JP3364955B2 - 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 disc.

[0002]

2. Description of the Related Art Conventionally, there has been a demand for miniaturization of an optical disk device which records and reproduces information by using laser light.
Attempts are being made to reduce the size and weight of optical pickups.
The reduction in size and weight of the optical pickup is advantageous not only for downsizing the entire device, but also for improving performance such as shortening access time. In recent years, the size and weight of optical pickups have been reduced by using hologram optical elements, and some of them have been put to practical use. For example, as an example thereof, JP-A-62-146
No. 444, etc., the laser light is guided to a hologram lens for condensing by a plurality of internal reflections by a transparent and slender light guide body, and the reflected light from the optical disc board is reflected by a plurality of internal reflections by the light guide body. There are things that lead to the detector.

[0003]

However, the above-mentioned conventional structure has the following problems. (1) Required optical path length because the hologram lens for converging the laser light on the information holding surface of the optical disc, the polarization beam splitter for separating the round trip path, and the zone plate for obtaining astigmatism are separately configured. However, it is difficult to downsize the optical pickup. (2) Before the output beam of the laser reaches the aspherical reflector, internal reflection is repeated several times by the concave reflector, etc., so that 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 returning optical path including the recording signal reflected by the optical disk, the polarization state of the laser light changes due to reflection, and the S / N ratio of the recording signal deteriorates significantly. (4) When forming an incompletely polarized beam splitter, the manufacturing process is complicated because it is necessary to first coat the film for the incompletely polarized beam splitter on the upper surface of the light guide body, and then to form the outer cover. (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 structure of the optical element is complicated and cannot be manufactured inexpensively.

[0004]

In order to solve the above-mentioned conventional problems, the present invention provides a light guide member composed of a transparent parallel plate for guiding light from a light emitting element toward a direction of an optical disk disc by a plurality of internal reflections. An internal reflection surface of the light guide member on the side opposite to the optical disc board is a polarization separation film that transmits the P-polarized component of the light from the light-emitting element and reflects the S-polarized component.
A first hologram pattern for focusing light from the light emitting element guided by the light guide member on an optical disc board;
When n is an integer, the reflected light from the optical disc is diffracted in the direction of (2n + 1) π / 4 with respect to the polarization direction of the S-polarized component from the light emitting element reflected by the internal reflection surface of the light guide member. The first light receiving sensor detects the P-polarized component of the reflected light from the optical disc board that has passed through the composite hologram, and the composite hologram in which the second hologram pattern that changes the light to be focused is superposed on the plane of the optical guide member on the optical disc board side. To the plane of the light guide member on the side of the light receiving sensor of the light guide member, and the reflection portion of the light guide member for reflecting the reflected light to the second light receiving sensor on the side of the optical disk of the light guide member. A transparent window for guiding the reflected light from the reflecting section to the second light receiving sensor is provided on the flat surface of the optical guide member on the light receiving sensor side, and the reflected light from the optical disc board passing through the composite hologram is Point is present between the polarization separation section and the transmission window, by the difference between the first light receiving sensor and the second light-receiving sensor configured to detect the information recorded on the focus error and the optical disc board.

[0005]

According to the present invention, the first hologram pattern of the composite hologram and the second hologram pattern of the composite hologram are formed as a pattern superimposed in the same area by the above-mentioned structure. It is possible to have three functions, that is, a separation function and a function for changing to light for focus error detection, and the second hologram pattern of the composite hologram causes the reflected light from the optical disk board to be reflected by the internal reflection surface of the light guide member. When n is an integer with respect to the polarization direction of the S-polarized component from the light emitting element (2n +
1) Since the light is diffracted in the direction of π / 4, it is possible to make the P-polarized component and the S-polarized component half in the polarization splitting portion. Further, by utilizing the internal reflection of the light guide member for the light paths from the light emitting element to the composite hologram and from the composite hologram to the second light receiving sensor, a light guide member thinner than the length of the light path is used, and further internal reflection is performed. By causing the polarization splitting film to reflect the ellipticization of the polarization state that occurs at the time of, it is possible to make the light into linearly polarized light again.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first 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 an embodiment of the present invention, and FIG. 1B is a sectional view taken along line XX of the optical pickup shown in FIG. 1A according to the embodiment of the present invention. .

