JP2007073114A - Objective lens unit and its manufacturing method, and optical pickup unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact objective lens unit which is an objective lens unit for optical pickup apparatus used compatibly, in which highly accurate image formation can be attained, and simple and low cost reflection-prevention is achieved. <P>SOLUTION: Since a compound objective lens 20 in which a first lens part 21 and a second lens part 22 having different specifications are arranged adjacently are used, a spot compatible with a standard can be formed in an information recording plane for a BD and for a DVD by operation-arrangement either of the first and the second lens parts 21, 22 on an optical path. Also, since a common reflection preventing coat 53 compatible with a laser beam of first wavelength λ1 and a laser beam of second wavelength λ2 are provided at optical planes 21a, 21b of the first lens part 21 and optical planes 22a, 22b of the second lens part 22, the reflection preventing coat 53 can be collectively formed at the first lens part 21 and the second lens part 22. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an objective lens unit suitable as an objective system for an optical pickup and a method for manufacturing the objective lens unit, and further relates to an optical pickup apparatus including the objective lens unit.

Up to now, various optical pickup devices for reproducing and recording information on optical information recording media such as CD (compact disc) and DVD (digital versatile disc) have been developed and manufactured, and are widely used. Yes. “Reproduction / recording of information” means reproduction and / or recording of information. As an objective lens incorporated in such an optical pickup device, there is a composite objective lens in which a plurality of lens elements are fixed in a holder, and information can be easily reproduced / recorded on a different type of recording medium. (See Patent Document 1). In addition, as a similar objective lens, there is a composite objective lens in which a plurality of lens elements are combined and integrally molded. In this case, the composite objective lens is miniaturized by integral molding, and the assembly process is simplified (Patent Document). 2-5). There is also an objective lens formed by embedding two microlenses having different focal lengths in a glass substrate having a relatively low refractive index (see Patent Document 6).
JP 2001-67700 A JP-A-9-115170 Japanese Patent Application Laid-Open No. 9-306021 JP-A-10-275356 JP-A-9-63083 JP 2000-90472 A

  However, in a compound objective lens in which a plurality of lens elements are fitted and fixed in a holder, the objective lens is large and the assembly process is likely to be complicated. In particular, alignment between the plurality of lens elements is not easy.

  On the other hand, in the case of a compound objective lens in which a plurality of lens elements are combined and integrally molded, the objective lens can be made relatively small and the assembly process can be simplified and reduced in cost. It is not easy to form a separate antireflection film suitable for the wavelength used. Actually, a multilayer film is formed on the optical surface of the other lens element while protecting one lens element with a mask, and a multilayer film is formed on the optical surface of the one lens element while protecting the other lens element with a mask. A manufacturing method of forming a film is used. Here, in the case of a mask that is surely shielded, it is not easy to replace the mask, and in the case of a mask that is easy to replace, there is a high possibility that unnecessary components adhere to the other lens element when forming one lens element. .

  In the case of an objective lens formed by embedding two microlenses in a glass substrate having a relatively low refractive index, the processing process is extremely complicated, and the degree of freedom of optical characteristics that can be set for the objective lens obtained as a result. Will also be limited. Furthermore, it is not easy to form an individual antireflection film on the optical surface of each microlens.

  Therefore, the present invention provides an objective lens unit for an optical pickup device used for interchangeable purposes, which enables compact and high-precision imaging, and realizes simple and low-cost anti-reflection. The purpose is to do.

  Another object of the present invention is to provide an optical pickup device for compatibility, which realizes high recording / reproducing accuracy at low cost.

  It is another object of the present invention to provide a method for manufacturing an objective lens unit that realizes simple and low-cost antireflection.

  In order to solve the above-described problems, an objective lens unit for an optical pickup device according to the present invention is used with a first lens unit used for light of a first wavelength and light of a second wavelength different from the first wavelength. An integrated objective lens unit that includes a second lens unit, and the first lens unit and the second lens unit are disposed adjacent to each other, the optical surface of the first lens unit and the optical surface of the second lens unit, A common antireflection film is provided that matches the light of the first wavelength and the light of the second wavelength.

