JPH07110959A - Optical detection element and optical pickup device using the element - Google Patents

Abstract

PURPOSE:To obtain an optical detection element which enhances the intensity of individual signals such as a tracking-error signal, a magneto-optical signal and a focusing-error signal and to obtain an optical pickup device using it. CONSTITUTION:An optical detection element 23 is provided with a first light- receiving face 25 which receives three reflected light beams R1, R11, R21 corresponding to + first-order light by a diffraction grating and with a second light- receiving face 26 which receives three reflected light beams R2, R12, R22 corresponding to - first-order light by the diffraction grating. When the difference between an optical detection signal from the first light-receiving face 25 and an optical detection signal from the second light-receiving signal is found, a tracking-error signal can be generated. Since the respective three reflected light beams (R1, R11, R21), (R2, R12, R22) are incident on the first and second light-receiving faces 25, 26, the signal intensity of the tracking-error signal is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photo-detecting element which is applied to a magneto-optical recording / reproducing apparatus or the like and writes or reads information to or from a recording medium such as a magneto-optical disk, and an optical pickup device using the same.

[0002]

2. Description of the Related Art In order to write or read information to or from a recording medium by an optical pickup device, it is necessary to accurately position an objective lens in both the focus direction and the track direction. When the recording medium is a magneto-optical disk, the Kerr rotation of the plane of polarization is read as a magneto-optical signal, which is weaker than the pit signal of the compact disk.

On the other hand, with the recent miniaturization of magneto-optical disks, miniaturization of optical pickup devices has been required.
Therefore, by using a diffraction grating and a 3-beam Wollaston Prism, the information (magneto-optical signal) recorded on the magneto-optical disk from the reflected light from the magneto-optical disk and the positional deviation in the focus direction ( There is known an optical pickup device in which a focus error signal indicating defocus) and a tracking error signal indicating position deviation in the track direction can be taken out by a single photodetector (for example, Japanese Patent Laid-Open No. 4-157647). .

According to this conventional optical pickup device, a recording layer of a magneto-optical disk is irradiated with a light beam which is separated into three light beams of 0th order light and ± 1st order light by a diffraction grating, as shown in FIG.
As shown, each reflected light beam R ₀ , R ₁ , from the recording layer
R ₂ is divided into three by the three-beam Wollaston prism 1, and a total of nine reflected light beams R ₀ , R ₁ , R
₂ , R ₁₀ , R ₁₁ , R ₁₂ , R ₂₀ , R ₂₁ , R ₂₂ are generated,
Five of the reflected light beams R ₀ , R ₁ , R ₂ , R ₁₀ ,
R ₂₀ is detected by a single photodetector element (see FIG. 14) 2 and the detection result is used to generate a focus error signal, a tracking error signal and a magneto-optical signal.

Therefore, as shown in FIG. 14, the conventional photodetector 2 has a 0th-order light separated by a diffraction grating and ± 1.
A plurality of light receiving surfaces for respectively receiving reflected light beams R ₀ , R ₁ , R ₂ corresponding to the next light and reflected light beams R ₁₀ , R ₂₀ whose traveling directions are separated as magneto-optical signals by the three-beam Wollaston prism 1. 3 to 7.

As described above, the conventional photodetector 2 has a structure that does not use the reflected light beams R ₁₁ , R ₁₂ , R ₂₁ , and R ₂₂ at the four corners, and it is necessary to increase the intensity of the tracking error signal. In addition, the light quantity ratio of the 0th order light to the ± 1st order light by the diffraction grating is kept relatively low at about 4 to 8. Also,
A conventional three-beam Wollaston prism is used for a basic split light amount ratio, that is, an ordinary ray: an ordinary ray and an extraordinary ray are combined: an extraordinary ray of 25:50:25 is often used. It is a half of the light amount of the combined ordinary and extraordinary rays, and the magneto-optical signal (ordinary ray intensity-extraordinary ray intensity) is quite weak.

[0007]

However, in the conventional optical pickup device, the reflected light beams R _{11 at} the four corners,
Since R ₁₂ , R ₂₁ , and R ₂₂ are not used, there is a problem that the tracking error signal and the intensity of the magneto-optical signal are weak accordingly. Further, since the light quantity ratio of the 0th-order light to the ± 1st-order light by the diffraction grating is not high, there is a problem that a focus error signal and a magneto-optical signal having large signal strength cannot be obtained. Further, the basic split light amount ratio by the conventional three-beam Wollaston prism has a strong central beam intensity ratio,
Since the intensity on both sides is half that of the central beam, there was a problem that a large magneto-optical signal could not be obtained.