First, from the semiconductor laser which is a light emitting element,
The forward optical path to the optical disc will be described. Figure 1
Laser light 3 emitted horizontally from the semiconductor laser chip 2 mounted horizontally on the sensor substrate 1 in FIG.
Is a trapezoidal reflection prism 4 which is also mounted on the sensor substrate 1 so that its reflection surface faces the semiconductor laser chip 2, and the light guide member from the incident window 6 of the second surface 5b of the transparent light guide member 5. 5 Diagonal incidence inside the diffused light 7
become. The diffused light 7 is reflected toward the second surface 5b side by the outward reflection portion 46 provided on the first surface 5a facing the optical disc board 9 on the upper surface of the light guide member 5, and becomes reflected light 47. Further, this reflected light 47 is reflected by P provided on the second surface 5b.
The outward polarization splitting unit 48, which is formed of a polarization splitting film that transmits the polarization component and reflects the S polarization component, returns again to the first polarization splitting unit 48.
The light is reflected on the surface 5a side and becomes reflected light 49. The reflected light 49 reflected by the outward polarization splitting unit 48 obliquely enters the composite hologram 8 formed on the first surface 5a and near the outward reflection unit 46.

The reason why the polarization separating film is used for the outward polarization separating section 48 is that when the laser light is normally reflected by the outward reflecting section 46 and the like, the polarization state of the reflected light changes with the reflection. For example, light incident as linearly polarized light may change to elliptically polarized light after being reflected. In magneto-optical recording, linearly polarized light must be incident on the optical disc board 9 to detect a slight Kerr rotation angle. Therefore, it is very important to keep the linearly polarized light incident on the optical disc board 9. For this reason, in order to prevent the polarization state from becoming elliptical due to reflection, conventionally, a phase difference control film for controlling the phase difference of polarization components has been applied to the reflection part. However, since the retardation control film has a multilayer film structure, the manufacturing process becomes complicated and the manufacturing cost increases.
Therefore, in this embodiment, the outward reflection portion 46 has a simpler reflection film structure, and the reflected light 47 is allowed to be elliptically polarized light. However, since the P-polarized light component generated by the reflection is transmitted by the outward polarization separation unit 48, the reflected light 49 becomes the linearly polarized light of only the S-polarized light again. This forward polarization splitting unit 48 requires a polarization splitting film for the backward polarization splitting unit 13 on the same second surface 5b as will be described later, so that the forward polarization splitting unit 48 and the backward polarization splitting unit 13 are made of the same material, If coating is performed in the same process, it will not cause any increase in manufacturing cost.

On the composite hologram 8, two kinds of hologram patterns as shown in FIG. 2A are superimposed and drawn. FIG. 2B shows a first hologram pattern 8a that is concentric and has a pitch that becomes smaller toward the outer periphery and that converts the diffused light 7 into converged light 11 that is condensed as a spot 10 on the information recording layer 9a of the optical disc board 9. In FIG. 2C, the reflected light of the spot 10 is changed to the backward diffracted light 12 by the second hologram pattern 8b.

Next, the return path from the optical disc board 9 will be described. On the second surface 5b of the light guide member 5, there is formed a backward polarization separating section 13 coated with a backward polarization separating film which transmits the P polarized component of the backward diffracted light 12 and reflects the S polarized component.

As shown in FIG. 1A, in the second hologram pattern 8b, if the polarization state of the reflected light 49 incident on the composite hologram 8 is linearly polarized light 14 as indicated by the arrow, the backward diffracted light 12 is generated. Since the diffraction direction is set to 45 ° with respect to the polarization direction of the linearly polarized light 14, the backward-path diffracted light 12 is transmitted to the backward-path polarized light separating portion 13 as the P-polarized component, S
The polarization component is about half, and the amount of the transmitted light 15 from the backward polarization splitting unit 13 is about half that of the backward diffracted light 12. The transmitted light 15 is the first light receiving sensor 16 formed on the sensor substrate 1.
Irradiate. The reflected light 17, which is about the other half of the backward diffracted light 12 reflected by the backward polarization splitting unit 13, is the first surface 5a.
The reflected light 19 is reflected by the return reflection part 18 and travels toward the second surface 5b again. The reflected light 19 passes through the transmission window 20 of the second surface 5b and then becomes the transmitted light 21 and irradiates the second light receiving sensor 22. The backward-path diffracted light 12 is returned to the backward-polarization separation unit 13.
The composite hologram 8 and the like are designed so that a focal point 23 exists between the transmission window 20 and the transmission window 20.