  In the objective lens unit, since the objective lens is an integral type (integral molding) in which the first lens portion and the second lens portion are arranged adjacent to each other, either the first lens portion or the second lens portion is arranged on the optical path. Therefore, information can be easily reproduced and recorded on two types of optical information recording media having different standards. In addition, in the case of the objective lens unit, a common antireflection film adapted to the light of the first wavelength and the light of the second wavelength is provided on the optical surface of the first lens unit and the optical surface of the second lens unit. Therefore, the antireflection film can be formed collectively on the first lens portion and the second lens portion. Thereby, although the first lens portion and the second lens portion are adjacent to each other, a highly accurate antireflection film can be formed relatively easily and at low cost.

  According to a specific aspect or aspect of the present invention, the objective lens unit further includes a connecting portion that positions and holds the first lens portion and the second lens portion relative to each other. In this case, the first lens unit and the second lens unit can be supported in an appropriate state while avoiding interference between the first lens unit and the second lens unit when the objective lens unit is manufactured or used. In this case as well, the first lens portion, the connecting portion, and the second lens portion are formed by integral molding.

  In another aspect of the invention, the first wavelength is in the range of 390 to 420 nm. In this case, the first lens unit can reproduce and record information at a high density using near-ultraviolet or blue light. This wavelength range includes wavelengths corresponding to the standards of BD (Blu-ray Disc) and HD-DVD.

  In yet another aspect of the invention, the second wavelength is in the range of 630-680 nm. In this case, the second lens unit can reproduce and record information using red light. This wavelength range includes wavelengths corresponding to the DVD standard.

  In yet another aspect of the invention, the second wavelength is in the range of 670-800 nm. In this case, the second lens unit can reproduce and record information using near-infrared light. This wavelength range includes wavelengths corresponding to the CD standard.

  The objective lens unit can be formed from various resins that can be normally used for optical applications such as lenses. In particular, it is preferable to use a resin containing a polymer having an alicyclic structure, and among them, it is more preferable to use a cyclic olefin resin.

  In addition, an athermal resin can be used as the resin material as described above. The athermal resin is a material in which particles of, for example, 30 nm or less are dispersed in a resin as a base material. The athermal resin has a characteristic that the refractive index change with respect to the temperature change is smaller than that of a resin for normal optical use. Therefore, when the phase structure is formed in the first lens part or the second lens part, the temperature characteristic of the phase structure The improvement effect can be moderated, thereby reducing the deterioration of the wavelength characteristics due to the phase structure, increasing the design freedom of the optical element, and increasing the tolerance of manufacturing error and assembly accuracy. Can do.

  In general, when powder is mixed with a transparent resin material, light scattering occurs and the transmittance decreases, so that it has been difficult to use as an optical material. It has been found that by using fine particles having a diameter of, for example, 30 nm or less, scattering can be substantially prevented. By utilizing such a phenomenon, materials having different temperature characteristics can be mixed macroscopically and the temperature change of the refractive index and the root thermal expansion can be suppressed, and thus A material that has an artificial effect of suppressing temperature characteristics is called an athermal resin. The athermal resin is preferably a material in which fine particles with an average particle diameter of 30 nm or less having a refractive index change rate larger than a refractive index change rate accompanying a temperature change of the resin as a base material are dispersed. In addition, when the sign of the refractive index change rate of the resin that is the base material is negative, the refractive index change rate is large. It includes both of positive refractive index change rates.

  In still another aspect of the present invention, the apparatus further includes a holder that directly or indirectly supports at least one of the first lens unit and the second lens unit. In this case, the first lens unit and the second lens unit can be displaced via the holder, and the objective lens unit can be conveniently driven and handled.

  An optical pickup device according to the present invention reads information from a first optical information recording medium via (a) the objective lens unit described above and (b) a first lens unit, or reads information from the first optical information recording medium. An optical device for writing, reading information on the second optical information recording medium via the second lens unit, or writing information on the second optical information recording medium.

  In the optical pickup device, the objective lens unit described above is used, and information can be easily reproduced and recorded on the first and second optical information recording media having different standards. In addition, the common antireflection film provided in the first lens unit and the second lens unit is relatively simple and low-cost, but has a relatively high performance as a result of the batch film formation. It is possible to reproduce and record information with high accuracy.

  In a specific aspect of the present invention, the optical pickup device further includes a driving device that drives the objective lens unit to displace the first and second lens portions. In this case, switching between the first lens unit and the second lens unit can be performed, and tracking and focusing can be performed for each lens unit.

