JP2004005945A - Optical pickup device and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin type optical pickup device for recording/reproducing data on/from a low density optical disk and a high density optical disk, and to provide an optical disk device using the optical pickup device. <P>SOLUTION: This optical pickup device has an LDA 11 of a short wavelength, an LDB 12 of a long wavelength, a beam splitter 41, an erect prism 23 for converting an optical axis into an optical axis perpendicular to an optical disk and an objective lens 32, wherein a composite filter 33 is arranged integrally with the objective lens 32, and the composite filter 33 is arranged oppositely to the erect prism 23 such that the surface of the composite filter 33 and the slant surface of the starting prism 23 are parallel to each other. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical pickup device used for recording information on an optical recording medium or reproducing information from the optical recording medium, and an optical disk device using the optical pickup device.
[0002]
[Prior art]
In recent years, computer devices have made remarkable progress in miniaturization and high performance. On the other hand, optical recording media are widely used because of their large storage capacity and easy handling, and are widely used as storage devices for computer devices. In addition, along with the downsizing of the computer apparatus, the optical disk apparatus handling the optical recording medium has also attained a significant downsizing.
[0003]
In order to reduce the size of the optical disk device, it is most important to reduce the size of the optical pickup device. Therefore, various proposals useful for miniaturization have been made. For example, an example of providing a thin optical disk device using a triangular rising prism (for example, see Patent Document 1) and an effect of improving wavefront aberration have been reported (for example, see Patent Document 2). .
[0004]
At the same time, optical disks, which are optical recording media, have also made remarkable progress. CD-ROM has spread as a low-density optical disk, and CD-R / RW has spread as its recording system. At the same time, a high-density optical disk has been developed, and a DVD-R / RW and a DVD-RAM of a recording system have been widely used after a DVD-ROM of a reproduction system.
[0005]
Note that the optical disk of the present invention is a generic term for an optical recording medium capable of reproducing or recording information using a light beam. Regardless of the difference in the method of using it together or not, regardless of whether it is housed in the jacket or not, it can be used in the form of a large or small outside diameter or a rectangular shape like a business card. Shall be used in a broad sense regardless of
[0006]
[Patent Document 1]
JP-A-11-134701 (page 3-8, FIG. 1-4)
[Patent Document 2]
JP-A-2000-195085 (pages 2 to 5, FIG. 1-4)
[0007]
[Problems to be solved by the invention]
However, since many types of media have become widespread, there is a need in the market to be compatible with these media and to further reduce the thickness of disk devices with the spread of portable computer devices.
[0008]
Therefore, in order to meet such market demands, the present invention provides an optical pickup device capable of recording / reproducing a low-density optical disk and recording / reproducing a high-density optical disk, and formed to have a reduced thickness, and It is an object of the present invention to provide an optical disc device formed with a thinner housing using the optical pickup device.
[0009]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and has a first light source that emits a first laser beam having a first wavelength, and a second light source that emits a second laser beam having a second wavelength. A second light source, a beam splitter for guiding the optical axis of the first laser light and the optical axis of the second laser light to a common optical axis, and converting the common optical axis to an optical axis perpendicular to the optical disk. And an objective lens for converging the first laser light and the second laser light on the respective optical discs, and the respective beam diameters of the first laser light and the second laser light. An optical pickup device, wherein a composite filter for controlling the polarization direction is arranged integrally with the objective lens, and the surface of the composite filter and the inclined surface of the rising prism are arranged to face each other so as to be parallel to each other. .
[0010]
According to the present invention, it is possible to perform recording or reproduction of a low-density optical disk and recording or reproduction of a high-density optical disk, and furthermore, an optical pickup device formed with a reduced thickness, and a reduction in thickness using the optical pickup device The optical disk device can be provided.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to solve the above problems, the present invention provides a first light source that emits a first laser light having a first wavelength, a second light source that emits a second laser light having a second wavelength, Beam splitter means for guiding the optical axis of the first laser light and the optical axis of the second laser light to a common optical axis, a rising prism for converting the common optical axis to an optical axis perpendicular to the optical disc, An objective lens for condensing the first laser light and the second laser light on the respective optical discs, and controlling a light beam diameter and a polarization direction of each of the first laser light and the second laser light; An optical pickup device is characterized in that the composite filter is disposed integrally with the objective lens, and the surface of the composite filter and the inclined surface of the rising prism are disposed so as to face each other so as to be parallel to each other.
[0012]
According to the present invention, it is possible to provide an optical pickup device having an optical system capable of reproducing or recording on a CD long wavelength system and reproducing or recording on a DVD short wavelength system. In addition, since at least one of the optical systems is a recursive system and the other optical system is a non-recursive system, the non-recursive detection system is shared with the recursive system, so the number of parts of the detection system is reduced and the carriage mounting space is also reduced. Thus, an inexpensive and small optical pickup device can be provided.
