JPS62219339A - Light pickup - Google Patents

Abstract

PURPOSE:To exactly read out a light beam from an information recorder without requiring severe mounting accuracy of a hologram, and also, without shifting a focus of incident light to an optical disk due to a vibration, etc. of an actuator, by using the hologram instead of the reflected light of a mirror. CONSTITUTION:A light beam which is made on a lambda/4 plate 20 is emitted to a beam splitter 19. The beam splitter 19 curves the incident light beam by 90 deg., and makes it incident on a converging lens 21. The light beam which is made incident on the converging lens 21 is irradiated by the converging lens 21, to a detector 22 which exists in a focal position of the converging lens 21. Also, the light beam which is irradiated to this detector 22 is the reflected light from a disk 14 which scarcely causes an error by a hologram 23. Such an error is smaller error than that of a shift angle (DELTA...)=2DELTAtheta which is generated in case when for instance, the incident light A is shifted by an angle DELTAtheta, by using a conventional mirror, and a data of the disk 14, which is detected by the detector 22 goes to a more accurate data.

Description

Detailed Description of the Invention (Summary of the Invention) The present invention has a structure in which light is irradiated onto an information recording medium such as an optical disk through a hologram, and the diffraction of the hologram is used to generate light parallel to the main axis of an objective lens. , and thereby obtain accurate information from the information recording medium.

[Technical field of invention]

The present invention relates to an optical pickup that reads information from an information recording medium such as an optical disk.

[Traditional technique]

As shown in Fig. 6, a conventional optical pickup is installed close to a disk 1 on which information is recorded by providing unevenness on its surface, and is divided into a fixed optical system 2 and a driving optical system 3. We are trying to make system 3 lighter.

Here, the fixed optical system 2 includes a semiconductor laser 4. Collimator lens 5. Beam splitter 6, λ/4i7° and converging lens 8. The driving optical system 3 is composed of a detector 9, an actuator 13. Mirror 10. Objective lens 11. It is composed of coils 12a and 12b. A light beam from a fixed optical system 2 is received by a driving optical system 3 and focused by an objective lens 11 onto a disk 1 which is rotated in the direction of an arrow E by a motor (not shown). Focusing is performed by moving the objective lens 11 up and down in the C direction, and tracking is performed by moving the objective lens 11 with a small working distance and driving the actuator 13 in the B direction with a large working distance.

By moving the driving optical system 3 in this way.

The laser beam oscillated from the semiconductor laser 4 passes through the collimator lens 5. Beam splitter 6, λ/4 plate 7, mirror 1
0. The light enters the uneven portion 1a of the disk 1 via the objective lens 11. The reflected light from the uneven portion 1a becomes information light created by the optical path difference.

This reflected light is reflected by the objective lens 11. Mirror 10. λ/4 plate 7
The beam is bent 90 degrees by the beam splitter 6.

It is read by a detector 9 through a converging lens 6.

In such a conventional optical pickup, the uneven portion 1a of the disk 1 is irradiated with a light beam by focusing and tracking as described above.

[Problem that the invention seeks to solve]

In the conventional optical pickup as described above, in order to obtain focused reflected light from the disk 1, incident light parallel to the main axis 11a of the objective lens 11 is required. However, if the mirror lO shifts by Δθ, the reflected light, that is, the light incident on the objective lens 11, shifts by 2×80. Therefore, in the driving optical system 3, the optical path precision of the reflected light from the mirror 10 is required to be particularly precise. For this reason, the mounting precision of the mirror 10 has become strict.

Furthermore, when the actuator 13 moves in the direction of arrow B, it may swing up and down (in the same figure). When the actuator 13 swings up and down by Δθ.

The optical path of the reflected light from the mirror 10 is also shifted by Δθ. As a result, beam focusing of the light incident on the objective lens 11 is lost. For these, disk 1
It was not possible to obtain a focused incident light at the top.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional drawbacks, it is an object of the present invention to provide an optical pickup in which the focus of light incident on an optical disk does not shift due to setting errors of the mirror 10, vibrations of the actuator 13, or the like.

[Means for solving problems]

According to the present invention, by using a hologram instead of a mirror, the laser light emitted from the semiconductor laser enters the objective lens parallel to the main axis of the objective lens, and is located at the focal point of the objective lens. This is achieved by precisely irradiating the signal surface of the disk with laser light.

[For production]

As mentioned above, by using a hologram instead of the reflected light from the mirror, even if the hologram is slightly tilted with respect to the objective lens, the diffracted light from the hologram is irradiated parallel to the main axis of the objective lens, and the signal surface of the disk is illuminated. By injecting a precisely focused laser beam, the reflected light can accurately obtain the information formed on the disk.

