JPH0748266B2 - Objective lens drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device for condensing a light beam emitted from a light source and drivingly displacing an objective lens for irradiating the signal recording surface of an optical recording medium such as an optical disc as a beam spot. .

[0002]

2. Description of the Related Art Conventionally, an optical disc recording and / or reproducing apparatus using an optical disc which is an optical recording medium as a recording medium records an information signal on the optical disc or reproduces an information signal recorded on the optical disc. An optical pickup device is used in. This optical pickup device is provided with an objective lens so that a light beam emitted from a light source such as a semiconductor laser is focused on a signal recording surface of an optical disc and irradiated. This objective lens
The light beam emitted from the light source is drive-controlled in a focusing direction parallel to the optical axis so that the signal recording surface of the rotating optical disc is always irradiated in a focused state. Further, the objective lens is drive-controlled in a tracking direction, which is a direction orthogonal to the optical axis, so as to follow the recording track of the optical disc in a state where the light beam emitted from the light source is condensed.

An objective lens driving device is used as a device for driving and displacing this objective lens in a direction parallel to the optical axis and a direction orthogonal to the optical axis.

As an objective lens driving device of this type, FIG.
The one configured as shown in is known. This Figure 5
The objective lens driving device shown in (1) includes a pair of parallel lens bobbin supporting arms 103 as elastic supporting members to which a lens bobbin 104 to which an objective lens 105 is attached is attached to the free end side. The lens bobbin supporting arm 103 is integrally provided with a supporting member 102 at one end side, and the supporting member 102 is a pair of supporting shafts 1 as a fixed portion that stands upright on a substrate 101 that constitutes a yoke of a magnetic circuit unit.
02a, 102a supporting the substrate 101
It is mounted with a cantilevered support structure on top. The lens bobbin supporting arm 103 is made of a flexible material such as synthetic resin.

Then, on the base end side and the tip end side of the lens bobbin supporting arm 103, the first parallel to the optical axis of the objective lens 105 attached to the lens bobbin 104 in the direction orthogonal to the extension direction of the lens bobbin supporting arm 103. Also, second hinge portions 103a and 103b are formed. The first and second hinge portions 103a and 103b are formed by forming a thin portion on a part of the lens bobbin supporting arm 103.

In this way, the lens bobbin supporting arm 103 is fixed to the supporting member 102 on the base end side and cantilevered.
The objective lens 105 attached to the lens bobbin 104 supported on the distal end side of the lens is displaced and driven in the focusing direction shown by the arrow f in FIG. 5 in the optical axis direction by elastic deformation of the pair of lens bobbin supporting arms 103. , The pair of lens bobbin supporting arms 103 are displaced by using the first and second hinge portions 103a and 103b as the displacement portions, so that the pair of lens bobbin supporting arms 103 are displaced in the two axial directions of the tracking direction shown by the arrow t in FIG. Displacement driven.

A focusing coil 106 and a tracking coil 107 to which a driving current for driving and displacing the objective lens 105 in the focus direction and the tracking direction are supplied are attached to the lens bobbin 104 to which the objective lens 105 is attached. The focusing coil 106 is wound in a rectangular tube shape and is attached to the lens bobbin 104 as a pair.
Are wound in a flat rectangular shape and are attached one by one on one side surface of one focusing coil 106. The focusing coil 106 and the tracking coil 107 are a pair of rising pieces 108a and 108b that are formed to rise from the substrate 101 that constitutes the yoke of the magnetic circuit unit.
Also, it is attached to the lens bobbin 104 so as to face the magnet 109 attached to the one rising piece 108a. Then, the focusing coil 106
Drive current according to the focus error signal is supplied to
By supplying a drive current corresponding to the tracking error signal to the tracking coil 107, the objective lens 105 attached to the lens bobbin 104 is driven and displaced in the focusing direction and the tracking direction.

Then, the objective lens 105 is driven and displaced in the focusing direction and the tracking direction according to the focus error signal and the tracking error signal, whereby the focus control and the tracking control are realized, and the light emitted from the optical pickup device is realized. The beam
It is possible to accurately focus the light on the signal recording surface of the optical disc and accurately scan the recording track formed on the optical disc to follow the recording track.

