JP2006209907A - Optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup capable of preventing a nonuniform temperature distribution in an objective lens and aberrations in the objective lens, caused by nonuniform temperature distribution. <P>SOLUTION: This optical pickup is provided with an objective lens 1, a lens holder 3 for supporting the objective lens 1, and coils 2a and 2b installed in the lens holder 3 for driving the objective lens 1 and the lens holder 3. The objective lens 1 is installed at a plurality of support parts 6a to 6d of the lens holder 3 to be supported, and contact areas with the objective lens 1 are smaller for the support parts 6a to 6d arranged near the coils 2a and 2b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup used in an optical recording / reproducing apparatus.

  An optical pickup is used to read information recorded on an optical disk, which is a recording medium such as a CD or DVD, or to record information on an optical disk. In an optical pickup, an electromagnetic actuator composed of a coil and a magnet is generally used to control the relative position between an objective lens that emits laser light and an optical disk.

  This optical pickup includes an objective lens mainly made of plastic, a lens holder for holding the objective lens, and a wire for elastically supporting the lens holder. The lens holder is provided with a focus coil for driving the lens holder in the focus direction and a tracking coil for driving the lens holder in the tracking direction. Moreover, there are four wires, for example, and the lens holder is cantilevered.

  In recent years, since the optical pickup tends to be further miniaturized and integrated, the objective lens is disposed close to a coil such as a focus coil and a tracking coil that are heat sources. In addition, since the recording / reproducing speed is increased and the driving current supplied to the coil tends to increase, the amount of heat generated by the coil increases and the temperature of the objective lens increases. In the objective lens, a temperature distribution is generated in which the temperature near the coil is higher than the temperature far from the coil, and the temperature difference is remarkable. As a result, the objective lens made of plastic with a high coefficient of thermal expansion easily causes a change in thickness and axially asymmetric thermal deformation, resulting in increased coma, spherical aberration, astigmatism, and the like. Yes.

Therefore, in order to solve this problem, a configuration has been proposed in which a member with high thermal conductivity formed in an annular shape with a constant thickness is disposed so as to contact the objective lens and the lens holder (for example, , See Patent Document 1). By adopting such a configuration, heat is uniformly transmitted to the objective lens, and nonuniformity of the temperature distribution in the objective lens is reduced, so that various aberrations due to the nonuniformity of the temperature distribution are reduced.
Japanese Patent Laid-Open No. 11-176209

  However, even with the optical pickup configured as described above, the temperature rise on the side closer to the objective lens coil is slightly higher than the temperature rise on the side far from the objective lens coil, so the temperature distribution in the objective lens is uneven. It is.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical pickup that prevents the temperature distribution in the objective lens from becoming non-uniform and prevents the objective lens from causing aberrations due to the non-uniform temperature distribution. To do.

  The first optical pickup of the present invention includes an objective lens, a lens holder that supports the objective lens, and a coil installed in the lens holder to drive the objective lens and the lens holder, and the lens The objective lens is installed on a plurality of support portions of the holder so that the objective lens is supported, and the support portion disposed closer to the coil is in contact with the objective lens. Is small.

  In addition, the second optical pickup of the present invention includes an objective lens, a lens holder that supports the objective lens, a coil installed in the lens holder to drive the objective lens and the lens holder, and the objective An annular member having a higher thermal conductivity than the lens holder is provided around the lens so as to surround the objective lens, and a space is provided between the lens holder or the objective lens and the annular member. The distance of the space formed along the radial direction of the objective lens as viewed from the focus direction is larger as the position is closer to the coil.

  The third optical pickup of the present invention includes an objective lens, a lens holder that supports the objective lens, a coil installed in the lens holder to drive the objective lens and the lens holder, and the objective An annular member having a thermal conductivity higher than that of the lens holder, which is disposed around the lens so as to surround the objective lens, and an outer peripheral surface of the annular member is in contact with the lens holder; The inner peripheral surface is in contact with the outer peripheral surface of the objective lens, and the width of the annular member along the radial direction of the objective lens as viewed from the focus direction is smaller as the position is closer to the coil.

  The optical pickup according to the present invention has an effect that the temperature distribution in the objective lens is prevented from becoming non-uniform, and the aberration of the objective lens due to the non-uniform temperature distribution hardly occurs.

  In the first optical pickup device of the present invention, the support portion has a smaller contact area with the objective lens as it is arranged closer to the coil that is the heat source. As a result, the larger the temperature rise of the support portion due to the heat generation of the coil, the smaller the contact area with the objective lens, so that heat is evenly transmitted to the objective lens. Therefore, the temperature distribution of the objective lens is uniform, and various aberrations such as coma aberration, spherical aberration, and astigmatism caused by the non-uniform temperature distribution of the objective lens hardly occur.

