JP4742159B2 - Optical information reproduction method - Google Patents

Description

  The present invention relates to an optical pickup head device, an optical information device, and an optical information reproducing method for recording / reproducing or erasing information on / from an optical disc.

  As a high-density and large-capacity storage medium, an optical disk that records information as a pit-like pattern is known. There are optical discs for various purposes depending on the content of information. For example, a digital audio disk, a video disk, a document file disk, and a data file disk. These applications continue to expand into yet another new field. Among various optical disks, a digital versatile disk (DVD) that has begun to spread in recent years is a high-density optical disk that uses a visible light semiconductor laser having a wavelength of 650 nm as a light source. There are various standards for DVD such as a read-only DVD-ROM, a DVD-R that can be recorded only once, and a DVD-RAM that can be recorded many times. In addition, a compact disk (CD) using an infrared semiconductor laser having a wavelength of 780 nm as a light source has been widely used. Similar to DVD, there are various standards such as a read-only CD-ROM, a CD-R that can be recorded only once, and a CD-RW that can be recorded many times.

  Since both DVD and CD are widely used, for the convenience of users, in addition to DVD-ROM and CD-ROM, DVD-R and CD-R are played back by a single information playback device. Preferably it can be done.

  Both CD-R and DVD-R are devices for recording and reproducing information using changes in the reflectance of the dye. However, since the absorptance and reflectance are optimized in a narrow wavelength range around 780 nm and 650 nm, respectively, information recorded on a CD-R cannot be reproduced using a beam with a wavelength of 650 nm, or recorded on a DVD-R. In many cases, the recorded information cannot be reproduced using a beam having a wavelength of 780 nm. Therefore, in an information reproducing apparatus capable of reproducing both CD-R and DVD-R, an optical pickup head including a DVD-R semiconductor laser and a CD-R semiconductor laser is used.

  In order to downsize the information reproducing apparatus and reduce the manufacturing cost, it is effective to adopt a small and low cost optical pickup head. As one of the techniques, a technique for simplifying the optical system of the optical pickup head has been proposed in recent years by integrating the above-described two types of semiconductor lasers in one package.

  FIG. 16 shows a configuration of a conventional optical pickup head device 1600 disclosed in Japanese Patent Laid-Open No. 10-289468. The optical pickup head device 1600 includes a light source 110 that emits a linearly polarized divergent beam having a wavelength of 650 nm and a light source 120 that emits a linearly polarized divergent beam having a wavelength of 780 nm on a substrate 610 in the package 60.

  Hereinafter, the principle of reading information recorded on the recording medium 20 using the optical pickup head device 1600 will be described. First, the beam 100 emitted from the light source 110 or 120 is incident on the beam combining means 30 which is a polarizing prism (birefringent plate) or hologram. The beam combining means 30 sets the same optical axis whether the beam 100 is a beam from the light source 110 or a beam from the light source 120. In the case of a beam from the light source 120, the beam 100 is refracted or diffracted by the beam combining means 30 and deflected. Thereafter, the beam 100 is converted into parallel light by the collimating lens 131, circularly polarized by the quarter-wave plate 140, converted to a convergent beam by the objective lens 132 through the aperture 15. The beam 100 is irradiated onto the optical storage medium 20, passes through the transparent substrate 21, and is condensed on the information recording surface 22. The beam 100 reflected by the information recording surface 22 is transmitted through the quarter-wave plate 140 to be a polarized beam that is 90 degrees different from the forward path, passes through the beam combining means 30, and then deflected means (polarizing hologram) 40. And is guided to the light detection means 50. The signal detected by the light detection means 50 is used as a signal representing information, and is used to generate a focus error signal and a tracking error signal given to the actuator 16 for focusing and tracking.

  In a disc recording / reproducing apparatus such as a DVD-RAM that can be recorded many times, the tracking control signal becomes unstable because the groove of the disc is shallow. Therefore, it is necessary to further generate three types of diffracted light using a diffraction grating (not shown) to obtain a focus error signal and a tracking error signal.

Japanese Patent Laid-Open No. 10-289468

  The optical pickup head device 1600 includes a beam combining unit 30 formed of a polarizing prism or a hologram, and a quarter-wave plate 140 necessary for polarizing the beam. Is expensive.

  Further, if the transparent substrate 21 of the optical storage medium 20 has birefringence, the beam reflected by the optical storage medium 20 is deflected by the combining means 30 and does not return to the light detection means 50 and is recorded on the optical storage medium 20. Information cannot be read well.

  Further, since the two light sources 110 and 120 are integrated on one substrate 610, there is no room for adjusting the diffraction gratings by providing diffraction gratings that generate three types of diffracted light. Or an optical pick-up head apparatus will enlarge.

  An object of the present invention is to provide a diffraction grating, an optical pickup head device, an optical information device, and an optical information reproducing method using the same.

In order to achieve the above object, the present invention is configured as follows.
The light source package of the present invention includes a first light source that emits a first beam, a second light source that emits a second beam different from the first beam, and the incident first beam or the A light source package including a polarization unit configured to deflect the second beam and emit the third beam as a third beam, wherein the polarization unit includes a first deflection unit configured to deflect the incident first beam, and an incident Second deflecting means for deflecting the second beam, the optical axis of the first beam after being deflected by the first deflecting means, and the optical axis after being deflected by the second deflecting means The optical axis of the second beam is substantially the same, thereby achieving the above object.

  The polarizing unit may further include a third deflecting unit that further deflects the first beam deflected by the first deflecting unit or the second beam deflected by the second deflecting unit. Good.

  The first to third deflection means may be formed on two substantially transparent substrates.