By the way, in this type of objective lens driving device, in order to protect the optical disc and the objective lens, the range of displacement of the lens bobbin 104 in the focusing direction is mechanically limited, so that the lens bobbin 104 can be protected.
Even when the objective lens 105 attached to the optical disc is closest to the optical disc, the tip of the objective lens 105 is regulated so as not to contact the optical disc. That is, as shown in FIG. 6, the main surface 110 a of the optical disk 110 on the side facing the objective lens 105 is
The range d _D displaced by 0-plane deviation is set to about 0.5 mm above and below the reference position, and the range d _F where the tip of the objective lens 105 is displaced is set to 1 mm above and below the reference position.
To the extent, these ranges d _D and d _F are regulated so as not to overlap each other. Even when the main surface 110a of the optical disk 110 and the tip of the objective lens 105 are closest to each other, the distance d
_{As M} , an interval of about 0.5 mm is maintained.

In order to make the objective lens 105 always follow the optical disc 110 at a predetermined distance regardless of the surface deviation of the optical disc 110, the objective lens 105
The range d _F in which the optical disc 110 is displaced is larger than the range d _{D in} which the optical disk 110 wobbles. Further, the distance from the tip of the objective lens 105 to the focal point of the objective lens 105, that is, the working distance (working distance) d _W is larger than the distance (d _D + d _M ). This working distance d _W is set to about 1.8 to 1.9 mm.

However, even in such an objective lens driving device, when an optical disc that is warped and has a large surface deviation is used, or when the optical disc is mounted in an incorrect state, the optical disc and the objective lens 105 are separated. There is a risk of contact with the tip. Therefore, in order to absorb the shock when the optical disc and the objective lens 105 come into contact with each other,
As shown in FIGS. 5 and 6, a buffer member 111 made of a material such as felt or rubber is attached to the tip of the objective lens 105.

[0012]

By the way, an optical pickup device detects an optical beam emitted from a light source and irradiated on a signal recording surface of an optical disc, and then reflected by the signal recording surface by a photodetector to form an optical disc on the optical disc. The recorded information signal is read. Then, the light beam reflected from the optical disc is detected by receiving the light beam in a light receiving area of a light receiving element such as a photodiode that constitutes the photodetector.

A light receiving element such as a photodiode has a limit in miniaturization and a size of a light receiving region. Therefore, it is extremely difficult for the light receiving element to detect the returning light beam from the optical disc in the state of the spot diameter of the light beam focused and irradiated on the fine recording track formed on the optical disc. Therefore, the spot diameter of the light beam returning from the optical disk is enlarged so that the light beam is received by the light receiving area of the light receiving element. The expansion of the spot diameter of the light beam is performed by extending the optical path of the light beam focused and incident on the photodetector with an optical component such as a lens.

Then, by using an objective lens having a short focal length as the objective lens for condensing the light beam on the signal recording surface of the optical disc and transmitting the returning light beam from the optical disc, an objective lens having a short focal length can be used. Even if the optical path length of the light beam incident on the photodetector is shortened, the spot diameter of this light beam can be sufficiently expanded. By using an objective lens with a short focal length in this way, the distance from the objective lens to the optical disc can be shortened, and the optical path length of the returning light beam from the optical disc to the photodetector can be shortened. It is possible to reduce the size of the optical pickup device.

As described above, by using the objective lens having a short focal length, the distance between the objective lens and the optical disc, that is, the working distance (working distance) can be shortened, for example, to about 1.3 mm.
When the working distance is shortened, the range in which the tip of the objective lens is driven and displaced and the range in which the main surface of the optical disc is displaced due to surface wobbling overlap, and the possibility of contact between these objective lenses and the optical disc increases. .

In the objective lens driving device in which the buffer member is attached to the tip of the objective lens, when the buffer member and the optical disk come into contact with each other, a load is applied to the objective lens via the buffer member. I can't avoid it. The objective lens is formed separately from the lens bobbin, and is attached to the lens bobbin by joining it with an adhesive or the like. Therefore, when a load is repeatedly applied to the objective lens, the joint portion with respect to the lens bobbin may be peeled off, and the mounting position may be displaced or tilted. If such a displacement or inclination of the objective lens occurs, it becomes impossible to accurately focus the light beam on the signal recording surface of the optical disc, and further it becomes impossible to accurately scan the recording track of the optical disc. As a result, it becomes impossible to accurately record the information signal on the optical disc or reproduce the information signal recorded on the optical disc.

Therefore, the present invention has been proposed in view of the above-mentioned circumstances, and even if the buffer member and the optical recording medium are in contact with each other, no load is applied to the objective lens, and the objective lens is not affected. The present invention has been proposed for the purpose of providing a suitable objective lens driving device applied to an optical pickup device in which the device is downsized by shortening the focal length of the lens.

[0018]

In order to achieve the above-mentioned object, an objective lens driving device according to the present invention has a lens bobbin in which an objective lens is attached so as to face an optical recording medium, and one end has a fixed portion. And an elastic support member for supporting the lens bobbin on the free end side so that the lens bobbin is displaceably supported in the optical axis direction of the objective lens and in a plane direction orthogonal to the optical axis direction, A buffer member is disposed near the center of gravity of the lens bobbin attached to the elastic support member, with the tip portion projecting from the tip portion of the objective lens.

[0019]

In the objective lens driving device according to the present invention, when the objective lens is driven and displaced in the focusing direction, the tip of the buffer member comes into contact with the optical recording medium before the tip of the objective lens. A direct load is prevented from being applied to the objective lens attached to the.

Further, since the buffer member is arranged near the center of gravity of the lens bobbin attached to the elastic supporting member, even if the optical recording medium comes into contact with the buffer member, the buffer bobbin is attached to the lens bobbin. Generation of a rotation moment can be suppressed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings. The objective lens driving device according to the present invention is an objective lens driving device for converging a light beam emitted from a light source such as a semiconductor laser which constitutes an optical pickup device and irradiating it as a beam spot on a signal recording surface of an optical recording medium such as an optical disc. It is a device for driving and displacing.

In this objective lens driving device, as shown in FIG. 1, a pair of parallel lens bobbin supporting arms 3 as elastic supporting members having a lens bobbin 4 on which an objective lens 5 is mounted are mounted on the free end side. I have it. The lens bobbin support arm 3 is integrally provided with a support member 2 on one end side, and the support member 2 is a pair of support shafts 2 as a fixed portion that stands upright on a substrate 1 that constitutes a yoke of a magnetic circuit unit.
It is mounted on the substrate 1 in a cantilevered structure by being supported by a and 2a. The lens bobbin support arm 3 is made of a flexible material such as synthetic resin.

The lens bobbin supporting arm 3 has one end on which the supporting member 2 is provided and the other end on which the lens bobbin 4 is attached. The lens bobbin 4 extends in a direction orthogonal to the extension direction of the lens bobbin supporting arm 3. The first and second hinge portions 3a parallel to the optical axis of the objective lens 5 attached to the
3b is formed. The first and second hinge portions 3a and 3b are formed by forming a thin portion on a part of the lens bobbin supporting arm 3.

The objective lens 5 attached to the lens bobbin 4 supported on the free end side of the lens bobbin supporting arm 3 supported in a cantilever manner by supporting the supporting member 2 provided on the one end side on the substrate 1 as described above. The elastic deformation of the pair of lens bobbin supporting arms 3 causes the lens bobbin supporting arms 3 to be displaced and driven in the focusing direction indicated by the arrow f in FIG. 1 in the optical axis direction. By displacing 3a and 3b as the displacement portions, the displacement is driven in the biaxial directions of the tracking direction shown by the arrow t in FIG.

A focusing coil 6 and a tracking coil 7 to which a driving current for driving and displacing the objective lens 5 in the focus direction and the tracking direction are supplied are attached to the lens bobbin 4 to which the objective lens 5 is attached. The focusing coils 6 are wound in a rectangular tubular shape and are mounted in pairs on the lens bobbin 4, and the tracking coils 7 are wound in a flat rectangular shape and are mounted in pairs on one side surface of one focusing coil 6. There is. The focusing coil 6 and the tracking coil 7 are arranged so as to face a pair of rising pieces 8a, 8b formed upright from the substrate 1 forming the yoke of the magnetic circuit section and a magnet 9 attached to one rising piece 8a. , Mounted on the lens bobbin 4. Then, the focusing coil 6 is supplied with a drive current according to the focus error signal, and the tracking coil 7 is supplied with a drive current according to the tracking error signal, whereby the objective lens 5 attached to the lens bobbin 4 is supplied.
Is driven and displaced in the focusing direction and the tracking direction.

