JP2002123966A - Optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To integrate plural optical parts used for such an optical device as an optical head, which records and reproduces information to/from a recording medium by projecting an optical spot on such a disk-like recording medium as a CD, into a single optical part, and to provide an optical head in which cost is reduced and productivity is improved by reducing the number of parts by integrating in particular a PBS(polarizing beam splitter) prism, a wavelength plate, and a dichroic prism into a single integrated optical part. SOLUTION: The PBS prism, a 1/4 wavelength plate, and the dichroic prism are integrated to form a single integrated optical part 13 in the optical head provided with a first optical path where a first laser beam source 12, the PBS prism, the 1/4 wavelength plate, and the dichroic prism are located in series, and a second optical path composed of a second laser beam source 25 furnished with a hologram and the dichroic prism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an optical component used in an optical device such as an optical head for recording and reproducing information on a recording medium by projecting a light spot on a disk-shaped recording medium such as a CD. The present invention relates to an optical head in which a PBS prism, a wave plate, and a dichroic prism are integrated into a single composite optical component to reduce costs and improve productivity by reducing the number of components.

[0002]

2. Description of the Related Art An optical disk apparatus for recording and reproducing information on a disk-shaped recording medium such as a CD or a DVD using a laser beam projects a spot of a laser beam emitted from a laser light source onto a recording surface of the recording medium. And an optical head for performing recording and reproduction. FIG. 5 is a schematic configuration diagram showing an example of an optical head mounted on such an optical disk device. The optical head 1 includes a first laser diode (hereinafter, referred to as a first LD) 2 that generates a first laser beam L1 (for example, 630 nm, which is a wavelength for CD recording and reproduction), and a first laser diode. The first laser beam L1 emitted from the LD 2 is incident, and the PBS film 3a allows the PBS beam 3 to pass only the P-polarized component but not the S-polarized component to function as a polarizing beam splitter (PBS) prism 3 and a PBS prism 3. A quarter-wave plate 4 for rotating the polarization plane of the P-polarized component of the transmitted first laser light L1 by 90 degrees, and a dichroic prism 5 for transmitting the first laser light L1 transmitted through the quarter-wave plate 4 And a rising mirror 6 for reflecting the first laser beam L1 transmitted through the dichroic prism 5 toward the disk-shaped recording medium. First LD
The optical path from 2 to the disk-shaped recording medium constitutes a first optical path. The return light L 1 ′, which is the first laser light L 1 reflected by the disk, is reflected by the rising mirror 6, passes through the dichroic prism 5, and is further polarized by the quarter-wave plate 4 to 90 degrees. The light is rotated in the same direction to become S-polarized light, and the S-polarized light component is reflected by the PBS film 3 a of the PBS prism 3 and received by the light receiving element (PD) 7.
The PBS prism 3 has a configuration in which a PBS film 3a is sandwiched between inclined surfaces of two triangular prism glasses, and allows only the P-polarized light component to pass. The quarter-wave plate 4 is made of an anisotropic crystal plate such as quartz or a polymer resin film, and rotates the polarization plane of the input laser light by 90 degrees. The dichroic prism 5 includes a reflection separation film 5a between the two triangular prism glasses.
In this example, only the component having a wavelength of 780 nm is reflected.

Further, the optical head 1 further includes a second laser beam L2 (for example, a DVD recording / reproducing wavelength of 780 nm).
m) a second laser diode emitting light (second LD)
11, a dichroic prism 5 that reflects only a component having a wavelength of 780 nm in the second laser beam L2 by the reflection separation film 5a, and a rising mirror 6, which constitute a second optical path. The second LD 2 has a configuration in which a light receiving element having a hologram on a light receiving surface is juxtaposed. The return light L2 ′ of the second laser light L2 reflected on the recording surface of the disk-shaped recording medium is reflected on the rising mirror 6 and then on the reflection / separation film 5a of the dichroic prism 5 and is reflected on the second LD 11 Is incident on the light receiving element provided in.
Return light L1 ', L2' from the disc-shaped recording medium is incident on the light receiving element 7 and each light receiving surface of the second LD 11, respectively. As a result, an output signal (electric signal) corresponding to each return light L1 ', L2'. Are output from the light receiving element 7 and the second LD 11. These output signals are processed by a control circuit (not shown), and the information recorded on the disk-shaped recording medium is reproduced.