[0013]
Furthermore, since the third inclined surface of the rising prism and the composite filter face each other in parallel with each other, even if the focus shift of the objective lens is permitted, the objective lens and the composite filter are arranged close to each other. Thus, a thin optical pickup device can be configured. Accordingly, it is possible to provide an optical pickup device capable of recording / reproducing a low-density optical disk and recording / reproducing a high-density optical disk and having a reduced thickness, and an optical disk device thinned using the optical pickup device. be able to.
[0014]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. For the sake of simplicity, a DVD optical disk (hereinafter abbreviated as DVD) is used as an example of a high-density optical disk, and a CD optical disk (hereinafter abbreviated as CD) is used as an example of a low-density optical disk. . However, the present invention is not to be construed as being limited to these exemplified media. For example, a red wavelength DVD optical disc may be a low density optical disc, and a blue wavelength DVD optical disc may be a high density optical disc.
[0015]
(Embodiment 1)
FIG. 1 is a perspective view showing the entire optical pickup. In FIG. 1, 1 and 2 are optical recording media, 1 is a DVD (DVD optical disk), and 2 is a CD (CD optical disk). Both the optical disks DVD1 and CD2 are formed in a disk shape, and information tracks are formed in concentric (more precisely, spiral) shapes. When viewed from the optical disk, the arrangement direction of the information tracks is called a tangential direction (tangential direction), and the radial direction (radial direction) is called a tracking direction.
[0016]
The whole is collectively referred to as an optical pickup 9 and has the following main components. Reference numeral 11 denotes an LDA (semiconductor laser A) which emits a short wavelength laser as a light source for DVD. Reference numeral 12 denotes an LDB (semiconductor laser B), which emits a long-wavelength laser for a CD light source. The short-wavelength laser light emitted from the LDA 11 changes its direction by a mirror 42 and enters a CLA (collimator lens A) 21. The short-wavelength laser light converted from the diffused light into the parallel light by the CLA 21 enters the beam splitter 41. The long-wavelength laser light emitted from the LDB 12 passes through the integrating prism 13 and enters the CLB 22. The long-wavelength laser light converted from the diffused light into the parallel light by the CLB 22 also enters the beam splitter 41.
[0017]
The beam splitter 41 transmits the P-polarized light and reflects the S-polarized light with respect to the short-wavelength laser light, or reflects the entire light with respect to the long-wavelength laser light. And has a function of transmitting or reflecting depending on the polarization direction. More specifically, for example, a highly transparent resin material or an optical glass (hereinafter, abbreviated as a light transmitting member) formed in a parallel plate is used to transmit light to one surface by the wavelength and the polarization direction of light. Alternatively, it is realized by forming an optical thin film having a reflecting function.
[0018]
The laser beams of both wavelengths that have entered the beam splitter 41 are guided to the same optical axis (see the optical axis H in FIG. 3) and enter the rising prism 23. In the conventional optical path, the laser beams of both wavelengths travel almost in parallel with the surface of the optical disk. The laser beams of both wavelengths are reflected inside the rising prism 23 to change the course, and the light intensity distribution of the FFP (far field pattern) is shaped into a substantially circular shape, and is perpendicular to the surface of the optical disk (FIG. (See axis F).
[0019]
The laser beams of both wavelengths emitted from the rising prism 23 enter the objective lens unit 31. The objective lens unit 31 adjusts the diameter of the laser beam according to each wavelength, converts the laser beam into convergent light, and vertically enters the surface of the optical disk.
[0020]
Reference numeral 51 denotes a PDA (photodetector A as light receiving means), which receives and detects a part of the light emitted from the LDA 11 and LDB 12 extracted by the beam splitter 41. The light detected by the PDA 51 is fed back to the control of the light emission power of the LDA 11 and the LDB 12 by the control IC 61. Reference numeral 53 denotes an HFM (high-frequency module) that modulates the LDA 11 at a high frequency. The HFM 53 may be mounted together with the control IC 61. VOLA (volume A) 62 and 63 VOLB (volume B) are variable resistors (volumes) for adjusting the light emission power of LDA11 and LDB12, respectively.
[0021]
The return reflected light including the signal component reflected by the recording layer of the optical disk enters the beam splitter 41 in the reverse order described above. The beam splitter 41 reflects the return reflected light of both wavelengths again. Thus, the return reflected light including the signal component reflected by the recording layer of the optical disk is detected by the PDB 52 via the CLB 22 and the integration prism 13. The PDB 52 is a photodetector B as light receiving means, and detects return reflected light including a signal component reflected from a recording layer of an optical disc of each standard according to each wavelength.
[0022]
On the other hand, the actuator 8 supports the objective lens unit 31 in a displaceable manner. This is for focusing the light beam on the information recording layer of the optical disc (focusing) and for following in the minute tracking direction. The components described above are mounted on the carriage 7. Therefore, the movement exceeding the range of the tracking control in the tracking direction is dealt with by moving the entire carriage 7 in the radius (radial) direction of the optical disk.
[0023]
Next, each component will be described in order. The LDA 11 is a semiconductor laser A that emits a short-wavelength laser as a DVD light source. Even for an optical pickup device having a reduced thickness, a general-purpose semiconductor laser which is generally commercially available in both shape and characteristics is used.
