JP2007087500A - Optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device for appropriately recording and/or reproducing information with respect to e.g. a high density DVD and all of the conventional DVDs and CDs. <P>SOLUTION: Since heat generated from tracking coils TC to be heat sources is conducted to a lens holder HD and heat conduction is suppressed by heat shielding members p1 and p2 having low heat conductivity, heating of optical surfaces of objective lenses OBJ1 and OBJ2 on the sides far from the tracking coils TC is promoted via the lens holder HD having high heat conductivity while heating of optical surfaces of the objective lenses OBJ1 and OBJ2 on the side near to the tracking coils TC is suppressed and evenness of temperature distribution of the optical surfaces as a whole can be achieved. <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 or more objective optical elements, thereby providing information to 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 on the optical surface of the objective optical element is asymmetric with respect to the optical axis. On the other hand, even if the temperature distribution on the optical surface of the objective optical element is point-symmetric, spherical aberration occurs if there is a temperature gradient toward the optical axis. As described above, when a temperature distribution in the direction perpendicular to the optical axis and / or in the optical axis direction occurs in the objective optical element and the temperature difference becomes excessive, thermal expansion of the optical surface is caused and recording and / or reproduction of appropriate information is hindered. There is a risk of causing aberration deterioration. 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 a problem, and an optical pickup device capable of appropriately recording and / or reproducing information with respect to different optical information recording media using two or more objective optical elements. The purpose is to provide.

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 (λ1 <λ2), and a light collecting device including at least a first objective optical element and a second objective optical element. And condensing the light beam from the first light source on the information recording surface of the first optical information recording medium through the protective layer having a thickness of t1 using the first objective optical element. Information can be recorded and / or reproduced, and the light beam from the second light source is applied to the information recording surface of the second optical information recording medium through the protective layer having a thickness of t2 using the second objective optical element. An optical pickup device capable of recording and / or reproducing information by collecting light,
The first objective optical element and the second objective optical element are fixed to a support member driven by an actuator,
Controlling heat transmitted to at least one of the first objective optical element and the second objective optical element via the support member by conducting a portion having a different thermal conductivity in the support member. It is characterized by.

  When the first objective optical element and the second objective optical element are heated by a heat source such as an actuator, the temperature on the optical surface of the objective optical element is controlled by controlling heat conduction in the support member. The uneven distribution can be suppressed and the maximum temperature can be lowered. More specifically, by providing the support member with a portion having a high thermal conductivity and a portion having a low thermal conductivity, the heat conductivity is increased when heat from a heat source is transmitted to the support member. The heat dissipation effect is enhanced by conducting through a high part, and the heat shielding effect is enhanced by conducting through a part having low thermal conductivity, and the first objective optical element and the second are enhanced by their synergistic effect. An optical information recording medium capable of making the temperature distribution of at least one optical surface of the objective optical elements uniformly uniform and suppressing the maximum temperature, thereby suppressing aberration deterioration in a light beam passing through the objective optical element. Information can be appropriately recorded and / or reproduced.

  According to a second aspect of the present invention, in the invention according to the first aspect, the support member includes a first part provided between the objective optical element and the actuator, and the first part. And a second portion having a higher thermal conductivity than the second portion.

The optical pickup device according to claim 3 includes a first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a light collecting device including at least a first objective optical element and a second objective optical element. And condensing the light beam from the first light source on the information recording surface of the first optical information recording medium through the protective layer having a thickness of t1 using the first objective optical element. Information can be recorded and / or reproduced, and the light beam from the second light source is applied to the information recording surface of the second optical information recording medium through the protective layer having a thickness of t2 using the second objective optical element. An optical pickup device capable of recording and / or reproducing information by collecting light,
The first objective optical element and the second objective optical element are fixed to a support member driven by an actuator,
The support member has a gap between at least one of the first objective optical element and the second objective optical element and the actuator.

  When the first objective optical element and the second objective optical element are heated by a heat source such as an actuator, the temperature on the optical surface of the objective optical element is controlled by controlling heat conduction in the support member. The uneven distribution can be suppressed and the maximum temperature can be lowered. More specifically, in the support member, by providing a gap between at least one of the first objective optical element and the second objective optical element and the actuator, the heat from the heat source is Increases the heat shielding effect when transmitted to the support member, makes the temperature distribution of at least one of the first objective optical element and the second objective optical element uniform, and suppresses the maximum temperature. Accordingly, it is possible to appropriately record and / or reproduce information with respect to the optical information recording medium while suppressing aberration deterioration in the light beam passing through the objective optical element. As a space | gap, the hollow and the opening which penetrated the support member are included. As the shape of the separate member or the gap, various shapes such as a circle, an oval, a triangle, a quadrangle, and a polygon can be taken.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the actuator includes at least one of a tracking coil and a focusing coil, and the at least one coil is the first coil. The first objective optical element and the second objective optical element are arranged asymmetrically with respect to at least one of the first objective optical element and the second objective optical element. Therefore, even when the at least one coil serves as a heat source, The temperature distribution on at least one optical surface of the objective optical element and the second objective optical element can be made uniform and the maximum temperature can be suppressed.

  Since the objective optical element is supported by the support member, when attention is paid to one objective optical element, for example, it is difficult to symmetrically arrange the actuator that can be a heat source. The optical surface close to the actuator may be easily heated. Therefore, in the present invention, by providing a portion having a lower thermal conductivity than the material of the lens holder, for example, between the objective optical element and the actuator, the heat transmitted to the objective optical element is suppressed, and the optical The surface temperature distribution can be made uniform and the maximum temperature can be suppressed. The first part may be a part having higher thermal conductivity than the second part, and thereby heat radiation can be promoted.

  According to a fifth aspect of the present invention, there is provided the optical pickup device according to any one of the first to fourth aspects, wherein the objective optical element extends in a direction perpendicular to a perpendicular line drawn from the actuator closest to the optical axis to the optical axis. The surface on which the objective optical element is in contact with the support member on the side close to the nearest actuator when divided into a side close to the nearest actuator and a side far from the nearest actuator by cutting along a virtual plane including the optical axis Is smaller than the surface area where the objective optical element is in contact with the support member on the side farthest from the nearest actuator, so that the support member on the side near the nearest actuator that can serve as a heat source. By reducing the surface area in contact with the objective optical element, heat conduction is suppressed and the temperature of the optical surface of the objective optical element is reduced. It causes uniform distribution, it is possible to suppress the maximum temperature.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the support member includes a first opening for mounting the first objective optical element, and the second A second opening for mounting the objective optical element, and at least one of the first opening and the second opening is lowered from the actuator closest to the objective optical element mounted on the optical axis to the optical axis. Mounting on the side closest to the nearest actuator when it is divided into the side closer to the nearest actuator and the side farther away by cutting in a virtual plane that extends in a direction perpendicular to the perpendicular and includes the optical axis The gap formed between the objective optical element and the objective optical element is larger than the gap formed between the objective optical element mounted on the side far from the nearest actuator. Since it is a feature, on the side close to the nearest actuator that can be a heat source, a heat shielding effect is enhanced by utilizing a gap between the support member and the objective optical element, and the temperature distribution of the optical surface of the objective optical element is increased. It can be made uniform and the maximum temperature can be suppressed.

  According to a seventh aspect of the present invention, in the invention of the sixth aspect, at least one of the first opening and the second opening is formed on the objective optical element mounted from the inner periphery thereof. A holding portion that extends toward the actuator, and a notch is formed in the holding portion on the side close to the actuator, so that heat conduction through the holding portion can be suppressed. .

  An optical pickup device according to an eighth aspect of the present invention is the optical pickup device according to the sixth aspect, wherein at least one of the first opening and the second opening is formed on the objective optical element mounted from the inner periphery thereof. A holding portion that extends toward the surface of the objective optical element on which the holding portion is mounted is provided with irregularities at least on the side close to the actuator. The heat conduction through the holding part can be suppressed.

  The optical pickup device according to claim 9 is characterized in that, in the invention according to any one of claims 1 to 8, fins and / or voids are formed on the surface of the support member. The heat dissipation effect of the support member can be enhanced.

  An optical pickup device according to a tenth aspect is the invention according to any one of the first to ninth aspects, wherein the support member is provided between the first objective optical element and the second objective optical element. And the second part having a lower thermal conductivity than the third part, so that the optical element of the objective optical element is inserted through the part having the higher thermal conductivity. By rapidly heating the low temperature region on the surface, the temperature distribution as a whole can be made uniform. Note that the third part may be a part having lower thermal conductivity than the second part, whereby heat transferred to the third part is reduced, and the third part It has the effect of raising the ambient temperature.

  An optical pickup device according to an eleventh aspect is the optical pickup device according to any one of the first to tenth aspects, wherein at least one of the first objective optical element and the second objective optical element has a particle size of 30 nm or less. It is formed from a plastic resin in which inorganic fine particles are dispersed.

  For example, the inorganic fine particles dispersed in the thermoplastic resin as the plastic resin are not particularly limited, and the rate of change in refractive index with temperature of the resulting thermoplastic resin composition (hereinafter referred to as | dn / dT |) is small. Any inorganic fine particles that can achieve the object of the present invention can be selected. 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 twelfth aspect is the invention according to any one of the first to tenth 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.

  An optical pickup device according to a thirteenth aspect of the present invention is the optical pickup apparatus according to any one of the first to twelfth aspects, 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 reproduction is performed, so that information can be recorded and / or reproduced on any of high-density DVD, DVD, and CD, for example.

  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.

  According to the present invention, it is possible to provide an optical pickup device that can appropriately record and / or reproduce information on different optical information recording media using two or more objective optical elements.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 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 1st Embodiment.

  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 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 collimator lens CL1 passes through a diffraction grating G, which is 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. Passes through the splitter PBS, the expander lens EXP, and the dichroic prism DP.

  The light beam that has passed through the dichroic prism DP passes through the λ / 4 wave plate QWP, is condensed by the first objective lens OBJ1, and is a protective layer (thickness t1 = 0.1-0) of the first optical disk OD1. .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 dichroic prism DP, and the expander lens EXP, and is reflected by the polarization beam splitter PBS. Further, since the light passes through the sensor lens SL, passes through the optical axis correction element SE, and enters the light receiving surface of the photodetector PD, the information recorded on the first optical disc OD1 is read using the output signal. A signal is obtained. The optical axis correction element SE is irradiated from either side by correcting an optical axis shift that occurs when at least one of the first semiconductor laser LD1 and the second semiconductor laser LD2 is shifted. The light beam also functions so as to be condensed at the optimum position on the light receiving surface of the photodetector PD.

  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) passes through the beam shaper BS, the shape of the light beam is corrected, and then enters the first collimator lens CL1 to become a parallel light beam. . The light beam emitted from the first collimating lens CL1 passes through the diffraction grating G, and further passes through the polarizing beam splitter PBS, the expander lens EXP, and the dichroic prism DP.

  The light beam that has passed through the dichroic prism DP passes through the λ / 4 wavelength plate QWP, is condensed by the first objective lens OBJ1, and is a protective layer (thickness t2 = 0.5 to 0) of the second optical disk OD2. .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 first objective lens OBJ1, λ / 4 wavelength plate QWP, dichroic prism DP, and expander lens EXP, and is reflected by the polarization beam splitter PBS. Furthermore, since it passes through the sensor lens SL, passes through the optical axis correction element SE, and enters the light receiving surface of the photodetector PD, the output signal is used to read information recorded on the second optical disc OD2. 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 second semiconductor laser LD2 forms an image 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, the actuator base ACTB is moved by an actuator (not shown) so that the optical axis of the second objective lens OBJ2 is positioned with the optical axis of the λ / 4 wavelength plate QWP.

  After 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 second collimating lens CL2, the divergence angle is changed, and then reflected by the dichroic prism DP, The information recording surface passes through the λ / 4 wavelength plate QWP, is condensed by the second objective lens OBJ2, and passes through the protective layer (thickness t3 = 1.1 to 1.3 mm) of the third optical disk OD3. And a condensed 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 dichroic prism DP, and is further collected by the second collimating lens CL2. Since the light is 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 collimator lens CL1 passes through a diffraction grating G, which is 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 splitter PBS, the expander lens EXP, the first dichroic prism DP1, and the λ / 4 wavelength plate QWP, and is reflected by the second dichroic prism DP2.

  The light beam reflected by the second dichroic prism DP2 is condensed by the first objective lens OBJ1 and 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 information 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 second dichroic prism DP2, and is a λ / 4 wavelength plate QWP1, first dichroic prism DP1. Then, the light passes through the expander lens EXP, is reflected by the polarization beam splitter PBS, passes through the sensor lens SL, passes through the optical axis correction element SE, and enters the light receiving surface of the photodetector PD. As a result, a read signal of information recorded on the first optical disk OD1 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) passes through the beam shaper BS, the shape of the light beam is corrected, and then enters the first collimator lens CL1 to become a parallel light beam. . The light beam emitted from the first collimating lens CL1 passes through the diffraction grating G, and further passes through the polarizing beam splitter PBS, the expander lens EXP, the first dichroic prism DP1, and the λ / 4 wavelength plate QWP, and the second dichroic prism DP2. It is reflected by.

  The light beam reflected by the second dichroic prism DP2 is condensed by the first objective lens OBJ1 and is passed through the protective layer (thickness t2 = 0.5 to 0.7 mm) of the second optical disk OD2. The light is condensed on the information recording surface to form a condensing 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, is reflected by the second dichroic prism DP2, and is reflected by the λ / 4 wavelength plate QWP and the first dichroic prism DP1. Since it passes through the expander lens EXP, is reflected by the polarization beam splitter PBS, further passes through the sensor lens SL, passes through the optical axis correction element SE, and enters the light receiving surface of the photodetector PD, the output signal is used. Thus, a read signal of information recorded on the second optical disk OD2 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 second semiconductor laser LD2 forms an image 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) is reflected by the first dichroic prism DP1 after passing through the second collimating lens CL2 and changing the divergence angle. After that, the light passes through the λ / 4 wavelength plate QWP and the second dichroic prism DP2, is reflected by the mirror M, is condensed by the second objective lens OBJ2, and is protected by the protective layer (thickness t3) of the third optical disk OD3. = 1.1 to 1.3 mm), the light is condensed on the information 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 second objective lens OBJ2, is reflected by the mirror M, passes through the second dichroic prism DP2, and the λ / 4 wavelength plate QWP. Since the light is reflected by the first dichroic prism DP1, further condensed by the second collimating lens CL2, and incident on the light receiving surface of the photodetector PD3 in the third semiconductor laser LD3, the output signal is used to generate the third A read signal of information recorded on the optical disk OD3 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.

  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 diffractive structure or an optical path difference. It can have a structure. Furthermore, these optical surfaces can also be divided into special annular zones.

  The lens holder HD is formed by arranging a circular opening (also referred to as a first opening) a1 and an opening (also referred to as a second opening) a2 in the longitudinal direction. The inner diameters of the openings a1 and a2 are preferably larger than the outer diameters of the flanges f1 and f2 of the objective lens. In addition, holding parts h1 and h2 projecting annularly 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 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.

  The resin lens holder HD has rectangular openings r1 and r2 penetrating vertically between the tracking coil TC and the openings a1 and a2. In the openings r1 and r2, heat shield members p1 and p2 made of a material (for example, ceramic) having a lower thermal conductivity than the material of the lens holder HD are fitted. Here, the heat shield members p1. p2 constitutes the first part, and the other lens holder HD constitutes the second part having a higher thermal conductivity than the first part.

  According to the present embodiment, heat generated from the tracking coil TC serving as a heat source is transmitted to the lens holder HD, but heat conduction is suppressed by the heat shield members p1 and p2 having lower thermal conductivity than the lens holder HD. Therefore, the optical surfaces of the objective lenses OBJ1 and OBJ2 closer to the tracking coil TC are suppressed from heating, whereas the optical surfaces of the objective lenses OBJ1 and OBJ2 far from the tracking coil TC have high thermal conductivity. Heating is promoted through the lens holder HD, and the temperature distribution of the optical surface as a whole can be made uniform.

  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 this example, no member is arranged in the rectangular openings r1 and r2 penetrating vertically so that a gap is formed. According to this example, the heat generated from the tracking coil TC serving as a heat source is transmitted to the lens holder HD, but the heat conduction is suppressed by the air in the openings r1 and r2 having low thermal conductivity. The temperature distribution on the optical surfaces of OBJ1 and OBJ2 can be made uniform.

  FIG. 5 is a perspective view of an objective lens unit OU according to still another example. In this example, each of the openings r1 and r2 is divided into two parts, and the side surfaces on the side of the openings a1 and a2 are shaped to follow them. Therefore, it is possible to secure a large volume of the voids that constitute the first part. The openings r1 and r2 may be filled with a member having a lower thermal conductivity than the lens holder HD.

  FIG. 6 is a perspective view of an objective lens unit OU according to still another example. In the lens holder HD of this example, openings r3 and r4 are formed between the focusing coil FC and the openings a1 and a2 in addition to the openings r1 and r2. This example is effective when the focusing coil FC is a heat source that generates a relatively large amount of heat, and conduction of heat generated therefrom is suppressed by the air in the openings r3 and r4 having low thermal conductivity. Therefore, the temperature distribution of the optical surfaces of the objective lenses OBJ1 and OBJ2 can be made uniform. Moreover, since the surface area of the lens holder HD is increased by providing the openings r1 to r4, the heat dissipation effect is also enhanced. Furthermore, by using the wind flow generated when the optical disk rotates in the vicinity of the lens holder HD, the air heated by the openings r1 to r4 can be driven out, and the heat shielding effect can be further enhanced.

  FIG. 7 is a perspective view of an objective lens unit OU according to still another example. The lens holder HD of this example has an opening r5 between the openings a1 and a2. The opening r5 has an arc shape in which both side surfaces follow the inner peripheral surface of the openings a and a2, and has a shape that widens in the longitudinal direction. A heat transfer member t1 made of a material (for example, aluminum) having a higher thermal conductivity than that of the lens holder HD is fitted in the opening r5. That is, the heat transfer member t1 transfers the heat generated from the tracking coil TC and the forcing coil FC, which are heat sources, to the back side of the objective lenses OBJ1 and OBJ2 away from them, thereby the temperature distribution of the optical surface as a whole. Uniformity can be achieved. Here, the heat transfer member t1 constitutes a third part having a high thermal conductivity, and the other lens holder HD constitutes a second part having a thermal conductivity lower than that of the third part.

  FIG. 8 is an exploded perspective view of an objective lens unit OU that can be used in the above-described embodiment. In this example, the holding portions h1 and h2 formed on the inner periphery of the openings a1 and a2 of the lens holder HD are not completely annular and have notches c1 and c2 on the tracking coil TC side.

  Here, when the flange portions f1 and f2 of the objective lenses OBJ1 and OBJ2 are placed on the holding portions h1 and h2, the portions of the notches c1 and c2 do not contact the flange portions f1 and f2. In other words, the objective lenses OBJ1 and OBJ2 are cut from a tracking coil TC constituting the actuator closest to the objective lenses OBJ1 and OBJ2 along a virtual plane that extends in a direction perpendicular to the perpendicular line drawn down to the optical axis and includes the optical axis. Thus, when divided into a side closer to the tracking coil TC and a side farther from the tracking coil TC, the area of the surface of the objective lens in contact with the lens holder HD on the side closer to the tracking coil TC can be larger It is smaller than the area of the surface of the objective lens in contact. Accordingly, heating of the optical surfaces of the objective lenses OBJ1 and OBJ2 closer to the tracking coil TC is suppressed.

  FIG. 9 is an exploded perspective view of an objective lens unit OU that can be used in the above-described embodiment. This example is an example in which the number of notches c1 and c2 is further increased with respect to the holding portions h1 and h2 formed on the inner periphery of the openings a1 and a2 of the lens holder HD shown in FIG. The optical surfaces in OBJ1 and OBJ2 are further suppressed from heating.

  FIG. 10 is an exploded perspective view of an objective lens unit OU that can be used in the above-described embodiment. In this example, a part of the inner circumference of the openings a1 and a2 of the lens holder HD close to the tracking coil TC side is cut out and removed together with the holding parts h1 and h2 formed on the inner circumference, thereby expanding the opening. Portions e1 and e2 are formed. In other words, the enlarged openings e1 and e2 extend in a direction perpendicular to the perpendicular line extending from the tracking coil TC constituting the actuator closest to the objective lens attached thereto to the optical axis, and the optical axis is By cutting along the imaginary plane, the gap formed between the objective lens mounted on the side close to the tracking coil TC is separated from the side near the tracking coil TC in the tracking coil TC. It is larger than the gap formed between the objective lens mounted on the far side. Accordingly, heating of the optical surface of the objective lenses OBJ1 and OBJ2 on the side close to the tracking coil TC is suppressed.

  FIG. 11 is a diagram showing the lens holder HD cut along a virtual plane including both the optical axis of the objective lens OBJ1 and the optical axis of the objective lens OBJ2. In this example, stepped portions s1 and s2 with reduced diameters are formed in the lower part of the inner periphery of the openings a1 and a2. Ring zone grooves (also referred to as recesses) g1 and g2 are formed on the upper surfaces of the step portions s1 and s2, respectively. The flange portions f1 and f2 of the objective lenses OBJ1 and OBJ2 are arranged on the upper surfaces of the step portions s1 and s2 so that the side surfaces thereof do not contact the openings a1 and a2, and the lens holder HD is used with an adhesive (not shown). The objective lenses OBJ1 and OBJ2 can be bonded to each other. Here, since the annular grooves g1 and g2 are formed between the flange portions f1 and f2 and the step portions s1 and s2 of the objective lenses OBJ1 and OBJ2, the tracking coil TC is formed by the air sealed therein. Therefore, the heating of the optical surface in the objective lenses OBJ1 and OBJ2 is suppressed. It should be noted that the same effect can be obtained by forming an annular projection on the upper surfaces of the step portions s1 and s2. It is sufficient that the step portions s1 and s2 are provided at least on the actuator side.

  FIG. 12 is an exploded perspective view of an objective lens unit OU that can be used in the above-described embodiment. In this example, thin-walled 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, the examples shown in FIGS. 3 to 12 can be used in combination as long as they do not interfere with each other.

  FIG. 13 is a perspective view of another lens unit OU '. The lens unit OU ′ shown in FIG. 13 can be arranged in the optical pickup device shown in FIGS. 1 and 2, and an objective lens OBJ1 (for condensing laser light from a semiconductor laser on information recording surfaces of different optical disks, 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 urge the objective lenses 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. 13), 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 plurality of circular openings CA are formed in the lens holder HD, thereby suppressing heat from the tracking coils TCA, TCB from being transmitted to the objective lenses OBJ1, OBJ2. In addition to filling the circular opening CA including the first portion with a material having a lower thermal conductivity than the lens holder HD, the structures shown in FIGS. 7 to 11 can be added.

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 when the temperature distribution of the optical surface is biased, by suppressing the local refractive index change, any optical disk can be controlled. Information can be recorded and / or reproduced appropriately. 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 perspective view of objective-lens unit OU concerning another example. It is a disassembled perspective view of another objective-lens unit OU which can be used for embodiment mentioned above. It is a disassembled perspective view of another objective-lens unit OU which can be used for embodiment mentioned above. It is a disassembled perspective view of another objective-lens unit OU which can be used for embodiment mentioned above. It is a figure which cuts and shows the lens holder HD by the virtual plane in which both the optical axis of objective lens OBJ1 and the optical axis of objective lens OBJ2 are included. It is a disassembled perspective view of another objective-lens unit OU which can be used for embodiment mentioned above. It is a perspective view of another lens unit OU '.

Explanation of symbols

ACT Actuator ACTB Actuator base BS Beam shaper CA Circular aperture CL1 First collimating lens CL2 Second collimating lens DP Dichroic prism DP1 First dichroic prism DP2 Second dichroic prism EXP Expander lens FC Focusing coil G Diffraction grating HD Lens holder LC Laser chip LD1 Semiconductor laser LD2 Semiconductor laser LD3 Semiconductor laser M Mirror MGA, MGB, MGC, MGD Magnet OBJ1, OBJ2 Objective lens OD1 Optical disc OD2 Optical disc OD3 Optical disc OU, OU 'Objective lens unit PBS Polarizing beam splitter PC Circumferential PD Photodetector QWP λ / 4 wave plate S1, S2 Step SE Optical axis correction element SH Support axis SL Sensor lens A tracking actuator TC tracking coil TCA, TCB tracking coil a opening a opening a1, a2 opening b1 objective lens body c1, c2 notch e1 enlarged opening f1, f2 flange part fn fin g1, g2 annular groove h1, h2 holding part p1, p2 heat shield members r1-r4 opening r5 opening s1, s2 step t1 heat transfer member

Claims (13)

A first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a condensing optical system including at least a first objective optical element and a second objective optical element; Information can be recorded and / or reproduced by condensing the light beam from the light onto the information recording surface of the first optical information recording medium through the protective layer having a thickness of t1 using the first objective optical element. The information recording and / or by focusing the light beam from the second light source on the information recording surface of the second optical information recording medium through the protective layer having a thickness t2 using the second objective optical element. An optical pickup device capable of reproduction,
The first objective optical element and the second objective optical element are fixed to a support member driven by an actuator,
Controlling heat transmitted to at least one of the first objective optical element and the second objective optical element via the support member by conducting a portion having a different thermal conductivity in the support member. An optical pickup device characterized by the above.   The support member includes a first part provided between the objective optical element and the actuator, and a second part having higher thermal conductivity than the first part. Item 4. The optical pickup device according to Item 1. A first light source having a wavelength λ1, a second light source having a wavelength λ2 (λ1 <λ2), and a condensing optical system including at least a first objective optical element and a second objective optical element; Information can be recorded and / or reproduced by condensing the light beam from the light onto the information recording surface of the first optical information recording medium through the protective layer having a thickness of t1 using the first objective optical element. The information recording and / or by focusing the light beam from the second light source on the information recording surface of the second optical information recording medium through the protective layer having a thickness t2 using the second objective optical element. An optical pickup device capable of reproduction,
The first objective optical element and the second objective optical element are fixed to a support member driven by an actuator,
The optical pickup device, wherein the support member has a gap between at least one of the first objective optical element and the second objective optical element and the actuator.   The actuator includes at least one of a tracking coil and a focusing coil, and the at least one coil is disposed asymmetrically with respect to at least one of the first objective optical element and the second objective optical element. The optical pickup device according to claim 1, wherein   By cutting the objective optical element in a direction perpendicular to a perpendicular line extending from the closest actuator to the optical axis and including the optical axis, a side closer to and far from the nearest actuator When the objective optical element is in contact with the support member on the side closer to the nearest actuator, the area of the surface on which the objective optical element is in contact with the support member on the side farther from the nearest actuator. The optical pickup device according to claim 1, wherein the optical pickup device is smaller than the optical pickup device.   The support member includes a first opening for mounting the first objective optical element, and a second opening for mounting the second objective optical element. The first opening and the second opening By cutting at least one of the apertures in an imaginary plane extending in a direction perpendicular to a perpendicular extending from the actuator closest to the objective optical element attached thereto to the optical axis and including the optical axis, When divided into a side close to the nearest actuator and a side far from the nearest actuator, a gap formed between the objective optical element attached on the side close to the nearest actuator is attached on the side far from the nearest actuator. The optical pickup device according to claim 1, wherein the optical pickup device is larger than a gap formed between the objective optical element.   At least one of the first opening and the second opening has a holding portion extending from an inner periphery thereof toward the mounted objective optical element. 7. The optical pickup device according to claim 6, wherein a notch is formed on a side close to the actuator.   At least one of the first opening and the second opening has a holding portion extending from an inner periphery thereof toward the attached objective optical element, and the holding portion is attached. 7. The optical pickup device according to claim 6, wherein unevenness is formed on a surface in contact with the objective optical element at least on a side close to the actuator.   9. The optical pickup device according to claim 1, wherein fins and / or voids are formed on the surface of the support member.   The support member includes a third part provided between the first objective optical element and the second objective optical element, and a second part having a lower thermal conductivity than the third part. The optical pickup device according to claim 1, comprising:   11. At least one of the first objective optical element and the second objective optical element is formed of a plastic resin in which inorganic fine particles having a particle size of 30 nm or less are dispersed. The optical pickup device according to any one of the above.   The optical pickup device according to claim 1, wherein at least one of the first objective optical element and the second objective optical element is made of glass. The light beam from the first light source that has passed through the first objective optical element or the light beam from the second light source that has passed through the second objective optical element has a thickness t3 (t3> t1 or t3> t2). 13. 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. .

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