JP2638403B2 - Optical pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for recording or reproducing information on an optical disk.

[0002]

2. Description of the Related Art Conventionally, it has been desired to reduce the size of an optical disk device for recording and reproducing information using laser light.
Attempts have been made to reduce the size and weight of optical pickups.
Reducing the size and weight of the optical pickup is advantageous not only for reducing the size of the entire device, but also for improving the performance such as shortening the access time. 2. Description of the Related Art In recent years, optical pickups have been reduced in size and weight by using hologram optical elements, and some of them have been put to practical use. For example, as an example, Japanese Patent Application Laid-Open No. 62-146
No. 444, etc., a laser light is guided to a hologram lens for condensing by a plurality of internal reflections by a transparent and elongated light guide, and a reflected light from an optical disk is reflected by a plurality of internal reflections by the light guide. Some lead to the detector.

[0003]

However, the above-described conventional configuration has the following problems. (1) Necessary optical path length because a hologram lens for condensing laser light on the information holding surface of the optical disk, a polarization beam splitter for separating the reciprocating path, and a zone plate for obtaining astigmatism are separately configured. And it is difficult to reduce the size of the optical pickup. (2) Since the internal reflection is repeated several times by a concave reflector or the like until the output beam of the laser reaches the aspherical reflector, the polarization state of the laser light changes from linearly polarized light to elliptically polarized light, and the read recording signal The S / N ratio deteriorates. (3) Since there are several plane mirrors in the optical path on the return path including the recording signal reflected by the optical disk, the polarization state of the laser beam changes due to the reflection, and the S / N ratio of the recording signal is greatly deteriorated. (4) In the case of forming an incompletely polarized beam splitter, the manufacturing process is complicated because a film for the incompletely polarized beam splitter must first be coated on the upper surface of the light guide, and then the outer skin portion must be formed. (5) When the directions of inclination of the surfaces of the concave reflector and the plane mirror are different, it is difficult to manage the positional relationship between the surfaces and the inclination angle. (6) The configuration of the optical element is complicated and cannot be produced at low cost.

[0004]

In order to solve the above-mentioned conventional problems, the present invention provides a light guide member comprising a transparent parallel flat plate for guiding light from a light emitting element toward an optical disk by a plurality of internal reflections. A first hologram pattern for condensing light from the light emitting element guided by the light guide member onto the optical disc, and (2n + 1) with respect to the polarization direction of linearly polarized light from the light emitting element when n is an integer. ) Π
The composite hologram, in which the reflected light from the optical disc is diffracted in the direction of / 4 and superimposed with the second hologram pattern for changing the focus to light, has passed through the composite hologram to the plane of the optical guide member on the optical disc side. The P-polarized component of the reflected light from the optical disk is transmitted to the first light-receiving sensor, the polarization separating portion for reflecting the S-polarized component is directed to the light-receiving sensor-side plane of the light guide member, and the reflected light from the polarization separating portion is transmitted to the second light-receiving member.
A reflecting portion for reflecting light to the light receiving sensor is provided on a plane of the optical guide member on the optical disk surface side, and a transmission window for guiding reflected light from the reflecting portion to the second light receiving sensor is provided on a flat surface of the light guide member on the light receiving sensor side. The focal point of the reflected light from the optical disk that has passed exists between the polarization separation portion and the transmission window.
A focus error and information recorded on the optical disk are detected based on a difference between the light receiving sensor and the second light receiving sensor.

[0005]

According to the present invention, the first hologram pattern and the second hologram pattern of the composite hologram are formed as a pattern superimposed on the same area by the above structure, and the light condensing function and the reciprocating path are formed in one area. In addition to having three functions of a separating function and a function of changing to light for detecting a focus error, the second hologram pattern of the composite hologram allows the reflected light from the optical disc to be polarized in the direction of linearly polarized light from the light emitting element. On the other hand, when n is an integer, the light is diffracted in the direction of (2n + 1) π / 4, so that the P-polarized light component and the S-polarized light component can be halved with respect to the polarization separation portion.

The optical path from the light emitting element to the composite hologram and the optical path from the composite hologram to the light receiving sensor are:
By utilizing the internal reflection of the light guide member, a long light path length is realized by using a thin light guide member.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. 1A is a plan view of an optical pickup according to one embodiment of the present invention, and FIG. 1B is a line X of the optical pickup shown in FIG. 1A according to one embodiment of the present invention.
It is -X sectional drawing.