  In addition, the light source package, a condensing unit for condensing the third beam emitted from the light source package on the optical storage medium, and a beam branch for receiving and deflecting the reflected beam reflected by the optical storage medium An optical pickup head device may be configured to include a light receiving unit that receives the reflected beam deflected by the beam branching unit and outputs a signal corresponding to the amount of received light.

  The optical pickup head device according to the present invention includes a first light source that emits a first beam having a wavelength λ1, a second light source that emits a second beam having a wavelength λ2 different from the wavelength λ1, and the first light source. Receiving a beam emitted from the light source or the second light source, and generating a plurality of beams; a condensing unit for condensing the plurality of beams generated by the diffraction unit on an optical storage medium; A beam branching unit that receives and deflects a reflected beam that is collected on the optical storage medium and reflected by the optical storage medium, and a reflected beam that is deflected by the beam branching unit, and that corresponds to the amount of light received An optical pickup head device having a light detection unit for outputting a signal, wherein the diffraction unit has a first pattern and a second pattern formed at a predetermined angle, and the first pattern is For wavelength λ1 rather than wavelength λ2 The diffraction efficiency is high, and the second pattern is an optical pickup head device having a diffraction efficiency higher than the wavelength λ1 with respect to the wavelength λ2, thereby achieving the above object.

  The first pattern generates diffracted light substantially only for the first beam of wavelength λ1, and the second pattern substantially diffracts light only for the second beam of wavelength λ2. May be generated.

  The interval between the diffracted lights generated from the first pattern and the interval between the diffracted lights generated from the second pattern may be substantially the same.

  A line connecting a plurality of diffracted lights generated from the first pattern and a line connecting a plurality of diffracted lights generated from the second pattern are substantially the same on the photodetector. Also good.

  The optical pickup head device according to the present invention includes a first light source that emits a first beam, a second light source that emits a second beam having a wavelength different from that of the first beam, and the first light source. Or receiving and deflecting the beam emitted from the second light source, receiving a third beam having substantially the same optical axis, and receiving the third beam emitted from the deflection unit, A diffraction unit that generates a plurality of beams, a light collecting unit that collects the plurality of beams generated by the diffraction unit on an optical storage medium, and a light that is collected on the optical storage medium and reflected by the optical storage medium An optical pickup head device having a beam branching unit that receives and deflects the reflected beam and a light detection unit that receives the reflected beam deflected by the beam branching unit and outputs a signal corresponding to the received light amount This achieves the above objectives

  The optical pickup head device according to the present invention includes a first light source that emits a first beam having a wavelength λ1, a second light source that emits a second beam having a wavelength λ2 different from the wavelength λ1, and the first light source. A first beam emitted from the light source or a second beam emitted from the second light source is collected on the optical storage medium, and is collected on the optical storage medium. Light having a beam branching unit that receives and deflects the reflected beam reflected by the optical storage medium, and a light detection unit that receives the reflected beam deflected by the beam branching unit and outputs a signal corresponding to the received light quantity In the pickup head device, the beam branching unit is a hologram element in which a first hologram pattern and a second hologram pattern are formed, and the first hologram pattern is diffracted with respect to the wavelength λ1 rather than the wavelength λ2. The second hologram pattern is an optical pickup head device having a high diffraction efficiency with respect to the wavelength λ2 rather than the wavelength λ1, thereby achieving the above object.

  The beam branching unit is a hologram element in which a first hologram pattern and a second hologram pattern are formed, and the wavelength of the first beam is a wavelength λ1 and the wavelength of the second beam is a wavelength λ2. The first hologram pattern may have a higher diffraction efficiency for the wavelength λ1 than the wavelength λ2, and the second hologram pattern may have a higher diffraction efficiency for the wavelength λ2 than the wavelength λ1.

  The diffracted light generated from the first hologram pattern and the diffracted light generated from the second hologram pattern may substantially coincide on the light detection means.

  The first light source, the second light source, and the light detection unit may be integrated.

  The light detection unit may receive conjugate light from the hologram element.

  In addition, any one of the optical pickup head devices described above, a drive unit that changes the relative positions of the information storage medium and the optical pickup head device, and a signal that is output from the optical pickup head device are used to perform calculations. An information recording / reproducing apparatus including an electric signal processing unit for obtaining the information may be configured.

  According to the above configuration, it is possible to realize an optical information device that can reproduce information satisfactorily without any change in the amount of light received by the photodetector even if the optical storage medium has partially varying birefringence. Can do.

  Also, when assembling the optical pickup head device, if the rotation adjustment is made with respect to either the CD or the DVD optical storage medium, the other adjustment becomes unnecessary, and the productivity of the optical pickup head device is drastically increased. Can be improved.

  According to the present invention, the optical axis of the first wavelength beam and the optical axis of the second wavelength beam reflected by the second reflecting surface are made substantially the same using the non-polarizing prism. Thereby, a light source that emits a non-polarized beam as if it is emitted from one light source is obtained. When this light source is applied to an optical pickup head device, a quarter-wave plate is not required because of non-polarized light, and assembly adjustment of optical components when manufacturing the optical pickup head device is a conventional optical pickup head having one light source. As with the device, it is very simplified.

  In addition, even if the optical storage medium has birefringence that varies partially, there is no change in the amount of light received by the photodetector, and an optical information device that can reproduce information satisfactorily can be realized.

  Further, when the optical pickup head device is assembled, if the rotation adjustment of the diffraction grating is performed with respect to the optical storage medium of either CD or DVD, the other adjustment is performed at the same time. Productivity can be dramatically improved.