  In the first optical pickup of the present invention, preferably, the objective lens and the support portion are fixed by an adhesive member, and the support portion disposed closer to the coil is applied to the adhesive member. The amount is small. Thereby, the heat transmitted to the objective lens through the adhesive member is also uniformly transmitted to the objective lens.

  In addition, the second optical pickup of the present invention includes an annular member that is installed around the objective lens so as to surround the objective lens and has a higher thermal conductivity than the lens holder, and the lens holder or the objective lens, and the annular member There is a space between the two and the distance of the space along the radial direction of the objective lens as viewed from the focus direction is larger as the position is closer to the coil. As a result, the larger the temperature rise, the larger the space is formed by the heat generated by the coil, so that heat is evenly transmitted to the objective lens. In addition, since the annular member has higher thermal conductivity than the lens holder, heat is also diffused in the annular member so that heat is transmitted in a state that is nearly equal. Therefore, the temperature distribution of the objective lens is uniform, and various aberrations such as coma aberration, spherical aberration, and astigmatism caused by the non-uniform temperature distribution of the objective lens hardly occur.

  In the second optical pickup of the present invention, preferably, the coil is installed on the surface of the lens holder parallel to a plane extending in the tracking direction and the focus direction, and the annular member shortens the tracking direction. An elliptical ring whose major axis is a direction perpendicular to the axis, the tracking direction, and the focus direction, and the space is formed between the annular member and the objective lens. Thereby, heat is uniformly transmitted to the objective lens.

  The third optical pickup according to the present invention further includes an annular member having higher thermal conductivity than the lens holder, in contact with the lens holder on the outer peripheral surface, and in contact with the outer peripheral surface of the objective lens on the inner peripheral surface. The width of the annular member along the radial direction of the objective lens as viewed from the side is smaller as the position is closer to the coil. As a result, the smaller the temperature rise due to the heat generated by the coil, the larger the width of the annular member, so that the heat is evenly transmitted to the objective lens. In addition, since the annular member has higher thermal conductivity than the lens holder, heat is also diffused in the annular member so that heat is transmitted in a state that is nearly equal. Therefore, the temperature distribution of the objective lens is uniform, and various aberrations such as coma aberration, spherical aberration, and astigmatism caused by the non-uniform temperature distribution of the objective lens hardly occur.

  In the second optical pickup of the present invention, the coil is installed on the surface of the lens holder parallel to a plane extending in the tracking direction and the focus direction, and the outer periphery of the annular member has a long axis in the tracking direction. An ellipse having a minor axis in a direction perpendicular to the tracking direction and the focus direction. Thereby, heat is uniformly transmitted to the objective lens.

  In the second or third optical pickup, preferably, the annular member is a metal film having a surface perpendicular to the focus direction. Thereby, an annular member can be easily produced by plating or vapor deposition. Further, since the annular member is a film, the weight is not large, and the increase in current used for driving the objective lens is small, so that the amount of heat generated by the coil does not increase.

  In the second or third optical pickup, the metal film may be formed on the lens holder.

  In any one of the first to third optical pickups, the objective lens is made of plastic. Thereby, cost reduction is possible. In addition, since the lens is plastic, the weight of the lens is light, the movable part of the optical pickup can be reduced, and low power consumption and excellent servo response can be obtained. Further, it is possible to mass-produce a lens including a diffraction grating that can improve aberration characteristics and cope with a plurality of wavelengths.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
An optical pickup according to Embodiment 1 of the present invention will be described with reference to the drawings. 1 is a plan view showing the configuration of an optical pickup according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 and 2, the focus direction of the objective lens 1 is the Z-axis direction, and the tracking direction of the objective lens 1 is the Y-axis direction. The X axis is an axis perpendicular to the Y axis and the Z axis.

  The optical pickup 10 will be described with reference to FIGS. 1 and 2. The optical pickup 10 includes a base 9, a suspension holder 8, two magnets 4 a and 4 b that are plate-like and form a drive magnetic circuit, an objective lens 1 made of plastic such as PMMA, and the objective lens 1. A lens holder 3 supporting the lens holder, coil substrates (coils) 2a and 2b installed on the lens holder 3, suspension wires 5a, 5b and 5c elastically supporting the lens holder 3, and a suspension wire (not shown). I have. The suspension wire not shown in FIG. 1 has the same length as the suspension wire 5c in FIG. 1, is located in the −Z-axis direction of the suspension wire 5c, and is installed substantially parallel to the suspension wire 5c. Further, the suspension wire (not shown) is located in the −Y-axis direction of the suspension wire 5b in FIG. 2 and is installed substantially parallel to the suspension wire 5b. Therefore, it cannot be illustrated in FIG. 1 and FIG.

  The suspension holder 8 and the magnets 4 a and 4 b are fixedly installed on the base 9. The magnets 4a and 4b are arranged so as to face each other and to be perpendicular to the X axis, and the lens holder 3 is located between them. Suspension wires 5a, 5b, and 5c and one end of a suspension wire (not shown) are fixed to the lens holder 3. The suspension wires 5a, 5b, and 5c and the other end of the suspension wire (not shown) are attached to the suspension holder 8. It is fixed. That is, the lens holder 3 is cantilevered by the suspension wires 5a, 5b, 5c and a suspension wire (not shown). Since the suspension wires 5a, 5b, 5c and the suspension wire (not shown) are elastic bodies, the lens holder 3 is not fixed and cannot be moved. The suspension wires 5a, 5b, and 5c and the suspension wire (not shown) also have a conductive wire function, and supply current to the coil substrates 2a and 2b.

  The lens holder 3 is manufactured by injection molding using, for example, a liquid crystal polymer resin. Coil substrates 2a and 2b are formed on the surface of the lens holder 3 facing the magnets 4a and 4b, respectively. The coil boards 2a and 2b are formed by integrally laminating a coil wiring pattern forming a tracking coil and a focus coil on a printed board, and are supplied from suspension wires 5a, 5b and 5c and a suspension wire (not shown). The current direction controls the magnetic direction and the strength of the magnetic force. By controlling the magnetic direction and magnetic force of the coil substrates 2a and 2b, a force having a desired direction and a desired strength is generated between the coil substrates 2a and 2b and the magnets 4a and 4b. As described above, the magnets 4a and 4b are fixed to the base 9, and the lens holder 3 is elastically supported by the suspension wires 5a, 5b and 5c and a suspension wire (not shown). 3 is driven. Since the objective lens 1 is supported by the lens holder 3, when the lens holder 3 is driven, the objective lens is also driven. In this way, the objective lens 1 is driven in the focus direction (Z-axis direction) and the tracking direction (Y-axis direction), and the laser beam can be focused at a desired position on an optical disk (not shown) as a recording medium. it can. Thereby, it is possible to read information recorded on the optical disc or record information on the optical disc.

  The lens holder 3 is provided with four support portions 6a, 6b, 6c and 6d for supporting the objective lens 1. The objective lens 1 is installed on the support portions 6a, 6b, 6c, and 6d. The objective lens 1 has a structure that does not contact the lens holder 3 at portions other than the support portions 6a, 6b, 6c, and 6d. The relationship between the support portions 6a, 6b, 6c, 6d and the objective lens 1 will be described with reference to FIGS. 1 and 2 and FIG. FIG. 3 is an enlarged plan view of the objective lens in the optical pickup according to Embodiment 1 of the present invention. Specifically, only the periphery of the objective lens 1 in FIG. 1 is enlarged and illustrated.

  When the optical pickup is viewed from the focus direction (Z-axis direction) (especially, see FIG. 3), the support portions 6b and 6d pass along a line 12 that passes through the center of the circular objective lens 1 and is parallel to the Y-axis. Is arranged. Further, support portions 6a and 6c are arranged along a line 13 passing through the center of the objective lens 1 and parallel to the X axis. Here, the distances between the support portions 6a, 6b, 6c, 6d and the coil substrates 2a, 2b are compared. The distances between the support portions 6a, 6b, 6c, 6d and the coil substrates 2a, 2b are the shortest distances between the support portions 6a, 6b, 6c, 6d and the coil substrates 2a, 2b. The support portions 6a and 6c are the same distance from the coil substrates 2a and 2b, respectively, and the support portions 6b and 6d are the same distance from the coil substrates 2a and 2b, respectively. Further, the distance between the support portions 6a and 6c and the coil substrates 2a and 2b is shorter than the distance between the support portions 6b and 6d and the coil substrates 2a and 2b. That is, the support portions 6a and 6c are closer to the coil substrates 2a and 2b than the support portions 6b and 6d. The support portions 6a and 6c closer to the coil substrates 2a and 2b have a smaller contact area with the objective lens 1 than the support portions 6b and 6d.

  When the optical pickup 10 is activated, the objective lens 1 is driven in order to irradiate the optical disk with laser light. As described above, the objective lens 1 is driven by controlling the magnetic direction and the strength of the magnetic force of the coil substrates 2a and 2b. Thereby, current is supplied to the coil substrates 2a and 2b from the suspension wires 5a, 5b and 5c and the suspension wire (not shown), and the coil substrates 2a and 2b generate heat. In the lens holder 3, heat is transferred from the surface in contact with the coil substrates 2 a and 2 b to locations that are sequentially separated. That is, the temperature rise is larger at a position closer to the coil substrates 2a and 2b, which are heat sources, and the temperature rise is smaller at a position farther from the coil substrates 2a and 2b.

  Heat generated in the coil substrates 2 a and 2 b is also transmitted to the objective lens 1 through the lens holder 3. Since the objective lens 1 is not in contact with the lens holder 3 except for the support portions 6a, 6b, 6c, and 6d, the heat conduction path is only the support portions 6a, 6b, 6c, and 6d. That is, heat is transmitted to the objective lens 1 through the support portions 6a, 6b, 6c, and 6d.

  Since the support portions 6a and 6c are closer to the coil substrates 2a and 2b than the support portions 6b and 6d, the temperature rise is higher than that of the support portions 6b and 6d. However, as described above, since the support portions 6a and 6c have a smaller contact area with the objective lens 1 than the support portions 6b and 6d, the support portions 6a and 6c are contact surfaces compared to the support portions 6b and 6d. Since the heat transfer resistance is large, it is difficult to transfer heat, and no large heat is transferred to the objective lens 1. That is, each support part 6a, 6b, 6c, 6d can transmit heat to the objective lens 1 equally. By doing in this way, the temperature distribution of the objective lens 1 can be made uniform. Therefore, various aberrations such as coma aberration, spherical aberration, and astigmatism that are caused when the temperature distribution of the objective lens 1 is not uniform are unlikely to occur.

  Further, in order to fix the objective lens 1 to the support portions 6a, 6b, 6c and 6d, UV curable adhesives 7a and 7b which are adhesive members applied to the objective lens 1 and the support portions 6a, 6b, 6c and 6d. 7c and 7d, it is preferable to set the coating amount. Since heat is transmitted also by the UV curable adhesives 7a, 7b, 7c, 7d, specifically, the UV curable adhesive applied to the support portions 6a, 6c installed at positions close to the coil substrates 2a, 2b. The amount of 7a, 7c is preferably smaller than the amount of UV curable adhesives 7b, 7d applied to the support portions 6b, 6d. By doing in this way, the temperature distribution of the objective lens 1 can be made uniform.

  Note that heat transfer from the coil substrates 2a and 2b, which are heat generation sources, to the objective lens 1 may be due to radiation, convection of outside air, or the like in addition to heat conduction through the lens holder 3 or the like. Also in the amount of heat transfer to the objective lens 1 due to radiation or convection, the heat transfer amount closer to the coil substrates 2a and 2b, which are heat sources, becomes larger. Therefore, it is preferable that the support portions 6a and 6c closer to the coil substrates 2a and 2b have a smaller contact area with the objective lens 1 than the support portions 6b and 6d. Further, the amount of the UV curable adhesive 7a, 7c applied to the support portions 6a, 6c installed at positions close to the coil substrates 2a, 2b is used as the UV curable adhesive 7b applied to the support portions 6b, 6d, It is preferable to make it less than the amount of 7d. Thereby, the heat transfer amount by heat conduction is adjusted by the amount of non-uniform heat transfer amount by radiation or convection, and the temperature distribution of the objective lens 1 can be made uniform.

  The contact area between the support portions 6a, 6b, 6c, and 6d and the objective lens 1 and the arrangement thereof are optimum so that the temperature distribution of the objective lens 1 is uniform in consideration of the heat generation amount of the coil, the conductivity of each component, and the like. The value of Similarly, the application amount of the UV curable adhesives 7a, 7b, 7c, and 7d may be set to an optimum value.

  Regardless of the size of the contact area between the support portions 6a, 6b, 6c and 6d and the objective lens 1, the heat transmitted to the objective lens 1 can be controlled by controlling the application amount of the adhesives 7a, 7b, 7c and 7d. It is also possible to make the temperature distribution of the objective lens 1 uniform by controlling.

  As described above, in the optical pickup 10 according to the first embodiment, it is not necessary to increase the number of components in order to make the temperature distribution of the objective lens uniform, so that the component cost does not increase. Further, since the number of assembling steps does not increase, the manufacturing cost does not increase. In addition, since there are no additional parts, the weight of the driven portion does not increase, and there is no need to increase the current for driving the objective lens. Therefore, the amount of heat generated by the coil substrates 2a and 2b does not increase.

  Note that the structure specifically shown in Embodiment 1 is merely an example, and the present invention is not limited to this specific example. For example, the number of support parts is not limited to four as long as it is plural. The number of support portions may be an odd number, but an even number can be arranged symmetrically, and a configuration for making the temperature distribution uniform can be easily formed.

(Embodiment 2)
An optical pickup according to Embodiment 2 of the present invention will be described with reference to the drawings. 4 is a plan view showing the configuration of the optical pickup according to Embodiment 2 of the present invention, and FIG. 5 is a cross-sectional view taken along the line V-V in FIG. The basic configuration of the optical pickup 20 of the second embodiment is substantially the same as that of the optical pickup 10 of the first embodiment shown in FIGS. 1 and 2, and the support portions 6a and 6b shown in FIGS. 6c and 6d are not provided, and an annular member 21 in which a space 24 is formed between the objective lens 1 and the objective lens 1 is provided. Therefore, in FIGS. 4 and 5, members having the same functions as those in the first embodiment are denoted by the same reference numerals, and description of these members is omitted. 4 and 5, the focus direction of the objective lens 1 is the Z-axis direction, and the tracking direction of the objective lens 1 is the Y-axis direction. The X axis is an axis perpendicular to the Y axis and the Z axis.

  As shown in FIGS. 4 and 5, the objective lens 1 is supported on the lens holder 3. An annular member 21 is provided around the objective lens 1 so as to surround the objective lens 1. The thermal conductivity of the annular member 21 is higher than that of the lens holder 3, and the annular member 21 is, for example, a metal. When the optical pickup is viewed from the focus direction (especially, see FIG. 4), the objective lens 1 has a circular shape, and the annular member 21 has a circular objective lens 1 with the X axis as the major axis and the Y axis as the minor axis. An elliptical ring having the same center. The objective lens 1 and the annular member 21 are in contact with each other on a line 22 that passes through the center of the objective lens 1 that is a circle and is parallel to the Y axis. In other locations, the objective lens 1 and the annular member 21 are not in contact with each other, and a space 24 is formed.

  Further, the distance between the objective lens 1 and the annular member 21, that is, the distance of the space 24 is maximum on a line 23 that passes through the center of the objective lens 1 that is a circle and is parallel to the X axis. The distance between the objective lens 1 and the annular member 21 (hereinafter referred to as the distance of the space 24) is the distance between the outer periphery of the objective lens 1 and the inner periphery of the annular member 21 along the radial direction of the objective lens 1. is there. Further, the distance of the space 24 increases as it approaches the line 23 along the outer periphery of the objective lens 1 from the contact point between the line 22 and the objective lens 1, that is, the point 25 where the objective lens 1 and the annular member 21 are in contact. As described above, the maximum is on line 23. That is, the distance of the space 24 increases as it approaches the point 26 at the intersection of the line 23 and the outer periphery of the objective lens 1 and decreases as it approaches the point 25 at the intersection of the line 22 and the outer periphery of the objective lens 1.

  Here, the distances between the outer peripheral portions of the objective lens 1 and the coil substrates 2a and 2b are compared. The distances between the outer peripheral portions of the objective lens 1 and the coil substrates 2a and 2b are the shortest distances between the outer peripheral portions of the objective lens 1 and the coil substrates 2a and 2b. The distance between the point 26 that intersects the line 23 on the outer periphery of the objective lens 1 and the coil substrate 2a, 2b is the shortest, and the point 25 that intersects the line 22 on the outer periphery of the objective lens 1 and the coil substrate 2a, 2b. And the longest distance.

  When the optical pickup 20 is activated and the coil substrates 2 a and 2 b generate heat, the heat is transmitted to the annular member 21 through the lens holder 3. For example, in the case of the lens holder 3 made of a liquid crystal polymer that is often used because of its light weight and high rigidity, the thermal conductivity is 0.289 W / m ° C., which is not so high. Further, since the distances between the coil substrates 2 a and 2 b and the outer peripheral portions of the annular member 21 are not constant, heat is transmitted non-uniformly to the outer periphery of the annular member 21. That is, at each location on the outer periphery of the annular member 21, the temperature is lower as the location is farther from the coil substrates 2a and 2b. Specifically, the temperature at the point 28, which is the intersection point between the line 22 and the outer periphery of the annular member 21, is lower than that at the point 27, which is the intersection point between the line 23 and the outer periphery of the annular member 21. However, when, for example, a C1720 beryllium copper plate is used as the annular member 21, its thermal conductivity is 109 to 130 W / m ° C., which is nearly 1000 times higher than that of the lens holder 3. As a result, heat is diffused in the annular member 21, and the uneven temperature distribution is easily corrected. Therefore, although the temperature distribution in the inner periphery of the annular member 21 is not uniform, the temperature distribution in the outer periphery of the annular member 21 is nearly equal to that in the outer periphery.

  That is, the temperature is higher as it is closer to the point of intersection of the line 23 and the inner periphery of the annular member 21, and the temperature is lower as it is closer to the point of intersection of the line 22 and the inner periphery of the annular member 21. The distribution is almost even.

  Furthermore, as described above, a space 24 having a size corresponding to the distance between the coil substrates 2 a and 2 b and the objective lens 1 is formed between the objective lens 1 and the annular member 21. Since the space 24 is filled with air, the thermal conductivity is lower than that of the annular member 21.

  As described above, the temperature distribution at the inner periphery of the annular member 21 increases as the temperature approaches the point at the intersection of the line 23 and the inner periphery of the annular member 21, and at the intersection of the line 22 and the inner periphery of the annular member 21. The closer to a spot, the lower the temperature. Further, as described above, the distance of the space 24 increases as it approaches the point 26 at the intersection of the line 23 and the outer periphery of the objective lens 1 and approaches the point 25 at the intersection of the line 22 and the outer periphery of the objective lens 1. Get smaller. For this reason, in the inner periphery of the annular member 21, the higher the temperature, the farther the distance to the outer periphery of the objective lens 1, and the greater the heat transfer resistance, the less it is possible to transfer heat. On the contrary, in the inner periphery of the annular member 21, the lower the temperature, the closer the distance to the outer periphery of the objective lens 1, and the easier the heat transfer because the resistance of heat transfer is small. Therefore, even if the temperature distribution is not uniform on the inner periphery of the annular member 21, the space 24 is formed so that heat can be evenly transmitted to the outer periphery of the objective lens 1. Thus, the optical pickup 20 of the second embodiment can make the temperature distribution of the objective lens 1 uniform.

  Note that heat transfer from the coil substrates 2a and 2b, which are heat generation sources, to the objective lens 1 may be due to radiation, convection of outside air, or the like, in addition to heat conduction through the annular member 21 and the space 24. Also in the amount of heat transfer to the objective lens 1 due to radiation or convection, the heat transfer amount closer to the coil substrates 2a and 2b, which are heat sources, becomes larger. Therefore, it is preferable that the distance of the space 24 is larger as the distance from the intersection point between the line 23 and the outer periphery of the objective lens 1 is closer. Further, it is preferable that the distance of the space 24 is smaller as the distance from the intersection point between the line 22 and the outer periphery of the objective lens 1 approaches the point 25. Thereby, the heat transfer amount by heat conduction is adjusted by the amount of non-uniform heat transfer amount by radiation or convection, and the temperature distribution of the objective lens 1 can be made uniform.

  The distance of the space 24 may be set to an optimum value that makes the temperature distribution of the objective lens 1 uniform in consideration of the heat generation amount of the coil substrates 2a and 2b, the conductivity of each component, and the like.

  As described above, the heat from the coil substrates 2a and 2b is evenly transmitted to the objective lens 1 of the optical pickup 20 of the second embodiment. Therefore, the temperature distribution of the objective lens 1 is uniform, and various aberrations such as coma aberration, spherical aberration, and astigmatism caused by the non-uniform temperature distribution of the objective lens 1 are unlikely to occur.

  For example, the annular member 21 may be formed of a metal film having a thickness in the focus direction. Specifically, the annular member 21 that is a metal film may be formed on the lens holder 3 by forming a metal film by plating or vapor deposition. By doing in this way, the annular member 21 can be produced easily. Further, since the annular member 21 is a film, the weight is not large and the increase in current used for driving the objective lens 1 is small, so that the amount of heat generated by the coil substrates 2a and 2b does not increase.

  In the second embodiment, the space 24 is formed between the annular member 21 and the objective lens 1. For example, another configuration of the optical pickup according to the second embodiment of the present invention is shown. As shown in FIG. 6, which is a plan view, when viewed from the focus direction, the annular member 21 and the lens holder 3 are circular in shape, and a space 24 is formed between the annular member 21 and the lens holder. It is good. The distance of the space 24 may be increased as the position is closer to the coil substrates 2a and 2b as in the above configuration, and the specific value is determined in consideration of the heat generation amount of the coil substrates 2a and 2b, the conductivity of each component, and the like. What is necessary is just to obtain | require the optimal value from which the temperature distribution of the objective lens 1 becomes uniform. In FIG. 6, the same reference numerals are used for members having the same functions as those in FIG.

  Note that the structure specifically shown in Embodiment 2 is merely an example, and the present invention is not limited to this specific example. For example, the annular member has an elliptical shape, but may have another shape as long as heat is evenly transmitted to the objective lens, for example, a rectangular shape.

(Embodiment 3)
An optical pickup according to Embodiment 3 of the present invention will be described with reference to the drawings. 7 is a plan view showing the configuration of the optical pickup according to Embodiment 3 of the present invention, and FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. The basic configuration of the optical pickup 30 of the third embodiment is substantially the same as that of the optical pickup 10 of the first embodiment shown in FIGS. 1 and 2, and the support portions 6a and 6b shown in FIGS. 6c and 6d are not provided, but the point that the annular member 31 is provided is different. 7 and 8, members having the same functions as those in the first embodiment are denoted by the same reference numerals, and description of these members is omitted. 7 and 8, the focus direction of the objective lens 1 is the Z-axis direction, and the tracking direction of the objective lens 1 is the Y-axis direction. The X axis is an axis perpendicular to the Y axis and the Z axis.

As shown in FIGS. 7 and 8, the objective lens 1 is supported on the lens holder 3. An annular member 31 is provided around the objective lens 1 so as to surround the objective lens 1. The thermal conductivity of the annular member 31 is higher than that of the lens holder 3, and the annular member 31 is, for example, a metal. When the optical pickup is viewed from the focus direction (especially, see FIG. 7), the objective lens 1 is circular, and the outer periphery of the annular member 31 is a circle with the X axis direction as the short axis and the Y axis direction as the long axis. It is an ellipse having the same center as the objective lens 1. The inner periphery of the annular member 31 is a circle having the same shape as the objective lens 1, and the inner peripheral surface of the annular member 31 is in contact with the outer peripheral surface of the objective lens. That is, the objective lens 1 is fitted inside the annular member 31. Since the annular member 31 is configured as described above, the width of the annular member 31 is not uniform. The width of the annular member 31 is the length along the radial direction of the annular member 1. The distance between each part of the annular member 31 and the coil substrates 2a and 2b is the shortest distance between each part of the annular member 31 and the coil substrates 2a and 2b. For example, the width t ₃₂ of the annular member 31 along the line 32 that passes through the center of the objective lens 1 that is a circle and is parallel to the Y axis is a line 33 that passes through the center of the objective lens 1 that is a circle and is parallel to the X axis. It is larger than the width t ₃₃ of the annular member 31 along. In the annular member 31, the width of the annular member 31 increases as it approaches the line 32, and the width of the annular member 31 decreases as it approaches the line 33. Therefore, the minimum value of the width t _33, the width t ₃₂ is the maximum value. The outer peripheral surface of the annular member 31 is in contact with the lens holder 3.

  When the optical pickup 30 is activated and the coil substrates 2 a and 2 b generate heat, the heat is transmitted to the annular member 31 through the lens holder 3. For example, in the case of the lens holder 3 made of a liquid crystal polymer that is often used because of its light weight and high rigidity, the thermal conductivity is 0.289 W / m ° C., which is not so high. Further, since the distances between the coil substrates 2 a and 2 b and the outer peripheral portions of the annular member 31 are not constant, heat is transmitted nonuniformly to the outer periphery of the annular member 31. That is, at each location on the outer periphery of the annular member 31, the temperature is lower as the location is farther from the coil substrates 2a and 2b. Specifically, the temperature at the point 38, which is the intersection point between the line 32 and the outer periphery of the annular member 31, is lower than that at the point 37 that is the intersection point between the line 33 and the outer periphery of the annular member 31. However, when, for example, a C1720 beryllium copper plate is used as the annular member 31, its thermal conductivity is 109 to 130 W / m ° C., which is nearly 1000 times higher than that of the lens holder 3. As a result, heat is diffused in the annular member 31, and uneven temperature distribution is easily corrected. Furthermore, the width of the annular member 31 having a higher thermal conductivity is larger in a portion where the width of the annular member 31 is different depending on the distance from the coil substrates 2a and 2b and the temperature rise on the outer periphery of the annular member 31 is smaller. Therefore, the amount of heat transferred increases. Therefore, the temperature distribution on the inner periphery of the annular member 31 becomes uniform. Since the outer peripheral surface of the objective lens 1 is in contact with the inner peripheral surface of the annular member 31, the temperature distribution on the outer periphery of the objective lens 1 becomes uniform. Therefore, the non-uniformity of heat transmitted to the objective lens 1 is corrected, and the temperature distribution of the objective lens becomes uniform.

  The width of each portion of the annular member 31 may be set to an optimum value that makes the temperature distribution of the objective lens uniform in consideration of the heat generation amount of the coil substrates 2a and 2b, the conductivity of each component, and the like.

  As described above, the heat from the coil substrates 2a and 2b is evenly transmitted to the objective lens 1 of the optical pickup 30 of the third embodiment. Therefore, the temperature distribution of the objective lens 1 is uniform, and various aberrations of the objective lens due to the non-uniform temperature distribution of the objective lens 1 do not occur.

  For example, the annular member 31 may be formed of a metal film having a surface perpendicular to the focus direction. Specifically, the annular member 31 that is a metal film may be formed by forming a metal film on the lens holder 3 by plating or vapor deposition. By doing in this way, the annular member 31 can be produced easily. Further, since the annular member 31 is a film, the weight is not large and the increase in current used for driving the objective lens 1 is small, so that the amount of heat generated by the coil substrates 2a and 2b does not increase.

  Note that the structure specifically shown in Embodiment 3 is merely an example, and the present invention is not limited to this specific example. For example, the outer shape of the annular member is elliptical, but may be other shapes as long as heat is evenly transmitted to the objective lens, for example, a rectangle.

  In the first to third embodiments, the objective lens 1 is formed of plastic such as PMMA. However, the objective lens 1 may be formed of glass or other plastics, for example.

  The objective lens is mainly formed in an aspherical surface, and is mostly composed of two types of glass and plastic. When the objective lens is made of plastic, there are disadvantages such as deformation due to thermal expansion due to a change in temperature and temperature in comparison with glass. However, in general, the cost can be reduced by injection molding, the specific gravity is lighter than glass, and the movable part of the optical pickup can be reduced, resulting in low power consumption and excellent servo response. There is a merit such as. Furthermore, a plastic objective lens can be provided with a diffraction grating that cannot be mass-produced by glass. Providing the diffraction grating has advantages such as improvement of the aberration characteristics of the lens and the ability to cope with a plurality of wavelengths. For these reasons, plastic lenses are now the mainstream.

  Thus, by using the objective lens 1 as plastic, there are effects of cost reduction, power consumption reduction, excellent servo response, and aberration characteristics.

  As described above, plastic is a material having a high coefficient of thermal expansion. However, in the optical pickup of the present invention, since the objective lens 1 has a uniform temperature distribution, there is an effect that various aberrations do not occur even if the objective lens 1 is made of plastic.

  In the optical pickup of the present invention, the temperature distribution of the objective lens is uniform even when the coil generates heat. Therefore, the optical pickup can be downsized, thinned, and driven at high speed, and the performance improvement and reliability of the optical pickup are guaranteed. Yes. Accordingly, it is desirable that the optical pickup of the present invention be mounted on an optical recording / reproducing apparatus that is required to be downsized, thinned, and driven at high speed.

FIG. 2 is a plan view showing the configuration of the optical pickup according to the first embodiment of the present invention. II-II sectional view of FIG. In the optical pickup according to Embodiment 1 of the present invention, an enlarged plan view of the objective lens FIG. 3 is a plan view showing the configuration of the optical pickup according to the second embodiment of the present invention. VV arrow cross-sectional view of FIG. FIG. 5 is a plan view showing the configuration of another optical pickup according to the second embodiment of the present invention. FIG. 5 is a plan view showing a configuration of an optical pickup according to a third embodiment of the present invention. VIII-VIII sectional view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Objective lens 2a, 2b Coil board | substrate 3 Lens holder 4a, 4b Magnet 5a, 5b, 5c Suspension wire 6a, 6b, 6c, 6d Support part 7a, 7b, 7c, 7d UV curable adhesive 8 Suspension holder 9 Base 10 , 20, 30 Optical pickup 12, 13, 22, 23, 32, 33 Line 21, 31 Annular member 24 Space 25, 26, 27, 28, 37, 38 locations

Claims (9)

An objective lens;
A lens holder for supporting the objective lens;
A coil installed on the lens holder to drive the objective lens and the lens holder;
The objective lens is supported by installing the objective lens on a plurality of support portions that the lens holder has,
The optical pickup having a smaller contact area with the objective lens as the support portion is arranged closer to the coil. The objective lens and the support portion are fixed by an adhesive member,
The optical pickup according to claim 1, wherein the amount of application of the adhesive member is smaller as the support portion is disposed closer to the coil. An objective lens;
A lens holder for supporting the objective lens;
A coil installed in the lens holder for driving the objective lens and the lens holder;
An annular member that is installed around the objective lens so as to surround the objective lens and has a higher thermal conductivity than the lens holder,
A space is formed between the lens holder or the objective lens and the annular member,
An optical pickup in which the distance of the space along the radial direction of the objective lens as viewed from the focus direction is larger at a position closer to the coil. The coil is installed on the surface of the lens holder parallel to a plane extending in the tracking direction and the focus direction,
The annular member is an elliptical ring having a short axis as a tracking direction and a long axis as a direction perpendicular to the tracking direction and the focus direction,
The optical pickup according to claim 3, wherein the space is formed between the annular member and the objective lens. An objective lens;
A lens holder for supporting the objective lens;
A coil installed in the lens holder for driving the objective lens and the lens holder;
An annular member that is installed around the objective lens so as to surround the objective lens and has a higher thermal conductivity than the lens holder,
The outer peripheral surface of the annular member is in contact with the lens holder,
The inner peripheral surface of the annular member is in contact with the outer peripheral surface of the objective lens,
The optical pickup is such that the width of the annular member along the radial direction of the objective lens viewed from the focus direction is smaller as the position is closer to the coil. The coil is installed on the surface of the lens holder parallel to a plane extending in the tracking direction and the focus direction,
6. The optical pickup according to claim 5, wherein the outer peripheral surface of the annular member is an ellipse having a major axis as a tracking direction and a minor axis as a direction perpendicular to the tracking direction and the focus direction.   The optical pickup according to claim 3, wherein the annular member is a metal film having a surface perpendicular to the focus direction.   The optical pickup according to claim 7, wherein the metal film is formed on the lens holder.   The optical pickup according to claim 1, wherein the objective lens is made of plastic.

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