JP3854809B2 - Optical head device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical head used in an optical disk device such as an optical disk or a magnetic disk.
[0002]
[Prior art]
An optical disc is an information medium having features such as non-contact, large capacity, and low cost. Compact discs (hereinafter referred to as CDs) widely used in various applications such as music and computers are recordable discs such as CD-Rs and CD-RWs, in addition to CD-ROMs dedicated to playback. The spread of is also progressing rapidly.
[0003]
On the other hand, in recent years, large capacity disks such as a digital versatile disk (hereinafter referred to as DVD) having a capacity about seven times that of a CD have appeared. Thus, in the situation where there are a plurality of types of optical disks, there is a strong demand for a DVD / CD compatible optical head apparatus that can perform recording and reproduction with respect to the plurality of optical disks with a single apparatus.
[0004]
In order to reproduce a DVD-ROM, a laser light source having a wavelength of 650 nm is necessary, whereas in order to reproduce a CD-R, a laser light source having a wavelength of 780 nm is necessary. This is because the CD-R has a low reflectance near the wavelength of 650 nm. Therefore, it is necessary to mount two laser light sources on the DVD / CD compatible optical head.
[0005]
To reduce the size and cost of the optical head, it has a reflecting surface that combines two wavelengths with one prism, or separates the light beam going to the information recording medium and the light beam going back to the photodetector. The prism is indispensable, and the mounting of the prism ensures positional accuracy and may require adjustment in some cases. Conventional examples are disclosed in Japanese Patent Application Laid-Open No. 2000-82226 and Japanese Patent Application Laid-Open No. 2000-163787, but the shape related to the position fixing method of the prism is not discussed.
[0006]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide an optical head device that can easily secure positional accuracy during prism assembly.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, in the optical head of the present invention, the first laser light source that emits the light beam having the first wavelength and the light beam having the second wavelength that is different from the first wavelength are emitted. Two laser light sources, an optical component that guides the light beam emitted from the first laser light source or the second laser light source to the information recording medium by reflecting or transmitting the light beam, and an object that focuses the light beam on the information recording medium. A lens; an actuator that drives the objective lens; a photodetector that receives the light beam reflected by the information recording medium; and a holding member that holds the optical component. The optical component includes a first triangular prism, a second triangular prism, and a prism having two reflecting surfaces parallel to each other. Of the two reflecting surfaces of the prism, the optical component is a laser light source. The first reflecting surface on the near side is a surface that transmits the light beam of the first wavelength and reflects the light beam of the second wavelength to combine the optical paths of the respective light beams, and the other second reflecting surface. Is a surface that reflects and guides each light beam that has passed through the optical path to the information recording medium. The first reflecting surface of the prism and the first triangular prism are joined together, and the second reflecting surface of the prism and the second reflecting surface are connected to each other. 2 triangular prisms are joined, a part of the first reflecting surface of the prism is exposed, the exposed portion of the first reflecting surface is brought into contact with the holding member, and the first reflecting surface 45 The optical component is positioned by bringing the holding surface into contact with the surface forming an angle of degrees. It is fit.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. Here, as an example, an optical head device capable of reproducing CD-R recording and CD and DVD will be described. FIG. 1 is a perspective view showing an optical head device and is a partially exploded view. 2 is a diagram illustrating the configuration of a standard prism and the optical axis, FIG. 3 is a diagram illustrating an optical axis change in consideration of actual prism variations, FIG. 4 is an embodiment of the present invention, and FIG. An embodiment of a prism having two parallel reflecting surfaces and a part of the reflecting surfaces exposed is shown.
[0009]
In FIG. 1, the optical head case 1 is equipped with a laser light source 2a that oscillates near a wavelength of 655 nm, and a laser light source 2b that oscillates near a wavelength of 785 nm. Reference numerals 3 and 4 are auxiliary lenses. 5 is a prism having a wavelength and selectivity for transmittance and reflectance (hereinafter referred to as dichroic prism), 6 is a half mirror having a wavelength and selectivity for transmittance and reflectance (hereinafter referred to as dichroic half mirror), and 7 is It is fixed to the case 1 with a collimating lens. 8 is a raising mirror, 9 is an actuator, 10 DVD / CD compatible special objective lens (hereinafter referred to as an objective lens), 11 is an optical disk, 12 is a detection lens, 13 is a photodetector, and 14 is a front monitor. The actuator 9 includes a wire support portion 17 for mounting a total of four wires by the focus coil wire 15 and the tracking coil wire 16, an objective lens 9, a focus coil 18, a tracking coil 19, etc. on the opposite side of the wire support portion 17. The lens-coil holder 20 is fixed to the case 1 and the yoke plate 21 is fixed to the case 1.
