JPS58194151A - Optical pickup device - Google Patents

Abstract

PURPOSE:To attain stable optical characteristics, by providing the entire optical system including a laser light source to a moving section of an optical pickup device. CONSTITUTION:A support shaft hole having a length nearly equal to the total axial length of the entire optical pickup is piercedly arranged at the center of device. A hole 32 having a cross section as shown in a figure is pierced through a support shaft 31 intersecting a ray axis of laser light placed between the semiconductor laser 11 functioning as the laser light source and a polarized light beam splitter 10 of the optical system. The path of laser light of the semiconductor laser 11 is formed through this hole 32. The laser light from the beam splitter 10 is projected on a disc D through an objective lens 7. The reflecting light from the disc D reaches a photodetector 14 through the beam splitter 10. Since the pickup is used always at the best point of the lens as positioned at first in this way, the stable optical characteristics are attained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical pickup device used, for example, in an optical video disc playback device, and in particular, the present invention relates to an optical pickup device used, for example, in an optical video disc playback device, and in particular, an objective lens is arranged along two axes: an optical axis direction (focus direction) and a tracking direction perpendicular thereto. The present invention relates to an optical pickup device that is driven in a direction.

Generally, an optical playback device, especially an optical video disc playback device, includes a focusing control mechanism for driving and controlling an objective lens (convergent lens) in the optical axis direction of the optical system, and a focusing control mechanism in a direction perpendicular to the optical axis direction. A tracking control mechanism is required to drive and control the objective lens. The former is an optical recording medium (hereinafter referred to as a disk) on which information such as video signals and audio signals is recorded.

) The upper surface of the disc is used to correctly focus the light beam for reading the information, and the latter is used to correctly follow the information track recorded spirally or concentrically on the upper surface of the disk. .

By the way, the movable parts of conventional optical pickup devices include
Only an objective lens, or only an objective lens and a tracking mirror such as a galvanometer mirror is provided, and a laser light source such as a semiconductor laser or gas laser is provided in a separate member, such as the chassis of an optical video disc playback device. .

In this case, the relative position of each optical element changes due to the above-mentioned focusing control and tracking control of the optical pickup device, which complicates the configuration for making the laser beam incident on the disk at the optimal focused state and track position. There are drawbacks such as the characteristics easily changing, the optical field of view being narrow, and the lens having to remove off-axis aberrations, which increases the lens cost.

The present invention eliminates such conventional drawbacks, and by providing the entire optical system including the laser light source in the movable part of the optical pickup device, it is possible to change the relative positions of the optical components from the laser light source to the objective lens. It is possible to drive without
The optical axis and optical path length of the entire optical system are kept constant, and each lens is always used at the best point positioned at the beginning, resulting in stable optical characteristics and an infinite optical field of view. In addition, it not only reduces the lens cost by eliminating the need to remove aberrations outside the optical axis of the lens, but also makes it easier to reduce the overall thickness of the optical pickup device, making it possible to stably support the movable parts within the device. The purpose of the present invention is to provide an optical pickup device that can perform the following operations.

That is, the feature of the optical pink-up device according to the present invention is that the objective lens, the 1/4 wavelength plate, the collimating lens, and the polarizing beam splitter are held in a movable member that is slidably supported on the support shaft. , this movable member is provided with a first coil and a second coil, and the first coil (
A current corresponding to the focus error signal is supplied to the second coil, and a current corresponding to the tracking error signal is supplied to the second coil. Objective lens, 17
A four-wavelength plate, a collimator lens, and a polarizing beam splitter are arranged in a line in a direction parallel to the support axis, and the weight of the movable member is adjusted around the support axis for each optical member arranged in the -row. A laser light source such as a semiconductor laser is disposed at substantially symmetrical positions, and a hole is bored in the support shaft to form a laser light path from the laser light source.

Next, prior to a detailed description of the present invention, an optical pickup device that is a prior art of the present invention will be described with reference to FIGS. 1 to 3.

1 to 3 show an example in which the two-dimensional drive device previously proposed by the applicant is applied to an optical disc playback device, and FIG. 1 is a plan view, and FIG. 2 is a plan view. 1
3 is a cross-sectional view taken along the line ■--l in FIG. 1. FIG. In each of these figures, a movable member 1 made of a non-magnetic material consists of a bobbin and a holder 1B, and a tubular bearing member fitted in the axial direction is located at the center of the holder 1B. 2 is provided. Further, a focusing control drive coil (hereinafter referred to as a focus coil) 3 is wound around the outer peripheral surface of one bobbin of the movable member 1 so as to form a ring around the bearing member 2. Two sets of tracking control drive coils (hereinafter referred to as trunking coils) 4A and 4B are provided closely on the surface of the coil. Each of the tracking coils 4A and 4B has a winding axis direction perpendicular to the winding axis direction of the focus coil 3, and forms a total of four rings arranged on the outer peripheral surface of one bobbin. There is.

Next, in the holder 1B of the movable member 1, a stepped hole 5 parallel to the central axis of the bearing member 2 is provided at a position eccentric to the central axis of the bearing member 2.
A lens barrel 6 is attached to the hole 5. Inside this lens barrel 6, an objective lens 7, a 1/4 wavelength plate 8,
and a collimating lens 9 are provided, and the optical axes of these optical components are arranged parallel to the central axis of the bearing member 2. Further, a polarizing beam splitter 10 is attached to the lower end side of the hole 5 in FIG.

Next, the laser light source, for example, the semiconductor laser 11,
゛The objective lens 7.1 is centered around the central axis of the movable member 1.
It is disposed at a position substantially symmetrical in terms of weight with the optical components of the 74-wavelength plate 8, collimator lens 9, and polarizing beam splitter 10, and is attached to one of the movable members 1, for example, a bobbin. Laser light from the semiconductor laser 11 is guided to the polarizing beam splitter 10 via the space between the holder 1B and one bobbin. Furthermore, a photodetector 14 whose detection surface is directed toward the polarization beam subrick 10 is attached to the lower bobbin 1A of the polarization beam splitter 10 in FIG.

In the movable member 1 configured in this way, the support shaft 16 is planted and fixed at the center of the fixed yoke 15 made of magnetic material toward the bottom in FIG. 2, and is guided and inserted into the center hole of the bearing member 2. Thus, it is supported so as to be slidable and rotatable, that is, to be slidable in the axial direction of the support shaft 16 and rotatable around the shaft. Furthermore, an annular permanent magnet 18 is closely fixed to the lower surface of the fixed yoke 15 in FIG. A first yoke part 20 having a piece 19 is fixed. Further, the fixed yoke 15 includes a first yoke portion 20.
A second yoke portion 21 is disposed inside one bobbin, facing the projecting piece portion 19, and projects downward in FIG. 2 (to the right in FIG. 3). These fixed yokes 15
, a permanent magnet 181, a first yoke part 20, and a second yoke part 21 constitute a magnetic circuit, and a focus coil 3 is formed in the magnetic gap between the first yoke part 20 and the second yoke part 21. and tracking carp/L, 4A, 4B
will be placed. Furthermore, the fixed yoke 15 has a holding body 1
A hole 22 having a diameter larger than the outer diameter of the lens barrel 6 held by B is bored, and the upper end of the lens barrel 6 is guided and inserted into this hole 22.

To explain the operation of the optical system built in the optical pink-up device as the prior art of the present invention configured as described above, the linearly polarized laser beam emitted from the semiconductor laser 11 is polarized beam beam. After being reflected by the flick 10, it is collimated by a collimator lens 9, and this collimated laser beam passes through a quarter-wave plate 8 and is converted into a circularly polarized laser beam.

This converted laser beam is made incident onto the surface of the disk D by the objective lens 7.

The rotation direction of the polarization plane of the reflected circularly polarized laser beam reflected by the disk surface of the disk D is opposite to the rotation direction of the polarization plane of the circularly polarized laser beam that is incident on the disk surface of the disk D. Therefore, the linear polarization plane of the reflected laser light beam that passes through the quarter-wave plate 8 and is converted into a linearly polarized wave is the same as that of the laser light beam from the semiconductor laser 11 that is incident on the quarter-wave plate 8. The plane of polarization differs by 90° compared to the plane of linear polarization.

Therefore, the laser beam reflected from the surface of the disk D passes straight through the polarizing beam splitter 10 and is incident on the photodetector 14. The photodetector 14 detects the light intensity distribution of the reflected laser beam, and based on this, a read information signal, a focus error signal, a tracking error signal, etc. are generated by a signal processing circuit (not shown).

Next, the driving operation of the optical system including the objective lens 7 will be explained. When a focus control drive signal is supplied to the focus coil 3 in response to a focus error signal, a current having a polarity and magnitude corresponding to the focus control drive signal flows through the focus control coil 3, and the focus coil 3 is the first yoke part 20 and the second yoke part 2
1 from the magnetic field in the magnetic gap formed between the two. As a result, the objective lens 7 housed in the lens barrel 6 attached to the holder 1B, the 1/4 wavelength plate 8, the collimator lens 9, the polarizing beam splitter 10 fixed to the holder 1B, and the semiconductor laser. 1
1 is moved as a whole while maintaining their respective positional relationships, and the objective lens 7 is moved toward or away from the surface of the disk D, thereby performing predetermined focus control.

In addition, when a tracking control drive signal is supplied to the tracking coils 4A, 4B in response to a tracking error signal, a current with a polarity and magnitude corresponding to the tracking control drive signal is supplied to the tracking coils 4A, 4B.
, and from the magnetic field of the magnetic gap between the projecting piece 19 of the first yoke part 20 and the second yoke part 21, each tiger knocking coil 4A, 4B moves to the right about the support shaft 16. Since the optical axis of the lens barrel 6, that is, the optical axis of the objective lens 7, is mounted in a direction centered, the optical axis of the lens barrel 6, that is, the optical axis of the objective lens 7, is moved in the direction across the signal trunk of the disk D (in the direction of arrow t or 1 in FIG. 1), and tracking control is performed.

Further, when the focus control drive signal is supplied to the focus coil 3 and the tracking control drive signal is supplied to the tracking coils 4A and 4B, focus control and tracking control are performed simultaneously.

In this example, the laser light beam from the laser light source 11 passes through the objective lens assembly in a round-trip manner and forms an optical path to the photodetector 14.The relative position of each optical element is controlled by orcus control and tracking control. This has the advantage that the positional relationship does not change. In addition, since the best point of each lens positioned initially is always used, the optical characteristics are not only stable, but the optical field of view can be expanded to infinity. Furthermore, there is no need to remove off-axis aberrations, resulting in lower lens costs.

By the way, in an optical pickup device including such an entire optical system, the movable parts are heavy, so it is important to arrange the optical components in a well-balanced manner. That is, as shown in FIGS. 1 to 3, the semiconductor laser 11, which is the heaviest component, and the lens barrel 6, which is equipped with a lens system,
It is necessary to arrange the polarizing beam brick 10 at symmetrical positions with respect to the support shaft 16, which is the center of sliding rotation. Therefore, the length of the support shaft 16 needs to be short so as not to obstruct the optical path between the semiconductor laser 11 and the polarizing beam splitter 10, and the length of the bearing section 2 is also shortened. .

In this way, if the length of the support@16 or the bearing part 2 in the axial direction is short, the supporting state tends to become unstable, and especially when trying to make the entire optical pickup device thinner, the above-mentioned As the length becomes even shorter, it is more likely to get caught during sliding, rotation, etc., causing multiple resonances, and reducing the accuracy of drive control.

Taking these points into consideration, the optical pickup device according to the present invention has a support shaft 31 having a length that spans almost the entire axial length of the entire device and penetrates through the center of the device, as shown in FIG. The semiconductor laser 1 which is the laser optical axis is
A hole 32 having the cross-sectional shape shown in FIG. A laser light path is formed.

That is, in FIG. 4, the movable member 1 supported slidably on the support shaft 31 is composed of a pohin 1A and a holder 1B, and the holder 1B has an l lens γ, a 174 wavelength plate 8, A collimating lens 9 and a polarizing beam splitter 10 are held, and a focus coil 3 as a first coil and tracking coils 4A and 4B as second coils (see FIG. 1) are provided on one bobbin. 3 and the tracking coils 4A and 4B respectively in accordance with the tracking error signal. , the objective lens 7 is parallel to the axial direction of this support shaft 31.
．． A quarter-wave plate 8, a collimator lens 9, and a polarizing beam splitter 10 are arranged in a row, and objective lenses 7.1/
A semiconductor laser 11 as a laser light source is disposed at a position of the movable member 1 that is approximately symmetrical in terms of weight with respect to the optical lens system consisting of the four-wavelength plate 8, collimator lens 9, and polarizing beam splitter 10, and the semiconductor laser 11 as a laser light source is mounted on the support shaft 3H. As shown in FIG. 5, a hole 32 is formed to form a path for the laser beam from the semiconductor laser 11, and the laser beam from the semiconductor laser 11 is transmitted through the hole 32 into the polarized light of the optical system. I am trying to lead to Beams Brick 10. In this case, holding body 1B
The support shaft 31 also has a bearing portion 35 integrally formed with the support shaft 31.
Needless to say, a hole 36 that serves as a laser beam path is formed at a position corresponding to the hole 32. The other configurations are the same as those of the optical pink-up device shown in FIGS. 1 to 3, and corresponding parts are designated by the same reference numerals and explanations will be omitted.

According to such an optical pickup device as an embodiment of the present invention, the axial length of the support shaft 31 and the bearing portion 35 can be made approximately twice as long as in the case of the prior art. The sliding movement of the movable member 1 with respect to the support shaft 31 is performed stably, and the occurrence of catching during this sliding movement is extremely rare, and focus control and tracking control can be performed with high precision. Also, around the support shaft 31, an objective lens 7, a quarter wavelength plate 8, a collimating lens
49 and the optical lens system consisting of the polarized beam subric 10 and the like, and the semiconductor laser 11 are disposed at substantially symmetrical positions in terms of weight, so the weight balance of the movable member 1 is good, and the axial direction Allows for stable sliding and rotation around an axis. Furthermore, a semiconductor laser 11 as a laser light source
The entire optical system including
Since it is slidingly driven with respect to 1, the objective lens γ is always
The center of the lens coincides with the optical axis, and the lens is always used at the best point of the initially positioned lens, so the characteristics are stable, the optical field of view can be made infinite, and there is no need to remove off-axis aberrations. Of course, it has various advantages such as low lens cost.

Note that the present invention is not limited to the above-mentioned embodiments. For example, the bobbin 1A of the movable member 1 and the holder 1B may be formed integrally, or the bearing portion 35 may be formed as a separate member. It's okay. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

1 to 3 show an optical pickup device as a prior art used to explain the present invention, in which FIG. 1 is a plan view, FIG. 2 is a sectional view taken along the line ■-■ in FIG. The figure is a sectional view taken along the line T in FIG. 1. 4 and 5 show an embodiment of the present invention, with FIG. 4 being a sectional front view and FIG. 5 being a cross-sectional view of the hole portion of the support shaft in FIG. 4. 1・・・・・・・・・・・・・・・Movable member 1A・
・・・・・・・・・・・・・・・Bobbin 1B・・・・・・
......Holding body 3...
...Focus coil 4A, 4B...
Tracking coil 7・・・・・・・・・・・・・・・
・・・Objective lens 8・・・・・・・・・・・・・・・
・・1/4 wavelength plate 9・・・・・・・・・・・・・・・・
・・Collimator lens 10・・・・・・・・・・・・・
...Polarizing beam splitter 11...
... Semiconductor laser 14 ......
・・Photodetector 31・・・・・・・・・・・・Support shaft 32・・・・・・・・・・・・・Hole-35・・・
......Bearing section 36...
...... Hole No. 1 ml No. 3 g

Claims (1)

[Claims] A movable member slidably supported with respect to a support shaft holds an objective lens, a quarter-wave plate, a collimator lens, and a polarizing beam splinter, and a first coil and a second coil are provided on this movable member. , supplies a current according to the focus error signal to the first coil and a current according to the tracking error signal to the second coil, respectively, and supplies a current according to the focus error signal to the first coil, and a support shaft that supports the movable member in a slidable manner. The objective lens, optical/four-wave plate, collimating lens, and polarizing beam subric are arranged in a row in a direction parallel to the support axis at eccentric positions, and each optical member arranged in the -row is A laser light source is disposed at substantially symmetrical positions in terms of weight with respect to the support shaft, and a hole is bored in the support shaft to form a laser light path from the laser light source. pickup device.