In the objective lens driving device according to the present invention, as shown in FIG. 1, the tip end portion is provided in the vicinity of the center of gravity of the lens bobbin 4 supported on the free end side of the lens bobbin supporting arm 3. The buffer member 10 is attached by projecting from the tip of the objective lens 5 attached to the lens bobbin 4. Further, the mounting position of the buffer member 10 is
It is a position on the lens bobbin 4 that is not in contact with the objective lens 5.

The distance from the tip of the objective lens 5 to the tip of the buffer member 10 is the distance from the tip of the objective lens 5 to the focal point of the objective lens 5, that is, the working distance (working distance of the objective lens 5).・ Distance).

The cushioning member 10 used here is made of heat such as styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-butadiene-styrene block copolymer (SBS) or styrene-isoprene-styrene block copolymer (SBS). It is formed of a plastic elastomer.

The buffer member 10 made of this thermoplastic elastomer has low hardness and high breaking strength. The cushioning member 10 may be attached to the lens bobbin 4 using an adhesive, but the thermoplastic elastomer cannot sufficiently guarantee the adhesive strength of the adhesive.

Therefore, it is desirable that the cushioning member 10 be attached to the lens bobbin 4 without using an adhesive. For example, on the upper surface of the lens bobbin 4, as shown in FIG. 2, a cushioning member supporting projection 11 having a spherically shaped retaining portion 11a formed in a bulge is planted. On the other hand, the cushioning member 10 is formed in a bottomed cylindrical shape having a bottom portion 10b having a fitting hole 10a formed therein, and the fitting hole 10a is inserted into and fitted to the cushioning member support projection 11 to be mounted.

Further, the cushioning member 10 is formed as shown in FIG. That is, in this cushioning member 10, a cylindrical cushioning portion 10d is bulged at one end of the shaft portion 10c inserted into the insertion hole 12 formed in the lens bobbin 4, and the shaft portion 1 is formed.
A spherical retaining portion 10e is formed to bulge at the other end of 0c. The cushioning member 10 shown in FIG. 3 is attached to the lens bobbin 4 so as to be prevented from coming off by being inserted into the insertion hole 12 from the coming-off preventing portion 10e.

Further, as shown in FIG. 4, the cushioning member 10 is formed in a plate shape, and a pair of supporting claws 13 formed on the lens bobbin 4 support both ends thereof, and the projections provided on these supporting claws 13 are supported. You may make it attach so that the center part may be made to project above the lens bobbin 4 by the stripe part 14. A pair of support claws 1 that support both ends of a plate-shaped cushioning member 10.
3 has support grooves 13a formed on opposite sides. Then, the plate-shaped cushioning member 10 has support grooves 13a at both ends.
The cushioning member 10 is attached to the lens bobbin 4 while being prevented from falling off by the elastic force of the cushioning member 10 by being supported by the protrusion 14 so as to swell.

The objective lens driving device according to the present invention configured as described above is arranged in the optical disc recording and / or reproducing device so that the objective lens 5 faces the signal recording surface of the optical disc. At this time, the objective lens driving device is arranged so that the optical axis of the objective lens 5 is perpendicular to the signal recording surface of the optical disc and the tracking direction is substantially orthogonal to the tangential direction of the recording track formed on the optical disc. To be done.

Then, the light beam emitted from the optical system block including the light source of the optical pickup device is condensed by the objective lens driving device provided in the optical disc recording and / or reproducing device, and the signal of the optical disc is collected. It is irradiated as a beam spot on the recording surface. The light beam applied to the signal recording surface of the optical disc is reflected by the signal recording surface of the optical disc, returns to the optical system block again through the objective lens 5, and is detected by the photodetector built in this optical system block. .

The optical pickup device reads the information signal recorded on the optical disc by processing the detection signal detected by the photodetector by the detection signal processing circuit, and also generates the focus error signal and the tracking error signal. To do. Here, the focus error signal is
It is a signal indicating the amount of deviation of the beam spot of the light beam irradiated on the optical disc through the objective lens 5 in the optical axis direction of the objective lens 5. The tracking error signal is a deviation amount of the beam spot with respect to a recording track formed on the optical disc, and indicates a deviation amount of the beam spot in a direction orthogonal to a tangent line of the recording track. Focusing and tracking drive currents are generated based on these error signals. By supplying these drive currents to the corresponding coils 6 and 7, focus control and tracking control are performed. That is,
The beam spot of the light beam applied to the optical disc through the objective lens 5 is controlled so as to be always focused on the recording track of the optical disc without being affected by so-called surface wobbling or center wobbling of the optical disc. To be done. In this way, the optical disc is always positioned within the working distance range of the objective lens 5 when the focus control and the tracking control are activated.

By the way, when an information signal is written to and / or read from an optical disc having a large amount of surface deviation by the optical pickup device to which the objective lens driving device is applied, or when the optical disc is in an incorrect state. When mounted, the focus control of the objective lens 5 may not operate normally. In such cases,
The buffer member 10 provided on the lens bobbin 4 may come into contact with the optical disc.

In the objective lens driving device according to the present invention, the tip of the buffer member 10 projects toward the optical disc side more than the tip of the objective lens 5, so that the optical disc may come into contact with the tip of the objective lens 5. Absent. Since the cushioning member 10 has a low hardness, that is, is soft, it does not damage the optical disc even when it comes into contact with the optical disc. Further, since the buffer member 10 is attached to the lens bobbin 4 so as to restrict the contact of the objective lens 5 with the optical disc, the buffer member 10
Even when the optical disc contacts the optical disc, no load is applied to the objective lens 5.

The cushioning member 10 may be impregnated with a lubricant such as oil or fat in order to further reduce friction with the optical disc when it comes into contact with the optical disc. As the lubricant, for example, a material such as an olefin-based oil or fat that does not chemically corrode the optical disk can be used.

Further, since the buffer member 10 is mounted near the center of gravity of the lens bobbin 4 supported on the free end side of the lens bobbin supporting arm 3, it comes into contact with the optical disc and receives a pressing force from the optical disc. Even if
It is possible to prevent the rotation moment from being generated in the lens bobbin 4. Therefore, since the lens bobbin 4 supported on the free end side of the lens bobbin supporting arm 3 is restricted in a large inclination when coming into contact with the optical disc, the focus control is not activated due to the contact of the lens bobbin 4 with the optical disc. After that, the time required to return to the focus control operation state can be shortened.

[0040]

As described above, in the objective lens driving device according to the present invention, the tip end portion of the lens bobbin is located near the center of gravity of the lens bobbin attached to the free end side of the elastic supporting member that is cantilevered. Since the buffer member is disposed so as to protrude from the tip of the objective lens attached to the lens, even when the optical recording medium comes into contact with the buffer member, it is possible to prevent the rotational moment from being generated in the lens bobbin. Therefore, the state in which the focus control and the tracking control are disturbed can be quickly returned to the normal focus or tracking control state.

Further, since the tip of the buffer member comes into contact with the optical recording medium before the tip of the objective lens when the objective lens is driven and displaced in the focusing direction, the objective lens is directly loaded. It is prevented from being added, and the objective lens attached to the lens bobbin can be protected. In particular, it is possible to reliably prevent the displacement of the mounting position of the objective lens mounted on the lens bobbin.

Therefore, it is useful as an objective lens driving device using an objective lens having a short focal length in which the distance between the objective lens and the optical recording medium is shortened, and the optical pickup device using this objective lens driving device is miniaturized. Will be useful to.

[Brief description of drawings]

FIG. 1 is a perspective view showing an objective lens driving device according to the present invention in which a lens bobbin is supported by a movable supporting arm member.

FIG. 2 is a partially cutaway perspective view showing an example of a buffer member applied to an objective lens driving device according to the present invention.

FIG. 3 is a perspective view showing another example of the cushioning member constituting the present invention with a part thereof cut away.

FIG. 4 is a perspective view showing still another example of the cushioning member constituting the present invention with a part thereof cut away.

FIG. 5 is a perspective view showing a conventional objective lens driving device.

FIG. 6 is a schematic diagram illustrating a positional relationship between an objective lens and an optical recording medium in a conventional objective lens driving device.

[Explanation of symbols]

 3 lens bobbin support arm 4 lens bobbin 5 objective lens 10 cushioning member

Claims (1)

[Claims] 1. An objective lens is mounted facing an optical recording medium.
And the lens bobbin that is mounted on the free end side of the lens bobbin.
Mounted on the lens bobbin of the objective lens.
Displaceable in the optical axis direction and in the plane direction orthogonal to this optical axis direction
On the lens bobbin attached to the elastic support member.
In the vicinity of the center of gravity, move the tip from the tip of the objective lens above.
An objective lens driving device in which a cushioning member is provided so as to project .