1 is a diagram illustrating a configuration of a semiconductor light source package of Embodiment 1. FIG. 2 is a diagram illustrating a configuration of a prism according to Embodiment 1. FIG. FIG. 6 is a diagram illustrating a configuration of an optical pickup head device according to a second embodiment. 6 is a diagram showing a configuration of a hologram element according to a second embodiment. FIG. 6 is a diagram illustrating a light receiving unit of the photodetector according to Embodiment 2. FIG. FIG. 6 is a diagram illustrating a configuration of an optical pickup head device according to a third embodiment. It is a figure which shows the light-receiving parts 14a-14d of the photodetector 14 with which the diffracted light 71a-c and 72a-c each corresponded in Embodiment 3. FIG. FIG. 10 is a diagram illustrating a configuration of an optical pickup head device according to a fourth embodiment. FIG. 10 is a diagram illustrating a configuration of an optical pickup head device according to a fifth embodiment. It is a figure which shows the relationship between the track | truck on the information recording surface of an optical storage medium, and beams 4a-4c and 5a-5c. FIG. 6 is a diagram showing a grating pattern of each grating surface 61 and 62 of the diffraction grating 6. FIG. 10 is a diagram illustrating a configuration of an optical pickup head device according to a sixth embodiment. It is a figure which shows the relationship on the track | truck on the information recording surface of an optical storage medium, and beams 4a-4c, 5a-5c. FIG. 10 is a diagram illustrating a configuration of an optical pickup head device according to a seventh embodiment. FIG. 10 shows an optical information device according to an eighth embodiment. The structure of the conventional optical pick-up head apparatus is shown.

  Embodiments 1 to 8 of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals are given to components having the same function.

(Embodiment 1)
In the present embodiment, the optical axis of the first wavelength beam reflected by the first reflecting surface is substantially the same as the optical axis of the second wavelength beam reflected by the second reflecting surface. A semiconductor light source package having such a prism will be described.

  FIG. 1 shows a configuration of a semiconductor light source package 10 according to the first embodiment. The semiconductor light source package 10 includes a semiconductor laser light source 1 having a wavelength λ1, a semiconductor laser light source 2 having a wavelength λ2, and a prism 3. The semiconductor laser light source 1 emits a linearly polarized divergent beam 4 having a wavelength λ1 capable of reproducing information when a DVD such as a DVD-R is used as an optical storage medium. In this specification, for example, λ1 = 650 nm. The semiconductor laser light source 2 emits a linearly polarized divergent beam 5 having a wavelength λ2 capable of reproducing information when a CD such as a CD-R is used as an optical storage medium. In the present specification, for example, λ2 = 780 nm. The semiconductor laser light source 1 and the semiconductor laser light source 2 are mounted in the same package 10. The prism 3 has three reflecting surfaces 31, 32 and 33. The reflection surface 31 is a dichroic mirror having wavelength selectivity, and transmits all the beams having the wavelength λ1 and reflects all the beams having the wavelength λ2. The reflection surface 32 is a total reflection mirror that reflects all the beam having the wavelength λ1. The reflection surface 33 is a total reflection mirror that reflects both the beams of wavelengths λ1 and λ2. In the prism 3, the optical axis of the beam having the wavelength λ 1 reflected by the reflecting surface 32 and the optical axis of the beam having the wavelength λ 2 reflected by the reflecting surface 31 are adjusted to be substantially the same. Therefore, the optical axes of the beams having the wavelengths λ1 and λ2 reflected by the reflecting surface 33 are also equal. The beam may be emitted from the prism 3 after being reflected by the reflecting surfaces 31 and 32 so as not to be reflected by the reflecting surface 33. In this case, the direction of the outgoing beam from the prism 3 is shifted 90 degrees clockwise from the outgoing direction shown in FIG. The direction of the outgoing beam from the prism 3 can be set to an arbitrary direction by adjusting the position of the semiconductor light source package 10. In the seventh embodiment, an optical pickup head device using such a prism will be described.

  FIG. 2 shows the configuration of the prism 3. The prism 3 is composed of two glass substrates 35 and 36. A total reflection surface 33 is formed on the lower surface of the glass substrate 36, a dichroic surface 31 is formed on the upper surface, and a total reflection surface 32 is formed on the upper surface of the glass substrate 35, respectively. The reflecting surfaces 32 and 33 are metal films, and the dichroic surface 31 is a dielectric multilayer film. The two glass substrates 35 and 36 on which the reflective surfaces 31 to 33 are vapor-deposited are bonded together via an adhesive layer 34. The two bonded glass plates are cut at the cutting surface 41. Thus, the prism 3 can be formed by cutting out two glass plates (parallel flat plates). Therefore, the prism 3 can be made very inexpensive as compared with a rectangular parallelepiped prism manufactured by conventional polishing, and the semiconductor light source package 10 can also be manufactured at a low cost.

  Further, by deflecting using the prism 3, even if the wavelength of the light source fluctuates, the beam hardly moves, so that the reliability of the light source increases.

  In the semiconductor light source package 10, since the beams 4 and 5 emitted from the prism 3 have the same optical axis, the beams are emitted as if emitted from one light source while having two light sources. Therefore, when the semiconductor light source package 10 is applied to an optical pickup head device, assembly adjustment of optical components when manufacturing the optical pickup head device is greatly simplified as in the conventional optical pickup head device having one light source. The

  The semiconductor light source package 10 is also suitable for multicolor laser pointers.

(Embodiment 2)
In the present embodiment, an optical pickup device that does not require the quarter-wave plate 140 (FIG. 16) will be described.

