JP4637225B2 - Optical pickup - Google Patents

Description

  The present invention relates to an optical pickup.

  There are a wide variety of optical pickups used in optical disk read / write devices, such as those equipped with only a single wavelength laser, those equipped with a three wavelength laser, and those equipped with a plurality of objective lenses. There are a wide variety of products equipped with optical pickups, such as electronic computers, audio equipment, and DVD players.

  An adhesive is used everywhere in assembling the optical pickup. For example, optical components such as a laser unit and a light detection unit are attached to the base with an adhesive. Three-dimensional adhesion has attracted attention as one of the adhesion techniques that facilitate the alignment of optical components with respect to the optical axis (Patent Documents 1 and 2).

  The adhesion structure described in Patent Document 1 is shown in FIG. The light detection unit 110 includes a holder 101 and a light receiving element 104 mounted on the holder 101, and is assembled to the base 108. The reason why the light receiving element 104 is mounted on the holder 101 is to perform alignment without touching the light receiving element 104. A flexible substrate 107 for extracting signals is connected to the light receiving element 104. The holder 101 has holes 103 formed in two places. The protrusion 102 of the base 108 is inserted into the hole 103 of the holder 101, and the adhesive 106 is filled between the protrusion 102 and the inner surface of the hole 103. The adhesive 106 is typically an ultraviolet curable adhesive.

  According to the bonding technique as described above, since the light detection unit 110 and the base 108 are not in direct contact with each other, the alignment of the light detection unit 110 with respect to the optical axis 105 can be performed in each of the XYZ directions. That is, positioning is easy and accuracy is improved. After the alignment, the photodetecting unit 110 can be fixed to the base 108 by filling the adhesive 106 between the protrusion 102 and the inner surface of the hole 103 and irradiating the adhesive 106 with ultraviolet rays.

A similar adhesive structure is disclosed in Patent Document 2. As shown in FIGS. 8A and 8B, the bonding structure of Patent Document 2 is different from the bonding structure of Patent Document 1 in that an adhesive 106 is filled around 360 ° of the protrusion 102 of the base 108.
JP 2007-226922 A Japanese Patent Laid-Open No. 2003-257049

  In the adhesive structure shown in FIG. 7, the adhesive 106 is filled only on one side of the protrusion 102. Therefore, when the adhesive 106 repeatedly expands and contracts due to ambient temperature changes and self-heating of the optical components, the position of the light detection unit 110 is likely to be displaced in the X direction perpendicular to the optical axis 105. Further, after the adhesive 106 is cured, when the chuck for holding the light detection unit 110 is removed, the light detection unit 110 moves in the X direction due to the influence of the curing shrinkage of the adhesive 106.

  On the other hand, in the adhesive structure shown in FIGS. 8A and 8B, since the adhesive 106 is filled around 360 ° around the protrusion 102, the displacement in the XY direction is relatively unlikely to occur. However, as shown in FIG. 8A, since the adhesive 106 is filled also in the gap 112 between the portion other than the protrusion 102 of the base 108 and the holder 101, a positional shift in the Z direction is likely to occur.

  As the positional deviation of the optical component increases, the possibility of an error increases. In particular, in an optical pickup using a short wavelength laser, an accuracy of several μm order is required for bonding between the base and the optical component, and therefore, the bonding structure needs to be reviewed.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup that is less likely to be displaced in position even when a temperature load is applied and that has high reliability.

That is, the present invention
A base having at least one set of component mounting surfaces facing each other in the Z direction parallel to the optical axis;
At least one set of adhesive surfaces facing each other, each of the set of adhesive surfaces facing each of the set of component mounting surfaces and attached to the base so as not to directly contact the base Optical components,
The adhesive filled in each of the gaps formed on one side and the other side in the Z direction by the one set of component mounting surfaces and the one set of bonding surfaces, and the base in the direction perpendicular to the optical axis An adhesive structure including an open space formed around the adhesive so as to prevent the adhesive from interposing between a base and the optical component;
An optical pickup including the above is provided.

  The optical pickup according to the present invention employs so-called three-dimensional bonding in which the base and the optical component are bonded so as not to directly contact each other. The adhesive structure according to the present invention is provided with an open space that prevents the adhesive from being filled between the base and the optical component in the direction perpendicular to the optical axis. This open space is a space formed around the adhesive. That is, no adhesive is interposed between the base and the optical component in the Z direction perpendicular to the optical axis.

  According to the adhesive structure as described above, even if the adhesive repeatedly expands and contracts, the optical component moves only in the Z direction parallel to the optical axis. Therefore, it is possible to suppress the displacement of the optical component in the plane perpendicular to the optical axis, which is fatal to the optical pickup. Further, since the adhesive is filled in each of the gaps formed on one side and the other side in the Z direction by the component mounting surface of the base and the adhesive surface of the optical component, the influence of the expansion and contraction of the adhesive Is offset in the Z direction, and even when the filling amount or thickness of the adhesive varies, the positional deviation in the Z direction can be minimized. As described above, according to the present invention, it is possible to provide an optical pickup in which the optical components are not easily displaced even when a temperature load is applied, and reading errors and writing errors are unlikely to occur.

(First embodiment)
FIG. 1 is a schematic block diagram showing a typical configuration of the optical pickup of the present invention. The optical pickup 10 includes a laser unit 12, a beam splitter 14, a collimator lens 16, a rising mirror 18, a diffraction grating 20, an objective lens 22, and a light detection unit 24 as an optical system. These optical components 12 to 24 are each attached to a base 26. The base 26 is moved by a servo motor (not shown) so that the objective lens 22 can scan the recording surface of the optical disk.

  The laser light emitted from the laser unit 12 passes through the beam splitter 14 and the collimating lens 16 and reaches the rising mirror 18. The traveling direction of the laser beam is changed by the rising mirror 18. The laser light passes through the diffraction grating 20 and the objective lens 22 and is applied to the recording surface of the optical disc (not shown). The laser light reflected by the recording surface travels in the opposite direction to the forward path, the traveling direction is changed by the beam splitter 14, and reaches the light detection unit 24. The light detection unit 24 converts the optical signal into an electrical signal.

  In the present embodiment, an adhesive is used to attach the laser unit 12 and the light detection unit 24 to the base 26. Hereinafter, a preferable adhesion structure between the base and the optical component in the optical pickup 10 will be described by taking an adhesion structure between the base 26 and the light detection unit 24 as an example.

  Note that the base shown in the drawings referred to in the following description represents only a part of the base 26 of the optical pickup 10 shown in FIG. The base 26 of the optical pickup 10 usually has a space for mounting optical components other than the light detection unit 24. By using the base 26 in common, it is easy to align each optical component with respect to the optical axis.

  2A is an exploded perspective view showing a state in which the light detection unit is removed from the base in the optical pickup shown in FIG. FIG. 2B is a top view of the light detection unit fixed to the base. FIG. 2C is a side view of the bonding structure between the base and the light detection unit.

  As shown in FIG. 2A, the light detection unit 24 includes a holder 30 and a light receiving element 32 mounted on the holder 30. The holder 30 is provided with a protrusion 34 that protrudes in a direction perpendicular to the optical axis 28 (X direction). The convex portions 34 are provided on both sides of the holder 30. The convex portion 34 forms a pair of bonding surfaces 30p and 30q facing each other. The base 26 is provided with a concave portion 27 for receiving the convex portion 34 of the holder 30. Corresponding to the protrusions 34, the recesses 27 are also provided on both sides in the X direction. The recess 27 forms a pair of component mounting surfaces 26p and 26q that face each other in the direction parallel to the optical axis 28 (Z direction).

  In the light detection unit 24, each of the pair of bonding surfaces 30p, 30q of the holder 30 faces each of the pair of component mounting surfaces 26p, 26q of the base 26, and the holder 30 is not in direct contact with the base 26. In addition, it is attached to the base 26. Thereby, the adhesion structure 40 shown in FIG. 2B and FIG. 2C is formed.

  In this specification, a direction parallel to the optical axis 28 is defined as a Z direction, and a plane perpendicular to the Z direction is defined as an XY plane. With respect to the XY plane, the horizontal direction of the light receiving element 32 constituting the light detection unit 24 is defined as the X direction and the vertical direction is defined as the Y direction. The X direction is also the direction in which the bonding structures 40 are arranged.

  The adhesive structure 40 includes a concave portion 27 of the base 26, a convex portion 34 of the holder 30, an adhesive 36 that plays a role of fixing the light detection unit 24 to the base 26, and the convex portion 34 and the adhesive 36 of the holder 30. And an open space 38 around. The component mounting surfaces 26p and 26q of the base 26 and the bonding surfaces 30p and 30q of the holder 30 form gaps on one side and the other side in the Z direction, and each of the gaps is filled with the adhesive 36. Yes. Since the adhesive structure 40 is provided on each of one side and the other side in the X direction perpendicular to the optical axis 28, the holder 30 of the light detection unit 24 can be reliably supported by the base 26.

  The open space 38 is a space for preventing the adhesive 36 from being filled between the base 26 and the light detection unit 24 in the direction perpendicular to the optical axis 28, and around the convex portion 34 of the holder 30. Is formed. When an XY cross section across the adhesive 36 is observed, an open space 38 exists at 360 ° around the adhesive 36. In other words, there is no adhesive straddling the base 26 and the holder 30 with respect to the X direction and the Y direction, and the base 26 and the light detection unit 24 are only on surfaces facing each other (part mounting surface and adhesive surface) with respect to the Z direction. Is glued. Further, the other surfaces (upper and lower surfaces) of the convex portion 34 other than the bonding surfaces 30p and 30q are exposed to the open space 38.

  According to such an adhesive structure 40, when the adhesive 36 expands and contracts, the light detection unit 24 moves only in the Z direction. Since the adhesive 36 can expand and contract relatively freely in the XY plane, the displacement of the light detection unit 24 in the XY direction is small even if it occurs. In addition, since the light detection unit 24 is bonded to the base 26 with the convex portion 34 sandwiched between the pair of component mounting surfaces 26p and 26q, the convex portion 34 is pressed from both sides in the Z direction when the adhesive 36 expands. It is. When the adhesive 36 contracts, the convex portion 34 is pulled from both sides in the Z direction. As a result, the influence of expansion and contraction of the adhesive 36 is offset, and the movement of the light detection unit 24 in the Z direction is also suppressed. Such an effect is caused when the thickness of the adhesive 36 varies according to the alignment of the light detection unit 24, or when the thickness of the adhesive 36 varies according to an error in the amount of adhesive supplied from the dispenser. But you can get it.

  A set of component mounting surfaces 26p and 26q of the base 26 are parallel to each other and substantially perpendicular to the optical axis 28. Similarly, the pair of bonding surfaces 30p and 30q of the holder 30 are also parallel to each other and perpendicular to the optical axis 28. In other words, the YZ cross section of the concave portion 27 of the base 26 is rectangular or U-shaped, and the YZ cross section of the convex portion 34 of the holder 30 is also rectangular. The light detection unit 24 is attached to the base 26 so that the component attachment surfaces 26p, 26q of the base 26 and the adhesive surfaces 30p, 30q of the holder 30 are arranged in parallel in the Z direction. In this way, the thickness of the adhesive 36 is substantially uniform in the XY plane, and the degree of expansion and contraction is also uniform in the XY plane. For this reason, the effect of preventing the displacement is further enhanced. Further, an effect of preventing the light detection unit 24 from rotating about the X direction as a rotation axis can be expected. Note that “substantially parallel” and “substantially vertical” mean that it is not necessary to be strictly parallel or vertical, since adjustment and adhesion in three dimensions are assumed.

  In the present embodiment, the light detection unit 24 is attached to the base 26 so that the convex portion 34 of the holder 30 is inserted into the concave portion 27 of the base 26. The base 26 supports the convex portion 34 of the holder 30 via an adhesive 36. In this way, it is possible to easily prevent the adhesive 36 from interposing the base 26 and the light detection unit 24 in the X direction. In other words, it is easy to create the open space 38 in the X direction (see FIG. 2B). The alignment of the light detection unit 24 with respect to the optical axis 28 is also easy.

  The adhesion structure 40 can be formed by the following procedure. First, the base 26 and the light detection unit 24 are prepared. The base 26 is typically made of a metal material such as an aluminum alloy, a magnesium alloy, or a zinc die cast. A resin material such as LCP (Liquid Crystal Polymer) may be used for the base 26. The holder 30 of the light detection unit 24 is also made of the same metal material or resin material. The light receiving element 32 to be mounted on the holder 30 may be an OEIC (Opto-Electronic IC) including a photodiode and an amplifier circuit.

  Next, alignment of the light detection unit 24 with respect to the optical axis 28 is performed. Next, the adhesive 36 is supplied by a dispenser to each of the gap between the component mounting surface 26p and the bonding surface 30p and the gap between the component mounting surface 26q and the bonding surface 30q. Finally, the adhesive 36 is cured by irradiating ultraviolet rays. In this way, the light detection unit 24 can be fixed to the base 26. When the viscosity of the adhesive 36 before curing is low, as shown in FIG. 2C, the adhesive 36 may protrude slightly from the adhesive surfaces 30p and 30q and hang down. However, according to the present embodiment, since there is a sufficient gap (open space 38) between the convex portion 34 and the concave portion 27, the possibility that the adhesive 36 is interposed between the convex portion 34 and the concave portion 27 in the Y direction is low. That is, the allowable error range of the filling amount is wide.

(Second Embodiment)
As shown in FIGS. 3A and 3B, this embodiment differs from the previous embodiment in that the base 46 has a recess 47 that penetrates in the Y direction. Other essential parts are common. The shape of the light detection unit 24 is partially changed so as to fit into the recess 47 of the base 46. As shown in FIG. 3C, an adhesive 36 is filled between the component mounting surfaces 46p and 46q of the base 46 and the adhesive surfaces 30p and 30q of the light detection unit 24, thereby forming an adhesive structure 50. .

  According to this embodiment, the concave portion 47 of the base 46 is a hollow portion 47 penetrating in the direction perpendicular to the optical axis 28 and the X direction, and the hollow portion 47 forms an open space 38 around the adhesive 36. Has been.

  As shown in FIG. 3D, when the amount of the adhesive filling is excessive, a part 136 of the adhesive 36 wraps under the convex portion 134 and the base 146 and the convex portion 134 are bonded in the Y direction. there is a possibility. On the other hand, according to the base 46 having the recess 47 cut out in the Y direction, even if the adhesive 36 hangs down until reaching the lower end 46e of the base 46 as shown in FIG. There can be no adhesive between the light detection unit 24 and the light detection unit 24 (projection 34). Therefore, even when the adhesive is excessively filled, the effect of preventing the displacement in the XY plane can be reliably obtained.

(Third embodiment)
Similar to the second embodiment, this embodiment also takes measures against dripping of the adhesive. Specifically, as shown in FIGS. 4A and 4B, in the present embodiment, the concave portion 57 of the base 56 includes a component holding portion 57a and an adhesive reservoir 57b. The component holding part 57a is a part having the component mounting surfaces 56p and 56q, and forms a space in which the convex portion 34 (the convex portion of the holder 30) of the light detection unit 24 is inserted. The adhesive reservoir 57b is a portion adjacent to the component holding portion 57a and forms a space that is wider in the Z direction than the component holding portion 57a. A space formed by the adhesive reservoir 57 b functions as an open space 38 around the adhesive 36.

  According to the present embodiment, the same effect as described in the second embodiment can be obtained. As shown in FIG. 4B, the base 56 and the light detection unit 24 (convex portion 34) are bonded to each other in the Y direction even when the adhesive 36 is excessively filled so as to wrap the convex portion 34 of the holder 30. Not. Further, by providing the bottomed recess 57, the strength of the base 56 can be maintained high.

  In the embodiment described above, the present invention is applied to the attachment of the light detection unit to the base, but the application target of the present invention is not limited to this. For example, the adhesive structure of the present invention can be applied to a laser unit 12 (see FIG. 1) including a laser diode. The laser unit 12 is also a typical optical component attached to the base with an adhesive.

  A sample 70 shown in FIG. 5 was produced. In this sample 70, a laser unit 74 is attached to a base 72 made of zinc die casting, and the adhesive 36 is filled only between the surfaces parallel to the optical axis 28. It is common to each described embodiment. Moreover, the point which the recessed part 73 of the base 72 is a hollow recessed part is the same as 2nd Embodiment.

  Next, a temperature load was applied to the sample 70, and the offset amount (positional deviation) of the optical axis 29 of the laser unit 74 relative to the optical axis 28 of the base 72 was measured with respect to the XY plane perpendicular to the optical axis 28. Specifically, the offset amount when the sample 70 was exposed to a -20 ° C, 25 ° C, and 70 ° C cooling cycle was measured. The results are shown in FIGS. 6A and 6B.

  FIG. 1 is the result of Sample No. The result of 2. The origin of the graph represents the position of the optical axis 28 of the base 72, and the data point represents the position of the optical axis 29 of the laser unit 74. This means that when the position of the optical axis 29 overlaps the origin, the position of the laser unit 74 relative to the base 72 is completely as designed.

  As shown in FIGS. 6A and 6B, when the sample 70 was exposed to a thermal cycle, the position of the optical axis 29 of the laser unit 74 moved about 1 μm from the position of 25 ° C. in the XY plane. That is, in the temperature range of −20 ° C. to 70 ° C., the offset amount of the laser unit 74 from the room temperature position could be suppressed to about 1 μm. Incidentally, an offset amount of about 5 μm is observed in the conventional product.

Schematic block diagram showing a typical configuration of the optical pickup of the present invention The disassembled perspective view of 1st Embodiment which shows the state which removed the photon detection unit from the base. Top view of the light detection unit fixed to the base Side view The disassembled perspective view of 2nd Embodiment which shows the state which removed the photon detection unit from the base. Top view of the light detection unit fixed to the base AA sectional view of the adhesion structure of a 2nd embodiment. Schematic diagram of an adhesive structure where no open space is formed The disassembled perspective view of 3rd Embodiment which shows the state which removed the photon detection unit from the base. Side view Schematic perspective view of the prepared sample Sample No. Graph showing the measurement result of 1 Sample No. Graph showing the measurement results of 2 Perspective view of conventional adhesive structure Front view of another conventional adhesive structure Cross-sectional view of the adhesive structure shown in FIG. 8A

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical pick-up 12 Laser unit 14 Beam splitter 16 Collimating lens 18 Rising mirror 20 Diffraction grating 22 Objective lens 24 Optical detection unit 26, 46 Base 26p, 26q, 46p, 46q Component attachment surface 27, 47, 57 Recess 28 Optical axis 30 Holder 30p, 30q Adhesion surface 32 Light receiving element 34 Protruding part 36 Adhesive 38 Open space 40, 50 Adhesive structure 47 Cut-out concave part 57a Component holding part 57b Adhesive reservoir

Claims (8)

A base having at least one set of component mounting surfaces facing each other in the Z direction parallel to the optical axis;
At least one set of adhesive surfaces facing each other, each of the one set of adhesive surfaces facing each of the one set of component mounting surfaces and attached to the base so as not to directly contact the base Optical components,
The adhesive filled in each of the gaps formed on one side and the other side in the Z direction by the one set of component mounting surfaces and the one set of bonding surfaces, and the base in the direction perpendicular to the optical axis An adhesive structure including an open space formed around the adhesive so as to prevent the adhesive from interposing between a base and the optical component;
With an optical pickup. The set of component mounting surfaces are parallel to each other and perpendicular to the optical axis;
The set of adhesive surfaces are parallel to each other;
2. The optical pickup according to claim 1, wherein the optical component is attached to the base such that the component attachment surface and the adhesive surface are arranged substantially in parallel along the Z direction. The base has a recess forming the set of component mounting surfaces;
The optical component has a convex portion forming the set of bonding surfaces,
The optical pickup according to claim 1, wherein the optical component is attached to the base so that the convex portion is inserted into the concave portion.   The optical pickup according to claim 1, wherein the adhesive structure is provided on each of one side and the other side in the X direction perpendicular to the optical axis.   The light according to claim 3, wherein the concave portion of the base is a hollow portion penetrating in the Y direction perpendicular to the optical axis and the X direction, and the open space is formed by the hollow portion. pick up. The concave portion of the base is adjacent to the component holding portion, forming a space in which the set of component mounting surfaces and the convex portion of the optical component are inserted, and the component An adhesive reservoir that forms a space extending in the Z direction from the holding portion,
The optical pickup according to claim 3, wherein a space formed by the adhesive reservoir functions as the open space.   There is no adhesive straddling the base and the optical component in the direction perpendicular to the Z direction, and the base and the optical component are only on the component mounting surface and the adhesive surface facing each other in the Z direction. The optical pickup according to any one of claims 1 to 6, wherein and are bonded together. The optical pickup according to claim 1, wherein the optical component is a laser unit including a laser diode, or a light detection unit including a holder and a light receiving element mounted on the holder.

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