Therefore, the present invention has been made in view of the above circumstances, and a photodetecting element for improving the intensity of each of a tracking error signal, a magneto-optical signal, and a focus error signal, and an optical pickup using the same. The purpose is to provide a device.

[0009]

In order to achieve the above object, the photodetector according to claim 1 records a light beam separated by a diffraction grating into at least three light components of 0th order light and ± 1st order light. At least three reflected light beams corresponding to the + 1st-order light in a photodetector that receives a reflected light beam that is emitted from a recording medium and is separated into at least three reflected light beams by a Wollaston prism. It has a first light receiving surface for receiving the beam and a second light receiving surface for receiving at least three reflected light beams corresponding to the minus first-order light.

In the optical pickup device according to the second aspect, a light beam generating source for generating a light beam and a light beam from the light beam generating source are divided into at least zero-order light and ± first-order light. A diffraction grating to be separated, an objective lens that collects and irradiates a light beam separated by the diffraction grating onto a recording portion of a recording medium and receives each reflected light beam from the recording medium, and an objective lens received by the objective lens. A Wollaston prism that separates each reflected light beam into at least three, and a photodetector that receives at least nine reflected light beams from the Wollaston prism, and at least three reflections corresponding to the + 1st order light. A first light receiving surface for receiving a light beam, a second light receiving surface for receiving at least three reflected light beams corresponding to the −1st order light, and the 0th order light. Of the three reflected light beams, at least the third reflected light beam formed by a plurality of divided light receiving surfaces for splitting the central reflected light beam and receiving the divided light beams is provided on both sides of at least three reflected light beams corresponding to the 0th order light. It is characterized in that it has a photodetector having a pair of fourth light-receiving surfaces for receiving the reflected light beams independently of each other, and a lens driving means for adjusting the position of the objective lens.

In the optical pickup device according to a third aspect of the invention, the light quantity ratio of the 0th order light to the ± 1st order light by the diffraction grating is 8.5 to 15.

Further, in the Wollaston prism which separates into an ordinary ray, a ray obtained by combining the ordinary ray and the extraordinary ray, and an extraordinary ray, the optical pickup device according to the fourth aspect is characterized in that Of the total amount of light is 30 to 45%.

[0013]

According to the photodetector of the first aspect, by taking the difference between the photodetection signal from the first light-receiving surface and the photodetection signal from the second light-receiving surface, for example, a tracking error signal is detected. Can be generated. Since at least three reflected light beams are respectively incident on the first and second light receiving surfaces, the tracking error signal has a large signal intensity.

According to the optical pickup device of the second aspect, as in the first aspect, the difference between the light detection signal from the first light receiving surface and the light detection signal from the second light receiving surface is obtained. Thereby, for example, a tracking error signal can be generated, and at least three reflected light beams are respectively incident on the first and second light receiving surfaces, so that the tracking error signal has a large signal intensity. Also,
For example, a focus error signal can be generated from the light detection signal from each divided light receiving surface of the third light receiving surface.
Further, by taking the difference between the photo detection signals from the pair of fourth light receiving surfaces, for example, a magneto-optical signal can be generated.

According to the optical pickup device of the third aspect, the signal intensity of the magneto-optical signal and the focus error signal is set by setting the light quantity ratio of the 0th order light to the ± 1st order light by the diffraction grating to be 8.5 or more. Although it can be increased, if the light quantity ratio exceeds 15, the signal strength of the tracking error signal becomes too small. Therefore, by setting the light quantity ratio of the 0th-order light to the ± 1st-order light by the diffraction grating to be 8.5 to 15, the signals of the magneto-optical signal and the focus error signal can be obtained without making the signal intensity of the tracking error signal too small. The strength can be increased.

According to the optical pickup device of the fourth aspect, in the Wollaston prism that separates into an ordinary ray, a ray composed of the ordinary ray and the extraordinary ray, and the extraordinary ray, the ordinary ray and the extraordinary ray A large magneto-optical signal can be obtained by setting the ratio to the total amount of light of 30 to 45%, and a large tracking error signal can also be obtained by using the photodetector according to the first aspect. If the amount of ordinary and extraordinary rays exceeds 45% of the total amount of light, the focus error signal becomes too weak.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the optical pickup device of the present invention, and FIG. 2 is a perspective view showing the optical system thereof.

