JP3967525B2 - Lens drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lens driving device that drives a lens that focuses a light beam on an information recording surface of an optical information recording medium.
[0002]
[Prior art]
In recent years, various optical heads for recording information on an optical information recording medium using a high-density substrate (polycarbonate, PC material with a refractive index of 1.59 and a thickness of 100 μm) have been proposed.
[0003]
In this type of optical head, when a light beam is collected by a hemispherical lens and an objective lens and irradiated onto an optical recording medium, both lenses are moved in parallel or orthogonal to the optical axis by a biaxial actuator. Servo is performed by. It is known that the spherical aberration caused by the change in the film thickness of the cover glass of the optical recording medium is eliminated by moving the hemispherical lens in the optical axis direction, and the aberration can be reduced.
[0004]
A biaxial actuator of such a two-group lens (numerical aperture NA: 0.8 or more) composed of a hemispherical lens and an objective lens is shown, for example, in FIG. 1 of Japanese Patent Application Laid-Open No. 11-110794. The lens driving device shown in FIG. 1 of Japanese Patent Application Laid-Open No. 11-110794 has the following characteristics (refer to FIG. 1 of Japanese Patent Application Laid-Open No. 11-110794 for reference numerals in parentheses below).
[0005]
1. The hemispherical lens (4) and the objective lens (3) are held by a bobbin (8) to which a focus servo coil (9) wound around an outer peripheral surface is fixed, and an elastic support member (10) comprising four leaf springs. Is supported by.
[0006]
2. The objective lens (3) is held by a bobbin (13) to which a spherical aberration correction coil wound around an outer peripheral surface is fixed, and is supported by an elastic support member (15) including four leaf springs. A yoke and a permanent magnet (12) are provided on the bobbin (8) at opposite positions, and only the bobbin (13) holding the objective lens (3) moves in the optical axis direction with respect to the bobbin (8). It is like that.
[0007]
[Problems to be solved by the invention]
However, the lens driving device disclosed in Japanese Patent Application Laid-Open No. 11-110794 has the following problems.
[0008]
That is, firstly, the phase characteristic that approximates the value of m1 / m2 to the coefficient α is good, but because the yoke and permanent magnet are mounted, m2 is large, and m1 and the holder holding the objective lens are both large, and the focus sensitivity is high. There is a problem that it decreases.
[0009]
here,
m1: The weight of the member made of the bobbin (13) on which the objective lens (3) is fixed on the spherical aberration correction coil wound around the outer peripheral surface.
[0010]
m2: The hemispherical lens (4) and the objective lens (3) are members made of a yoke (8) provided on a permanent magnet (12) and a yoke on which a focus servo (9) wound around an outer peripheral surface is fixed. weight.
[0011]
That is, the weight of the member consisting of the bobbin (8) which is a movable member provided on the yoke and the permanent magnet (12) increases (because the yoke and permanent magnet are mounted), and the focus sensitivity is poor. If a movable member consisting of the bobbin (13) is arranged in the bobbin (8), mutual interference of focus drive occurs, and control becomes uneasy.
[0012]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lens driving device that is small and lightweight and can improve focus sensitivity.
[0013]
[Means for Solving the Problems]
The lens driving device of the present invention is a lens driving device that drives a lens that irradiates a light beam from a light source onto an information recording surface of an optical information recording medium. The first lens device is disposed on the optical axis of the light beam. First lens driving means for driving the lens in the optical axis direction of the light beam, and a second lens disposed on the same optical axis as the first lens, and the optical axis direction of the light beam and the optical A second lens driving means for driving in a direction crossing a track of the information recording medium, a base member for holding the first lens driving means and the second lens driving means independently and movably, and the base A permanent magnet that is provided on the member and generates a common magnetic flux for the first lens driving unit and the second lens driving unit, and the first lens driving unit is shared by the permanent magnet. Magnetism A first focus coil provided on a first holding member for holding the first lens disposed in the first lens, and the second lens driving means is disposed in a common magnetic flux by the permanent magnet. In addition, it is composed of a second focus coil and a tracking coil provided on a second holding member for holding the second lens.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
1 to 7 relate to a first embodiment of the present invention, FIG. 1 is a development view showing a configuration of an objective lens driving device, and FIG. 2 is a sectional view showing a cross section including the objective lens and hemispherical lens of FIG. 3 is a diagram showing the configuration of the light receiving element of the tilt detector of FIG. 2, and FIG. 4 is the configuration of a tilt control circuit that controls the tilt correction coil based on the detection signal from the light receiving element of the tilt detector of FIG. 5 is a developed view showing a configuration of a modified example of the objective lens driving device of FIG. 1, FIG. 6 is a diagram showing a modified example of the permanent magnet of FIG. 1, and FIG. 7 is a lens holder for the hemispherical lens of FIG. It is a figure which shows the modification of the supporting member to do.
[0016]
As shown in FIGS. 1 and 2, the objective lens driving device 1 according to the present embodiment includes an objective optical system that focuses a light beam on a signal recording surface of an optical information recording medium 2 such as an optical disk or a magneto-optical disk. Is used in an optical head for recording and / or reproducing information signals with respect to the optical information recording medium 2.
[0017]
The objective optical system includes a second lens (hereinafter referred to as an objective lens) 3 on which light from a light source is incident, and a first light that is condensed on the signal recording surface of the optical information recording medium 2 via the objective lens 3. A lens (hereinafter referred to as a hemispherical lens 4), that is, a semiconductor laser (not shown), a photodetector, and the like are integrated by a mirror 6 provided on the bottom surface portion of the base 5 whose both ends are bent at an upper right angle. Light from the fixed optical system is reflected and guided to the objective optical system.
[0018]
The hemispherical lens 4 is held by a lens holder 4a, and the lens holder 4a is supported by a suspension spring (suspension spring having a thickness of 0.5 mm or less of stainless steel plate) as a support member at a position passing through the lens principal point surface of the hemispherical lens 4. It is supported. The base end of the suspension spring 7 is fixed to the upper part of the first end 5a bent at a right angle above the base 5, and the hemispherical lens 4 is moved in the focusing direction to a part 7a on the fixed side of the suspension spring 7. A part 8b of the inner surface of the hemispherical lens focus coil 8 is fixed with an adhesive.
[0019]
Further, the objective lens 3 is held by a lens holder 9, and the lens holder 9 is supported by two support members (rectangular, hexagonal column cross-section, for example, metal wires) 10 at positions passing through the lens principal point surface of the objective lens 3. It has been. A hollow portion 9a is provided on the first end portion 5a side of the lens holder 9, and a focus coil 11 that moves the objective lens 3 to the focus and an objective lens 3 that moves in the tracking direction on the inner surface of the hollow portion 9a. A first tracking coil 12a and a second tracking coil 12b, and the objective lens 3 is moved in the radial or tangential direction in order to adjust the tilt between the optical axis of the objective optical system and the optical information recording medium 2. Is provided with a pair of tilt correction coils 13a and 13b that are driven to rotate about the axis, and the hollow portion 9a is supported by the two I-shaped yokes 14a and 14b inserted from the bottom surface of the base 5 and separated. It is supported by the member 10 and is screwed to the substrate 15 via the outer yoke 5a.
[0020]
A pair of tilt correction coils 13 c and 13 d for rotating the objective lens 3 about the radial direction or the tangential direction is provided at the tip of the lens holder 9. The tilt correction coils 13 c and 13 d are provided on the bottom surface of the base 5. Two I-shaped yokes 16a and 16b that are more standing are inserted and held.
[0021]
A permanent magnet 17 is bonded and fixed to each of the first end portion 5a and the second end portion 5b bent at a right angle above the base 5 facing the first end portion 5a. The lens focus coil 8, the focus coil 11, the first tracking coil 12a, the second tracking coil 12b, and the tilt correction coils 13a, 13b, 13c, and 13d are disposed in the common magnetic flux.
[0022]
In the common magnetic flux, the hemispherical lens focus coil 8 that moves the hemispherical lens 4 in the optical axis direction, and the objective lens 3 can be tilt-corrected with respect to the optical axis direction, radial (disk radius), and the principal point of the objective lens. The tilt correction coils 13a, 13b and 13c, 13d are located in the magnetic gap between the permanent magnet 17 and the yoke 14.
[0023]
The upper part of the second end 5b is bent at a right angle, and a tilt detector 19 for detecting tilt is provided on the upper surface of the bent part. That is, optical information is obtained with respect to the optical axis connecting the objective lens 3 and the hemispherical lens 4 in the tangential (track direction) and radial direction (disc radial direction) of the objective optical system by the tilt detector 19 integrated with the light source and the photodetector. A tilt which is a relative angle error with respect to the signal recording surface of the recording medium 2 is detected.
[0024]
As shown in FIG. 3, the tilt detector 19 is composed of light receiving elements 19a, 19b, 19c, and 19d of a four-divided photodetector, and is output to a tilt control circuit 21 as shown in FIG. That is, in the tilt control circuit 21 shown in FIG. 4, the outputs of the light receiving elements 19a and 19b are added to the adder 22a, the outputs of the light receiving elements 19a and 19c are added to the adder 22b, and the outputs of the light receiving elements 19b and 19d are added to the adder 22c. The outputs of the light receiving elements 19c and 19d are connected to the adder 22d, respectively. Further, the outputs of the adders 22a and 22d are connected to a subtracter 23a, and the outputs of the adders 22b and 22d are connected to a subtractor 23b. The outputs of the subtractor 23a and the subtracter 23b are connected to subtractors 24a, 24b, 24c, and 24d.
[0025]
When the outputs of the light receiving elements 19a, 19b, 19c, and 19d are a, b, c, and d by the tilt control circuit 21, 2 (bc) from the subtractor 24a and 2 (a from the subtractor 24b. -D), 2 (da) is output from the subtractor 24c, and 2 (cd) is output from the subtractor 24d. The outputs of the subtractors 24a, 24b, 24c, and 24d are the tilt correction coils 13a, 13b, 13c, 13d.
[0026]
As a result, the radial tilt control and the tangential so as to eliminate the relative angular error between the optical information recording medium 2 and the optical axis of the objective optical system in an arbitrary track in synchronization with the rotational speed of the optical information recording medium 2. Tilt control is performed continuously.
[0027]
In the tilt detection, the tilt of the objective lens with respect to the optical information recording medium 2 may be detected directly from the offset amount of the tracking error signal.
[0028]
As described above, according to the present embodiment, the focus sensitivity can be improved by independently controlling the focus and tracking of the hemispherical lens 4 objective lens 3 in a common magnetic flux, and the mutual stability is eliminated and the control is stable. Can be increased.
[0029]
Further, the tilt correction in the tangential direction can be performed only by the objective lens 3, and the coma aberration on the surface of the optical information recording medium 2 can be suppressed to be small.
[0030]
Further, when the tilt correction coil is not used, the inner yoke 14 is made up of a single plate that stands on the bottom surface, and the total reflection mirror 6 is directly joined and fixed at 45 degrees on the base 5 as shown in FIG. It can be constituted as follows.
[0031]
Further, as shown in FIG. 6, a pair of permanent magnets 25a magnetized differently in the thickness direction and a single permanent magnet 25b magnetized in the thickness direction are joined to the outer yoke 5b with an adhesive. .
[0032]
The permanent magnets 25a and 25b are the same surface, and the inner yoke 14 is erected on the opposing surface. There is a gap (gap) between the inner yoke 14 and the permanent magnet 25, and the plate of the outer yoke 5b. The surface and the angled inner yoke 14 are joined.
[0033]
Further, it is fixed to the suspension spring 7 that supports the lens holder 4a of the hemispherical lens 4 shown in FIG. The shape of the fixed hemispherical lens focus coil 8 is symmetrical so as to straddle the boundary line of the pair of permanent magnets 25a, and has a square shape.
[0034]
Further, the first and second tracking coils 12a and 12b shown in FIG. 2 are symmetrical and have a square shape so as to straddle the edge of the end face of the permanent magnet 25b.
[0035]
When the hemispherical lens focus coil 8 is formed in a square shape, the two magnets 25a and 25b may be bonded together to form the permanent magnet 17 (when two sets are used, the gap portion 26 is eliminated in FIG. 6). And just two sheets together).
[0036]
Further, as shown in FIG. 7, instead of the suspension spring 7, the lens holder 4 a of the hemispherical lens 4 may be supported by two wire-like support members 27 in the lens principal point plane of the hemispherical lens 4. In this case, since the weight of the hemispherical lens 4 including the lens holder 4a is reduced, the focus sensitivity can be further improved.
[0037]
The outer surface of the hemispherical lens on the optical information recording medium 2 side is roughened by etching or the like with the outer peripheral surface of the outside of the optical path as a surface roughness of 0.5 or more (for example, an average surface roughness of 1.0 micron). ) A pigment may be mixed in the epoxy resin on the surface to cover the light absorption layer. In this way, stray light of diffracted light reflected from the optical information recording medium 2 can be suppressed.
[0038]
Further, instead of a hemispherical lens, an optical probe composed of a hole provided by opening a minute opening in a conical or quadrangular pyramid shape on a Si (silicon) substrate as shown in FIG. 1 of JP-A-2000-82234, for example. It may be used.
[0039]
FIGS. 8 to 10 relate to the second embodiment of the present invention, FIG. 8 is a diagram showing a configuration for detecting the relative position between the objective lens and the hemispherical lens, and FIG. 9 is a configuration of a modification of FIG. FIGS. 10 and 10 are plan views each including the light source and the photodetector of FIG.
[0040]
Since the second embodiment is almost the same as the first embodiment, only different points will be described, and the same components are denoted by the same reference numerals and description thereof will be omitted.
[0041]
As shown in FIG. 8, in the present embodiment, the hemispherical lens 4 is driven in two directions of the optical axis and the disk radius with respect to the optical information recording medium 2, so that the hemispherical lens 4 has an outer peripheral surface on the lens holder 4a. A focus coil 31 and a tracking coil 32 are stacked to face each other. For this reason, the lens holder 4 a is supported by four wires (metal wires) 33.
[0042]
When performing focus control or tracking control on the information track with the light beam emitted from the hemispherical lens on the optical recording medium, it is necessary to maintain the relative positions in the optical axis direction and the direction perpendicular to the optical axis.
[0043]
Therefore, a light source (LED) 38 and a photodetector 34 having a plurality of light receiving regions (for example, four divisions) are fixed to a part of the lens holder 9 of the objective lens 4. On the other hand, a reflecting plate 35 is bonded to the surface of the lens holder 4 a of the hemispherical lens 4 facing the photodetector 34.
[0044]
The light beam emitted from the light detector 34 on the lens holder 9 of the objective lens 3 is reflected by the reflecting plate 35 on the lens holder 4a holding the hemispherical lens, and the light beam is received on the light detector 34. The position in two directions can be detected by the output of each light receiving element.
[0045]
Further, since the distance between the objective lens and the hemispherical lens is narrow, it is more preferable to use a capacitance sensor instead of an optical sensor.
[0046]
Note that the hemispherical lens 4 may be configured to detect the relative position of the hemispherical lens 4 and the objective lens 3 when focus and tracking control is performed as shown in FIG. That is, a light source (LED) 38 and a photodetector 34a having PDs 36 and 37 made up of, for example, three-divided light receiving areas are provided on the base 5, and a part of the lens holder 9 is opened, and a surface near the opening of the lens holder 9 and Reflector plates (reflection hologram lenses) 35a and 35b having a lens function of diffracting and condensing are provided on the surface of the lens holder 4a facing the opening.
[0047]
At this time, the light source 38 and the light detector 34a are configured as shown in FIG. 10, and the outputs of the three regions 36A, 36B, and 36C of the light source (for example, LED) 38 and PD 36 are A, B, and C at the center. If the outputs of the three regions 37a, 37b, and 37c are a, b, and c, the position detection signal of the objective lens 3 is (A + C) −B, and the position detection signal of the hemispherical lens 4 is (a + c) −b. Become. Accordingly, the relative position between the objective lens 3 and the hemispherical lens can be detected as (a + c) −b− (A + C) + B.
[0048]
With the configuration as shown in FIG. 9, it is not necessary to provide a light detector in the lens holder 9 which is a movable part, so that the wiring process can be performed easily.
[0049]
11 and 12 relate to a third embodiment of the present invention. FIG. 11 is a cross-sectional view showing a configuration of the objective lens driving device. FIG. 12 is a cross-sectional view showing a configuration of a modification of the objective lens driving device in FIG. FIG.
[0050]
Since the third embodiment is almost the same as the second embodiment, only different points will be described, and the same components are denoted by the same reference numerals and description thereof will be omitted.
[0051]
In the present embodiment, the second lens (hereinafter referred to as a collimator lens) is controlled in the optical axis direction, and the first lens (hereinafter referred to as a two-group lens in which the hemispherical lens and the objective lens are integrated) is aligned in the optical axis direction. This is an example of controlling in a direction perpendicular to the optical axis direction.
[0052]
Specifically, as shown in FIG. 11, the optical head body 100 includes a semiconductor laser 101, a quarter-wave plate 102, a polarization beam splitter 104 joined with a cylindrical lens 103, a photodetector 105, and a diffraction grating 106. Has been.
[0053]
A hologram unit in which the semiconductor laser 101, the quarter-wave plate 102, the polarization beam splitter 104 to which the cylindrical lens 103 is bonded, the photodetector 105, and the diffraction grating 106 are integrated can also be used.
[0054]
The light beam emitted from the semiconductor laser 100 passes through the diffraction grating 106, the polarization beam splitter 104, and the quarter wavelength plate 102. The linearly polarized light separated into three beams by the diffraction grating 106 becomes circularly polarized light when transmitted through the quarter-wave plate 102. Then, the light beam passes through the collimator lens 110 to become a parallel light beam, is converged by the objective lens 3, passes through the hemispherical lens 4, and is irradiated onto the track of the optical information recording medium 2.
[0055]
The light beam reflected on the track of the optical information recording medium 2 passes through the hemispherical lens 4, the objective lens 3, and the collimator lens 110 and enters the quarter-wave plate 102. The light beam that has passed through the quarter-wave plate 102 becomes linearly polarized light and is reflected by the polarization beam splitter 104. The reflected light beam passes through the cylindrical lens 103 and is received by the photodetector 105.
[0056]
Focus control and tracking control of the objective lens 3 are performed by the output of the photodetector 105. Further, focus control of the collimator lens 110 is performed in order to reduce spherical aberration that causes a reduction in the reproduction signal, and position detection of the collimator lens 110 in the optical axis direction is performed by the position detector 111 provided in the base 5. .
[0057]
The position detector 111 is composed of an LED as a light source and a photodetector consisting of two-divided light reception. A holder 110a for holding the collimator lens 110 is provided with a reflector 112, and the base 5 and the collimator of the objective lens driving device 1 are provided. The position of the lens 110 relative to the holder 110a can be detected.
[0058]
In addition, a conical projection 115 is provided below the base 5 of the objective lens driving device 1 for driving the second group lens (integration of the hemispherical lens 4 and the objective lens 3), and the optical head body that receives the projection 115 A cylindrical hole 116 is provided on the 100 side, and the protrusion 115 and the cylindrical hole 116 are in contact with each other with a line on the circumference, and the angle adjustment with the optical information recording medium 2 is performed by three screws 117 (one in the figure). Are fixed with an adhesive after adjustment according to FIG.
[0059]
A lens holder 4a (made of a plastic material) having a small outer diameter of the hemispherical lens 4 and a lens holder 9 (made of a plastic material) having a large outer diameter of the objective lens 3 are attached to the adhesive portion 119 after positioning between the optical axis and both lenses. Are joined. At this time, a convex portion is formed in the lens holder 4a that holds the hemispherical lens 4 with the concave portion formed in the lens holder 9 of the objective lens 3 and is in a fitted state.
[0060]
On the lens holder 9 of the objective lens 3, a collimator lens 110 side is provided with a counter balance 120 formed integrally with a protrusion. The counter balance 120 may join metal pieces with an adhesive.
[0061]
Although the lens holder 9 of the objective lens 3 is supported by an elastic support member 121 made of two wires, it may be supported by four non-parallel wires.
[0062]
Also in this embodiment, the same operations and effects as in the first embodiment can be obtained.
[0063]
Note that the second group lens (integration of the hemispherical lens 4 and the objective lens 3) may be as shown in FIG. That is, in FIG. 12, a silicon substrate (or ceramic substrate) 133 having a tapered recess 131 supporting the hemispherical lens 4 on the upper surface and a tapered recess 132 supporting the objective lens 3 on the lower surface is used. Then, the hemispherical lens 4 is bonded and fixed to the recess 131 and the objective lens 3 is fixed to the recess 132, respectively. At this time, the hemispherical lens 4 and the objective lens 3 are fixed in a line contact state at points a and b in the figure.
[0064]
The silicon substrate (or ceramic substrate) 133 is accommodated and fixed in a hollow engineering plastic material 135 supported by a support member 134 made of four metal wires.
[0065]
Examples of the engineering plastic material 135 include PPS (polyphenylene sulfide) and LCP (liquid crystal polymer) which are thermoplastic resins containing a fiber filler. The coefficient of thermal expansion of this PPS is 2-3 × 10 ^-Five The coefficient of thermal expansion of LCP is 5 × 10 ^-Five On the other hand, the thermal expansion coefficient of the silicon substrate 133 used in the configuration of FIG. ^-6 It is.
[0066]
Therefore, by configuring as shown in FIG. 12, since the thermal expansion coefficient of the silicon substrate 133 is smaller than the thermal expansion coefficient of the plastic material 135, it is possible to suppress a change in the distance between the objective lens 3 and the hemispherical lens 4 due to a temperature change. it can.
[0067]
In the configuration of FIG. 12, the outer peripheral surfaces of the objective lens 3 and the hemispherical lens 4 are partly brought into line contact with the inner peripheral surfaces of the tapered recesses 131 and 132 formed in the silicon substrate 133. Positioning in the vertical direction with respect to the direction and adjustment of the tilt of the lens can be easily performed.
[0068]
FIG. 13 is a cross-sectional view showing a configuration of an objective lens driving device according to the fourth embodiment of the present invention.
[0069]
Since the fourth embodiment is almost the same as the first embodiment, only different points will be described, and the same components are denoted by the same reference numerals and description thereof will be omitted.
[0070]
In the present embodiment, a first drive device integrated with a hemispherical lens that moves a collimator lens for correcting an error in substrate thickness in the optical axis direction, and a first objective lens in the optical axis direction and the optical axis direction. And an optical information recording medium made of an existing substrate having a thickness of 1.2 mm and a substrate for high-density recording (a polycarbonate material having a thickness of 100 μm). In order to ensure compatibility with the formula information recording medium, the third driving device for moving the second objective lens in the optical axis direction and in the direction perpendicular to the optical axis direction is composed of a common magnetic circuit composed of a plurality of permanent magnets. This is an example.
[0071]
Specifically, as shown in FIG. 13, the existing optical system and the optical system of the present embodiment are integrated, and the configuration of the optical system of the present embodiment is a semiconductor arranged in an optical body. A laser 151, a photodetector 152 that receives reflected light from the optical information recording medium 2, and a hologram element 153 that separates the forward and backward paths of the light beam.
[0072]
The light beam emitted from the semiconductor laser 151 passes through the hologram element 153, becomes a parallel light beam at the collimator lens 154, converges at the first objective lens 3, passes through the hemispherical lens 4, and passes through the optical information recording medium 2 surface. Irradiate.
[0073]
If no collimator lens is used, the light beam emitted from the semiconductor laser 151 is transmitted through the hologram element 153, converged by the first objective lens 3, and transmitted through the hemispherical lens 4 to the surface of the optical information recording medium 2. Irradiate.
[0074]
The light beam reflected from the surface of the optical information recording medium 2 passes through the hemispherical lens 4, the first objective lens 3, and the collimator lens 154 and enters the hologram element 153. The primary light beam diffracted by the hologram element 153 is received by the photodetector 152.
[0075]
On the other hand, the configuration of the existing optical system includes a semiconductor laser 160 disposed in the optical body, a second objective lens 161 that focuses the light beam on the optical information recording medium 2, and the optical information recording medium 2. It comprises a photodetector 162 that receives reflected light, a hologram element 163 and a collimator lens 164 that separate the forward and backward paths of the light beam.
[0076]
A second driving device that moves the integrated hemispherical lens 4 and the first objective lens 3 in the optical axis direction and a direction perpendicular to the optical axis direction, and the second objective lens 161 in the optical axis direction and the optical axis direction. The configuration of a common magnetic circuit composed of a plurality of permanent magnets of the third driving device moving in the perpendicular direction is as follows.
[0077]
That is, the integrated hemispherical lens 4, the first objective lens 3, and the second objective lens 161 are both holders 171 and 172 held by an engineering plastic material (for example, PPS) and a plurality of support members (the cross section is rectangular) (Not shown). Further, focus and tracking coils 173 and 174 are fixed to the outer peripheral surfaces of the holders 171 and 172 with an adhesive.
[0078]
The collimator lens 154 is also supported by a holder 175 held by a PPS material and a plurality of support members (a plate spring having a rectangular cross section: not shown). Further, only the focusing coil 176 is fixed to the outer peripheral surface of the holder 175 with an adhesive.
[0079]
A plurality of permanent magnets 180 are fixed to the inner peripheral surface parallel to the optical axis with an adhesive on the base 5 made of a magnetic material at a position facing the focus and tracking coils 173 and 174. As described above, the outer yoke and the inner yoke (not shown but similar to the first embodiment) are common, and the entire driving device is downsized.
[0080]
In the optical information recording / reproducing apparatus provided with the objective lens driving device of the present embodiment, although not shown, first, an optical information recording medium composed of an existing substrate having a thickness of 1.2 mm and a substrate for high-density recording ( The optical information recording medium 2 is identified in the case of a polycarbonate material having a thickness of 100 μm.
[0081]
That is, a disc-shaped optical information recording medium 2 (hereinafter referred to as a disc) is placed on a turntable, and the first objective lens 3 and the second objective lens 161 are provided by a feed drive mechanism not shown. When moving to the circumferential side, the existing semiconductor laser emits light by detecting the signal from the position detector at the innermost circumference (in this case, if the disk 2 is dedicated for reproduction, the disk rotation stops and the disk 2 is recorded and reproduced) If possible, it is the desired number of revolutions).
[0082]
Next, the second objective lens 161 is searched in the direction of the optical axis, and the driving device that monitors the focus error signal with the photodetector is operated. The substrate thickness is identified from the monitor output signal.
[0083]
When the disk 2 is an existing substrate having an existing thickness of 1.2 mm, the semiconductor laser 160 emits light. Then, by monitoring the tracking error signal with the photodetector 152, the tracking control operation is performed on the track on the recording medium as it is, and a standby state is entered.
[0084]
On the other hand, when the disk 2 is a high-density recording substrate (polycarbonate material having a thickness of 100 μm), the semiconductor laser 151 on the high-density side emits light. Then, the hemispherical lens 4 and the first objective lens 3 are searched in the optical axis direction, the focus error signal is monitored by the photodetector 152, and the driving device is operated. At this time, the collimator lens 154 is electrically held at a predetermined (intermediate position). Further, focus and tracking control is started by the first driving device of the hemispherical lens 4 and the first objective lens 3, and aberration correction due to the substrate thickness error from the measured value of the jitter amount from the RF signal is not shown. ) In which the aberration due to the error of the substrate thickness is obtained, and the optical axis direction of the collimator lens 154 is controlled by the amount of aberration. As a result, the control is continued with the jitter amount being the minimum value.
[0085]
When the substrate thickness varies greatly as described above, the substrate thickness is identified by an objective lens having a long working distance (WD), so that the protective layer on the medium surface or the SIL lens is damaged by the contact between the hemispherical lens 4 and the disk 2. Suppresses the occurrence of
[0086]
【The invention's effect】
As described above, according to the present invention, the first lens and the second lens are driven by providing a permanent magnet that generates a common magnetic flux for the first lens driving unit and the second lens driving unit. It is small and lightweight, and there is an effect that the focus sensitivity can be improved.
[Brief description of the drawings]
FIG. 1 is a development view showing a configuration of an objective lens driving device according to a first embodiment of the present invention.
2 is a cross-sectional view showing a cross section including the objective lens and hemispherical lens of FIG. 1;
3 is a diagram showing a configuration of a light receiving element of the tilt detector of FIG. 2;
4 is a diagram showing a configuration of a tilt control circuit that controls a tilt correction coil based on a detection signal from a light receiving element of the tilt detector of FIG. 3;
FIG. 5 is a development view showing a configuration of a modified example of the objective lens driving device of FIG. 1;
6 is a view showing a modification of the permanent magnet of FIG.
7 is a view showing a modified example of a support member that supports the lens holder of the hemispherical lens in FIG. 1;
FIG. 8 is a diagram showing a configuration for detecting a relative position between an objective lens and a hemispherical lens according to a second embodiment of the present invention.
9 is a diagram showing a configuration of a modified example of FIG.
10 is a diagram showing a plan view of the light source and the photodetector shown in FIG. 9;
FIG. 11 is a cross-sectional view showing a configuration of an objective lens driving device according to a third embodiment of the present invention.
12 is a cross-sectional view showing a configuration of a modified example of the objective lens driving device in FIG. 11;
FIG. 13 is a sectional view showing the structure of an objective lens driving device according to a fourth embodiment of the invention.
[Explanation of symbols]
1 ... Objective lens driving device
2 ... Optical information recording medium
3 ... Objective lens
4 ... Hemispherical lens
4a, 9 ... Lens holder
5 ... Base
6 ... Mirror
7 ... Suspension spring
8 ... Focus coil for hemispherical lens
10: Support member
11 ... Focus coil
12a ... first tracking coil
12b ... second tracking coil
13a, 13b, 13c, 13d ... Tilt correction coil
14a, 14b, 16a, 16b ... Yoke
15 ... Board
17, 18 ... Permanent magnet
19 ... Tilt detector

Claims (4)

In a lens driving device that drives a lens that irradiates a light beam from a light source onto an information recording surface of an optical information recording medium,
First lens driving means for driving a first lens disposed on the optical axis of the light beam in an optical axis direction of the light beam;
Second lens driving means for driving a second lens disposed on the same optical axis as the first lens in the optical axis direction of the light beam and in a direction crossing a track of the optical information recording medium;
A base member for holding each of the first lens driving means and the second lens driving means independently and movably;
A permanent magnet that is provided on the base member and generates a common magnetic flux for the first lens driving unit and the second lens driving unit;
The first lens driving means includes a first focus coil provided on a first holding member that holds the first lens disposed in a common magnetic flux generated by the permanent magnet,
The second lens driving means includes a second focus coil and a tracking coil provided on a second holding member that holds the second lens disposed in a common magnetic flux generated by the permanent magnet. A lens driving device. The second lens driving means has at least one pair of inner yokes;
A pair of tilt correction coils for correcting an inclination between the optical axis of the light and the information recording surface of the optical information recording medium, which is inserted through the pair of inner yokes in a common magnetic flux generated by the permanent magnet. The lens driving device according to claim 1, wherein: The center of rotational driving that is supported on the outer surface of the second holding member in a plane parallel to the optical axis of the second lens and that is accompanied by at least tangential tilt correction by the pair of tilt correction coils. The lens driving device according to claim 2, further comprising a supporting unit provided on the base member with the main point surface of the second lens as a principal point plane. The lens driving apparatus according to claim 1, further comprising a position detection unit configured to detect a relative position between the first lens and the second lens.

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