JPH11353698A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device which is capable of preventing the occurrence of noise due to return lights to a semiconductor laser at the time of recording and reproducing and erasing information with respect to an optical disk and which uses a hologram. SOLUTION: In this optical disk device, a luminous flux outgoing from a semiconductor laser 1 is made incident on an objective lens 7 with a hologram 4 to be converged on an optical disk 8 by the objective lens 7 and a reflected luminous flux from the disk 8 is made incident on the hologram 4 with the objective lens 7 to be diffracted by the holgram 4 and the reflected flux is guided a photodiode 9. In this case, an optical isolator 6 deflecting the reflected luminous flux from the disk 8 is provided between the semiconductor laser 1 and the objective lens 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical disk device,
The present invention relates to an optical pickup device used for an optical card device, an optical tape device, and the like, and more particularly, to an optical pickup device using a hologram.

[0002]

2. Description of the Related Art Conventionally, as an optical pickup device of this type, a light beam emitted from a semiconductor laser is made incident on an objective lens via a hologram and condensed on an information recording medium by the objective lens. There is known a device in which a reflected light beam from the hologram is incident on the hologram through the objective lens, diffracted by the hologram, and guided to a light receiving element (for example, JP-A-5-250718, JP-A-6-76340). Gazette, JP-A-6-314438).

FIG. 6 is a perspective view showing an example of a configuration of an optical pickup device using the hologram, and FIG. 7 is an explanatory diagram of a light beam in the device. A light beam from a semiconductor laser 1 as a light source is separated into three light beams (one main beam and two sub-beams for detecting a radial error) by a diffraction grating 3 formed on the lower surface of a hologram element 2, and the hologram element The light passes through the hologram 4 formed on the upper surface of the second light 2 as 0th-order diffracted light. 0 passed through this hologram 4
The next-order diffracted light becomes parallel light by the collimating lens 5 and is condensed on the optical disk 8 as an information recording medium by the objective lens 7. A part of the light beam reflected from the optical disk 8 is diffracted by the hologram 4 on the upper surface of the hologram element 2 via the objective lens 7 and the collimator lens 5 and is incident on a photodiode as a light receiving element.

[0004]

However, in an optical pickup device using a hologram as exemplified in FIGS. 6 and 7, a part of the reflected light beam that has passed through the hologram as the 0th-order diffracted light is a semiconductor laser. Since the light returns to the light emitting point, the oscillation characteristics of the semiconductor laser fluctuate, and there is a possibility that noise may be generated during information recording or information reproduction on the information recording medium. The generation of noise due to the return light to the semiconductor laser hardly causes a problem in an optical pickup device dedicated to information reproduction, but a high-power semiconductor laser whose oscillation characteristics are liable to fluctuate in an optical pickup device capable of recording information. Therefore, the generation of the noise tends to be a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical pickup device using a hologram, which is used for recording information on an information recording medium, reproducing information, and erasing information. An object of the present invention is to provide an optical pickup device capable of preventing generation of noise due to return light to a laser.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a light beam emitted from a semiconductor laser is incident on an objective lens via a hologram, and the objective lens impinges on an information recording medium. In an optical pickup device that condenses and reflects a light beam reflected from the information recording medium through the objective lens to the hologram, diffracts the light beam by the hologram, and guides the light beam to a light receiving element, the optical pickup device is disposed between the semiconductor laser and the objective lens. A light deflecting means for deflecting a light beam reflected from the information recording medium.

According to the first aspect of the present invention, the light deflecting means provided between the semiconductor laser and the objective lens deflects the light beam reflected from the information recording medium. Due to this deflection, the reflected light beam of the 0th-order diffraction that has passed through the hologram also reaches a position shifted from the light emitting point of the semiconductor laser, and no return light is focused on the light emitting point of the semiconductor laser.

According to a second aspect of the present invention, there is provided the optical pickup device according to the first aspect, wherein the light deflecting means is mountable, wherein the objective of the light beam emitted from the semiconductor laser by mounting the light deflecting means is provided. The angle of deflection by the light deflecting means is set such that the amount of change in the angle of incidence on the lens falls within a predetermined allowable range.

In the optical pickup device of the second aspect, even when the light deflecting means is mounted due to the problem of returning light to the light emitting point of the semiconductor laser, the light beam emitted from the semiconductor laser is transmitted to the objective lens. Of the incident angle falls within a predetermined allowable range, and normal information recording, information reproduction, and information erasing can be performed.

According to a third aspect of the present invention, there is provided the optical pickup device according to the first aspect, wherein the light deflecting means is mountable, wherein the light receiving element receives the diffracted light from the hologram by mounting the light deflecting means. The angle of deflection by the light deflecting means is set such that the movement of the light receiving spot is within the range of the light receiving section.

In the optical pickup device according to the third aspect, even when the light deflecting means is mounted due to the problem of returning light to the light emitting point of the semiconductor laser, the diffracted light from the hologram is reflected on the light receiving element. Moves within the range of the light receiving portion of the light receiving element, and normal detection of the reflected light beam is enabled.

According to a fourth aspect of the present invention, a light receiving element having a plurality of light receiving portions is used as the light receiving element, and a light receiving spot moving in a direction intersecting a dividing line of the light receiving portion is detected to collect light on the information recording medium. 4. The optical pickup device according to claim 3, wherein the movement of the light receiving spot of the diffracted light from the hologram on the light receiving element by attaching the light deflecting means is along the division line. To be in the direction
The direction of deflection by the light deflection means is set.

In the optical pickup device according to the fourth aspect, even when the light deflecting means is mounted due to the problem of returning light to the light emitting point of the semiconductor laser, diffracted light from the hologram is reflected on the light receiving element. Moves in the direction along the dividing line between the light receiving portions of the light receiving element, so that it is possible to detect the light condensing characteristic on the normal information recording medium.

According to a fifth aspect of the present invention, in the optical pickup device of the first, second, third or fourth aspect, the light beam emitted from the semiconductor laser is linearly polarized light. And a し た wavelength plate in combination.

According to the optical pickup device of the present invention, the linearly polarized outgoing light beam from the semiconductor laser is deflected as P-polarized light when passing through the Wollaston prism of the light deflecting means, and circularly polarized light when passed through the quarter wavelength plate. Luminous flux. The light beam of this circularly polarized light is reflected by the information recording medium and
After passing through the wave plate, the direction of polarization of the light beam emitted from the semiconductor laser becomes a reflected light beam of linearly polarized light inclined by 180 degrees. This reflected light flux is further deflected when passing through the Wollaston prism from the opposite direction as S-polarized light. As described above, the light deflecting means having a simple configuration in which the Wollaston prism and the quarter-wave plate are combined can deflect the light beam reflected from the information recording medium.

The invention of claim 6 is the invention of claims 1, 2, 3, 4
Or an optical pickup device according to item 5, holding means for holding the information recording medium, and the light source such that the recording surface of the information recording medium moves relative to the light-converging position of the objective lens of the optical pickup device. And a driving unit for driving at least one of the information recording medium and the pickup device.

According to a sixth aspect of the present invention, in the information recording medium driving device, the information recording medium held by the holding means with respect to the condensing position of the objective lens of the optical pickup device according to the first, second, third, fourth or fifth aspect. By driving at least one of the optical pickup device and the information recording medium by driving means so that the recording surface of the medium relatively moves, in a state where there is no return light to the semiconductor laser of the optical pickup device, Information recording, information reproduction, and information erasing on an information recording medium can be performed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a perspective view illustrating a schematic configuration of an optical pickup device according to the present embodiment, and FIG. 1B is an explanatory diagram of a light beam in the device.
The optical pickup device according to the present embodiment includes a semiconductor laser 1 as a light source, a hologram element 2, a collimating lens 5, an optical isolator 6 as a light deflecting unit, an objective lens 7, and a photodiode 9 as a light receiving element. A light beam emitted from the semiconductor laser 1 passes through a hologram element 2, a collimating lens 5, and an optical isolator 6,
Optical disk 8 as information recording medium by objective lens 7
Focused on top. The light beam reflected from the optical disk 8 passes through the objective lens 7, and a part thereof is diffracted by the hologram element 2 and guided to the photodiode 9.

The optical disk 8 is not limited to a read-only optical disk, but may be any other information recording medium such as a write-once type optical disk capable of recording information only once or a rewritable type optical disk capable of recording / erasing information. There may be. In this embodiment,
A rewritable optical disk is used.

The semiconductor laser 1 emits a predetermined amount of divergent light and a linearly polarized output light beam Lo toward the hologram element 2. Light beam L emitted from the semiconductor laser 1
o is a diffraction grating 3 formed on the lower surface of the hologram element 2.
As a result, the light beam is separated into three light beams (one main beam and two sub-beams for tracking error detection), and passes through the hologram 4 formed on the upper surface of the hologram element 2 as zero-order diffracted light. The zero-order diffracted light composed of the three light beams passing through the hologram 4 of the hologram element 2 is converted into a parallel light beam by the collimator lens 5, deflected by a small angle by the optical isolator 6, and then spotted on the optical disk 8 by the objective lens 7. It is collected.

The reflected light beam from the optical disk 8 passes through the objective lens 7 in the reverse direction, is again deflected by a small angle by the optical isolator 6, and is irradiated on the hologram 4 on the upper surface of the hologram element 2 via the collimator lens 5. You. Since the hologram 4 is divided into two regions having different grating periods by the dividing line in the radial direction of the optical disk 8 as described above, a part of the reflected light beam composed of the three light beams from the optical disk 8 is further divided into two. Diffracts by dividing into two. A total of six light beams diffracted by the hologram 4 are applied to a light-receiving portion of the photodiode 9 divided into five, and an information reproduction signal (RF), a tracking error signal (TES), and a focus error signal are described later. (FES) is detected.

On the other hand, of the reflected light beam from the optical disk 8, the light beam that has passed through the hologram element 2 as the 0th-order diffracted light has been deflected by the optical isolator 6 by a small angle, so that it has shifted from the light emitting point of the semiconductor laser 1. It is collected at the position and arrives. Therefore, there is no return light condensed at the light emitting point of the semiconductor laser 1, and it is possible to prevent the generation of noise due to the return light to the semiconductor laser 1 at the time of information recording and information reproduction on the optical disk 8.

Next, a configuration example of the optical isolator 6 will be described. FIG. 2 is an explanatory diagram of the optical isolator 6 configured by combining the Wollaston prism 61 and the 波長 wavelength plate 62. This optical isolator 6 has a
The structure is such that a 波長 wavelength plate 62 is attached to the optical disk side of a Wollaston prism 61 of 6 mm (thickness) × 4 mm × 4 mm. The Wollaston prism 61 includes two wedge-shaped prisms 61a and 61b having different optical axes.
Are bonded together, and the prism 6 on the side of the semiconductor laser 1 is
The optical axis 63a of 1a is set in the vertical direction in the figure, and the optical axis 63b of the prism 61b on the optical disk 8 side is set in the direction orthogonal to the paper surface in the figure. Optical isolator 6
The outgoing luminous flux from the semiconductor laser 1 which is incident on the semiconductor laser 1 as P-polarized light (polarization direction of the electric field is parallel to the YZ plane in the figure) is an extraordinary ray (refractive index ne = 1.5474) in the prism 61a.
8), and ordinary light (refractive index no) in the prism 61b.
= 1.53856), so as shown in FIG.
= 0.075 °. The reflected light beam from the optical disk 8 passes through the quarter-wave plate 62 twice, enters the optical isolator 6 as S-polarized light (polarized light whose vibration direction of the electric field is perpendicular to the YZ plane in the figure), and In the prism 61a, an extraordinary ray (refractive index ne = 1.54748) is formed, and in the prism 61a, an ordinary ray (refractive index no = 1.53856) is formed. As a result,
The reflected light beam Lr that returns to the semiconductor laser 1 through the optical isolator 6 is inclined by θ2 = 0.15 ° (= 0.075 ° × 2) with respect to the emitted light beam Lo as shown in FIG. . Here, the focal length of the collimating lens 5 is set to 10
mm, the reflected light flux from the optical disk 8 is approximately 26 μm (= 10 mm × sin) from the light emitting point of the semiconductor laser 1.
(0.15 °)) Since the light is condensed at a shifted position, it is possible to prevent the generation of noise due to the return light. As described above, by combining the Wollaston prism and the quarter-wave plate, the optical isolator 6 for deflecting the reflected light returning from the optical disk 8 to the semiconductor laser 1 can be easily configured.

The optical isolator 6 is configured to be detachable from the optical pickup device main body of the present embodiment,
The optical isolator 6 may be mounted only when necessary. In this case, the semiconductor by the optical isolator 6 is changed so that the amount of change in the incident angle of the light beam Lo emitted from the semiconductor laser 1 to the objective lens 7 due to the mounting of the optical isolator falls within a predetermined allowable range. Laser 1
The angle of the deflection of the light beam Lo emitted from is set. For example,
Generally, the allowable value of the inclination of the light beam incident on the objective lens 7 is about 1 °. However, since the light beam incident on the objective lens 7 is inclined by about 30 minutes due to optical components other than the optical isolator 6, the optical isolator 6 does not. The angle of deflection is set to 30 minutes or less. By setting the angle of deflection by the optical isolator 6 in this way, regardless of whether the optical isolator 6 is mounted or not, the light beam Lo emitted from the semiconductor laser 1 is Lo.
Is focused on a predetermined position on the optical disk 8 by the objective lens 7, so that normal information recording and reproduction can be performed. Moreover, a hologram unit in which the semiconductor laser 1, the hologram element 2 and the photodiode 9 are integrated can be commonly used regardless of whether the optical isolator 6 is mounted or not.

When the optical isolator 6 is configured to be detachable and mounted only when necessary, when the optical isolator 6 is mounted, the diffracted light from the hologram element 2 due to the mounting of the optical isolator 6 is applied to the photodiode 9. The direction and angle of the deflection of the reflected light beam from the optical disk 8 by the optical isolator 6 are set so that the movement of the light receiving spot is in the light receiving portion of the photodiode 9 along the dividing line between the light receiving portions. With this setting, regardless of whether the optical isolator is mounted or not, the reflected light beam from the optical disk 8 is received at a predetermined position on the light receiving surface of the photodiode 9, so that normal error signal detection and information reproduction can be performed. Become. Moreover, as described above, the optical isolator 6
Regardless of the presence or absence of mounting, a hologram unit in which the semiconductor laser 1, the hologram element 2 and the photodiode 9 are integrated can be used in common.

For example, in the optical pickup device of this embodiment, the light receiving surface of the photodiode 9 is divided into five light receiving portions D1 to D5 as shown in FIGS. 3 (a), 3 (b) and 3 (c). . The light beam reflected from the optical disk 6 is diffracted by the hologram 4 on the upper surface of the hologram element 2 and
Five light receiving portions D1 of the photodiode 9 as second-order diffracted light
To D5. The hologram 4 is composed of two regions having different grating periods divided by a radial dividing line of the optical disc 8, and of the main beams in the reflected light beam, light incident on one of the regions is received by the light receiving units D2 and D3. The light incident on the other region on the dividing line is collected on the light receiving portion D4. Further, the sub-beams in the reflected light flux are condensed on the light receiving portions D1 and D5, respectively. These condensed light receiving spots S change as shown in FIGS. 3A to 3C according to the convergence state of the light beam on the optical disk 8. FIG.
(A) is a light receiving spot when the optical disk 8 is too far,
FIG. 3B shows a light receiving spot when focusing, and FIG. 3C shows a light receiving spot when the optical disk 8 is too close.

