3. The optical pickup device according to claim 1, further comprising a plurality of optical path separating elements and a plurality of objective lenses, wherein said optical path separating element and the objective lens can be selected and used. 4. An optical system comprising a plurality of optical path separating elements, a plurality of objective lenses, and a plurality of light sources having different wavelengths, and condensing light to the vicinity of a diffraction limit even when a transparent substrate thickness of an optical information recording medium or a light source wavelength is different. 2. The optical pickup device according to claim 1, wherein said optical path separating element, a plurality of objective lenses, or a light source can be selectively used.
Optical pickup device. 5. An optical path separating element suitable for the optical information recording medium, wherein the type of the optical information recording medium to be recorded or reproduced is detected.
5. The optical pickup device according to claim 2, wherein an objective lens or a light source is automatically selected and used. 6. A two-dimensional array photodetector detects a shift amount of the incident light on the light receiving calculation range on the two-dimensional array photodetector in an initial setting state, and according to the shift amount. 6. The optical pickup device according to claim 2, wherein the light receiving calculation range is reset.