JP2006012203A - Optical element for optical pickup, and optical pickup using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element for an optical pickup composed of a so-called free-form surface lens which can be easily and accurately fixed in the proper direction with respect to a holder. <P>SOLUTION: The optical element 10 for the optical pickup is used by being fixed to the holder 30 and formed with a plurality of optical operating surfaces including at least an incident surface 17 and an exit surface 21, and at least one of these optical operating surfaces is composed of a rotationally asymmetrical curved surface, and light entered from the incident surface 17 exits from the exit surface 21 to converge to a recording medium 29. In this optical element 10, fixing parts 24a, 24b fixed to the holder 30 are constituted so as to have rotationally symmetrical shapes with respect to a 1st axis 25. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical element provided in an optical pickup of an optical disc drive apparatus for optically recording / reproducing information and an optical pickup using the optical element.

  In optical disk drive devices, the use of CDs that use lasers with a wavelength of 780 nm, DVDs that use lasers with a wavelength of 660 nm, and disks that use lasers with a wavelength of 405 nm, and higher density by shortening the wavelength are being promoted. . As for NA, the density has been increased by increasing CD from 0.45 to DVD to 0.6.

  As described above, when the wavelength is shortened and the NA is increased, the tolerance for various optical characteristics is reduced, and the demand for an objective lens that is a condensing optical element for condensing laser light on a recording medium is severe. Become. For example, although a semiconductor laser is used as the laser, the occurrence of chromatic aberration due to the wavelength variation becomes unacceptable, and in order to cancel the chromatic aberration, the objective lens needs to be configured with a plurality of positive and negative lenses.

  However, if the objective lens is composed of a plurality of lenses, the assemblability deteriorates, such as the need to align their optical axes. Moreover, since the number of parts increases, it tends to be disadvantageous in terms of cost.

  In order to avoid or reduce such an inconvenience, an objective lens made up of a so-called free-form surface lens having a rotationally asymmetric curved surface as shown in FIG. There is known an optical pickup in which the number of sheets can be reduced by using 101 even when the wavelength is short and the NA is high (see, for example, Patent Document 1). In FIG. 23, in order to align the direction with the other figures, the figure shown in Patent Document 1 is rotated 180 degrees so that the recording medium 102 faces up.

  The objective lens 101 refracts incident light 103 on a surface 105, then sequentially reflects the light on a surface 106 and a surface 107, and further refracts the light on a surface 108 to collect the emitted light 104 on the recording medium 102. The surfaces 105 to 108 are rotationally asymmetric curved surfaces.

  The objective lens 101 disclosed in Patent Document 1 is mounted on a holder of a lens actuator, and is supported so as to be movable in a direction substantially perpendicular to the recording medium 105 or across a track. The objective lens 101 receives a normal lens. Since the lower surfaces 105 and 107 are rotationally asymmetric free curved surfaces, the holder needs to be provided with a receiving portion formed of a curved surface or curved edge matched to the lower surfaces (Z-side) 105 and 107.

  However, it is difficult to manufacture a holder having a receiving part composed of a curved surface or a curved edge, and it is also difficult to measure the shape of the completed receiving part, so that it is difficult to feed back an error when it is manufactured with a mold. For this reason, an error is easily generated in the shape, and the sitting of the objective lens is deteriorated. To increase the accuracy, it is necessary to adjust the orientation of the objective lens when attaching it to the holder. However, there is a concern that play may occur and workability will deteriorate, making it impossible to fix the objective lens in the correct orientation. Is done.

  An optical element using a free curved surface as shown in FIG. 24 is also known, although it is not a lens for optical pickup (see, for example, Patent Document 2).

  The optical element 110 shown in FIG. 24 receives light from the surface 113 and emits light from the surface 111. During this time, the light is refracted by the surface 113 and reflected by the surface 111, and further the surface 112. And is refracted and transmitted through the surface 111. These surfaces 111 to 113 are rotationally asymmetric curved surfaces.

  In the optical element 110, fixing portions 116a and 116b are provided on the side surfaces 114 and 115, and the optical element 110 is fixed to a holder or the like using the fixing portions 116a and 116b.

  Therefore, if the technique disclosed in Patent Document 2 is applied to the objective lens 101 disclosed in Patent Document 1, a fixed portion is provided on the side surface of the objective lens 101, and an attachment surface of the fixed portion is provided in the holder, the objective lens 101 is provided. It becomes possible to fix it to the holder without rattling.

However, when the objective lens 101 is fixed to the holder, it is necessary to adjust the orientation of the objective lens 101 with high accuracy as described above. For this purpose, some adjustment mechanism is provided on the holder side that receives the fixing portion of the objective lens 101. Therefore, there is a concern that the apparatus will be increased in size.
Japanese Patent Application Laid-Open No. 2002-245331 JP-A-9-73005

  The first object of the present invention made in view of the above circumstances is to provide an optical element for an optical pickup comprising a so-called free-form surface lens that can be easily and accurately fixed to a holder in the correct orientation.

  Furthermore, a second object of the present invention is to provide an optical pickup capable of miniaturizing the apparatus by using the optical element for optical pickup described above.

The invention according to claim 1, which achieves the first object, is used while being fixed to a holder, and has a plurality of optical action surfaces including at least an entrance surface and an exit surface, and at least one of these optical action surfaces is rotated. In an optical element for an optical pickup that is formed of an asymmetric curved surface and emits light incident from the incident surface to the recording medium by exiting from the exit surface,
The fixing portion fixed to the holder has a rotationally symmetric shape with respect to the first axis.

