JP2007102919A - Optical pickup apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup apparatus capable of suitably recording/reproducing information in/from all of high density DVDs and conventional DVDs and CDs for instance. <P>SOLUTION: Although heat generated from a tracking coil TC and a focusing coil FC which are heat sources is transmitted to a lens holder HD, heat conduction is suppressed by a holding body HB having high heat insulation, so that heating on an optical surface of an objective lens OBJ1 on the side close to the tracking coil TC and the focusing coil FC is suppressed and temperature distribution on the optical surface and the inside of an element can be uniformed. Since the objective lens OBJ1 is held by the holding body HB having high heat insulation, a sudden temperature change can be suppressed and resistance force against disturbance can be improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical pickup device, and in particular, collects light beams emitted from light sources having different light source wavelengths via one of two objective optical elements, thereby differentiating information on different optical information recording media. The present invention relates to an optical pickup device capable of recording and / or reproducing.

  In recent years, research and development of a high-density optical disk system capable of recording / reproducing information using a blue-violet semiconductor laser having a wavelength of about 400 nm is rapidly progressing. As an example, an optical disc (for example, HD DVD) for recording / reproducing information with a numerical aperture NA of 0.65 and a light source wavelength of 405 nm is the same size as a DVD (NA 0.6, light source wavelength of 650 nm, storage capacity of 4 and 7 GB). It is possible to record information of 15 to 20 GB per surface on an optical disk having a diameter of 12 cm. An optical disc (for example, a Blu-ray disc) that records and reproduces information with a numerical aperture NA of 0.85 and a light source wavelength of 405 nm can record 20 to 30 GB of information on one surface of an optical disc having a diameter of 12 cm. is there. In this specification, an optical disk that records and / or reproduces information using a blue-violet semiconductor laser having a wavelength of about 400 nm is generically referred to as a “high density DVD”.

  By the way, it cannot be said that the value as a product of the optical pickup device is sufficient only by being able to appropriately record / reproduce information on such a high-density DVD. In light of the fact that DVDs and CDs that record a wide variety of information are currently being sold, it is not only possible to record / reproduce information appropriately for high-density DVDs. For example, conventional DVDs owned by users Alternatively, it is possible to record / reproduce information appropriately for a CD as well, which leads to an increase in the value of a product as a compatible type optical pickup device. Against this background, the condensing optical system used in the compatible type optical pickup device can appropriately record / reproduce information while maintaining compatibility with any high-density DVD, conventional type DVD, or CD. It is desired to have performance.

Here, in order to simplify the configuration of the optical pickup device and to reduce the cost, it is essential that the compatible optical pickup device has a single condensing optical system including the objective lens. preferable. However, due to the shortening of the light source wavelength, the adoption of high NA, etc., the aberration characteristics of the objective lens are required to be extremely high when recording and / or reproducing information on a high-density DVD. In some cases, it is difficult to appropriately record and / or reproduce information on DVDs and CDs. On the other hand, an example of an optical pickup device capable of recording and / or reproducing information on three or more types of optical information recording media by switching a plurality of objective lenses is described in, for example, Patent Document 1 below. ing.
JP 2004-319062 A

  By the way, in order to appropriately record and / or reproduce information in the optical pickup device, the light beam that has passed through the objective optical element is appropriately condensed on the track of the information recording surface of the optical information recording medium (optical disk). Therefore, a focusing operation and a tracking operation for adjusting the position of the objective optical element are necessary. Here, for example, in a general optical pickup device of a DVD / CD compatible type, it is sufficient to perform a focusing operation and a tracking operation for a commonly used objective optical element, and the actuator can be a small type.

  However, as shown in Patent Document 1, when two objective optical elements are used, it is necessary to perform a focusing operation and a tracking operation for each. However, if an actuator is provided separately and each is driven independently, As a result, the number of actuators increases, resulting in a complicated configuration and a larger apparatus. Furthermore, when one objective optical element is used, the other objective optical element is not used, and there is a situation that it is not necessary to drive the objective optical element independently.

  Therefore, a configuration has been planned in which two objective optical elements are held by a common support member and driven by a common actuator. However, in a configuration in which two objective optical elements are driven together with a common support member, a greater driving force is required for the actuator in order to perform a focusing operation and a tracking operation with good response to an increase in inertial mass. The Rukoto. To obtain a large driving force, the amount of energization increases, so the amount of heat generation increases, and the problem that the generated heat is transmitted through the support member and heats the objective optical element has been clarified.

  In particular, when two objective optical elements are supported by a common support member, it is difficult to dispose the heat source at an equal distance from any objective optical element. It will be heated in the form of distribution. However, coma aberration occurs when the temperature distribution in the optical surface of the objective optical element or inside the element is rotationally asymmetric with respect to the optical axis. On the other hand, even if the temperature distribution in the optical surface of the objective optical element or inside the element is rotationally symmetric with respect to the optical axis, spherical aberration occurs if there is a temperature gradient from the outside of the element toward the optical axis. As described above, when the temperature distribution in the optical axis vertical direction and / or the optical axis direction is generated in the objective optical element and the temperature difference is excessive, the optical surface is thermally expanded and the refractive index is changed. There is a risk of causing aberration deterioration that hinders reproduction. In particular, in recent years, there has been a demand for increasing the speed of recording and / or reproducing information on an optical information recording medium, and in order to meet this demand, it is necessary to appropriately suppress aberration deterioration of the light beam that has passed through the objective optical element. There is.

  The present invention has been made in view of such problems, and provides an optical pickup device that can appropriately record and / or reproduce information on different optical information recording media using two objective optical elements. For the purpose.

The optical pickup device according to claim 1 includes a first light source having a wavelength λ1, a second light source having a wavelength λ2, and a condensing optical system including a first objective optical element and a second objective optical element. Information can be recorded and / or reproduced by focusing the light beam from the first light source on the information recording surface of the first optical information recording medium through a protective layer having a thickness t1. An optical pickup device capable of recording and / or reproducing information by condensing the luminous flux from the light onto the information recording surface of the second optical information recording medium through a protective layer having a thickness t2.
The first objective optical element and the second objective optical element are supported by a support member driven by an actuator,
A first member is disposed on the actuator side between at least one of the first objective optical element and the second objective optical element and the actuator, and is more thermally insulated than the first member. The high second member is arranged on the at least one side.

  When the first objective optical element and the second objective optical element are heated by a heat source such as an actuator, an optical surface of the objective optical element is attached by attaching a member having another characteristic to the support member. In addition, it is possible to suppress an uneven temperature distribution inside the device or to reduce the maximum temperature. More specifically, a first member is arranged on the actuator side between at least one of the first objective optical element and the second objective optical element and the actuator, and the first member By disposing the second member having a higher heat insulating property than the member on the at least one side, the heat insulating effect of the at least one objective optical element is enhanced, and the temperature distribution in the optical surface and the inside of the element is made closer to uniform. In addition, the maximum temperature can be suppressed, whereby aberration deterioration in the light beam passing through the objective optical element can be suppressed, and information can be appropriately recorded and / or reproduced on the optical information recording medium. The second member is preferably disposed so as to be in contact with at least one of the first objective optical element and the second objective optical element, but another inclusion may be disposed therebetween. good.

  The optical pickup device according to a second aspect of the present invention is the optical pickup device according to the first aspect, wherein the support member is formed integrally with the first member, so that the number of parts is reduced. .

  The optical pickup device according to claim 3 is characterized in that, in the invention according to claim 1 or 2, the support member is made of metal, so that it has excellent heat resistance and also enhances a heat dissipation effect. be able to.

  According to a fourth aspect of the present invention, in the invention according to the third aspect, the support member is an aluminum alloy or a magnesium alloy, so that the weight can be reduced. In addition, when an alumite film treatment is performed on the surface of the aluminum alloy, the heat dissipation effect can be enhanced.

  The optical pickup device according to claim 5 is characterized in that, in the invention according to claim 1 or 2, the support member is formed of a first resin material, and therefore takes advantage of the characteristics of the resin. Weight reduction can be achieved.

  An optical pickup device according to a sixth aspect is characterized in that, in the invention according to the fifth aspect, the first resin material includes a fibrous substance, and therefore, the strength and heat resistance can be improved. In particular, when carbon fiber or metal fiber is used as the fibrous material, the thermal conductivity can be increased.

  According to a seventh aspect of the present invention, in the optical pickup device according to the fifth aspect, the support member is made of a liquid crystal polymer, so that the heat resistance can be improved. As the liquid crystal polymer, a wholly aromatic polyester is preferably used, and it is desirable to contain glass fibers in order to improve the strength. Details of the liquid crystal polymer are described in, for example, JP-A No. 2000-345028 and JP-A No. 10-46007.