The optical pickup device 10 of this embodiment is
As shown in FIG. 1, a lens driving unit (lens driving unit) 12 that adjusts a position of an objective lens 11 described later in a focus direction Z and a track direction X, and an optical system block 13 in which a plurality of optical components and the like are incorporated. have.

As shown in FIG. 2, the optical system block 13 irradiates a semiconductor laser (light beam generation source) 14 for generating a laser light beam B and three laser light beams B generated by the semiconductor laser 14 for irradiation. Light beams B ₀ , B ₁ ,
A diffraction grating 15 for separating the B _2, a collimator lens 16 for collimating the beam of the separated three irradiation light beam B _0, B _1, B ₂ by the diffraction grating 15, an objective lens 1
A beam splitter (BS) that changes the optical axis direction of a reflected light beam R (R ₀ , R ₁ , R ₂ ) from one side
17, and the irradiation light beams B ₀ , B ₁ , and B ₂ from the semiconductor laser 14 side that have passed through the beam splitter 17 are condensed and irradiated onto a recording layer (recording portion) of, for example, a magneto-optical disk D serving as a recording medium. The optical axis direction is changed by the objective lens 11 which receives each of the reflected light beams R ₀ , R ₁ and R ₂ from the recording layer of the magneto-optical disk D and the beam splitter 17 which the objective lens 11 receives. The reflected light beams R ₀ , R ₁ , R ₂ are each divided into three, and a total of 9 reflected light beams R ′ (R ₀ , R ₁ , R ₂ , R _{2
10, R 11, R 12,} R 20, R 21, 3 -beam Wollaston prism for generating _{R 22) (3-Beam Wollaston} Prism)
18 and a reflection mirror 19 for reflecting the reflected light beam R ′
A condenser lens 20 for condensing the reflected light beam R'reflected by the reflection mirror 19, a concave lens 21 for reducing the convergence angle of the incident reflected light beam R ', and a reflected light beam R'. A cylindrical lens 22 that causes astigmatism, a photodetector 23 that detects a reflected light beam R ′ that has passed through the cylindrical lens 22, and the like are built in.

The diffraction grating 15 is, as shown in FIG.
At least the 0th-order light irradiation light beam B ₀ and the + _1st- order light irradiation light beam B ₁ − so that the incident beam B is spread out in a fan shape around the optical axis of the beam B by the diffraction phenomenon.
The irradiation light beam B ₂ of the primary light is separated into three light beams. Of these three irradiation light beams B ₀ , B ₁ , and B ₂ , the irradiation light beams B ₁ and B _{2 on} both outer sides are used to generate a so-called tracking error signal.

The three-beam Wollaston prism 18
As shown in FIG. 4, a pair of triangular prisms 18a and 18b made of a uniaxial crystal such as quartz, rutile or calcite and having a substantially right triangle shape in cross section are formed into a rectangular parallelepiped shape by joining their inclined surfaces 18c. It is composed. Also,
The three-beam Wollaston prism 18 is arranged such that the crystal axis directions of the triangular prisms 18a and 18b are orthogonal to the optical axis of the reflected light beam R, and are linked to each other at an angle of approximately 45 degrees. It is configured. When the reflected light beams R ₀ , R ₁ and R ₂ incident on the three-beam Wollaston prism 18 are transmitted through the inclined surfaces 18c of the triangular prisms 18a and 18b, they are refracted in different directions depending on the polarization direction, resulting in abnormalities. First beam R ₁₀ , R which is a light beam
₁₁ , R ₁₂ , second beams R ₂₀ , R ₂₁ , R ₂₂ which are ordinary rays
And the ordinary beams and the extraordinary rays are separated into third beams R ₀ , R ₁ and R ₂ .

