JPH1139692A - Beam splitter, composite optical element and optical pickup device using them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a beam splitter and a composite optical element independent of a polarizing film and to provide an optical pickup device attaining to make the device small and thin. SOLUTION: This optical pickup device 1 comprises at least first and second photodetectors 9a, 9b formed on a first semiconductor substrate 12, a semiconductor laser 2 having a perpendicular light emitting surface and a prism 4, in which a first wire grid 14a for splitting a light beam on a forward path from a light beam on a backward path and a second wire grid 14b for splitting the light beam in the backward path into the first and second photodetectors 9a, 9b are formed, and an objective lens 6 converging the light on a magnetooptical disk 10. In this case, both the first wire grid 14a and the second wire grid 14b are linear one-dimensional gratings formed on the principal plane of the prism 4, a polarizing component parallel with the forming direction of one-dimensional grating is almost reflected and a perpendicular polarizing component is almost transmitted through.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam splitter, a composite optical element, and an optical pickup device using the same. More specifically, the present invention relates to a forward light beam emitted from a semiconductor laser and a return light beam reflected and returned. The present invention relates to a beam splitter, a composite optical element, and an optical pickup device using the same, which are characterized by a spectroscopic means for separating.

[0002]

2. Description of the Related Art An optical pickup device for obtaining a magneto-optical signal of a magneto-optical disk, which is an example of an optical recording medium, and servo signals such as a focusing error signal and a tracking error signal, for example, astigmatism as a method of detecting a focusing error signal. The method using the three-spot method as a method for detecting the tracking error signal has a schematic configuration as shown in the schematic configuration diagram in FIG.

A forward light beam (dashed-dotted line in the figure) emitted from a semiconductor laser 2 as a light source is split into zero-order light and ± first-order light by a diffraction grating 3 and enters a prism 4.
In general, the prism 4 is configured by joining a pair of triangular prisms, and a BS (Beam) having a multilayer dielectric film formed by vapor deposition or sputtering on one of the joining surfaces.
(Split) film 11 is formed to constitute a beam splitter. Then, in the BS film 11, the forward light beam emitted from the semiconductor laser 2 and the return light beam reflected on the signal recording surface of the magneto-optical disk 10 are separated.

A forward light beam of a p-polarized light component separated and transmitted by the BS film 11 of the prism 4 is incident on a collimator lens 5 and converted into parallel light, for example, in the focusing direction of a biaxial actuator (not shown). Objective lens 6 held by a movable part that moves in the tracking direction
Thus, the light is focused on the signal recording surface of the magneto-optical disk 10.
The outgoing light beam condensed on the signal recording surface of the magneto-optical disk 10 is rotated by the magneto-optical Kerr effect due to the magnetization direction of the signal recording surface, so that the returning light beam containing the s-polarized light component is rotated. Then, the light passes through the objective lens 6 and the collimator lens 5 again, is incident on the prism 4, and
Are reflected by the Wollaston prism 7 (two-dot chain line in the figure). The returning light beam is split into a plurality of light beams by the Wollaston prism 7 and is incident on the multi-lens 8. Astigmatism for detecting a focus error signal is generated by the multi-lens 8 and condensed on the light receiving element 9. Is done. The light receiving element 9 is provided with a plurality of divided light receiving sections corresponding to the plurality of light beams split by the Wollaston prism 7, and the light receiving element 9 serves as a servo signal of a focusing error signal and a tracking error signal. A magneto-optical signal or the like is detected.

However, the p and s polarization directions of the BS film 11 in the prism 4 are uniquely determined by the incident direction of the outward light beam emitted from the semiconductor laser 2 to the BS film 11. That is, when no optical thin film is provided, it is always Tp> Ts. Therefore, even when an optical thin film is provided, it is difficult to design Ts to be larger than Tp. Therefore, they are usually arranged on the assumption that Tp> Ts. Further, in order to focus more light emitted from the semiconductor laser 2 on the magneto-optical disk 10, the transmittance in the outward path is increased, the carrier level of the magneto-optical reproduction signal is increased, and the CN ratio is further improved. In order to make the product of Rp and Rs as large as possible, the light emitted from the semiconductor laser 2 is configured to be p-polarized light. Therefore, the arrangement of the optical components in the optical pickup device 1 for the magneto-optical disk 10 is as follows.
The arrangement was roughly limited to the arrangement shown in FIG.