  FIG. 3 shows a configuration of the optical pickup head device 300 according to the present embodiment. The optical pickup head device 300 includes a semiconductor light source package 10, a hologram element 64, a collimator lens 8, an objective lens 9, and a photodetector 12. Since the semiconductor light source package 10 uses the non-polarizing prism 3, the beam 4 or 5 is not polarized. Therefore, it is not necessary to use a quarter wave plate that is mainly used for conversion between circularly polarized light (or elliptically polarized light) and linearly polarized light. In the first embodiment, no particular reference is made to the positional relationship between the semiconductor laser light source 1 and the semiconductor laser light source 2 in the semiconductor light source package 10, but in the present embodiment, the semiconductor laser light source 1 and the semiconductor laser light source 2 are used. The distance a between 2 is 2 mm. This is because the spherical aberration caused by the difference in the thickness of the substrate 21 of the optical storage medium 20 can be corrected by making the position of the light source 2 viewed from the collimating lens 8 closer to the light source 1. The refractive index of the prism is 1.51.

  Hereinafter, an operation in which the optical pickup head device 300 reads information from the optical storage medium 20 will be described. First, the optical pickup head device 300 causes either the semiconductor laser light source 1 or the semiconductor laser light source 2 to emit light according to the optical storage medium 20. When the optical storage medium 20 is a DVD, for example, the beam 4 is emitted from the semiconductor laser light source 1. The emitted beam 4 is reflected by the reflecting surface 32 formed on the prism 3, the optical path is bent, and the dichroic surface 31 is transmitted. On the other hand, when the optical storage medium 20 is a CD, the beam 5 is emitted from the semiconductor laser light source 2. The emitted beam 5 enters the prism 3 and is reflected by the dichroic surface 31. The beam 4 transmitted through the reflecting surface 31 and the reflected beam 5 have the same optical axis, are reflected by the reflecting surface 33 and bent in the optical path, and then converted into parallel light through the collimating lens 8 having a focal length of 20 mm. The beam 4 or 5 converted into parallel light is converted into a convergent beam by the objective lens 9 having a focal length of 3 mm, passes through the transparent substrate 21 of the optical storage medium 20, and is collected on the information recording surface 22. The thickness t of the transparent substrate is 1.2 mm for CD and 0.6 mm for DVD.

  The beams 4 and 5 are reflected by the information recording surface 22. The reflected beams 4 and 5 pass through the objective lens 9 and the collimator lens 8 and then enter the hologram element 64. The beams 4 and 5 incident on the hologram element 64 become diffracted lights 71 and 72, respectively, and are received by the photodetector 12.

  FIG. 4 shows the configuration of the hologram element 64. The hologram element 64 has three regions 64a to 64c, receives the beam 4 or 5 at the center of the hologram element 64, and generates diffracted light in the regions 64a to 64c. The axis 64d is parallel to the dividing line of the regions 64b and 64c, and is arranged so as to be parallel to the track when mapped to the track by the beam 4 or 5.

  FIG. 5 shows a light receiving portion of the photodetector 12. The light receiving unit of the photodetector 12 includes four light receiving units 12a to 12d. The light receiving units 12a to 12d receive the diffracted lights 71a to 71c and the diffracted lights 72a to 72c. Here, the diffracted lights 71a and 72a are generated in the area 64a of the hologram element 64 (FIG. 4), and the diffracted lights 71b and 72b are generated in the area 64b of the hologram element 64 (FIG. 4), and the diffracted lights 71c and 72c. Is generated in the region 64c of the hologram element 64 (FIG. 4).

  When the signals output from the light receiving units 12a to 12d according to the received light quantity are I12a to I12d, the focus error signal is obtained by the calculation of (I12a-I12b) by the Foucault method. The tracking error signal is obtained by comparing the phases of I12c and I12c by the phase difference method. Since any signal detection method is a well-known method, detailed description is omitted.

  The optical pickup head device of the present invention is capable of reproducing information favorably without changing the amount of light received by the photodetector even if the optical storage medium has birefringence that varies partially. It becomes.

  In the present embodiment, the reflecting surface 31 is a dichroic mirror in order to improve the transmission efficiency of the optical system. However, if there is a margin in the amount of light, the reflecting surface 31 may be a half mirror that does not have wavelength selectivity. In addition, a wavelength-selective aperture filter that restricts the aperture having a wavelength of 780 nm may be provided between the collimating lens 8 and the objective lens 9. Further, an objective lens having a different curvature obtained by partially changing the optimum substrate thickness may be used as the objective lens 9. Further, if the photodetector and the light source are integrated, the optical pickup head device 300 (FIG. 3) can be further miniaturized.

(Embodiment 3)
In the present embodiment, an optical pickup head device configured to use a predetermined hologram element so that diffracted light beams emitted from different light sources coincide on a photodetector will be described.

  FIG. 6 shows a configuration of an optical pickup head device 600 according to the present embodiment. The difference from the optical pickup head device 300 (FIG. 3) according to the second embodiment is that a hologram element 65 is used instead of the hologram element 64 (FIG. 3), and that the photodetector 14 is used instead of the photodetector 12. It is to use. Since the other configuration is the same as that of the optical pickup head device 300 (FIG. 3), description thereof is omitted.

  The hologram element 65 has pattern surfaces 66 and 67 on the lower surface and upper surface of a single substrate, respectively. Diffracted light 71 is generated from the pattern surface 66, and diffracted light 72 is generated from the pattern surface 67. FIG. 7 shows the light receiving portions 14a to 14d of the photodetector 14 in which the diffracted lights 71a to 71c and 72a to 72c match each other. The direction of the grating pitch and the spatial frequency axis of the hologram element 65 (FIG. 6) is selected so that the diffracted light 71 and 72 coincide on the photodetector 14. Otherwise, the pattern surfaces 66 and 67 (FIG. 6) are substantially the same as the regions 64a to 64c (FIG. 4), respectively.