[Embodiments of the invention]

Hereinafter, nine embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing an optical pickup according to an embodiment of the present invention. In this figure, the optical pickup is placed close to the disk 14 and is composed of a fixed optical system 15 and a driving optical system 16, as in FIG. 6 described above. The fixed optical system 15 is the same as described above.

Semiconductor laser 17. Collimator lens 18. Beam splitter 19. λ/4 plate 20. Converging lens 21.

The driving optical system 16 is composed of a detector 22 and a hologram 2.
3. Objective lens 24. It is composed of coils 25a, 25b, etc. Further, the drive optical system 16 is configured to be movable in the direction of the arrow via an actuator 26 by a linear motor or the like (not shown).

On the other hand, the disc 14 has a concave-convex portion 14 on which signals such as images, audio, and control data are recorded on a signal surface (lower surface in the figure) 14a.
b is formed. Further, when reading out a signal from the disk 14, the disk 14 is rotated in the direction of arrow E around the support shaft 14c, and the signal is read out by a laser beam that enters through an objective lens 24, which will be described later.

In the optical pickup of this embodiment configured as described above,
The operation of reading signals on the disk 14 will be explained below.

First, a control circuit (not shown) moves the driving optical system 16 to a signal reading position on the disk 14 via the actuator 26 described above. At the same time as this movement, disk 1
4 is also rotated in the E direction and the objective lens 24 is moved to the reading start position.
focus.

Thereafter, in response to a reading start signal (not shown), the laser beam from the semiconductor laser 17 is turned off, and the laser beam that enters the beam splitter 19 via the collimator lens 18 is emitted from the beam splitter 19 as it is, and
/4 The hologram 23 in the drive optical system 16 via the slope 20
incident on . The hologram 23 diffracts the incident laser light and emits one diffracted light. The diffracted light (B) emitted from the hologram 23 is made to have an exit angle θ that is the same angle as the incident angle θ of the laser light (A) that is incident on the hologram 23 . Moreover, even if the hologram 23 is deviated by an angle △θ due to the above-mentioned reason, when the emitted light (diffraction light) B is emitted to the hologram 23 at an emission angle of θ in order to read the signal from the disk 14. , the deviation angle Δψ of the emitted light B is (tanθ)(Δθ)2, which is a very small angle.

Therefore, the diffracted light (B
) is the mounting precision of the hologram 23 and the actuator 2.
6 (vibration of the hologram 23), and allows light parallel to the main axis 24a of the objective lens 24 to enter the objective lens 24.

Further, in order to always position the concavo-convex portion 14b of the disk 14 on the focal point of the objective lens 24, a signal from a control circuit (not shown) is input to the coils 25a and 25b, and the objective lens 24 is
and the uneven portion 14b.

Therefore, the light incident on the objective lens 24 is directed toward the main axis 24a.
The signal from the disk 14 is read (by irradiating light onto the uneven portion 14b), and the data (reflected light) is sent to the hologram 23 via the objective lens 24. incident.

The hologram 23 diffracts the above-mentioned incident reflected light and outputs the diffracted light to the λ/4 plate 20 in the fixed optical system 15. At this time, the relationship between the incident light and the reflected light on the hologram 23 is opposite to that of the above-mentioned incident light A and output light B. That is, in this case, the incident light is B and the outgoing light is A, and the outgoing light A is an outgoing light that is not affected by the vibration of the actuator 26.

In this way, the light incident on the λ/4 plate 20 is emitted to the beam spiriter 19. The beam splitter 19 bends the incident light by 90 degrees and enters the converging lens 21 .

The light incident on the converging lens 21 is directed by the absorption lens 21 onto the detector 22 located at the focal point of the converging lens 21 . Moreover.

The light irradiated to this detector 22 is the hologram 2 described above.
3, it is one reflected light from the disk 14 with less error. In addition, this error is 1 when using the conventional mirror 10. For example, the deviation angle (△ψ
)=2Δθ, this is a small error. Therefore, the data of the disk 14 detected by the detector 22 becomes more accurate data.

FIG. 3 is a block diagram of an optical pickup according to a second embodiment of the present invention. In the same figure, the same PB materials as those in FIG. The difference in this figure from FIG. 1 is that a hologram 27 is disposed on the optical path of the laser beam between the λ/4 plate, the two metal plates, and the zero-gram polarizing plate 23.