In recent years, as an optical pickup device 1 corresponding to a demand for downsizing of a read-only optical disk device or an optical disk device for both recording and reproduction, a semiconductor laser 2 as a light source on a semiconductor substrate and a focusing error signal Attention has been focused on a composite optical element (laser coupler type) integrally formed with a light receiving element 9 for detecting a servo signal of a tracking error signal, a magneto-optical signal, and the like. Magneto-optical disk 1 using this composite optical element
FIG. 11 shows an example of the optical pickup device 1 for
The schematic configuration will be described with reference to the schematic configuration diagram of FIG.

A second semiconductor substrate 13 is mounted on a first semiconductor substrate 12, and a semiconductor laser 2 as a light source is mounted on the second semiconductor substrate 13. On the side facing the light emitting surface of the semiconductor laser 2, a prism 4 having an inclined surface of approximately 45 degrees with respect to the surface of the first semiconductor substrate 12 on which the second semiconductor substrate 13 is mounted is provided with a phase plate 17. Is fixed to the first semiconductor substrate 12 with an adhesive or the like. A BS film 11 is formed on the inclined surface, and the outward light beam emitted from the semiconductor laser 2 is separated at the BS film 11 and reflected to the side where the magneto-optical disk 10 is present. Then, the light is condensed on the signal recording surface of the magneto-optical disk 10 by the objective lens 6 held by a movable portion that is movable in a focusing direction and a tracking direction of a biaxial actuator (not shown). The outgoing light beam condensed on the signal recording surface of the magneto-optical disk 10 is rotated by the magneto-optical Kerr effect due to the magnetization direction of the signal recording surface, so that its return plane light beam containing a p-polarized component is rotated. Then, the light again passes through the objective lens 6 and enters the prism 4, and the p-polarized light component is guided into the prism 4 in the BS film 11. The return light beam (two-dot chain line in the drawing) guided into the prism 4 is converted by the phase plate 17 by approximately 45 degrees in the polarization direction, and any one of the bonding surfaces of the phase plate 17 and the first semiconductor substrate 12 is converted. Tp100%, Rs100 formed on the surface
%, The p-polarized component is transmitted and the s-polarized component is reflected. The transmitted p-polarized light component is reflected by the high reflection film formed on the top surface of the prism 4 and enters the second light receiving element 9b. The pair of the first light receiving element 9a and the second light receiving element 9b detect a servo signal and a magneto-optical signal of a focusing error signal and a tracking error signal.

As a modification of the optical pickup device 1 using the composite optical element in the case described with reference to FIG. 11, the outward light beam emitted from the semiconductor laser 2 is transmitted through the BS film 11 and transmitted. The outgoing light beam may be reflected to a certain side of the magneto-optical disk 10 by a mirror having, for example, a 45-degree reflecting surface, and for example, a two-axis actuator may be disposed on the mirror to reduce the size and thickness. However, assuming that the transmittance of the p-polarized component in the BS film 11 is Tp, the reflectance is Rp, the transmittance of the s-polarized component is Ts, and the reflectance is Rs, normally Tp ≧
Ts or Rp ≦ Rs. Accordingly, the BS film 11 of the outward light beam emitted from the semiconductor laser 2 at the BS film 11
When the BS film 11 is formed such that the reflectivity Rs at the time is large, the transmittance Tp of the p-polarized light component and the transmittance Ts of the s-polarized light component of the return light beam reflected by the magneto-optical disk 10 at the BS film 11 are returned. Tp × Ts, that is, the carrier becomes small, and the detection level of the magneto-optical signal and the like detected by the first light receiving element 9a and the second light receiving element 9b becomes extremely small. The pickup device 1 has an inconvenient configuration.

That is, the prism 4 constituting the composite optical element
In the BS film 11, the polarization directions of p and s are uniquely determined by the incident direction of the outward light beam emitted from the semiconductor laser 2 to the BS film 11. Therefore, as shown in FIG. 11, the configuration of the optical pickup device 1 is such that a biaxial actuator is disposed on one side of the magneto-optical disk 10 on the composite optical element, thereby responding to the demand for downsizing. It was difficult to do.