  Referring to FIG. 6 again, the pattern formed on the pattern surface 66 generates a diffracted light upon receiving a beam with the wavelength λ1 of the light source 1, but hardly receives the diffracted light even when receiving a beam with the wavelength λ2 of the light source 2. Do not generate. In other words, the pattern formed on the pattern surface 66 has higher diffraction efficiency for the wavelength λ1 than for the wavelength λ2. This is realized by optically setting the grating depth to an integral multiple of λ2. Thereby, stray light can be suppressed and the light use efficiency can be increased. Similarly, the pattern formed on the pattern surface 67 generates a diffracted light upon receiving a beam with a wavelength λ2 of the light source 2, but hardly generates a diffracted light upon receiving a beam with a wavelength λ1 of the light source 1. In other words, the pattern formed on the pattern surface 67 has higher diffraction efficiency for the wavelength λ2 than for the wavelength λ1. In this case, the grating depth is optically set to an integral multiple of λ1.

  The size of the photodetector 14 is smaller than that of the photodetector 12 (FIG. 3). This is because the light receiving portions 14a to 14d can be reduced by overlapping the diffracted beams 71 and 72. Therefore, the optical pickup head device 600 is suitable for downsizing, and the smaller the size of the light receiving portion, the smaller the capacity and the more suitable the information reproducing device that requires higher speed.

  In the present embodiment, the configuration for detecting the focus error signal by the Foucault method has been described. However, other detection methods such as a spot size detection method can also be applied. Further, the photodetector 14 may receive conjugate light with respect to the diffracted lights 71 and 72 from the hologram element 65. In this case, the light utilization efficiency is doubled, and an optical pickup head device with a better signal-to-noise ratio can be configured.

  By using the two pattern surfaces 66 and 67, the photodetector 14 can be arranged in an arbitrary size and at an arbitrary position. Therefore, even when the outer shape of the optical pickup head device is restricted, the degree of freedom in optical design is large, and it is possible to flexibly deal with various uses such as in-vehicle use and portable use.

(Embodiment 4)
In the present embodiment, an optical pickup head device configured so that the diffracted light beams emitted from different light sources coincide on the photodetector by using a predetermined hologram element similar to that in the third embodiment. explain.

  8 differs from the optical pickup head device 600 (FIG. 3) shown in the third embodiment in that a hologram element 68 is used instead of the hologram element 65 (FIG. 6), and that the light source 1 (FIG. 3). ) Instead of the light source 1a and the semiconductor light source package 810 employing the light source 2a instead of the light source 2 (FIG. 3). Other configurations are the same as those of the optical pickup head device 600 (FIG. 6).

  The light source 1a and the light source 2a are monolithic semiconductor lasers formed on one semiconductor substrate and emit beams having wavelengths of 780 nm and 650 nm. The interval between the light emitting points is 100 μm. The hologram element 68 has two pattern surfaces 69 and 70 as in the hologram element 65 (FIG. 6). Diffracted light 71 is generated from the pattern surface 69, and diffracted light 72 is generated from the pattern surface 70. Again, the grating pitch and the direction of the spatial frequency axis are selected so that the diffracted lights 71 and 72 generated from the pattern surfaces 69 and 70 coincide on the photodetector 14 as shown in FIG.

  Even when the light emitting points of the light sources are different, the diffracted light on the photodetector 14 can be matched, so that the optical pickup head device of the present embodiment can also be miniaturized. Further, since the prism is not provided in the light source, the optical pickup head device is further inexpensive.

(Embodiment 5)
In this embodiment, if two diffraction patterns are given to the diffraction grating and the position of the diffraction grating is adjusted so that a plurality of diffracted lights have a predetermined positional relationship with respect to one storage medium, the other A diffraction grating that is automatically adjusted for a storage medium will be described.

  FIG. 9 shows a configuration of an optical pickup head device 900 according to the present embodiment. The difference from the optical pickup head device 300 (FIG. 3) shown in the second embodiment is that a half mirror 7 is used instead of the hologram element 64 (FIG. 3), and that a diffraction grating is provided between the prism 3 and the half mirror 7. 6, the use of the photodetector 13 instead of the photodetector 12 (FIG. 3), and the provision of the concave lens 11 between the half mirror 7 and the photodetector 13.

  The diffraction grating 6 has two grating surfaces 61 and 62. The distance from the light source 2 to the lattice plane 61 is 10 mm. The beams 4 and 5 emitted from the prism 3 are incident on the diffraction grating 6. The beams 4 and 5 transmitted through the diffraction grating 6 become three beams 4a to 4c and 5a to 5c, respectively, are reflected by the half mirror 7, and then converted into a convergent beam by the objective lens 9, and on the information recording surface 22. Focused. The beams 4 and 5 reflected by the information recording surface 22 pass through the objective lens 9 and the collimator lens 8 and then pass through the half mirror 7. By passing through the half mirror 7, astigmatism is given to the beams 4 and 5. Subsequently, the beams 4 and 5 are transmitted through the concave lens 11 whose optical axis is inclined. As a result, coma aberration imparted when passing through the half mirror 7 is corrected. Thereafter, the beams 4 and 5 are received by the photodetector 13. Based on the beams 4a to 4c and 5a to 5c received by the photodetector 13, a focus error signal and a tracking error signal are generated. The method will be described later.

  Hereinafter, the relationship between the optical storage medium 20, the beams 4a to 4c, 5a to 5c, and the diffraction grating 6 for generating the focus error signal and the tracking error signal will be described.