  According to a second aspect of the present invention, in the optical element for an optical pickup according to the first aspect, the rotationally symmetric shape is a cylindrical shape.

  The invention according to claim 3 is the optical element for optical pickup according to claim 1, wherein the rotationally symmetric shape is a truncated cone shape.

  According to a fourth aspect of the present invention, in the optical element for an optical pickup according to the first aspect, the rotationally symmetric shape is formed by rotating a plane 180 degrees or more and less than 360 degrees around the first axis. It is characterized by having a shape.

  According to a fifth aspect of the present invention, in the optical element for an optical pickup according to any one of the first to fourth aspects, when the optical axis of the light emitted from the optical element is the second axis, the first And an angle formed by the cosine of the second axis is 90 degrees.

  According to a sixth aspect of the present invention, in the optical element for an optical pickup according to any one of the first to fifth aspects, the first axis is an optical axis of light emitted from the emission surface or an optical axis of the optical axis. It is characterized by intersecting the extension line.

  According to a seventh aspect of the present invention, in the optical element for an optical pickup according to any one of the first to sixth aspects, as the optical action surface, at least one reflecting surface in addition to the incident surface and the emitting surface. It is characterized by having.

  According to an eighth aspect of the present invention, in the optical element for an optical pickup according to the seventh aspect, the reflecting surface is a rotationally asymmetric curved surface.

Furthermore, the invention according to claim 9 for achieving the second object comprises at least an optical element for condensing incident light on a recording medium, a holder for fixing the optical element, and a moving mechanism for the holder. In the optical pickup provided,
The said optical element consists of the optical element for optical pick-ups as described in any one of Claims 1-8, It is characterized by the above-mentioned.

  According to a tenth aspect of the present invention, in the optical pickup according to the ninth aspect, the moving mechanism rotates and moves the holder about a third axis whose direction cosine is 90 degrees with the first axis. It is characterized by this.

The invention according to claim 11 that achieves the second object further includes an optical element for condensing incident light on a recording medium, a holder for fixing the optical element, and the holder movably supported. In an optical pickup comprising at least a first member and a second member for fixing the first member,
The optical element comprises the optical element for an optical pickup according to any one of claims 1 to 8,
The first member is fixed to the second member so as to be rotatable and adjustable around a fourth axis whose direction cosine is 90 degrees with the first axis.

  According to the optical element for an optical pickup of the present invention, since the fixed portion fixed to the holder has a rotationally symmetric shape with respect to the first axis, by rotating and adjusting around the first axis, Thus, it can be easily and accurately fixed in the correct orientation.

  In addition, according to the optical pickup of the present invention, since the optical pickup optical element having the holder fixing portion having a rotationally symmetric shape with respect to the first axis is used, there is no need for any adjustment mechanism on the holder side, and the optical pickup is used. The optical element can be easily and accurately fixed in the correct orientation with respect to the holder, and the optical pickup can be miniaturized.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
1 to 10 show a lens actuator of an optical pickup according to a first embodiment of the present invention. FIG. 1 is a perspective view, FIGS. 2 and 3 are perspective views with a cover removed, and FIG. FIG. 5 is a cross-sectional view taken along the line A-A in FIG. 4 (with a cover), FIG. 6 is an exploded perspective view, and FIG. 7 is a cross-sectional view taken along the line BB in FIG. 8 is a perspective view of the objective lens, FIG. 9 is an exploded perspective view of the objective lens and the holder portion, and FIG. 10 is a perspective view of a main part showing a modification of the objective lens.

  2 to 6, an objective lens 10, which is an optical element for optical pickup, focus coils 1a and 1b, and tracking coils 4a to 4h are bonded to a holder 30 made of a synthetic resin such as a liquid crystal polymer.

  The objective lens 10 is a so-called free-form surface lens. As shown in FIG. 5, the light is incident from the optical path 11, and the incident light is first refracted by the incident surface 17 and travels the optical path 12, and then the reflecting surface. 18 is reflected on the optical path 13, then reflected on the reflective surface 19 and travels on the optical path 14, further reflected on the reflective surface 20 and travels on the optical path 15, and finally refracted on the exit surface 21 to be refracted on the optical path. Proceeding to FIG. 16, spots are formed on the recording medium 29. Here, the optical axis which is the center of the optical paths 11 to 16 is in the same YZ plane. Further, the optical action surfaces of the incident surface 17, the reflecting surfaces 18 to 20, and the exit surface 21 are curved surfaces that are not rotationally symmetric and are free-form surfaces, and have a surface-symmetric shape with respect to the ZX plane that passes through the optical axis. ing.

  As shown in FIG. 8, at both ends in the X direction of the objective lens 10, rotationally symmetric columnar convex portions 24 a and 24 b with the axis 25 serving as the first axis as the rotation center are fixed to the holder 30. Is provided. As shown in FIG. 5, the axis 25 is on the extension line of the optical axis of the light emitted from the objective lens 10, which is the second axis, and extends in the X direction perpendicular to the optical path 16.

  As shown in FIG. 9, the holder 30 is provided with groove portions 35a and 35b. The bottom portions 36a and 36b (36a not shown) of the groove portions 35a and 35b have a half shape of the side surface of the cylinder, and the radius of the cylinder is about 10 to 20 μm larger than the radius of the convex portions 24a and 24b. ing. By fitting the convex portions 24a and 24b of the objective lens 10 to the bottom portions 36a and 36b of the groove portions 35a and 35b, the objective lens 10 can be rotated and adjusted around the axis 25 around the X axis indicated by the arrow 26. It becomes possible. The widths of the groove portions 35a and 35b are the same as the diameters of the bottom portions 36a and 36b. Thereby, the objective lens 10 is rotationally adjusted as indicated by an arrow 26 and is fixed to the holder 30 in an accurate direction. After adjustment, the objective lens 10 is bonded to the holder 30 so as not to move.

  At the bottom of the Z-end of the holder 30 to which the objective lens 10 is fixed, as shown in FIG.

  The tracking coils 4a to 4f are inserted into the protrusions 32a to 32f provided in the holder 30 at the central hole portion thereof, and are thereby positioned and bonded and fixed to the holder 30.

  The focus coils 1a and 1b are bonded and fixed to the surfaces of the tracking coils 4a to 4f. At this time, the focus coils 1a and 1b are inserted in the projections 31a and 31b provided in the holder 30 in the holes 3a and 3b, and the Z direction is positioned, and the X direction is positioned and fixed by a jig.

  The holder 30 is provided with protrusions 33a and 33b at both ends in the X direction. The protrusions 33a and 33b are provided with holes 34a to 34f, and six wire springs 6a to 6f made of beryllium copper are inserted into and bonded to the holes 34a to 34f. The wire springs 6a to 6f have a circular cross-sectional shape and are all arranged in parallel. Here, the four wire springs 6a, 6c, 6d, and 6f are the same spring, and the remaining two wire springs 6b and 6e are the same spring having a smaller spring constant than the previous four. The wire springs 6a and 6d, the wire springs 6b and 6e, and the wire springs 6c and 6f are in the same XY plane, and the distance in the X direction of the spring in the plane is the same for the wire springs 6a and 6d and the wire springs 6c and 6f. The distance between the wire springs 6b and 6e is smaller than the former.

  The six wire springs 6a to 6f are soldered to the focus coils 1a and 1b and the tracking coils 4a to 4h at the end (Y + side end) on the holder 30 side. That is, the focus coils 1b and 1d are connected in series, and both ends thereof are soldered to the wire springs 6b and 6e, and the tracking coils 4a to 4h are divided into two sets different from the normal, and the tracking coils 4a and 4b. , 4e, 4f are connected in series and soldered to wire springs 6a and 6d, and tracking coils 4c, 4d, 4g, and 4h are connected in a row and soldered to wire springs 6c and 6f.

  The Y-direction ends of the six wire springs 6a to 6f are fixed to the spring pocket 7, and further inserted into the holes 43a to 43f of the substrate 41 and soldered. The spring bush 7 is provided with recesses 8a and 8b, and the portions are filled with silicone gel to damp the wire springs 6a to 6f. Although not shown in the drawing, the spring spring 7 is provided with holes for passing the wire springs 6a to 6f in the portions corresponding to the bottoms (Y-direction) of the recesses 8a and 8b, similarly to the holder 30 and the substrate 41. .

  As shown in FIG. 3, the substrate 41 is positioned by fitting the hole 42 into the convex portion 9 provided in the spring pocket 7. The holder 30 is supported by the spring spacer 7 by six wire springs 6a to 6f so as to be movable in a direction substantially perpendicular to the recording medium 29 (Z direction) and a direction crossing the track of the recording medium 29 (X direction). become. The substrate 41 is connected to an external electric circuit, and the focus coils 1a and 1b and the tracking coils 4a to 4b are connected to the external electric circuit via six wire springs 6a to 6f.

  The spring 7 is fixed to an iron base 44. The base 44 is provided with a rising portion 45a, and its Z + end side is formed into a U shape by bent portions 46a and 46b formed on both sides in the X direction. The Y direction is positioned, and the Z direction is positioned on the bottom surface of the base 44 (surface extending in the XY direction). Further, the base 44 is provided with a rising portion 45b having a similar shape so as to face the rising portion 45a in the Y direction, and the Z + end side thereof is bent by the bent portions 46c and 46d formed on both sides in the X direction. It has a U shape. Magnets 47a and 47b are bonded to the opposing surfaces of the raised portions 45a and 45b.

  The polarity of the magnets 47a and 47b and the mechanism of driving force generation will be described in the magnetic circuit on the magnet 47a side.

  As shown in FIGS. 5 and 6, the magnet 47a has, for example, a Z-side on the surface facing the focus coil 1a and the tracking coils 4a to 4d and an S-pole on the Z + side. As indicated by an arrow 54, the magnetic field is generated so as to exit from the N pole on the surface of the magnet 47a and return to the S pole on the surface. As a result, as shown in FIG. 7, a reverse magnetic field is applied to the sides 2a and 2b of the focus coil 1a. Here, since the direction of the current flowing through the focus coil 1a is reversed on the sides 2a and 2b, the driving force generated on the sides 2a and 2b is the same direction in the Z direction, and the focus direction (the vertical direction of the recording medium 29). The driving force is generated.