  An optical pickup device according to an eighth aspect is characterized in that, in the invention according to any one of the first to seventh aspects, the liquid crystal polymer is a wholly aromatic polyester.

  According to a ninth aspect of the present invention, in the invention according to the fifth aspect, the support member is a composite of glass fiber and liquid crystal polymer.

  An optical pickup device according to a tenth aspect of the present invention is the invention according to any one of the first to ninth aspects, wherein the support member has a radiating fin on the outer periphery or in the vicinity thereof, so that the heat dissipation effect is enhanced. The maximum temperature of the objective optical element can be reduced.

  An optical pickup device according to an eleventh aspect is the invention according to any one of the first to tenth aspects, wherein a magnetic field forming unit that forms a magnetic field around the support member and a magnetic fluid that contacts the periphery of the support member. Therefore, the heat dissipation effect can be enhanced through the magnetic fluid. Details of the magnetic fluid are described in, for example, JP-A-2004-227679.

  An optical pickup device according to a twelfth aspect is characterized in that, in the invention according to any one of the first to eleventh aspects, the second member is formed of a second resin material. It is possible to reduce the weight by utilizing the characteristics of

  The optical pickup device according to a thirteenth aspect of the invention according to the twelfth aspect of the invention is characterized in that the second resin material is a resin foam, and thus has an excellent heat insulating effect.

  The optical pickup device according to a fourteenth aspect is characterized in that, in the invention according to the twelfth aspect, the second member is a sheet material, so that the compactness can be achieved.

  An optical pickup device according to a fifteenth aspect is characterized in that, in the invention according to any one of the first to fourteenth aspects, the second member is annular, and is fitted around the objective optical element. Can be combined. Here, the “annular” includes not only a shape that is continuous in the circumferential direction but also a shape that is partially interrupted, such as a so-called C-shape.

  An optical pickup device according to a sixteenth aspect is the invention according to any one of the first to fifteenth aspects, wherein the second member is disposed between the first objective optical element and the second objective optical element. In other words, it is characterized in that a portion having a higher thermal conductivity is provided, so that the temperature distribution on the optical surface and inside the element can be made uniform.

  In an optical pickup device according to a seventeenth aspect, in the invention according to any one of the first to sixteenth aspects, the wavelength λ1 is not less than 380 nm and not more than 450 nm, and the second member is formed of the first objective optical element. It is arranged only around.

  An optical pickup device according to claim 18 is the invention according to any one of claims 1 to 17, wherein the maximum numerical aperture of the first objective optical element is greater than the maximum numerical aperture of the second objective optical element. The second member is arranged only around the first objective optical element.

  The optical pickup device according to claim 19 is the optical pickup device according to any one of claims 1 to 18, wherein the light beam from the first light source that has passed through the first objective optical element or the second objective optical element. Information is recorded by condensing the light beam from the second light source that has passed through the third optical information recording medium through a protective layer having a thickness of t3 (t3> t1 or t3> t2). And / or reproducing, information can be appropriately recorded and / or reproduced on a high-density DVD, DVD, or CD.

  An optical pickup device according to a twentieth aspect is the optical pickup device according to the nineteenth aspect, wherein the first optical information recording medium is an HD DVD, the second optical information recording medium is a DVD, and the third optical information is recorded. The recording medium is a CD.

  In an optical pickup device according to a twenty-first aspect, in the invention according to the nineteenth aspect, the first optical information recording medium is a Blu-ray disc, the second optical information recording medium is a DVD, and the third optical information is recorded. The recording medium is a CD.

  An optical pickup device according to a twenty-second aspect is the invention according to any one of the first to twenty-first aspects, wherein the first objective optical element has two or more optical elements, and the second objective optical element. Since the optical information recording medium is required to have a relatively high optical performance, information recording and / or using the first objective optical element. For optical information recording media that are reproduced and whose optical performance requirements are relatively lenient, information can be recorded and / or reproduced using the second objective optical element to balance performance and cost. it can.

  According to a twenty-third aspect of the present invention, there is provided the optical pickup device according to the twenty-second aspect of the invention, wherein the first objective optical element uses the light beam condensed on one information recording surface of a Blu-ray disc, DVD, or CD. The information is recorded and / or reproduced by a light beam condensed on the information recording surface of the HD DVD by the second objective optical element.

  An optical pickup device according to a twenty-fourth aspect is the optical pickup device according to the twenty-second aspect, wherein information is obtained by a light beam condensed on one information recording surface of HD DVD, DVD, and CD by the first objective optical element. The information is recorded and / or reproduced by a light beam condensed on the information recording surface of the Blu-ray disc by the second objective optical element.

  The optical pickup device according to claim 25 is the invention according to any one of claims 1 to 17, wherein the second member is disposed around the first objective optical element and the second objective optical element. It is characterized by being arranged respectively.

  An optical pickup device according to a twenty-sixth aspect is the invention according to any one of the first to seventeenth aspects, wherein the second member includes both the first objective optical element and the second objective optical element. It is arranged so as to surround it.

An optical pickup device according to a twenty-seventh aspect includes a first light source having a wavelength λ1, a second light source having a wavelength λ2, and a condensing optical system including a first objective optical element and a second objective optical element. Information can be recorded and / or reproduced by focusing the light beam from the first light source on the information recording surface of the first optical information recording medium through a protective layer having a thickness t1. An optical pickup device capable of recording and / or reproducing information by condensing the luminous flux from the light onto the information recording surface of the second optical information recording medium through a protective layer having a thickness t2.
The first objective optical element and the second objective optical element are supported by a support member driven by an actuator,
A third member having higher thermal conductivity than the support member is disposed between the support member and the actuator.

  According to the present invention, since the third member having higher thermal conductivity than the support member is disposed between the support member and the actuator, when the actuator is a heat source, the third member is generated therefrom. Dispersing the heat through the third member can suppress local heating and maximum temperature of the optical surface of at least one objective optical element, and thereby aberration in a light beam passing through the objective optical element. It is possible to appropriately record and / or reproduce information on the optical information recording medium while suppressing deterioration.

The optical pickup device according to claim 28 includes a first light source having a wavelength λ1, a second light source having a wavelength λ2, and a condensing optical system including a first objective optical element and a second objective optical element. Information can be recorded and / or reproduced by focusing the light beam from the first light source on the information recording surface of the first optical information recording medium through a protective layer having a thickness t1. An optical pickup device capable of recording and / or reproducing information by condensing the luminous flux from the light onto the information recording surface of the second optical information recording medium through a protective layer having a thickness t2.
The first objective optical element and the second objective optical element are supported by a support member driven by an actuator,
A fourth member having higher heat dissipation than the support member is disposed between the support member and the actuator.

  According to the present invention, since the fourth member having higher heat dissipation than the support member is disposed between the support member and the actuator, when the actuator serves as a heat source, the heat generated therefrom By radiating heat through the fourth member, it is possible to suppress the optical surface of at least one objective optical element and the maximum temperature inside the element, thereby suppressing aberration deterioration in the light beam passing through the objective optical element. Thus, information can be recorded and / or reproduced appropriately on the optical information recording medium.

  The optical pickup device according to a twenty-ninth aspect is the invention according to the twenty-eighth aspect, wherein fins or gaps are formed in the fourth member, so that the heat dissipation effect can be further enhanced.

  An optical pickup device according to a thirty-third aspect is characterized in that, in the invention according to any one of the twenty-seventh to twenty-ninth aspects, the support member is formed of a resin material, and therefore takes advantage of the characteristics of the resin. Weight reduction can be achieved.

  The optical pickup device according to a thirty-first aspect is characterized in that, in the invention according to the thirty-third aspect, the resin material contains a fibrous substance, so that the strength and heat resistance can be improved. In particular, when carbon fiber or the like is used as the fibrous material, the thermal conductivity can be increased.

  In the optical pickup device according to a thirty-second aspect, in the invention according to the thirty-first aspect, the support member is made of a liquid crystal polymer, so that the heat resistance can be improved.

  An optical pickup device according to a thirty-third aspect is the invention according to any one of the twenty-seventh to thirty-second aspects, wherein a magnetic field forming unit that forms a magnetic field around the support member and a magnetic fluid that contacts the periphery of the support member. Therefore, the heat dissipation effect can be enhanced through the magnetic fluid.