The principle of magneto-optical signal detection will be described in more detail with reference to FIG. In FIG. 3, 14 is 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 polarization plane, it is the reflected light of the spot 10 unless information is recorded on the information recording layer 9a of the optical disc board 9 (when the information recording layer 9a is not magnetized). The backward diffracted light 12 also has the same polarization direction as the linearly polarized light 14. Return path diffracted light 1 in such a state
Almost 100% of the P-polarized component is transmitted in the polarization direction of 2,
Return-path polarization splitting unit 13 that reflects almost 100% of S-polarized light component
As shown in FIG. 3, the diffraction direction of the backward diffracted light 12 is linearly polarized 14
It is set to 45 ° with respect to the polarization direction of. When the linearly polarized light 14 is reflected by the magnetized information pits of the optical disc board 9,
The rotation direction changes within ± θk depending on the polarity of magnetization and the strength of magnetization (Kerr effect). Now, the state of θk rotation from the state of linearly polarized light 14 is referred to as linearly polarized light 24, and the state of −θk rotation is referred to as linearly polarized light 25. Linearly polarized light 24 to linearly polarized light 2
When the magneto-optical signal modulated up to 5 is made incident on the polarization splitting film of the backward polarization splitting section 13, the P polarization component detected by the first light receiving sensor 16 becomes a signal 26, which is detected by the second light receiving sensor 22. The S-polarized component becomes like the signal 27. Since the signals 26 and 27 are out of phase with each other by 90 °, differential amplification of both signals doubles the signal component and cancels noise of the in-phase component, resulting in an improved S / N ratio. .

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

In the present embodiment, the diffraction direction of the backward diffracted light 12 is set to 45 ° with respect to the polarization direction of the linearly polarized light 14, but this angle may be 135 °, 225 ° or 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,
16d, and 22a, 22b, 22c, 22d. Here, the currents from the respective portions 16a, 16b, 16c, 16d of the first light receiving sensor 16 and the second light receiving sensor 22 and 22a, 22b, 22c, 22d are respectively I (16a), I (16b) and I ( 16c), I
(16d), and I (22a), I (22b), I
(22c) and I (22d). As can be seen from the circuit diagram of FIG. 4 , the focus error (F.
E. ), A tracking error (TE), and an RF (recording) signal (RF) are represented by the following mathematical formula (Equation 1),
The circuit configuration is obtained by (Equation 2) and (Equation 3).

[0016]

[Equation 1]

[0017]

[Equation 2]

[0018]

R. F. = [{I (16a) + I (16b)} + {I (16c) + I (16d) }] -[{I (22a) + I (22b)) + {I (22c) + I (22d )}]

Of these, the focus error signal (F.
E. ) 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 board 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 shown. Assuming 31a and 32a respectively, the following (Equation 4)
The irradiation intensity distribution of the laser light and the positional relationship between the first light receiving sensor 16 and the second light receiving sensor 22 are adjusted so that

[0020]

[Equation 4]

Next, when the distance between the optical disc board 9 and the first surface 5a is approached from the focused state, the irradiation shapes of the laser light 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 in (Equation 5).

[0022]

[Equation 5]

On the contrary, when the distance between the optical disk 9 and the first surface 5a is out of focus, the irradiation shape of the laser light on the first light receiving sensor 16 and the second light receiving sensor 22 is 31.
b, 32b, and the focus error signal (FE)
Changes like (Equation 6).

[0024]

[Equation 6]

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

As described above, by designing the focal point 23 of the backward-path diffracted light 12 to exist between the backward-path polarization splitting portion 13 and the transmission window 20, the focus error can be eliminated by the astigmatism method which is often used conventionally. Compared to 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 that only collects light.

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

[0028]

[Equation 7]

This is because the transmitted light in the range from d to H is diffused by the diffusion film 34 and does not affect the reflected light 37. For this reason, the diffusion film 34 may be an absorption film that absorbs laser light. The transmitted light 38 that has passed 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
A light-shielding film 42 is coated on b to form a transmission window 41 smaller than the diameter of the reflected light 19. Of course, the light shielding film 42 may be coated as a continuous region with the light shielding film 35 of FIG. FIG. 6B shows the size of the reflected light 19 when it reaches the second surface 5b 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 illuminated.

When using such a focus error detection 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.
Need not be divided as described above, and 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 used as the focus error. You can FIG. 7 shows the first
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 are shown.

Since the multi-division light receiving sensor as shown in FIG. 4 is not used in this focus error detection method, delicate position adjustment between the first light receiving sensor 39, the second light receiving sensor 40 and the irradiation shape of the laser light is unnecessary. It is excellent in productivity and long-term stability.

The method shown in FIG. 1 and FIGS.
In any of the above methods, the entrance window 6 and the polarization splitting unit 1
If parts other than 3, the transparent window 20 and the transparent window 41 are coated with the light shielding film 35 over the entire second surface 5b of the light guide member 5, various stray light generated in the light guide member 5 can be received. The signal S / N ratio is improved because the influence on the signal can be significantly reduced.

FIG. 8 is an enlarged view showing the structure in the vicinity of the semiconductor laser chip 2 and the reflecting prism 4 of FIG. The reflecting prism 4 is trapezoidal, and its reflecting surface 4a is coated with a semi-transmissive film that transmits a part of the emitted light of the semiconductor laser chip 2 into the reflecting prism 4. The semi-transmissive light 45 taken into the reflection prism 4 is detected by the monitor sensor 44 formed in a portion of the sensor substrate 1 that is in contact with the bottom surface of the reflection prism 4. The monitor sensor 44 constantly monitors the light quantity change of the semiconductor laser chip 2 and feeds back information to the control circuit. Conventionally, the amount of light emitted from the rear surface 2a of the semiconductor laser chip 2 was monitored, but 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 through the entrance window 6 provided on the second surface 5b of the light guide member 5 by the reflecting prism 4. By using the reflection 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 dissipation, and the merit that the incident angle to the light guide member 5 can be set accurately. There is.

FIGS. 9A and 9B illustrate the case where the light emitted from the semiconductor laser chip 2 is P-polarized with respect to the second surface 5b. FIG. 9A shows the second surface 5b.
It shows a case where a P-polarized light 50 having a polarization plane in the paper surface is converted into an S-polarized light 51 perpendicular to the paper surface by using a transmission type optical rotator 56 (for example, a half-wave plate or the like) attached to the sheet. In FIG. 9B, a quarter-wave plate 53, which is attached to the first surface 5a and whose back surface is coated with a reflection film 52, is reciprocated, and a P-polarized light 54 having a polarization plane within the paper surface is S-polarized perpendicular to the paper surface. It shows a case of converting to polarized light 55.
The advantage of using the light emitted from the semiconductor laser chip 2 as P-polarized light after converting it to S-polarized light is as follows.

The light quantity distribution of the emitted light of the semiconductor laser is usually elliptical. The plane of polarization is in the minor axis direction of the ellipse. For this reason, the minor axis of the ellipse of the light quantity distribution is made to exist in the optical axis plane formed by the optical axis of the laser light 3 in the optical path from the semiconductor laser chip 2 to the composite hologram 8, and the outgoing polarization separation section 48 is S-polarized. By making it reach, the distribution of the amount of light incident on the composite hologram 8 can be approximated to a circular shape, and at the same time, linear polarization of only good S-polarized light can be incident on the composite hologram 8.