[0010]

SUMMARY OF THE INVENTION The present invention provides a beam splitter and a composite optical element in which the arrangement of a semiconductor laser as a light source and a light receiving element for detecting a focusing error signal, a tracking error signal, a magneto-optical signal and the like is arbitrary. An object of the present invention is to provide an optical pickup device in which the arrangement of a laser and a light receiving element is arbitrary, and an optical pickup device that is smaller and thinner.

[0011]

In order to solve the above-mentioned problems, in the beam splitter according to the first aspect of the present invention, there is provided a beam splitter for separating a forward light beam emitted from a semiconductor laser and a return light beam reflected and returned. In a beam splitter having a beam splitter, the spectroscopic means includes Al or Au on one main surface of the prism.
Is a linear one-dimensional lattice formed of a metal such as the one-dimensional lattice. In this one-dimensional lattice, both the outward light beam and the return light beam reflected on the signal recording surface of the optical recording medium are reflected by the one-dimensional lattice. It is characterized in that a polarized light component parallel to the forming direction is substantially reflected, and a polarized light component perpendicular to the one-dimensional grating forming direction is almost transmitted. When the wavelengths of the forward light beam and the backward light beam are λ (nm), and the refractive index of the prism on which the one-dimensional grating is formed is n, the value of the grating formation pitch is λ / n (nm) or less. There is a feature.

According to a fourth aspect of the present invention, there is provided a composite optical device comprising: a pair of light receiving elements formed on at least a semiconductor substrate; a semiconductor laser formed on the semiconductor substrate and having a light emitting surface substantially perpendicular to the semiconductor substrate; A first spectral unit that is fixed on the light receiving element and separates a forward light beam emitted from the light emitting surface of the semiconductor laser and a return light beam reflected back from the light emitting surface of the semiconductor laser to a surface facing the light emitting surface of the semiconductor laser, A second splitting means for splitting the return light beam separated by the first splitting means into a pair of light receiving elements; and a beam splitter formed with a second splitting means. All means are A
1 and a linear one-dimensional lattice formed of a metal such as Au. In this one-dimensional lattice, the polarization components of the forward light beam and the backward light beam are parallel to the direction in which the one-dimensional lattice is formed. The polarization component is substantially reflected, and the polarization component perpendicular to the direction in which the one-dimensional grating is formed is substantially transmitted. Further, the second spectral unit may be constituted by a phase plate for rotating the polarization plane of the return light beam by 45 degrees, and an analyzer for separating the return light beam passing through the phase plate into transmitted light and reflected light. . When the wavelengths of the forward light beam and the backward light beam are λ (nm), and the refractive index of the prism on which the one-dimensional grating is formed is n, the value of the pitch of the one-dimensional grating is λ / n (nm). It is characterized by the following.

In the optical pickup device of the present invention, an objective lens for converging at least the forward light beam emitted from the semiconductor laser on the optical recording medium, and the return light reflected by the forward light beam and the optical recording medium and returning. In an optical pickup device having a beam splitter having a beam splitter for separating a beam and a light receiving element for receiving a return light beam reflected by the beam splitter, the beam splitter includes a metal such as Al or Au on one main surface of a prism. In this one-dimensional grating, in both the forward light beam and the backward light beam, the polarization component parallel to the direction in which the one-dimensional grating is formed is almost reflected, and the one-dimensional grating is formed. It is characterized in that a polarized light component perpendicular to the grating forming direction is substantially transmitted. When the wavelengths of the forward light beam and the return light beam are λ (nm), and the refractive index of the prism on which the one-dimensional grating is formed is n, the value of the pitch at which the one-dimensional grating is formed is λ.
/ N (nm) or less.

According to a ninth aspect of the present invention, there is provided an optical pickup device comprising: at least a pair of light receiving elements formed on a semiconductor substrate; a semiconductor laser formed on the semiconductor substrate and having a light emitting surface substantially perpendicular to the semiconductor substrate; A first light splitting means for separating a forward light beam emitted from the semiconductor laser and a return light beam reflected back from the semiconductor laser on a surface opposite to a light emitting surface of the semiconductor laser; A compound optical element having a beam splitter formed with second splitting means for splitting the return light beam separated by the splitting means into a pair of light receiving elements, and an objective lens for condensing the forward light beam on an optical recording medium In the optical pickup device having the first and second splitting means, both the first splitting means and the second splitting means are linear primary members formed of a metal such as Al or Au on one main surface of the prism. In this one-dimensional grating, the polarization components of the forward light beam and the return light beam are almost completely reflected in the polarization direction parallel to the one-dimensional lattice formation direction, and are reflected in the one-dimensional lattice formation direction. The vertical polarization component is substantially transmitted. Further, the second spectral unit may be constituted by a phase plate for rotating the polarization plane of the return light beam by 45 degrees, and an analyzer for separating the return light beam passing through the phase plate into transmitted light and reflected light. . When the wavelengths of the forward light beam and the backward light beam are λ (nm), and the refractive index of the prism on which the one-dimensional grating is formed is n,
It is characterized in that the value of the formation pitch of the one-dimensional lattice is λ / n (nm) or less.

The operation of the above-described means is such that the transmittance or reflectance for the polarization component of the outward light beam emitted from the semiconductor laser and the return light beam reflected and returned from the semiconductor laser in the beam splitter is used as a polarizer, and the main surface of the prism is used as a polarizer. Can be arbitrarily set according to the direction in which the linear one-dimensional lattice formed in the above-described manner, that is, the one-dimensional lattice of the wire grid is formed. Therefore, it is possible to provide an optical pickup device in which the arrangement of the semiconductor laser and the light receiving element is arranged so that, for example, optical adjustment can be easily performed. In addition, in the optical pickup device using the composite optical element, a configuration is possible in which the outward light beam emitted from the semiconductor laser is transmitted, and the return light beam reflected and returned is reflected and guided to the light receiving element. Can be achieved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a spectroscopic means for separating a polarization component of a forward light beam emitted from a semiconductor laser and a polarization component of a return light beam reflected on a signal recording surface of an optical recording medium. Instead of forming a beam splitter with a prism on which a BS film is formed as in the related art, a beam grid is formed on one main surface of the prism to form a beam splitter. That is, as shown in the schematic configuration diagram of the wire grid 14 in FIG. 1, the wavelength of the forward light beam and the backward light beam in the prism having the wire grid 14 formed on one main surface is λ (nm), the refractive index of the prism. When the value A of the pitch at which the grid 15 of the wire grid 14 is formed is set to λ / n (nm) or less, the polarization component parallel to the direction in which the grid 15 is formed is substantially reflected,
The polarization component perpendicular to the direction in which the grating 15 is formed is used as a polarizer by utilizing the property of being substantially transmitted. And
The ratio between the amount of transmitted light and the amount of reflected light can be arbitrarily set according to the angle at which the grid 15 is formed in the wire grid 14.

Hereinafter, as shown in FIG. 1, a polarization component parallel to the direction in which the grid 15 of the wire grid 14 formed on one principal surface of the prism is formed is referred to as a P polarization component, and
The polarized light component perpendicular to the direction of formation 5 is defined as an S-polarized light component, and specific embodiments of the present invention will be described with reference to FIGS. It is to be noted that the same reference numerals are given to components having the same structure as those shown in FIGS. 10 and 11 referred to in the related art in the drawings.

Embodiment 1 In this embodiment, a wire grid is formed on a prism of the present invention in an optical pickup device 1 having the same configuration as the case described with reference to FIG. 10 of the prior art. This is an example in which the configured beam splitter is applied. This will be described with reference to FIG. 2, which is a schematic configuration diagram of the optical pickup device 1.

