JP2005222667A - Objective lens unit, optical head, and optical pickup apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an objective lens unit which reduces damage to an optical disk surface even at the collision while reducing possibility of collision against the optical disk. <P>SOLUTION: A sheet-shaped protecting member 40 is stuck on an annular projection part 24 along its upper end plane 24a. The protecting member 40 is composed of a foamed material in which an elastic material such as rubber and a resin material are foamed, for example, it is fixed on the projection part 24 utilizing adhesive composed of photo-setting resin or the like. Thus, when the protecting member 40 is formed of a foamed material having elasticity, sufficient elasticity deformation quantity can be secured even if it is thinned extremely. Hence, even when collision of an objective lens unit 10 against an optical disk OD is not prevented by a focus servo of the objective lens unit 10, since collision stress can be absorbed sufficiently by the protecting member 40 as a damper, damage to the surface of the optical disk OD is prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an objective lens unit suitable as an objective lens incorporated in an optical head for forming a spot on a recording surface of an optical recording medium for an optical pickup, and further to an optical head and an optical device comprising such an objective lens unit. The present invention relates to a pickup device.

Up to now, various optical pickup devices have been developed and manufactured for the reproduction and recording of information on optical discs such as CDs (Compact Discs), DVDs (Digital Versatile Discs), and BDs (Blue-ray Discs). doing. In an optical head device incorporated in such an optical pickup device, an objective lens is used, and a protective body made of an elastic material is bonded onto a protective protrusion around the objective lens. Thereby, even if the objective lens and the optical disc collide during focus servo, it is possible to prevent not only the objective lens but also the optical disc from being damaged (see, for example, Patent Document 1).
JP 2000-242958 A

  However, in the objective lens as described above, if the amount of the protector protruding from the surface of the objective lens is reduced in order to reduce the possibility of collision during focus servo, the protector becomes extremely thin and absorbs impact stress. Therefore, the damage on the surface of the optical disc at the time of an inevitable collision cannot be ignored. When the protective protrusion is omitted and the protective body is provided, the protective body can be made relatively thick. However, the lens surface of the objective lens is exposed and easily damaged in the assembly process before the protective body is bonded.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an objective lens unit that can reduce damage to the surface of an optical disk even during a collision while reducing the possibility of collision with the optical disk.

  It is another object of the present invention to provide an optical head and an optical pickup device incorporating the above objective lens unit.

  In order to solve the above problems, a first objective lens unit according to the present invention includes: (a) a lens member integrally formed with a lens body and a flange portion that supports the lens body; A protective member made of a porous structure having a minute space, fixed to the flange portion, and protruding toward the object side from the surface of the flange portion.

  In the first objective lens unit, the protective member that protrudes closer to the optical disc, that is, the object side than the surface of the flange portion is made of a porous structure having a large number of minute spaces inside. Even when the amount of protrusion of the protective member relative to the lens surface of the main body is reduced and the possibility of collision with the optical disk is reduced, the protective member has sufficient elasticity. Therefore, even when the objective lens unit collides with an object such as an optical disk, damage to the optical disk surface can be reduced. When the lens member has a protrusion protruding from the flange portion toward the object side and a protective member is formed thereon, the lens surface of the lens body can be protected from immediately after molding by the protrusion.

  The second objective lens unit according to the present invention includes: (a) a lens member integrally formed with a lens body and a flange portion that supports the lens body; and (b) an object-side surface of the flange portion. And (c) a fixing layer for adhering a part of the elastic body of the minute unit to the object side surface of the flange portion.

  In the second objective lens unit, since a part of the minute unit elastic body is adhered to the object side surface of the flange portion by the fixing layer, the protective layer made of the minute unit elastic body and the fixing layer is made extremely thin and soft. be able to. Furthermore, the elastic body of minute units is difficult to peel off by the fixing layer.

  A third objective lens unit according to the present invention includes: (a) a lens body integrally formed with a lens body, a flange portion that supports the lens body, and a protrusion that projects from the flange portion toward the object side; and b) a protective member supported at a position retracted to the non-object side from the top of the protrusion.