[0037]

As described above, the present invention includes an optical guide member formed of a transparent parallel flat plate for guiding light from a light emitting element toward a direction of the optical disk board by a plurality of internal reflections, and an optical disk board of the light guide member. Is a polarization separation film that transmits the P-polarized component of the light from the light-emitting element and reflects the S-polarized component of the light from the light-emitting element on the opposite side, and collects the light from the light-emitting element guided by this light guide member onto the optical disc board. The first hologram pattern that emits light and the optical disc in the direction of (2n + 1) π / 4 with respect to the polarization direction of the S-polarized component from the light emitting element reflected by the internal reflection surface of the light guide member when n is an integer. A composite hologram, which is formed by superimposing a second hologram pattern that diffracts the light reflected from the board and turns it into a focused light, passes through the composite hologram to the optical guide board side plane of the light guide member. And the P-polarized component of the reflected light from the optical disc board passes through the first light-receiving sensor, the light receiving sensor side of the plane of the light guide member by the polarization separation section for reflecting the S-polarized light component,
The reflection part that reflects the reflected light from the polarization splitting part to the second light receiving sensor is received by the light guide member through the transmission window that guides the reflected light from the reflection part to the second light receiving sensor on the plane of the optical guide member on the optical disc side. The focus of the reflected light from the optical disc board which is provided on the flat surface on the sensor side and has passed through the composite hologram exists between the polarization separation section and the transmission window, and the focus error occurs due to the difference between the first light receiving sensor and the second light receiving sensor. The first hologram pattern and the second hologram pattern of the composite hologram are formed as a pattern superimposed in the same area by being configured to detect the information recorded on the optical disc board and the information recorded on the optical disc board. It can have three functions in one area: a light condensing function, a round-trip path separating function, and a function for changing to light for focus error detection. Since the forward path to and from the composite hologram to the second light receiving sensor uses multiple internal reflections of the light guide member, a light guide member that is thinner than the optical path length can be used, and the overall size of the element can be reduced. it can. Also,
By coating the polarization separating film on the outward reflection portion, it is possible to prevent the linearly polarized light from becoming elliptical due to internal reflection. Further, the outward polarization polarization film and the backward polarization polarization film are continuously made of the same material, so that the elliptical polarization of the linearly polarized light can be prevented without increasing the cost. Further, when n is an integer with respect to the polarization direction of the S-polarized component from the light emitting element, which is the reflected light from the optical disc board reflected by the internal reflection surface of the light guide member by the second hologram pattern of the composite hologram (2n + 1) Since the light is diffracted in the direction of π / 4, it is possible to split the P-polarized component and the S-polarized component into 50 and 50 in the polarization splitting unit, and the reflected light from the optical disc board is respectively transmitted to the first light receiving sensor and the second light receiving sensor. It is possible to disperse at a rate of 50%, and by the differential amplification of the first light receiving sensor and the second light receiving sensor, in-phase noise components other than the signal having the information recorded on the optical disc are removed. An RF (recording) signal can be obtained. Further, since the focal point of the reflected light from the optical disk board exists between the return semi-transmissive portion and the transmission window, the focus error signal can be obtained by means of the spot size method or the like due to the difference between the first light receiving sensor and the second light receiving sensor. . Also, as a manufacturing method, it is possible to provide an optical pickup for magneto-optical recording, etc., which can be highly accurately and highly integrated because it has a simple configuration such as patterning a hologram on a parallel plate and film formation. can do.

[Brief description of drawings]

1A is a plan view of an optical pickup according to an embodiment of the present invention, and FIG. 1B is a sectional view taken along line XX of the optical pickup shown in FIG. 1A according to an embodiment of the present invention.

FIG. 2A is a diagram showing a superposed pattern of a first hologram pattern and a second hologram pattern of an optical pickup according to an embodiment of the present invention. FIG. 2B is a diagram of an optical pickup according to an embodiment of the present invention. 1 (c) is a diagram showing a second hologram pattern of the optical pickup according to the embodiment of the present invention.

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

FIG. 4 is a diagram and a signal processing circuit diagram of a light receiving sensor which constitutes an optical pickup according to an embodiment of the present invention.

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, and FIG. 5B is an optical pickup according to the embodiment of the present invention. Plan view of the vicinity of the first light receiving sensor when another focus error detection method of FIG.

FIG. 6A is a 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 of the vicinity of the second light receiving sensor when another focus error detection method of FIG.

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 the embodiment of the present invention is used, and FIG. 7B is a light waveform according to the embodiment of the present invention. The output waveform diagram from the second light receiving sensor in the case of using another focus error detection method of the pickup is the first light receiving in the case of using the other focus error detection method of the optical pickup in the embodiment of the present invention. 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.

