JP2702167B2 - Optical pickup - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magneto-optical pickup using a hologram.

[Problems to be Solved by Conventional Techniques and Inventions] In recent years, the information industry has been remarkably advanced, and the amount of information handled tends to increase. For this reason, instead of a recording or reproducing apparatus for recording or reproducing information using a conventional magnetic head, a light beam is irradiated to record information at a high density on a recording medium or to record on a recording medium at a high density. An optical information recording / reproducing apparatus capable of reproducing information recorded at a high density at a high speed has attracted attention.

As a rewritable recording method, a magneto-optical method of recording information on a recording medium according to the direction of magnetization (upward and downward) and reproducing the information by using a magneto-optical effect such as the Kerr effect has attracted attention.

In the magneto-optical system, an optical pickup capable of reading the rotation of the polarization plane is required. For example, in the optical pickup disclosed in Japanese Patent Application No. 62-336439 filed earlier by the present applicant, an information signal is obtained as follows. That is, for example, P-polarized light is irradiated to the recording medium, the reflected light from the recording medium surface will light vector P ₁ or P ₂ with S-polarized light component by receiving the rotation of the polarization plane by the Kerr effect. This light is transmitted through a half-wave plate having an azimuth angle of 22.5 degrees, the polarization plane is rotated by 45 degrees, incident on a polarization beam splitter, and split into reflected light and transmitted light. The reflected light and the transmitted light are emitted in parallel by a prism, received by a two-segment photodetector, and converted into an electric signal. Then, by taking the difference between the outputs of the detectors of the two-divided photodetector by a differential circuit, the difference between the respective light vectors P ₁ and P ₂ is obtained, and the upward and downward signals of the magnetization are determined. It has become.

However, the conventional optical pickup has a problem that the number of optical components of a differential optical system for obtaining an information signal is large, and it is difficult to reduce the size and the weight, thereby increasing the access time. Also, adjustment of the optical components was necessary.

In addition, the conventional optical pickup requires a control optical system for focus detection and tracking detection and a differential optical system divided into two, which increases the number of photodetectors. In the case where the focus error signal and the tracking error signal are detected by the four-segment photodetector using the above-mentioned method, since the error signals are not separated, they may interfere with each other and cause an error.

However, recently, in order to reduce the size and weight of an optical pickup, an optical pickup using a hologram as an optical system has been proposed.

For example, Japanese Patent Application Laid-Open No. Sho 62-120640 discloses that a light emitted from a light source and a reflected light from a recording medium using a phase type hologram, a surface relief type hologram, and a λ / 4 plate are not used for magneto-optics. An optical pickup that separates the optical pickup from the optical pickup is disclosed.

Japanese Patent Application Laid-Open No. 63-74149 discloses an optical pickup of a magneto-optical type, in which a hologram for focusing light from a light source toward a recording medium on the recording medium and a light reflected from the recording medium are diffracted toward the photodetector. And a third hologram for guiding a signal to two photodetectors is provided between the two holograms and the two photodetectors. ing.

As a related technique, Japanese Patent Application Laid-Open No. 62-249107 discloses a polarization beam splitter using a phase type diffraction grating having polarization properties.

Incidentally, in the optical pickup, it is necessary to detect a control signal of a focus error signal and a tracking error signal in addition to the information signal. However, in the above-mentioned Japanese Patent Application Laid-Open No. 62-120640, the detection of the control signal is considered. Not. Further, Japanese Patent Application Laid-Open No. 63-74149 describes that it is also possible to detect a shift in the focus direction and the track direction by devising a third hologram creation method. No means have been disclosed.

Therefore, in order to obtain the control signal, Japanese Patent Application Laid-Open No. 62-2776
As disclosed in Japanese Patent Publication No. 35, it is conceivable to interpose a hologram for separating a reflected light from a recording medium into a beam for detecting a control signal in an optical path from a light source to the recording medium.

However, in this case, the diffraction efficiency is reduced, the amount of light irradiated on the recording medium is reduced, and the amount of light received on the photodetector for detecting the control signal is also reduced, thereby deteriorating the performance. There is.

[Object of the Invention] The present invention has been made in view of the above circumstances, and enables an optical pickup that can be reduced in size and weight and that can efficiently obtain a magneto-optical information signal and a control signal. It is intended to provide.