As shown in FIG. 5, the photo-detecting element 23 is a reflected light beam corresponding to + 1st order light, and three reflected light beams R ₁ and R ₁ whose traveling directions are separated by the Wollaston prism 18. The first light receiving surface 25 for receiving ₁₁ and R _21, and the reflected light beam corresponding to the −1st order light, whose traveling directions are separated by the Wollaston prism 18
A second light receiving surface 26 for receiving the two reflected light beams R ₂ , R ₁₂ , and R _22, and a reflected light beam corresponding to the 0th order light,
Of the three reflected light beams R ₀ , R ₁₀ , and R ₂₀ whose traveling directions are separated by the Wollaston prism 18, a plurality of first to fourth divided light-receiving surfaces for dividing and receiving the central reflected light beam R ₀ 24a, 24b, 24c, and third light-receiving surface 24 consisting 24d, 0 3 one reflective light corresponding to the primary light beam R _0, R _10, on both sides of the reflected light beam R ₁₀ of R _20, R
A pair of fourth light-receiving surfaces 2 for individually receiving ₂₀
7 and 28 are provided. Further, each of the light receiving surfaces 24a to 2
4d, 25, 26, 27 and 28 are configured to output a photodetection signal corresponding to the light intensity of the received reflected light beam to a signal processing unit 30 described later via a lead wire (not shown).

FIG. 6 is a block diagram showing the control system of this embodiment.

The optical pickup device 10 of this embodiment is
As shown in the figure, a control section (control means) 29 for controlling each section of the apparatus 10 is provided, the lens driving section 12 is connected to the control section 29, and each of the light receiving surfaces 24 to 26 is connected to a signal processing section. It is connected through 30.

The signal processing section 30 generates a tracking error signal and a focus error signal based on the light detection signals sent from the respective light receiving surfaces 24 to 26, outputs them to the control section 29, and outputs a fourth light receiving signal. A magneto-optical signal is generated based on the photodetection signals sent from the surfaces 27 and 28, and is output to the output buffer 31.

When the tracking error signal is generated by the signal processing unit 30, the reflected light beams R ₁ , R ₁₁ ,
The difference between the light detection signal output from the first light receiving surface 25 that receives R ₂₁ and the light detection signal output from the second light receiving surface 26 that receives the reflected light beams R ₂ , R ₁₂ , and R ₂₂ is calculated. As a result, a tracking error signal is generated.

When the focus error signal is generated, the value of the focus error signal is Fe and the value of the light detection signal from the first to fourth divided light receiving surfaces 24a to 24d is Ra, respectively, according to the astigmatism method. , Rb, Rc, Rd, the following formula (1) Fe = (Ra + Rc)-(Rb + Rd) (1) is obtained.

That is, as shown in FIG.
When the disk D is at the focal position (solid line), the reflected light from is focused on the Z ₀ point in the z-axis direction perpendicular to the paper surface,
In the x direction parallel to the paper surface, since the focal point is at the point X ₀ , the beam cross section becomes a perfect circle at the point P. Therefore, at the position of point P, 4
By placing the divided first to fourth divided light receiving surfaces 24a to 24d, a spot (R) of a perfect circle as shown in FIG.
_{Since 0} ) is obtained, the value Fe of the focus error signal becomes 0 in the case of focusing.

When the objective lens 11 approaches the disk D (dotted line), the focal point moves to the Z'point and the X'point, and the beam cross section at the P point becomes thick in the z direction and thin in the x direction. As shown in FIG. 9, the upper spot (R ₀ ) becomes an ellipse to the upper right when taking the z and x directions, and the value Fe of the focus error signal has a positive value.

When the objective lens 11 moves away from the disc D (dotted line), the spot (R ₀ ) on the light receiving surface 24 for focusing becomes an ellipse that descends to the right as shown in FIG. Fe has a negative value.

In this way, by calculating the above equation (1), it is possible to judge whether the focus is in focus, is too close, or is too far away. Further, as shown in FIG. It is also possible to recognize the amount of defocus depending on the value Fe.

When a magneto-optical signal is generated by the signal processing unit 30, the reflected light beam R corresponding to the 0th order light is used.
A pair of fourth light receiving surfaces 27, 2 which independently received the reflected light beams R ₁₀ , R ₂₀ on both sides of ₀ , R ₁₀ , R ₂₀ respectively.
A magneto-optical signal is generated by taking the difference between the two optical detection signals output from the optical disc 8.

The lens driving unit 12 is provided with a focusing coil and a tracking coil, and under the control of the control unit 29, current is supplied to these coils to generate a driving force in the coils to move the objective lens 11 in the focusing direction. The position is adjusted by following Z and the track direction X.

