BRIEF DESCRIPTION OF THE DRAWINGS
These and objects as well as advantages of the present invention will become clear by the following description of preferred embodiments of the present invention with reference to the accompanying drawings, wherein:
FIG. 1 is a decomposed structural perspective view (first embodiment) showing an embodiment of an optical pickup device in relation to the present invention;
FIGS. 2A to 2C are diagrams (second embodiment) showing an example of a bonding structure of an optical component 1 and an accommodation case 2 in FIG. 1;
FIGS. 3A and 3B are diagrams showing an example of a forming region of an adhesive 3 in FIG. 2;
FIGS. 4
a to 4G are diagrams (third embodiment) showing the other examples of a bonding structure of the optical component 1 and the accommodation case 2 in FIG. 1;
FIGS. 5A to 5D are diagrams (fourth embodiment) showing the other example of a bonding structure of the optical component 1 and the accommodation case 2 in FIG. 1;
FIGS. 6A and 6B are diagrams showing an example of a forming region of an adhesive 3 in FIGS. 5A to 5D;
FIGS. 7A to 7C are diagrams (fifth embodiment) showing the other example of a bonding structure of the optical component 1 and the accommodation case 2 in FIG. 1; and
FIGS. 8A and 8B are diagrams (sixth embodiment) showing the other example of a bonding structure of the optical component 1 and the accommodation case 2 in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of the present invention will be described with reference to the accompanying drawings.
First Embodiment
FIG. 1 is a decomposed structural perspective view showing a preferred embodiment of an optical pickup device 100 of the present invention. In FIG. 1, the optical pickup device of the present invention is built into an optical disk drive 101. The optical pickup device 100 fixes an optical component 1 of various kinds, a light emitting element 11 such as a laser diode, a photoelectric converting element 12, and an objective lens 13, etc. by mounting these elements to an accommodation case 2 (also defined as an accommodation case). An optical beam emitted from the light emitting element 11 is transmitted to the objective lens 13 via the optical component 1 of various kinds and is then condensed and radiated to an optical recording medium (optical disk) 102 provided opposed to the objective lens 13. Moreover, a reflected light from the optical disk 102 is condensed with the objective lens 13, transferred to the photoelectric converting element 12 via an optical component 1 of various kinds and then converted into an electric signal. In this case, an optical path (optical axis) for each optical component 1 is formed within a plane almost parallel to a surface of the optical disk 102, in other words, within a plane parallel to a placing surface of the optical pickup device 100 (or accommodation case 2) as will be understood from arrangement in FIG. 1. The optical pickup device 100 is driven with a motor not shown and moves in the radius direction of the optical disk 102 along a guide rail 14.
The optical component 1 includes various lenses such as a grating lens, a coupling lens, and a detector lens. These lenses give large influence on an optical transmission characteristic and must be maintained in higher positional accuracy at the optimum position on the optical path. Therefore, the optical component 1 fixed in direct with an adhesive supplied to the predetermined position of an accommodating part 20 in the accommodation case 2. In this case, in view of reduction in thickness of the optical disk drive 101, the optical pickup device 100 is formed thin through restriction on height and thickness (depth of accommodating part 20) thereof. Accordingly, each optical component 1 is constituted in the structure that it cannot be bonded in the bottom surface side and is bonded to the internal circumferential surface of the accommodation case 2 only at both side surfaces.
Various lenses considered as the optical component 1 are constituted with a die casting material mainly formed of any material of at least polyolefin and acryl. The accommodation case 2 is constituted with a die casting material mainly formed of any material of at least Zn, Mg, Al, and PPS (polyphenylen sulfide). Moreover, as an adhesive, a material that is hardened with irradiation of ultraviolet ray is used. This material is supplied into a gap between the optical component 1 and the accommodation case 2. This adhesive may be hardened, for example, with irradiation of the ultraviolet ray from the upper direction or the lower direction of the accommodation case 2.
For the optical pickup device 100, tolerance for mispositioning of the optical component 1 becomes more severe with further improvement in performance and thickness. Meanwhile, with further improvement in performance, heat generated from each optical element increases in quantity. If such heat is transferred to the adhesive 3 and the optical component 1 via the accommodation case 2, stress due to difference in the thermal expansion coefficients of members may be generated in the adhesive 3. Particularly, since the thin optical pickup device 100 described above has a structure that only both side surfaces of the optical component 1 are fixed to the accommodation case 2 with the adhesive 3, stress of the adhesive 3 increases. Such stress of the adhesive 3 is also generated with an environmental load. Such stresses bring about peeling and reduction in strength of the adhesive 3 and also cause mispositioning of the optical component 1. Therefore, it has been requested to provide a structure that can reduce as much as possible such stresses and does not easily generate mispositioning even if stresses are generated.
Second Embodiment
FIGS. 2A to 2C are diagrams showing an example of a bonding structure of the optical component 1 and the accommodation case 2 in the optical pickup device of FIG. 1.
FIG. 2A is a plan view observed from the upper part of the accommodation case 2 (inserting side of the optical component 1). FIGS. 2B and 2C are cross-sectional views observed from the plane perpendicular to the optical axis. The optical component 1 is arranged to the optimum position for the optical axis 10 within the accommodation case 2 and the side surfaces 1s in both sides parallel to the optical axis 10 of the optical component 1 and each side surface 2s of the accommodation case provided opposing to both side surfaces are bonded and fixed with the adhesive 3. In this case, a plane 1p in the optical axis direction of the optical component 1 is not in contact with a plane 2p in the optical axis side of the accommodation case 2 and are arranged in separation. In the arrangement described above, the optical pickup device of this embodiment is formed in the structure that stress of the adhesive 3 is reduced as much as possible even when environmental change occurs and that mispositioning (particularly, mispositioning in the optical axis direction) of the optical component 1 is not easily generated even if stress is generated.
In this embodiment, a recessed channel 4 to be filled with the adhesive is formed through the accommodation case 2 in the height (depth) direction at the center of the bonding surface in the optical axis direction for the side surface 2s as the bonding surface of the accommodation case 2 as shown in FIG. 2A. As a result, a larger bonding gap (b) for the optical component 1 is attained at the center in the optical axis direction as shown in the cross-section along A-A′ in FIG. 2B, while a smaller bonding gap (a) is attained at the end part in the optical axis direction as shown in the cross-section along B-B′ in FIG. 2C (a<b). In more concrete, the gap (a) equal to or less than 1 mm is preferable. Naturally, the adhesive 3 supplied to fill the gap is formed thick at the center and formed thin at the end part. In this case, the recessed channel 4 is formed in the shape to the stepped portion as a sloping surface and the side surface 2s to be bonded is formed in the shape almost symmetrical in the optical axis direction. Accordingly, the gap for bonding is made smaller almost symmetrically toward both end portions from the center in the optical axis direction.
According to the structure of the bonding surface in this embodiment, peeling of bonded area can be prevented by remarkably reducing stress that is assumed as a reason of peeling at the bonded area, because thickness of adhesive at the end part of the bonding surface (=a) is thinner than that in the structure of the related art where the bonding gap is formed in the uniform width. Moreover, since the adhesive at the center of the bonding surface (=b) is formed thick, sufficient bonding strength of the adhesive for the coated region and the optical component 1 can be assured. Furthermore, since the accommodation case 2 and its bonding surface for the optical component 1 are shaped almost symmetrically toward both end portions in the optical axis direction, if each member generates thermal expansion due to temperature change, expansion forces of these elements are balanced and therefore the optical component 1 is never mispositioned in the optical axis direction. In addition, since the surface 1p of the optical component 1 in the optical axis direction is never in contact with the surface 2p of the accommodation case 2, the optical component 1 is never mispositioned in the optical axis direction, even if the accommodation case 2 is thermally expanded.
Moreover, in this embodiment, the recessed channel 4 is shaped to form the stepped portion thereof as the sloping surface. Namely, the recessed channel 4 is formed to bring about the width (c) at the upper end of the sloping surface that is larger than the width (d) at the lower end of the sloping surface (c>d). Therefore, thickness of the adhesive at the stepped portion of the recessed channel 4 is gradually reduced to further reduce the stress thereof. Accordingly, peeling of the bonded area, reduction in bonding strength, and mispositioning of the optical component 1 resulting from such phenomena due to formation of the recessed channel can be prevented.
Moreover, the recessed channel 4 is formed through the depth direction of the accommodation case 2 in the identical shape of the cross-section. Accordingly, the ultraviolet ray is irradiated along the direction of the recessed channel 4 from the upper or lower direction of the accommodation case 2 to equally irradiate the adhesive 3 supplied to fill the gap. As a result, not only the stable hardening characteristic of the adhesive 3 can be assured but also easier hardening work of the adhesive can be achieved. Here, it may be possible that the recessed channel 4 is not formed through the depth direction of the accommodation case 2 and is formed in the identical shape of cross-section at least within the range of the bonding region. In this case, the ultraviolet ray is irradiated only from the selected one direction.
As the adhesive 3, an acrylic or epoxy system adhesive that is hardened with radiation of the ultraviolet ray is preferable. Moreover, the adhesive having the glass transition temperature resulting in a comparatively lower bonding strength may also be used. In addition, in order to improve the bonding strength, it is also preferable for the surface of the bonding region of the accommodation case 2 that the Blast processing that is generally conducted for the die-casting material is implemented to form fine crenelation in the average size of about several μm.
FIGS. 3A and 3B are diagrams showing an example of a forming region (bonding region) of the adhesive 3 in the bonding structure of FIGS. 2A to 2C. FIG. 3A is a perspective view of the entire part of the accommodation case 2. FIG. 3B is a perspective view showing the bonding region 3s at the side surface of the optical component 1 after the accommodation case 2 is removed. The adhesive 3 is never formed to the entire surface of the side surface is of the optical component 1 but is formed in the region other than the periphery of the side surface is. Namely, when sizes of the side surface is of the optical component 1 are determined that length in the optical axis direction is (k) and height is (h), and when sizes of the region 3s corresponding to above sizes are (e), and (f), respectively, relationships of e<k and f<h are determined. Therefore, the adhesive 3 is never adhered to the peripheral part of the side surface is, not deteriorating the surface 1p in the optical axis side of the optical component 1.
In addition, it is preferable that the region 3s is formed to satisfy the relationship of e>f for the sizes e and f. Namely, in the case where the size (e) in the optical axis direction of the region 3s of the adhesive is determined larger, the adhesive 3 is fully supplied covering the recessed channel 4 in the width direction thereof and bonding strength can be stabilized under the condition that the adhesive 3 reaches the region where the bonding gap=(a) is achieved. These sizes of the bonding region 3s may be controlled with amount of supply and supply position of the adhesive 3.
Third Embodiment
FIGS. 4A to 4G are plan views showing the other example of the bonding structure of the optical component 1 and the accommodation case 2 in the optical pickup device of FIG. 1. Like the second embodiment, the recessed channel 4 to be filled with the adhesive is formed in the height (depth) direction through the side surface to be bonded of the accommodation case 2. In this third embodiment, the recessed channel 4 is formed in various shapes. The bonding gap (b) at the center in the optical axis direction and the bonding gap (a) at both end portions are structured to result in the relationship of a<b and the adhesive fixing process is conducted using the adhesive 3.
In FIG. 4A, the recessed channel 4 is formed in the shape of character V, while in FIG. 4B, the recessed channel 4 is formed in the semi-elliptical shape, while in FIG. 4C, the recessed channel 4 is formed in the semi-circular shape. In FIG. 4D, the saw-tooth shape crenelation is provided at the bonding surface and the bonding gaps (a) and (b) are determined as the average values of crenelation. In FIG. 4E, the stepped portion of the recessed channel 4 is formed as the sharp sloping surface (namely, difference in sizes (c) and (d) is set extremely small). In FIG. 4F, width (c) of the recessed channel 4 is set in the relation of c<g for the shortest lens-to-lens distance (g) in the optical axis direction of the optical component 1. Moreover, in FIG. 4G, a size (e) in the optical axis direction of the region that is filled with the adhesive 3 is limited up to both sloping positions of the recessed channel 4 (namely, e<c).
Even in these examples of structure, since the adhesive (=a) at both end portions of the bonding surface is formed thin, peeling of the bonded area can be prevented by remarkably reducing stress that is considered as a cause of peeling at the bonded area. Moreover, since the bonding surface of the accommodation case 2 is formed almost symmetrically toward both end portions of the bonding surface, expansion force of each member due to temperature change is well balanced and the optical component 1 is never mispositioned in the optical axis direction.
Fourth Embodiment
FIGS. 5A to 5D are diagrams showing the other example of the bonding structure of the optical component 1 and the accommodation case 2. FIG. 5A is a plan view observed from the upper direction of the accommodation case 2, while FIGS. 5B and 5C are cross-sectional views observed from the plane perpendicular to the optical axis. In this fourth embodiment, the recessed channel 5 to be filled with the adhesive is formed through the optical component 1 in the height (depth) direction to the side surface 1s of both sides as the bonding surface of the optical component 1. The side surface 2s as the bonding surface of the accommodation case 2 should be formed flat. As shown in FIG. 5A, the recessed channel 5 is formed at the center in the optical axis direction in the shape that the stepped portion is formed as the sloping surface. As a result, a large bonding gap (b) is given for the accommodation case 2 at the center in the optical axis direction as shown in FIG. 5B, and a small bonding gap (a) is given at the end part in the optical axis direction as shown in FIG. 5C (a<b). Here, the recessed channel 5 may also be formed in the shape of each example of structure shown in the second embodiment or third embodiment. For example, length of the channel 5 (size along the bonding surface 2s of the accommodation case) may be set shorter then the radius of curvature of the lens formed to the optical component 1 as shown in FIG. 5D.
FIGS. 6A and 6B are diagrams showing an example of the forming region (bonding region) of the adhesive 3. FIG. 6A is an entire perspective view of the accommodation case 2 and FIG. 6B is a perspective view showing the bonding region 3s at the side surface of the optical component 1 after the accommodation case 2 is removed. Like the FIGS. 3A and 3B described above, the adhesive 3 is not formed to the entire surface of the side surface 1s of the optical component 1 but is formed in the region 3s other than the periphery. Moreover, when sizes of the region are defined as (e) and (f), the adhesive 3 is preferably formed under the condition satisfying the relationship of e>f.
In this embodiment, peeling of bonded area can be prevented by remarkably reducing stress that is a cause of peeling of the bonded area, because thickness of the adhesive (=a) at the end part of the bonding surface is rather small. Moreover, since the bonding surface of the optical component 1 is formed in the shape almost symmetrical toward both end portions of the bonding surface, expansion force of each member due to temperature change is well balanced and the optical component 1 is never mispositioned in the optical axis direction.
Fifth Embodiment
FIGS. 7A to 7C are diagrams (plan views) showing the other example of the bonding structure of the optical component 1 and the accommodation case 2 in the optical pickup device of FIG. 1. In this embodiment, the recessed channels 4, 5 to be filled with the adhesive are formed in both side surface 2s of the accommodation case 2 and the side surface is of the optical component 1. In FIGS. 7A and 7B, the recessed channels 4, 5 have equal width, while in FIG. 7C, the recessed channels 4, 5 have different widths. In any case described above, the larger bonding gap (b) is given at the center in the optical axis direction, while the smaller bonding gap (a) is given at the end part in the optical axis direction (a<b). This embodiment also provides the effect similar to that of the embodiments described above. Moreover, depth of the recessed channels 4, 5 that are required for obtaining the predetermined bonding gap (b) may be reduced to a half by forming the recessed channels to both accommodation case 2 and the optical component 1.
Sixth Embodiment
FIGS. 8A and 8B are diagrams showing the other example of the bonding structure of the optical component 1 and the accommodation case 2 in the optical pickup device of FIG. 1, namely the cross-sectional views thereof observed from the optical axis direction. FIG. 8A is the cross-sectional view where the upper and lower corners 2r of the accommodation case 2 are angled (chamfered) in order to make easier the inserting work of the optical component 1. In this case, the recessed channel is not shown but may be provided to any of the accommodation case 2 and the optical component 1. The adhesive 3 is supplied to the gap between these elements avoiding the corners 2r. FIG. 8B is the cross-sectional view where the side surface of the optical component 1 is never formed flat and includes a projected part 1t. In this case, bonding with the accommodation case 2 may be realized while the projected part it is left as it is, by forming the recessed channel 4 including the stepped portion that is equal to or larger than the projected part it is formed in the side of the accommodation case 2.
The structure of optical pickup device and material of each member described in above embodiments are only an example. The structures attained by modifying or combining as required the structures of the embodiments described above may also be considered as the objects of the present invention. The present invention may be adapted to the optical pickup device using inorganic materials such as the other metal materials and glasses as the materials of the accommodation case and the optical component.
Quality of recording and reproducing signals to and from an optical disk may be improved and more stable performance may also be assured for environmental change by introducing the optical pickup device described above into an optical disk drive.
While we have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to those skilled in the art, and we therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.
Patent Application
20080087802