[0010]
The case 1 may be made of a material such as zinc die cast, magnesium, or glass fiber reinforced plastic, but there is no problem, but this embodiment is zinc die cast. The laser light source 2a is driven by the DVD integrated circuit 31 and has a high frequency superimposed thereon. The laser light source 2b is driven by the CD-R integrated circuit 33 and has a high frequency superimposed thereon. Note that the laser light sources 2a and 2b, the DVD integrated circuit 31, the CD-R integrated circuit 33, the photodetector 13, and the front monitor 14 are connected to a signal input / output conductor 28 (not shown).
[0011]
Next, the operation will be described. A description will be given of a light beam having an oscillation wavelength of 655 nm, that is, an optical system for reproducing a DVD. The laser light source 2a emits divergent light having a wavelength of about 655 nm and a polarization direction parallel to the Y axis in the drawing. The emitted light is incident on the auxiliary lens 3 having a function of diverging the light beam, and the divergent light emitted from the auxiliary lens 3 is reflected by the dichroic prism 5 and the dichroic half mirror 6 and then substantially collimated by the collimating lens 7. It becomes.
[0012]
In this embodiment, the dichroic prism 5 reflects light with a wavelength of about 655 nm by about 100%, and the dichroic half mirror 6 reflects light with a wavelength of about 655 nm by about 50%. The light beam emitted from the collimating lens 7 is reflected by the rising mirror 8 and is narrowed down to the optical disk 11 by the objective lens 10 to form a light spot. The reflected light from the optical disk 11 passes through the objective lens 10, the rising mirror 8, and the collimating lens 7 again and enters the dichroic half mirror 6. About 50% of the incident light passes through the dichroic half mirror 6, passes through the detection lens 12, and is guided to the photodetector 13.
[0013]
Next, a light beam with an oscillation wavelength of 785 nm, that is, a CD system will be described. The laser light source 2b emits divergent light having a wavelength of about 785 nm and a polarization direction parallel to the X axis in the drawing. Here, a plano-convex lens is used as the auxiliary lens 4, and a diffraction grating is provided on the plane side thereof. The divergent light emitted from the auxiliary lens 4 passes through the dichroic prism 5 and is reflected by the dichroic half mirror 6, and then becomes a substantially parallel light beam by the collimator lens 7. In this embodiment, the dichroic prism 5 transmits almost 100% of light having a wavelength of about 785 nm, and the dichroic half mirror 6 reflects light of about 90% of light having a wavelength of about 785 nm. About 10% of the light incident on the dichroic half mirror 6 passes through the dichroic half mirror 6 and enters the front monitor 14. The front monitor 14 is provided for detecting a change in laser light intensity when recording a signal on a CD-R disc. The light beam emitted from the collimating lens 7 is reflected by the rising mirror 8 and is narrowed down to the optical disk 11 by the objective lens 10 to form a light spot. The reflected light from the optical disk 11 passes through the objective lens 10, the raising mirror 8, and the collimating lens 7 again and enters the dichroic half mirror 6. About 10% of the incident light passes through the dichroic half mirror 6, passes through the detection lens 12, and is guided to the photodetector 13. The light guided to the above-described photodetector 13 is used to detect a light spot control signal such as a focus error and a track error and an information signal recorded on the optical disc 11.
[0014]
The dichroic prism 5 shown in FIG. 1 will be described in detail with reference to FIGS. In FIG. 2, the dichroic prism 5 is composed of a left triangular prism 44 and a right triangular prism 45. A dichroic film is formed on the joint surface to reflect the DVD laser 2a and transmit the light from the CD-R laser 2b as described above. I am letting. In the figure, the one-dot chain line arrow is the optical axis of the light emitted from each laser. Further, the triangular prism 44 and the triangular prism 45 are bonded together to be integrated, and are positioned on the case 1 (not shown) by the holding members 41, 42 and 43. When the triangular prism 44 and the triangular prism 45 are misaligned, the result is as shown in FIG. In other words, the prism 46 and the cut portion 47 were originally an integral triangle. The prism 48 and the cut portion 49 were also an integral triangle. When there is a sticking shift as shown in FIG. 3, the shape is a square, but the size is increased by ΔL with respect to the original dimension L, and when it is brought into contact with the holding member, the reflecting surface moves to the left in FIG. On the other hand, since the position of the optical axis emitted from the laser light source 2a (not shown) is the same, as a result, the optical axis going to the left in the figure is shifted downward. When the angle of the joint surface is 45 degrees, this amount of change is equal to ΔL.