  An optical pickup device according to a thirty-fourth aspect is the invention according to any one of the first to thirty-third aspects, wherein at least one of the first objective optical element and the second objective optical element has a particle size of 30 nm. It is formed from an organic-inorganic composite in which the following inorganic fine particles are dispersed.

  The inorganic fine particles dispersed in the thermoplastic resin, for example, as the organic-inorganic composite are not particularly limited, and the refractive index change rate (hereinafter referred to as | dn / dT |) of the obtained thermoplastic resin composition with temperature is not particularly limited. It can be arbitrarily selected from inorganic fine particles that can achieve the object of the present invention. Specifically, oxide fine particles, metal salt fine particles, semiconductor fine particles, and the like are preferably used. Of these, those that do not generate absorption, light emission, fluorescence, etc. in the wavelength region used as an optical element are appropriately selected and used. Is preferred.

As the oxide fine particles used in the present invention, the metal constituting the metal oxide is Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Y, Nb, Zr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, La, Ta, Hf, W, Ir, Tl, Pb, Bi and rare earth metals A metal oxide that is one or more metals selected from the group can be used. Specifically, for example, silicon oxide, titanium oxide, zinc oxide, aluminum oxide, zirconium oxide, hafnium oxide, niobium oxide Tantalum oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, indium oxide, tin oxide, lead oxide, niobic acid which is a double oxide composed of these oxides Lithium, potassium niobate, lithium tantalate, the aluminum magnesium oxide (MgAl ₂ O _4), and the like. In addition, rare earth oxides can also be used as oxide fine particles used in the present invention, specifically, scandium oxide, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide. Terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide and the like. Examples of the metal salt fine particles include carbonates, phosphates, sulfates, and the like, specifically, calcium carbonate, aluminum phosphate, and the like.

Further, the semiconductor fine particles in the present invention mean fine particles having a semiconductor crystal composition, and specific examples of the semiconductor crystal composition include simple elements of Group 14 elements of the periodic table such as carbon, silicon, germanium, and tin, Compound consisting of a group 15 element of the periodic table such as phosphorus (black phosphorus), a group 16 element of the periodic table such as selenium and tellurium, a compound comprising a plurality of group 14 elements of the periodic table such as silicon carbide (SiC), oxidation Tin (IV) (SnO ₂ ), tin sulfide (II, IV) (Sn (II) Sn (IV) S ₃ ), tin sulfide (IV) (SnS ₂ ), tin sulfide (II) (SnS), selenization Periodic table of tin (II) (SnSe), tin telluride (II) (SnTe), lead sulfide (II) (PbS), lead selenide (II) (PbSe), lead telluride (II) (PbTe), etc. Compound of group 14 element and group 16 element of periodic table, boron nitride (BN), boron phosphide BP), boron arsenide (BAs), aluminum nitride (AlN), aluminum phosphide (AlP), aluminum arsenide (AlAs), aluminum antimonide (AlSb), gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide Periodic Table Group 13 elements and Periodic Table Group 15 such as (GaAs), gallium antimonide (GaSb), indium nitride (InN), indium phosphide (InP), indium arsenide (InAs), indium antimonide (InSb) Compound with element (or III-V group compound semiconductor), aluminum sulfide (Al ₂ S ₃ ), aluminum selenide (Al ₂ Se ₃ ), gallium sulfide (Ga ₂ S ₃ ), gallium selenide (Ga ₂ Se ₃₎ ), telluride gallium (Ga ₂ Te _3), indium oxide (In ₂ O _3), Indium (In ₂ S _3), indium selenide (In ₂ Se _3), compounds of tellurium indium (In ₂ Te ₃₎ periodic table group 13 elements and the periodic table group 16 element such as, thallium chloride ( I) (TlCl), thallium bromide (I) (TlBr), thallium iodide (I) (TlI) and other group 13 elements and periodic table group 17 elements, zinc oxide (ZnO), Zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), cadmium oxide (CdO), cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), mercury sulfide (HgS) ), Mercury selenide (HgSe), mercury telluride (HgTe), etc., a compound of a periodic table group 12 element and a periodic table group 16 element (or II-VI group compound semiconductor), sulfur Arsenic _{(III) (As 2 S 3} ), selenium arsenic _{(III) (As 2 Se 3} ), telluride arsenic _{(III) (As 2 Te 3} ), antimony sulfide _{(III) (Sb 2 S 3} ), selenium Antimony (III) iodide (Sb ₂ Se ₃ ), antimony telluride (III) (Sb ₂ Te ₃ ), bismuth sulfide (III) (Bi ₂ S ₃ ), bismuth selenide (III) (Bi ₂ Se ₃ ), Compounds of Group 15 elements of Periodic Table and Group 16 elements of Periodic Table such as bismuth (III) telluride (Bi ₂ Te ₃ ), copper oxide (I) (Cu ₂ O), copper selenide (Cu) ₂ Se) and other compounds of Group 11 elements of the periodic table and Group 16 elements of the periodic table, copper chloride (I) (CuCl), copper bromide (I) (CuBr), copper iodide (I) (CuI) , Compounds of Group 11 elements of the periodic table and Group 17 elements of the periodic table, such as silver chloride (AgCl) and silver bromide (AgBr), acids Periodic table such as nickel (II) (NiO), periodic group 10 elements and periodic table group 16 elements, cobalt oxide (II) (CoO), cobalt sulfide (II) (CoS), etc. Compounds of group elements and group 16 elements of the periodic table, compounds of group 8 elements of the periodic table and group 16 elements of the periodic table such as triiron tetroxide (Fe ₃ O ₄ ), iron (II) sulfide (FeS), etc. , Manganese (II) (MnO) and other periodic table group 7 elements and periodic table group 16 elements, molybdenum sulfide (IV) (MoS ₂ ), tungsten oxide (IV) (WO ₂ ) periodicity Periodic table of compounds of Group 6 elements and Periodic Table Group 16 elements, vanadium oxide (II) (VO), vanadium oxide (IV) (VO ₂ ), tantalum oxide (V) (Ta ₂ O ₅ ), etc. Compounds of Group 5 elements and Group 16 elements of the periodic table, titanium oxide (TiO ₂ , Ti ₂ O ₅ , Ti ₂ O ₃ , Ti ₅ O ₉ etc.) periodic table group 4 element and periodic table group 16 element compound, magnesium sulfide (MgS), periodic table group 2 element such as magnesium selenide (MgSe) Compounds with Group 16 elements of the periodic table, cadmium oxide (II) chromium (III) (CdCr ₂ O ₄ ), cadmium selenide (II) chromium (III) (CdCr ₂ Se ₄ ), copper (II) chromium sulfide ( III) (CuCr ₂ S ₄ ), chalcogen spinels such as mercury (II) selenide (III) (HgCr ₂ Se ₄ ), barium titanate (BaTiO ₃ ), and the like. In addition, G. Schmid et al .; Adv. Mater. 4, 494 (1991) (BN) 75 (BF2) 15F15 and D.C. Fenske et al .; Angew. Chem. Int. Ed. Engl. 29, page 1452 (1990), a semiconductor cluster having a fixed structure such as Cu ₁₄₆ Se ₇₃ (triethylphosphine) ₂₂ reported in the same manner is also exemplified.

Generally, dn / dT of a thermoplastic resin has a negative value, that is, the refractive index decreases as the temperature increases. Therefore, in order to efficiently reduce | dn / dT | of the thermoplastic resin composition, it is preferable to disperse fine particles having a large dn / dT. When using fine particles having the same sign as dn / dT of the thermoplastic resin, the absolute value of dn / dT of the fine particles is preferably smaller than dn / dT of the thermoplastic resin as the base material. Furthermore, fine particles having a dn / dT opposite in sign to dn / dT of the thermoplastic resin as a base material, that is, fine particles having a positive value of dn / dT are preferably used. By dispersing such fine particles in the thermoplastic resin, | dn / dT | of the thermoplastic resin composition can be effectively reduced with a small amount. The dn / dT of the fine particles to be dispersed can be appropriately selected depending on the value of the dn / dT of the thermoplastic resin as the base material. In general, the fine particles are dispersed in a thermoplastic resin preferably used for an optical element. The dn / dT of the fine particles is preferably larger than −20 × 10 ^{−6 and} more preferably larger than −10 × 10 ⁻⁶ . As fine particles having a large dn / dT, for example, gallium nitride, zinc sulfide, zinc oxide, lithium niobate, lithium tantalate, or the like is preferably used.

  On the other hand, when the fine particles are dispersed in the thermoplastic resin, it is desirable that the difference in refractive index between the thermoplastic resin as the base material and the fine particles is small. As a result of investigations by the inventors, it has been found that if the difference in refractive index between the thermoplastic resin and the dispersed fine particles is small, it is difficult to cause scattering when light is transmitted. When the fine particles are dispersed in the thermoplastic resin, the larger the particles, the easier it is to cause scattering when light is transmitted. However, if the difference in the refractive index between the thermoplastic resin and the dispersed fine particles is small, relatively large fine particles It was discovered that the degree of light scattering is small even when using. The difference in refractive index between the thermoplastic resin and the dispersed fine particles is preferably in the range of 0 to 0.3, and more preferably in the range of 0 to 0.15.

  The refractive index of a thermoplastic resin preferably used as an optical material is often about 1.4 to 1.6, and examples of the material dispersed in these thermoplastic resins include silica (silicon oxide), calcium carbonate, Aluminum phosphate, aluminum oxide, magnesium oxide, aluminum / magnesium oxide and the like are preferably used.

  Further, the inventors' research has revealed that the dn / dT of the thermoplastic resin composition can be effectively reduced by dispersing fine particles having a relatively low refractive index. Although the details of the reason why | dn / dT | of the thermoplastic resin composition in which fine particles having a low refractive index are dispersed are small, the temperature change in the volume fraction of the inorganic fine particles in the resin composition causes the refraction of the fine particles. It is thought that the lower the rate, the more likely it is to work in the direction of decreasing | dn / dT | of the resin composition. As fine particles having a relatively low refractive index, for example, silica (silicon oxide), calcium carbonate, and aluminum phosphate are preferably used.

  It is difficult to improve the dn / dT reduction effect, light transmittance, desired refractive index, etc. of the thermoplastic resin composition at the same time, and the fine particles dispersed in the thermoplastic resin are characteristics required for the thermoplastic resin composition. The dn / dT of the fine particles themselves, the difference between the dn / dT of the fine particles and the dn / dT of the thermoplastic resin as the base material, the refractive index of the fine particles, and the like may be selected as appropriate. it can. In addition, it is preferable to appropriately select and use fine particles which are compatible with the thermoplastic resin as a base material, that is, dispersibility with respect to the thermoplastic resin and hardly cause scattering, and are used.

  For example, when a cyclic olefin polymer that is preferably used for an optical element is used as a base material, silica is preferably used as fine particles that reduce | dn / dT | while maintaining light transmittance.

  As the fine particles, one kind of inorganic fine particles may be used, or a plurality of kinds of inorganic fine particles may be used in combination. By using a plurality of types of fine particles having different properties, the required characteristics can be improved more efficiently.

  The inorganic fine particles according to the present invention preferably have an average particle size of 1 nm or more and 30 nm or less, more preferably 1 nm or more and 20 nm or less, and still more preferably 1 nm or more and 10 nm or less. When the average particle diameter is less than 1 nm, it is difficult to disperse the inorganic fine particles and the desired performance may not be obtained. Therefore, the average particle diameter is preferably 1 nm or more, and the average particle diameter exceeds 30 nm. In addition, the resulting thermoplastic material composition may become turbid, resulting in a decrease in transparency and a light transmittance of less than 70%. Therefore, the average particle diameter is preferably 30 nm or less. The average particle diameter here refers to the volume average value of the diameter (sphere converted particle diameter) when each particle is converted into a sphere having the same volume.

  Further, the shape of the inorganic fine particles is not particularly limited, but spherical fine particles are preferably used. Specifically, the minimum diameter of the particle (minimum value of the distance between the tangents when drawing two tangents in contact with the outer periphery of the fine particle) / maximum diameter (the value in drawing two tangents in contact with the outer periphery of the fine particle The maximum value of the distance between tangents) is preferably 0.5 to 1.0, and more preferably 0.7 to 1.0.

  Further, the particle size distribution is not particularly limited, but in order to achieve the effect of the present invention more efficiently, a particle having a relatively narrow distribution is preferably used rather than a particle having a wide distribution. Used.

  An optical pickup device according to a thirty-fifth aspect is the invention according to any one of the first to third aspects, wherein at least one of the first objective optical element and the second objective optical element is made of glass. Therefore, an objective optical element that suppresses a change in aberration even when a temperature distribution occurs can be obtained.

  In this specification, an objective optical element (also referred to as an objective lens) is to be opposed to the optical information recording medium at a position closest to the optical information recording medium in a state where the optical information recording medium is loaded in the optical pickup device in a narrow sense. It refers to an optical element that has a light collecting action, and in a broad sense, refers to an optical element that can be actuated at least in the optical axis direction by an actuator together with the optical element.

  ADVANTAGE OF THE INVENTION According to this invention, the optical pick-up apparatus which can record and / or reproduce | regenerate information appropriately with respect to a different optical information recording medium can be provided using two objective optical elements.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 shows the recording / recording of information on all high-density DVDs (also referred to as first optical disks), conventional DVDs (also referred to as second optical disks) and CDs (also referred to as third optical disks). It is a schematic sectional drawing of the optical pick-up apparatus concerning 1st Embodiment which can reproduce | regenerate. Note that the maximum numerical aperture of the first objective lens OBJ1 is larger than the maximum numerical aperture of the second objective lens OBJ2 (the same applies to the embodiment of FIG. 2 described later).

  As shown in FIG. 1, the lens holder HD, which is a support member, is supported at least two-dimensionally by an actuator ACT. The actuator ACT is attached to the frame (not shown) of the optical pickup device via the actuator base ACTB so that the position can be adjusted. The actuator base ACTB is held so as to be movable in the left-right direction in the figure by an actuator (not shown).

  A case where information is recorded and / or reproduced on the first optical disc OD1 will be described. In such a case, it is assumed that the actuator base ACTB is moved by an actuator (not shown) so that the optical axis of the first objective lens OBJ1 coincides with the optical axis of the λ / 4 wavelength plate QWP. In FIG. 1, a light beam emitted from a first semiconductor laser LD1 (wavelength λ1 = 380 nm to 450 nm) serving as a first light source passes through a beam shaper BS and the shape of the light beam is corrected, and then a first collimator. The light enters the lens CL1 and becomes a parallel light beam. The light beam emitted from the first collimating lens CL1 passes through the first dichroic prism DP1, and is diffracted as an optical means for separating the light beam emitted from the light source into a main beam for recording / reproducing and a sub beam for detecting a tracking error signal. It passes through the grating G, and further passes through the polarization beam splitter PBS, the expander lens EXP, and the second dichroic prism DP2.

  The light beam that has passed through the second dichroic prism DP2 passes through the λ / 4 wavelength plate QWP, is condensed by the first objective lens OBJ1, and is a protective layer (thickness t1 = 0.1) of the first optical disk OD1. Through 0.7 mm) to be focused on the information recording surface to form a focused spot.

  Then, the light beam modulated and reflected by the information pits on the information recording surface again passes through the first objective lens OBJ1, the λ / 4 wavelength plate QWP1, the second dichroic prism DP2, and the expander lens EXP, and then by the polarization beam splitter PBS. Since it is reflected and further passes through the sensor lens SL and enters the light receiving surface of the photodetector PD, a read signal of information recorded on the first optical disk OD1 is obtained using the output signal.

  In addition, focus detection and track detection are performed by detecting a change in the amount of light due to a change in the shape and position of the spot on the photodetector PD. Based on this detection, the actuator ACT is moved so that the first objective lens OBJ1 is moved together with the lens holder HD so that the light beam from the first semiconductor laser LD1 is imaged on the information recording surface of the first optical disk OD1. To drive.

  A case where information is recorded and / or reproduced on the second optical disc OD2 will be described. In this case, it is assumed that the actuator base ACTB is moved by an actuator (not shown) so that the optical axis of the second objective lens OBJ2 coincides with the optical axis of the λ / 4 wavelength plate QWP. The light beam emitted from the second semiconductor laser LD2 (wavelength λ2 = 600 nm to 700 nm) enters the second collimator lens CL2 and becomes a parallel light beam. The light beam emitted from the second collimating lens CL2 is reflected by the first dichroic prism DP1, passes through the diffraction grating G, and further passes through the polarization beam splitter PBS, the expander lens EXP, and the second dichroic prism DP2.

  The light beam that has passed through the second dichroic prism DP2 passes through the λ / 4 wavelength plate QWP, is condensed by the second objective lens OBJ2, and is a protective layer (thickness t2 = 0.5) of the second optical disk OD2. Through 0.7 mm) to be focused on the information recording surface to form a focused spot.

  The light beam modulated and reflected by the information pits on the information recording surface again passes through the second objective lens OBJ2, the λ / 4 wavelength plate QWP, the second dichroic prism DP2, and the expander lens EXP, and is reflected by the polarization beam splitter PBS. Then, the light passes through the sensor lens SL and enters the light receiving surface of the photodetector PD, so that a read signal of information recorded on the second optical disk OD2 is obtained using the output signal.

  In addition, focus detection and track detection are performed by detecting a change in the amount of light due to a change in the shape and position of the spot on the photodetector PD. Based on this detection, the actuator ACT is moved so that the second objective lens OBJ2 is moved together with the lens holder HD so that the light beam from the second semiconductor laser LD2 is imaged on the information recording surface of the second optical disk OD2. To drive.

  The third semiconductor laser LD3 is a hologram laser, and a laser chip LC as a light source and a photodetector PD3 are packaged. A case where information is recorded and / or reproduced on the third optical disc OD3 will be described. In this case, it is assumed that the actuator base ACTB is moved by an actuator (not shown) so that the optical axis of the second objective lens OBJ2 coincides with the optical axis of the λ / 4 wavelength plate QWP.

  The light beam emitted from the laser chip LC of the third semiconductor laser LD3 (wavelength λ3 = 700 nm to 800 nm) passes through the third collimating lens CL3 to become a parallel light beam, and is then reflected by the second dichroic prism DP2. , Passes through the λ / 4 wavelength plate QWP, is condensed by the second objective lens OBJ2, and the information is recorded through the protective layer (thickness t3 = 1.1 to 1.3 mm) of the third optical disk OD3. The light is focused on the surface and a focused spot is formed here.

  The light beam modulated and reflected by the information pits on the information recording surface again passes through the second objective lens OBJ2 and the λ / 4 wavelength plate QWP, is reflected by the second dichroic prism DP2, and is further reflected by the third collimating lens CL3. Since the light is condensed and incident on the light receiving surface of the photodetector PD3 in the third semiconductor laser LD3, a read signal of information recorded on the third optical disk OD3 is obtained using the output signal.

  Further, focus detection and track detection are performed by detecting a change in the amount of light due to a change in the shape and position of the spot on the third photodetector PD3. Based on this detection, the actuator ACT is moved so that the second objective lens OBJ2 is moved together with the lens holder HD so that the light beam from the third semiconductor laser LD3 is imaged on the information recording surface of the third optical disk OD3. Drive.

  FIG. 2 shows that information can be recorded / reproduced on all high-density DVDs (also referred to as first optical disks), conventional DVDs (also referred to as second optical disks) and CDs (also referred to as third optical disks). It is a schematic sectional drawing of the optical pick-up apparatus concerning 2nd Embodiment.

  As shown in FIG. 2, the lens holder HD as a support member is supported by an actuator ACT so as to be movable at least two-dimensionally. The actuator ACT is attached to the frame (not shown) of the optical pickup device via the actuator base ACTB.

  A case where information is recorded and / or reproduced on the first optical disc OD1 will be described. In FIG. 2, a light beam emitted from a first semiconductor laser LD1 (wavelength λ1 = 380 nm to 450 nm) serving as a first light source passes through a beam shaper BS and the shape of the light beam is corrected, and then a first collimator. The light enters the lens CL1 and becomes a parallel light beam. The light beam emitted from the first collimating lens CL1 passes through the first dichroic prism DP1, and is diffracted as an optical means for separating the light beam emitted from the light source into a main beam for recording / reproducing and a sub beam for detecting a tracking error signal. The light passes through the grating G, further passes through the polarizing beam splitter PBS, the expander lens EXP, the second dichroic prism DP2, and the λ / 4 wavelength plate QWP, and is reflected by the third dichroic prism DP3.

  The light beam reflected by the third dichroic prism DP3 is condensed by the first objective lens OBJ1, and the information is passed through the protective layer (thickness t1 = 0.1 to 0.7 mm) of the first optical disk OD1. The light is condensed on the recording surface to form a condensing spot.

  The light beam modulated and reflected by the information pits on the information recording surface again passes through the first objective lens OBJ1, is reflected by the third dichroic prism DP3, and is a λ / 4 wavelength plate QWP1, second dichroic prism DP2, and expander. Since the light passes through the lens EXP, is reflected by the polarization beam splitter PBS, passes through the sensor lens SL, and enters the light receiving surface of the photodetector PD, information is recorded on the first optical disc OD1 using the output signal. A read signal of the recorded information is obtained.

  In addition, focus detection and track detection are performed by detecting a change in the amount of light due to a change in the shape and position of the spot on the photodetector PD. Based on this detection, the actuator ACT is moved so that the first objective lens OBJ1 is moved together with the lens holder HD so that the light beam from the first semiconductor laser LD1 is imaged on the information recording surface of the first optical disk OD1. To drive.

  A case where information is recorded and / or reproduced on the second optical disc OD2 will be described. The light beam emitted from the second semiconductor laser LD2 (wavelength λ2 = 600 nm to 700 nm) enters the second collimator lens CL2 and becomes a parallel light beam. The light beam emitted from the second collimating lens CL2 is reflected by the first dichroic prism DP1, passes through the diffraction grating G, and is further polarized by the polarization beam splitter PBS, the expander lens EXP, the second dichroic prism DP2, the λ / 4 wavelength plate QWP, The light passes through the third dichroic prism DP3 and is reflected by the mirror M.

  The light beam reflected by the mirror M is collected by the second objective lens OBJ2 and is applied to the information recording surface via the protective layer (thickness t2 = 0.5 to 0.7 mm) of the second optical disk OD2. The light is condensed and a condensing spot is formed here.

  The light beam modulated and reflected by the information pits on the information recording surface again passes through the second objective lens OBJ2, is reflected by the mirror M, and is reflected by the third dichroic prism DP3, λ / 4 wavelength plate QWP, and second dichroic prism. DP2 passes through the expander lens EXP, is reflected by the polarization beam splitter PBS, further passes through the sensor lens SL, and enters the light receiving surface of the photodetector PD, so that the output signal is used to enter the second optical disc OD2. A read signal of the recorded information is obtained.

  In addition, focus detection and track detection are performed by detecting a change in the amount of light due to a change in the shape and position of the spot on the photodetector PD. Based on this detection, the actuator ACT is moved so that the second objective lens OBJ2 is moved together with the lens holder HD so that the light beam from the second semiconductor laser LD2 is imaged on the information recording surface of the second optical disk OD2. To drive.

  The third semiconductor laser LD3 is a hologram laser, and a laser chip LC as a light source and a photodetector PD3 are packaged. A case where information is recorded and / or reproduced on the third optical disc OD3 will be described.

  The light beam emitted from the laser chip LC of the third semiconductor laser LD3 (wavelength λ3 = 700 nm to 800 nm) passes through the third collimator lens CL3 to become a parallel light beam, and is further reflected by the second dichroic prism DP2. The protective layer (thickness t3 = 1.1) of the third optical disk OD3 passes through the λ / 4 wavelength plate QWP and the third dichroic prism DP3, is reflected by the mirror M, is condensed by the second objective lens OBJ2. Through 1.3 mm) to be focused on the information recording surface to form a focused spot.

  The light beam modulated and reflected by the information pits on the information recording surface again passes through the second objective lens OBJ2, is reflected by the mirror M, passes through the third dichroic prism DP3, the λ / 4 wavelength plate QWP, and passes through the second objective lens OBJ2. Since it is reflected by the 2 dichroic prism DP2, and further collected by the third collimating lens CL3, it is incident on the light receiving surface of the photodetector PD3 in the third semiconductor laser LD3, so that the output signal is used to generate the third optical disk OD3. A read signal of information recorded in the information is obtained.

  Further, focus detection and track detection are performed by detecting a change in the amount of light due to a change in the shape and position of the spot on the third photodetector PD3. Based on this detection, the actuator ACT is moved so that the second objective lens OBJ2 is moved together with the lens holder HD so that the light beam from the third semiconductor laser LD3 is imaged on the information recording surface of the third optical disk OD3. Drive.

  In the above embodiment, information is recorded and / or reproduced on a Blu-ray disc or HD DVD using the first objective lens OBJ1, and on the DVD and CD using the second objective lens OBJ2. Information is recorded and / or reproduced, but information is recorded and / or reproduced on a Blu-ray disc, DVD and CD using the first objective lens OBJ1, and the second objective lens OBJ2 is installed. It may be used to record and / or reproduce information on the HD DVD. In this case, the light beam having the wavelength λ1 is incident on both the first objective lens OBJ1 and the second objective lens OBJ2.

  FIG. 3 is an exploded perspective view of an objective lens unit OU that can be used in the above-described embodiment. The objective lens unit OU is formed on the outer periphery of the objective lens OBJ1 and objective lens OBJ2, a lens holder (also referred to as a support member) HD that holds the objective lenses OBJ1 and OBJ2, and is a component of the focusing actuator. And a tracking coil TC that is disposed at both ends in the longitudinal direction of the lens holder HD and is a component of the tracking actuator. The lens holder HD is supported by a wire (not shown) so as to be capable of minute displacement with respect to the head main body side, and the tracking coil TC is arranged at an appropriate position facing a magnet or a yoke (not shown). Yes. The objective lens unit OU supplies the lens holder HD together with the objective lenses OBJ1 and OBJ2 in the Z direction parallel to the optical axis by energizing the coils FC and TC disposed in the magnetic field formed by the magnet or the like. A coil drive circuit (not shown) for moving a desired amount in the X direction perpendicular to the X direction is provided.

  The objective lenses OBJ1 and OBJ2 are biconvex lenses made of plastic, and have annular flange portions f1 and f2 on the outer periphery of the circular objective lens bodies b1 and b2. Note that the pair of optical surfaces provided in the objective lens books b1 and b2 can be formed of, for example, an aspheric surface, but are not limited to a simple curved surface. For example, in the case of a compatible optical head capable of reproducing / recording information with respect to a plurality of standards such as CD, DVD, high density optical disk, etc., the optical surfaces of the objective lens bodies b1 and b2 are provided with a diffraction structure or an optical path difference. It can have a structure. Furthermore, these optical surfaces can also be divided into special annular zones.

  A resin lens holder (also referred to as a first member) HD including carbon fiber or glass fiber has a large-diameter opening a1 and a small-diameter opening a2 arranged in the longitudinal direction. In the opening a1, a substantially cylindrical holding body (also referred to as a second member) HB made of foamed resin having higher heat insulation than the material of the lens holder HD is fitted and disposed. The holding body HB has an opening a1 'at the center. The inner diameters of the openings a1 'and a2 are preferably equal to or larger than the outer diameter of the flanges f1 and f2 of the objective lens. In addition, holding portions h1 and h2 projecting annularly inward in the radial direction are formed on the inner periphery of the openings a1 'and a2. The objective lenses OBJ1 and OBJ2 are attached to the holding body HB and the lens holder HD using an adhesive or the like with the flange portions f1 and f2 in contact with the upper surfaces of the holding portions h1 and h2, respectively.

  According to this example, the heat generated from the tracking coil TC and the focusing coil FC as heat sources is transmitted to the lens holder HD, but the heat conduction is suppressed by the holding body HB having high heat insulating properties. Further, heating of the optical surface of the objective lens OBJ1 on the side close to the focusing coil FC is suppressed, and the temperature distribution in the optical surface and inside the element can be made uniform. Moreover, since the rapid temperature change can be suppressed by holding the objective lens OBJ1 with the holding body HB having high heat insulation, resistance to disturbance can be increased.

  FIG. 4 is a perspective view of an objective lens unit OU according to another example. The objective lenses OBJ1 and OBJ2 are incorporated in the lens holder HD. In the example of FIG. 3, only the objective lens OBJ1 having a low tolerance for aberration deterioration is held via the holding body HB as the second member, but in this example, the two objective lenses OBJ1 and OBJ2 are shared. Is held by the holding body HB.

  More specifically, the lens holder HD made of resin forms an elongated hole-shaped opening a3 extending in the longitudinal direction. In the opening a3, a substantially cylindrical holding body HB made of foamed resin having higher heat insulation than the material of the lens holder HD is fitted and disposed. The holding body HB as the second member has openings a1 'and a2' at the center. The inner diameters of the openings a1 'and a2' are preferably equal to or larger than the outer diameter of the flanges f1 and f2 of the objective lens. In addition, the objective lenses OBJ1 and OBJ2 are made of adhesive or the like with the flange portions f1 and f2 in contact with the upper surface of a holding portion (not shown) projecting annularly on the inner periphery of the openings a1 ′ and a2 ′. It is attached to the holding body HB.

  According to this example, the heat generated from the tracking coil TC and the focusing coil FC as heat sources is transmitted to the lens holder HD, but the heat conduction is suppressed by the holding body HB having high heat insulating properties. In addition, heating of the optical surfaces of the objective lenses OBJ1 and OBJ2 near the focusing coil FC is suppressed, and the temperature distribution in the optical surface and inside the element can be made uniform. In addition, since the objective lenses OBJ1 and OBJ2 are held by the holding body HB having a high heat insulating property, a rapid temperature change can be suppressed, so that the resistance to disturbance can be increased.

  FIG. 5 is a perspective view of an objective lens unit OU according to still another example. The objective lenses OBJ1 and OBJ2 are incorporated in the lens holder HD. In the example of FIG. 4, the two objective lenses OBJ1 and OBJ2 are held via a common holding body HB, but in this example, the two objective lenses OBJ1 and OBJ2 are individually held by the holding bodies HB1 and HB2. keeping. The resin lens holder HD is insert-molded with a metal heat transfer member (also referred to as a third member) t1 such as an aluminum alloy having higher heat conductivity than the material.

  More specifically, the resin lens holder HD is formed by arranging the opening a1 and the opening a2 in the longitudinal direction. In the opening a1, a substantially cylindrical holding body HB1 made of a foamed resin having higher heat insulation than the material of the lens holder HD is fitted and disposed. In the opening a2, the material of the lens holder HD is fitted. In addition, a substantially cylindrical holding body HB2 made of a foamed resin having high heat insulation is fitted and disposed. The holding members HB1 and HB2 that are the second members have openings a1 'and a2' at the center, respectively. The inner diameters of the openings a1 'and a2' are preferably equal to or larger than the outer diameter of the flanges f1 and f2 of the objective lens. Further, the objective lenses OBJ1 and OBJ2 use an adhesive or the like in a state where the flange portions f1 and f2 are in contact with the upper surface of a holding portion (not shown) projecting annularly on the inner periphery of the openings a1 ′ and a2 ′. Are attached to the holding bodies HB1 and HB2.

  The heat transfer member t1 is arranged in a substantially H shape so as to partition the opening a1 and the opening a2 when the lens holder HD is viewed from above, and therefore a part of the heat transfer member t1 is formed by the objective lenses OBJ1 and OBJ2. Arranged between.

  According to this example, the heat generated from the tracking coil TC and the focusing coil FC as heat sources is evenly transmitted to the periphery of the objective lenses OBJ1 and OBJ2 via the heat transfer member t1, and further, the holding body having high heat insulation. Since heat conduction is suppressed by HB1 and HB2, the optical surfaces of the objective lenses OBJ1 and OBJ2 on the side close to the tracking coil TC and the focusing coil FC are suppressed from heating, and the temperature distribution in the optical surface and inside the element is made uniform. be able to. Further, since the objective lenses OBJ1 and OBJ2 are held by the holding bodies HB1 and HB2 having high heat insulating properties, a rapid temperature change can be suppressed, and thus the resistance to disturbance can be increased.

  FIG. 6 is a perspective view of an objective lens unit OU according to another example, and the objective lenses OBJ1 and OBJ2 are incorporated in the lens holder HD. This example differs from the example shown in FIG. 3 only in that thin wall-shaped fins fn extending along the periphery are formed on the upper and lower surfaces of the lens holder HD. Part of the heat from the tracking coil TC and the focusing coil FC arranged around the lens holder HD is radiated through the fins fn, so that heating of the optical surface in the objective lenses OBJ1 and OBJ2 is suppressed. Become. In particular, the heat dissipation effect of the fins fn can be enhanced by using an air flow generated when the optical disk rotates in the vicinity of the lens holder HD. Needless to say, this example can be used in combination with the examples shown in FIGS.

  FIG. 7 is a diagram showing another lens holder HD cut along a plane including the optical axis of the objective lenses OBJ1 and OBJ2. In this example, stepped portions s1 and s2 having reduced diameters are formed in the lower part of the inner periphery of the openings a1 and a2 of the lens holder HD. Between the step portions s1 and s2 and the flange portions f1 and f2 of the objective lenses OBJ1 and OBJ2, a donut disk-shaped heat insulating sheet material (second second) made of a foamed resin having a higher heat insulating property than the material of the lens holder HD. CS1 and CS2 are also arranged (also referred to as members, which are the same in FIG. 8). The side surfaces of the flange portions f1 and f2 are arranged so as not to contact the openings a1 and a2, and the objective lenses OBJ1 and OBJ2 can be bonded to the lens holder HD using an adhesive (not shown). Here, since the heat insulating sheet materials CS1 and CS2 are disposed between the flange portions f1 and f2 of the objective lenses OBJ1 and OBJ2 and the step portions s1 and s2, the heat from the tracking coil TC and the like is thereby shielded. Therefore, heating of the optical surface in the objective lenses OBJ1 and OBJ2 is suppressed. Note that the heat insulating sheet materials CS1 and CS2 are not completely annular, and part of the circumferential direction may be interrupted.

  FIG. 8 is a diagram showing another lens holder HD cut along a plane including the optical axis of the objective lenses OBJ1 and OBJ2. In this example, heat insulating sheet materials CS1 and CS2 having a shape in which a thin circular tube is connected to the outer peripheral edge of a donut disk-shaped sheet are provided in the objective lens unit shown in FIG. That is, the side surfaces of the flange portions f1 and f2 are in contact with the openings a1 and a2 through the side walls of the heat insulating sheet materials CS1 and CS2, and the lower surface thereof is in contact with the step portions s1 and s2 with the heat insulating sheet material CS1. , CS2 is contacted via the bottom wall, and thereby heat from the tracking coil TC or the like can be shielded, so that heating of the optical surface in the objective lenses OBJ1 and OBJ2 is suppressed.

  FIG. 9 is a diagram showing another lens holder HD cut along a plane including the optical axis of the objective lenses OBJ1 and OBJ2. In this example, the flange portions f1 and f2 of the objective lenses OBJ1 and OBJ2 are in direct contact with the step portions s1 and s2 of the lens holder HD with respect to the objective lens unit shown in FIG. Between the holder HD, a heat dissipation member (also referred to as a fourth member) RB having higher heat dissipation (for example, metal) than the material (for example, resin) of the lens holder HD is disposed. Since the heat generated from the tracking coil TC is released into the air through the heat dissipation member RB before being transmitted to the lens holder HD, heating of the optical surface in the objective lenses OBJ1 and OBJ2 is suppressed.

  FIG. 10 is a diagram showing the lens holder HD cut along a plane that does not include the second objective lens and includes the optical axis of the first objective lens OBJ1. In the present embodiment, the first objective lens OBJ1 includes a plurality of optical elements OE1 and OE2, but the second objective lens (not shown) is a single lens. The movable part of the objective lens unit OU includes a lens holder HD and a magnet MG attached thereto. The movable part is fixed to the actuator base ACTB by a plurality of elastic materials SPG so as to be movable in the x and z directions. On the other hand, a yoke YK formed of a magnetic material is supported on the actuator base ACTB, and a coil CL is wound around the yoke YK. The magnetic fluid ML is disposed in a gap between the magnet MG and the coil CL, and is held by a magnetic field generated between the magnet MG and the yoke YK. At this time, the magnetic fluid ML has a heat conductivity that is four times or more that of air, but has a higher heat dissipation than the material of the lens holder HD. The magnet MG, the coil CL, and the yoke YK constitute magnetic field forming means or an actuator. In this example, the magnet MG is attached to the lens holder HD and constitutes a part of the support member.

  During operation, heat generated by the magnet MG can be released to the coil CL side via the magnetic fluid ML. At this time, since the magnetic fluid ML is in a liquid state, it does not cause a slight movement of the movable portion and does not affect the direction of the magnetic field generated in the gap between the magnet MG and the yoke YK. Will not be adversely affected. In addition, since the movable part moves only in the x and z directions, the distance between the magnet MG and the coil CL does not change. For this reason, since the distance in the magnetic fluid through which Joule heat is conducted does not change while the movable part is operating, the heat dissipation characteristics of the objective lens unit OU are stabilized.

  Further, FIG. 11 is a perspective view of another type of lens unit OU '. The lens unit OU ′ shown in FIG. 11 can be disposed in the optical pickup device shown in FIGS. 1 and 2, and the objective lens OBJ1 (for condensing the laser light from the semiconductor laser onto the information recording surface of a different optical disc, respectively). A first objective optical element), OBJ2 (second objective optical element), a lens holder (support member) HD that holds the optical axes of these objective lenses OBJ1 and OBJ2 on the same circumference PC, and this lens An actuator base ACTB that holds the holder HD rotatably through a support shaft SH provided at the position of the center axis of the circumference PC and reciprocally moves along the center axis of rotation, and the lens holder HD as a support shaft A focusing actuator (not shown) for reciprocating movement in a direction along SH, and a rotation operation to the lens holder HD to bias each objective lens OBJ1, O And a tracking actuator TA for positioning the J2. The lens unit OU 'is provided with an operation control circuit (not shown) that controls the operation of each actuator.

  The objective lenses OBJ1 and OBJ2 are respectively installed in holes penetrating the flat plate surface of the disk-shaped lens holder HD, and are disposed at equal distances from the center of the lens holder HD. The lens holder HD is rotatably engaged with an upper end portion of a support shaft SH standing from an actuator base ACTB at the center thereof, and a focusing actuator (not shown) is provided below the support shaft SH. It is arranged.

  That is, the focusing actuator is configured by forming an electromagnetic solenoid by a permanent magnet provided at the lower end portion of the support shaft SH and a coil provided around the support magnet SH, and adjusting the current flowing through the coil to thereby adjust the support shaft SH and the lens. The holder HD is urged to reciprocate in a minute unit in the direction along the support shaft SH (vertical direction in FIG. 11), and the focal length is adjusted.

  Further, as described above, the lens holder HD is given a rotation operation around the support shaft SH having an axis parallel to the optical axis by the tracking actuator TA. The tracking actuator TA includes a pair of tracking coils TCA and TCB that are provided symmetrically on the edge of the lens holder HD with the support shaft SH interposed therebetween, and an actuator base ACTB that is close to the edge of the lens holder HD. Two pairs of magnets MGA, MGB, MGC, and MGD are provided, which are provided at positions symmetrical with respect to the support shaft SH.

  When the tracking coils TCA and TCB are individually opposed to one pair of magnets MGA and MGB, the positions of the magnets MGA and MGB are set so that the objective lens OBJ1 is on the optical path of the laser beam. The positions of the magnets MGC and MGD are set so that the objective lens OBJ2 is on the optical path of the laser beam when facing the magnets MGC and MGD individually.

  In addition, the lens holder HD described above has a stopper (not shown) that limits the rotation range so that the tracking coil TCA and the magnet MGB or the magnet MGD, and the tracking coil TCB and the magnet TGA or the magnet TGC do not face each other. Is provided.

  Further, the tracking actuator TA is disposed so that the tangential direction of the outer periphery of the circular lens holder HD is orthogonal to the tangential direction of the track of the optical disk, and by energizing the lens holder HD in a minute unit, This is for correcting the deviation of the irradiation position with respect to the track of the laser beam. Therefore, in order to perform this tracking operation, for example, it is necessary to slightly bias the lens holder HD while keeping the tracking coils TCA and TCB facing the magnets MGA and MGB.

  In order to perform such tracking operation, each tracking coil TCA, TCB is equipped with an iron piece on the inside thereof, and this iron piece is attracted to each magnet so that a delicate repulsive force is generated between these magnets. In addition, the operation control circuit controls the flow of current through the tracking coils TCA and TCB.

  In this example, a substantially cylindrical holding body (second member) made of a foamed resin having higher heat insulation than the material of the lens holder HD, between the objective lens OBJ1 and the lens holder (also referred to as a first member) HD. (Also referred to as HB) prevents heat from the tracking coils TCA and TCB from being transmitted to the objective lenses OBJ1 and OBJ2. In addition, the structure shown in FIGS. 4-11 can also be added to this example.

In the embodiment described above, at least one of the objective lenses OBJ1 and OBJ2 may be formed from a plastic resin in which inorganic fine particles having a dn / dT of less than 8 × 10 ⁻⁵ and a particle diameter of 30 nm or less are dispersed. good. Alternatively, at least one of the objective lenses OBJ1 and OBJ2 may be formed of glass having a dn / dT of less than 5 × 10 ⁻⁵ . In such a case, since dn / dT is smaller than that of a normal plastic lens, even if the temperature distribution in the optical surface or inside the element is biased, by suppressing the local refractive index change, any optical disk can be used. In contrast, information can be appropriately recorded and / or reproduced. The lens holder HD may hold three or more objective lenses.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, the material of the lens holder is not limited to resin, and metals such as aluminum alloy and magnesium alloy can also be used. When any of the objective lenses is composed of a plurality of optical elements, the present invention can be applied even when the temperature of the optical surface of one optical element close to the heat source is significantly different from the temperature of the optical surface of the remaining optical elements. Is possible.

It is a schematic sectional drawing of the optical pick-up apparatus concerning 1st Embodiment. It is a schematic sectional drawing of the optical pick-up apparatus concerning 2nd Embodiment. It is a disassembled perspective view of the objective lens unit OU that can be used in the embodiment described above. It is a perspective view of objective-lens unit OU concerning another example. It is a perspective view of objective-lens unit OU concerning another example. It is a perspective view of objective-lens unit OU concerning another example. It is a figure which cuts and shows another lens holder HD by the surface containing the optical axis of objective-lens OBJ1 and OBJ2. It is a figure which cuts and shows another lens holder HD by the surface containing the optical axis of objective-lens OBJ1 and OBJ2. It is a figure which cuts and shows another lens holder HD by the surface containing the optical axis of objective-lens OBJ1 and OBJ2. It is a figure which cuts and shows the lens holder HD by the surface which does not contain the objective lens OBJ2 but includes the optical axis of the objective lens OBJ1. It is a perspective view of another lens unit OU '.

Explanation of symbols

ACT Actuator ACTB Actuator base BS Beam shaper CL Coil CL1 Collimate lens CL2 Collimate lens CS1, CS2 Heat insulation sheet material DP Dichroic prism DP1 Dichroic prism DP2 Dichroic prism EXP Expander lens FC Focusing coil G Diffraction grating HB Holder HB1, HB2 Holder HD LC laser chip LD1 Semiconductor laser LD2 Semiconductor laser LD3 Semiconductor laser M Mirror MG Magnet MGA, MGB, MGC, MGD Magnet ML Magnetic fluid OBJ1, OBJ2 Objective lens OD1 Optical disc OD2 Optical disc OD3 Optical disc OE1, OE2 Optical element OU Objective lens unit PBS Polarized beam Splitter PC Circumference PD Photodetector PD3 Photodetector QWP λ / 4 wave plate QWP1 λ / 4 wave plate RB Heat dissipation member SE Optical axis correction element SH Support shaft SL Sensor lens SPG Elastic material TA Tracking actuator TC Tracking coil TCA, TCB Tracking coil TGA Magnet TGC Magnet YK Yoke a1 Opening part a2 Opening part a3 Opening part b1 Objective lens main body f1, f2 Flange part fn Fins h1, h2 Holding parts s1, s2 Step part t1 Heat transfer member

Claims (35)

A first light source having a wavelength λ1, a second light source having a wavelength λ2, and a condensing optical system including a first objective optical element and a second objective optical element; Information can be recorded and / or reproduced by condensing on the information recording surface of the first optical information recording medium via the protective layer of t1, and the protective layer having a thickness of t2 is applied to the light beam from the second light source. An optical pickup device capable of recording and / or reproducing information by focusing on the information recording surface of the second optical information recording medium,
The first objective optical element and the second objective optical element are supported by a support member driven by an actuator,
A first member is disposed on the actuator side between at least one of the first objective optical element and the second objective optical element and the actuator, and is more thermally insulated than the first member. An optical pickup device, wherein a high second member is arranged on at least one side.   The optical pickup device according to claim 1, wherein the support member is formed integrally with the first member.   The optical pickup device according to claim 1, wherein the support member is made of metal.   The optical pickup device according to claim 3, wherein the support member is an aluminum alloy or a magnesium alloy.   The optical pickup device according to claim 1, wherein the support member is made of a first resin material.   The optical pickup device according to claim 5, wherein the first resin material includes a fibrous substance.   The optical pickup device according to claim 5, wherein the support member is made of a liquid crystal polymer.   The optical pickup device according to claim 7, wherein the liquid crystal polymer is a wholly aromatic polyester.   6. The optical pickup device according to claim 5, wherein the support member is a composite of glass fiber and liquid crystal polymer.   The optical pickup device according to claim 1, wherein the support member has a heat radiating fin on an outer periphery or in the vicinity thereof.   The optical pickup device according to claim 1, further comprising: a magnetic field forming unit that forms a magnetic field around the support member; and a magnetic fluid that contacts the periphery of the support member.   The optical pickup device according to claim 1, wherein the second member is made of a second resin material.   The optical pickup device according to claim 12, wherein the second resin material is a resin foam.   The optical pickup device according to claim 12, wherein the second member is a sheet material.   The optical pickup device according to claim 1, wherein the second member is annular.   The part according to any one of claims 1 to 15, wherein a portion having a higher thermal conductivity than the second member is provided between the first objective optical element and the second objective optical element. The optical pickup device described.   The optical pickup according to claim 1, wherein the wavelength λ1 is not less than 380 nm and not more than 450 nm, and the second member is disposed only around the first objective optical element. apparatus.   The maximum numerical aperture of the first objective optical element is larger than the maximum numerical aperture of the second objective optical element, and the second member is disposed only around the first objective optical element. The optical pickup device according to claim 1, wherein:   The light flux from the first light source that has passed through the first objective optical element or the light flux from the second light source that has passed through the second objective optical element has a thickness t3 (t3> t1 or t3> t2). 19. The optical pickup device according to claim 1, wherein information is recorded and / or reproduced by condensing light on the information recording surface of the third optical information recording medium via a protective layer. .   The optical pickup device according to claim 19, wherein the first optical information recording medium is an HD DVD, the second optical information recording medium is a DVD, and the third optical information recording medium is a CD. .   20. The optical pickup device according to claim 19, wherein the first optical information recording medium is a Blu-ray disc, the second optical information recording medium is a DVD, and the third optical information recording medium is a CD. .   The first objective optical element has two or more optical elements, and the second objective optical element has a single optical element. The optical pickup device described.   Information is recorded and / or reproduced by a light beam condensed on one information recording surface of Blu-ray Disc, DVD and CD by the first objective optical element, and HD is recorded by the second objective optical element. 23. The optical pickup device according to claim 22, wherein information is recorded and / or reproduced by a light beam condensed on an information recording surface of the DVD.   Information is recorded and / or reproduced by a light beam condensed on one information recording surface of HD DVD, DVD and CD by the first objective optical element, and Blu-ray is recorded by the second objective optical element. 23. The optical pickup device according to claim 22, wherein information is recorded and / or reproduced by a light beam condensed on an information recording surface of the disc.   The optical pickup device according to claim 1, wherein the second member is disposed around each of the first objective optical element and the second objective optical element.   The optical pickup according to claim 1, wherein the second member is disposed so as to surround both the first objective optical element and the second objective optical element. apparatus. A first light source having a wavelength λ1, a second light source having a wavelength λ2, and a condensing optical system including a first objective optical element and a second objective optical element; Information can be recorded and / or reproduced by condensing on the information recording surface of the first optical information recording medium via the protective layer of t1, and the protective layer having a thickness of t2 is applied to the light beam from the second light source. An optical pickup device capable of recording and / or reproducing information by focusing on the information recording surface of the second optical information recording medium,
The first objective optical element and the second objective optical element are supported by a support member driven by an actuator,
A third member having a thermal conductivity higher than that of the support member is disposed between the support member and the actuator. A first light source having a wavelength λ1, a second light source having a wavelength λ2, and a condensing optical system including a first objective optical element and a second objective optical element; Information can be recorded and / or reproduced by condensing on the information recording surface of the first optical information recording medium via the protective layer of t1, and the protective layer having a thickness of t2 is applied to the light beam from the second light source. An optical pickup device capable of recording and / or reproducing information by focusing on the information recording surface of the second optical information recording medium,
The first objective optical element and the second objective optical element are supported by a support member driven by an actuator,
4. An optical pickup device, wherein a fourth member having higher heat dissipation than the support member is disposed between the support member and the actuator.   The optical pickup device according to claim 28, wherein fins or gaps are formed in the fourth member.   30. The optical pickup device according to claim 27, wherein the support member is made of a resin material.   The optical pickup device according to claim 30, wherein the resin material includes a fibrous substance.   The optical pickup device according to claim 30, wherein the support member is made of a liquid crystal polymer.   33. The optical pickup device according to claim 27, further comprising: a magnetic field forming unit that forms a magnetic field around the support member; and a magnetic fluid that contacts the periphery of the support member.   2. At least one of the first objective optical element and the second objective optical element is formed of an organic-inorganic composite in which inorganic fine particles having a particle size of 30 nm or less are dispersed. 34. The optical pickup device according to any one of -33. The optical pickup device according to any one of claims 1 to 34, wherein at least one of the first objective optical element and the second objective optical element is made of glass.

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