[0024]
FIG. 2 is an exploded perspective view of a unit constituting the LDB. In FIG. 2, an LDB 12 is a semiconductor laser B that emits a long-wavelength laser for a CD light source. Similarly to the LDB 11, the LDB 12 uses a general-purpose semiconductor laser that is generally commercially available. Therefore, the most expensive essential parts can be procured at the lowest cost together with the LDB 11, and an inexpensive optical pickup device can be provided.
[0025]
Further, the LDB 12 constitutes one unit including the integration prism 13, the base member 19, and the PDB 52. The members may be integrated with each other via members that define their positions, the intervening member may be shared by the carriage 7, or may be directly fixed to each other. In general, the position of the light emitting point (not shown) of the LDB 12 has its center point coincident with the center point of the circular outer periphery of the stem 12a. The height of the light emitting point in the optical axis direction is defined by the height from the upper surface of the stem 12a. The plane of polarization of the emission beam is defined by an angle (usually parallel) with respect to an imaginary line connecting the marker 12b (V-shaped positioning groove) formed on the stem 12a.
[0026]
The base member 19 is provided with a base marker 19a (V-shaped positioning). By assembling the imaginary line connecting the base marker 19a and the imaginary line connecting the marker 12b with each other, the polarization plane of the emission beam can be displayed on the base member 19. The material of the base member 19 is selected from easily available metal materials such as Al, Zn, Fe, and brass which have excellent thermal conductivity and workability. The heat radiation of the LDB 12 from the stem 12a via the base member 19 can be more effectively promoted. Furthermore, using the base member 19 instead of the stem 12a, the LDB 12 can be easily attached to a member to be attached (the carriage 7 in the example of the present invention). This is because a structure suitable for the shape of the mounting position of the carriage 7 can be obtained without being restricted by the shape of the stem 12a.
[0027]
The integrating prism 13 is composed of first to fifth light guide members. As the material of each light guide member, a highly transparent resin material or optical glass is used. In particular, optical glasses such as SFL-1.6 and BK-7 have high refractive indices, so that the design margin of the diffraction grating and the film can be increased, and the wavelength shift during transmission is hard to occur. Among them, BK-7-1.5 is convenient because it is easily available and has excellent workability.
[0028]
The first light guide member 14 is formed in a parallel plate shape, and has a diffraction grating. This is because the light emitted from the LDB 12 is diffracted. The zero-order light and the ± first-order light thus obtained are used to generate main and sub beams (hereinafter, collectively referred to as three beams) used for tracking control.
[0029]
The second light guide member 15 is formed in a substantially triangular prism shape having a substantially right triangle cross section. A predetermined reflecting surface is formed on the slope of the substantially right triangle. This reflecting surface has a selective function of transmitting three beams of long wavelength for CD and reflecting return light of short wavelength for DVD. For example, a polarization beam splitter film or a wavelength selection film may be used.
[0030]
The third light guide member 16 is formed in a substantially trapezoidal column shape having a substantially trapezoidal cross section. One of the opposing parallel planes is joined to the second light guide member 15. A predetermined separation surface is formed on the other of the parallel planes. This separation surface has a selective separation function of transmitting three beams of long wavelength for CD, reflecting return light of long wavelength for CD, and transmitting return light of short wavelength for DVD. For example, a polarizing beam splitter film having a wavelength selecting function may be used.
[0031]
The fourth light guide member 17 is also formed in a substantially trapezoidal column shape having a substantially trapezoidal cross section. One of the opposed parallel planes is joined to the third light guide member 16. On the other of the parallel planes, a predetermined diffraction grating is formed. This diffraction grating functions as a reflection type diffraction grating for generating signal detection light with respect to the long wavelength return light for CD.
[0032]
The fifth light guide member 18 is formed in a substantially triangular prism shape having a right triangular cross section. Each surface forming a right angle becomes a reference surface of the integrating prism 13. It should be noted that these light guide members and the respective film forming configurations and diffraction gratings formed on each slope are technically disclosed in detail in Japanese Patent No. 2806293, Japanese Patent No. 3085148, and Japanese Patent Application Laid-Open No. 2001-31835. The description of the publication will be omitted with reference to the publication.
[0033]
FIG. 3 is a diagram for explaining the relationship between the rising prism and the objective lens unit, and is a diagram of the actuator 8 of FIG. 1 viewed from the radial direction (R display). In FIG. 3, the structure is partially exaggerated for easy understanding. First, the rising prism 23 is formed in a triangular prism shape having a substantially isosceles triangle cross section having an obtuse apex angle. The laser beams of both wavelengths are guided to the same optical axis H by the beam splitter 41. The prism 23 is arranged such that the surfaces forming the sides are inclined at a predetermined angle with respect to the optical axis H.
[0034]
The parallel light that has entered the inside from the first slope 24 of the rising prism 23 refracts and travels. When it reaches the third slope 26, it is totally reflected inside. When the light reaches the second slope 25, it is reflected again inside. When the light reaches the third slope 26 again, the light is refracted and transmitted, and travels from the third slope 26 of the rising prism 23 toward the objective lens unit 31.
[0035]
At this time, the rising prism 23 can function as an anamorphic prism by making the incident angle on the first slope 24 and the exit angle on the third slope 26 different. In other words, the FFP (Far Field Pattern) of the LDA 11 or LDB 12 has an elliptical light intensity distribution due to the anisotropy of the radiation divergence angle of the semiconductor laser, but has a substantially circular light intensity distribution by passing through the rising prism 23. Can be converted.
[0036]
Thus, the laser light emitted from the semiconductor laser can be focused on a minute spot. In particular, when the short-wavelength laser light of the LDA 11 is used for recording, the emitted laser light can be used for forming a recording spot without waste, so that a general-purpose semiconductor laser is used for the LDA 11 without using a high-power semiconductor laser. The most expensive essential parts can be procured at the lowest cost, and an inexpensive optical pickup device can be provided.
[0037]
Referring again to FIG. 3, reference numeral 31 denotes an objective lens unit in which the objective lens 32 and the composite filter 33 are integrally formed with a lens holder. The lens holder 34 is supported by the actuator 8 of FIG.
[0038]
The DVD 1 has a recording layer formed at a depth t1 = 0.6 mm from the surface (the lower surface of the disk). On the other hand, the CD has a recording layer formed at a depth t2 = 1.2 mm from the surface (the lower surface of the disk). Therefore, the objective lens 32 focuses the short wavelength of the DVD1 on the recording layer having a depth of 0.6 mm and the long wavelength of the CD on the recording layer having a depth of 1.2 mm for the parallel light having the same optical axis F. It works for you. Thus, even if the wavelength of the light source and the thickness of the medium up to the recording layer are different, it can function properly. That is, the objective lens 32 functions as a so-called special objective lens.
[0039]
The composite filter 33 is configured such that an aperture filter 35, a diffraction grating 36, and a quarter-wave plate 37 are integrally formed in this order from the side close to the light source, and are arranged together with the objective lens 32 in a lens holder 34. The aperture filter 35 controls the beam diameter of the transmitted laser light in order to satisfy both the standards of DVD1 and CD2 by sharing one objective lens 32. That is, as shown by the dotted line, the whole area is transmitted and a numerical aperture (hereinafter abbreviated as NA) of 0.6 is realized with respect to the DVD short wavelength. On the other hand, with respect to the long wavelength of the CD, as indicated by a dashed line, the light passes through the central region to realize an NA of 0.50. At this time, the light in the peripheral portion is absorbed (or reflected) by the material of the aperture filter 35.
[0040]
The diffraction grating 36 is formed by etching a light-transmitting resin material or optical crystal having optical anisotropy to form a transmission diffraction grating having polarization dependency. In the present embodiment, the grating depth is set so that it functions as a polarization-dependent transmission type diffraction grating for short wavelengths of DVD, does not function for long wavelengths of CD, and becomes a light transmitting member. I do. As described above, the long wavelength of the CD causes the signal detection light to be generated by the reflection type diffraction grating provided in the fourth light guide member 17.
[0041]
The 波長 wavelength plate 37 is designed at a wavelength intermediate between the DVD short wavelength and the CD long wavelength, and functions as a substantially 波長 wavelength plate for both laser beams.
[0042]
In this way, if the selected polarization direction of the diffraction grating 36, the linearly polarized light of the LDA 11 and the linearly polarized light (for example, P-polarized light) of the LDB 12 are orthogonal to each other, the light traveling from the light source to the optical disk (hereinafter abbreviated as outward light). Pass through the 影響 wavelength plate 37 without being affected by the diffraction grating 36. In the process of transmitting through the quarter-wave plate 37, the forward-path light of linearly polarized light is converted into circularly polarized light whose phase is rotated by 90 degrees, condensed by the objective lens 32, and forms an image on the recording layer of the optical disk.
[0043]
The light reflected on the recording layer of the optical disk (hereinafter abbreviated as return light) reaches the quarter-wave plate 37 via the objective lens 32 in the reverse order. In the process of transmitting through the quarter-wave plate 37, the return light of circular polarization is converted into linearly polarized light (for example, S-polarized light) whose phase is rotated by 90 degrees with respect to the outward light. At this time, the linearly polarized light (S-polarized light) of the return light has an angle of 90 degrees with the linearly polarized light (P-polarized light) of the outward light, and coincides with the selective polarization direction of the diffraction grating 36 described above. In this way, the return light of the DVD short wavelength is subjected to the diffraction action of the diffraction grating 36 and exits the composite filter 33.
[0044]
Since the objective lens 32 and the composite filter 33 are integrated with the lens holder 34, the best positional relationship between the objective lens 32 and the composite filter 33 is obtained even when the objective lens 32 performs a focus shift operation or a tracking shift operation. Is maintained, it is possible to configure an optical pickup device that is not easily affected by the lens shift. In addition, since the third inclined surface 26 of the rising prism 23 and the composite filter 33 are configured to face each other in parallel, even if the focus shift of the objective lens 32 is allowed, the objective lens 32 and the composite filter 33 are kept close to each other. And a thin optical pickup device can be configured.