The control unit 29 controls the lens driving unit 12 based on the tracking error signal and the focus error signal output from the signal processing unit 30 to control the position of the objective lens 21 in the focus direction and the track direction. It is something to do.

Next, the operation of this embodiment will be described with reference to FIG.

The laser light beam B generated from the semiconductor laser 14 is separated into the _{first to} third irradiation light beams B ₀ , B ₁ and B ₂ by the diffraction grating 15 and is made into a parallel beam by the collimator lens 16. It passes through the beam splitter 17 and enters the objective lens 11.

The objective lens 11 focuses the incident irradiation light beams B ₀ , B ₁ and B ₂ on the recording layer of the magneto-optical disk D and irradiates them.

By the way, the recording layer of the magneto-optical disk D is
The so-called vertical magnetization is formed so that the magnetization direction is changed for each micro area according to the written information signal. The reflected light beams R of the irradiation light beams B ₀ , B ₁ , and B ₂ focused and irradiated on this recording layer are shown in FIG. 12 by the so-called Kerr effect according to the magnetization direction of this recording layer. Thus, the polarization direction is changed.

That is, for example, the reflected light beam R from the region where the magnetization direction of the recording layer is in the initial state (the region indicated by the upward arrow in the figure), in other words, the region where the recorded information is "0". Is rotated by + θ _{k with} respect to the polarization directions of the irradiation light beams B ₀ , B ₁ and B ₂ incident on the recording layer. Further, the polarization of the reflected light beam R from a region in which the magnetization direction of the recording layer is inverted with respect to the initial state (a region indicated by a downward arrow in the figure), in other words, a region where the recording information is "1". The direction is rotated by −θ _{k with} respect to the polarization direction of the irradiation light beams B ₀ , B ₁ and B ₂ incident on the recording layer.

In this way, the irradiation light beams B ₀ , B ₁ and B ₂ incident on the recording layer of the magneto-optical disk D are reflected light beams whose polarization directions are rotated according to the contents of the recording information of the recording layer. As R ₀ , R ₁ and R ₂ , they enter the objective lens 11 again.

The reflected light beams R ₀ , R ₁ and R ₂ re-incident on the objective lens 11 are converted into parallel beams,
The optical axis direction of the beam splitter 17 is changed by the reflecting surface 17a of the beam splitter 17, and the light enters the Wollaston prism 18.

The Wollaston prism 18 separates each of the incident reflected light beams R ₀ , R ₁ and R ₂ into three, and a total of 9 reflected light beams R '(R ₀ , R ₁ , R ₂ ,
R ₁₀ , R ₁₁ , R ₁₂ , R ₂₀ , R ₂₁ , R ₂₂ ) are generated and made incident on the reflection mirror 19.

The reflected light beam R'which has entered the reflection mirror 19 is reflected by the reflection mirror 19, is condensed by the condenser lens 20, and is made astigmatic by the cylindrical lens 22. It is incident on 23.

Each of the light receiving surfaces 24a to 24 of the light detecting element 23
The d, 25, 26, 27 and 28 output a photodetection signal corresponding to the light intensity of the received reflected light beam to the signal processing unit 30.

The signal processing section 30 generates a tracking error signal, a focus error signal and a magneto-optical signal based on the photo detection signal output from the photo detection element 23, and sends the tracking error signal and the focus error signal to the control section 29. Then, the magneto-optical signal is output to the output buffer 31. .

The control unit 29 controls the lens driving unit 12 based on the tracking error signal and the focus error signal output from the signal processing unit 30 to adjust the position of the objective lens 21 in the focus direction Z and the track direction X. I do. The magneto-optical signal is used as reproduction information.

The present invention is not limited to the above embodiment, but can be modified in various ways. For example, the recording medium targeted by the apparatus of this embodiment is not limited to the MO magneto-optical disk, but may be a mini disk magneto-optical disk. Further, it may be an optical system in which a beam splitter for separating a light beam incident on the objective lens from the light beam generation source and a reflected light beam from the recording medium passing through the objective lens and a three-beam Wollaston prism are integrated.

[0049]

According to the invention described in claim 1 described above in detail, since three reflected light beams are respectively made incident on the first and second light receiving surfaces, a tracking error signal having a large signal intensity is obtained. It is possible to provide a photodetector capable of producing

According to the invention of claim 2, the first
Since three reflected light beams are made incident on the second light receiving surface and the second light receiving surface, respectively, it is possible to provide an optical pickup device capable of generating a tracking error signal having a large signal intensity.