First, the grating 15 of the first wire grid 14a formed on the prism 4 from the direction B in FIG.
An example in which the direction of formation is formed as shown in FIG. The grid 15 of the first wire grid 14a formed on the joint surface of the prism 4 is
If formed in the direction shown in FIG. 3, the S-polarized light component of the outward light beam (dashed line in the figure) emitted from the semiconductor laser 2 as the light source is almost transmitted. That is, the outward light beam emitted from the semiconductor laser 2 is split into zero-order light and ± first-order light by the diffraction grating 3 and enters the prism 4. The S-polarized light component of the outward light beam that has been separated and substantially transmitted by the first wire grid 14a formed on the prism 4 is incident on the collimator lens 5 and converted into parallel light, for example, a biaxial actuator (not shown). The light is condensed on the signal recording surface of the magneto-optical disk 10 by the objective lens 6 held by a movable part that is movable in the focusing direction and the tracking direction. The outgoing light beam condensed on the signal recording surface of the magneto-optical disk 10 is rotated by the magneto-optical Kerr effect due to the magnetization direction of the signal recording surface, so that its return plane light beam containing a P-polarized component is rotated. , Again the objective lens 6
And the collimator lens 5 and enter the prism 4, the P-polarized component is substantially reflected by the first wire grid 14 a and enters the Wollaston prism 7 (two-dot chain line in the figure). In the Wollaston prism 7, the return light beam is split into a plurality of light beams to form a multi lens 8.
And the multi-lens 8 generates astigmatism in the light beam for detecting a focus error signal,
The light is focused on the light receiving element 9. The light receiving element 9 is constituted by a plurality of light receiving sections divided corresponding to the plurality of light beams divided by the Wollaston prism 7, and thereby a servo signal of a focusing error signal and a tracking error signal, a magneto-optical signal, and the like. Is detected.

Next, although not shown, the arrangement of the semiconductor laser 2 and the light receiving element 9 in the optical pickup device 1 is opposite to the case shown in FIG. 2, that is, in FIG. The diffraction grating 3 and the semiconductor laser 2 are arranged on the optical axis on which the light-receiving element 8 and the light receiving element 9 are arranged, and the Wollaston prism 7, the multi-lens 8 and the A case where the light receiving element 9 is arranged will be described. in this case,
The formation direction of the grid 15 of the first wire grid 14a formed on the prism 4 from the direction B in FIG. 2 is formed as shown in FIG.

The P-polarized light component of the outward light beam emitted from the semiconductor laser 2 is split into zero-order light and ± first-order light by the diffraction grating 3 and enters the prism 4. The P-polarized light component of the outward light beam incident on the prism 4 is substantially reflected by the first wire grid 14a to a certain side of the magneto-optical disk 10 and is incident on the collimator lens 5 to be converted into parallel light. The light is focused on the signal recording surface.
The return light beam including the S-polarized component reflected by the signal recording surface of the magneto-optical disk 10 passes through the objective lens 6 and the collimator lens 5, and the S-polarized component passes through the first wire grid 14 a of the prism 4. The light is substantially transmitted to enter the Wollaston prism 7, transmitted through the multi-lens 8, and condensed on the light receiving element 9. Then, in the light receiving element 9, a servo signal and a magneto-optical signal such as a focusing error signal and a tracking error signal are detected.

As described above, the arrangement of the semiconductor laser 2 as the light source and the light receiving element 9 can be arbitrarily set by changing the forming direction of the grid 15 of the first wire grid 14a formed on the prism 4. it can. Therefore, it is possible to provide the optical pickup device 1 in which the arrangement of the semiconductor laser 2 and the light receiving element 9 is arbitrary.