Here, each light receiving section D of the photodiode 9
When the output signals from 1 to D5 are represented by S1 to S5, the focus error signal (FES) is a so-called Foucault method (for example, G. Bouwhuis et al .: Principles of Optical Disc).
Systems, Adam Hilger Ltd., Bristol, (1985))
According to the principle, FES = S2-S3. On the other hand, the tracking error signal (TES) is detected by a three-beam method. Since the sub-beams for tracking error detection are respectively condensed on the light receiving units D1 and D5, the tracking error signal (TES) is TES = S1-S5
Given by Further, the information reproduction signal (RF) is expressed as RF =
It is given by S2 + S3 + S4.

FIGS. 4A, 4B and 4C respectively show the states of the light receiving spots focused on the respective light receiving portions of the photodiode 9 when the optical isolator 6 is mounted. 4A shows a light receiving spot when the optical disk 8 is too far, FIG. 4B shows a light receiving spot when the optical disk 8 is in focus, and FIG. 4C shows a light receiving spot when the optical disk 8 is too close. In the apparatus of the present embodiment, the light beam reflected from the optical disk 8 is deflected by about 0.15 ° with respect to the light beam emitted from the semiconductor laser 1 by the optical isolator 6, so that the focal length of the collimator lens 5 is set to 10 mm, for example.
The position of the light receiving spot on the light receiving section is about 26 μm
(= 10 mm × sin (0.15 °)). Here, the focus error signal (FES) is F
Since ES = S2−S3, the angle and direction of the deflection by the optical isolator 6 are such that the shift of the light receiving spot by the optical isolator 6 is in the light receiving section and along the dividing line of the light receiving sections D2 and D3. Is set.
With this setting, the focus error signal (FES) can be normally detected.

FIG. 5 is a schematic configuration diagram of an optical disk drive device as an information recording medium drive device provided with the optical pickup device. This optical disk drive device
In addition to the optical pickup device 10, a tray 11 as holding means for holding the optical disk 8, and a light source such that the recording surface of the optical disk 8 relatively moves with respect to a light condensing position 12 by an objective lens of the optical pickup device 10. It has a drive mechanism for the pickup device 10 and a rotation drive mechanism for rotating the optical disk 8. The tray 11 is configured to be movable in the direction of arrow A, and can take a protruding position protruding from the housing 13 where the optical disc 8 can be loaded and ejected, and an insertion position inserted into the housing 13. .
In addition, the tray 11 is provided with a spindle motor 14 as the rotation drive mechanism and the optical pickup device 10 along the shaft 15 in the radial direction of the optical disk 8 (in the direction of arrow B).
Is provided with a drive mechanism (not shown) for driving the motor.

In the optical disk drive device having the above configuration,
Since there is no return light to the semiconductor laser 1 of the optical pickup device 10, information recording, information reproduction, and information erasure on the optical disk 8 can be performed without noise due to the return light.

In the above embodiment, the Wollaston prism 61 and the と wavelength plate 62 are used as the optical isolator 6.
However, the present invention can be applied to a case where a combination of another prism such as a Rochon prism or a Senarmont prism and a quarter-wave plate is used as the optical isolator 6. is there. In particular, Roch
When an on prism or a Senarmont prism is used, the light beam emitted from the semiconductor laser to the optical disk can be deflected, but the reflected light beam returning from the optical disk can be deflected. It is no longer necessary to consider changes in

[0032]

According to the first to sixth aspects of the present invention, since there is no return light condensed at the light emitting point of the semiconductor laser, the semiconductor laser at the time of recording information on the information recording medium, reproducing information, and erasing information. There is an effect that generation of noise due to return light to the light source can be prevented.

In particular, according to the second and sixth aspects of the present invention, normal information recording,
The information can be reproduced and erased, and components other than the light deflecting means, such as a semiconductor laser, a hologram, and an objective lens, can be commonly used.

In particular, according to the third and sixth aspects of the present invention, a normal reflected light beam can be detected regardless of the presence or absence of the light deflecting means, and a semiconductor laser or hologram other than the light deflecting means can be detected. There is an effect that parts such as an objective lens can be commonly used.

In particular, according to the fourth and sixth aspects of the present invention, it is possible to detect the light condensing characteristic on a normal information recording medium irrespective of whether or not the light deflecting means is mounted, and to detect the light deflecting means. There is an effect that components such as a semiconductor laser, a hologram, and an objective lens other than the above can be commonly used.

In particular, according to the fifth and sixth aspects of the present invention, the light deflecting means for deflecting the reflected light beam which is going to return from the information recording medium to the semiconductor laser via the hologram element is provided with a Wollaston prism and a quarter wavelength. There is an effect that it can be easily configured by combining with a plate. (Hereinafter, margin)

[Brief description of the drawings]

FIG. 1A is a perspective view illustrating a schematic configuration of an optical pickup device according to an embodiment of the present invention. (B) is an explanatory view of a light beam of the device.

FIG. 2 is an explanatory diagram of an optical isolator used in the device.

FIG. 3A is an explanatory diagram of a light receiving spot when an optical disc 8 is too far in an optical pickup device without an optical isolator. (B) is an explanatory view of a light receiving spot when the optical disc in the apparatus is in focus. (C)
4 is an explanatory diagram of a light receiving spot when the optical disk is too close in the apparatus.

FIG. 4A is an explanatory diagram of a light receiving spot when an optical disc 8 is too far in an optical pickup device equipped with an optical isolator. (B) is an explanatory view of a light receiving spot when the optical disc in the apparatus is in focus. FIG. 3C is an explanatory diagram of a light receiving spot when the optical disc is too close in the apparatus.

FIG. 5 is a schematic configuration diagram of an optical disk drive device according to an embodiment of the present invention.

FIG. 6 is a perspective view showing a schematic configuration of a conventional optical pickup device.

FIG. 7 is an explanatory diagram of a light beam of the device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Hologram element 3 Diffraction grating 4 Hologram 5 Collimating lens 6 Optical isolator 7 Objective lens 8 Optical disk 9 Photodiode 10 Optical pickup device 11 Tray 12 Focusing position 13 Housing 14 Spindle motor 15 Shaft

Claims (6)

[Claims] 1. A light beam emitted from a semiconductor laser enters an objective lens via a hologram, is focused on an information recording medium by the objective lens, and a reflected light beam from the information recording medium is transmitted through the objective lens. In an optical pickup device which is incident on the hologram, diffracts the light by the hologram, and guides the light to a light receiving element, light deflecting means for deflecting a light beam reflected from the information recording medium is provided between the semiconductor laser and the objective lens. An optical pickup device, characterized in that: 2. The optical pickup device according to claim 1, wherein said light deflecting means is mountable, and said light beam emitted from said semiconductor laser is incident on said objective lens by mounting said light deflecting means. An optical pickup device characterized in that the angle of deflection by the light deflecting means is set so that the amount of change within the range falls within a predetermined allowable range. 3. The optical pickup device according to claim 1, wherein said light deflecting means is mountable, wherein a light receiving spot on said light receiving element of a diffracted light from said hologram by mounting said light deflecting means. An optical pickup device characterized in that the angle of deflection by the light deflecting means is set so that the movement of the light is within the range of the light receiving section. 4. A light receiving element having a plurality of light receiving portions is used as the light receiving element, and a light receiving spot moving in a direction intersecting a dividing line of the light receiving portion is detected to detect a light condensing characteristic on the information recording medium. 4. The optical pickup device according to claim 3, wherein the movement of the light receiving spot of the diffracted light from the hologram on the light receiving element by attaching the light deflecting means is in a direction along the dividing line. An optical pickup device wherein the direction of deflection by the light deflection means is set. 5. The optical pickup device according to claim 1, wherein the light beam emitted from the semiconductor laser is linearly polarized light, wherein the light deflecting means comprises a Wollaston prism, a quarter-wave plate, An optical pickup device comprising a combination of the above. 6. An optical pickup device according to claim 1, 2, 3, 4 or 5, holding means for holding an information recording medium, and said information recording medium with respect to a focusing position of an objective lens of said optical pickup device. An information recording medium driving device, comprising: an optical pickup device and driving means for driving at least one of the information recording medium so that the recording surface of the information recording medium relatively moves.