  FIG. 10 shows the relationship between the tracks on the information recording surface 22 of the optical storage medium 20 and the beams 4a to 4c and 5a to 5c. FIG. 10A schematically shows the relationship between the beams 4a to 4c and the tracks when the optical storage medium 20 is a CD-ROM. Information is recorded on a CD-ROM as a pit row having a length of 0.8 μm to 3.0 μm, a width of 0.5 μm, and a depth of about 0.1 μm, and the track pitch tp1 is 1.6 μm. Of the three beams 4a to 4c generated by the diffraction grating 6, the beam 4a is the 0th-order diffracted light, and the beams 4b and 4c are ± 1st-order diffracted light. The angle formed by the straight line connecting the spots of the beams 4a to 4c and the track is defined as θ1. Further, the distance L1b at which the beams 4a and 4b are shifted in the direction orthogonal to the track with respect to the track pitch is tp1 / 4, that is, 0.4 μm. An interval L1c at which the beams 4a and 4c are shifted in the direction orthogonal to the track is also tp1 / 4, that is, 0.4 μm. The three diffracted lights are adjusted to maintain the above-described relationship by rotating the diffraction grating 6. This arrangement is well known as a configuration for detecting a tracking error signal called a three-beam method.

  On the other hand, FIG. 10B schematically shows the relationship between the beams 5a to 5c and the tracks when the optical storage medium 20 is a DVD-RAM. In the DVD-RAM, information is recorded as pit rows of light and dark marks having a length of about 0.6 μm to 2.8 μm and a width of about 0.6 μm, and the track pitch tp2 is 0.74 μm. Further, unlike a DVD-ROM, a guide groove having a pitch gp2 of 1.48 [mu] m (= tw of tp2) and a depth of 0.07 [mu] m is formed, and the previous gray mark is formed between the grooves. Has been. Of the three beams 5a to 5c generated by the diffraction grating 6, the beam 5a is the 0th-order diffracted light, and the beams 5b and 5c are ± 1st-order diffracted lights. An angle formed by a straight line connecting the spots of the beams 5a to 5c and the track is defined as θ2. An interval L2b at which the beams 5a and 5b are shifted in the direction perpendicular to the track with respect to the track pitch is tp2 (= gp2 / 2), that is, 0.74 μm. An interval L2c at which the beams 5a and 5c are shifted in a direction perpendicular to the track is also tp2 (= gp2 / 2), that is, 0.74 μm. This arrangement is well known as a configuration for detecting a tracking error signal called a differential push-pull method to be described later.

  These angles θ1 and θ2 are defined based on the inclination of the grating pattern of the grating surfaces 61 and 62 of the diffraction grating 6, which will be described later with reference to FIG. The configuration and position of the diffraction grating 6 are adjusted so that the diffracted light and the track maintain such an angular relationship.

  FIG. 11 shows the grating patterns of the grating surfaces 61 and 62 of the diffraction grating 6. 11A shows the lattice plane 61, and FIG. 11B shows the lattice plane 62. FIG. The diffraction grating 6 is made by molding a resin having a refractive index of 1.52, and the distance b (FIG. 9) between the grating surfaces 61 and 62 is 1 mm. The grating pattern of the diffraction grating 6 is designed so that the intervals between the beams 4a and 4b, 4a and 4c, 5a and 5b, and 5a and 5c (FIG. 10) on the information recording surface of the optical storage medium 20 are substantially equal. ing. This is because the size of the light receiving portion of the photodetector 13 can be reduced if the intervals between the beams are the same.

  The pattern formed on the grating surface 61 shown in FIG. 11A generates a diffracted light upon receiving a beam with a wavelength λ1, but the grating depth is such that almost no diffracted light is generated upon receiving a beam with a wavelength λ2. This is optically an integral multiple of λ2. Further, the pattern formed on the grating surface 62 shown in FIG. 11B generates a diffracted light upon receiving a beam with a wavelength λ2, but hardly generates a diffracted light upon receiving a beam with a wavelength λ1. The grating depth is optically an integral multiple of λ1. For example, the grating depth is 2.3 μm and 1.9 μm, respectively. The grating pitches P1 and P2 are 74 μm and 83 μm, respectively.

  An axis 61a shown in FIGS. 11A and 11B serves as a reference axis when the diffraction grating 6 is manufactured. The diffraction grating 6 is configured such that the angle between the reference axis 61a and the spatial frequency axis 61b of the grating surface 61 is θ1, and the angle between the reference axis 61a and the spatial frequency axis 62b of the grating surface 62 is θ2. Has been. Since the diffraction grating 6 is formed as one diffraction grating 6 having the grating surfaces 61 and 62, even when the diffraction grating is mass-produced, the difference between the angles θ1 and θ2 is always kept constant. Incidentally, as described with reference to FIG. 10, the angle θ <b> 1 is an angle formed by a straight line connecting the spots of the beams 4 a to 4 c and a track on the information recording surface 22 of the optical storage medium 20. Further, the angle θ2 is an angle formed by a straight line connecting the spots of the beams 5a to 5c and the track. Therefore, the position of the diffraction grating 6 is rotated with respect to either one of the medium of CD or DVD, and the three diffracted lights are transmitted to the above-described L1b and L1c (FIG. 10A) or L2b and L2c (FIG. 10). If the adjustment is made to have the relationship (b)), the adjustment is automatically completed for the other medium. As a result, the adjustment process is greatly simplified, and the productivity of the optical pickup head device is dramatically improved. Further, by providing two grating surfaces on the diffraction grating 6, the size of the diffraction grating 6 becomes the same as that of a conventional diffraction grating having one grating surface, and an optical pickup head having two small light sources. The device can be configured.

  Next, a method for generating a focus error signal and a tracking error signal using the diffracted light obtained as described above will be described. Referring to FIG. 9 again, the photodetector 13 includes eight light receiving portions 13a to 13h, the beams 4a and 5a are the light receiving portions 13a to 13d, the beams 4b and 5b are the light receiving portions 13e to 13f, and the beam 4c. 5c is received by the light receiving portions 13g to 13h. When signals output according to the amounts of light received from the light receiving units 13a to 13h are I13a to I13h, respectively, the focus error signal is output from the four light receiving units 13a to 13d regardless of the type of medium. It is obtained by the calculation of (I13a + I13c) − (I13b + I13d) by the astigmatism method using the output signals I13a to I13d.

  On the other hand, the tracking error signal is calculated by (I13e + I13f)-(I13g + I13h) when the medium is a CD system such as a CD-ROM. When the medium is a DVD-ROM, the phase difference method compares the phases of I13a to I13d. And when the medium is a DVD-RAM, it is obtained by the calculation of (I13a + I13d) − (I13b + I13c) + k · {(I13e + I13g) − (I13f + I13h)}, respectively. Here, k is a coefficient for correcting the signal amplitude in accordance with the diffraction efficiency of the diffraction grating 6. In the case of DVD-RAM, a tracking error signal can also be obtained by (I13a + I13d)-(I13b + I13c), but an offset is likely to occur due to the movement of the objective lens in accordance with the tracking operation. The offset is reduced by the previous calculation.

  The method for generating the focus error signal and the tracking error signal has been described above.

  In the present embodiment, the design is performed so that θ2 is matched with the DVD-RAM. However, the optimum values of L1b and L1c are 0 according to the optimum values of L1b and L1c (FIG. 10), for example. .37 μm), the angle at which the spatial frequency axis of the grating surface 62 is tilted may be changed. Also, in the case of an information reproducing apparatus having a different light source wavelength and medium, the optical pickup head apparatus of the present invention can be applied if the optical design is performed according to the optical conditions. The optical design described above is an example, and the angles formed by the axes 61a and 61b and 61a and 62b can be arbitrarily designed. In this case, the pitches P1 and P2 of the grating may be changed. The concave lens 11 may not be used depending on the required optical specifications.

(Embodiment 6)
In the present embodiment, an optical pickup head device in which a tracking error signal is not greatly reduced by using a predetermined diffraction grating will be described.

  FIG. 12 shows an optical pickup head device 1200 of the present embodiment. The difference from the optical pickup head device 900 (FIG. 9) shown in the fifth embodiment is that a diffraction grating 63 is provided instead of the diffraction grating 6 (FIG. 9). By using the diffraction grating 63, the positional relationship between the beams 4a to 4c and 5a to 5c condensed on the optical storage medium 20 and the tracks and the positions of the beams 4a to 4c and 5a to 5c on the photodetector 13 are different. . The diffraction grating 63 has a single grating surface, and generates diffracted lights 4a to 4c and 5a to 5c, regardless of which of the light sources 1 and 2 is received.

  FIG. 13 shows the relationship between the tracks on the information recording surface 22 of the optical storage medium 20 and the beams 4a to 4c and 5a to 5c. FIG. 13A schematically shows the relationship between the beams 4a to 4c and the tracks when the optical storage medium 20 is a CD-R. In the CD-R, grooves having a pitch gp1 of 1.6 μm are formed, and information marks are recorded in either the grooves or between the grooves. The recorded mark has a length of about 0.8 μm to 3.0 μm and a width of about 0.6 μm. Unlike DVD-RAM, the track pitch tp1 and the groove pitch gp1 are the same. In the three beams 4a to 4c generated by the diffraction grating 6, 4a is 0th-order diffracted light, and 4b and 4c are ± 1st-order diffracted light. The distances L1b and L1c in the direction orthogonal to the tracks of the beams 4a and 4b, 4a and 4c are adjusted by rotating the diffraction grating 6 to an angle θ3 so as to be 0.8 μm (= tp1 / 2), respectively. .

  On the other hand, FIG. 5B schematically shows the relationship between the beams 5a to 5c and the tracks when the optical storage medium 20 is a DVD-RAM. The distances L2b and L2c in the direction orthogonal to the tracks of the beams 5a and 5b, 5a and 5c are formed with only one grating plane on the diffraction grating 63, so that when the medium is a CD, the relationship between the beam and the track is adjusted. The relationship between the beam and the track in the DVD is automatically determined to the angle θ3, which is 0.67 μm here. This is narrower than the interval of 0.74 μm shown in the second embodiment, but there is no problem because the offset of the tracking error signal is slightly reduced and no offset is generated. DVD-RAM also has a standard with a track pitch of 0.62 [mu] m with an increased recording density, and in order to reproduce information recorded on a medium with a track pitch of 0.62 [mu] m as well as 0.74 [mu] m, this embodiment The configuration of the optical pickup head device 1200 (FIG. 12) shown in FIG. This is because there is no significant decrease in the tracking error signal for any medium.

  In this embodiment, since one diffraction grating 63 is used, the beams 4a to 4c and 5a to 5c can be arranged on the photodetector 13 so as to be aligned in a straight line. When the medium is a DVD-ROM, the tracking error signal is calculated by a phase difference method that compares the phases of I13a to I13d. Otherwise, (I13a + I13d)-(I13b + I13c) + k1. Each can be obtained by the calculation of (I13g-I13h), that is, the differential push-pull method. Here, k1 and k2 are coefficients for correcting the signal amplitude in accordance with the diffraction efficiency of the diffraction grating 63 and the reflectance of the recorded and unrecorded portions of the optical storage medium 20.

  The optical pickup head device 1200 (FIG. 12) according to the present embodiment is suitable for a recordable information recording / reproducing device such as a CD-R or a DVD-RAM. Similarly to the optical pickup head device 600 (FIG. 6) shown in the third embodiment, the optical pickup head device 1200 (FIG. 12) also has the diffraction grating 63 (FIG. 12) as one of a medium of either CD or DVD. By adjusting the rotation for the other medium, the adjustment is automatically completed for the other medium, so that the adjustment process is simplified.

(Embodiment 7)
In the present embodiment, an optical pickup head device using a prism that is useful when the astigmatic difference between beams emitted from two light sources is different will be described.

  FIG. 14 shows an optical pickup head device 1400 of the present embodiment. The difference from the optical pickup head device 1200 (FIG. 12) shown in the sixth embodiment is that a prism 37 is provided instead of the prism 3 (FIG. 12).

  The prism 37 is formed with a total reflection surface 39 and a dichroic surface 38 having wavelength selectivity. The beam 4 emitted from the light source 1 is reflected by the total reflection surface 39 and then passes through the dichroic surface 38. On the other hand, the beam 5 emitted from the light source 2 is reflected by the dichroic surface 38. The beams 4 and 5 take the same optical path when exiting the prism 37.

  As the beam 4 of the light source 1, when a laser beam having an astigmatic difference of about 20 μm that is emitted like a gain waveguide laser and a prism 37 are used, the beam is propagated through the prism 37 to cause astigmatism. The gap can be corrected. Further, since the beam 5 emitted from the light source 2 does not propagate through the prism, no astigmatism is given to the beam 5. When the astigmatic differences of the beams emitted from the two light sources are different, the astigmatic difference of one of the beams can be corrected. Therefore, both of the two beams emitted from the prism 37 have a small wavefront aberration, and the optical storage medium. The information recorded in 20 can be read satisfactorily. That is, when the astigmatic difference between the beams emitted from the two light sources is different, the optical pickup head device shown in this embodiment is suitable.

  Similarly to the optical pickup head device 1200 (FIG. 12) shown in the sixth embodiment, the optical pickup head device 1400 of the present embodiment also rotates and adjusts the diffraction grating 63 with respect to one of the medium of either CD or DVD. As a result, the adjustment is automatically completed for the other medium. Therefore, the adjustment process is simplified.

  In addition, various optical configurations may be changed without departing from the spirit of the present invention.

(Embodiment 8)
In the present embodiment, an optical information device configured using the optical pickup head device described in the above embodiments will be described.

  FIG. 15 shows an optical information device 1500 of the present embodiment. The optical storage medium 20 loaded in the optical information device 1500 is rotated by the optical storage medium drive unit 81. The optical pickup head device 80 also sends a signal corresponding to the positional relationship with the optical storage medium 20 to the electric circuit unit 83. The electric circuit unit 83 amplifies or calculates this signal to finely move the optical pickup head device 80 or the objective lens in the optical pickup head device. The drive unit 82 is a drive unit for the optical pickup head device, and the objective lens drive unit 85 is a drive unit for the objective lens in the optical pickup head device. By the signal and the drive unit 82 or 85, focus servo and tracking servo are performed on the optical storage medium 20, and information is read from, written to, or erased from the optical storage medium 20. The connection part 84 is a connection with a power supply or an external power supply. From here, electricity is supplied to the electric circuit unit 83, the optical pickup head device drive unit 82, the optical storage medium drive unit 81, and the objective lens drive unit 85. Note that a connection terminal with a power source or an external power source is connected to each drive circuit. There is no problem even if it is provided.

DESCRIPTION OF SYMBOLS 1 Semiconductor laser light source 2 Semiconductor laser light source 3 Prism 6 Diffraction grating 7 Half mirror 8 Collimating lens 9 Objective lens 11 Concave lens 12 Photo detector 13 Photo detector 14 Photo detector 20 Optical storage medium 31 Reflective surface 32 Reflective surface 33 Reflective surface 34 Adhesive layer 35 Glass substrate 36 Glass substrate 37 Prism 38 Reflecting surface 39 Reflecting surface 41 Cutting surface 61 Lattice surface 62 Lattice surface 61a Axis 61b Spatial frequency axis 62b Spatial frequency axis 63 Diffraction grating 64 Hologram element 65 Hologram element 68 Hologram element 80 Optical pickup Head device 81 Optical storage medium drive unit 82 Optical pickup head device drive unit 83 Electric circuit 84 Power supply 85 Objective lens drive unit

Claims (1)

A first light source that emits a first beam having a wavelength λ1, a second light source that emits a second beam having a wavelength λ2 different from the wavelength λ1, and the first light source emitted from the first light source. And a second diffraction grating having a grating pattern for receiving a second beam emitted from the second light source and generating a plurality of diffracted lights of the 0th order and the first order, respectively, and a plurality of diffraction gratings from the diffraction grating The light condensing unit that receives the diffracted light and condenses it on the optical storage medium, the beam branching unit that receives and deflects the plurality of diffracted lights reflected by the optical storage medium, and the beam branching unit deflected by the beam branching unit An optical pickup head device having a light detection unit that receives the plurality of diffracted lights and outputs a signal corresponding to the received light quantity. In the diffraction grating, the first beam and the second beam are Received with the same lattice pattern, 0 each When the optical storage medium reproduces information by irradiating the first beam with the wavelength λ1, the optical storage medium has a first track having a track pitch of tp1. When information is reproduced by irradiating the second beam of wavelength λ2 using an optical storage medium, a second optical storage medium having a track with a track pitch of tp2 is used, and the track pitch is tp1> tp2. There is a relationship, and the interval between the zero-order diffracted light generated by the diffraction grating receiving the first beam and the first-order diffracted light in the direction perpendicular to the track of the first optical storage medium is substantially tp1 / 2. The light detection unit includes a plurality of light receiving units, and is generated when the diffraction grating receives the zero-order diffracted light generated by the diffraction grating receiving the beam of the wavelength λ1 and the beam of wavelength λ2. 0th order diffracted light The first-order diffracted light received by the same light receiving unit and generated by receiving the beam of wavelength λ1 by the diffraction grating is the same as the first-order diffracted light generated by receiving the beam of wavelength λ2 by the diffraction grating. An optical information reproducing method, wherein the optical information is received by a light receiving unit .

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