  As shown in FIG. 4, since the magnet 47a has an S + pole in the Y + direction and an N pole in the Y− direction at the Z + end, the magnetic field from the N pole passes through the rising portion 45a and is bent. 46a and 46b appear as N poles and return to the S poles on the surface of the magnet 47a as indicated by arrows 53a and 53b. As a result, as shown in FIG. 7, a magnetic field in the opposite direction reaches the sides 5e and 5f of the tracking coil 4c. Here, since the direction of the current flowing through the tracking coil 4c is reversed at the sides 5e and 5f, the driving force generated at the sides 5e and 5f has the same direction in the X direction, and the tracking direction (crosses the track of the recording medium 29). Direction) is generated. Similarly, the tracking coil 4d generates a driving force in the direction in which the sides 5g and 5h cross the track.

  Although the polarities are reversed, the tracking coils 4a and 4b similarly generate a driving force in the direction in which the sides 5a to 5d cross the track. Depending on the strength of the magnet 47a and the like, the magnetic field of the magnetic pole appearing at the tips of the bent portions 46a and 46b through the rising portion 45a may be weak. Even in that case, the magnetic field of the arrow 54 directly coming out from the surface of the magnet 47a is strong, and this magnetic field causes the magnetic field in the same direction as the magnetic field of the previous arrows 53a and 53b to be applied to the sides 5b, 5c, 5f and 5g of the tracking coils 4a to 4d. In addition, there is no problem because a driving force in a direction crossing the track is generated.

  The magnet 47b is arranged so that the magnetic poles facing the magnet 47a are different from each other, and generates the same driving force. Here, since the magnets 47a and 47b have opposite polarities, a magnetic field is generated between the magnets 47a and 47b as shown by an arrow 55 in FIG. 4, and this magnetic field is also the above-described magnetic fields 53a and 53b. , 54 in the same direction, there is no problem.

  By the way, as described above, the tracking coils 4a to 4h can flow currents independently to the tracking coils 4a, 4b, 4e, and 4f and the tracking coils 4c, 4d, 4g, and 4h. Therefore, if the tracking coils 4a, 4b, 4e, 4f and the tracking coils 4c, 4d, 4g, 4h are supplied with current so as to generate the same driving force, the holder 30 exerts the driving force in the tracking direction (Z direction). Receive and move. Further, if there is a difference between the driving force generated in the tracking coils 4a, 4b, 4e, 4f and the driving force generated in the tracking coils 4c, 4d, 4g, 4h, for example, the tracking coil indicated by the arrow 56a in FIG. If the driving force of 4a, 4b, 4e, 4f is reduced and the driving force of the tracking coils 4c, 4d, 4g, 4h indicated by the arrow 56b is increased, the holder 30 moves greatly toward the larger driving force. 30 rotates around the Y axis, which is the third axis, as indicated by an arrow 57. Therefore, if this is utilized, the movement of adjusting the tilt of the objective lens 10 can be performed. Note that the driving force generated by the tracking coils 4a, 4b, 4e, 4f and the tracking coils 4c, 4d, 4g, 4h can be reversed in some cases.

  A stainless steel cover 40 is fixed to the base 44 so as to cover the holder 30. As shown in FIG. 1, the cover 40 also covers the upper side of the projections 33a and 33b of the holder 30 on the Z + side. The holder 30 moves in the Z + direction, and the Z + ends 38a and 38b of the projections 33a and 33b. (See FIG. 4) abuts on the cover 40, thereby functioning as a stopper for limiting the amount of movement.

  The drive mechanism of the objective lens 10 configured as described above is referred to as a lens actuator. Although not shown, this lens actuator is fixed to an optical pickup body having an optical system composed of a laser diode, a photodetector, a prism and the like.

  Next, the operation of the optical pickup according to the present embodiment configured as described above will be described.

  Laser light emitted from a laser diode (not shown) enters the objective lens 10 from the optical path 11 after passing through several prisms. At this time, the diaphragm 37 provided in the holder 30 restricts unnecessary light from entering the objective lens 10. The laser light incident on the objective lens 10 is emitted from the optical path 16 and forms a spot on the recording medium 29.

  The reflected light from the recording medium 29 returns to the optical system (not shown) through the objective lens 10 again, passes through several prisms, etc., and is received by the photodetector, and a focus error, tracking error, and recording signal are generated. At the same time, the inclination of the objective lens 10 about the Y axis with respect to the recording medium 29 is also detected.

  Here, when a focus error is detected, a current is passed through the focus coils 1 a and 1 b to drive the holder 30 in a direction perpendicular to the recording medium 29. When a tracking error is detected, a current is passed through the tracking coils 4a to 4h to drive the holder 30 in a direction crossing the track of the recording medium 29, or in a radial direction when the recording medium 29 is a circular disk. . Further, when accessing different tracks, the holder 30 is driven in the radial direction of the recording medium 29 together with the lens actuator by a driving means (not shown). As described above, the holder 30 and the objective lens 10 fixed thereto are subjected to focus control, tracking control, and access control.

  Further, when it is detected that the optical path 16 of the objective lens 10 is not perpendicular to the recording medium 29 due to the deflection of the recording medium 29 and is tilted around the Y axis, as described above, tracking is performed. The current flowing through the coils 4a, 4b, 4e, 4f and the tracking coils 4c, 4d, 4g, 4h is adjusted to rotate the holder 30 around the Y axis, so that the optical path 16 is perpendicular to the recording medium 29. The inclination of the objective lens 10 is adjusted so that Here, the tilt adjustment of the objective lens 10 is only in the direction around the Y axis. However, when the recording medium 29 is a disk, there is no problem because the main deflection is from the center toward the outer periphery.

  According to the present embodiment, since the objective lens 10 is provided with the cylindrical convex portions 24a and 24b that are rotationally symmetric fixed portions with respect to the first axis 25, the objective lens 10 having a rotationally asymmetric optical action surface is used. In this case, the objective lens 10 can be easily fixed, and the optical path 16 of the light emitted from the objective lens 10 can be accurately perpendicular to the recording medium 29 by rotating and adjusting the objective lens 10 about the rotational symmetry axis 25. Can be fixed with high accuracy.

  The convex portions 24a and 24b of the objective lens 10 are arranged in the X direction, and the lens actuator on which the objective lens 10 is mounted can be driven to rotate around the Y axis, and the convex portions 24a and 24b rotate. The angle formed between the symmetry axis 25 and the direction cosine of the rotation axis (Y axis) of the lens actuator is 90 degrees. Therefore, the objective lens 10 is accurately adjusted when fixed about the X axis and is corrected by the lens actuator when used about the Y axis, so that the angle is accurately adjusted in either direction. It becomes a high-performance device. In addition, since the Y axis is corrected at the time of use, the accuracy at the time of fixing can be lowered, the assemblability can be improved, and the assembling cost can be reduced.

  Furthermore, since the convex portions 24a and 24b are formed in a cylindrical shape, the mold for manufacturing the objective lens 10 can be easily processed and can be easily measured, so that the accuracy of the mold can be easily increased. The precision objective lens 10 can be easily and inexpensively manufactured. Further, by forming the convex portions 24a, 24b in a cylindrical shape, the bottom portions 36a, 36b of the groove portions 35a, 35b of the holder 30 that receives the convex portions 24a, 24b can also be formed in a cylindrical side surface shape, so that highly accurate bottom portions 36a, 36b can be realized at low cost. .

  Further, the axis 25 of the convex portions 24a and 24b is perpendicular to the optical path 16 of the light emitted from the objective lens 10, and the optical path 16 is perpendicular to the recording medium 29. Therefore, the axis 25 is parallel to the recording medium surface. It becomes. Therefore, when the objective lens 10 is rotationally adjusted around the axis 25, the emitted light moves in a plane perpendicular to the recording medium 29 without being inclined with respect to the recording medium 29, and therefore, the occurrence of aberration is small and adjustment is easy. Can be done.

  In addition, since the axis 25 intersects the extension line of the optical path 16 of the emitted light, no matter which direction the objective lens 10 is rotated, the change in the distance between the exit surface 21 of the objective lens 10 and the recording medium 29 is changed. Are the same, and the adjustability is good. When the axis 25 does not intersect with the extended line of the optical path 16 of the emitted light, the emission surface 21 of the objective lens 10 approaches the recording medium 29 when rotated in one direction, and is emitted when rotated in the opposite direction. Since the surface 21 is separated from the recording medium 29, the amount of movement of the emitted light changes depending on the rotation direction, and the adjustability is deteriorated.

  In the present embodiment, the rotationally symmetric axis 25 of the convex portions 24a and 24b, which are fixed portions, and the rotational axis (Y axis) of the lens actuator are orthogonal to each other. The convex portions 24a and 24b may be aligned with the direction of the rotation axis of the lens actuator. This eliminates the effect of adjusting the angles in the different directions described above, but the objective lens 10 can be adjusted and fixed to the holder 30 in the correct orientation, so that the lens actuator is rotated for the correction. There is no need. Therefore, the amount of rotation of the lens actuator can be reduced, and its characteristics can be improved. In other words, when the amount of rotation of the lens actuator increases, the resonance increases and the change in sensitivity increases and the characteristics deteriorate with the amount of rotation. Therefore, by reducing the amount of rotation, the characteristics of the lens actuator can be reduced. Can be improved.

  Further, the fixed portion formed on the objective lens 10 may have a shape in which columnar convex portions 26a and 26b having different radii are connected stepwise as shown in a partial detail view in FIG.

(Second Embodiment)
11 to 16 show the main part of the lens actuator of the optical pickup according to the second embodiment of the present invention. FIG. 11 is a perspective view of the objective lens, FIG. 12 is a perspective view of the movable part, and FIG. FIG. 14 is a diagram illustrating the main part of the holder fixing portion of the objective lens, FIG. 15 is an explanatory diagram of the adjustment mechanism of the objective lens, and FIG. 16 is the objective lens of the holder. It is a figure which shows the modification of a fixing | fixed part. The same parts as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  This embodiment is different from the first embodiment in the shape of the fixing portion of the objective lens 10. That is, as shown in FIG. 11, convex portions 61a and 61b, which are fixed portions, are provided at both ends of the objective lens 10 in the X direction. The convex portions 61a and 61b are not circular columnar shapes as in the first embodiment, but are rotationally symmetric truncated cone shapes around the axis 25. The objective lens 10 is the same as the first embodiment except for the convex portions 61a and 61b, and is a so-called free-form surface lens.

  The objective lens 10 is attached to a holder 30 as shown in FIG. Here, as shown in FIG. 12 and FIG. 13, a gap is provided between the side surfaces 22 and 23 of the objective lens 10 and the wall portions 64 a and 64 b of the holder 30 facing each of them. The objective lens 10 is fixed to the grooves 62a and 62b provided in the holder 30 at the convex portions 61a and 61b. The bottom portions 63a and 63b of the groove portions 62a and 62b have a cylindrical side surface shape as shown in FIGS.

  As shown in FIG. 14, the radii of the bottom portions 63a and 63b are set such that the objective lens 10 is arranged at the center in the X direction of the holder 30, that is, the gap between the side surface 22 of the objective lens 10 and the wall portion 64a of the holder 30 and the objective. When the objective lens 10 is arranged on the holder 30 with the same clearance between the side surface 23 of the lens 10 and the wall portion 64b of the holder 30, the radius becomes larger than the radius 67 of the convex portions 61a and 61b in contact with the bottom portions 63a and 63b. Yes. The objective lens 10 is fixed to the holder 30 by being rotated around the X axis as indicated by an arrow 26 in FIG. 14 with the convex portions 61a and 61b in contact with the bottom portions 63a and 63b.

  Furthermore, in the present embodiment, the objective lens 10 is also rotated and adjusted around the Y axis. FIG. 15A shows that the objective lens 10 is at the center of the holder 30 in the X direction, the optical axis of the optical path 16 is perpendicular to the recording medium, and the angle formed with the Z direction is zero. In FIG. 15, the optical axis of the optical path 16 is drawn to be extended, and all components are schematically shown for convenience of explanation.

  Here, as shown in FIG. 15B, when the objective lens 10 is shifted in the direction of the arrow 65 (X-direction), a portion having a large radius of the frustoconical convex portion 61a is formed at the bottom 63a of the holder 30. On the contrary, at the bottom 63b, a portion with a small radius of the frustoconical convex portion 61b comes into contact, and as a result, the objective lens 10 is tilted around the Y axis as indicated by an arrow 68. If the objective lens 10 is moved in the reverse direction, it rotates in the reverse direction. Thereby, the objective lens 10 is also rotationally adjusted around the Y axis, and is fixed to the holder 30 in the correct orientation.

  In FIG. 15, the amount of movement of the objective lens 10 is drawn large for convenience of explanation, but the actual amount of tilt adjustment is small, and the amount of movement is also small. Further, in FIG. 14, the difference between the radius of the bottom 63a and the radius of the convex portion 61a is drawn large, but this difference is also slight in practice.

  Other configurations and operations are substantially the same as those of the first embodiment.

  According to the present embodiment, the shape of the convex portions 61a and 61b that fix the objective lens 10 to the holder 30 is a truncated cone shape, so that the objective lens 10 is placed on the axis of the rotationally symmetric axis 25 of the convex portions 61a and 61b. Not only the rotation but also the rotation around the axis orthogonal to the symmetry axis 25 can be adjusted, and the objective lens 10 can be fixed to the holder 30 with higher accuracy.

  In the present embodiment, the shape of the fixing portion of the holder 30 that receives the convex portions 61a and 61b of the objective lens 10 is not limited to the cylindrical side surface shape, and various modifications are possible. For example, as shown in FIG. In addition, a V-shaped groove 66 may be used.

(Third embodiment)
FIG. 17 is a perspective view of the lens actuator of the optical pickup according to the third embodiment of the present invention, and corresponds to FIG. 3 of the first embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  In the present embodiment, the holder 30 is supported by four wire springs 6a to 6d. Accordingly, both ends of the focus coils 1b and 1d connected in series are connected to the wire springs 6b and 6d, and both ends of the tracking coils 4a to 4h connected in series are connected to the wire springs 6a and 6c. Unlike the first embodiment, the tracking coils 4a to 4h are not divided into two sets.

  Further, the Y-direction ends of the wire springs 6a to 6d are not fixed to the spring pocket 7, but are fixed to the substrate 41 only by soldering. Accordingly, in the present embodiment, the substrate 41 constitutes the first member. The spring pocket 7 is provided with recesses 8a and 8b (see FIG. 2) penetrating in the Y direction. The substrate 41 is fixed by inserting a hole 72 provided in the substrate 41 into a columnar protrusion 71 provided in the spring pocket 7. Therefore, in this embodiment, the spring 7 constitutes the second member. The rotational symmetry axis 73 of the cylindrical projection 71 is in the Y-axis direction, and the angle formed between the cosine of the direction and the rotational symmetry axis 25 extending in the X-axis direction of the cylindrical convex portions 24a and 24b of the objective lens 10 is 90. It is a degree.

  In a state where the substrate 41 is inserted into the cylindrical protrusion 71 of the spring pocket 7, the wire springs 6 a to 6 d are inserted and fixed to the holder 30 and the substrate 41. Thereafter, the spring 7 is fixed to the base 44. Here, the substrate 41 is rotationally adjusted as indicated by an arrow 74 around the axis 73 which is the fourth axis, that is, the Y axis, with the hole 72 fitted into the cylindrical projection 71, whereby the objective lens 10 is The direction around the axis is correctly adjusted, and after the adjustment, the substrate 41 is bonded and fixed to the spring pocket 7. The fitting between the hole 72 and the columnar protrusion 71 is a clearance fit in which the difference between the diameters of the hole 72 and the columnar protrusion 71 is about 10 μm so that the substrate 41 can rotate and there is no rattling. Yes. In some cases, a loose interference fit with a difference in diameter of about 0 to 10 μm may be used. After bonding, the recesses 8a and 8b are filled with silicone gel.

  The objective lens 10 is rotationally adjusted around the Y axis and fixed, but unlike the first embodiment, the lens actuator detects the inclination around the Y axis and rotates the holder 30. There is no function.

  Other configurations and operations are substantially the same as those of the first embodiment.

  According to the present embodiment, the mechanism for adjusting the inclination of the objective lens 10 of the lens actuator, which is composed of the hole 72 of the substrate 41 and the cylindrical protrusion 71 of the spring 7, rotates only about one axis (Y axis). The angle formed between the cosine of the shaft 73 and the rotationally symmetric axis 25 extending in the X-axis direction of the cylindrical convex portions 24a and 24b of the objective lens 10 is 90 degrees. , And the inclination in all directions can be adjusted, whereby the objective lens 10 can be fixed in the correct orientation.

  Normally, a mechanism for adjusting the tilt of the lens actuator is provided around two axes whose direction cosine forms an angle of 90 degrees, but in this embodiment, the mechanism for adjusting the tilt of the lens actuator is provided around one axis. Therefore, the adjustment mechanism can be simplified, and the cost and size of the apparatus can be reduced accordingly.

(Fourth embodiment)
FIG. 18 is a perspective view of the objective lens in the lens actuator of the optical pickup according to the fourth embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  In the present embodiment, the shape of the fixed portion of the objective lens 10 is different from that of the first embodiment. That is, in the present embodiment, the convex portion 81 which is a fixed portion is provided only at one end of the Y-direction end, not at both ends of the objective lens 10 in the X direction. The convex portion 81 has a cylindrical shape with a shaft 82 that is a first axis extending in the Y-axis direction as a rotationally symmetric axis. The objective lens 10 is the same as that of the first embodiment except for the convex portion 81, and is a so-called free-form surface lens.

  The objective lens 10 is fixed to the holder 30 (not shown) using the convex portion 81, and at that time, the objective lens 10 is rotated and adjusted in a correct direction around the shaft 82.

  Other configurations and operations are substantially the same as those of the first embodiment.

  According to the present embodiment, since the objective lens 10 is fixed to the holder 30 at one place, the apparatus can be downsized. The direction of the rotationally symmetric axis 82 is the Y-axis direction, which is different from the X-axis direction of the first to third embodiments, but the adjustment direction depending on the formation position of the convex portion 81 should be set as appropriate. Can do. For example, depending on the design of the objective lens 10 and other optical systems, when the allowable amount of tilt around the X axis of the objective lens 10 and the allowable amount of tilt around the Y axis are not the same, The strict side of the allowable amount can be adjusted for rotation. When the lens actuator is provided with a rotation mechanism as in the first embodiment, or when the fixed portions of the wire springs 6a to 6d are rotated and adjusted by the spring 7 as in the third embodiment, the location and mechanism Since there is a direction in which the rotation adjustment mechanism is easily provided due to restrictions, it may be determined in consideration of this.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, the objective lens 10 may have various shapes other than those described above, and may have a shape that is not plane-symmetric, for example. Moreover, the number of reflective surfaces can also be set arbitrarily. Furthermore, the curved optical action surface of the objective lens 10 is not limited to a rotationally asymmetric curved surface, and may include a rotationally symmetric curved surface, or a diffraction grating may be formed on the optical action surface. In the above embodiment, the optical axes of all the optical paths in the objective lens 10 are in the same plane, but they may not be in the same plane.

  Further, the shape of the fixed portion of the objective lens 10 can be variously modified such as a shape obtained by rotating a spherical surface or a curve. That is, the fixing portion only needs to have a rotationally symmetric shape only for the portion used for fixing. For example, as shown in FIG. 19, a rectangular parallelepiped shape that is not rotationally symmetric is provided at the tip of the rotationally symmetrical cylindrical convex portions 81a and 81b.鍔 82a, 82b can also be provided. In this case, for example, as shown in FIG. 20, the holder 30 has groove portions 84a, 82a, 82b for accommodating the flanges 82a, 82b in the X direction ahead of the groove portions 83a, 83b to which the convex portions 81a, 81b of the objective lens 10 are fixed. 84b is formed, and the objective lens 10 is accurately positioned in the X direction and fixed to the holder 30 by the groove portions 84a and 84b and the flanges 82a and 82b.

  Furthermore, as shown in FIG. 21, space portions 92a and 92b (92b not shown) can be provided at the centers of the convex portions 91a and 91b that are the fixing portions of the objective lens 10. Thus, if the space portions 92a and 92b are provided, the radii of the convex portions 91a and 91b can be increased with the same mass, and the rigidity of the convex portions 91a and 91b can be increased.

  Further, as shown in FIG. 22, convex portions 96a and 96b (96b not shown) that are fixed portions of the objective lens 10 are rotated by 180 degrees around the rotational symmetry axis 99 that is the first axis. It can also be. That is, the convex portion 96a will be described in detail. The convex portion 96a is a shape obtained by rotating the hatched surface 97a around the rotation axis 99 with a rotation angle 98 of 180 degrees and using the curved surface. The objective lens 10 is adjusted and fixed. The rotation angle 98 is preferably 180 degrees or more and less than 360 degrees. The convex portion 96b (not shown) has the same shape.

  Further, the lens actuator can be variously changed. For example, in the third embodiment, a rotation adjusting mechanism including a hole 72 provided in the substrate 41 and a columnar protrusion 71 provided in the spring pocket 7 between the substrate 41 to which the wire springs 6 a to 6 d are fixed and the spring pocket 7. However, an adjustment mechanism may be provided between the spring bush 7 and the base 44. Further, an adjustment mechanism may be provided between the optical pickup main body to which the lens actuator is fixed and the fixed portion of the lens actuator.

1 is a perspective view showing a lens actuator of an optical pickup according to a first embodiment of the present invention. FIG. 2 is a perspective view of the lens actuator with the cover of FIG. 1 removed. Similarly, it is a perspective view of a lens actuator with a cover removed. Similarly, it is a top view of the lens actuator with the cover removed. It is AA sectional drawing (however, with a cover) of FIG. It is a disassembled perspective view of the lens actuator of FIG. FIG. 5 is a cross-sectional view taken along line BB in FIG. 4 (with a cover). It is a perspective view of the objective lens shown in FIG. Similarly, it is an exploded perspective view of an objective lens and a holder part. It is a perspective view of the principal part which shows the modification of the objective lens in 1st Embodiment. It is a perspective view of the objective lens in the lens actuator of the optical pickup which concerns on 2nd Embodiment of this invention. It is a perspective view of the movable part of the lens actuator in 2nd Embodiment. It is the figure which looked at the cross section in the plane C of FIG. 12 from the D direction. It is principal part explanatory drawing of the holder fixing | fixed part of the objective lens in 2nd Embodiment. It is explanatory drawing of the adjustment mechanism of the objective lens in 2nd Embodiment. It is a figure which shows the modification of the objective lens fixing | fixed part of the holder in 2nd Embodiment. It is a perspective view of the lens actuator of the optical pick-up which concerns on 3rd Embodiment of this invention. It is a perspective view of the objective lens in the lens actuator of the optical pick-up which concerns on 4th Embodiment of this invention. It is a perspective view which shows the modification of the fixing | fixed part of the objective lens which concerns on this invention. It is a perspective view of the objective lens shown in FIG. 19, and the holder part holding it. It is a perspective view which shows the other modification of the fixing | fixed part of the objective lens which concerns on this invention. Similarly, it is a perspective view which shows another modification. It is a figure which shows the objective lens which consists of a conventional free-form surface lens. It is a figure which shows the other conventional optical element which has a free-form surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Focus coil 4a-4h Tracking coil 6a-6f Wire spring 7 Spring hook 8a, 8b Concave part 9 Convex part 10 Objective lens 11-16 Optical path 17 Incident surface 18, 19, 20 Reflective surface 21 Ejection surface 22, 23 Side surface 24a, 24b Convex part (fixed part)
25 axes (first axis)
29 Recording medium 30 Holder 31a, 31b Projection 32a-32f Projection 33a, 33b Projection 34a-34f Hole 35a, 35b Groove 36a, 36b Bottom 37 Diaphragm 40 Cover 41 Substrate 42 Hole 43a-43f Hole 44 Base 45a, 45b Rising 46a-46d Bending part 47a, 47b Magnet 61a, 61b Convex part (fixed part)
62a, 62b Groove 63a, 63b Bottom 64a, 64b Wall 71 Cylindrical protrusion 72 Hole 73 Axis (fourth axis)
81 Convex part (fixed part)
81a, 81b Convex part (fixed part)
82 axis (first axis)
82a, 82b ８３ 83a, 83b Groove part 84a, 84b Groove part 91a, 91b Convex part (fixed part)
92a, 92b Space part 96a, 96b Convex part (fixed part)
97a surface 99 rotational symmetry axis (first axis)

Claims (11)

A plurality of optical action surfaces including at least an entrance surface and an exit surface are used, which are fixed to a holder, and at least one of these optical action surfaces is a rotationally asymmetric curved surface, and the light incident from the entrance surface is emitted In the optical element for optical pickup that is emitted from the surface and condensed on the recording medium,
An optical element for an optical pickup, wherein the fixing portion fixed to the holder has a rotationally symmetric shape with respect to the first axis.   The optical element for an optical pickup according to claim 1, wherein the rotationally symmetric shape is a cylindrical shape.   The optical element for an optical pickup according to claim 1, wherein the rotationally symmetric shape is a truncated cone shape.   2. The optical element for an optical pickup according to claim 1, wherein the rotationally symmetric shape is a shape formed by rotating a plane 180 degrees or more and less than 360 degrees around the first axis.   2. The angle formed by the direction cosine of the first axis and the second axis is 90 degrees when the optical axis of light emitted from the optical element is a second axis. The optical element for optical pickups as described in any one of -4.   The optical element for an optical pickup according to claim 1, wherein the first axis intersects with an optical axis of light emitted from the exit surface or an extension line of the optical axis. .   The optical element for an optical pickup according to claim 1, wherein the optical action surface has at least one reflecting surface in addition to the incident surface and the exit surface.   8. The optical element for an optical pickup according to claim 7, wherein the reflecting surface is a rotationally asymmetric curved surface. In an optical pickup comprising at least an optical element for condensing incident light on a recording medium, a holder for fixing the optical element, and a moving mechanism for the holder,
An optical pickup, wherein the optical element comprises the optical element for an optical pickup according to any one of claims 1 to 8.   The optical pickup according to claim 9, wherein the moving mechanism rotates the holder about a third axis whose direction cosine is 90 degrees with respect to the first axis. An optical element for condensing incident light on a recording medium, a holder for fixing the optical element, a first member for movably supporting the holder, and a second member for fixing the first member In an optical pickup comprising at least
The optical element comprises the optical element for an optical pickup according to any one of claims 1 to 8,
The optical pickup according to claim 1, wherein the first member is fixed to the second member so as to be adjustable in rotation about a fourth axis having a cosine of 90 degrees with the first axis.

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