First, from a semiconductor laser which is a light emitting element,
The optical path on the outward path to the optical disk will be described. FIG.
4B, a laser beam 3 emitted horizontally from a semiconductor laser chip 2 mounted horizontally on a sensor substrate 1
The light guide member 5 is also formed by a trapezoidal reflection prism 4 also mounted on the sensor substrate 1 so that the reflection surface faces the semiconductor laser chip 2, from the entrance window 6 on the second surface 5 b of the transparent light guide member 5. 5 Diffuse light that enters obliquely into the interior 7
become. The diffused light 7 is reflected toward the second surface 5b by the first reflecting portion 46 provided on the first surface 5a facing the optical disk 9 on the upper surface of the light guide member 5, and becomes reflected light 47. Further, the reflected light 47 is reflected again to the first surface 5a side by the second reflecting portion 48 provided on the second surface 5b, and becomes reflected light 49. The reflected light 49 reflected by the second reflector 48 obliquely enters the composite hologram 8 formed on the first surface 5a and near the first reflector 46.

Normally, when the laser light is reflected by the first reflecting portion 46 and the second reflecting portion 48, the polarization state of the reflected light changes with the reflection. For example, the laser light incident as linearly polarized light may change to elliptically polarized light after reflection. In the magneto-optical recording information, linearly polarized light must be incident on the optical disk 9 and a slight Kerr rotation angle must be detected. Therefore, it is very important that the linearly polarized light be incident on the optical disk 9 while maintaining the state of linear polarization. . For this reason, in order to prevent the polarization state from being made elliptical due to reflection, a phase difference control film for controlling the phase difference of the polarization component is applied to the first reflection section and the second reflection section.

This phase difference control film has the following structure, for example.
It is something like The thickness of the film is d, the refractive index is n,
When the optical film thickness is represented by nd, the L layer is SiO 2 _Two (Nd =
207 nm, n = 1.45)._Two (Nd =
199 nm, n = 2.30) and the angle of incidence of light
Assuming 18.35 ° to the line, air, L layer, (L layer, H layer)¹¹-It has a film configuration like a light guide member. Here (L layer / H layer)¹¹Is (L
Layer / H layer) as a pair and repeat 11 times
Represents

As shown in FIG. 2A, two types of hologram patterns are superimposed on the composite hologram 8. FIG. 2B shows a first hologram pattern 8a which is concentric and has a smaller pitch toward the outer circumference, and converts the diffused light 7 into convergent light 11 which is condensed as a spot 10 on an information recording layer 9a of an optical disc 9. FIG. 2C shows that the reflected light of the spot 10 is changed to the backward diffraction light 12 by the second hologram pattern 8b.

Next, the return path from the optical disk 9 will be described. On the second surface 5b of the light guide member 5, there is formed a return polarization separation section 13 coated with a return polarization separation film that transmits the P polarization component of the return diffraction light 12 and reflects the S polarization component.

As shown in FIG. 1A, when the polarization state of the reflected light 49 incident on the composite hologram 8 is a linearly polarized light 14 as indicated by an arrow, the second hologram pattern 8b Since the diffraction direction is set to be 135 ° with respect to the polarization direction of the linearly polarized light 14, the return path diffracted light 12 is transmitted to the return path polarization separation unit 13 by a P polarization component,
The S-polarized light component becomes approximately half, and the amount of the transmitted light 15 from the return polarization splitting section 13 becomes approximately half of the return diffraction light 12. The transmitted light 15 is transmitted to the first light receiving sensor 1 formed on the sensor substrate 1.
Irradiate 6. The reflected light 17, which is about the remaining half of the return-diffraction light 12 reflected by the return polarization splitting unit 13,
The reflected light 19 is reflected by the return reflection part 18 of FIG. The reflected light 19 is transmitted through the transmission window 20 on the second surface 5b and then becomes transmitted light 21 to irradiate the second light receiving sensor 22. The backward-path diffracted light 12 is reflected by the backward-path polarization separation unit 1.
The composite hologram 8 and the like are designed so that the focal point 23 exists between the transmission window 3 and the transmission window 20.

The principle of detecting a magneto-optical signal will be described in more detail with reference to FIG. In FIG. 3, reference numeral 14 denotes the polarization direction of the linearly polarized light incident on the composite hologram 8 as described above. Since the composite hologram 8 does not affect the plane of polarization, if information is not recorded on the information recording layer 9a of the optical disk 9 (unless the information recording layer 9a is magnetized), it is reflected light of the spot 10. Return-path diffracted light 12 is also linearly polarized light 14
Has the same polarization direction as The polarization direction of the return-diffraction light 12 in such a state is as shown in FIG. 3 with respect to the polarization separation film of the return polarization separation unit 13 that transmits the P-polarized component almost 100% and reflects the S-polarized component almost 100%. The diffraction direction of the backward diffraction light 12 is set to 135 ° with respect to the polarization direction of the linearly polarized light 14 so that the light is incident at an azimuth of 45 °. When the linearly polarized light 14 is reflected by the magnetized information pits of the optical disc 9, the direction of rotation is ±± depending on the polarity and intensity of the magnetization.
It changes within the range of θk (Kerr effect). Now linearly polarized light 14
The state rotated by θk from the state described above is referred to as linearly polarized light 24, and the state rotated by −θk is referred to as linearly polarized light 25. When the magneto-optical signal modulated from the linearly polarized light 24 to the linearly polarized light 25 is made incident on the polarization separation film of the return polarization separation unit 13, the first light receiving sensor 16
The P-polarized light component detected by the second light receiving sensor 22 becomes like a signal 27, and the P-polarized light component detected by the second light receiving sensor 22 becomes like a signal 27. Since the signal 26 and the signal 27 are out of phase by 90 °, if the two signals are differentially amplified, the signal component is doubled,
Since the noise of the in-phase component is canceled, as a result S
/ N ratio is improved.

Input and output of various signals to and from the sensor substrate 1 on which the first light receiving sensor 16, the second light receiving sensor 22, and the like are formed are performed via a lead frame 28. 2
Reference numeral 9 denotes a package made of a non-conductive material such as resin and ceramics. The space 30 surrounded by the light guide member 5 and the package 29 is usually filled with an inert gas such as nitrogen gas, but may be filled with a transparent resin or the like as needed.

In this embodiment, the diffraction direction of the backward diffraction light 12 is set to 135 ° with respect to the polarization direction of the linearly polarized light 14. However, this angle may be any of 45 °, 225 ° and 315 °. good.

Next, the shapes of the first light receiving sensor 16 and the second light receiving sensor 22 and the principle of signal detection will be described with reference to FIG. The first light receiving sensor 16 and the second light receiving sensor 22 have four portions 16a, 16b, 16c, respectively.
16d and 22a, 22b, 22c, 22d. Here, currents from the respective portions 16a, 16b, 16c, 16d and 22a, 22b, 22c, 22d of the first light receiving sensor 16 and the second light receiving sensor 22 are represented by I (16a), I (16b), I (16), respectively. (16c), I
(16d), and I (22a), I (22b), I
(22c) and I (22d). As can be seen from the circuit diagram of FIG.
E. FIG. ), Tracking error (TE), and RF recording signal (RF) have a circuit configuration that can be obtained by the following equations (Equation 1), (Equation 2), and (Equation 3). ing.

[0018]

(Equation 1)

[0019]

(Equation 2)

[0020]

(Equation 3)

The focus error signal (F.
E. FIG. ) Will be further described. Now, the spot 10 of the composite hologram 8 is accurately focused on the information recording layer 9a of the optical disc 9 and the irradiation shape of the laser beam on the first light receiving sensor 16 and the second light receiving sensor 22 in this focused state is determined. Assuming 31a and 32a respectively, the following (Equation 4)
The irradiation light intensity distribution of the laser beam and the positional relationship between the first light receiving sensor 16 and the second light receiving sensor 22 are adjusted so that

[0022]

(Equation 4) E. FIG. = 0

Next, when the distance between the optical disc 9 and the first surface 5a is close from the in-focus state, the irradiation shapes of the laser beams on the first light receiving sensor 16 and the second light receiving sensor 22 are 31c and 32c, respectively. , The focus error signal (FE) changes as shown in (Equation 5).

[0024]

(Equation 5) E. FIG. > 0

Conversely, when the distance between the optical disc 9 and the first surface 5a is far from the in-focus state, the irradiation shape of the laser beam on the first light receiving sensor 16 and the second light receiving sensor 22 becomes 31
b, 32b, and the focus error signal (FE)
Changes as in (Equation 6).

[0026]

(Equation 6) E. FIG. <0

The focus error detection method described above is known as a spot size method, and the tracking error detection method is known as a push-pull method.

By designing the focal point 23 of the backward-path diffracted light 12 to exist between the backward-path polarization separating section 13 and the transmission window 20, the focus error can be reduced by the astigmatism method that has been widely used in the related art. Compared with the case of detection, a complicated hologram pattern for generating astigmatism is unnecessary, and the second hologram pattern 8b of the composite hologram 8 is a very simple pattern of only focusing.

FIGS. 5 and 6 show a configuration in the case of using a focus error detection method which is simpler than the spot size method. In FIG. 5A, a polarization separation film 33 is further laminated on the second surface 5b of the light guide member 5 and coated with a diffusion film 34 and a light shielding film 35, and a polarization separation window 36 is provided. As shown in FIG. 5B, when the shape of the diffusion film 34 is an annular zone, the inner diameter is d, and the outer diameter is D, the diameter H of the return-path diffracted light 12 on the polarization separation film 33 is expressed by the following equation (7). D and D are determined so that

[0030]

[Expression 7] d <H <D

This is because the transmitted light in the range from d to H is diffused by the diffusion film 34 so that the reflected light 37 is not affected. For this reason, the diffusion film 34 may be an absorption film that absorbs laser light. The transmitted light 38 transmitted through the inner diameter side of the inner diameter d of the diffusion film 34 reaches the first light receiving sensor 39.

FIG. 6 shows the reflected light 19 incident on the second light receiving sensor 40. Second surface 5 of light guide member 5
b is coated with a light-shielding film 42 to form a transmission window 41 smaller than the diameter of the reflected light 19. This light-shielding film 42 may of course be coated as a region continuous with the light-shielding film 35 of FIG. FIG. 6B illustrates the size of the diameter when the reflected light 19 reaches the second surface 5 b and the diameter of the transmission window 41. The transmitted light 43 from the transmission window 41 is the second
The light receiving sensor 40 is irradiated.

When using such a focus error detecting method, the first light receiving sensor 39 and the second light receiving sensor 40 are the first light receiving sensor 16 and the second light receiving sensor 22 shown in FIG.
The difference between the outputs of the first light receiving sensor 39 and the second light receiving sensor 40 having a light receiving area large enough to receive the transmitted light 38 and the transmitted light 43 is not necessary as the focus error. Can be. FIG. 7 shows the first
3 illustrates the respective outputs of the light receiving sensor 39 and the second light receiving sensor 40, and the difference signal between the first light receiving sensor 39 and the second light receiving sensor 40.

In this focus error detection method, since the multi-segment light receiving sensor as shown in FIG. 4 is not used, it is not necessary to finely adjust the positions of the first light receiving sensor 39, the second light receiving sensor 40 and the irradiation shape of the laser light. And is excellent in productivity and long-term stability.

The method shown in FIG. 1 and FIGS.
In any of the methods, the portions other than the entrance window 6, the return polarization splitting section 13, the transmission window 20, and the transmission window 41 may be used by coating the light shielding film 35 over the entire second surface 5b of the light guide member 5. Since the influence of various stray lights generated in the light guide member 5 on the light receiving sensor can be significantly reduced, the S / N ratio of the signal is improved.

FIG. 8 is an enlarged view showing the structure near the semiconductor laser chip 2 and the reflecting prism 4 in FIG. The reflecting prism 4 has a trapezoidal shape, and its reflecting surface 4a is coated with a semi-transmissive film that transmits a part of the light emitted from the semiconductor laser chip 2 into the reflecting prism 4. The semi-transmitted light 45 taken into the reflection prism 4 is detected by a monitor sensor 44 formed at a portion of the sensor substrate 1 that contacts the bottom surface of the reflection prism 4. The monitor sensor 44 constantly monitors a change in the amount of light of the semiconductor laser chip 2 and feeds back information to a control circuit. Conventionally, the amount of light emitted from the rear surface 2a of the semiconductor laser chip 2 has been monitored. However, the light emitted from the rear surface 2a may cause stray light to other light receiving sensors (the first light receiving sensor 16, the second light receiving sensor 22, etc.). Become. In the configuration of the present invention, since the light is taken into the reflection prism 4, there is an advantage that the influence on other light receiving sensors can be reduced. The laser light emitted from the semiconductor laser chip 2 enters the entrance window 6 provided on the second surface 5 b of the light guide member 5 by the reflection prism 4. By using the reflecting prism 4, the semiconductor laser chip 2 can be mounted horizontally on the sensor substrate 1, which is advantageous in terms of wiring and heat radiation, and has the advantage that the incident angle to the light guide member 5 can be set with high accuracy. There is.

In this embodiment, the laser light 3 from the semiconductor laser chip 2 is reflected and is obliquely incident on the composite hologram 8, but the light quantity distribution of the laser light 3 is usually elliptical. Therefore, if the minor axis of the ellipse of the light amount distribution is set to be within the optical axis plane formed by the optical axis of the laser beam 3 in the optical path from the semiconductor laser chip 2 to the composite hologram 8, the light enters the composite hologram 8. The light quantity distribution to be obtained can be approximated to a circle. Since the laser beam 3 usually has a plane of polarization in the minor axis direction of the elliptical radiation, the semiconductor laser chip 2 may be mounted in a direction in which the plane of the optical axis coincides with the plane of polarization as shown in FIG. .

[0038]

As described above, the present invention comprises a light guide member made of a transparent parallel flat plate for guiding light from a light emitting element toward an optical disk by a plurality of internal reflections, and is guided by this light guide member. A first hologram pattern for condensing the light from the light emitting element on the optical disk, and an optical disk with a direction of (2n + 1) π / 4 with respect to the polarization direction of the linearly polarized light from the light emitting element when n is an integer. An optical disc that has passed through the composite hologram to a plane on the optical disc side of an optical guide member made of a transparent parallel flat plate, in which a composite hologram superimposed with a second hologram pattern that diffracts reflected light from the light into a focused light is formed. The polarized light separating unit that transmits the P-polarized light component of the reflected light from the board to the first light receiving sensor and reflects the S-polarized light component to the plane of the light guide member on the light receiving sensor side. A reflecting portion for reflecting the reflected light from the portion to the second light receiving sensor to the flat surface of the light guide member on the optical disk side; The focal point of the reflected light from the optical disk that has passed through the composite hologram exists between the polarization splitting section and the transmission window, and the focus error and the optical disk are caused by the difference between the first light receiving sensor and the second light receiving sensor. By detecting the information recorded on the board, the first hologram pattern and the second hologram pattern of the composite hologram are formed as a pattern superimposed on the same area. Can provide three functions: a condensing function, a round-trip path separating function, and a function of converting to light for detecting a focus error, and utilizing the internal reflection of a light guide member. Therefore, a light guide member that is thinner than the length of the optical path can be used, so that the size of the optical pickup can be reduced, and the reflected light from the optical disk can be reflected from the light emitting element by the second hologram pattern of the composite hologram. When n is an integer with respect to the polarization direction of the linearly polarized light, the light is diffracted in the direction of (2n + 1) π / 4, so that the P-polarized light component and the S-polarized light component can be halved with respect to the polarization separation portion. 50% of the light reflected from the panel is applied to the first light-receiving sensor and the second light-receiving sensor, respectively.
And a high-quality RF in which in-phase noise components other than signals having information recorded on the optical disc are removed by differential amplification of the first light receiving sensor and the second light receiving sensor. (Recording) signal can be obtained. Furthermore, since the focal point of the reflected light from the optical disk exists between the return half-transmission portion and the transmission window, the first light receiving sensor and the second
A focus error signal can be obtained by a method such as a spot size method based on a difference between light receiving sensors. In addition, since the manufacturing method has a simple configuration such as patterning of a hologram on a parallel plate and film formation, high-precision and high-integration is possible, and an inexpensive optical pickup for magneto-optical recording is provided. can do.

[Brief description of the drawings]

FIG. 1A is a plan view of an optical pickup according to an embodiment of the present invention; FIG. 1B is a cross-sectional view of the optical pickup shown in FIG.

FIG. 2A is a diagram showing a superimposed pattern of a first hologram pattern and a second hologram pattern of an optical pickup according to an embodiment of the present invention; FIG. FIG. 1C shows a second hologram pattern of the optical pickup in one embodiment of the present invention.

FIG. 3 is a diagram illustrating a principle of detecting a magneto-optical signal of an optical pickup according to an embodiment of the present invention;

FIG. 4 is a diagram illustrating a shape and a signal processing circuit of a light receiving sensor included in an optical pickup according to an embodiment of the present invention.

FIG. 5A is a cross-sectional view of the vicinity of a first light receiving sensor when another focus error detection method of the optical pickup according to the embodiment of the present invention is used. FIG. 5B is an optical pickup according to the embodiment of the present invention. Plan view near the first light receiving sensor when another focus error detection method is used

FIG. 6A is a cross-sectional view of the vicinity of a second light receiving sensor when another focus error detection method of the optical pickup according to the embodiment of the present invention is used. FIG. 6B is an optical pickup according to the embodiment of the present invention. Plan view near the second light receiving sensor when another focus error detection method is used

FIG. 7A is an output waveform diagram from the first light receiving sensor when another focus error detection method of the optical pickup according to one embodiment of the present invention is used, and FIG. Output waveform from the second light receiving sensor when another focus error detection method of the pickup is used. FIG. 3C shows the first light reception when another focus error detection method of the optical pickup according to the embodiment of the present invention is used. Output waveform diagram obtained by subtracting the output of the second light receiving sensor from the output of the sensor

FIG. 8 is an enlarged view of the vicinity of a semiconductor laser chip and a reflecting prism of an optical pickup according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor base 2 Semiconductor laser chip 4 Reflection prism 5 Optical guide member 8 Composite hologram 9 Optical disk board 10 Spot 11 Return path diffracted light 13 Return path polarization separation part 14 Linear polarization 16 First light receiving sensor 18 Return path reflection part 20 Transmission window 22 Second light reception Sensor 28 Lead frame 29 Package 34 Diffusion film 46 First reflector 48 Second reflector

Claims (8)

(57) [Claims] A light-emitting element for irradiating the optical disk with linearly polarized light; a first light-receiving sensor and a second light-receiving sensor for receiving light reflected from the optical disk; A light guide member formed of a transparent parallel plate that guides light from the light emitting element to the optical disk by a plurality of internal reflections and guides reflected light from the optical disk to the two light receiving sensors. ,
A first hologram pattern for condensing light from the light emitting element on an optical disc, and (2n + 1) π with respect to the direction of linearly polarized light from the light emitting element when n is an integer.
A composite hologram superimposed with a second hologram pattern for diffracting the reflected light from the optical disc in the direction of / 4 and turning it into a focused light passes through the composite hologram to the plane of the optical guide member on the optical disc side. A polarization splitting unit that transmits the P-polarized component of the reflected light from the optical disk to the first light receiving sensor and reflects the S-polarized component to the plane of the light guide member on the light receiving sensor side; A reflecting portion for reflecting the reflected light from the light receiving member to the second light receiving sensor to a flat surface of the light guide member on the optical disk side; and a transmission window for guiding the reflected light from the reflecting portion to the second light receiving sensor. And the focal point of the reflected light from the optical disk that has passed through the composite hologram exists between the polarization splitting unit and the transmission window. Optical pickup and detecting the information recorded on the focus error and the optical disc board by the difference between the optical sensor and the second light receiving sensor. 2. The optical pickup according to claim 1, wherein a phase difference control film for controlling a phase of a polarization component of light from the light emitting element is provided on an internal reflection surface of the light guide member. 3. A light quantity distribution in a plane perpendicular to an optical axis of light emitted from the light emitting element is an elliptical distribution, and a minor axis of the ellipse is a light in an optical path from the light emitting element to the composite hologram. 2. The optical pickup according to claim 1, wherein the axis exists on a plane where the axis exists. 4. The optical pickup according to claim 1, wherein said light emitting element and said two light receiving sensors are arranged in non-contact with said light guide member. 5. An optical pickup according to claim 4, further comprising an incident light reflecting member for reflecting light from said light emitting element and causing the light to enter the light guide member. 6. An optical pickup according to claim 5, wherein said light emitting element and said incident light reflecting member are arranged on a sensor substrate on which both said light receiving sensors are formed. 7. The incident light reflecting member is a trapezoidal prism, and a slope surface of the trapezoidal prism is coated with a semi-transmissive film, and a light amount monitor sensor is formed on the sensor substrate in contact with a bottom surface of the trapezoidal prism. Part of the light from the light emitting element is transmitted through the trapezoidal prism,
The optical pickup according to claim 6, wherein the light quantity of the light emitting element is monitored by the light quantity monitor sensor. 8. A polarized light separating film constituting the polarized light separating section,
The diaphragm is formed by a member that diffuses light, and has a diaphragm having a diaphragm smaller than the beam diameter of the reflected light from the optical disc, and the transmission window is made smaller than the beam diameter of the reflected light from the optical disc to form the diaphragm. 5. The optical pickup according to claim 4, wherein the first light-receiving sensor and the second light-receiving sensor detect light transmitted from the transmission window, respectively, and detect a focus error based on a light amount difference of the transmitted light.