[0045]
Next, the operation of the optical pickup device of the present invention configured as described above will be described. For the sake of simplicity, the description will be divided into a DVD short wavelength system and a CD long wavelength system. FIG. 4 is a diagram for explaining the operation of the short wavelength system. 4 shows a section from the light source to the beam splitter 41 as viewed from the Z direction in FIG. 1, and a section from the beam splitter 41 to the optical disk as viewed from the R direction in FIG. FIG.
[0046]
First, the DVD short wavelength system will be described. The DVD short-wavelength laser light emitted from the LDA 11 (hereinafter, abbreviated as forward light A101 and indicated by a two-dot chain line) enters the CLA 21 via the mirror 42. The outward light A <b> 101 converted from the diffused light into the parallel light by the CLA 21 enters the beam splitter 41. The outward light A101 refracted and transmitted through the beam splitter 41 is incident on the rising prism 23. At this time, the outward light A101 is converted from the optical axis H to the optical axis F by repeating refraction and reflection as described above. At the same time, the light intensity distribution is converted from an elliptical distribution to a substantially circular distribution by the ratio between the incident angle on the first slope 24 and the exit angle on the third slope 26. Hereinafter, this conversion ratio is abbreviated as beam shaping magnification.
[0047]
Further, the outward light A101 enters the composite filter 33. At this time, as described above, the outward light A101 is adjusted to a luminous flux diameter equivalent to NA of 0.6 by the aperture filter 35, travels without being affected by the diffraction grating 36, passes through the quarter wavelength plate 37, and becomes circularly polarized light. Is converted. Further, the light is focused on the DVD 1 by the objective lens 32. Then, the outward light A101 has an NA of 0.6 and focuses on the recording layer having a depth of 0.6 mm of the DVD1.
[0048]
The outward light A101 is reflected by the recording layer and travels in the opposite optical path again. That is, the return light A102 (shown by a solid line). The return light A 102 is again converted into parallel light by the objective lens 32 and enters the composite filter 33. The light is converted to linearly polarized light (S-polarized light) rotated by 90 degrees through the quarter-wave plate 37, and is subjected to the diffraction effect of the diffraction grating 36, so that the return light A102 further travels in the opposite optical path. The return light A 102 is converted from the optical axis F to the optical axis H by the rising prism 23.
[0049]
Since the return light A102 is linearly polarized light rotated by 90 degrees with respect to the forward light A101, it is reflected on the surface of the beam splitter 41, separated from the forward light, and travels to the LDB 12. The return light A102 is converged again by the CLB 22 and enters the integration prism 13. That is, the DVD short-wavelength system is a non-recursive optical system because the return light B102 does not return to the starting point of the forward light A101.
[0050]
5A and 5B are diagrams illustrating the operation of the integrated prism, FIG. 5A is a diagram illustrating the operation at the short wavelength of the DVD, and FIG. 5B is a diagram illustrating the operation at the long wavelength of the CD. . 4 and 5A, the return light A102 enters the fourth light guide member 17 from the end face, passes through the third light guide member 16, and reaches the slope of the second light guide member 15. This slope is formed, for example, on the reflection surface of the wavelength selection film. Done. Since the optical path length from the diffraction grating 36 to the detection position PDB 52 is long, a sufficient separation effect can be obtained by a slight diffraction effect. That is, the production of the diffraction grating 36 is facilitated, so that the cost can be reduced.
[0051]
In recording the DVD 1, it is necessary to detect the accurate optical power of the LDA 11 and perform optical power control. Therefore, the PDA 51 is arranged near the beam splitter 41, and when the outward light A101 enters the beam splitter 41, a part of the outward light A101 slightly reflected from the surface (incident surface) of the beam splitter 41 is detected. . That is, the monitor light A103 is indicated by a dotted line in FIG.
[0052]
When a semiconductor laser having a large radiation divergence anisotropy (aspect ratio) is used, the LDA 11 is set by setting the beam shaping magnification of the rising prism 23 between 1.1 and 1.3. When the short-wavelength laser light is used for recording, the emitted laser light can be used for forming a recording spot without waste. In recording and reproducing in a DVD short wavelength system, control of astigmatism is important. When the rising prism 23 has a beam shaping function, astigmatism can be controlled by slightly changing the parallelism of the parallel light incident on the rising prism 23.
[0053]
More specifically, the astigmatism can be adjusted by slightly changing the distance between the LDA 11 and the DVD collimator CLA 21. If the rising prism 23 does not have a beam shaping function (beam shaping ratio 1.0), a wedge prism can be added to the beam splitter 41 to adjust the astigmatism of the DVD short wavelength system. . At this time, the wedge-shaped prism functions as an astigmatism correction member. Of course, the beam splitter 41 to which the wedge prism is added may be integrally formed.
[0054]
Next, the CD long wavelength system will be described. FIG. 6 is a diagram for explaining the operation of the long wavelength system. As in FIG. 4, a section from the light source to the beam splitter 41 represents a view from the Z direction in FIG. 1, and a section from the beam splitter 41 to the optical disk represents a view from the R direction in FIG. In FIG. 5B and FIG. 6, the laser light of the CD long wavelength emitted from the LDB 12 (hereinafter, abbreviated as forward light B 111 and indicated by a two-dot chain line) is the first light guide member 14 of the integrated prism 13. , Three beams are generated. Further, the outward light B111 sequentially passes through the second light guide member 15, the third light guide member 16, and the fourth light guide member 17, and exits from the end face of the fourth light guide member 17.
[0055]
The outward light B111 exits the integrating prism 13 and then enters the CLB 22. The light is converted from the diffused light into the parallel light by the CLB 22. Next, the outward light B111 is reflected by the surface of the beam splitter 41 and enters the rising prism 23. At this time, the outgoing light B111 is converted from the optical axis H to the optical axis F by repeating refraction and reflection in the same manner as the above-mentioned DVD diameter short wavelength. At the same time, when the rising prism 23 is provided with a beam shaping function, the light intensity distribution is converted from an elliptical distribution to a circular distribution according to the beam shaping ratio.
[0056]
Further, the outward light B111 enters the composite filter 33. At this time, the outward light B111 is restricted by the aperture filter 35 so that the light beam diameter becomes a predetermined beam diameter. The outward light B111 travels without being affected by the diffraction grating 36 because the wavelength is different. Next, the light is converted into circularly polarized light via a quarter-wave plate 37. Further, the light is focused on the CD 2 by the objective lens 32. The forward light B111 is focused on a recording layer of CD2 having a depth of 1.2 mm with an NA of 0.50 according to the standard.
[0057]
The outward light B111 is reflected by the recording layer and travels in the opposite optical path again. That is, the return light B112 (shown by a solid line). The return light B112 is converted into parallel light again by the objective lens 32 and enters the composite filter 33. After passing through the quarter-wave plate 37, the light is converted into linearly polarized light rotated by 90 degrees with respect to the outgoing light B111 and transmitted through the diffraction grating 36, and the backward light B112 further travels in the opposite optical path. The return light B 112 is converted from the optical axis F to the optical axis H by the rising prism 23. Further, the return light B112 is reflected on the surface of the beam splitter 41 and travels to the LDB 12 again. The return light B112 is converged again by the CLB 22 and enters the integration prism 13.
[0058]
In other words, the CD long wavelength system is a recursive optical system since the return light B112 returns to the starting point of the forward light B111. In the section from the beam splitter 41 to the optical disk via the objective lens 32, the forward light A101, the backward light A102, the forward light B111, and the backward light B112 all pass in common. The optical axis.
[0059]
The return light B112 enters the fourth light guide member 17 from the end face, passes through the fourth light guide member 17, and reaches the slope of the third light guide member 16. For example, a polarization beam splitter film is formed on this slope, and the return light B112 (S-polarized light) whose polarization plane is rotated by 90 degrees is reflected. Further, the light passes through the fourth light guide member 17 and reaches the slope of the fourth light guide member 17. A reflection type diffraction grating is formed on this slope, and the return light B112 separates and generates signal detection light and reflects it. The return light B112 is reflected again on the slope of the third light guide member 16 and exits from the other end face of the fourth light guide member 17. The return light B112 enters the PDB 52, and the signal of CD2 is detected.
[0060]
When recording the CD2, it is necessary to detect the accurate optical power of the LDB 12 and perform the optical power control. Therefore, the PDA 51 is also used for the CD2. When the outward light B111 is reflected on the surface of the beam splitter 41, a part of the outward light B111 slightly entering the inside of the beam splitter 41 from the surface (reflection surface) of the beam splitter 41 is detected. That is, the monitor light B113 is indicated by a dotted line in FIG. Thus, even in the CD long wavelength system, the optical power can be controlled by detecting the accurate optical power.
[0061]
(Embodiment 2)
In the above description, it was described that the beam splitter 41 was formed in a parallel plate. Alternatively, the description has been made assuming that a wedge-shaped prism is combined with the parallel-plate beam splitter 41. Therefore, next, an embodiment in which the beam splitter 41 is formed in a different shape will be described. FIG. 7 shows a second embodiment relating to the beam splitter, in which the beam splitter 41 in FIGS. 4 and 6 is replaced by the beam splitter 43 of the second embodiment. Since all other components are the same as those described in FIGS. 4 and 6, the same reference numerals are given and duplicate description is omitted.
[0062]
As the material of the beam splitter 43, similarly to the integrated prism 13, a highly transmissive resin material or optical glass (hereinafter, abbreviated as a light transmitting member) is used. The beam splitter 43 is formed in a quadrangular prism having a quadrangular cross section, and has a separation surface 44 formed therein. Alternatively, a triangular prism having the separation surface 44 may be attached to form a quadrangular prism. Like the beam splitter 41, the separation surface 44 has a function of transmitting or reflecting, for example, depending on the wavelength and polarization direction of light, and is formed by forming an optical thin film.
[0063]
More specifically, the separation surface 44 forms a wavelength selection film and functions as wavelength selection means for separating short-wavelength laser light and long-wavelength laser light. The wavelength selection film transmits 90% or more of a short-wavelength laser light (wavelength for DVD: 635 to 670 nm) and reflects 90% or more of a long-wavelength laser light (wavelength for CD: 780 nm). Accordingly, the outgoing light A101 having a short wavelength emitted from the LDA 11 is converted into a parallel light beam by the collimator lens 21, and then the outgoing light A101 passes through the separation surface 44 and enters the rising prism 23. At this time, the remaining light of 10% or less of the separation surface 44 is reflected and becomes the monitor light A103 and enters the PDA 51.
[0064]
On the other hand, the long-wavelength outgoing light B111 emitted from the LDB 12 is converted into a parallel light beam by the collimator lens 22, and then the outgoing light B is reflected by the separation surface 44 and enters the rising prism 23. At this time, the remaining light of 10% or less of the separation surface 44 is transmitted and becomes the monitor light B <b> 113 and enters the PDA 51.
[0065]
As described above, since a part of the light emission energy of the outward light A101 and the outward light B111 can be directly monitored by the PDA 51 by the PDA 51, accurate control of the recording power can be realized. In addition, since the separation surface 44 has a structure sandwiched between the highly transparent resin material and the optical glass, the film formation design of the wavelength selection film formed on the separation surface 44 becomes easy. Therefore, it can be easily manufactured and formed at low cost.
[0066]
Also, as shown exaggeratedly in FIG. 7, by setting the surface of the quadrangular prism to an angle slightly inclined with respect to the optical axis, the surface reflected light reflected on the surface of the beam splitter 43 is affected on the optical system. (In particular, do not return to the direction of LDA11 or LDB12). Thus, there is no need to form an anti-reflection film or the like on the surface of the beam splitter 43, and the beam splitter 43 can be formed at low cost.
[0067]
Further, as shown in an exaggerated manner in FIG. 7, one side of a quadrangular cross section is extended along the optical axis of one of the outward light (in the example of FIG. 7, the light of the backward light A102 or the outward light B111). (In the axial direction). Thus, the optical path length can be adjusted using the refractive index of the beam splitter 43.
[0068]
As described in detail above, it is possible to provide an optical pickup device having an optical system capable of reproducing and recording on a CD long wavelength system and reproducing and recording on a DVD short wavelength system. it can. In addition, since at least one of the optical systems is a recursive system and the other optical system is a non-recursive system, the non-recursive detection system is shared with the recursive system, so the number of parts of the detection system is reduced and the carriage mounting space is also reduced. Thus, an inexpensive and small optical pickup device can be provided.
[0069]
Furthermore, since the third inclined surface 26 of the rising prism 23 and the composite filter 33 are configured to face in parallel with each other, even if the focus shift of the objective lens 32 is allowed, the objective lens 32 and the composite filter 33 are still connected. They can be arranged close to each other, and a thin optical pickup device can be configured. Thus, an optical pickup device capable of recording / reproducing a low-density optical disk and recording / reproducing a high-density optical disk and having a reduced thickness, and an optical disk device thinned using the optical pickup device are provided. be able to.
[0070]
【The invention's effect】
According to the present invention, an optical pickup device capable of recording / reproducing a low-density optical disk and recording / reproducing a high-density optical disk and having a reduced thickness, and an optical disk thinned using the optical pickup device An apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an entire optical pickup. FIG. 2 is an exploded perspective view of a unit constituting an LDB. FIG. 3 is a view for explaining a relationship between a rising prism and an objective lens unit. FIG. FIG. 5 is a diagram illustrating the operation of an integrated prism. FIG. 6 is a diagram illustrating an operation of a long wavelength system. FIG. 7 is a diagram illustrating a second embodiment related to a beam splitter.