Embodiment 2 This embodiment is an example in which the composite optical element of the present invention is applied to an optical pickup device 1. This will be described with reference to FIG. 5, which is a schematic configuration diagram of the optical pickup device 1. A second semiconductor substrate 13 is fixed to the first semiconductor substrate 12, and the semiconductor laser 2 as a light source is mounted on the second semiconductor substrate 13. On the side facing the light emitting surface of the semiconductor laser 2, an inclined surface of the first semiconductor substrate 12 that is inclined with respect to the surface to which the second semiconductor substrate 13 is fixed is used as a bonding surface, and a first triangular prism is formed. The prism 4a and the trapezoidal column-shaped second prism 4b are fixed to the first semiconductor substrate 12 with an adhesive or the like. A first wire grid is provided on at least a portion of the joining surface of one of the first prism 4a and the second prism 4b, which is irradiated with a forward light beam (dashed line in the drawing) emitted from the semiconductor laser 2. 1
4a (first spectral means) is formed. The direction in which the first wire grid 14a is formed as viewed from the direction C in FIG. 5 is the same as the case shown in FIG.
The S-polarized light component of the outward light beam emitted from the semiconductor laser 2 is almost transmitted, and is reflected to a certain side of the magneto-optical disk 10 by a mirror 16 having, for example, a 45-degree reflecting surface. Then, the light is condensed on the signal recording surface of the magneto-optical disk 10 by the objective lens 6 held in a movable portion movable in a focusing direction and a tracking direction of a biaxial actuator (not shown), for example. The outgoing light beam condensed on the signal recording surface of the magneto-optical disk 10 is rotated by the magneto-optical Kerr effect due to the magnetization direction of the signal recording surface, and its return plane light beam containing a P-polarized component is rotated. The light passes through the objective lens 6 again, is reflected by the mirror 16, enters the second prism 4b, and is substantially reflected by the first wire grid 14a. Return light beam reflected by the first wire grid 14a (two-dot chain line in the figure)
Is incident on a second wire grid 14b (second spectral means) formed on the joint surface of the second prism 4b with the first semiconductor substrate 12. This second wire grid 14
As shown in FIG. 6, the formation direction of the grating 15 viewed from the direction D in FIG. 5B is inclined such that the amount of transmission and reflection of the return light beam in the second wire grid 14b is substantially equal, for example. It is formed. The return light beam transmitted through the second wire grid 14b is incident on the first light receiving element 9a, and the return light beam reflected by the second wire grid 14b is reflected from the high light beam formed on the top surface of the second prism 4b. The light is reflected by the reflection film and enters the second light receiving element 9b. The pair of the first light receiving element 9a and the second light receiving element 9b detect a servo signal and a magneto-optical signal of a focusing error signal and a tracking error signal.

In this embodiment, as shown in FIG. 7, the composite optical element in the optical pickup device 1 in the case described with reference to FIG. 5 rotates the optical axis from the semiconductor laser 2 to the mirror 16. The optical pickup device 1 may be configured to be rotated by 180 degrees as a center. In this case, the formation direction of the grid 15 of the first wire grid 14a as viewed from the direction E in FIG. 7 is the same as the case illustrated in FIG. The formation direction of the grid 15 of the second wire grid 14b viewed from the direction F in FIG. 7 is the same as the case shown in FIG. Although not shown, the formation direction of the grid 15 of the first wire grid 14a viewed from the direction C in FIG. 5 and the formation direction of the grid 15 of the first wire grid 14a viewed from the direction E in FIG. In this case, the forward light beam emitted from the semiconductor laser 2 is reflected to a certain side of the magneto-optical disk 10 in the first wire grid 14a, as shown in FIG. An optical pickup device 1 similar to the case described above can also be configured.

Third Embodiment In the present embodiment, the second spectral means in the second embodiment is provided between the second prism and the semiconductor substrate on which the pair of light receiving elements are formed. It is composed of a phase plate that rotates the polarization direction by 45 degrees, and an analyzer that is provided on a joint surface of the phase plate with the semiconductor substrate and that transmits a P-polarized component and reflects an S-polarized component. Referring to FIG. 8, which is a schematic configuration diagram of the optical pickup device,
The schematic configuration will be described. The semiconductor laser 2
The forward light beam emitted from the optical disk is reflected by the magneto-optical disk 10 to become a forward light beam, and the return light beam is incident on the first wire grid 14a until the light beam is incident on the first wire grid 14a. Since it is the same as described above, duplicate description will be omitted.

The returning light beam including the P-polarized light component is substantially reflected by the first wire grid 14a. The return light beam (two-dot chain line in the drawing) reflected by the first wire grid 14a passes through the second prism 4b and enters the phase plate 17. In this phase plate 17, the polarization plane of the return light beam is rotated by 45 degrees. An analyzer 18 is formed on the surface of the phase plate 17 joined to the first semiconductor substrate 12, and the analyzer 18 transmits a P-polarized component and reflects an S-polarized component. Then, only the P-polarized light component enters the first light receiving element 9a. The return light beam reflected by the analyzer 18 passes through the phase plate 17 and again enters the second prism 4b.
b, the light is reflected by the high reflection film formed on the top surface, passes through the phase plate 17, and enters the second light receiving element 9b. Then, only the S-polarized light component enters the second light receiving element 9b. This pair of the first light receiving element 9a and the second light receiving element 9
With b, the servo signal and the magneto-optical signal of the focusing error signal and the tracking error signal are detected.