[Means for Solving the Problems] An optical pickup according to the present invention provides a light source for emitting light for irradiating a magneto-optical recording medium, and guiding the light emitted from the light source to the magneto-optical recording medium, A first hologram for guiding the reflected light from the light source in a direction different from the light source, and an optical path from the light source to the recording medium on the optical path of the reflected light from the recording medium passing through the first hologram. A second hologram disposed outside and having a polarization property to separate reflected light from the recording medium into a plurality of light beams for detecting an information signal and detecting a control signal; and a light before the second hologram. A half-wave plate disposed on a road; and an information signal detection and control signal detection photodetector that receives each light beam separated by the second hologram.

[Operation] In the present invention, the light emitted from the light source is applied to the magneto-optical recording medium via the first hologram, and is reflected by rotating the polarization plane according to the direction of magnetization in the magneto-optical recording medium. You. This reflected light passes through the first hologram,
The light enters the second hologram, and is separated into a plurality of light beams for information signal detection and control signal detection by the second hologram. Then, this light beam is received by the information signal detection and control signal detection photodetectors, and an information signal and a control signal are obtained.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1 to 6 relate to a first embodiment of the present invention, FIG. 1 is an explanatory view showing the structure of an optical pickup, FIG. 2 is an explanatory view showing a second hologram in FIG. 1, and FIG. The figure is an explanatory view showing a configuration of an optical pickup of a modification of the embodiment,
FIG. 4 is a circuit diagram showing a circuit for generating an information signal and a control signal, FIG. 5 is an explanatory diagram showing a method for producing a first hologram, and FIG. 6 (a) shows a method for producing a second hologram. FIG. 6 (b) is an explanatory view showing an irradiation area of each light to the dry plate at the time of producing the second hologram.

As shown in FIG. 1, an optical pickup 1 for recording, reproducing, and erasing information on a magneto-optical recording medium 3 includes a semiconductor laser 2 as a light source, and diffracts light emitted from the semiconductor laser 2. A first hologram 5 that focuses on the recording surface of the magneto-optical recording medium 3 so as to focus on the recording surface, and diffracts reflected light from the recording medium 3 in a direction different from that of the semiconductor laser 2; It is arranged on the optical path of the reflected light from the recording medium 3 passing through one hologram 5 and outside the optical path from the semiconductor laser 2 to the recording medium 3.
A half-wave plate 6 and a second hologram 7 are provided, and _three photodetectors S ₁ , S ₂ and S ₃ for receiving the light beam emitted from the second hologram 7 are provided.

The semiconductor laser 2 emits, for example, P-polarized linearly polarized light, and this light is incident on the first hologram 5 from an oblique direction. The light passes through the first hologram 5, the diameter of the ellipse in the minor axis direction is enlarged, the beam shape is shaped into a substantially circular shape, and the light is focused and focused on the recording surface of the recording medium 3. . Information is recorded on the recording medium 3 by upward magnetization and downward magnetization. Therefore, the polarization plane of the P-polarized light incident on the recording medium 3 is rotated by the magneto-optical effect (Kerr effect) according to the magnetization direction of the recording medium. For example, assuming that the polarization plane rotates by θ degrees with respect to the upward magnetization, the polarization plane rotates by −θ degrees with respect to the downward magnetization.

The reflected light having the S-polarized component due to the rotation of the polarization plane enters the first hologram 5, is diffracted in a direction different from that of the semiconductor laser 2, and passes through the half-wave plate 6. , And enters the second hologram 7. As shown in FIG. 2, the second hologram 7 is, for example, entirely circular,
One of the semicircular portions 7a is a surface relief hologram having a polarization property of transmitting P-polarized light. The other half-circle portion is composed of two quarter-circle portions 7b and 7c, each of which is a surface relief hologram having a polarization property of diffracting S-polarized light. The surface relief hologram has a relief groove utilizing birefringence, diffracts light having a polarization direction parallel to the direction of the relief groove, and transmits light having a polarization direction perpendicular to the direction of the relief groove.

The angle formed between the polarization direction of the incident light with respect to the second hologram 7 and the direction of the relief groove of the second hologram 7 is
The azimuth of the half-wave plate 6 is 22.5 so that the angle is 45 degrees.
Set to degree. Thus, when the recording medium 3 is not subjected to rotation of the polarization plane, the P-polarized light component of TM (polarized light perpendicular to the lattice groove) and TE (polarized light parallel to the lattice groove) of the light incident on the second hologram 7 ), The light intensities of the S-polarized light components are equalized. When the recording medium 3 is rotated by the polarization plane, the ratio between the P-polarized component and the S-polarized component changes according to the upward magnetization and the downward magnetization.

The P-polarized component transmitted through the semi-circular portion 7a of the second hologram 7 is received by the photodetector S _2, 1/4 yen portion 7b, the S-polarized light component diffracted by 7c, respectively, the photodetectors The light is received at S ₁ and S ₃ . The photodetector S _2, as shown in FIG. 4, each photodetector is divided into four _{S 21, S 22, S 23} , S
_{Has 24} .

Next, a circuit for generating an information signal and a control signal will be described with reference to FIG.

First, a reproduction signal of the magneto-optical data section is obtained as follows. That is, the adder 11 obtains the sum signal of the outputs of the four photodetectors S ₂₁ , S ₂₂ , S ₂₃ , and S ₂₄ , and the adder 12 outputs the output signals of the photo detectors S ₁ and S ₃ . Is obtained. Then, the adder 11 is provided by the differential amplifier 13.
A difference signal between the output signal of the differential amplifier 13 and the output signal of the adder 12 is obtained. The output signal of the differential amplifier 13 becomes a reproduction signal of the magneto-optical data section. The sum signal of the outputs of the photodetectors S ₂₁ , S ₂₂ , S ₂₃ , and S ₂₄ , which is the output signal of the adder 11, corresponds to the light intensity of the P polarization component.
The sum signal of the output signals of the photodetectors S ₁ and S ₃ which is the output signal of the adder 12 corresponds to the light intensity of the S-polarized component. Therefore, the output signal of the differential amplifier 13 corresponds to the difference between the light intensity of the P-polarized component and the light intensity of the S-polarized component, whereby it is determined whether the magnetization is upward or downward.

The reproduction signal of the pre-pit section is added to the adders 11, 12
Is obtained by the output signal of the adder 14 that generates the sum signal of the output signals of

The focus error signal is obtained as follows. That is, the adder 15 causes the photodetectors S ₂₁ and S ₂₃
The sum signal of the outputs of
Sum signal of the output signal of the S _22, S ₂₄ are obtained. The difference signal between the output signals of the adder 15 and the adder 16 is obtained by the differential amplifier 17, and the output signal of the differential amplifier 17 becomes the focus error signal. In this embodiment, the second hologram 7 has a knife edge function in the knife edge method, and the transmitted light of the semicircular portion 7a of the second hologram 7 is divided into four light detectors in a focused state. It focused on the center of the S _2, in the state in which the recording medium 3 closer than the focus position, as indicated by the dashed line in FIG. 4, the photodetector S _21, S ₂₃ side enters the semicircular In a state where the recording medium 3 is farther from the focus position, as shown by a solid line in FIG. 4, the light enters the photodetectors S ₂₂ and S ₂₄ in a semicircular shape. The diameter of the semicircle increases as the deviation from the in-focus position increases. Therefore, the light quantity of the photodetectors S ₂₁ and S ₂₃ and the photodetectors S ₂₂ and S
By detecting the difference between the ₂₄ light amounts, a focus error signal can be obtained.

The tracking error signal is obtained from the output signal of the differential amplifier 18 that generates a difference signal between the output signals of the photodetectors S ₁ and S ₃ . In the present embodiment, the push-pull method for detecting the imbalance of the intensity distribution of the return light from the recording medium 3 is used. In the on-track state, the photodetectors S ₁ and S _{3 are used.}
Are the same, but if they go off the track, there will be a difference between the incident light amounts of the photodetectors S ₁ and S ₃ . Therefore, a tracking error signal can be obtained by generating a difference signal between the output signals of the photodetectors S ₁ and S ₃ by the differential amplifier 18.

Next, a method for forming the first hologram 5 will be described with reference to FIG.

First, the diverging light of the recording light O diverging from the point P ₁ corresponding to the position of the semiconductor laser 2 and the point corresponding to the position of the recording medium 3 toward the dry plate formed by coating the photoresist on the transparent substrate. and irradiating the converged light of the recording light beam b, which focuses on P ₂ causing interference. Moreover, the divergent light of the recording light a diverging from the point P ₃ corresponding to the position of the optical detector S _2, wherein interfere with each other focused light of the recording light b, and developed after exposure, the double exposure method A first hologram 5 is created. The first hologram 5 is, for example, a phase hologram.

Next, a method for forming the second hologram 6 will be described with reference to FIG.

First, for example, a focused plate of the recording lights O ₁ , O ₂ , and O ₃ is irradiated toward a dry plate formed by applying a photoresist to the half-wave plate 6 to cause interference. Incidentally, wherein O ₁ is focused at a point L ₂ corresponding to the position of the optical detector S _2, O ₂ is the point corresponding to the position of the optical detector S ₂
O ₃ is light that is focused on L ₂ and O ₃ is focused on a point L ₃ corresponding to the position of the photodetector S ₃ . Also, as shown in FIG. 6 (b), the O ₂ and O ₃ are each a 1/4 circle portion of the second hologram 7.
Irradiate the parts to be 7b and 7c. Further, the focused light of the recording lights O ₁ and O ₄ is irradiated toward the dry plate to cause interference. still,
The O ₄ is a light focused on the optical detector S _1, S _2, points corresponding to the position other than the S ₃ L _4. Also, as shown in FIG.
The O ₄ irradiates the semi-circular portion 7 a of the second hologram 7. In this way, double exposure is performed and development is performed, and at the same time, a relief groove is formed on an end face, thereby forming a second hologram 7 which is a surface relief hologram. The direction of the relief groove is such that it transmits the P-polarized light component and diffracts the S-polarized light component.

As described above, according to this embodiment, since the hologram is used for the optical system, the optical pickup can be reduced in size and weight, the access time can be reduced, and the number of parts is small and simple. Can be low price.

In addition, since a hologram (second hologram 7) for separating the reflected light from the recording medium 3 into a beam for detecting an information signal and a control signal is not interposed in the optical path from the semiconductor laser 2 to the recording medium 3, the diffraction efficiency is reduced. Lifting, recording medium 3
Can be increased. In addition, a large amount of light can be received on the photodetector for detecting the control signal, and an optical pickup with good performance can be obtained.

Further, it is not necessary to provide a single photodetector for reading signals in areas such as the pre-pit section and the data section, and the number of photodetectors is reduced by obtaining an information signal by a sum signal or a difference signal of each error signal. Can be low cost.

Further, since the return light from the recording medium 3 is focused by the hologram, the size of the photodetector can be reduced.

Further, in the present embodiment, the photodetector and the semiconductor laser 2 as the light source are arranged on the same line, so that they can be arranged on the same substrate. 6. By sandwiching the transparent substrate between the second hologram 7 and the second hologram 7, a smaller and non-adjustable optical pickup can be obtained.

In this embodiment, a surface relief type hologram is used as a hologram having a polarizing property. However, since the surface relief type hologram has a small lattice groove using birefringence, it is necessary to protect the surface. Therefore, instead of the surface relief hologram, S-polarized light and P-polarized light are separated by utilizing the fact that the diffraction efficiency of S-polarized light and P-polarized light is greatly changed by the product of the spatial frequency of the diffraction grating and the wavelength used. A polarizing beam splitter having a polarizing property using a phase grating hologram may be used.

Further, as means for protecting the second hologram 7, the second hologram 7 is provided on one end face of the transparent member, the semiconductor laser 2 and photodetector S _1, S _2, S ₃ of the package to the end face of the other end Close the first transparent member to one end face of another transparent member.
The hologram 5 may be bonded to the other end face, and the half-wave plate 6 may be bonded to the other end face so that the half-wave plate 6 and the second hologram 7 are brought closer to each other to protect the hologram. Further, as another protection means of the second hologram 7, a half-wave plate 6 is joined to the end face of the transparent member,
The second hologram 7 may be formed on an end face of the semiconductor laser 2 and a transparent member may be interposed between the second hologram 7 and the package of the semiconductor laser 2 and the photodetectors S ₁ , S ₂ , and S ₃ .

With the protection means as described above, a reliable optical pickup can be realized.

In this embodiment, the first hologram 5 has functions of a collimator lens, a shaping prism, and an objective lens. However, as shown in FIG. Instead, a first hologram 25 having the functions of a collimator lens and a shaping prism may be provided.

In the modification shown in FIG. 3, the light emitted from the semiconductor laser 2 is shaped into a parallel light beam by the first hologram 25, is focused by the objective lens 24, and is focused on the recording medium 3. Tie. The reflected light from the recording medium 3 is converted into a parallel light beam by the objective lens 24 and diffracted by the first hologram 25 toward the half-wave plate 6 and the second hologram 7.

When forming the first hologram 25, in FIG. 5, parallel light may be used instead of the recording light b to be focused.

Other configurations, operations and effects are the same as those of the first embodiment.

7 to 9 relate to a second embodiment of the present invention. FIG. 7 is an explanatory view showing the structure of an optical pickup, FIG. 8 is an explanatory view showing a second hologram in FIG. The figure is a circuit diagram showing a circuit for generating an information signal and a control signal.

In the present embodiment, as shown in FIG. 8, the second hologram 27 is, for example, entirely circular, and one of the semicircular portions 27a has a polarization property of transmitting P-polarized light and diffracting S-polarized light. It is a surface relief hologram. The other half-circle portion is composed of two quarter-circle portions 27b and 27c, each of which is a surface relief hologram having a polarization property of diffracting S-polarized light.

The azimuth of the half-wave plate 6 is set to 22.5 degrees so that the angle between the polarization direction of the incident light with respect to the second hologram 27 and the direction of the relief groove of the second hologram 27 is 45 degrees. Have been. Thereby, when the recording medium 3 is not subjected to the rotation of the polarization plane, the hologram 27 of the second
The light intensity of the P-polarized light component and the S-polarized light component of the light incident on the light source are equal, and the P-polarized light component transmitted through the semicircular portion 27a is equal to the S-polarized light component diffracted by the semicircular portion 27a. I have.

In this embodiment, the light detector S ₁₁ positioned to receive light transmitted through the semi-circular portion 27a of the second hologram 27 are arranged, an optical detector S ₁₃ is positioned to receive the diffracted light. Further, photodetectors S ₁₂ and S ₁₂ ′ are arranged at positions where the diffracted lights of the quarter circle portions 27b and 27c of the second hologram 27 are received, respectively.

As shown in FIG. 9, the photodetector S _12, S ₁₂ are respectively, have two divided photodetector _{S 41, S 42, S 43} , S 44.

Incidentally, how to create the second hologram 27 in this embodiment is the same as the second hologram 7 in the first embodiment, FIG. 6 (a), the optical detector S ₁₃ to the position of point L ₄
Is arranged.

Next, a circuit for generating an information signal and a control signal will be described with reference to FIG.

First, the reproduction signal of the magneto-optical data section is output from the photodetectors S ₁₁ and S ₁₁ .
_It is obtained by the output signal of the differential amplifier 31 which generates the difference signal of the ₁₃ output signals. The output signal of the light detector S ₁₁ corresponds to the light intensity of P-polarized component, while the output signal of the light detector S ₁₃ corresponds to the light intensity of S-polarized light component. Accordingly, the output signal of the differential amplifier 31 corresponds to the difference between the light intensity of the P-polarized component and the light intensity of the S-polarized component, whereby it is determined whether the magnetization is upward or downward.

Also, the reproduced signal of the pre-pit portion is output from each of the photodetectors S ₁₁ and S ₁₁ .
_13, obtained by the output signal of the _{S 41, S 42, S 43} , a differential amplifier 32 for generating a sum signal of the output signal of S _44.

The focus error signal is obtained as follows. That is, the adders 33 cause the photodetectors S ₄₁ and S ₄₃
The sum signal of the outputs of
Sum signal of the output signal of the S _42, S ₄₄ are obtained. Then, a difference signal between the output signals of the adders 33 and 34 is obtained by the differential amplifier 35, and the output signal of the differential amplifier 35 becomes a focus error signal. In the present embodiment, the second hologram 27 also has the function of a knife edge in the knife edge method, and the diffracted lights of the quarter circle portions 27b and 27c of the second hologram 27 are respectively in the focused state. 2-part photodetector S
_When the recording medium 3 is focused on the center of S ₁₂ ′ and the recording medium 3 is closer than the in-focus position, the recording medium 3 is incident on the photodetectors S ₄₁ and S ₄₃ in a quarter circle shape, and the recording medium 3 is focused. in a state apart from the position-focus, as indicated by the dashed line in FIG. 9, the optical detector S _42, S ₄₄ side 1
Incident in / 4 circular shape. The diameter of the quarter circle increases as the deviation from the in-focus position increases. Therefore, the light intensity of the photodetectors S ₄₁ and S ₄₃ and the photodetectors
By detecting the difference between the amount of S _42, S _44, the focus error signal is obtained.

The tracking error signal is obtained as follows. That is, by the adder 37, the photodetectors S ₄₁ and S _41
42 sum signal of output, i.e. the output signal is obtained photodetectors S _12, the adder 38, the sum signal of the output signal of the light detector S _43, S _44, that is, the output signal of the light detector S ₁₂ ' Is obtained. The difference signal between the output signals of the adder 37 and the adder 38 is obtained by the differential amplifier 39.
The 39 output signal becomes the tracking error signal. In the present embodiment, a push-pull method for detecting the imbalance of the intensity distribution of the return light from the recording medium 3 is used. In the on-track state, the incident light amounts of the photodetectors S ₁₂ and S ₁₂ ′ are equal, When off the track, the photodetector S ₁₂ ,
A difference occurs in the amount of incident light on S ₁₂ ′. Therefore, by generating a difference signal of the output signal of the light detector S _12, S ₁₂ 'by the differential amplifier 39, the tracking error signal is obtained.

In this embodiment, of the second hologram 27,
For the quarter circle portions 27b and 27c, a phase type hologram having no polarization may be used. The semicircular portion 27a may use a phase grating hologram having polarization.

Other configurations, operations and effects are the same as those of the first embodiment.

It should be noted that the present invention is not limited to the above embodiments, and for example,
Instead of providing the half-wave plate 6, the second holograms 7,27
The direction of the relief grooves of the second holograms 7 and 27 is determined so that the angle formed between the polarization direction of the incident light with respect to and the direction of the relief grooves of the second holograms 7 and 27 is a predetermined angle such as 45 degrees. Is also good.

Further, the first hologram 5 may transmit one of the light traveling from the semiconductor laser 2 to the recording medium 3 and the light traveling from the recording medium 3 to the second hologram.

[Effects of the Invention] As described above, according to the present invention, the use of a hologram makes it possible to reduce the size and weight of an optical pickup, and furthermore, a plurality of light beams for information signal detection and control signal detection. Since the second hologram having the polarization property of separating the light from the light source is arranged outside the optical path from the light source to the recording medium,
Efficiently, a magneto-optical information signal and a control signal can be obtained, and the 45-degree polarization plane is incident on the second hologram in a rotating state.
This has the effect of facilitating assembly. There is an effect that.

[Brief description of the drawings]

FIGS. 1 to 6 relate to a first embodiment of the present invention.
FIG. 2 is an explanatory view showing the structure of the optical pickup, and FIG.
FIG. 3 is an explanatory diagram showing a second hologram, FIG. 3 is an explanatory diagram showing a configuration of an optical pickup according to a modification of the embodiment, FIG. 4 is a circuit diagram showing a circuit for generating an information signal and a control signal, and FIG. FIG. 6 is an explanatory view showing a method for creating a first hologram, FIG. 6 (a) is an explanatory view showing a method for creating a second hologram, and FIG. FIG. 7 to FIG. 9 relate to a second embodiment of the present invention. FIG. 7 is an explanatory view showing the configuration of an optical pickup, and FIG. 2
FIG. 9 is a circuit diagram showing a circuit for generating an information signal and a control signal. 1 ...... optical pickup, 2 ...... semiconductor laser 3 ...... magneto-optical recording medium, 5 ...... first hologram 6 ...... 1/2-wavelength plate, 7 ...... second hologram S _1, S _2, S ₃ …… Photodetector

Claims (2)

(57) [Claims] A light source for emitting light for irradiating a magneto-optical recording medium; a light emitted from the light source being guided to the magneto-optical recording medium, and a reflected light from the recording medium being directed in a direction different from the light source. A first hologram leading to the first hologram and a light reflected from the recording medium passing through the first hologram on the optical path and outside the optical path from the light source to the recording medium, and reflected from the recording medium. A second hologram having a polarization property of separating light into a plurality of light beams for detecting an information signal and a control signal, and a half-wave plate disposed on an optical path before the second hologram; An optical pickup comprising: an information signal detection and control signal detection photodetector that receives each light beam separated by the second hologram. 2. The optical pickup according to claim 1, wherein said second hologram is divided into at least three parts to obtain a focusing control signal and a tracking control signal.