  In the third objective lens unit, since the protective member is supported at a position retracted to the non-object side (opposite the object) from the top of the protrusion, the thickness of the protective member in the optical axis direction of the lens member The protection member has sufficient elasticity even when the protrusion amount of the protection member with respect to the lens surface of the lens body is reduced. Therefore, even when the objective lens unit collides with an object such as an optical disk, damage to the optical disk surface can be reduced.

  In a specific aspect of the invention, in the objective lens unit, the protection member is supported by a pedestal formed on the outer peripheral side of the protrusion. When the lens member has a protrusion protruding from the flange portion toward the object side, the lens surface of the lens body can be protected immediately after molding by the protection member.

  In another specific aspect of the invention, the pedestal that supports the protection member is an end surface on the object side of the flange portion adjacent to the outside of the protrusion.

  In another specific aspect of the above invention, the pedestal further supporting the protection member, further comprising a second lens portion joined to the non-object side of the first lens portion on the object side made of the lens member, In the two-lens portion, an enlarged diameter portion having an outer diameter larger than the outer diameter of the first lens portion.

  In another specific aspect of the invention, the protective member covers at least a part of the outer periphery of the flange portion provided on the lens member. In this case, the fixing with the lens member is ensured, and the durability of the protection member can be increased.

  In another specific aspect of the invention, the protection member is supported by being partially embedded in a notch-like portion formed in the protrusion.

  A fourth objective lens unit according to the present invention includes (a) a lens member integrally formed with a lens body and a flange portion supporting the lens body, and (b) formed integrally with the lens member. And a protective means formed by a convex portion protruding from the surface of the flange portion toward the object side from the lens body.

  In the fourth objective lens unit, the protection means formed integrally with the lens member is formed by a convex portion protruding from the surface of the flange portion toward the object side from the lens body. Compared with the case of directly colliding with an object such as an optical disk, damage to the lens body can be reduced, and the impact of the collision can be reduced.

  In another specific aspect of the invention, the protection means is a convex portion formed in an annular shape along the surface of the flange portion. In this case, the protection means can be easily formed on the flange portion.

  In another specific aspect of the invention, the protection means is a plurality of convex portions arranged on the surface of the flange portion. In this case, the impact of a collision with an object such as an optical disk can be reduced by a large number of convex portions.

  In another specific aspect of the invention, the lens member and the convex portion are formed of a material having a hardness lower than that of the substrate surface of the optical recording medium. In this case, damage to the substrate surface of the optical recording medium can be reduced by deformation or wear on the convex side.

  In another specific aspect of the above invention, the flange portion has a protrusion protruding to the object side, and the protection means is formed by a protrusion on the protrusion. In this case, a convex part can be made low, convex part rigidity increases, and the convex part damage by the impact of a collision can be suppressed.

  An optical head according to the present invention is (a) an optical head for forming a spot on a recording surface of an optical recording medium, and (b) includes the above-described objective lens unit that converges an incident light beam as a spot. . In this case, for example, when forming a spot on the recording surface of the optical recording medium, it is possible to use an objective lens unit that has a high density and a high NA but hardly damages the optical recording medium.・ Reproduction can be realized.

  An optical pickup device according to the present invention includes the above-described optical head, and can read information on a recording surface of an optical recording medium or write information on the recording surface. In this case, high density and high NA can be easily achieved without damaging the optical recording medium.

[First Embodiment]
The objective lens unit for an optical head according to the first embodiment of the present invention will be described below.

  FIG. 1 is a side sectional view of the objective lens unit according to the present embodiment. The objective lens unit 10 directly connects the first lens member 20 at the first stage disposed closer to the optical recording medium and the second lens member 30 at the second stage disposed away from the optical recording medium. It has a joined structure. The former first lens member 20 is an optical element made of, for example, plastic or glass that is integrally formed, and is formed around a circular lens body 21 having a pair of lens surfaces 21 a and 21 b and the lens body 21. And an annular flange portion 22. The latter second lens member 30 is also an integrally formed optical element made of plastic or glass, for example, and is formed around a circular lens body 31 having a pair of lens surfaces 31a and 31b. And an annular flange portion 32.