[0004]

The optical head having the above configuration has a large number of components in the first optical path.
It has disadvantages such as an increase in the number of manufacturing steps, an increase in parts cost, and an increase in size. In particular, when further miniaturization of the optical head is strongly demanded due to miniaturization of the device on which the optical head is mounted, there is a limit to the miniaturization of the optical head having the above configuration. Further, since the PBS prism 3, the quarter-wave plate 4, and the dichroic prism 5 are all made of glass, quartz, or the like, a part of the incident light or the outgoing light is reflected at the interface with air, causing a problem. . In order to prevent this reflected light, it is necessary to coat an anti-reflection film on the glass part and the crystal part which are the entrance and exit surfaces of each of the optical components 3, 4, 5 without fail. However, when mass-producing each optical component, incorporation of a process of coating an anti-reflection film on each input / output surface requires a large loss in equipment and procedures, resulting in increased costs and reduced productivity. Cause. Therefore, the problem to be solved by the present invention is:
A plurality of optical components used for an optical device such as an optical head for recording and reproducing information on the recording medium by projecting a light spot on a disc-shaped recording medium such as a CD are combined as much as possible into a single optical component. It is in. In particular, an object of the present invention is to provide an optical head in which the PBS prism, the wave plate, and the dichroic prism are integrated into a single composite optical component to reduce the number of components and reduce costs and improve productivity. Further, it is not necessary to apply a special anti-reflection film to the entrance / exit surface of the composite optical component, thereby making it possible to reduce the number of manufacturing steps and manufacturing costs.

[0005]

In order to solve the above-mentioned problems,
According to a first aspect of the present invention, writing and reading of information are performed by projecting spots of the first and second laser beams respectively emitted from the first and second laser light sources onto a recording surface of a rotating disk-shaped recording medium. A first optical path in which the first laser light source, a PBS prism, a quarter-wave plate, and a dichroic prism are sequentially arranged; the second laser light source with a hologram; and the dichroic prism Wherein the PBS prism, the quarter-wave plate, and the dichroic prism are integrated into a single composite optical component. The invention according to claim 2 includes a synthetic optical component having a configuration in which a PBS coat film is laminated and integrated on one surface of a glass substrate, and a 波長 wavelength plate and a dichroic coat film are sequentially laminated and integrated on the other surface of the glass substrate. It is characterized by having. According to a third aspect of the present invention, there is provided a synthetic optical component having a configuration in which a 波長 wavelength plate and a PBS coat film are sequentially laminated and integrated on one surface of a glass substrate, and a dichroic coat film is laminated and integrated on the other surface of the glass substrate. It is characterized by having. According to a fourth aspect of the present invention, a PBS coat film is laminated and integrated on one surface of the first glass substrate, and a 波長 wavelength plate, a second glass substrate, and a dichroic coat film are sequentially formed on the other surface of the first glass substrate. It is characterized by comprising a synthetic optical component having a laminated and integrated configuration. The invention according to claim 5 includes a synthetic optical component having a configuration in which a PBS coat film is laminated and integrated on one surface of the 波長 wavelength plate, and a dichroic coat film is laminated and integrated on the other surface of the 波長 wavelength plate. It is characterized by having. According to a sixth aspect of the present invention, there is provided a synthetic optical component having a configuration in which a PBS coat film, a quarter-wave plate, and a dichroic coat film are sequentially arranged at predetermined intervals inside a glass block.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 shows the first embodiment of the present invention.
14 is a schematic diagram showing a configuration of an optical head using the synthetic optical component according to the embodiment. The optical head 11 is provided with a first laser beam L1 (for example, a wavelength of 63 for CD recording / reproducing.
0 nm), and a first laser beam L1 emitted from a first LD (first laser light source) 12 and a first laser diode (hereinafter, referred to as a first LD) 12 generating P A composite optical component 13 that transmits only a polarized light component and emits light after rotating the polarization plane by 90 degrees, and a rising mirror 14 that reflects light emitted from the composite optical component 13 and guides the light to a disk-shaped recording medium. , Constitute a first optical path. The return light L1 'of the first laser light L1 reflected by the disc-shaped recording medium is reflected by the rising mirror 14, and the polarization plane is further rotated by 90 degrees by the synthetic optical component 13, so that the light receiving element (PD) 15 is received. The synthetic optical component 13 shown in FIG. 1 is of the standard type shown in FIG. 2A, and a PBS coat film is formed on one surface (an incident surface of the first laser beam L1) of a glass substrate 21 having a required thickness. 22
And a 一体化 wavelength plate 23 and a dichroic coating film (reflection / separation film) 24 are sequentially laminated and integrated on the other surface of the glass substrate (the emission surface of the first laser beam L1). I have. The PBS coat film 22 has a function of reflecting the S-polarized component in the first laser beam L1 and transmitting only the P-polarized component, and the quarter-wave plate 23 rotates the polarization plane of the P-polarized component by 90 degrees. The dichroic coat film 24 has a function of transmitting a laser beam having a wavelength of 630 nm and a function of reflecting a laser beam having a wavelength of 780 nm. The return light L 1 ′, which is the first laser light L 1 reflected by the disk, is reflected by the rising mirror 14, passes through the dichroic coat film 24, and further passes through the quarter-wave plate 23 to change the plane of polarization. Rotated 90 degrees in the same direction to become S-polarized light, P
The S-polarized light component is reflected by the BS coat film 22 and received by the light receiving element (PD) 15. The optical head further includes a second laser diode (second LD) 25 that emits a second laser beam L2 (for example, a DVD recording / reproducing wavelength of 780 nm), and a second LD (second LD). The second laser light L2 emitted from the (laser light source) 25
Dichroic coating film 24 that reflects only the laser beam L2
As a result, the light is guided to the rising mirror 14 and irradiated onto the disk-shaped recording medium. These constitute the second optical path.

