JPH0628733A - Optical head - Google Patents

Abstract

PURPOSE:To provide the optical head splitting a beam accurately by making an incident angle to a beam split face of an optical element almost constant. CONSTITUTION:An optical element 6 having a beam split face 8 being a curved face so as to make an incident angler to a reflected light almost constant is provided in a divergent or a convergent luminous flux of a reflected light on the way of an optical path leading a reflected light from a magneto-optical recording medium 12 to a photodetector to attain accurate beam split. Then a reproduction signal of information or the like is sufficiently obtained by each of photodetectors 4, 5, 9, 10 receiving a light beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for recording and reproducing information on an optical recording medium.

[0002]

2. Description of the Related Art A general structure of an optical head for a magneto-optical recording medium will be described below. As shown in FIGS. 10 and 11, the divergent beam linearly polarized from the semiconductor laser 50 is incident on the beam splitter 51 as P-polarized light and part of it is transmitted. The light beam that has passed through the beam splitter 51 is converted into a parallel beam by the collimator lens 52, and then the advancing direction of the light beam is changed by 90 ° by the rising mirror 53.
A recording surface of a magneto-optical recording medium (not shown) is irradiated by 4 as a light spot.

Information is recorded on the magneto-optical recording medium according to the direction of magnetization, and the irradiated light spot is reflected by the Kerr effect in which the polarization direction is rotated in the opposite direction according to the direction of magnetization. The reflected light (returned light) reflected by this magneto-optical recording medium passes through the objective lens 54, the rising mirror 53, and the collimator lens 52 and enters the beam splitter 51 again. The return light that has entered the beam splitter 51 has an S-polarized component because the plane of polarization is rotated by the Kerr effect. Most of the S-polarized component is reflected, and part of the P-polarized component is reflected.

Next, the return light reflected by the beam splitter 51 is transmitted through the concave lens 55, and its polarization direction is rotated by 45 ° by the ½ wavelength plate 56, and is guided to the polarization beam splitter 57. In the polarization beam splitter 57,
The plane beam splitting surface 57a splits the beam into a P-polarized component and an S-polarized component. The P-polarized component and the S-polarized component are respectively detected by the light receiving portions 58a and 58b of the photodetector 58, and the reproduction signal of information, the focus error signal, and the tracking error signal are detected based on the outputs thereof.
FIG. 11 is a plan view of the photodetector 58. Each of the light receiving portions 58a and 58b has a light receiving region divided into three bands. The detection principle of each of the above signals is well known and will not be described.

[0005]

However, in the above-described conventional optical head, the polarization beam splitter 57 to which the return light reflected by the magneto-optical recording medium is guided is arranged in the convergent light flux of the return light. There is. For this reason, the incident angle of the light beam incident on the flat beam splitting surface 57a is not constant, and the light beam cannot be accurately separated. As a result, there is a problem that the reproduction signal and the like obtained based on the output of the photodetector 58 deteriorates.

The present invention has been proposed to solve the above-mentioned problems, and it is possible to perform accurate beam splitting by making the angle of incidence on the beam splitting surface of the optical element substantially constant, and thus reproducing It is an object of the present invention to provide an optical head that can effectively prevent deterioration of signals and the like.

[0007]

In order to achieve the above object, the present invention provides an optical head which irradiates an optical recording medium with a light spot to record and reproduce information, and which reflects light from the optical recording medium. The optical head is provided with an optical element having a curved beam splitting surface in the divergent or convergent light flux of the reflected light in the middle of the optical path leading to the photodetector.

[0008]

As described above, since the optical element having the curved beam splitting surface is provided in the diverging or converging light beam of the reflected light, it is possible to accurately split the light beam, and thus to reproduce the information reproduction signal. It becomes possible to detect it sufficiently.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view showing a first embodiment of the present invention, and FIG. 2 is a plan view of a silicon substrate which is a part thereof. A semiconductor laser 2 is mounted on the silicon substrate 1, and a raising mirror 3 is mounted in the emission direction of the light beam from the semiconductor laser 2. The light beam emitted from the semiconductor laser 2 is linearly polarized, and its polarization direction is the X direction. Information is recorded in tracks on a magneto-optical recording medium, which will be described later, and the tracks are arranged so as to be parallel or perpendicular to the X direction.

An optical element 6 is arranged in the direction of reflection of the light beam by the raising mirror 3, and a hologram 7 is formed on the surface of the optical element 6 opposite to the semiconductor laser 2. There is. The hologram 7 has a lens action which makes the lattice direction form an angle of approximately 45 ° (the counterclockwise direction is positive) with respect to the X direction and gives the ± 1st order diffracted light a focal power in the opposite direction.

On the surface of the optical element 6 on the semiconductor laser 2 side, a curved beam splitting surface 8 is formed. The beam splitting surface 8 is coated with a dielectric multilayer film, and has a transmittance of almost 100% for a light beam with an incident angle of approximately 0 °, and a light beam with an incident angle of approximately 39 °. On the other hand, the P-polarized light reflectance is almost 0% and the S-polarized light reflectance is almost 100%. That is, the beam splitting surface 8 functions as a polarization beam splitter for a light beam having an incident angle of approximately 39 °. 3 is an explanatory view showing the P-polarized reflectance and the S-polarized reflectance of the beam splitting surface 8 with respect to the incident angle. Photodetectors 4 and 5 are arranged on the silicon substrate 1 at a distance. The photodetectors 4 and 5 are located in the direction of −45 ° with respect to the X direction and symmetrically with respect to the raising mirror 3. Further, the photodetector 4 is a light receiving region 4 formed by a straight line of −45 ° with respect to the X direction.
Similarly, the photodetector 5 is also divided into three bands a, 4b, and 4c, and the photodetector 5 is also a light receiving region 5a, 5 with a straight line of −45 ° with respect to the X direction.
It is divided into three bands b and 5c. Further, on the surface of the optical element 6 on which the hologram 7 is formed, photodetectors 9 and 10 are formed so as to sandwich the hologram 7.

Further, an objective lens 11 is arranged in the transmission direction of the light beam which passes through the hologram 7 from the raising mirror 3 side of the optical element 6, and converges the light beam to the magneto-optical recording medium 12. It is designed to illuminate a light spot.

The operation of this embodiment will be described below. While the light beam emitted from the semiconductor laser 2 is linearly polarized (the polarization direction is the X direction), it is incident on the rising mirror 3 and reflected in a direction substantially perpendicular to the silicon substrate 1. The reflected light beam is incident on the beam splitting surface 8 of the optical element 6. Since the incident angle at this time is near 0 °, most of the light beam passes through the beam splitting surface 8. The light beam that has passed through the beam splitting surface 8 passes through the hologram 7 as zero-order light, is converged by the objective lens 11, and then is irradiated onto the magneto-optical recording medium 12 as a light spot.

The emitted light from the semiconductor laser 2 is linearly polarized in the X direction, but since the Kerr effect occurs when it is irradiated onto the magneto-optical recording medium 12, the reflected light (returned light) is magneto-optical. The polarization direction is rotated from the X direction by the Kerr rotation angle according to the direction of the magnetization recorded on the recording medium 12. The return light reflected by the magneto-optical recording medium 12 again passes through the objective lens 11 to enter the optical element 6, and is separated into ± first-order diffracted lights by the hologram 7. At this time, since the lattice direction of the hologram 7 is approximately 45 ° with respect to the X direction, the diffraction direction of the ± 1st order diffracted light is −45 with respect to the X direction.
The direction is °. Next, the ± first-order diffracted lights separated by the hologram 7 are incident on the beam splitting surface 8, and the curved surface shape of the beam splitting surface 8 has an incident angle of approximately 39 with respect to all the rays of the ± first-order diffracted light. It is formed so that it becomes °. Therefore, in the return light that has entered the beam splitting surface 8, only the P-polarized component is transmitted and detected by the photodetectors 4 and 5, and most of the S-polarized component is reflected and formed on the optical element 6. The light is detected by the photodetectors 9 and 10.

Next, the light beam received by the photodetector will be described. Due to the lens action of the hologram 7, the + 1st-order diffracted light is focused before the photodetector 4, and the −1st-order diffracted light is focused behind the photodetector 5. When the objective lens 11 is at the in-focus position with respect to the magneto-optical recording medium 12, the size of the light spot on the photodetectors 4 and 5 is the same for the ± first-order diffracted light (states shown in FIGS. 1 and 2). ). On the other hand, the objective lens 11
When approaches to or away from the magneto-optical recording medium 12, the size of the light spot changes in the opposite direction due to ± first-order diffracted light.

Here, the outputs of the light receiving regions 4a to 4c and 5a to 5c of the photodetectors 4 and 5 shown in FIG. 2 are Ia to I, respectively.
c, Ja to Jc, the output of the photodetectors 9, 10 is Ka,
If Kb, the focus error signal (FE) is calculated by the beam size method.

## EQU1 ## Obtained as FE = (Ia-Ib + Ic)-(Ja-Jb + Jc). In addition, the tracking error signal (T
E) is a push-pull method

## EQU2 ## Obtained as TE = (Ia-Ic)-(Ja-Jc). Further, since the rotation of the polarization direction due to the Kerr effect with respect to the X direction changes the ratio of the P polarization component and the S polarization component of the light beam incident on the beam splitting surface 8, the magneto-optical signal S becomes

[Equation 3] S = (Ia + Ib + Ic + Ja + Jb + Jc)
Obtained as-(Ka + Kb).

FIGS. 4 to 6 show a second embodiment of the present invention, in which parts corresponding to those of the first embodiment are designated by the same reference numerals. A beam splitter 13 is provided in the emitting direction of the semiconductor laser 2, and a collimator lens 14 is provided in the traveling direction of the light beam passing through the beam splitter 13. A rising mirror 15 is provided in the traveling direction of the light beam that passes through the collimator lens 14, and the light beam whose traveling direction is changed by the objective lens 16 is recorded on a recording surface of a magneto-optical recording medium (not shown). It is designed to be illuminated as a light spot.

The return light reflected by the magneto-optical recording medium again passes through the objective lens 16, the raising mirror 15 and the collimator lens 14 and enters the beam splitter 13.
A ½ wavelength plate 17 and an optical element 6 are provided in the direction of the light beam reflected by the beam splitter 13, and a first photodetector 18 and a second light detector 18 are provided near the optical element 6. A detector 19 is provided.

As shown in the plan view of FIG. 5, the first photodetector 18 has four light receiving regions 18a-1a divided by a straight line parallel to the information track of the magneto-optical recording medium and a straight line perpendicular thereto.
It has 8d. In addition, the second photodetector 19 is similar to that shown in FIG.
As shown in the plan view in FIG. 2, two light receiving regions 19a, 19 divided by a straight line parallel to the information track of the magneto-optical recording medium are shown.
b.

A beam splitting surface 8 is formed on the return light incident surface side of the optical element 6. The beam splitting surface 8 is formed into a curved surface so that the incident angle is almost α with respect to all the rays of the returning light in the focused state, and the surface of the beam splitting surface 8 with respect to the ray with the incident angle α is A dielectric multilayer film is coated (not shown) so that the P-polarized light reflectance is approximately 0% and the S-polarized light reflectance is approximately 100%. Therefore, the beam splitting surface 8 functions as a polarization beam splitter for a light beam having an incident angle of approximately α.

The operation of this embodiment configured as described above will be described. First, the light beam emitted from the semiconductor laser 2 is incident on the beam splitter 13, and the light beam transmitted through the beam splitter 13 is collimator lens 14
After being converted into a parallel beam by, the moving direction is changed by 90 ° by the rising mirror 15, and the light is irradiated as a light spot on the recording surface of the magneto-optical recording medium (not shown) by the objective lens 16.

Information is recorded in the magneto-optical recording medium according to the direction of magnetization, and the irradiated light spot is reflected by the Kerr effect in which the polarization direction is rotated in the opposite direction according to the direction of magnetization. The return light reflected by the magneto-optical recording medium passes through the objective lens 16, the rising mirror 15 and the collimator lens 14 and enters the beam splitter 13. The return light that has entered the beam splitter 13 is reflected by the beam splitter 13, and the half-wave plate 17
Then, the polarization direction is rotated by 45 ° and enters the optical element 6. Here, the beam splitting surface 8 of the optical element 6 has an incident angle of approximately α with respect to all the returning light rays in the focused state.
Since the P-polarized light component of the return light incident on the beam splitting surface 8 is transmitted through the beam splitting surface 8 and then through the optical element 6 obliquely, Astigmatism is applied to the first photodetector 18
Detected in. Furthermore, most of the S-polarized light component of the return light that has entered the beam splitting surface 8 is reflected and
Is detected by the photodetector 19 of.

Therefore, if the outputs of the light receiving areas 18a to 18d of the first photodetector 18 are Ia to Id and the outputs of the light receiving areas 19a and 19b of the second photodetector 19 are Ja and Jb, respectively. , The magneto-optical signal S is

## EQU00004 ## Obtained as S = (Ia + Ib + Ic + Id)-(Ja + Jb). Further, the focus error signal FE is
By the astigmatism method,

## EQU5 ## FE = (Ia + Ic)-(Ib + Id) In addition, the tracking error signal TE
Is a push-pull method

## EQU6 ## Obtained as TE = (Ja-Jb).

FIG. 7 shows a third embodiment of the present invention. In this optical head, a semiconductor laser 22 and a raising mirror 23 are mounted on a silicon substrate 21, a light beam linearly polarized in the X direction is emitted from the semiconductor laser 22, and the light beam is raised by the raising mirror 23.
The optical element 24, the collimator lens 25, and the objective lens 26 irradiate the magneto-optical recording medium 27, and the return light reflected by the magneto-optical recording medium 27 passes through the objective lens 26, the collimator lens 25, and the optical element 24, and the silicon substrate. 21. The magneto-optical recording medium 27 is arranged so that the direction of its information track is inclined by 45 ° with respect to the X direction.

In addition to mounting the semiconductor laser 22 and the raising mirror 23 on the silicon substrate 21, the plane shown in FIG. 8 is received so as to receive the return light from the magneto-optical recording medium 27 which is incident through the optical element 24. As shown in the figure, X
The photodetector 28a is arranged so as to be substantially point-symmetric with respect to the rising mirror 23 on a straight line approximately ± 45 ° with respect to the direction.
To form ~ 28h. In addition, about -45 with respect to the X direction
The photodetectors 28b and 28d formed on the straight line of
Three light receiving regions 28b-1, 28b-2, 28b-3 and 28d- divided by straight lines parallel to the straight line, respectively.
1, 28d-2, 28d-3.

The optical element 24 is formed by attaching the first plastic molded lens 24a and the second plastic molded lens 24b to each other and rotationally symmetric with respect to the optical axis. First
Plastic molded lens 24a of collimator lens 2
As shown in the plan view of FIG. 9, two holograms 29a and 29b are integrally formed by dividing the surface on the 5 side by a straight line that passes through the optical axis and is inclined by 45 ° with respect to the X direction. The return light from the magneto-optical recording medium 27 is diffracted by 29a and 29b to obtain ± first-order diffracted light. Here, the hologram 29a is composed of linear gratings at equal intervals inclined by 45 ° with respect to the X direction, and the hologram 29b is −45 ° with respect to the X direction.
It is composed of a slanted linear grid at equal intervals. In addition,
The holograms 29a and 29b have the same lattice spacing.

On the bonding surface of the first plastic molded lens 24a and the second plastic molded lens 24b, the portion including the optical axis is the return light from the magneto-optical recording medium 27 diffracted by the holograms 29a and 29b. The curved surface is formed so that the incident angles are substantially equal to all the ± 1st-order diffracted light beams, and at least the curved surface portion is coated with a dielectric multilayer film to remove the curved surface portion. It acts as the beam splitting surface 30. In this embodiment, the beam splitting surface 30 has a transmittance of almost 100% for a light beam with an incident angle of about 0 ° and a P-polarized reflectance of a light beam with an incident angle of about 39 °. It is configured so that the reflectance of S-polarized light is approximately 0% and that of S-polarized light is approximately 100%.

Further, the first plastic molded lens 24
On the surface of a on the side of the collimator lens 25, a curved total reflection mirror surface 31 coated with aluminum so as to reflect the return light reflected by the beam splitting surface 30.
To form.

In this embodiment, when the objective lens 26 is in focus with respect to the magneto-optical recording medium 27, the + 1st order diffracted light and -1 of the returned light diffracted by the hologram 29a.
The silicon substrate 21 is placed on the optical axis of an optical system such as the optical element 24 so that the next-order diffracted light focuses on the surface of the silicon substrate 21 in the front and rear directions to form spots of the same size on the silicon substrate 21. For a plane orthogonal to
For example, the optical axis of the emission light of the semiconductor laser 22 and the optical axis of the optical system are set by setting the angle of the reflecting surface of the raising mirror 23 with respect to the surface of the silicon substrate 21 to 38 ° in accordance with the inclination. Try to match and.

The operation of this embodiment will be described below. The light beam emitted from the semiconductor laser 22 and linearly polarized in the X direction is reflected by the rising mirror 23, and then the optical element 2
It is incident on the beam splitting surface 30 of No. 4. Since the incident angle of the light beam at this time is near 0 °, most of the light beam passes through the beam splitting surface 30. The light beam that has passed through the beam splitting surface 30 passes through the holograms 29a and 29b as zero-order light, and then is converted into a parallel light flux by the collimator lens 25.
Further, it is converged by the objective lens 26, and the magneto-optical recording medium 2
7 is illuminated as a light spot.

The emitted light from the semiconductor laser 22 is linearly polarized in the X direction, but the return light reflected by the magneto-optical recording medium 27 has the magnetization recorded in the magneto-optical recording medium 27 by the Kerr effect. Depending on the direction, the polarization direction is rotated from the X direction by the Kerr rotation angle. This magneto-optical recording medium 2
The return light reflected by 7 again passes through the objective lens 26 and the collimator lens 25, and then the hologram 2 of the optical element 24.
It is incident on 9a and 29b and is diffracted respectively.

In the return light incident on the hologram 29a, the + 1st order diffracted light is diffracted in the direction of 135 ° with respect to the X direction, and the −1st order diffracted light is diffracted in the direction of −45 ° with respect to the X direction. Each is incident on the beam splitting surface 30. In the + 1st-order diffracted light incident on the beam splitting surface 30, most of its P-polarized component is transmitted through the beam splitting surface 30, and the optical element 24
And is incident on the photodetector 28b. Most of the S-polarized component is reflected by the beam splitting surface 30, then reflected by the total reflection mirror surface 31, emitted from the optical element 24, and incident on the photodetector 28f. To do.

Similarly, most of the P-polarized component of the -1st-order diffracted light from the hologram 29a that has entered the beam splitting surface 30 passes through the beam splitting surface 30 and is emitted from the optical element 24 to the photodetector 28d. Most of the S-polarized component that has been incident is reflected by the beam splitting surface 30, then reflected by the total reflection mirror surface 31 and emitted from the optical element 24.
Incident on.

In the return light incident on the hologram 29b, the + 1st order diffracted light is diffracted in the direction of 45 ° with respect to the X direction, and the −1st order diffracted light is diffracted in the direction of −135 ° with respect to the X direction. And enters each of the beam splitting surfaces 30. In the + 1st-order diffracted light that has entered the beam splitting surface 30, most of its P-polarized component passes through the beam-splitting surface 30, is emitted from the optical element 24 and enters the photodetector 28a, and most of the S-polarized component is beam-split. After being reflected by the surface 30, it is reflected by the total reflection mirror surface 31 and emitted from the optical element 24,
It is incident on the photodetector 28e.

Similarly, most of the P-polarized component of the −1st-order diffracted light from the hologram 29b which has entered the beam splitting surface 30 passes through the beam splitting surface 30 and is emitted from the optical element 24 to the photodetector 28c. Most of the incident S-polarized component is reflected by the beam splitting surface 30, is then reflected by the total reflection mirror surface 31, is emitted from the optical element 24, and is detected by the photodetector 28g.
Incident on.

Here, in the silicon substrate 21, when the magneto-optical recording medium 27 is in the focus position with respect to the objective lens 26, the + 1st order diffracted light of the return light diffracted by the hologram 29a is in front of the photodetector 28b. In addition, the -1st-order diffracted light is focused behind the photodetector 28d, respectively, so that the light spots of equal size are formed on the photodetectors 28b and 28d, so that the optical axis of the optical system such as the optical element 24 is formed. Since the magneto-optical recording medium 27 is displaced forward and backward from the in-focus position, it is arranged at an angle of 14 ° with respect to the plane orthogonal to the photodetector 28.
The spot sizes on b and 28d change in opposite directions.

Therefore, the light receiving areas 28b-1, 28b-2, 28b-3, 28d- of the photodetectors 28b, 28d are detected.
The outputs of ₁ , 28d-2 and 28d-3 are respectively Ib1,
_Assuming that I _b2 , I _b3 , I _d1 , I _d2 , and I _d3 , the focus error signal FE is obtained by the beam size method.

FE = (I _b1 −I _b2 + I _b3 ) − (I _d1 −I _d2 + I _d3 ).

The holograms 29a and 29b are
Since it is divided by a straight line parallel to the information track of the magneto-optical recording medium 27, the tracking error signal can be obtained by the push-pull method from the difference between the amount of light transmitted through the hologram 29a and the amount of light transmitted through the hologram 29b. That is, the photodetectors 28a, 28c, 28e, 28
f, 28 g, the output of 28h, respectively I _a, I _c, I
_{Assuming e} , I _f , I _g , and I _h , the tracking error signal TE is

[Equation 8] TE = (I _b1 + I _b2 + I _b3 + I _d1 + I _d2 + I _d3
+ I _f + I _h ) − (I _a + I _c + I _e + I _g ).

The return light reflected by the magneto-optical recording medium 27 has its polarization direction rotated from the X direction by the Kerr rotation angle,
The change in the polarization direction results in a change in the ratio of the P polarization component and the S polarization component with respect to the beam splitting surface 30. Therefore, the reproduction signal RF of information is generated by the holograms 29a and 2a.
Since the diffraction directions of 9b are orthogonal,

## _EQU9 ## RF = (I _b1 + I _b2 + I _b3 + I _d1 + I _d2 + I _d3
+ I _e + I _g )-(I _a + I _c + I _f + I _h ).

The third embodiment has the following advantages as compared with the first embodiment described above. 1) Since the collimator lens 25 is used, the objective lens 26 is made movable, and a separation optical system in which the remaining members are fixed becomes possible. 2) Since the holograms 29a and 29b are linear gratings at equal intervals, it is possible to make the diffraction angles of the + 1st order diffracted light and the −1st order diffracted light opposite in direction. As a result, it is not necessary to consider the difference between the + 1st order diffracted light and the −1st order diffracted light when determining the surface shape of the curved beam splitting surface 30. This is convenient in that the incident angles of both the + 1st-order diffracted light and the -1st-order diffracted light are maintained at approximately 39 °, and as a result, the quality of the reproduced signal of information can be improved. 3) The optical element 24 is replaced with the first plastic molding lens 24.
Since a and the second plastic molded lens 24b are bonded together, the light beam of the P-polarized component that passes through the beam splitting surface 30 is not refracted at the beam splitting surface 30. As a result, the aberration of the P-polarized light beam that passes through the optical element 24 can be reduced, and the quality of the focus error signal can be improved. 4) Since the S-polarized light beam reflected by the beam splitting surface 30 is reflected again by the total reflection mirror surface 31, all the photodetectors can be formed on one silicon substrate 21. . 5) Since the total reflection mirror surface 31 has a curved surface, the light beam reflected and diverged by the beam splitting surface 30 can be made into a converged beam again, thereby forming a small light spot on the silicon substrate 21. You can Therefore,
Photodetectors 28e, 28f, 28 for receiving this light beam
g and 28h can be reduced.

[0041]

As described above, according to the present invention, since the beam splitting surface has a curved surface such that the incident angle of the returning light is substantially constant, the reflected light from the magneto-optical recording medium diverges or converges. Even with light, the angle of incidence on the beam splitting surface can be made substantially constant, and accurate beam splitting is possible. As a result, it becomes possible to properly obtain the reproduction signal of information and the like by each photodetector that receives the light beam.

[Brief description of drawings]

FIG. 1 is a sectional view of an optical head according to a first embodiment of the present invention.

FIG. 2 is a plan view of the silicon substrate of the first embodiment.

FIG. 3 is an explanatory diagram of reflectance with respect to an incident angle in the first embodiment.

FIG. 4 is a sectional view of an optical head according to a second embodiment of the present invention.

FIG. 5 is a plan view of the first photodetector of the second embodiment.

FIG. 6 is a plan view of a second photodetector of the second embodiment.

FIG. 7 is a sectional view of an optical head according to a third embodiment of the present invention.

FIG. 8 is a plan view of a silicon substrate according to a third embodiment.

FIG. 9 is a plan view of a hologram according to a third embodiment.

FIG. 10 is a sectional view of an optical head according to a conventional example.

FIG. 11 is a plan view of a conventional photodetector.

[Explanation of symbols]

 1 Silicon Substrate 2 Semiconductor Laser 3 Raising Mirror 4 Photodetector 5 Photodetector 6 Optical Element 7 Hologram 8 Beam Splitting Surface 9 Photodetector 10 Photodetector 11 Objective Lens 12 Magneto-Optical Recording Medium 21 Silicon Substrate 22 Semiconductor Laser 23 Start-up mirror 24 Optical element 24a First plastic molded lens 24b Second plastic molded lens 25 Collimator lens 26 Objective lens 27 Magneto-optical recording medium 28a to 28h Photodetector 29a, 29b Hologram 30 Beam splitting surface 31 Total reflection mirror surface

Claims (1)

[Claims] 1. In an optical head for irradiating an optical spot on an optical recording medium to record and reproduce information, the reflected light diverges or converges in the middle of an optical path for guiding the reflected light from the optical recording medium to a photodetector. An optical head characterized in that an optical element having a curved beam splitting surface is provided in a light beam.