  The first lens member 20 is fixed on the flange portion 32 of the second lens member 30 via the flange portion 22. For this reason, the upper end portion 32 a of the flange portion 32 is adapted to be fitted to the step portion 22 a provided in the flange portion 22. The inner diameter of the annular upper end portion 32a is substantially equal to the outer diameter of the annular protrusion of the step portion 22a. When the objective lens unit 10 is assembled, the upper end portion 32a and the stepped portion 22a are joined using an adhesive or the like.

  The first lens member 20 has a thin annular projection 24 that protrudes on the object side, that is, the optical disc OD side, on the flange portion 22. The upper end surface 24a of the projection 24 is formed so as to be closer to the optical disc OD side than the lens surface 21a of the lens body 21 in the optical axis OA direction, and protects the lens surface 21a when the first lens member 20 is handled. Have a role to play. That is, the first lens member 20 is transported by an appropriate transport device immediately after molding and stocked in a storage place, and is further gripped by the handling mechanism when assembled to the objective lens unit 10. At this time, if the lens surface 21a protrudes outward from the protrusion 24, the possibility of damage to the lens surface 21a increases. However, the protrusion 24 is provided around the lens body 21 as in the present embodiment, and the lens By disposing the surface 21a at a deep position, it is possible to prevent damage in handling the lens surface 21a and the like.

  On the annular protrusion 24, a sheet-like protection member 40 is attached along the upper end surface 24a. The protective member 40 is made of a foamed material obtained by foaming an elastic material such as rubber or a resin material, and is fixed on the protruding portion 24 by using an adhesive made of, for example, a photocurable resin. Thus, when the protective member 40 is formed of a foam of an elastic material, a sufficient amount of elastic deformation can be ensured even if the protective member 40 is made extremely thin. Therefore, even when the collision between the objective lens unit 10 and the optical disk OD cannot be avoided by the focus servo of the objective lens unit 10, the protective member 40 becomes a good damper and can sufficiently absorb the collision stress. It is possible to prevent the surface ODS of the optical disc OD from being damaged.

  The protective member 40 is not limited to the rubber foam as described above, but can be formed of various porous structures having a large number of minute spaces inside. At this time, the minute space is not limited to a closed space such as a bubble, but may be an open space. That is, the protection member 40 can be formed of a spongy material, for example.

[Second Embodiment]
The objective lens unit for an optical head according to the second embodiment will be described below. The objective lens unit of the second embodiment is a modification of the objective lens unit of the first embodiment with respect to the protective member, and the overall structure is the same as the objective lens unit of the first embodiment.

  FIG. 2A is an enlarged cross-sectional view illustrating the formation of the protective member in the second embodiment, and FIG. 2B is an enlarged cross-sectional view illustrating a state after the formation of the protective member. As shown in FIG. 2A, a liquid in which the fine particle elastic body 142 is dispersed in a solvent 141 is applied as a coating layer 143 with a uniform thickness on the annular protrusion 24. Here, the solvent 141 is obtained by dissolving an appropriate adhesive with alcohol or the like, and the fine particle elastic body 142 is a minute unit elastic body made of an elastic material such as rubber or a resin material.

  As shown in FIG. 2B, when the solvent 141 in FIG. 2A is dried, the protective member 140 is formed on the protrusion 24. That is, the fine particle elastic bodies 142 are randomly arranged on the protrusions 24, and each fine particle elastic body 142 is firmly and firmly fixed on the root side by the solidified layer 144 that is a fixed layer formed by drying the solvent 141. The protective member 140 formed in this way can be sufficiently elastically deformed even though it is extremely thin, and can effectively prevent surface damage of the optical disk. Further, by forming the solidified layer 144 from an appropriate material, it is possible to effectively prevent the fine particle elastic body 142 and the protective member 140 itself from being peeled off.