According to the third aspect of the invention, since the light quantity ratio of the 0th order light and the ± 1st order light by the diffraction grating is set within the predetermined range, the signal strength of the tracking error signal is increased. It is possible to provide an optical pickup device capable of increasing the signal strengths of the magneto-optical signal and the focus error signal.

According to the fourth aspect of the present invention, since the basic division light amount ratio by the Wollaston prism is within the predetermined range, the optical pickup device capable of increasing the magneto-optical signal and the tracking error signal. Can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an optical pickup device of the present invention.

FIG. 2 is a perspective view showing an optical system of the present embodiment.

FIG. 3 is a principle diagram for explaining a diffraction phenomenon of a diffraction grating.

FIG. 4 is a perspective view for explaining polarization by a 3-beam Wollaston prism.

FIG. 5 is a diagram showing a configuration of a photodetector element.

FIG. 6 is a block diagram showing a control system of this embodiment.

FIG. 7 is a principle diagram for explaining generation of a focus error signal by a signal processing unit.

FIG. 8 is a diagram showing spots formed on a third light receiving surface of the photodetector.

FIG. 9 is a diagram showing spots formed on a third light receiving surface of the photodetector.

FIG. 10 is a diagram showing spots formed on a third light receiving surface of the photodetector.

FIG. 11 is a graph showing a signal value Fe of a focus error signal and defocus.

FIG. 12 is a diagram showing a reflected light beam from the recording layer of the magneto-optical disk.

FIG. 13 is a perspective view for explaining polarization by a 3-beam Wollaston prism.

FIG. 14 is a diagram showing a conventional photodetector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Optical pickup device 11 Objective lens 12 Lens drive part (lens drive means) 14 Semiconductor laser (light beam generation source) 15 Diffraction grating 18 3 beam Wollaston prism 23 Photodetector element 24a, 24b, 24c, 24d Split light receiving surface 25th 1 light receiving surface 26 second light receiving surface 27, 28 fourth light receiving surface 29 control unit (control means) D magneto-optical disk (recording medium) B, B ₀ , B ₁ , B ₂ irradiation light beam R, R ' , R ₀ , R ₁ , R ₂ , R ₁₀ , R ₁₁ , R ₁₂ ,
R ₂₀ , R ₂₁ , R ₂₂ reflected light beam

Claims (4)

[Claims] 1. At least 0-order light and ± 1 by a diffraction grating.
A photodetector element for irradiating a recording medium with a light beam separated into three beams of the next light and receiving the reflected light beams from the recording medium into at least three reflected light beams respectively by a Wollaston prism. A first light-receiving surface that receives at least three reflected light beams corresponding to the + 1st-order light, and a second light-receiving surface that receives at least three reflected light beams corresponding to the −1st-order light. A photo-detecting element having. 2. A light beam generating source for generating a light beam, a diffraction grating for separating the light beam from the light beam generating source into at least three light components of 0th order light and ± 1st order light, and the diffraction grating An objective lens that collects and irradiates the separated light beam on a recording portion of a recording medium and receives each reflected light beam from the recording medium, and at least three reflected light beams received by the objective lens, respectively. A Wollaston prism for separating and a photodetector for receiving at least nine reflected light beams from the Wollaston prism, the first light receiving surface for receiving at least three reflected light beams corresponding to the + 1st order light. And a second light receiving surface for receiving at least three reflected light beams corresponding to the −1st order light and a central reflected light beam of the three reflected light beams corresponding to the 0th order light A third light-receiving surface formed of a plurality of divided light-receiving surfaces for splitting and receiving the divided light beams, and a pair of fourth light-receiving beams which independently receive reflected light beams on both sides of at least three reflected light beams corresponding to the 0th-order light. An optical pickup device comprising: a light detecting element having a light receiving surface of the lens; and a lens driving unit that adjusts the position of the objective lens. 3. The optical pickup device according to claim 2, wherein a light quantity ratio of 0th order light to ± 1st order light by the diffraction grating is 8.5 to 15. 4. In the Wollaston prism, which separates an ordinary ray, a ray composed of an ordinary ray and an extraordinary ray, and an extraordinary ray, the ratio of the ordinary ray and the extraordinary ray to the total amount of light is 30 to 45%. The optical pickup device according to claim 2.