[0015]
FIG. 4 shows an embodiment of the present invention. That is, the dichroic prism 5 is composed of a triangular prism 50 and a triangular prism 51, and a part of the joint surface of the triangular prism 50 is exposed by the holding member 43 as much as possible. When the holding members 41, 42, and 43 are arranged as shown in FIG. 4 and the triangular prism 50 is pressed to the right side, precise positioning is possible by the wedge effect. Even if there is a misalignment of the triangular prism 51, the positioning is performed with only one component, so the position variation is much less. Specifically, when the joint surface is 45 degrees and the angle variation is 0.1 degrees, assuming that the holding member interval is 4 mm span, the above-described ΔL is 0.005 mm or less. On the other hand, ΔL due to sticking deviation in the case of FIG. 3 is assumed to be about 0.1 mm, which can be greatly improved to 1/200. Further, the triangular prism 51 needs to be relatively smaller than the triangular prism 50, but the closer to the laser light source, the smaller the luminous flux and the easier application of the present invention becomes. A broken line arrow and an alternate long and short dash line in the figure indicate a light flux and an optical axis.
[0016]
FIG. 5 shows an embodiment of the present invention. In FIG. 4, the triangular prism 50 and the triangular prism 51 are joined and arranged in the case 1 separately from the dichroic half mirror 6, but in FIG. This is an embodiment having a composite configuration comprising a flat plate 53 and a triangular prism 54. Such a method has many advantages such as the positioning accuracy is improved because the distance between the holding members 55 and 56 can be increased, and the parallelism of the two reflecting surfaces is determined only by the accuracy of the parallel plate 53. The arrangement of the holding members 55, 56, and 57 and the direction in which the dichroic prism is pressed are the same as in FIG.
[0017]
Note that the holding members 55, 56, and 57 may not be configured in the case 1 but may be provided in a jig or the like.
As described above, in the above embodiments, the optical head includes a prism in a part of the optical component, and a part of the joint surface of the prism is exposed so that the joint surface of the prism, that is, the reflective surface. Can be directly used for the high-precision positioning of the prism, so that a small and high-performance optical head device can be obtained.
[0018]
【The invention's effect】
As described above , according to the present invention , it is possible to obtain an optical head device that can easily ensure positional accuracy during prism assembly .
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an optical system in an embodiment of the present invention. FIG. 2 is an explanatory diagram of a standard prism configuration and an optical axis. FIG. FIG. 4 is an embodiment of the present invention. FIG. 5 is an embodiment of a prism having two reflecting surfaces parallel to each other and a part of the reflecting surface is exposed.
DESCRIPTION OF SYMBOLS 1 ... Case, 2a, 2b ... Laser light source, 9 ... Actuator, 10 ... Objective lens,
DESCRIPTION OF SYMBOLS 17 ... Wire support part, 20 ... Coil lens holder part, 22 ... Outer peripheral side wall, 23 ... Inner peripheral side wall, 24 ... Opening part, 25 ... Reinforcement side wall, 26 ... Notch, 27 ... Extraction port, 28 ... Signal input / output Conductive wire, 29 ... conductive wire, 30 ... gap, 44 ... triangular prism, 45 ... triangular prism, 50 ... triangular prism, 51 ... triangular prism, 52 ... triangular prism, 53 ... parallel plate, 54 ... triangular prism

Claims (1)

A first laser light source that emits a light beam of a first wavelength;
A second laser light source that emits a light beam having a second wavelength different from the first wavelength;
An optical component that guides an information recording medium by reflecting or transmitting a light beam emitted from the first laser light source or the second laser light source;
An objective lens for focusing the light beam on an information recording medium;
An actuator for driving the objective lens;
A photodetector for receiving a light beam reflected by the information recording medium;
A holding member for holding the optical component,
The optical component includes a first triangular prism, a second triangular prism, and a prism having two reflecting surfaces parallel to each other.
Of the two reflecting surfaces of the prism, the first reflecting surface closer to the laser light source transmits the light beam having the first wavelength and reflects the light beam having the second wavelength, thereby reflecting each light beam. The other second reflecting surface is a surface that reflects each light beam that has passed through the optical path and guides it to the information recording medium,
The first reflecting surface of the prism and the first triangular prism are bonded, and the second reflecting surface of the prism and the second triangular prism are bonded;
A part of the first reflecting surface of the prism is exposed, the exposed portion of the first reflecting surface is brought into contact with a holding member, and a surface that forms an angle of 45 degrees with the first reflecting surface is held. An optical head device characterized in that the optical component is positioned by being brought into contact with a member.

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