[Third Embodiment]
The objective lens unit for an optical head according to the third embodiment will be described below. The objective lens unit of the third embodiment is a modification of the objective lens unit of the first embodiment with respect to the protection member.

  FIG. 3 is a side sectional view of the objective lens unit of the present embodiment. The objective lens unit 210 has a structure in which the first lens member 220 and the second lens member 30 are directly joined.

  The former first lens member 220 has substantially the same overall structure as that of the first lens member 20 (see FIG. 1) of the first embodiment, but an annular protrusion 224 formed on the flange portion 22. It has a narrow step portion 225 formed in a notch shape on the outer peripheral side. The step portion 225 is a pedestal formed by the end face of the flange portion 22, and an annular protective member 240 is attached along the upper surface. The protective member 240 is made of, for example, an elastic material such as rubber or a foamed material obtained by foaming a resin material, and is fixed to the stepped portion 225 using an adhesive made of, for example, a photocurable resin. In this way, by fixing the protective member 240 to the stepped portion 225 that is retracted to the opposite side (non-object side) of the optical disc from the protrusion 224, the thickness of the protective member 240 in the optical axis OA direction is the thickness of the stepped portion 225. Therefore, the amount of elastic deformation of the protection member 240 can be further increased. Therefore, even if the collision between the objective lens unit 210 and the optical disk cannot be avoided by the focus servo of the objective lens unit 210, the protective member 240 can be a damper to sufficiently absorb the collision stress, and the surface of the optical disk can be absorbed. Damage can be prevented from forming.

  FIG. 4 shows a modification of the objective lens unit 210 of FIG. In the case of this objective lens unit 310, the protective member 340 is larger than that in the case of FIG. 3, and the upper part of the outer periphery of the flange portion 22 is also covered from the periphery. When such a protection member 340 is used, the fixation with the first lens member 220 is ensured, and the durability of the protection member 340 is increased.

In the objective lens units 210 and 310 of the third embodiment described above, the difference between the linear expansion coefficient of the first lens member 220 and the linear expansion coefficient of the protection members 240 and 340 is Δα (cm / cm / ° C.)
−1.0 <Δα <+1.0 (1)
It is better to ensure that the relationship is satisfied. Thereby, even when the temperature environment in which the objective lens units 210 and 310 are used varies greatly, the protection members 240 and 340 can be fixed to the first lens member 220 with good compatibility. That is, since the expansion and contraction of the first lens member 220 and the protection members 240 and 340 are harmonized, it is possible to prevent the protection members 240 and 340 from being easily detached from the first lens member 220 due to temperature changes, and the protection members 240 and 340. However, it is possible to prevent the optical characteristics from being deteriorated by tightening the first lens member 220.

[Fourth Embodiment]
The objective lens unit for an optical head according to the fourth embodiment will be described below. The objective lens unit of the fourth embodiment is a modification of the objective lens unit of the first embodiment with respect to the protection member.

  FIG. 5 is a side sectional view of the objective lens unit of the present embodiment. The objective lens unit 410 has a structure in which the first lens member 420 and the second lens member 30 are directly joined.

  The former first lens member 420 has substantially the same overall structure as the first lens member 20 (see FIG. 1) of the first embodiment, but is formed on an annular protrusion 424 formed on the flange portion 22. A notch-like portion 425 is formed along the center thereof. The notched portion 425 is an annular recess or a plurality of shallow recesses, and the recess is filled with, for example, an elastic photo-curing resin, solidified, and fixed to the notched portion 425 as a protective member 440. Yes. In this way, by fixing the protective member 440 so as to fit into the notched portion 425 formed on the end surface of the protrusion 424, the thickness of the protective member 440 in the optical axis OA direction is increased by the depth of the notched portion 425. Therefore, the elastic deformation amount of the protection member 440 can be increased while suppressing an increase in the projection amount of the protection member 440. Therefore, even when the collision between the objective lens unit 410 and the optical disk cannot be avoided by the focus servo of the objective lens unit 410, the protective member 440 can act as a damper to sufficiently absorb the collision stress, and the surface of the optical disk can be absorbed. Damage can be prevented from forming.

  In the objective lens unit 410 of the fourth embodiment described above, the difference Δα between the linear expansion coefficient of the first lens member 420 and the linear expansion coefficient of the protection member 440 also satisfies the condition of the above-described formula (1). Accordingly, as in the case of the third embodiment, it is possible to prevent the protection member 440 from being easily detached from the first lens member 420 due to a temperature change, and the protection member 440 tightens the first lens member 420 to deteriorate the optical characteristics. Can be prevented.

[Fifth Embodiment]
The objective lens unit for an optical head according to the fifth embodiment will be described below. The objective lens unit of the fifth embodiment is a modification of the objective lens unit of the first embodiment with respect to the protective member.

  FIG. 6 is a side sectional view of the objective lens unit of the present embodiment. The objective lens unit 510 has a structure in which a first lens member 520 and a second lens member 530 are directly joined.

  The former first lens member 520 has substantially the same overall structure as the first lens member 20 (see FIG. 1) of the first embodiment, but an annular protrusion 524 formed on the flange portion 22. The width is narrow.

  The latter second lens member 530 also has substantially the same overall structure as the second lens member 30 of the first embodiment, but an annular rib 532 a is formed on the outer peripheral side surface of the flange portion 532. The rib 532a is an enlarged diameter portion having an outer diameter larger than the outer diameter of the first lens member 520. The outer periphery of the first lens member 520 is covered with a cylindrical protective member 540. The protective member 540 is made of a foam obtained by foaming an elastic resin material such as rubber, for example, and is fixed to the rib 532a using an adhesive made of, for example, a photocurable resin. As described above, by supporting the protective member 540 on the rib 532a that is retracted from the protruding portion 524, the upper end surface of the flange portion 532, and the like, the thickness of the protective member 540 in the optical axis OA direction can be secured. The amount of elastic deformation of the protection member 540 can be increased. Therefore, even if the collision between the objective lens unit 510 and the optical disk cannot be avoided by the focus servo of the objective lens unit 510, the protective member 540 can be a damper to sufficiently absorb the collision stress and Damage can be prevented from forming.

  In the objective lens unit 510 of the fifth embodiment described above, the difference Δα between the linear expansion coefficient of the first lens member 520 and the linear expansion coefficient of the protection member 540 also satisfies the condition of the above formula (1). good. Accordingly, as in the case of the third embodiment, it is possible to prevent the protection member 540 from being easily detached from the second lens member 530 due to a temperature change, and the protection member 540 removes the first lens member 520 and the second lens member 530. It is possible to prevent the optical characteristics from being deteriorated by tightening.

[Sixth Embodiment]
The objective lens unit for an optical head according to the sixth embodiment will be described below. The objective lens unit of the sixth embodiment is a modification of the objective lens unit of the first embodiment with respect to the protective member.

  FIG. 7A is a side sectional view of the objective lens unit of the present embodiment, and FIG. 7B is a plan view of the objective lens unit. The first lens member 620 on the optical disk OD side of the objective lens unit 610 has substantially the same overall structure as the first lens member 20 (see FIG. 1) of the first embodiment, but on the flange portion 22. The width of the formed annular protrusion 624 is narrow. An annular rib 624b is formed at the center of the upper end surface 624a of the protrusion 624 along the upper end surface 624a. The annular rib 624b is a convex portion that protrudes toward the optical disc OD, and functions as a protective means that softens the impact when the optical disc OD collides with the objective lens unit 610.

  The annular rib 624b is integrally formed with the lens body 21 and the flange portion 22 when the first lens member 620 is injection molded. Therefore, the dimensional variation of the protective member and the combination variation of the protective member and the lens member can be excluded, so that the annular rib 624b serving also as the protective member can be made thicker, that is, increased by at least the variation. Such an objective lens unit 610 is made of a material softer than the optical disc OD. That is, since the hardness of the material of the annular rib 624b is smaller than the hardness of the material of the optical disc OD, the material is easily deformed or hardly damaged. Therefore, even when the collision between the objective lens unit 610 and the optical disk OD cannot be avoided by the focus servo of the objective lens unit 610, the collision stress can be sufficiently absorbed by the annular rib 624b being deformed and worn. It is possible to prevent damage from being formed on the surface of the optical disc OD.

  FIG. 8 shows a modification of the objective lens unit 610 shown in FIG. In the case of the objective lens unit 710, a large number of convex portions 724b are randomly or regularly formed along the upper end surface 624a of the protrusion 624. These convex portions 724b are convex portions projecting toward the optical disc OD, and function as protective means for reducing the impact when the optical disc OD collides with the objective lens unit 710. A large number of convex portions 724 b are integrally formed with the lens body 21 and the flange portion 22 when the first lens member 720 is injection-molded. Therefore, since the dimensional variation of the protective member and the combination variation of the protective member and the lens member can be excluded, the convex portion 724b that also serves as the protective member can be thickened, that is, increased by at least the variation. The objective lens unit 710 is also made of a material softer than the optical disk OD, and the hardness of the many convex portions 724b is smaller than the hardness of the optical disk OD, so that the optical disk OD is hardly damaged.

[Seventh Embodiment]
The objective lens unit for an optical head according to the seventh embodiment will be described below. The objective lens unit of the seventh embodiment is a modification of the objective lens unit of the first embodiment with respect to the protective member.

  FIG. 9A is a side sectional view of the objective lens unit of the present embodiment, and FIG. 9B is a plan view of the objective lens unit. The first lens member 820 on the optical disc OD side of the objective lens unit 810 has substantially the same overall structure as the first lens member 20 (see FIG. 1) of the first embodiment, but on the flange portion 22. The protrusion 24 is not formed. An annular rib 824b is formed at the center of the upper end surface 822c of the flange portion 22 along the upper end surface 822c. The annular rib 824b is a convex portion that protrudes from the top of the optical surface of the first lens member 820 toward the optical disc OD, and functions as a protective means that softens the impact when the optical disc OD collides with the objective lens unit 810.

  The annular rib 824b is integrally formed with the lens body 21 and the flange portion 22 when the first lens member 820 is injection molded. Therefore, since the dimensional variation of the protective member and the combination variation of the protective member and the lens member can be excluded, the annular rib 824b serving also as the protective member can be made thicker, that is, higher than the variation. Furthermore, such an objective lens unit 810 is formed of a material softer than the optical disc OD. That is, since the hardness of the material of the annular rib 824b is smaller than the hardness of the material of the optical disk OD, the material is easily deformed or hardly damaged. Therefore, even when the collision between the objective lens unit 810 and the optical disk OD cannot be avoided by the focus servo of the objective lens unit 810, the annular rib 824b can sufficiently absorb the collision stress due to deformation and wear. It is possible to prevent damage from being formed on the surface of the optical disc OD.

  FIG. 10 shows a modification of the objective lens unit 810 shown in FIG. In the case of the objective lens unit 910, a large number of convex portions 924b are randomly or regularly formed on the upper end surface 922c of the flange portion 22 along the upper end surface 922c. These convex portions 924b are convex portions projecting toward the optical disc OD, and function as protective means for reducing the impact when the optical disc OD collides with the objective lens unit 910. A large number of convex portions 924 b are integrally formed with the lens main body 21 and the flange portion 22 when the first lens member 920 is injection molded. Therefore, since the dimensional variation of the protective member and the combination variation of the protective member and the lens member can be excluded, the convex portion 924b that also serves as the protective member can be thickened, that is, increased by at least the variation. The objective lens unit 910 is also made of a softer material than the optical disk OD, and the hardness of the many convex portions 924b is smaller than the hardness of the optical disk OD, so that the optical disk OD is hardly damaged.

[Eighth Embodiment]
FIG. 11 schematically shows a configuration of an optical pickup device in which the objective lens units 10, 110, 210, 310, 410, 510, 610, 710, 810, and 910 according to the first to seventh embodiments are incorporated in an optical head. FIG.

  This optical pickup device includes a semiconductor laser 62 that emits a light beam with a wavelength of 405 nm for information reproduction of the first optical disk 61 and a semiconductor laser 66 that emits a light beam with a wavelength of 655 nm for information reproduction of the second optical disk 65. In other words, laser beams having different wavelengths can be emitted. Laser light from both the semiconductor lasers 62 and 66 is obtained by using the objective lens unit (specifically, the objective lens units 10 to 910 according to the first to sixth embodiments) incorporated in the optical head 1000. The reflected light from the optical discs 61 and 65 is collected using the objective lens units 10 to 910.

  First, when reproducing the first optical disc 61, a beam is emitted from the first semiconductor laser 62, and the emitted light beam is transmitted through the beam splitter 71, and the polarized beam splitter 72, the collimator 73, and the quarter wavelength plate 74 are passed through. The light passes through and becomes a circularly polarized parallel light beam. This light beam is focused by a diaphragm 76 and is focused on the information recording surface 61b by the objective lens units 10 to 910 via the transparent substrate 61a of the first optical disk 61.

  The light beam modulated and reflected by the information bit on the information recording surface 61b is transmitted again through the lens units 10 to 910, the diaphragm 76, the quarter wavelength plate 74, and the collimator 73 and enters the polarization beam splitter 72, where Reflected and given astigmatism by the cylindrical lenses 78 and 78a, is incident on the photodetector 79, and an output signal is used to obtain a read signal of information recorded on the first optical disc 61.

  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 photodetector 79 is detected to perform focus detection and track detection. Based on this detection, the two-dimensional actuator 81 incorporated in the optical head 1000 irradiates the objective lens units 10 to 910 so that the light beam from the first semiconductor laser 62 forms an image on the information recording surface 61 b of the first optical disk 61. While moving in the axial direction, the objective lens units 10 to 910 are moved in a direction perpendicular to the optical axis so that the light flux from the semiconductor laser 62 is imaged on a predetermined track.

  On the other hand, when reproducing the second optical disk 65, a beam is emitted from the second semiconductor laser 66, and the emitted light beam is reflected by the beam splitter 71, which is a light synthesizing unit, and is combined with the light beam from the first semiconductor laser 62. Similarly, the light passes through the polarization beam splitter 72, the collimator 73, the quarter wavelength plate 74, the diaphragm 76, and the objective lens units 10 to 910, and is condensed on the information recording surface 65b via the transparent substrate 65a of the second optical disk 65. The

  The light beam modulated and reflected by the information bit on the information recording surface 65b is transmitted again through the objective lens units 10 to 910, the diaphragm 76, the quarter wavelength plate 74, the collimator 73, the polarization beam splitter 72, and the cylindrical lens 78. The light is incident on the detector 79, and a read signal of information recorded on the second optical disc 65 is obtained using the output information.

  Further, as in the case of the first optical disc 61, a two-dimensional built-in optical head 1000 is detected by detecting a change in the amount of light due to a change in the shape of the spot on the photodetector 79 and a change in position to detect the focus. The actuator 81 moves the objective lens units 10 to 910 for focusing and tracking.

  In the optical pickup device of the eighth embodiment, the objective lens units 10 to 910 of the first to seventh embodiments are incorporated, and the objective lens units 10 to 910 have a small amount of protrusion on the optical discs 61 and 65 side. Nevertheless, the protective members 40, 140, 240, 340, 440, 540 having a large elastic deformation amount, the annular rib 624b, and the convex portion 724b are formed. Therefore, not only can the objective lens units 10 to 910 be made to have a high NA but also to cope with high density and high speed of information that shortens the work distance, the objective lens units 10 to 910 and the optical discs 61 and 65 are inevitable. The occurrence of damage to the objective lens units 10 to 910 and the optical discs 61 and 65 can be prevented in the event of a collision.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments. For example, the shapes of the protective members 40, 140, 240, 340, 440, 540, the annular rib 624b, and the like are not limited to the annular shape, and may be divided into a plurality along the flange.

It is a side sectional view of the objective lens unit concerning a 1st embodiment. (A) is an expanded sectional view explaining formation of the protection member in 2nd Embodiment, (b) is an expanded sectional view explaining the state after formation of a protection member. It is a sectional side view of the objective lens unit concerning a 3rd embodiment. It is a sectional side view explaining the modification of the objective lens unit of FIG. It is side sectional drawing of the objective lens unit which concerns on 4th Embodiment. It is side sectional drawing of the objective lens unit which concerns on 5th Embodiment. (A) is a sectional side view of the objective lens unit according to the sixth embodiment, and (b) is a plan view of the objective lens unit. It is a top view explaining the modification of the objective lens unit of FIG. (A) is a sectional side view of the objective lens unit according to the seventh embodiment, and (b) is a plan view of the objective lens unit. It is a top view explaining the modification of the objective lens unit of FIG. It is a block diagram explaining the structure of the optical pick-up apparatus of 8th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Objective lens unit, 20 ... 1st lens member, 21 ... Lens main body, 22 ... Flange part, 24 ... Projection part, 30 ... 2nd lens member, 31 ... Lens main body, 32 ... Flange part, 40 ... Protection member

Claims (15)

A lens member integrally formed with a lens body and a flange portion supporting the lens body;
An objective lens unit comprising a protective member made of a porous structure having a large number of minute spaces inside and fixed to the flange portion and protruding toward the object side from the surface of the flange portion. A lens member integrally formed with a lens body and a flange portion supporting the lens body;
An elastic body of minute units arranged dispersed on the object side surface of the flange portion;
An objective lens unit comprising: a fixing layer that adheres a part of the elastic body of the minute unit to the object side surface of the flange portion. A lens body integrally formed with a lens body, a flange portion supporting the lens body, and a protrusion protruding from the flange portion toward the object side;
A protective member supported at a position retracted to the non-object side from the top of the protrusion,
An objective lens unit comprising:   The objective lens unit according to claim 3, wherein the protection member is supported by a pedestal formed on an outer peripheral side of the protrusion.   The objective lens unit according to claim 4, wherein the pedestal that supports the protection member is an object-side end surface of the flange portion adjacent to the outside of the protrusion.   A second lens portion that is joined to the non-object side of the first lens portion on the object side made of the lens member; and the pedestal that supports the protection member is formed on the second lens portion with respect to the first lens portion. The objective lens unit according to claim 4, wherein the objective lens unit is an enlarged diameter portion having an outer diameter larger than the outer diameter.   The objective lens unit according to claim 4, wherein the protection member covers at least a part of an outer periphery of the flange portion provided on the lens member.   The objective lens unit according to claim 3, wherein the protection member is partially embedded and supported in a notch-like portion formed in the protrusion. A lens member integrally formed with a lens body and a flange portion supporting the lens body;
Protective means formed integrally with the lens member and formed by a convex portion protruding from the surface of the flange portion toward the object side from the lens body,
An objective lens unit comprising:   The objective lens unit according to claim 9, wherein the protection means is a convex portion formed in an annular shape along a surface of the flange portion.   The objective lens unit according to claim 9, wherein the protection means is a plurality of convex portions arranged on a surface of the flange portion.   The objective lens unit according to any one of claims 9 to 11, wherein the lens member and the convex portion are formed of a material having a hardness lower than that of the substrate surface of the optical recording medium.   10. The objective lens unit according to claim 9, wherein the flange portion has a protruding portion that protrudes toward the object side, and the protection means is formed as a protruding portion on the protruding portion. An optical head for forming spots on the recording surface of an optical recording medium,
An optical head comprising the objective lens unit according to any one of claims 1 to 13, which converges an incident light beam as a spot. 15. An optical pickup device comprising the optical head according to claim 14 and capable of reading information on a recording surface of an optical recording medium or writing information on the recording surface.

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