1 DVD (DVD optical disk)
2 CD (CD optical disk)
3 Housing 4 Upper cover 5 Lower cover 6 Tray 7 Carriage 8 Actuator 9 Optical pickup 11 LDA (semiconductor laser A)
12 LDB (Semiconductor laser B)
13 integrated prism 14 first light guide member 15 second light guide member 16 third light guide member 17 fourth light guide member 18 fifth light guide member 19 base member 21 CLA (collimator lens A)
22 CLB
23 Rising prism 24 First slope 25 Second slope 26 Third slope 31 Objective lens unit 32 Objective lens 33 Composite filter 34 Lens holder 35 Opening filter 36 Diffraction grating 37 Quarter wave plates 41, 43 Beam splitter 42 Mirror 44 Separation Surface 51 PDA
52 PDB
53 HFM (high frequency module)
61 Control IC
62 VOLA
63 VOLB
101 Outbound light A
102 Return light A
103 Monitor light A
111 Outbound light B
112 Return light B
113 Monitor light B

Claims (16)

A first light source that emits a first laser light having a first wavelength, a second light source that emits a second laser light having a second wavelength, and an optical axis of the first laser light. Beam splitter means for guiding the optical axis of the second laser light to a common optical axis; a rising prism for converting the common optical axis to an optical axis perpendicular to the optical disk; An objective lens for condensing the second laser light and the respective optical discs,
A composite filter for controlling the light beam diameter and the polarization direction of each of the first laser light and the second laser light is disposed integrally with the objective lens, and a surface of the composite filter and a slope of the rising prism are disposed. An optical pickup device characterized in that they are arranged so as to face each other so as to be parallel to each other. 2. The optical pickup device according to claim 1, wherein at least one of the first wavelength and the second wavelength has an optical output for emitting a laser beam recordable on an optical disk. 2. The optical pickup device according to claim 1, wherein the rising prism is arranged at a predetermined inclination angle with respect to the common optical axis, and a beam shaping magnification is set between 1.1 and 1.3. . The second wavelength has a longer wavelength than the first wavelength, and an astigmatism correction member is disposed at a position where the first wavelength enters the beam splitter means. Item 2. The optical pickup device according to item 1. A first light source that emits a first laser light having a first wavelength, a second light source that emits a second laser light having a second wavelength, and an optical axis of the first laser light. Beam splitter means for guiding the optical axis of the second laser light to a common optical axis; a rising prism for converting the common optical axis to an optical axis perpendicular to the optical disk; An objective lens for condensing the second laser light and the respective optical discs,
The light source of at least one of the first wavelength and the second wavelength has a light output for emitting a laser beam recordable on an optical disk, and a light source for the first laser beam and the second laser beam. A composite filter for controlling each light beam diameter and a polarization direction is arranged integrally with the objective lens, and a surface of the composite filter and an inclined surface of the rising prism are arranged to face each other so as to be parallel to each other. Optical pickup device. 6. The optical pickup device according to claim 5, wherein the rising prism is disposed at a predetermined inclination angle with respect to the common optical axis, and a beam shaping magnification is set between 1.1 and 1.3. . The second wavelength has a longer wavelength than the first wavelength, and an astigmatism correction member is disposed at a position where the first wavelength enters the beam splitter means. Item 6. An optical pickup device according to item 5. A first light source for emitting a first laser light having a first wavelength, a second light source for emitting a second laser light having a second wavelength longer than the first wavelength, Beam splitter means for guiding the optical axis of the first laser beam and the optical axis of the second laser beam to a common optical axis; a rising prism for converting the common optical axis to an optical axis perpendicular to the optical disc; An objective lens for condensing the first laser light and the second laser light on the respective optical discs, and a light receiving element for detecting reflected light from the optical discs according to the first wavelength and the second wavelength Means, and an integrated prism for guiding the reflected light from the optical disc to the first wavelength and the second wavelength to the light receiving means, respectively.
The second light source, the integrated prism, and the light receiving unit are integrally disposed,
The second light source has a light output for emitting a laser beam recordable on an optical disc, and includes a composite filter for controlling the beam diameter and the polarization direction of each of the first laser beam and the second laser beam. Placed integrally with the objective lens,
An optical pickup device, wherein a surface of the composite filter and an inclined surface of the rising prism are opposed to each other so as to be parallel to each other. 9. An optical pickup device according to claim 8, wherein said beam splitter means has an optical thin film formed on one surface of a light transmitting member formed in a parallel plate. 9. The optical pickup device according to claim 8, wherein said beam splitter means is formed as a quadrangular prism having a quadrangular cross section having a separation surface on which an optical thin film is formed. 11. The optical pickup device according to claim 10, wherein the beam splitter has a shape in which some sides of the quadrilateral are extended in a direction of a specific optical axis. A first light source for emitting a first laser light having a first wavelength, a second light source for emitting a second laser light having a second wavelength longer than the first wavelength, Beam splitter means for guiding the optical axis of the first laser beam and the optical axis of the second laser beam to a common optical axis; a rising prism for converting the common optical axis to an optical axis perpendicular to the optical disc; An objective lens for condensing the first laser light and the second laser light on the respective optical discs, and a light receiving element for detecting reflected light from the optical discs according to the first wavelength and the second wavelength Means, and an integrated prism for guiding the reflected light from the optical disc to the first wavelength and the second wavelength to the light receiving means, respectively.
The second light source, the integrated prism, and the light receiving unit are integrally disposed,
The first light source and the second light source both have a light output for emitting a laser beam recordable on an optical disc, and have respective luminous flux diameters of the first laser beam and the second laser beam. An optical pickup device, wherein a composite filter for controlling a polarization direction is disposed integrally with the objective lens, and a surface of the composite filter and a slope of the rising prism are disposed so as to face each other so as to be parallel to each other. . 13. The optical pickup device according to claim 12, wherein the beam splitter has an astigmatism correction member. 13. The optical pickup device according to claim 12, wherein said beam splitter means is formed as a quadrangular prism having a quadrangular cross section having a separation surface on which an optical thin film is formed. 15. The optical pickup device according to claim 14, wherein the beam splitter has a shape in which a part of a side of the quadrilateral is extended in a direction of a specific optical axis. 13. An optical disk device using the optical pickup device according to any one of claims 1, 5, 8, and 12.

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