  In the objective lens unit manufacturing method according to the present invention, the first lens unit used for the first wavelength light and the second lens unit used for the second wavelength light different from the first wavelength are arranged adjacent to each other. A method for manufacturing an integrated objective lens unit, wherein the optical surface of the first lens unit and the optical surface of the second lens unit are compatible with the first wavelength light and the second wavelength light. The film is formed in a lump.

  In the manufacturing method of the objective lens unit, since a common antireflection film suitable for both the optical surface of the first lens unit and the optical surface of the second lens unit can be collectively provided, Although the second lens portion is adjacent, a highly accurate antireflection film can be formed on both of them relatively easily and at low cost. Therefore, when this objective lens unit is incorporated in an optical pickup device, information can be reproduced / recorded with high accuracy on the first and second optical information recording media having different standards.

[First Embodiment]
The objective lens unit according to the first embodiment of the present invention will be described below with reference to the drawings. FIGS. 1A and 1B are a plan view and a side view for explaining the objective lens unit of the first embodiment, and FIG. 1C is a view of a compound objective lens constituting the objective lens unit. It is a side view.

  An objective lens unit 10 shown in FIG. 1A and the like includes a composite objective lens 20 that is an objective optical system arranged to face an optical disc (not shown), and a composite objective lens 20 that supports the composite objective lens 20. And a holder member 30 that is displaced together, and two actuator portions 71 that are made of a coil or the like and are fixed to a side surface of the holder member 30.

  The compound objective lens 20 includes a first lens portion 21 that can collect incident light on an information recording surface provided in an optical disk (not shown) with a relatively small spot diameter, and another type of incident light with a relatively large spot diameter. 2nd lens part 22 which can be condensed on the information recording surface provided in the optical disc of this. Both lens parts 21 and 22 are supported and fixed from the periphery by a connecting part 23, and are substantially along a specific plane (a plane parallel to the paper surface of FIG. 1A) perpendicular to their optical axes OA1 and OA2. Arranged adjacent to each other. The compound objective lens 20 is a single component formed of various materials such as a plastic material, and the first lens portion 21 and the second lens portion 22 are integrated via a connecting portion 23.

  The first lens unit 21 is designed for a first laser beam having a first wavelength λ1, that is, a BD wavelength of 405 nm. That is, as shown in FIG. 1C, when the light beam of the first laser light having a wavelength of 405 nm parallel to the optical axis OA1 is incident along the optical axis OA1 from the first optical surface 21a side of the first lens unit 21, for example. A laser beam is emitted from the second optical surface 21b side of the first lens unit 21, and this laser beam is condensed at a focal position F1 on the optical axis OA1 to form a relatively small condensing spot here. To do.

  The second lens unit 22 is designed for a second laser beam having a second wavelength λ2, that is, a DVD wavelength of 655 nm. That is, as shown in FIG. 1C, when a light beam of the second laser beam having a wavelength of 655 nm is incident from the first optical surface 22a side of the second lens portion 22 along the optical axis OA2, for example, parallel to the optical axis OA2. A laser beam having a wavelength of 655 nm is emitted from the second optical surface 22b side of the second lens unit 22, and this laser beam is condensed at a focal position F2 on the optical axis OA2, and a relatively large light beam is condensed here. A spot is formed.

  Hereinafter, materials for manufacturing the composite objective lens 20 including the first and second lens portions 21 and 22 will be described. That is, the compound objective lens 20 can be formed from a plastic material that can be normally used for optical applications. Examples of the plastic material include transparent resin materials such as acrylic resin, polycarbonate resin, polyolefin resin (ZEONEX resin manufactured by Nippon Zeon Co., Ltd.), and cyclic olefin copolymer resin. As the glass material, a known optical glass, for example, M-BaCD5N (trade name, manufactured by HOYA Co., Ltd.) or the like is used.

  Further, an athermal resin can be used as the material of the composite objective lens 20. The athermal resin is a material in which, for example, particles of 30 nm or less are dispersed in a resin material as a base material. In general, a resin material that serves as a base material has a refractive index that decreases as the temperature rises, but dispersion and mixing of inorganic particles can reduce a change in the refractive index of the entire material.

When an athermal resin is used, the refractive index change, which was conventionally about −1.2 × 10 ⁻⁴ , can be suppressed to an absolute value of less than 8 × 10 ^−5, but the refractive index change is further reduced to an absolute value of 6 By making it less than × 10 ^−5, the performance of the composite objective lens 20 can be further enhanced.

More preferably, the change in refractive index is less than 4 × 10 ⁻⁵ in absolute value. As a material of the composite objective lens 20, a fine particle having a size of 30 nm or less, preferably 20 nm or less, more preferably 10 to 15 nm with respect to a resin material as a base material, and a refractive index that tends to cancel the refractive index change of the base material By using a material in which fine particles made of inorganic particles having characteristics are dispersed, an optical element having no temperature dependency of the refractive index or having a reduced temperature dependency can be provided.

  The fine particles dispersed in the base material are preferably inorganic substances, and more preferably oxides. It is more preferable that the oxide is saturated and does not oxidize any more.

  The inorganic substance is preferable from the viewpoint that the reaction with the resin as a base material, which is a high molecular organic compound, is kept low, and the oxide can prevent deterioration due to actual use such as laser light irradiation. it can. In particular, oxidation of the resin is easily promoted under severe conditions such as high temperature and laser light irradiation. However, such inorganic oxide fine particles can prevent deterioration due to oxidation.

  Of course, an antioxidant may be added to the resin material in order to prevent the resin from being oxidized by other factors.

As a specific example of the athermal resin, for example, niobium oxide (Nb ₂ 0 ₅ ) fine particles are dispersed in an acrylic resin. The volume ratio of the resin as the base material is 80, and the ratio of niobium oxide is about 20, and these are uniformly mixed. Although the fine particles tend to aggregate, a necessary dispersion state can be generated by a technique such as applying a charge to the surface of the particles for dispersion. Instead of niobium oxide, it may be used fine particles of silicon oxide (Si0 _2).

  It is preferable that the mixing / dispersing step of the resin material and the particles as the base material is performed in-line when the composite objective lens 20 is injection molded. In other words, after mixing and dispersing, it is preferable not to be cooled and solidified until the composite objective lens 20 is formed.

  The volume ratio can be appropriately increased or decreased in order to control the rate of change of the refractive index with respect to the temperature, or a plurality of types of fine particles can be blended and dispersed. That is, in the above example, the volume ratio is 80:20, that is, 4: 1, but can be appropriately adjusted between 90; 10 (9: 1) and 60:40 (3: 2). Increasing the amount of fine particles more than 9: 1 increases the effect of suppressing temperature change, and conversely, reducing the amount of fine particles less than 3: 2 is preferable without causing problems in the moldability of the optical element. .

  A common antireflection film is formed on the first and second lens portions 21 and 22 in spite of different target wavelengths. That is, as shown in FIG. 2A, the surface of the lens main body 21d of the first lens unit 21 has both a first laser beam having a wavelength λ1 = 405 nm and a second laser beam having a wavelength λ2 = 655 nm. An antireflection coating (antireflection film) 53 having an antireflection function is provided, and constitutes the first optical surface 21 a of the first lens unit 21. Further, as shown in FIG. 2B, both the first laser beam having the wavelength λ1 = 405 nm and the second laser beam having the wavelength λ2 = 655 nm are also applied to the surface of the lens body 22d of the second lens unit 22. An antireflection coating (antireflection film) 53 having an antireflection function is provided, and constitutes the first optical surface 22 a of the second lens unit 22.

  Note that the antireflection coating 53 is not limited to the first laser beam with a wavelength of 405 nm strictly, but achieves antireflection with respect to a laser beam having a central wavelength in the range of the wavelength λ1 = 390 to 420 nm. it can. In addition, the antireflection coating 53 is not limited to the second laser light with a wavelength of 655 nm strictly, but achieves antireflection with respect to a laser light having a central wavelength in the range of the wavelength λ2 = 630 to 680 nm. it can.

  The above is the description on the first optical surfaces 21a and 22a side of the first and second lens portions 21 and 22, but also on the second optical surfaces 21b and 22b side of the first and second lens portions 21 and 22. Similar film formation can be performed.

  The antireflection coating 53 is formed by laminating a plurality of material layers, and transmits the target laser beams of the first and second wavelengths λ1 and λ2 simultaneously with low loss by the interference action of each layer. When these layers are the first layer, the second layer,..., The fifth layer from the side closer to the surface of the lens body 21d, 22d, the first layer is made of a low refractive index material, and the second layer is made of a high refractive index material. Thus, the third layer is made of a medium refractive index material, the fourth layer is made of a low refractive index material, and the fifth layer is made of a medium refractive index material. The thicknesses of these layers are 81.2 to 113 nm for the first layer, 108.7 to 153 nm for the second layer, 97.6 to 136 nm for the third layer, 21.6 to 30 nm for the fourth layer, The layer is 71.0-99.0 nm.

  Examples of the high refractive index material include cerium oxide, titanium oxide, tantalum oxide, zirconium oxide, aluminum oxide, silicon nitride, and oxygen-containing silicon nitride. Examples of the medium refractive index material include aluminum oxide, yttrium oxide, lead fluoride, and cerium fluoride. Examples of the low refractive index material include silicon oxide, magnesium fluoride, aluminum fluoride, cryolite and the like. In addition, it is good also as comprising the layer which consists of a single component by using these materials by 1 type, and it is good also as comprising the layer which consists of multiple components by using in multiple types. In addition, when a plurality of types of materials are used, there are a case where a mixture is used as a vapor deposition material and a case where different materials are used as a vapor deposition material at the same time.

  The configuration of the antireflection coating 53 described above is merely an example, and the film thickness, the number of layers, and the like can be appropriately changed so that the target wavelength can be transmitted.

  FIG. 3 is a diagram conceptually illustrating an apparatus for forming the antireflection coating 53 shown in FIGS. 2 (a) and 2 (b). The film forming apparatus 90 is a sputtering type film forming apparatus, and includes a substrate holding device 91, a film material injection unit 92, and a control device 93. Of these, the substrate holding device 91 and the film material injection unit 92 are housed in a vacuum container 95 that enables film formation and the like in a low-pressure gas atmosphere.

  Here, the substrate holding device 91 holds a workpiece W that is a base material of the composite objective lens 20 and rotates together with the workpiece W, and a rotation mechanism that rotates the chuck 91a around the rotation axis RA at a desired speed. 91b. The film material injection unit 92 includes three different first to third target units 92a, 92b, and 92c for sequentially laminating a plurality of types of thin films on the upper surface of the workpiece W. These target units 92a, 92b, and 92c are arranged symmetrically about the rotation axis RA of the substrate holding device 91, although it is not clear in the drawing. Each of the target units 92a, 92b, and 92c incorporates different types of targets TAa, TAb, and TAc made of different film forming materials, and generates corresponding film forming material particles. Such film-forming particles are emitted from the targets TAa, TAb, and TAc, fly substantially along the axes P1, P2, and P3 and the periphery thereof, and enter the entire upper surface of the workpiece W relatively uniformly. Each of the targets TAa, TAb, and TAc is formed from a low refractive index material, a high refractive index material, and a medium refractive index material that constitute the antireflection coating 53 described above. When film formation is performed by operating the film material injection unit 92, the substrate holding device 91 rotates the work W fixed to the chuck 91a around the rotation axis RA, and the thin film deposited on the upper surface of the work W Uniform film thickness. In addition, when a low refractive index material, a high refractive index material, and a medium refractive index material are sequentially formed on the upper surface of the workpiece W, the target TAa, TAb, and TAc that operate are rotated while being switched under the control of the control device 93. Film materials having different compositions and refractive indexes are sequentially supplied onto the workpiece W to be processed.

  3 is merely an example, and the antireflection coating 53 shown in FIGS. 2 (a) and 2 (b) can be formed by various processes including a vacuum deposition method, a CVD method, an atmospheric pressure plasma method, and the like. The film can be formed by a film method.

  As is clear from the above description, the objective lens unit 10 of the present embodiment uses the compound objective lens 20 in which the first lens portion 21 and the second lens portion 22 having different specifications are arranged adjacent to each other. As a result, either one of the first and second lens portions 21 and 22 is operatively arranged on the optical path to form spots that conform to the standards on the BD information recording surface and the DVD information recording surface, respectively. Can do. In the case of the objective lens unit 10 of the present embodiment, the laser light having the first wavelength λ1 and the second wavelength are applied to the first optical surface 21a of the first lens unit 21 and the first optical surface 22b of the second lens unit 22. Since a common antireflection film, that is, an antireflection coating 53 that is compatible with the laser beam of λ2, is provided, the antireflection coating 53 can be formed collectively on the first lens portion 21 and the second lens portion 22. it can. Thereby, although the 1st lens part 21 and the 2nd lens part 22 are adjacent, the highly accurate antireflection coating 53 can be formed comparatively easily and at low cost.

  FIG. 4 is a diagram schematically showing a configuration of an optical pickup device incorporating the objective lens unit 10 shown in FIG.

  In this optical pickup device, laser light from each of the semiconductor lasers 61B and 61D is applied to the optical discs DB and DD which are optical information recording media using the shared objective lens unit 10, and is reflected from the respective optical discs DB and DD. The light is finally guided to the photodetectors 67B and 67D through the shared objective lens unit 10. In addition to the above-described semiconductor lasers 61B and 61D and photodetectors 67B and 67D, the optical system including the polarization beam splitters 63B, 63D and 64D, the cylindrical lenses 65B and 65D, the quarter wavelength plate 69, etc. , DD functions as an optical device for recording / reproducing information.

  Here, the first semiconductor laser 61B generates a first laser beam for information reproduction (for example, for BD, wavelength 405 nm) of the first optical disc DB, and this first laser beam is a first operating position (solid line). And a spot corresponding to NA 0.85 is formed on the information recording surface MB. The second semiconductor laser 61D generates a second laser beam for reproducing information from the second optical disk DD (for example, for DVD, wavelength 655 nm), and then the second laser beam is at the second operating position (dashed line). The light is condensed by the second lens portion 22 of the objective lens unit 10 and a spot corresponding to NA 0.65 is formed on the information recording surface MD. On the other hand, the first photodetector 67B detects the information recorded on the first optical disc DB as an optical signal (for example, for BD, wavelength 405 nm), and the second photodetector 67D is recorded on the second optical disc DD. Information is detected as an optical signal (for example, for DVD, wavelength 655 nm). Note that when the light source is switched from the first semiconductor laser 61B to the second semiconductor laser 61D, the objective lens unit 10 is slid by the actuator 73 which is a driving device (the position of the one-dot chain line), Instead, the second lens unit 22 is disposed on the optical path.

  The detailed structure and specific operation of the optical pickup device shown in FIG. 4 will be described below. First, when reproducing the first optical disk DB, the first laser light having the first wavelength λ1 = 405 nm is emitted from the first semiconductor laser 61B, and the emitted light beam becomes a parallel light beam by the collimator 62B. This light beam passes through the polarization beam splitters 63B and 64D and the quarter-wave plate 69, and is then focused on the information recording surface MB of the first optical disc DB by the corresponding first lens unit 21 of the composite objective lens 20. The

  The light beam modulated and reflected by the information bit on the information recording surface MB is again transmitted through the first lens unit 21 and the like, and is incident on the polarization beam splitter 63B. The light beam is reflected and given astigmatism by the cylindrical lens 65B. Then, the light is incident on the first photodetector 67B, and a read signal of information recorded on the first optical disc DB is obtained using the output signal.

  Further, a change in the amount of light due to a change in the shape of the spot and a change in position on the first photodetector 67B is detected to perform focus detection and track detection. Based on this detection, the actuator 73 moves the compound objective lens 20, that is, the first lens unit 21 in the optical axis direction so that the light beam from the first semiconductor laser 61B forms an image on the information recording surface MB of the first optical disc DB. The first lens unit 21 is moved in a direction perpendicular to the optical axis so that the light beam from the first semiconductor laser 61B is imaged on a predetermined track. The actuator 73 for performing focusing and tracking includes a first actuator portion 71 attached to the holder member 30 side of the objective lens unit 10 and a support device 75 that guides the movement of the holder member 30 and the composite objective lens 20. And a second actuator portion 72 attached to the side, and operates under the control of a control device (not shown).

  Next, when reproducing the second optical disk DD, the second laser light having the second wavelength λ2 = 655 nm is emitted from the second semiconductor laser 61D, and the emitted light beam becomes a parallel light beam by the collimator 62D. This light beam passes through the polarization beam splitter 63D, is reflected by the polarization beam splitter 64D, passes through the quarter-wave plate 69, and then the information on the second optical disk DD by the corresponding second lens unit 22 of the composite objective lens 20. It is condensed on the recording surface MD.

  The light beam modulated and reflected by the information bit on the information recording surface MD is transmitted again through the second lens unit 22 and the like, reflected by the polarization beam splitter 64D and incident on the polarization beam splitter 63D, and reflected and reflected here by the cylindrical lens. Astigmatism is given by 65D, is incident on the second photodetector 67D, and a read signal of information recorded on the second optical disk DD is obtained using the output signal.

  Further, as in the case of the first optical disc DB, the spot shape change on the second photodetector 67D and the light quantity change due to the position change are detected to perform focus detection and track detection, which are attached to the objective lens unit 10. The compound objective lens 20, that is, the second lens unit 22 is moved by the actuator 73 for focusing and tracking.

  In the above description, information is reproduced from the optical disks DB and DD. However, information can be recorded on the optical disks DB and DD by adjusting the outputs of the semiconductor lasers 61B and 61D.

[Second Embodiment]
The objective lens unit according to the second embodiment will be described below. The objective lens unit according to the second embodiment is a modification of the objective lens unit according to the first embodiment, and parts not specifically described are the same as those in the first embodiment.

  FIG. 5 is a plan view of the objective lens unit 110 of the present embodiment. In the illustrated objective lens unit 110, the connecting portion 123 of the composite objective lens 120 has a structure that also serves as the holder member 30 shown in FIG. That is, in this case, the actuator portion 71 is directly attached to the composite objective lens 120, the number of parts is reduced, and the bonding step between the composite objective lens and the holder becomes unnecessary, so that the cost can be reduced.

  In addition, as for each lens part 21 and 22 of the compound objective lens 120, a multilayer film that transmits both target wavelengths is collectively formed.

[Third Embodiment]
Hereinafter, the objective lens unit and the optical pickup device according to the third embodiment will be described. Note that the objective lens unit and the like according to the third embodiment are obtained by modifying the objective lens unit and the like of the first embodiment, and parts that are not particularly described are the same as those in the first embodiment.

  FIG. 6 is a diagram schematically showing a configuration of an optical pickup device in which the objective lens unit of the present embodiment is incorporated.

  In this optical pickup device, laser light from each of the semiconductor lasers 61B, 61D, and 61C is applied to the optical discs DB, DD, and DC, which are optical information recording media, using the shared objective lens unit 210, and the optical discs DB, The reflected light from DD and DC is finally guided to the photodetectors 67B, 67D, and 67C through the shared objective lens unit 210. In addition to the above-described semiconductor lasers 61B, 61D, and 61C and photodetectors 67B, 67D, and 67C, an optical system that includes polarizing beam splitters 63B, 63D, 64D, and 64C, cylindrical lenses 65B and 65D, a quarter-wave plate 69, and the like. The system functions as an optical device for recording / reproducing information on / from each optical disc DB, DD, DC.

  Here, the optical device for recording / reproducing information with respect to the first optical disc DB and the second optical disc DD is the same as that of the first embodiment, and hence the description thereof is omitted.

  The third semiconductor laser 61C generates a third laser beam for reproducing information on the third optical disk DC (for example, for CD, wavelength 780 nm), and then the laser beam is emitted from the objective lens unit 210 at the second operating position. A spot condensed by the two lens portions 222 and corresponding to NA 0.53 is formed on the information recording surface MC. On the other hand, the third photodetector 67C detects information recorded on the third optical disc DC as an optical signal (for example, for CD, wavelength 780 nm).

  The detailed structure and specific operation of the optical pickup device shown in FIG. 6 will be described below. When reproducing the third optical disk DC, laser light having a wavelength of, for example, 780 nm is emitted from the third semiconductor laser 61C, and the emitted light beam becomes a parallel light beam by the collimator 62C, passes through the polarization beam splitter 63C, and passes through the polarization beam splitter 64C. After being reflected, it is condensed on the information recording surface MC of the third optical disc DC by the corresponding second lens portion 222 of the composite objective lens 220.

  The light beam modulated and reflected by the information bit on the information recording surface MC is again transmitted through the second lens unit 222 and the like, reflected by the polarization beam splitter 64C, and incident on the polarization beam splitter 63C, and reflected there. Astigmatism is given by the cylindrical lens 65C, is incident on the third photodetector 67C, and a read signal of information recorded on the third optical disc DC is obtained using the output signal.

  Similarly to the case of the first and second optical discs DB and DD, the focus detection and track detection are performed by detecting the change in the light amount due to the spot shape change and position change on the third photodetector 67C, and the actuator. 73, the objective lens unit 210, that is, the second lens unit 222 is moved for focusing and tracking.

  In the above-described objective lens unit 210 for three waves, a common antireflection film is formed on the first and second lens portions 221 and 222. That is, the surface of the first lens unit 21 is provided with an antireflection coating for the first laser beam having the wavelength λ1 = 405 nm, the second laser beam having the wavelength λ2 = 655 nm, and the third laser beam having the wavelength λ3 = 780 nm. Is provided. It should be noted that the anti-reflection coats of both lens portions 221 and 222 do not need to be accurate as described above, and are reflected with respect to laser light having a central wavelength in the range of wavelength λ1 = 390 to 420 nm. And can prevent reflection with respect to laser light having a central wavelength in the range of the wavelength λ2 = 630 to 680 nm, and any one in the range of the wavelength λ3 = 670 to 800 nm. It is possible to prevent reflection with respect to the laser beam having the center wavelength.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications are possible. For example, in the first and third embodiments, information for BD is reproduced and recorded by the first lens units 21 and 221 and information for DVD and CD is reproduced and recorded by the second lens units 22 and 222. However, it is also possible to reproduce / record information on the HD-DVD by the first lens unit 21 and reproduce / record information on the DVD or CD by the second lens unit 22.

  Further, information can be reproduced / recorded on the DVD by the first lens unit 21 and information can be reproduced / recorded on the CD by the second lens unit 22. In this case, the first and second lens portions 21 and 22 are provided with an antireflection coating having an antireflection function in common at wavelengths λ2 = 630 to 680 nm and wavelengths λ3 = 670 to 800 nm, and consequently 630 to 800 nm. Is done.

  In addition, the compound objective lens 20 is not limited to having the two lens parts 21 and 22, and can have three or more lens parts. In this case, the wavelength of all the laser beams targeted by each lens part Thus, an antireflection film having an antireflection function is formed.

(A), (b) is the front view and side view of the objective lens unit of 1st Embodiment, (c) is a side view of a compound objective lens. (A), (b) is a partial expanded sectional view explaining the antireflection film formed in the objective-lens unit shown in FIG. It is a figure explaining the film-forming apparatus of the antireflection film shown in FIG. It is a figure which shows the structure of the optical pick-up apparatus incorporating the objective lens unit shown in FIG. It is a top view which shows the structure of the objective lens unit of 2nd Embodiment. It is a top view which shows the structure of the optical pick-up apparatus of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,110 ... Objective lens unit 20, 120, 220 ... Compound objective lens 21, 221 ... First lens part 22, 222 ... Second lens part 23 ... Connection part 30 ... Holder member 61B, 61D, 61C ... Semiconductor laser, 63B, 63D, 63C, 64D, 64C ... Polarizing beam splitter, 67B, 67D, 67C ... Photo detector, 71, 72 ... Actuator part, 73 ... Actuator, 75 ... Supporting device, DB, DD, DC ... Optical disc, MB, MD, MC ... Information recording surface

Claims (9)

A first lens unit used for light of a first wavelength; and a second lens unit used for light of a second wavelength different from the first wavelength; the first lens unit and the second lens unit; Is an integrated objective lens unit arranged adjacent to each other,
An optical pickup device in which a common antireflection film adapted to the light of the first wavelength and the light of the second wavelength is provided on the optical surface of the first lens unit and the optical surface of the second lens unit. Objective lens unit.   The objective lens unit according to claim 1, further comprising a connecting portion that positions and holds the first lens portion and the second lens portion relative to each other.   The objective lens unit according to claim 1, wherein the first wavelength is in a range of 390 to 420 nm.   The objective lens unit according to any one of claims 1 to 3, wherein the second wavelength is in a range of 630 to 680 nm.   The objective lens unit according to any one of claims 1 to 3, wherein the second wavelength is in a range of 670 to 800 nm.   The objective lens unit according to any one of claims 1 to 5, further comprising a holder that directly or indirectly supports at least one of the first lens unit and the second lens unit. The objective lens unit according to any one of claims 1 to 6,
Read information on the first optical information recording medium through the first lens unit, or write information on the first optical information recording medium, read information on the second optical information recording medium through the second lens unit, Alternatively, an optical pickup device comprising: an optical device that writes information on the second optical information recording medium.   The optical pickup device according to claim 9, further comprising a driving device that drives the objective lens unit to displace the first and second lens portions. A method of manufacturing an integrated objective lens unit in which a first lens unit used for light of a first wavelength and a second lens unit used for light of a second wavelength different from the first wavelength are arranged adjacent to each other. And
A common antireflection film that matches the light of the first wavelength and the light of the second wavelength is collectively formed on the optical surface of the first lens unit and the optical surface of the second lens unit. A manufacturing method of an objective lens unit characterized by the above.

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