FIG. 9 (a) is a diagram showing an example of the present invention in which the P-polarized light emitted from the semiconductor laser chip of the optical pickup is transmitted and S
An enlarged view of the main part near the polarization element to be polarized is shown in FIG. 7B is an expansion of the main part near the quarter-wave plate where the P-polarized light emitted from the semiconductor laser chip of the optical pickup in the embodiment of the present invention is reflected to become S-polarized light. Figure

[Explanation of symbols]

1 sensor base 2 Semiconductor laser chip 4 Reflective prism 5 Light guide member 8 Composite hologram 9 Optical disc board 10 spots 11 convergent light 12 Return path diffracted light 13 Return polarization splitter 14 Linearly polarized light 16 First light receiving sensor 18 Return Reflector 20 transparent window 22 Second light receiving sensor 28 lead frame 29 packages 34 Diffusion film 46 Outward reflection part 48 Outward polarization separation unit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI G11B 7/135 G11B 7/135 Z (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 11/105 G11B 7 / 09-7/22

Claims (7)

(57) [Claims] 1. A light emitting element for radiating linearly polarized light onto an optical disc board, and a first light receiving element for receiving reflected light from the optical disc board.
The light receiving sensor and the second light receiving sensor are disposed between the light receiving sensors and the optical disc board, and the light from the light emitting element is guided to the optical disc board by a plurality of internal reflections. And a light guide member made of a transparent parallel plate for guiding to both the light receiving sensors, wherein the P-polarized component of the light from the light emitting element is transmitted through an internal reflection surface of the light guide member on the light receiving sensor side, A first hologram pattern for condensing the light from the light emitting element reflected by the internal reflection surface of the light guide member on the optical disc board as a polarization separation film that reflects the S polarization component, and n is an integer While diffracting the reflected light from the optical disc in the direction of (2n + 1) π / 4 with respect to the polarization direction of the S-polarized component from the light emitting element reflected by the internal reflection surface of the light guide member. The P-polarized component of the reflected light from the optical disc board that has passed through the composite hologram is directed to the plane of the optical guide member on the optical disc side of the composite hologram which is superposed with the second hologram pattern for converting the light to connect the points. 1 the polarization splitting portion formed of a polarization splitting film that transmits the S-polarized light component to the light receiving sensor and directs the reflected light from the polarization splitting portion to the plane of the light guide member on the light receiving sensor side. 2 A reflecting portion for reflecting to the light receiving sensor is provided on a plane of the optical guide member on the optical disc side, and a transmission window for guiding the reflected light from the reflecting portion to the second light receiving sensor is provided on both of the light receiving members of the light guide member. The focal point of the reflected light from the optical disc board that has been provided on a plane and has passed through the composite hologram exists between the polarization separation section and the transmission window, and the first light receiving sensor and the second light receiving sensor An optical pickup characterized by detecting a focus error and information recorded on an optical disk disc by the difference between 2. A polarization separation film, which is provided on an internal reflection surface of the light guide member on the side of both the light receiving sensors and which guides light from the light emitting element to an optical disk board, and a polarization which constitutes the polarization separation section. The optical pickup according to claim 1, wherein the separation film and the separation film are continuously provided. 3. The linearly polarized light of the light emitted from the light emitting element is an S-polarized component with respect to the internal reflection surfaces of the light guide member on the side of the light receiving sensors.
The optical pickup described. 4. The optical pickup according to claim 1, wherein the light emitting element and the both light receiving sensors are arranged in non-contact with the light guide member. 5. The optical pickup according to claim 4, further comprising an incident light reflecting member that reflects light from the light emitting element to make the light incident on the light guide member. 6. The optical pickup according to claim 5, wherein the light emitting element and the incident light reflecting member are arranged on a sensor substrate on which the both light receiving sensors are formed. 7. The incident light reflection member is a trapezoidal prism, and a semi-transmissive film is coated on an inclined surface of the trapezoidal prism, and a light quantity monitor sensor is formed on the sensor substrate by contacting the bottom surface of the trapezoidal prism. Part of the light from the light emitting element is transmitted inside the trapezoidal prism,
7. The optical pickup according to claim 6, wherein the light amount monitor sensor monitors the light amount of the light emitting element.