The second LD 25 has a configuration in which a light receiving element having a hologram on a light receiving surface is juxtaposed. The return light L2 'of the second laser light L2 reflected on the recording surface of the disc-shaped recording medium is reflected by the rising mirror 14, then by the dichroic coating film 24, and is received by the second LD 25. Incident on. Synthetic optical component 1 having the above configuration
3 is a single component having the functions of the conventional PBS prism, quarter-wave plate, and dichroic prism.
The number of parts to be assembled can be reduced, the assembly structure can be simplified, the cost can be reduced, and the productivity can be improved, and the optical path can be further shortened to reduce the size of the optical head. Moreover, since the synthetic optical component 13 is of a plate type, the manufacturing process can be simplified. That is, the PBS coat film 22 is formed on each surface of the glass substrate 21,
Since it can be manufactured by laminating the 波長 wavelength plate 23 and the dichroic coat film 24, the number of manufacturing steps is greatly simplified. Furthermore, since the PBS coat film 22 is laminated on the incident surface of the glass substrate 21 and the quarter-wave plate 23 and the dichroic coat film 24 are laminated on the exit surface, the glass substrate surface does not come into contact with air, so It is no longer necessary to interpose an antireflection film at the interface between the glass substrate surface and air as in the prior art. In FIG. 1, the light receiving element 15 and the second LD 2
5 is adjacently arranged in a vertical positional relationship. This is because the light receiving element 15 receives the return light L1 ′ of the first laser light reflected 90 degrees by the PBS coat film 22 provided on the single composite optical component 13, and further the first light before the rising mirror 14. Since the second LD 25 is arranged at a position where the second laser light L2 can be emitted toward the dichroic coating film 24 so as to be orthogonal to the laser light L1, the light receiving element 1
5 and the second LD 25 are arranged close to each other. The distance between the light receiving element 15 and the second LD 25 can be variously adjusted by increasing or decreasing the thickness of the glass substrate 21 and the thickness of the wave plate 23. The relationship between the thickness of the glass substrate and the distance between the light receiving element 15 and the second LD 25 is as shown in FIG. 3, for example, as the glass substrate 21, an optical glass having a refractive index n of about 1.5 Is used, in order to make the distance between the light receiving element 15 and the second LD 25 4 mm, the thickness of the glass substrate 21 needs to be about 5 mm.

Next, FIG. 2B is a cross-sectional view showing a first modification of the plate-type composite optical component 13 shown in FIG. 2A. １ ／ wavelength plate 23 and PBS coat film 22 on one surface (incident surface)
Are sequentially laminated and integrated, and a dichroic coat film 24 is laminated and integrated on the other surface of the glass substrate 21. The synthetic optical component 13 according to the first modified example includes a glass substrate 2
Except for the configuration in which 1 is disposed between the quarter-wave plate 23 and the dichroic coat 24, the configuration is the same as the composite optical component in FIG. In other words, the PBS is provided on the incident surface side of the glass substrate 21.
The laminate of the coat film 22 and the quarter-wave plate 23 is integrated,
Further, a characteristic is that a dichroic coat 24 is laminated and integrated on the emission surface side. However, the glass substrate 21 is made of PBS
Coat film 22, quarter wave plate 23 and dichro coat 24
Such an arrangement is possible because it does not affect the characteristics even if it is arranged at any position between the positions. Therefore, as in the second modification shown in FIG. 2C, the two glass substrates 21A and 21A
B may be disposed between the PBS coat film 22 and the 波長 wavelength plate 23 and between the 波長 wavelength plate 23 and the dichro coat 24, respectively. Note that the synthetic optical component 13 according to the second modification of FIG. 2C has a configuration in which the quarter-wave plate 23 is sandwiched between the two glass substrates 21A and 21B. It is possible to use a resin wave plate other than an anisotropic crystal plate such as a plate. That is, in the composite optical component shown in FIGS.
Since the BS coat film 22 and the dichroic coat film 24 are formed by vapor deposition or the like, only a rigid anisotropic crystal plate can be used as the 波長 wavelength plate 23.
In other words, since it is difficult to deposit the PBS coat film 22 or the dichroic coat film 24 on the heat-sensitive resin wave plate, only an anisotropic crystal plate can be used in FIGS. 2 (a) and 2 (b). In the present invention, a quarter-wave plate 2 is provided between glass substrates.
3 is sandwiched, so that a wave plate made of resin can be used. Next, FIG. 2D is a cross-sectional view of a third modification of the synthetic optical component of the present invention.
And a dichroic coat film 24 is laminated and integrated on the other surface (emission surface) of the quarter-wave plate 23. When this type of composite optical component 13 is used, the distance between the light receiving element 15 and the second LD 25 can be reduced to about 100 μm. In other words, when the integration between the light receiving element 15 and the second LD 25 can be made close to about 100 μm, an ultra-thin plate-like composite of the type shown in FIG. This can be coped with by using the optical component 13, and the optical head can be significantly reduced in size.