In this embodiment, as shown in FIG. 9, the composite optical element in the optical pickup device 1 in the case described with reference to FIG. 8 rotates the optical axis from the semiconductor laser 2 to the mirror 16. The optical pickup device 1 may be configured so as to be rotated by 180 degrees as the center. In this case, the formation direction of the grid 15 of the first wire grid 14a as viewed from the direction H in FIG. 9 is the same as the case shown in FIG. It is. Although not shown, the grid 15 of the first wire grid 14a viewed from the direction G in FIG.
Is formed as in the case shown in FIG. 4, the forward light beam emitted from the semiconductor laser 2 is reflected on the first wire grid 14a toward a certain side of the magneto-optical disk 10 by a conventional technique. An optical pickup device 1 similar to the case described with reference to FIG. 11 can also be configured.

[0028]

If the beam splitter is formed by forming a wire grid which is a one-dimensional grid on one principal surface of the prism, the arrangement of the semiconductor laser which is the light source and the light receiving element can be adjusted by the grid of the wire grid formed on the prism. It can be set arbitrarily depending on the forming direction. Therefore, in the optical pickup device using this, the arrangement of the semiconductor laser and the light receiving element can be made, for example, such that the optical adjustment can be easily performed, and the degree of freedom in designing the optical pickup device can be increased. it can. Further, according to the composite optical element of the present invention, the transmittance or reflectance for the polarization component of the forward light beam emitted from the semiconductor laser in the beam splitter and the return light beam reflected and returned is determined by the direction in which the grid of the wire grid is formed. Can be set arbitrarily. Further, according to the optical pickup device of the present invention, a configuration is possible in which the outward light beam emitted from the semiconductor laser is substantially transmitted, and the return light beam that is reflected and returned is almost reflected and guided to the light receiving element. Can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a wire grid of the present invention.

FIG. 2 is a schematic configuration diagram of an optical pickup device according to Embodiment 1 of the present invention.

FIG. 3 is a diagram illustrating a formation direction of a grid of a first wire grid according to the first embodiment, the second embodiment, and the third embodiment of the present invention.
9 is a schematic view as viewed from the direction of the arrow C, FIG. 7 is a view as viewed from the direction of the arrow G, FIG. 8 is a view as viewed from the direction of an arrow G, and FIG.

4 shows another example of the first wire grid forming direction in the first embodiment, the second embodiment, and the third embodiment of the present invention, and is schematically viewed from arrow B in FIG. 2; 5, a schematic view in the direction of arrow C in FIG. 5, a schematic view in the direction of arrow E in FIG. 7, a schematic view in the direction of arrow G in FIG. 8, and a schematic view H in FIG.
It is an arrow view.

FIG. 5 is a schematic configuration diagram of an optical pickup device according to a second embodiment of the present invention.

FIG. 6 is a schematic D view showing a formation direction of a grid of a second wire grid viewed from a D direction in FIG. 5;

FIG. 7 is a schematic configuration diagram of an optical pickup device of another example of Embodiment 2 of the present invention.

FIG. 8 is a schematic configuration diagram of an optical pickup device according to a third embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of another example of the optical pickup device according to the third embodiment of the present invention;

FIG. 10 is a schematic configuration diagram of a conventional optical pickup device.

FIG. 11 is a schematic configuration diagram of an optical pickup device using a conventional composite optical element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical pick-up apparatus, 2 ... Semiconductor laser, 3 ... Diffraction grating, 4 ... Prism, 4a ... First prism, 4b ...
Second prism, 5: collimator lens, 6: objective lens, 7: Wollaston prism, 8: multi-lens, 9
.. Light receiving element, 9a first light receiving element, 9b second light receiving element, 10 magneto-optical disk, 11 BS film, 12 first semiconductor substrate, 13 second semiconductor substrate, 14 wires Grid, 14a ... first wire grid, 14b ...
2nd wire grid, 15 grid, 16 mirror, 1
7 ... Phase plate, 18 ... Analyzer

Claims (12)

[Claims] 1. A beam splitter having a beam splitter for separating a forward light beam emitted from a semiconductor laser and a return light beam reflected and returned, wherein the light splitter is a linear beam splitter formed on one main surface of a prism. A one-dimensional grating, wherein both the forward light beam and the backward light beam substantially reflect a polarization component parallel to the one-dimensional grating forming direction and are perpendicular to the one-dimensional grating forming direction. A beam splitter characterized in that a polarization component is substantially transmitted. 2. The beam splitter according to claim 1, wherein the one-dimensional grating contains one of Al and Au. 3. When the wavelengths of the forward light beam and the return light beam are λ (nm) and the refractive index of the prism is n, the value of the pitch of the one-dimensional grating is λ / n (nm). The beam splitter according to claim 1, wherein: 4. A pair of light receiving elements formed on at least a semiconductor substrate, a semiconductor laser formed on the semiconductor substrate and having a light emitting surface substantially perpendicular to the semiconductor substrate, and fixed on the pair of light receiving elements. And a first spectral unit that separates a forward light beam emitted from the light emitting surface and a return light beam that is reflected back to the surface facing the light emitting surface, and is separated by the first spectral unit. In a composite optical element having a beam splitter formed with a second splitting unit that splits the return light beam into the pair of light receiving elements, the first splitting unit and the second splitting unit are both prisms. It is a linear one-dimensional grating formed on one main surface, and both the outward light beam and the return light beam are substantially reflected in the polarization component parallel to the direction in which the one-dimensional grating is formed. Composite optical element characterized in that the polarized component perpendicular to substantially transparent to the formation direction of the one-dimensional grating. 5. A phase plate for rotating a polarization plane of the return light beam by 45 degrees, and a detector for separating the return light beam transmitted through the phase plate into transmitted light and reflected light. The composite optical element according to claim 4, comprising a photon. 6. The composite optical element according to claim 4, wherein said one-dimensional grating contains any one of Al and Au. 7. When the wavelength of the forward light beam and the backward light beam is λ (nm) and the refractive index of the prism is n, the value of the pitch of the one-dimensional grating is λ / n (nm) or less. The composite optical element according to claim 4, wherein: 8. An objective lens for converging at least a forward light beam emitted from a semiconductor laser on an optical recording medium, and a spectral unit for separating the forward light beam and a return light beam reflected by the optical recording medium and returning. And a light receiving element that receives the return light beam reflected by the spectral unit. The spectral unit is a linear one-dimensional grating formed on one main surface of a prism. In each of the forward light beam and the return light beam, a polarized component parallel to the one-dimensional grating forming direction is substantially reflected, and a polarized component perpendicular to the one-dimensional grating forming direction is substantially transmitted. An optical pickup device. 9. A pair of light receiving elements formed at least on a semiconductor substrate, a semiconductor laser formed on the semiconductor substrate and having a light emitting surface substantially perpendicular to the semiconductor substrate, and fixed on the pair of light receiving elements. And a first beam splitting unit that separates a forward light beam emitted from the semiconductor laser from the semiconductor laser and a return light beam that is reflected back to the surface facing the light emitting surface, and is separated by the first light splitting unit. A composite optical element having a beam splitter formed with a second beam splitter for splitting the return light beam to the pair of light receiving elements; and an objective lens for condensing the forward light beam on an optical recording medium. In the optical pickup device, each of the first beam splitting unit and the second beam splitting unit is a linear one-dimensional grating formed on one main surface of a prism; In both of the return light beam and the return light beam, a polarization component parallel to the one-dimensional grating formation direction is substantially reflected, and a polarization component perpendicular to the one-dimensional grating formation direction is substantially transmitted. Optical pickup device. 10. A phase plate for rotating the polarization plane of the return light beam by 45 degrees, and a detector for separating the return light beam transmitted through the phase plate into transmitted light and reflected light. The optical pickup device according to claim 9, comprising a photon. 11. The optical pickup device according to claim 8, wherein the one-dimensional grating contains any one of Al and Au. 12. When the wavelengths of the forward light beam and the backward light beam are λ (nm) and the refractive index of the prism is n, the value of the formation pitch of the one-dimensional grating is λ / n (nm) or less. The optical pickup device according to claim 8, wherein: