Patent Application
20140089952
1. Field of the Invention
The present invention relates to an optical pickup for an optical disc drive for reading out information recorded on a recording surface of an optical disc and/or recording information on an optical disc.
2. Description of the Related Art
An optical pickup as background technology of this technical field has been described in JP-2009-187619-A, for example. JP-2009-187619-A describes a configuration for directly winding focusing coils and tracking coils around a lens holder of the optical pickup. In this configuration, a gap exists between each focusing coil and each extending surface of the lens holder (around which each tracking coil is wound), between each focusing coil and an adjacent wire supporting part, and between each focusing coil and an adjacent post protruding from the lens holder (see Paragraph 0036 and FIG. 2).
In the configuration of JP-2009-187619-A, the wire supporting parts for fixing wires protrude from side faces of the lens holder and extend downward. Further, the posts, on which coil-winding protrusions (to which ends of the wires are soldered) have been formed, also protrude from the side faces of the lens holder and extend downward similarly to the wire supporting parts. Since the wire supporting parts and the posts protrude from the side faces of the lens holder and extend downward as described above, the gap has to be formed between each focusing coil and the adjacent wire supporting part and between each focusing coil and the adjacent post in order to make it possible to wind the focusing coils around the lens holder. However, the formation of the gaps leads to a decrease in the lengths of the focusing coils since the external shape of the lens holder is restricted by the prescribed dimensions of the apparatus. Thus, enhancement of the driving force generated by the focusing coils has not been sufficiently taken into consideration in JP-2009-187619-A.
It is therefore the primary object of the present invention to provide an optical pickup having a configuration for directly winding the coils around the lens holder and also being capable of enhancing the driving force generated by the coils.
In order to achieve the above object, an aspect of the present invention provides an optical pickup comprising: an objective lens which converges light on an optical disc; a lens holder to which the objective lens is attached; a focusing coil and a tracking coil which are wound around the lens holder; magnets which are arranged to face two side faces of the lens holder parallel to a radial direction of the optical disc; supporting members which support the lens holder; and supporting member fixation parts which are provided on two side faces of the lens holder orthogonal to the radial direction of the optical disc. In the optical pickup, the focusing coil is wound on parts of the lens holder on both sides of the lens holder in regard to the radial direction of the optical disc so that each portion of the focusing coil on each side is wound around a winding central axis extending in a direction parallel to the optical axis of the objective lens. The tracking coil is wound on central parts of the two side faces of the lens holder parallel to the radial direction of the optical disc. A gap exists between the focusing coil and the tracking coil. The focusing coil is wound between the supporting member fixation parts.
Preferably, the magnets are arranged on one side and on the other side in regard to the radial direction of the optical disc. The polarity of the surface of each magnet facing the lens holder is varied depending on whether the magnet is arranged on the one side or on the other side. The focusing coil is wound between the supporting member fixation parts in regard to the optical axis direction of the objective lens.
Preferably, the optical pickup has coil-winding protrusions to which ends of the focusing coil and the tracking coil are wound. The coil-winding protrusions protrude in the axial direction of the supporting members from a side face of the lens holder parallel to the radial direction of the optical disc.
Preferably, end faces of the focusing coil far from the objective lens in regard to the radial direction of the optical disc are situated at positions farther from the optical axis of the objective lens than the coil-winding protrusions.
Preferably, end faces of the focusing coil far from the objective lens in regard to the radial direction of the optical disc are situated at positions farther from the optical axis of the objective lens than the supporting members.
Preferably, the gap between the focusing coil and the tracking coil is formed to secure a space on the plane of the winding of the focusing coil between a first circle having a radius specified as the distance from the winding central axis of the focusing coil to outer corners of the contour of the focusing coil and a second circle having a radius specified as the distance from the winding central axis of the focusing coil to the parts of the lens holder where the tracking coil is wound.
In order to achieve the above object, another aspect of the present invention provides an optical pickup comprising: an objective lens which converges light on an optical disc; a lens holder to which the objective lens is attached; a focusing coil and a tracking coil which are wound around the lens holder; magnets which are arranged to face two side faces of the lens holder parallel to a radial direction of the optical disc; supporting members which support the lens holder; and supporting member fixation parts which are provided on two side faces of the lens holder orthogonal to the radial direction of the optical disc. In the optical pickup, the magnets are arranged on one side and on the other side in regard to the radial direction of the optical disc. The polarity of the surface of each magnet facing the lens holder is varied depending on whether the magnet is arranged on the one side or on the other side. The focusing coil is wound on parts of the lens holder on both sides of the lens holder in regard to the radial direction of the optical disc so that each portion of the focusing coil on each side is wound around a winding central axis extending in a direction parallel to the optical axis of the objective lens. The tracking coil is wound on central parts of the two side faces of the lens holder parallel to the radial direction of the optical disc. A space is secured on the plane of the winding of the focusing coil between a first circle having a radius specified as the distance from the winding central axis of the focusing coil to outer corners of the contour of the focusing coil and a second circle having a radius specified as the distance from the winding central axis of the focusing coil to the parts of the lens holder where the tracking coil is wound.
According to the present invention, the lengths of parts of the focusing coil facing the magnets can be increased, by which an optical pickup comprising a focusing coil capable of generating greater driving force can be provided.
Other objects and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which:
Referring now to the drawings, a description will be given in detail of preferred embodiments in accordance with the present invention. In the following description, components that are assigned identical reference characters in the drawings are those having the same functions, and thus explanation of such equivalent components can be omitted when an explanation has already been given of the reference character.
The objective lens 1 is mounted on the upper surface of a lens holder 2. The lower part of the lens holder 2 has protruding parts 8a and 8b formed on both sides in regard to the radial direction of the optical disc (y direction). The lens holder 2 has two side faces orthogonal to the radial direction of the optical disc (y direction). Each of the side faces orthogonal to the y direction is provided with a first supporting member fixation part 9a, a second supporting member fixation part 9b and a third supporting member fixation part 9c (from top to bottom).
A focusing coil of the optical pickup is made up of a first focusing coil 3 and a second focusing coil 4. The first focusing coil 3 is wound around the protruding part 8a on one side of the lens holder 2 to surround a winding central axis extending in the direction parallel to the optical axis of the objective lens 1 (z direction). The second focusing coil 4 is wound around the protruding part 8b on the other side of the lens holder 2 to surround another winding central axis extending in the direction parallel to the optical axis of the objective lens 1 (z direction). In this case, each of the first and second focusing coils 3 and 4 is wound between the second supporting member fixation part 9b and the third supporting member fixation part 9c in regard to the optical axis direction of the objective lens 1 (z direction).
The lens holder 2 also has two side faces parallel to the radial direction of the optical disc (y direction). A central part of each of the side faces parallel to the y direction is provided with winding frames 10. A tracking coil 5 is wound around the winding frames 10 on each side face parallel to the y direction.
The lens holder 2 is supported by supporting members 6 to be movable with respect to a fixed part 7. Ends of the supporting members 6 on one side are put through the first supporting member fixation part 9a, the second supporting member fixation part 9b and the third supporting member fixation part 9c of the lens holder 2, respectively, and then fixed by using an adhesive agent or the like. The other ends of the supporting members 6 are fixed to the fixed part 7 by using an adhesive agent or the like.
Two magnets 11a and 11b are arranged to face one of the side faces of the lens holder 2 parallel to the radial direction of the optical disc (y direction), while two magnets 11c and 11d are arranged to face the other side face of the lens holder 2 parallel to the y direction. The magnets 11a-11d are attached to a yoke 12 made of magnetic material. Incidentally, the reference characters “20” in
The lens holder 2 has coil-winding protrusions 20 which protrude in the axial direction of the supporting members 6 from one side face of the lens holder 2 that is parallel to the radial direction of the optical disc (y direction) and farther from the fixed part 7 (shown in
Incidentally, the combination of N-poles and S-poles may also be set inversely to the example of
In the objective lens driving apparatus 50 configured as above, when electric current is fed through the first focusing coil 3 and the second focusing coil 4, driving force in the focusing direction is caused by the electromagnetic interaction with the magnets 11a-11d. When electric current is fed through the tracking coil 5, driving force in the tracking direction is caused by the electromagnetic interaction with the magnets 11a-11d. Further, by setting a difference between the electric current supplied to the first focusing coil 3 and the electric current supplied to the second focusing coil 4, a difference is caused between the driving force generated by the first focusing coil 3 and the driving force generated by the second focusing coil 4. Torque in the tilt direction can be achieved by the difference.
Principal parts of the first and second focusing coils 3 and 4 for generating the driving force in the focusing direction are the parts facing the magnets 11a-11d. Therefore, increasing the lengths of the parts of the first and second focusing coils 3 and 4 facing the magnets 11a-11d leads to enhancement of the driving force in the focusing direction.
According to this embodiment, each of the first and second focusing coils 3 and 4 is wound between the second supporting member fixation part 9b and the third supporting member fixation part 9c in regard to the optical axis direction of the objective lens 1 (z direction). With this configuration, the need of forming the gap between each focusing coil and the adjacent wire supporting part (in which the supporting member fixation parts are connected together in a plate-like shape) or between each focusing coil and the adjacent post (as in JP-2009-187619-A) can be eliminated.
Further, in this embodiment, the coil-winding protrusions 20 protrude in the axial direction of the supporting members 6 from the side face of the lens holder 2 parallel to the radial direction of the optical disc (y direction). With this configuration, end faces of the first and second focusing coils 3 and 4 far from the objective lens 1 in regard to the radial direction of the optical disc (y direction) can be situated at positions farther from the optical axis of the objective lens 1 than the coil-winding protrusions 20.
In cases where the coil-winding protrusions 20 protrude in directions parallel to the radial direction of the optical disc (y direction) from side faces of the lens holder 2 orthogonal to the radial direction of the optical disc (y direction) differently from this embodiment (hereinafter referred to as a “comparative example”), the coil-winding protrusions 20 interfere with the first and second focusing coils 3 and 4, and thus the end faces of the first and second focusing coils 3 and 4 far from the objective lens 1 in regard to the radial direction of the optical disc (y direction) cannot be situated at positions farther from the optical axis of the objective lens 1 than the coil-winding protrusions 20.
Specifically, as shown in
With this configuration, the lengths of the parts of the first and second focusing coils 3 and 4 facing the magnets 11a-11d can be set longer than in the comparative example, by which the driving force generated by the first and second focusing coils 3 and 4 can be increased.
Next, other effects of this embodiment will be explained below referring to
As shown in
Further, referring to
With this configuration, the winding of each of the first and second focusing coils 3 and 4 around the lens holder 2 can be carried out with ease by rotating the unshown nozzle (for supplying the coil wire) along a circular orbit (with a radius r satisfying r1<r<r2) in the space between the first circle c1 and the second circle c2.
In the aforementioned configuration (as in the background technology) in which the nozzle has to pass through the gap between each focusing coil and the adjacent wire supporting part (in which the supporting member fixation parts are connected together in a plate-like shape) and the gap between each focusing coil and the adjacent post, the rotation of the nozzle along a circular orbit requires a considerably wide gap between each focusing coil and the wire support part and between each focusing coil and the post. Securing such wide gaps is substantially impossible in consideration of the dimensions of the apparatus. Thus, the orbit of the nozzle is necessitated to be in a rectangular shape in the aforementioned configuration of the background technology.
In cases of such a rectangular orbit, the traveling speed of the nozzle drops at the corners of the rectangular orbit since the nozzle has to temporarily stop at each corner and restart moving in a different direction.
In contrast, in cases of a circular orbit (with a radius r satisfying r1<r<r2) as in this embodiment, the nozzle can be moved at a constant speed and the time necessary for the coil winding can be shortened considerably compared to the rectangular orbit. In the configuration of this embodiment, for example, the coil winding time can be reduced by approximately 30% by use of the circular orbit compared to the rectangular orbit. This enables a substantial reduction in the manufacturing cost of the optical pickup. Incidentally, the “circular orbit” is not necessarily required to be a perfect circle in the strict sense. The circular orbit can be a substantially circular orbit as long as the nozzle is allowed to move at a constant speed.
Next, a second embodiment of the present invention will be described with reference to
Each of the two side faces of the lens holder 22 orthogonal to the radial direction of the optical disc (y direction) is provided with winding frames 30 protruding in a direction separating from the objective lens 1. Each of the first and second focusing coils 23 and 24 is wound between the winding frames 30. The other configuration is equivalent to that in the first embodiment.
In this embodiment, the coil-winding protrusions 20 protrude in the axial direction of the supporting members 6 from the side face of the lens holder 22 parallel to the radial direction of the optical disc (y direction). Therefore, the winding frames 30 are allowed to protrude outward from each side face of the lens holder 22 orthogonal to the radial direction of the optical disc (y direction).
In the aforementioned case where the coil-winding protrusions 20 protrude in directions parallel to the radial direction of the optical disc (y direction) from the side faces of the lens holder 22 orthogonal to the radial direction of the optical disc (y direction) (as in the background technology) differently from this embodiment, the winding frames 30 cannot be formed to protrude outward from each side face of the lens holder 22 orthogonal to the radial direction of the optical disc (y direction) since the coil-winding protrusions 20 interfere with the winding frames 30.
In this embodiment, the outward protrusion of the winding frames 30 from each side face of the lens holder 22 orthogonal to the radial direction of the optical disc (y direction) is made possible by forming the coil-winding protrusions 20 to protrude in the axial direction of the supporting members 6. Consequently, the first and second focusing coils 23 and 24 are allowed to have longer parts extending in the radial direction of the optical disc (y direction) not only compared to the configuration of the background technology but also compared to the first embodiment.
Specifically, as shown in
With this configuration, the lengths of the parts of the first and second focusing coils 23 and 24 facing the magnets can be set still longer than in the first embodiment, by which the driving force generated by the first and second focusing coils 23 and 24 can be increased further.
It is to be noted that the present invention is not limited to the aforementioned embodiments, but covers various modifications. While, for illustrative purposes, those embodiments have been described specifically, the present invention is not necessarily limited to the specific forms disclosed. Thus, partial replacement is possible between the components of a certain embodiment and the components of another. Likewise, certain components can be added to or removed from the embodiments disclosed.
Note also that some or all of the aforementioned components, functions, processors, and the like can be implemented by hardware such as an integrated circuit or the like. Alternatively, those components, functions, and the like can be implemented by software as well. In the latter case, a processor can interpret and execute the programs designed to serve those functions. The programs, associated data tables, files, and the like can be stored on a stationary storage device such as a memory, a hard disk, and a solid state drive (SSD) or on a portable storage medium such as an integrated circuit card (ICC), an SD card, and a DVD.
Further note that the control lines and information lines shown above represent only those lines necessary to illustrate the present invention, not necessarily representing all the lines required in terms of products. Thus, it can be assumed that almost all the components are in fact interconnected.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-213381 | Sep 2012 | JP | national |