Further, this hologram 27 is arranged within the fixed optical system 15. This hologram 27 is the hologram 23 mentioned above.
The laser light incident on the hologram 27 is diffracted by the λ/4 plate 2 and the metal plate 0, and the hologram 27 emits diffracted light with less "shake". Therefore, this hologram 27 hardly causes any deviation of the principal axis of the laser beam. That is, 1 as shown in this example, 2
By using holograms 23.27.

It is possible to realize an optical pickup with better information detection accuracy than the optical pickup amplifier of the above-described embodiment.

Further, FIGS. 4(a) to 4(e) show a third embodiment, in which a hologram 28 is used as the objective lens 24. In addition, in FIGS. 3A to 3C, a hologram 28 is used as the objective lens 24, and at the same time, the hologram 28 is used as the objective lens 24.
3 into the hologram 23 and the hologram 23
This is an example in which the light emitted from the drive optical system 16 is arranged at each location so that the angle of the light emitted from the drive optical system 16 is the same. As shown in this embodiment, a hologram 23 is placed at each location within the drive optical system 16.
By arranging the drive optical system 16, it is possible to effectively utilize the space within the drive optical system 16.

Further, FIG. 5 shows a fourth embodiment of the present invention.

In this figure as well, the same members as in FIG. 3 are given the same numbers. The difference between this figure and FIG. 3 is as follows.

Instead of using the hologram 23 and objective lens 24, one hologram 29 is used.

In this way, one hologram 29 is made to function as the objective lens 24, and moreover, the principal axis 29a of the diffracted light emitted from the hologram 29 and the incident light entering the hologram 29 are equiangular with respect to the hologram 29. Arrange it as you like. When the hologram 29 is arranged in this way, the actuator 26
Even if the hologram 29 vibrates (the hologram 29 is tilted), the principal axis 29a of the diffracted light remains unchanged. Therefore, according to this embodiment, accurate information can of course be obtained from the disk 14 even if the actuator 26 vibrates.

An optical pickup can be constructed by omitting the objective lens 24.

In the above embodiments, nine embodiments have been described in which the present invention is applied to optical discs, but the present invention may be incorporated into other information recording devices.

〔Effect of the invention〕

As explained in detail above, according to the present invention, it is not necessary to make the mounting precision of the hologram strict, and the focus of the incident light on the optical disk does not shift due to vibration of the actuator, etc., and accurate optical reading from the information recording device can be performed. can be done.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an optical pickup according to the present invention. FIG. 2 is a configuration diagram illustrating the relationship between input and output to a hologram polarizing plate. FIG. 3 is a configuration diagram of an optical pickup according to a second embodiment of the present invention. FIG. 4 (al~(C1 is a configuration diagram of an optical pickup according to a third embodiment of the present invention. FIG. 5 is a configuration diagram of an optical pickup according to a fourth embodiment of the present invention. FIG. 6 is a configuration diagram of an optical pickup according to a fourth embodiment of the present invention. It is a configuration diagram of an optical pickup. 14...Disk 15...Fixed optical system 16...Drive optical system 17...Semiconductor laser 18...Collimating lens 19...Beam brick 20 . . . λ /41 anti-21...Convergent lens 22...Detector 23.27.28.29...Hologram 24...Objective lenses 25a, 25b...Coil patent applicant Fujitsu Ltd.14 2o: walk τ slope 14a: 4gJ+me
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Claims (8)

[Claims] (1) An optical pickup having an optical system for irradiating light onto an information recording medium and detecting light reflected by the information recording medium, characterized in that a hologram is used in the optical system. (2) The optical system has a fixed optical system whose position is fixed and a movable driving optical system, and the hologram is provided within the driving optical system. Optical pickup described in section. (3) the fixed optical system is a semiconductor laser beam collimating system;
The driving optical system comprises a λ/4 plate, a beam splitter, and a reflected light detector, and the driving optical system comprises means for driving an objective lens and an actuator for driving the driving means in the track direction. The optical pickup described in Section 2. (4) The optical pickup according to claim 3, wherein the hologram is fixed to the actuator and placed between the objective lens and the λ/4 plate. (5) The optical pickup according to claim 3, wherein the objective lens is a hologram. (6) The optical pickup according to claim 3, wherein the objective lens and hologram are composed of one objective lens hologram. (7) The optical pickup according to any one of claims 4 to 6, wherein the main axes of the incident light and the outgoing light of the hologram are equiangular to each other with respect to the hologram surface. . (8) The optical system includes a fixed optical system whose position is fixed and a movable driving optical system, and the hologram is provided within the fixed optical system on the side from which light is emitted to the driving optical system. An optical pickup according to claim 1, characterized in that: