JPS6120058B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an objective lens driving device used in an optical information reading device.

For example, in a video or audio disk reproducing device, it is necessary to perform focusing so that the reading light beam is properly focused on the disk surface, and to perform tracking so that the light beam follows a track on the disk. What is important in this case is how to perform focusing and tracking based on these signals after obtaining signals for focusing and tracking by an appropriate method.

Various methods have been proposed for such focusing and tracking. In most of these conventional methods, a galvanometer mirror is placed in the optical path of the reading beam,
Tracking is performed by supplying a tracking signal to this to swing the light beam in a tracking direction perpendicular to the track. For this reason, in conventional video or audio disc playback devices, the reading light beam passes obliquely to the optical axis of the objective lens during the tracking operation, so even in such cases, the light beam is In order to achieve correct focusing, it is necessary to use a large objective lens that has no spherical aberration or astigmatism. Therefore, it is difficult to design the objective lens, the configuration is complicated, and the weight increases, making it difficult to provide good frequency characteristics and damping characteristics to the control system that drives the objective lens for focusing, and the drive device The disadvantage is that it is large and complicated.

In addition, in order to eliminate the above-mentioned drawbacks, there is also a system in which the objective lens is supported so as to be displaceable in the tracking direction via an elastic member such as a leaf spring, and the objective lens is driven in the tracking direction by a tracking drive means. Proposed. but,
This type of objective lens driving device has the problem that accurate tracking cannot be performed because the signal for driving the objective lens in the tracking direction and the amount of displacement of the objective lens do not have a linear relationship. One conceivable way to solve this problem is to detect the position of the objective lens in the tracking direction and perform motional feedback control of tracking based on this. Conventionally, it has not been possible to accurately detect the position of the objective lens in the tracking direction. In addition, in a configuration in which the objective lens is supported by an elastic member and driven in the tracking direction,
When the entire optical head, including the objective lens drive device, is moved in the disk radial direction to access a predetermined position, an inertial force acts on the elastic member in the opposite direction to the direction of movement, and this causes the movement. The objective lens vibrates during the process, and a similar phenomenon occurs even when the machine is stopped. This has the disadvantage that high-speed and accurate access becomes difficult.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks, to provide an objective lens driving device that can control the movement of an objective lens in the tracking direction with high precision, has a simple configuration, is small and lightweight.

The present invention provides an objective lens driving device having a tracking drive means for driving an objective lens in a tracking direction substantially orthogonal to an information track in order to read information recorded on a recording medium, in which one direction as viewed from the tracking direction of the objective lens is provided. first and second signal generating means for generating signals that increase and decrease, respectively, in accordance with the amount of displacement in the other direction, and decrease and increase, respectively, in accordance with the amount of displacement in the other direction; position detection means for detecting the position of the objective lens in the tracking direction based on the output signal of the signal generation means, and the displacement of the objective lens in the tracking direction is controlled by the tracking drive means in accordance with the output of the position detection means. The invention is characterized in that it is configured to be controlled.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an example of an optical information reading device including an objective lens driving device according to the present invention. In this example, a video disc playback device is shown. The disk 1 is mounted on a turntable 3 fixed to a rotating shaft 2a of a motor 2, and rotates at a predetermined rotational speed. In this embodiment, video information is recorded on the disk 1 by forming concave and convex pits 1a in which information is encoded in a spiral or concentric shape. Therefore, in this example, a so-called reflective video disk reproducing apparatus is shown, which reproduces video information by receiving the reflected light from the pit 1a of the reading light beam. An objective lens drive device 4, which will be described later, is placed opposite to the surface of the disk 1 on which the pits 1a are formed. The objective lens driving device 4 includes an objective lens 5, and controls the movement of the objective lens 5 in a focusing direction parallel to the optical axis and in a tracking direction perpendicular thereto and perpendicular to the direction of the track forming the pit 1a. , focusing is performed to accurately focus the reading light beam onto the track, and tracking is performed to accurately follow the track. In this example, tracking uses two tracking light beams different from the reading light beam, and these two tracking light beams are focused through the objective lens 5 to connect light points on both sides of the track. . These three light beams, the reading light beam and the tracking light beam, can be obtained from independent light sources, but in this example, the laser light from one laser light source 6 is projected onto the hologram plate 7, and the 0th order diffracted light beam is , ±1st-order diffracted light beams are obtained, and these three light beams are guided to the objective lens 5 via the beam splitter 8.

The objective lens driving device 4 directs the three light beams to
As described above, the disk 1 is scanned in the radial direction while focusing on a predetermined position on the disk 1. The three reflected lights from the disk 1 pass through the objective lens 5 and the beam splitter 8 and enter three light converters 9, 10 and 11, respectively. Here, the reflected light from the pit 1a is incident on the optical converter 9, and a video information component is derived from the output terminal 12, and this video information component is also supplied to the amplifier 13. The amplifier 13 compares this video information component with a predetermined reference value, detects the deviation, that is, a focusing error signal, and sends this signal to the focusing control circuit 14 and the amplifier 15.
The light is then supplied to the objective lens driving device 4 for focusing. At this time, the amount of movement of the objective lens 5 in the optical axis direction by the objective lens driving device 4 is detected, and this is input to the control circuit 14 to control focusing by motional feedback. Further, the reflected light of the tracking light beam on the disk surface is incident on optical converters 10 and 11, respectively, and converted into electrical signals, which are each supplied to a differential amplifier 16. Differential amplifier 16
compares the output signals of the optical converters 10 and 11, detects the difference signal, that is, a tracking error signal, and supplies this signal to the objective lens drive device 4 via the tracking control circuit 17 and amplifier 18 to perform tracking. Let them do it. Further, at this time, the amount of movement of the objective lens 5 from a predetermined position, for example, a neutral position, in the tracking direction by the objective lens driving device 4 is detected by first and second signal generating means, which will be described later. By supplying the detection output to the differential amplifier 84, the objective lens 5
A signal regarding the position in the tracking direction is obtained, and this signal is input to the control circuit 17 to perform motional feedback control of tracking.

Next, the configuration of an example of the objective lens driving device described above will be explained with reference to FIGS. 2, 3, and 4. Fig. 2 is a plan view of the objective lens driving device 4 viewed from the optical axis direction of the objective lens 5, Fig. 3 is a cross-sectional view taken along line A-A' in Fig. 2, and Fig. 4 is the same. A cross-sectional view taken along the line B-B' is shown. The objective lens 5 is attached to a cylindrical holding tube 20. This holding cylinder 20 is connected to a coil bobbin 23 by two leaf springs 21 and 22. Note that the leaf springs 21 and 22 or the lens holding cylinder 20 are made of a magnetic material. These two leaf springs 21 and 22 do not bend in the direction perpendicular to the plane of the paper, that is, in the direction of the optical axis in FIG. move to. A coil 24 is wound around the coil bobbin 23, and magnets 25 are arranged to sandwich the bobbin 23 from the inside and outside. magnet 2
Holes 27 and 28 through which the leaf springs 21 and 22 pass are formed in the inner cylinder portion 26 of 5, so that the coil bobbin 23 and the lens holding cylinder 20 can freely move in the optical axis direction. The coil bobbin 23 is attached to a frame 30 that holds the magnet 25 via a leaf spring 29 that is substantially symmetrical with respect to the optical axis, for example, shaped like a spider. Note that this leaf spring 29 can also be formed into a spiral shape or a leaf spring extending in the radial direction. Therefore, if a focusing error signal (current) is supplied to the coil 24 as explained in FIG. 1, the coil bobbin 23 and the lens holding cylinder 20 move together in the optical axis direction, and focusing is performed. Further, in this example, at least one piezoelectric element 31 is attached to the leaf spring 29, thereby detecting an electric signal corresponding to the deformation of the leaf spring 29, that is, the amount of movement of the objective lens 5 in the optical axis direction. This is the first
The signal is supplied to a focusing control circuit 14 shown in the figure to perform motional feedback control of the focusing operation. In this way, focusing can be performed accurately.

Next, a mechanism related to tracking will be explained. Two electromagnets 32 and 33 are provided on the inner surface of the inner cylinder portion 26 of the magnet 25 to face each other. These electromagnets 3
2 and 33, a tracking error signal is supplied as shown in FIG. Therefore, the electromagnet 32,3
If a tracking error signal (current) is supplied to either one of 3, the magnetic force generated by this acts on the magnetic leaf spring 21 or 22 or the magnetic holding cylinder 20 and is attracted to it. Tracking is then performed by moving the lens holding cylinder 20 in a tracking direction perpendicular to the focusing direction and the track direction of the disk 1 (see FIG. 1). In addition, in this example, as shown in FIGS. 2 and 4, piezoelectric elements 35 and 36 as first and second signal generating means are attached to the leaf springs 21 and 22, respectively, so that the leaf spring 21 Electric signals corresponding to the deformation, that is, the amount of movement of the objective lens 5 in the tracking direction are obtained, and these signals are differentially amplified by a differential amplifier 84 as shown in FIGS. By obtaining a signal regarding the position in the tracking direction and supplying this signal to the tracking control circuit 17, the tracking operation is controlled by motional feedback. Note that when the objective lens 5 moves in one direction in the tracking direction, the output of one piezoelectric element increases and the output of the other decreases, and vice versa when the objective lens 5 moves in the tracking direction. The output of one piezoelectric element is decreased and the output of the other is increased.

In this way, by differentially amplifying the outputs of the piezoelectric elements 35 and 36, the position of the objective lens 5 in the tracking direction can be detected with high accuracy, and motional feedback control can be performed based on the differential output. This allows accurate tracking. In addition, according to the leaf springs 21 and 22 of this embodiment, since the lens holding cylinder 20 moves linearly in the tracking direction while rotating, more accurate tracking can be performed.

In the embodiment described above, the objective lens 5 includes two leaf springs 21 and 22 for tracking, which are arranged symmetrically with respect to the optical axis, and a leaf spring 2 for focusing, which is also approximately symmetrical in shape with respect to the optical axis.
9 and is held so as to be elastically movable in a predetermined direction. Therefore, even if a vibration system in the direction perpendicular to the direction of the optical axis and the tracks on the disk, which is made up of a movable part for tracking, is placed on top of a vibration system in the optical axis direction, which is made up of a movable part for focusing, This has the advantage that undesirable vibrations are less likely to occur, and the drive device can be made more compact. Also,
Since a galvanometer mirror is not used for tracking control, a compact, lightweight, and inexpensive regeneration device can be realized.

Next, another embodiment of the objective lens driving device of the present invention will be described.

FIG. 6 shows the electromagnet 3 in the embodiment described above.
2, 33, piezoelectric elements 37, 38 and 39, 40 are attached to leaf springs 21, 22 so as to sandwich them in a sandwich-like manner, respectively.
Tracking control is performed by these piezoelectric elements 37, 38, 39, and 40. That is, in FIG. 6, for example, a tracking error signal (voltage) is supplied to the outer piezoelectric elements 38 and 40 via the tracking control circuit 17 and the amplifier 18, and the piezoelectric elements 38 and 40 are
40 is vibrated in a tracking direction perpendicular to the optical axis and the track direction of the disk 1. At this time, the inner piezoelectric elements 37 and 39 are connected to the lens holding tube 2.
In other words, since the objective lens is deformed according to the movement of the objective lens, the electrical signals corresponding to the deformation are compared by the differential amplifier 84, and the output signal is sent to the tracking control circuit 17.
The tracking servo is performed by feeding back to the As described above, in this embodiment, the piezoelectric element is used to perform tracking drive and tracking servo.
Therefore, the leaf springs 21, 22 or the lens holding cylinder 20 do not necessarily need to be made of magnetic material.

In the above-mentioned embodiments, the tracking error signal is detected using two tracking light beams, but in this way, the objective lens is minutely vibrated by a piezoelectric element and the reading is performed without using the tracking light beam. Tracking control can also be performed by detecting a tracking error signal from the reflected light of the optical beam. An example of such a configuration will be described below.

FIG. 7 shows a second objective lens driving device 4.
In the drive device having the structure shown in the figure, piezoelectric elements are attached to two leaf springs for tracking so as to sandwich them in a sandwich-like manner, as shown in FIG. 6. In this way, the objective lens driving device 4 used in this embodiment is
Since it is symmetrical with respect to the optical axis, FIG. 7 diagrammatically shows only the movable part for tracking including one leaf spring 21, and the configuration of the movable part for focusing and its control are the same as those in the above-mentioned embodiment. Since it is the same as that, the explanation will be omitted. A voltage source 42 is connected to the piezoelectric element 41 outside the leaf spring 21, and a voltage of a constant amplitude and a constant frequency f (much lower than the frequency of video information) is applied to the holding tube 20 that supports the objective lens. The laser beam from the laser light source 6 is transmitted through the beam splitter 8 and the objective lens 5 (second
(see figure) and then focused onto the disk 1. Therefore, the light spot of the reading light beam on the disk 1 vibrates minutely as the objective lens 5 vibrates.

The light beam reflected on the disk 1 passes through an objective lens 5 and a beam splitter 8 to a light converter 4.
3. At this time, as shown in FIG. 8A, if the reading light beam accurately follows the track as shown by the arrow, the voltage source from the optical converter 43 shown in FIG. Output signal (current) modulated at twice the frequency of 42
is obtained. Further, as shown in FIG. 8C, if the reading light beam does not follow the track, output signals with different amplitudes are obtained from the optical converter 43.

In FIG. 7, the output signal of the optical converter 43 is amplified by an amplifier 44. The amplified electrical signal is
Video information processing circuit 45 and synchronous detection circuit 46
is supplied to The video information processing circuit 45 extracts only the video information component from the signal from the amplifier 44 and outputs it to the output terminal 47. Also,
The synchronous detection circuit 46 detects a frequency component based on the vibration of the piezoelectric element 41 as shown in FIG. 8B and D from the supplied signal, and also generates a tracking error signal from this signal and a reference signal during normal tracking. The error signal is detected and supplied to the tracking control circuit 17. The tracking control circuit 17 processes the tracking error signal, supplies a current corresponding to the error signal to the electromagnet 32 via the amplifier 18, and moves the lens holding tube 20 (objective lens) in the tracking direction via the leaf spring 21. In addition to having them perform tracking,
An electric signal corresponding to the deformation of the leaf spring 21 based on this movement, that is, the amount of movement of the objective lens, is transmitted to the piezoelectric element 48 attached to the inside of the leaf spring 21 and the leaf spring (not shown) facing the leaf spring 21. The tracking is obtained from a piezoelectric element (not shown) attached to the inside and compared by the differential amplifier 84 as explained in FIG. 6 to control the tracking operation by motional feedback. This allows tracking control to be performed smoothly.

FIG. 9 shows an objective lens drive device 4 using a structure similar to that of the drive device shown in FIG. Tracking control is performed similarly to the embodiment shown in the figure. Therefore, in this embodiment as well, the objective lens driving device 4 is symmetrical with respect to the optical axis, so in FIG. 9, only the movable part for tracking including the leaf spring 21 is diagrammatically shown as in FIG. 7. The same reference numerals as those shown in FIG. 7 have the same functions. That is, in this embodiment, the voltage source 42 is connected to the piezoelectric element 50 attached to the leaf spring 21 in the same way as shown in FIG. Then, the tracking error signal is detected by the synchronous detection circuit 46, and then passed through the tracking control circuit 17 and the amplifier 18.
An electromagnet 32 moves the objective lens to perform tracking. At this time, the piezoelectric element 50 is deformed and vibrates minutely due to the tracking operation by the electromagnet 32. Therefore, from this piezoelectric element 50, an electric signal is obtained on which a signal corresponding to the deformation thereof, that is, the amount of movement of the objective lens is superimposed. In this embodiment, this electrical signal is supplied to the detection circuit 52 via the amplifier 51, where the piezoelectric element 50
A signal corresponding to the deformation of is extracted, and this signal is a signal corresponding to the deformation of a piezoelectric element (not shown) attached to a leaf spring (not shown) facing the leaf spring 21 obtained by a similar method. and the differential amplifier 84
The signal is then supplied to the tracking control circuit 17 for motional feedback control of tracking. Thereby, tracking control can be performed smoothly.

As described above, according to the present invention, the elastic member that holds the objective lens movably in the tracking direction is provided with two piezoelectric elements that generate signals in opposite directions according to the movement in the tracking direction, and the piezoelectric elements generate signals in opposite directions. Since the position of the objective lens in the tracking direction is detected based on the obtained signal, the position can be detected with high precision, and this makes it possible to easily control the movement of the objective lens in the tracking direction with high precision. , and a small and lightweight objective lens driving device can be realized.

It should be noted that the present invention is not limited to the above-mentioned example, and can be modified or changed in many ways.
For example, in the embodiments shown in FIGS. 1 to 6,
In order to obtain a tracking error signal, two tracking light velocities were used in addition to the reading light beam, but instead of using the tracking light beam, components at both ends of the reflected light of the reading light beam were converted to separate optical converters. It is also possible to obtain a tracking error signal by inputting the signal into the input signal and extracting the difference between these outputs. In addition, in the objective lens drive device shown in Fig. 2, a piezoelectric element for tracking control is provided on one side of each of the two leaf springs for tracking, but it is possible to provide a piezoelectric element on both sides of one of the leaf springs to create a bimorph structure. Also good.

Furthermore, the mechanism for holding the objective lens movably in the focusing direction and the tracking direction is shown in FIGS. 10 and 11 in addition to the above-described embodiments.
With the configuration shown in the figure, it is possible to stably move only in a predetermined direction without tracking movement in an undesired direction. That is, the 10th
The objective lens driving device 4 shown in the figure is shown in FIG.
The coil bobbin 58 is held in the holding frame 57 by two spider-shaped leaf springs 55 and 56, as shown in the cross-sectional views taken in the optical axis direction along the line X-X' in FIG. Two leaf springs 59 are attached to this bobbin 58 in a direction perpendicular to the optical axis.
and 60 support the objective lens 61 and the lens holding cylinder 62. Further, the coil bobbin 58 is extended in the optical axis direction, a coil 63 is wound around this part, and a magnet 64 is arranged to sandwich this part, and focusing control is performed by passing a current corresponding to the focusing error signal to the coil 63. At the same time, a piezoelectric element (not shown) is attached to at least one side of the leaf springs 55 and 56, and the focusing operation is controlled by motional feedback based on an electric signal obtained from the piezoelectric element. In this way, in this embodiment, since the leaf springs for focusing are provided at the upper and lower parts of the lens holding tube 62, when the lens holding tube 62 moves in the optical axis direction, the optical axis of the objective lens 61 can be effectively prevented from tilting. In addition, when tracking control uses electromagnets, the plate springs 59 and 60 are made of magnetic material, and the plate springs 59 and 60 are opposed to each other,
and the electromagnet 6 facing each other via the lens holding cylinder 62.
5 and 66, and for example, two piezoelectric elements (not shown) are attached to the leaf springs 59 and 60 as first and second signal generating means to perform motional feedback control. Note that if the electromagnets 65 and 66 are not used, the sixth
As shown in the figure, piezoelectric elements can be attached to both sides of a tracking leaf spring to perform tracking drive and feedback control.

The objective lens driving device 4 shown in FIG.
As shown in FIG. 1A is a cross-sectional view taken along the optical axis, and FIG. 11B is a cross-sectional view taken along line XI-XI' in FIG. It is supported on a coil bobbin 74 by two leaf springs 72 and 73 arranged parallel to the optical axis and facing each other across the optical axis. This coil bobbin 74
is supported by a magnet 77 via spider-like leaf springs 75 and 76 attached to its upper and lower ends, respectively, and has a cylindrical portion 78 sandwiched between the magnets 77, and a coil 79 is wound around this portion. In this objective lens driving device 4, focusing is performed by supplying a current corresponding to the focusing error signal to the coil 79 to drive the objective lens 70.
A piezoelectric element (not shown) attached to at least one of the leaf springs 75, 76 moves the leaf springs 75, 76 in the optical axis direction, and sends an electric signal corresponding to the amount of movement, that is, the deformation of the leaf springs 75, 76. This electrical signal can be obtained from the focusing control system and sent motion feedback to the focusing control system to achieve high precision. Tracking can also be achieved by attaching a piezoelectric element (not shown) to two leaf springs 72 and 73 installed in the optical axis direction, and by the action of the piezoelectric element without using an electromagnet, as shown in FIG. In this manner, the objective lens 70 can be moved in a direction perpendicular to the optical axis and the direction of a track (not shown) on the disk, and the movement can be controlled by motional feedback. In addition, when using electromagnets, as shown in FIG. , magnetic members 82 and 83 may be provided on the lens holding cylinder 71. In this case, the tracking control using the piezoelectric element
This embodiment is similar to the embodiment shown in FIG.

Furthermore, in the embodiments described above, when an electromagnet is used for tracking control, the leaf spring facing the electromagnet is made of a magnetic material. Only the magnetic material may be used. Further, the lens holding cylinder portion facing the electromagnet may be made of a magnetic material. In this way, especially in the embodiment shown in FIG.
There is no need to paste.

Furthermore, in the above-described embodiments, a reflective type video disk reproducing apparatus has been described, but the present invention is a so-called transparent type video disk reproducing apparatus that detects video or audio information and/or focusing and tracking control signals from transmitted light from a recording member. It can also be effectively applied to a type of optical information reading device.

Furthermore, in the above-described embodiment, the focusing leaf spring and the bobbin that supports the objective lens via the tracking leaf spring are relatively rotatable, so that the focusing leaf spring can rotate during the focusing operation. It is also possible to configure the bobbin so that its position does not change even if the bobbin is slightly rotated around the optical axis.Also, as a leaf spring for focusing, it is possible to use a shape that does not rotate during the focusing operation, for example. A strip-shaped parallel leaf spring can also be used in the same way as a tracking leaf spring.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an example of an optical information reading device equipped with an objective lens driving device according to the present invention, and FIG. 2 is a plan view showing the configuration of an example of the objective lens driving device shown in FIG. , Figure 3 shows A- in Figure 2.
A sectional view taken along line A', Figure 4 is also a sectional view taken along line B-B',
FIG. 5 is a schematic diagram of the tracking control system, FIGS. 6 and 7 are diagrams showing other embodiments of the objective lens driving device of the present invention, and FIGS.
B, C, and D are diagrams showing the normal tracking state and abnormal tracking state, respectively, and the respective output currents of the optical converter in these states in the embodiment shown in FIG. 7, and FIG. A line diagram showing still another embodiment of the lens driving device, FIG. 10A is a plan view showing the configuration of still another example of the objective lens driving device of the present invention, and FIG. -X' line sectional view, Figure 11A
11B is a sectional view showing the configuration of still another example of the objective lens driving device of the present invention, and FIG.
It is a sectional view taken along the line XI-XI'. DESCRIPTION OF SYMBOLS 1... Disk, 1a... Pit, 4... Objective lens drive device, 5... Objective lens, 6... Laser beam,
8... Beam splitter, 9, 10, 11... Optical converter, 13... Amplifier, 14... Focusing control circuit, 15... Amplifier, 16... Differential amplifier, 17...
Tracking control circuit, 18... Amplifier, 20... Lens holding tube, 21, 22... Leaf spring, 23... Coil bobbin, 24... Coil, 25... Magnet, 29... Leaf spring, 31... Piezoelectric element, 32, 33... Electromagnet, 3
5, 36... piezoelectric element, 37, 38, 39, 40...
Piezoelectric element, 41, 48... Piezoelectric element, 42... Voltage source, 43... Optical converter, 44... Amplifier, 45... Video information processing circuit, 46... Synchronous detection circuit, 50... Piezoelectric element, 51... Amplifier, 52... Detection circuit, 55,
56...Plate spring, 58...Coil bobbin, 59,60
... Leaf spring, 61... Objective lens, 62... Lens holding tube, 63... Coil, 64... Magnet, 65, 66... Electromagnet, 70... Objective lens, 71... Lens holding tube,
72, 73...Plate spring, 74...Coil bobbin, 7
5, 76... Leaf spring, 77... Magnet, 79... Coil,
80, 81... Electromagnet, 82, 83... Magnetic member,
84...Differential amplifier.

Claims (1)

[Claims] 1. In an objective lens driving device having a tracking drive means for driving an objective lens in a tracking direction substantially perpendicular to an information track in order to read information recorded on a recording medium, displacement of the objective lens in one direction as seen in the tracking direction. first and second signal generating means that generate signals that increase and decrease, respectively, in accordance with the amount of displacement in the other direction, and that generate signals that decrease and increase, respectively, in accordance with the amount of displacement in the other direction; position detection means for detecting the position of the objective lens in the tracking direction based on an output signal, and configured to control displacement of the objective lens in the tracking direction by the tracking drive means in accordance with the output of the position detection means. An objective lens driving device characterized by: