JPH0519854Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a pickup device in an optical information recording/reproducing device.

BACKGROUND ART Disks such as video disks and digital audio disks, which are information recording media, are
The information signal is recorded by forming minute pits (indentations) corresponding to the information signal as spiral tracks on its surface. When reading an information signal recorded in this manner, a fine spot light is irradiated onto the track, and changes in reflected light depending on the presence or absence of pits are converted into electrical signals and reproduced as the original information signals.

In this reproduction, the irradiated light must be accurately focused on the recording surface of the disk, and for this purpose,
It is necessary to control the position (focus servo) of the objective lens for focusing the irradiation light on the recording surface in the optical axis direction (focus direction) of the objective lens. Furthermore, since the irradiation light must accurately follow the recording track, it is also necessary to perform position control (tracking servo) of the irradiation light in a direction perpendicular to the optical axis direction (tracking direction).

A device as shown in FIG. 7 has already been developed for controlling the position of the objective lens.

As illustrated, the objective lens 101 is attached to a rectangular plate-shaped lens holder 102 that is a holding member. A focusing coil 103 is wound on the lower surface of the lens holder 102 so that the central axis of the coil is parallel to the optical axis of the objective lens 101 and that the cross-sectional shape perpendicular to the central axis of the coil is a substantially rectangular ring. is fixed. Four tracking coils 104 are attached to the outer surface of this focusing coil 103. These four tracking coils 104 are each wound in an annular shape beforehand, and the focusing coil 104
It is pasted on top of 3. The focusing coil 103 and the tracking coil 104, and therefore the objective lens 101, are arranged in the optical axis direction (arrow F direction) and the optical axis direction by a pair of frames 105 and a plurality of leaf springs 106 and 107. They are supported so as to be movable in the vertical direction (direction of arrow T). A magnetic circuit consisting of a yoke 109 and each pair of magnets 110 and yoke plates 111 is provided below the objective lens 101. The yoke 109 is provided with a pole portion 109a, and a focusing coil 103 and a tracking coil 104 are inserted into magnetic gaps 112 and 113 formed by the pole portion, a magnet 110, and a yoke plate 111. . That is, the pole portion 109a is fitted into the internal space 103a of the focusing coil 103. In addition, pole part 1
The through hole 109b provided in the hole 09a is for passing irradiation light emitted from a light emitting element (not shown).

The magnet 110 generates parallel magnetic flux toward the pole portion 109a facing the magnet. Magnetic gap 112 where this parallel magnetic flux exists
Since the focusing coil 103 and the tracking coil 104 are located within the magnetic flux 113 so as to be perpendicular to each other in a plane perpendicular to the magnetic flux, each of the arrows F and T can be adjusted by supplying current to these coils. The objective lens 101 can be driven in this direction.

In the device configured as described above, the pole portion 109a, which is a part of the magnetic circuit, is inserted into the focusing coil 103, and the through hole 109b for passing the irradiated light is formed in the pole portion. The outer diameter of the focusing coil 103, and therefore the magnetic circuit, must be increased. As a result, there was a problem in that the entire device became large.

Summary of the invention The present invention has been made in view of the above points, and its purpose is to provide a pickup device that can be easily miniaturized.

The pickup device according to the present invention includes an objective lens 30 for irradiating a recording surface of a recording medium with spot light, support mechanisms 31, 34, 36, 37 for supporting the objective lens movably in a focusing direction and a tracking direction. 38, 39, and driving means 32, 35, 4 for driving the objective lens.
1, 42, and 43, the driving means includes a first coil 32 wound such that the central axis of the coil is approximately parallel to the focusing direction, and a first coil 32 whose central axis is approximately parallel to the tracking direction. The second coil 35 is wound as follows.
and magnetic circuits 32, 35, 41, and 42 that generate magnetic flux that interlinks with the first coil and the second coil, the magnetic circuits sandwiching a plane including the focusing direction and the tracking direction. A pair of magnets 41 arranged so that the same poles face each other and sandwich the first coil and the second coil between the opposing poles, and a yoke that magnetically couples each of the non-opposing poles of the pair of magnets. 42, the yoke has a protrusion 42a that protrudes from a predetermined portion of the yoke that is not in contact with the magnet in the tracking direction and reaches near the opposing pole, and the second coil 35 It is characterized in that it is formed so as to fit externally into 42a.

By adopting such a configuration, the focusing coil and the magnetic circuit can be made extremely small compared to the conventional format in which a part of the magnetic circuit is inserted into the focusing coil.
As a result, the entire device can be made smaller.

In addition, since the effective magnetic flux interlinking with the focusing coil and the tracking coil increases, the magnetic circuit can be made smaller compared to conventional devices without protrusions when the required amount of effective magnetic flux is constant. In other words, the entire device can be made smaller.

Embodiment Hereinafter, a pickup device as an embodiment of the present invention will be described with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, the pick-up device has a pick-up body 1 which is a holding member. The pick-up body 1 is made of aluminum, its alloy, or synthetic resin, and has a through hole 1a as shown in FIG. A laser diode 3 as a light emitting element, a grating (diffraction grating) 4, a beam splitter 5, and a collimator lens 6 are coaxially arranged in the through hole 1a. The grating 4 is for splitting the irradiation light emitted from the laser diode 3 into light for focus servo for reproduction RF signal requirements and light for tracking servo. It transmits the irradiated light and bends the reflected light from the recording surface of the disk, which will be described later, with respect to the irradiated light, and guides it to a light receiving element, which will be described later. Further, the collimator lens 6 is for converting the irradiated light into parallel light.

Among the optical elements mentioned above, the laser diode 3, the grating 4, and the beam splinter 5
are supported on cylindrical holders 7, 8, and 9 such that the optical axes of these three optical elements coincide with the central axis of each holder, and each holder has a through hole 1a as a holder insertion hole. They are stacked and inserted inside. The through hole 1a has a circular cross section perpendicular to its central axis, and therefore each holder 7, 8, and 9 is movable along the central axis of each holder and rotated about the central axis. It is now possible to move. However, the holder 7 is fixed to the pick-up body 1 with screws.

As shown in FIG.
A wave plate 25 formed into a rectangular plate shape is disposed above the wave plate 25 , and is supported by a plate-shaped base member main body 27 via a holder 26 . However, the holder 26 constitutes the entire base member together with the base member main body 27. Further, the base member main body 27 is held by the pick-up body 1. Note that the wavelength plate 25 is the laser diode 3 described above.
This is for changing the polarization direction of the light in order to use the beam splitter 5 to separate the irradiation light emitted from the disc recording surface and the reflected light from the disk recording surface.

A fixing mechanism including the aforementioned pick-up body 1, laser diode 3, grating 4, beam splitter 5, collimator lens 6, cylindrical holders 7, 8 and 9, cylindrical sleeve 14, etc., and a wavelength plate. 25, the holder 26, the plate-shaped base member main body 27, and peripheral small members related thereto constitute a fixed optical system.

As shown in FIG. 1, an objective lens 30 is arranged above the wavelength plate 25 to focus the irradiation light emitted from the laser diode 3 onto the recording surface of the disk 29 as a spot light.
A cylindrical lens pad 30a is fitted around the outer periphery of the objective lens 30. The objective lens 30 is fitted into the upper end of a lens holder 31, which is a first holding member formed into a substantially cylindrical shape, so that its optical axis coincides with the central axis of the lens holder. As shown in FIGS. 3 and 4, a focusing coil 32 is wound around the outer periphery of the lens holder 31 so that the center axis of the coil coincides with the optical axis direction of the objective lens 30. As shown in FIGS. Note that a counterweight 30b is attached to the lower end of the lens holder 31. The lens holder 31 has a total of four overhangs, each pair of which protrude in a direction perpendicular to the optical axis direction of the objective lens 30 and in opposite directions about the central axis of the lens holder, on both ends of the lens holder 31 in the central axis direction. 31a and 31b are provided. One of each pair of protruding parts 31a and 31b is opposed to each other in the direction of the central axis of the lens holder 31. Two of these overhangs 3 facing each other
A bobbin 3 having a rectangular cross section is located between 1a and 31b.
4 is installed. A tracking coil 35 is wound around the outer periphery of the bobbin 34 so that the center axis of the coil coincides with a direction perpendicular to the optical axis direction of the objective lens 30. This tracking coil 35 is called a second coil, whereas the focusing coil 32 is called a first coil.
In addition, the lens holder 31 and the bobbin 34 are each
They will be referred to as a first holding member and a second holding member.

Two overhangs 31 with bobbins 34 attached
The other two projecting portions 31a and 31b protruding in the opposite direction to the projecting portions 31a and 31b include a pair of flexible projecting portions that are spaced apart and parallel to each other in the optical axis direction of the objective lens 30 and are flexible in that direction. One end of each leaf spring 36, which is a flexible member, is connected. The other end of each leaf spring is connected to a relay member 37. That is,
Each leaf spring 36 is attached to the relay member 37 in the form of a cantilever. Connected to the relay member 37 are respective one ends of a pair of leaf springs 38, which are a pair of flexible members arranged parallel to and apart from each other in a direction perpendicular to the optical axis direction of the objective lens 30 and flexible in the direction. There is. The other ends of the pair of leaf springs 38 are connected to a base member 39. That is, each leaf spring 38 is attached to the base member 39 in a cantilevered manner.

These lens holder 31, bobbin 34, leaf spring 36, relay member 37, leaf spring 38, base member 39, and peripheral small members related to these allow the objective lens 30 to be A support mechanism is configured to support the objective lens so that it is movable in the optical axis direction and in a direction perpendicular to the optical axis direction, and so that the optical axis of the objective lens is perpendicular to the recording surface of the disk 29.

Here, the relay member 37 and each leaf spring 36 and 38
The state of connection with is explained in detail.

The leaf springs 36 and 38 and the relay member 37 are bonded to each other with an adhesive. The relay member 37 has a protrusion 37a that protrudes from the adhesive surface with each leaf spring.
is formed. Further, as is particularly clear from FIG. 3, the relay member 37 has an escape groove 37b for the adhesive between the adhesive surface with the leaf spring 36 and the protrusion 37a.
is formed. When bonding each leaf spring 36 and 38 to the relay member 37, the protrusion 37a is held by a predetermined jig or the like (not shown), and an escape groove 37b for the adhesive is provided. This prevents the adhesive from flowing into the jig, etc., and prevents the relay member 37 and the jig, etc. from being glued together.

As shown in FIGS. 2 and 3, the same polarity is sandwiched between a plane perpendicular to the optical axis direction of the objective lens 30 and a direction perpendicular thereto, that is, a plane including the focusing direction and the tracking direction. A pair of magnets 41 are arranged to face each other and sandwich the focusing coil 32 and tracking coil 35 between the opposing poles. These pair of magnets 41 are magnetically coupled by a yoke 42 which is generally U-shaped as a whole. These magnets 41 and yoke 42
A magnetic circuit that generates a magnetic flux that interlinks with the focusing coil 32 and the tracking coil 35 is configured.

A protrusion 42a is formed in a portion of the yoke 42 that is not in contact with the magnet 41 so that its tip is located near the tracking coil 35. By providing this protrusion 42a, the magnetic flux interlinking with the tracking coil 35 is increased, and therefore the objective lens driving force in the tracking coil direction: T is increased. Also, yoke 4
2 is provided with a sub-yoke 42b which is provided in a portion not in contact with the magnet 41 and whose tip reaches the vicinity of the focusing coil 32. However, this sub-yoke 42b may be a protrusion integrally molded with the yoke 42, similar to the above-described protrusion 42a. By providing this sub-yoke 42b, the magnetic flux interlinking with the focusing coil 32 increases, so that the focusing direction: F
The driving force of the objective lens is increasing.

As is particularly clear from FIG. 3, each of the opposing surfaces of the pair of magnets 41 has an objective lens 3
A recess 41 whose cross section perpendicular to the optical axis direction of 0 is arc-shaped.
The focusing coil 32 is fitted between these two recesses 41a. The size of the recess 41a is such that the movable range of the focusing coil 32 in the direction of the coil center axis of the tracking coil 35 is such that
The movable range is larger than the range of movement in the opposite direction. That is, both concave portions 41a are formed on both sides of, for example, an ellipse or a long hole whose long axis coincides with the coil center axis direction of the tracking coil 35.

For example, as shown in FIGS. 3 and 4, a flexible printed circuit board 43 is provided for supplying current to the focusing coil 32 and the tracking coil 35, and the printed circuit board is connected to the leaf spring 36. , 38, as well as a relay member 37 and a base member 39 serving as fixing portions of each leaf spring. Further, although not particularly shown, the printed circuit board 43 is bonded to each elastic surface of each leaf spring and the fixed portion with a vibration-absorbing adhesive. A leaf spring 3 is used to drive the objective lens 30.
When 6 and 38 are bent, the resonance of each leaf spring is prevented by the vibration absorbing action caused by the deformation of the printed circuit board 43, but using an adhesive with vibration absorbing properties in this way Therefore, the vibration absorption effect is further increased.

In addition, as shown in FIG.
1a is formed with notches 31c on both sides in the protruding direction of the overhang, and the coils are drawn out from the focusing coil 32 and the tracking coil 35 to the printed circuit board 43 through the notches. . As is clear from the foregoing, the focusing coil 32 and the tracking coil 35 are housed in a magnetic circuit that includes a pair of magnets 41.
By drawing out the coils through the notch 31c, the spacing between the magnets can be narrowed, making it easier to downsize the magnetic circuit and, by extension, the pickup device as a whole.

A drive for driving the objective lens 30 by the above-described focusing coil 32, tracking coil 35, magnetic circuit including the magnet 41 and yoke 42, the printed circuit board 43, and peripheral small members related thereto. The means are configured. Furthermore, the drive mechanism and the support mechanism including the aforementioned plate springs 36, 38, etc. constitute a drive mechanism that servo drives the objective lens 30. Furthermore,
The drive mechanism and objective lens 30 constitute a movable optical system. The above-described fixed optical system and the movable optical system are coupled with a common optical axis.

Here, the wavelength position 25 will be explained again.

For example, as shown in FIG.
1 and the yoke 42 are fixed to the pickup body 1 by a pair of screws 45. As is clear from FIG. It is held and fixed by the magnetic circuit and the pick-up body 1. Therefore, a special fixing member for fixing the base body 27 is not required. Further, the wavelength plate 25 is attached to the surface of the base member consisting of the base member main body 27 and the holder 26 on the opposite side to the objective lens 30.

In the pickup device with the above configuration,
The irradiated light emitted from the laser diode 3 sequentially passes through the grating 4, the beam splitter 5, the collimator lens 6, the wavelength plate 25, and the objective lens 30, and is focused on the recording surface of the disk 29 as a fine spot light. Further, the reflected light from the recording surface of the disk 29 travels backward through the objective lens 30, the wavelength plate 25, and the collimator lens 6, enters the beam splitter 5, and then reaches the light receiving element 16 via the multi-lens 20.

As shown in FIG. 5, the light receiving surface of the light receiving element 16 is provided with a photodiode 57 for focus servo for reproduction RF signals and a pair of photodiodes 58 for tracking servo. The light receiving surface of the photodiode 57 is 57a, 5
It is divided into four parts 7b, 57c and 57d. Although it will not be described in detail because it is well known, each divided portion 57a to 57d is formed by utilizing the property that when light having convergence is transmitted through a so-called cylindrical lens, it is converged as two focal lines perpendicular to each other. The amount of light irradiated on the disk is detected and measured, the mutual positional relationship between the disk recording surface and the objective lens 30 is determined, and the objective lens 30 is adjusted accordingly.
is used to perform focus servo. In addition to the function of the cylindrical lens described above, the multi-lens 20 functions as a convex lens that provides convergence to the light reflected from the disk recording surface. Further, a signal for tracking servo is obtained from the difference in the amount of light received by the pair of photodiodes 58, respectively.

As shown in FIG. 6, the objective lens 30 is
The objective lens moves between a first position (indicated by a two-dot chain line) approaching the recording surface of the disk 29 and a second position (indicated by a one-dot chain line) away from the recording surface. The stopping position (indicated by a solid line) of the objective lens 30 when the power of the driving means (described above) for driving the objective lens 30 is turned off is set closer to the second position than the center between the first position and the second position. There is. That is, if the movement stroke of the objective lens 30 is S, then the dimension indicated by L in FIG. It is also getting smaller.

Effects of the Invention As detailed above, in the pick-up device of the optical information recording/reproducing apparatus according to the present invention, the driving means for driving the objective lens supported movably in the focusing direction and the tracking direction is arranged such that the central axis of the coil is A first coil (focusing coil) wound so as to be substantially parallel to the optical axis direction, and a second coil wound so that the coil center axis is substantially parallel to the direction perpendicular to the optical axis direction. It has a coil (for example, a tracking coil) and a magnetic circuit that generates magnetic flux that interlinks with the first and second coils, and the magnetic circuit has the same polarity across a plane that includes the focus direction and the tracking direction. The magnet includes a pair of magnets which are arranged to face each other and to sandwich the first and second coils between the opposite poles, and a yoke which magnetically couples each of the non-opposed poles of the pair of magnets.

In this way, since the magnetic circuit is formed to surround the focusing coil, etc., the focusing coil and the The magnetic circuit can be made extremely small, making it easier to downsize the entire device.

Further, in the pickup device according to the present invention, a protrusion is provided that protrudes in the tracking direction from a predetermined portion of the yoke that is not in contact with the magnet and reaches near the opposing pole, and the second coil is attached to the protrusion. It is formed to fit externally. Therefore, a new magnetic flux is generated between the opposing pole and the protrusion, and the effective magnetic flux interlinking with the focusing coil or tracking coil increases. Therefore, when the amount of effective magnetic flux required is constant, the magnetic circuit, and therefore the entire device, is smaller than a conventional pickup device that is not provided with the protrusion.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of a pickup device as an embodiment of the present invention, and FIG.
3 and 4 are exploded perspective views and perspective views showing the objective lens and its drive mechanism, respectively. FIG. 5 is a detailed view of the light receiving surface of the light receiving element, and FIG. 6 is a diagram showing the movement stroke of the objective lens. FIG. 7, which is a diagram for explaining the relationship between the stop positions, is a perspective view of a main part of a pickup device that has already been developed. Explanation of symbols of main parts, 1...Pickup body, 1a...Through hole, 1a, 1c, 7a...Receiving surface, 1a, 1e, 1f, 1g...Adjustment jig insertion hole, 1h...Adhesive reservoir , 1i...guide hole, 1k
...Spot facing part, 1l...Long hole, 1m, 17a, 5
0a, 50b, 50c...Opening part, 1n, 17
b, 41a... recess, 1p... round hole, 3... laser diode, 4... grating, 4a...
Outer surface, 5... Beam splitter, 5a, 5b...
...Optical axis, 6...Collimator lens, 7, 8, 9,
21...Cylindrical holder, 7b...Inner peripheral surface, 7c...
...pupil, 7d...wall part, 9a...centering guide part, 11, 12, 23b...wavy washer, 1
4...Cylindrical sleeve, 14a...Light passing hole, 1
4b... Wall portion, 14c... Outer surface, 16... Light receiving element, 17... Plate base member, 18... Pressing spring, 19a, 19b, 23, 39a, 39b, 4
5, 51, 52a...Screw, 20...Multi lens, 21a...Annular groove, 23a...Washer, 2
3c... Neck sleeve, 25... Wave plate, 26...
...Holder, 26a... Spot facing portion, 26b... Arc-shaped portion, 26d, 47b... Protrusion, 26e... Outer periphery, 26f... Arm portion, 26g... Bent portion, 2
7...Base member main body, 27a...Support protrusion, 2
7b...center hole, 29...disk, 30...objective lens, 30a...lens pad, 30b...
Counterweight, 31... Lens holder, 31
a, 31b...projection, 31c...notch, 32
... Focusing coil, 34 ... Bobbin, 3
5... Tracking coil, 36, 38... Leaf spring, 37... Relay member, 37a... Projection, 37
b... Adhesive relief groove, 39... Base member, 3
9c...Positioning protrusion, 39d...Recess, 41...
...Magnet, 42...Yoke, 42a...Protrusion, 42b...Sub-yoke, 42d...Tapered portion, 43...Printed circuit board.

Claims (1)

[Claims for Utility Model Registration] An objective lens 30 for irradiating a recording surface of a recording medium with spot light, and support mechanisms 31, 34, 36, 37 that support the objective lens movably in a focusing direction and a tracking direction. ,38,
39, and a driving means 3 for driving the objective lens.
2, 35, 41, 42, and 43, the driving means includes a first coil 32 wound such that the central axis of the coil is substantially parallel to the focusing direction, and a first coil 32 wound such that the central axis of the coil is approximately parallel to the tracking direction. The second coil 35 is wound approximately parallel to each other.
and magnetic circuits 32, 35, 41, and 42 that generate magnetic flux that interlinks with the first coil and the second coil, the magnetic circuits sandwiching a plane including the focusing direction and the tracking direction. A pair of magnets 41 arranged so that the same poles face each other and sandwich the first coil and the second coil between the opposing poles, and a yoke that magnetically couples each of the non-opposing poles of the pair of magnets. 42, the yoke has a protrusion 42a that protrudes in the tracking direction from a predetermined portion thereof that is not in contact with the magnet and reaches near the opposing pole, and the second coil 35 42a. A pickup device in an optical information recording/reproducing device, characterized in that the pickup device is formed to be fitted onto the outside of the optical information recording/reproducing device.