Next, FIG. 4 is a view showing a configuration of an optical head using a composite optical component according to a second embodiment of the present invention. The optical head 31 includes a first laser diode (hereinafter, referred to as a first LD) 32 that generates a first laser beam L1 (for example, 630 nm which is a wavelength for CD recording and reproduction), and a first laser diode L1. A synthetic optical component 3 that receives the first laser light L1 emitted from the LD 32, transmits only the P-polarized component, and emits the light after rotating the polarization plane by 90 degrees.
3 and a rising mirror 34 that reflects light emitted from the combining optical component 33 and guides the reflected light to the disk-shaped recording medium, and these constitute a first optical path. The return light L1 'of the first laser light L1 reflected by the disk-shaped recording medium is reflected by the rising mirror 34, and the polarization plane is further rotated by 90 degrees by the synthetic optical component 33, and the light receiving element (PD) The light is received by 35. The composite optical component 33 shown in FIG. 4 has a configuration in which the PBS prism 3, the quarter-wave plate 4, and the dichroic prism 5 shown in FIG. That is,
The synthetic optical component 33 includes a PBS coat film 41 and a 、 wavelength plate 4 within a glass block 40 at a required interval.
2. It is characterized by a configuration having a configuration in which dichrocoat films 43 are sequentially arranged. The PBS coat film 41 is
Has a function of reflecting the S-polarized component in the laser light L1 and transmitting only the P-polarized component, and the quarter-wave plate 42 has a function of rotating the polarization plane of the P-polarized component by 90 degrees. The film 43 has a function of transmitting a laser beam having a wavelength of 630 nm while reflecting a laser beam having a wavelength of 780 nm. Further, the return light L1 ′, which is the first laser light L1 reflected by the disk, is reflected by the rising mirror 34, passes through the dichroic coat film 43, and further passes through the quarter-wave plate 42 to change the plane of polarization. S rotated by 90 degrees in the same direction
The light becomes polarized, and the S-polarized light component is reflected by the PBS coat film 41 and received by the light receiving element (PD) 35.

The optical head further includes a second laser diode (second LD) 36 for emitting a second laser beam L2 (for example, a DVD recording / reproducing wavelength of 780 nm). Emitted second laser light L
2 is guided to the rising mirror 34 by the dichroic coating film 43 that reflects only the second laser light L2, and is irradiated on the disk-shaped recording medium. These constitute the second optical path. The second LD 36 has a configuration in which a light receiving element having a hologram on a light receiving surface is juxtaposed. Second laser light L2 reflected on the recording surface of the disk-shaped recording medium
Is reflected by the rising mirror 34, then reflected by the dichroic coating film 43, and is incident on the light receiving element of the second LD 36.

The composite optical component 33 having the above-described configuration includes a conventional PBS prism, a １ ／ wavelength plate (１ ／ wavelength film),
And since it is a single component that also has the function of a dichroic prism, it can reduce the number of assembling parts, simplify the assembling structure, reduce costs and improve productivity, and further shorten the optical path. Thus, the optical head can be downsized. Moreover, since the composite optical component 33 has a configuration in which each film is incorporated in a block-shaped (cube, rectangular parallelepiped, etc., hexahedron) glass, the manufacturing process can be simplified. That is, the PBS coat film 41, the quarter-wave plate 42, and the four large-area flat glass plate base materials, respectively,
By cutting the glass block 40 at a predetermined angle after sandwiching and integrating the dichroic coat film 43, mass production can be performed by batch processing, so that the number of manufacturing steps is greatly simplified. The distance between the PD 35 and the second LD 36 can be variously set by adjusting the distance between the PBS coat film 41 and the dichroic coat film 43.

[0012]

As described above, according to the present invention, the following excellent effects can be obtained. The invention of claim 1 is
A first optical path in which a first laser light source, a PBS prism, a 波長 wavelength plate, and a dichroic prism are sequentially arranged; and a second optical path including the second laser light source with a hologram and the dichroic prism. In the optical head provided, the PBS prism, quarter-wave plate, and dichroic prism are integrated into a single composite optical component, reducing the number of assembly steps, simplifying the assembly structure, and reducing costs. In addition, the productivity can be improved, and the optical path can be further shortened to reduce the size of the optical head. The composite optical component according to any one of claims 2, 3, and 4, wherein each of the one or two glass substrates has a PB
Since it is a plate type in which the S coat film, the 波長 wavelength plate, and the dichro coat film are sequentially laminated and integrated in an appropriate order, the manufacturing process can be simplified. Since the synthetic optical component according to claim 5 has a configuration in which a PBS coat film, a 波長 wavelength plate, and a dichroic coat film are directly laminated and integrated without using a glass substrate, a reduction in thickness can be achieved. This can further contribute to miniaturization of the optical head. The synthetic optical component according to claim 6 has a configuration in which a PBS coat film, a 波長 wavelength plate, and a dichroic coat film are sequentially arranged at predetermined intervals inside a glass block. As described above, the number of steps for assembling the components can be reduced, the assembling structure can be simplified, the cost can be reduced, and the productivity can be improved. In addition, the optical path can be further shortened and the optical head can be downsized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical head using a synthetic optical component according to a first embodiment of the present invention.

FIGS. 2A, 2B, 2C, and 2D are cross-sectional views each showing a configuration of a synthetic optical component according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between a thickness of a glass substrate and a distance between a light receiving element and a second LD.

FIG. 4 is a diagram showing a configuration of an optical head using a synthetic optical component according to a second embodiment of the present invention.

FIG. 5 is a diagram showing an example of a conventional optical head.

[Explanation of symbols]

11 optical head, 12 first laser diode, 1
3 Synthetic optical parts, 14 rising mirror, 15 light receiving element (PD), 21 glass substrate, 22 PBS coat film,
23 quarter-wave plate, 24 dichroic coating film (reflective separation film), 25 second laser diode (second LD),
31 optical head, 32 first laser diode (first LD), 33 synthetic optical parts, 34 rising mirror, 35 light receiving element (PD), 40 glass block, 4
1 PBS coated film, 42 1/4 wavelength plate, 43 dichro coated film.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G02B 5/30 G02B 5/30

Claims (6)

[Claims] 1. A method for projecting spots of first and second laser beams respectively emitted from first and second laser light sources onto a recording surface of a rotating disk-shaped recording medium to write and write information.
An optical head for performing reading, comprising: a first optical path in which the first laser light source, a PBS prism, a 波長 wavelength plate, and a dichroic prism are sequentially arranged; the second laser light source with a hologram; and the dichroic An optical head comprising: a second optical path comprising a prism; wherein the PBS prism, a quarter-wave plate, and a dichroic prism are integrated into a single composite optical component. 2. A synthetic optical component having a structure in which a PBS coat film is laminated and integrated on one surface of a glass substrate, and a 波長 wavelength plate and a dichroic coat film are sequentially laminated and integrated on the other surface of the glass substrate. An optical head characterized in that: 3. A quarter-wave plate, PB on one surface of a glass substrate.
An optical head comprising a synthetic optical component having a configuration in which an S coat film is sequentially laminated and integrated, and a dichroic coat film is laminated and integrated on the other surface of the glass substrate. 4. A PBS coat film is laminated and integrated on one surface of the first glass substrate, and ＰＢＳ is coated on the other surface of the first glass substrate.
An optical head comprising a synthetic optical component having a configuration in which a wavelength plate, a second glass substrate, and a dichroic coating film are sequentially laminated and integrated. 5. A composite optical component having a structure in which a PBS coat film is laminated and integrated on one surface of the quarter wavelength plate and a dichroic coat film is laminated and integrated on the other surface of the quarter wavelength plate. An optical head characterized in that: 6. An optical head comprising a synthetic optical component having a configuration in which a PBS coat film, a quarter-wave plate, and a dichroic coat film are sequentially arranged at predetermined intervals inside a glass block.