JP2010040117A - Optical element for pickup in optical recording/reading - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attach an optical pickup lens where a result of wavefront aberration measurement as one of performance evaluations of the optical pickup lens is good so as to easily obtain a good optical spot for an optical head, when the optical pickup lens used for the optical head and the optical disk device. <P>SOLUTION: In an optical pickup lens used for an optical head and an optical disk device, the lens surface of the incident surface side of a laser, the optical pick of the flash surface outside the lens surface, and a spot which becomes an attaching surface of the optical pickup lens are formed by the same mold. The attaching surface is set as a mirror surface. In addition, the lens surface of a disk surface side and a mirror surface formed on the flash surface outside the lens surface are formed by the same mold. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical pickup lens that exists in an optical path used in an optical system that performs recording or reproduction with respect to an optical disc, and an optical head and an optical disc apparatus that mount the optical pickup lens.

  Reading information from the optical disk is achieved by forming light spots on the optical disk by using the objective lens and the light emitted from the light source of the optical disk device through a transparent part such as a wave plate and a collimator. Information on the optical disc can be read. In recent years, the recording capacity of optical discs continues to increase, the recording density per unit area also continues to increase, and Blu-ray discs (BD) have been developed. The recording capacity of the Blu-ray Disc (BD) is 23 GB, which is five times the DVD disc capacity 4.7 GB, even though it is the same 12 cm disc as the DVD. The difference between a BD disc and a DVD disc is easier to see from the difference in the disc structure. The track pitch is 0.74 μm for DVD and BD is as narrow as 0.32 μm, and the minimum pit length is also as short as 0.149 μm for DVD of 0.400 μm. However, in order to accurately read and write such extremely narrow and short pits, it is necessary to use light with a wavelength of 405 nm in the BD, and the optical pickup lens used is also NA. It is necessary to use a high NA of 0.85 or more.

  In a DVD optical pickup lens, a technique of freely adjusting the edge thickness is often used in adjusting the distance between the apex on the disk surface side and the disk surface, that is, the working distance. In other words, this is a method in which the surface diameter of the optical pickup lens and the edge surface from the outer side to the outer diameter are manufactured with different molds. The edge thickness here refers to the thickness of the portion sandwiched between the portion from the lens surface on the laser incident surface side to the outer diameter and the portion from the lens surface to the outer diameter on the disk surface. .

  The advantage of this method is that the edge thickness can be determined freely with another mold without moving the center thickness which greatly affects the performance of the optical pickup lens. However, there are drawbacks to this approach. The optical pickup lens measures wavefront aberration in examining its performance. Usually, this wavefront aberration is measured in a state in which no inclination of the edge surface occurs with respect to the edge surface on the laser incident surface side. As a method of measuring without tilting the edge, irradiate the mirror surface on the laser incident surface side with a laser for measuring wavefront aberration, and adjust the lens tilt so that the interference fringes on the mirror surface are minimized. The way to do is taken.

  Wavefront aberration measurement is performed in a state where no tilt of the edge surface is generated by the above method, and the optical pickup lens is attached based on the obtained measurement result of the wavefront aberration. Specifically, the wavefront aberration component is confirmed, and if the wavefront aberration component that is focused on in a timely manner is large, the optical pickup lens cannot be used, or it is attached in consideration of the direction of occurrence of the wavefront aberration component. Will go and use. For example, in terms of the mounting angle of the optical pickup lens, the third-order coma aberration may be confirmed, the amount and direction of the confirmation may be confirmed, and the optical head may be attached to the optical head.

  However, since the edge surface on the laser incident surface side, which is a measurement standard for wavefront aberration, is an attachment surface, it cannot be confirmed whether the optical pickup lens is attached with a normal inclination. Therefore, a mirror surface is provided on the edge surface on the opposite side of the laser incident surface side from the lens surface diameter on the disk surface side to the outer diameter, and the optical pickup lens is tilted by applying a mounting laser beam to it. Control the installation. However, there are significant drawbacks to this approach. In other words, although the wavefront aberration is measured with reference to the edge surface on the laser incident surface side, the outer diameter is different from the lens surface diameter on the disk surface side, which is completely different from the edge surface on the laser incident surface side. It is that it is mounted on the mirror surface standard of the edge surface.

  Referring to the optical pickup lens 1 as shown in FIG. 1, the lens surface 2 and the mirror surface 6 of the optical pickup lens on the laser incident surface side are made of the same mold. The end portion of the lens surface and the mirror surface are connected by an appropriate curve, but the mirror surface start position 4 and the mirror surface end position 5 are smooth and substantially perpendicular to the optical axis 9. As described above with this mirror surface, the laser 10 for measuring the wavefront aberration is irradiated, and the lens tilt adjustment is performed so that the interference fringes on the mirror surface are minimized.

  In this state, wavefront aberration measurement is performed to determine whether or not the optical pickup lens can be used. However, since the lens mounting surface 7 is actually made of a mold different from the laser incident surface 2 and the mirror surface 6, Even if it is attached to the optical head as it is, it cannot be said that the result of aberration measurement is reflected. Further, in FIG. 1, the lens surface 3 on the disk surface side and the mirror surface 8 on the disk surface side are manufactured by separate molds. As described above, the mirror surface 8 on the disk surface side is used to attach the optical pickup lens to the optical head while irradiating the mounting laser beam and observing the inclination of the optical pickup lens. Since the lens surface 3 on the side and the mirror surface 8 are separate dies, it is difficult to directly reflect in the mounting reflecting the result of the wavefront aberration measurement measured by the previous method.

  As another example, an optical pickup lens as shown in FIG. 2 is also conceivable. The mirror surface 16 of the laser incident surface is made the same as the optical head mounting surface outside the lens surface 12 of the laser incident surface. In this method, when measuring the wavefront aberration, the laser 18 for measuring the wavefront aberration is irradiated and the lens tilt adjustment is performed so that the interference fringes on the mirror surface are minimized. The result of the wavefront aberration obtained by the measurement and the state of the optical pickup lens after mounting match, and it appears that the measurement result is reflected. However, this method still has a problem of how to make the mirror surface 16 on the laser incident surface side a mirror surface.

  If the mirror is attached to the optical head, ideally, the mirror surface 201 is formed as a surface perpendicular to the optical axis 20 of the optical pickup lens as shown in FIG. The mirror surface 22 and the mirror surface 24 must be formed so as to be planes symmetrical with respect to the optical axis 21 and the optical axis 23. Here, the line symmetry with respect to the optical axis is described because the mirror surface 22 and the mirror surface 23 have inclinations with respect to the optical axis such as θ1 and θ2, respectively.

  On the other hand, in order to make this mirror surface 201 into a mirror surface, the part which becomes the mirror surface of the mold is polished so as to be as flat as possible. Thus, the mirror surface 26 has a non-uniform angle such as θ3 or θ4 with respect to the circumference. Naturally, when the lens is mounted on the mirror surface of the optical pickup lens as shown in FIG. 6, in this case, the mounting is performed with an appropriate angle such as the angle θ3 or θ4 with respect to the optical axis. An optical pickup lens having such an angle means that there is a deviation from the optical axis, and the coma aberration that originally occurs due to the tilt of the optical pickup lens is eliminated while this deviation occurs. There is a need. Since it is not assumed that the optical pickup lens has such an inclination when the optical pickup lens is designed, if the lens performance is improved while the inclination is generated in actual manufacturing, the optical pickup lens is distorted. It will be.

  In DVD, NA is 0.60 and wavelength is 650 nm. On the other hand, in BD, NA is 0.85 and wavelength is 405 nm. Therefore, wavefront aberration is greatly increased in sensitivity in terms of λrms. ing. In other words, the method of manufacturing the surface diameter of the optical pickup lens in the above-described method and the edge surface from the outer side to the outer diameter with different molds is used in BD to attach the optical pickup lens normally. It can be said that it is difficult for it.

In a high NA optical pickup lens such as a BD, a method for easily mounting the optical pickup lens so that the optical axis of the optical pickup lens is aligned with the optical axis direction of the reading or writing laser. It showed to the 8th aspect from the 1st aspect of this invention.
However, the mirror surface described in the first to eighth aspects of the present invention has a smoothness equal to or less than the degree at which four interference fringes are seen at the measurement wavelength. Furthermore, it is desirable that the degree of smoothness is less than the level at which two are seen. That is, in order for two interference fringes to be seen, the height difference between the interference fringes needs to be λ / 2. For example, when measuring at a wavelength of 405 nm, the height difference of 405/2 = 202.5 nm A mirror surface with undulations.

  Further, since molding burrs are generated at the joints of different molds, it is possible to easily determine the joints of the molds.

  A first embodiment of the present invention will be described with reference to FIG. FIG. 7 is a cross-sectional view taken along a plane parallel to the optical axis of the optical pickup lens. The optical pickup lens 27 has a lens surface 28 on the laser incident surface side and a mirror surface 38 provided on the edge outside the lens surface. These lens surface 28 and mirror surface 38 are made of the same mold. The start position 29 of the lens surface 28 and the mirror surface 38 may be connected by an arbitrary curved surface, but the start position 30 and the end position 31 of the mirror surface 38 are mirror surfaces and are smooth. The lens surface 32 on the disk surface side and the mirror surface 37 provided on the outer edge are made of different molds. The optical pickup lens 27 is attached to the optical head by the mirror surface 36 on the laser incident surface side.

  In the first aspect of the present invention, the mirror surface formed toward the outer diameter from the lens surface on the laser incident surface side and the lens surface on the laser incident surface side are manufactured by a single mold. It also shows the production of the characteristic optical pickup lens. This is because the mirror surface formed toward the outer diameter from the lens surface on the laser incident surface side and the lens surface on the laser incident surface side are produced by a single mold, so the lens on the laser incident surface side. The inclination of the mirror surface formed from the surface toward the outer diameter and the lens surface on the laser incident surface side can be matched.

  This also means the following: When measuring wavefront aberration, which is one of the lens performances, when the wavefront aberration is measured in parallel with a mirror surface formed outside the lens surface on the laser incident surface side, that is, with no tilt, the laser Since the mirror surface formed outside the lens surface on the incident surface side is attached to the optical head, the result of the wavefront aberration measurement can be easily reflected in the optical head simply by attaching the result obtained by the wavefront aberration measurement to the optical head. Become. Here, by providing a mirror surface on the outer diameter part from the outside of the lens surface on the disk surface side, by applying a laser to adjust the tilt angle of the pickup lens to this mirror surface, the inclination of the lens is grasped, The tilt of the lens may be adjusted.

  Here, the importance of simultaneously producing the lens surface and the mirror surface of the edge surface provided outside the lens surface will be additionally described. Since the lens surface is point-symmetric with respect to the center of the lens, it is manufactured by fixing a tool for cutting a mold and rotating the mold in cutting and grinding. When the production of the lens surface is completed and a mirror surface of the edge surface provided outside the lens surface is produced as it is, this mirror surface is also point-symmetric with respect to the lens center. Here, after the lens surface is finished, an arbitrary curved surface may be connected to produce a mirror surface.

  When manufactured by this method, three types of lens cross-sections as shown in FIGS. FIG. 9 is an example in which the mirror surface 50 of the edge surface provided outside the lens surface on the laser incident surface side is perpendicular to the optical axis 49 of the optical pickup lens. In FIG. 10, the mirror surface 52 of the edge surface provided outside the lens surface on the laser incident surface side and the optical axis 51 of the optical pickup lens have an angle of θ5, that is, the mirror surface 52 of the edge surface is in relation to the optical axis 51. This is an example of a line-symmetric umbrella-like structure. In FIG. 11, the edge-side mirror surface 54 provided outside the lens surface on the laser incident surface side and the optical axis 53 of the optical pickup lens have an angle of θ 6, that is, the edge-side mirror surface 54 is relative to the optical axis 53. This is an example of a symmetric mortar structure.

  In FIGS. 9 and 10, if the lens mounting surface of the optical head is flat, the lens of the optical head can be simply mounted on the lens mounting surface of the optical head with the mirror surface of the edge provided outside the lens surface. The inclination of the mounting surface and the mirror surface of the edge surface provided outside the lens surface can be matched. That is, the measurement result of the wavefront aberration of the optical pickup lens can be easily reflected on the optical head.

  On the other hand, when the lens surface and the edge surface provided outside the lens surface are produced by separate molds, they are provided outside the lens optical axis 55 and the lens surface as shown in FIG. The mirror surface 56 of the edge surface has various inclinations within the mirror surface circumference like the angles of θ7 and θ8. As described above with respect to the problem of the lens having such a form, when the mirror surface has such an angle, or when the lens is mounted on the mirror surface, in this case, the angles θ7 and θ8 are set with respect to the optical axis 55. It will be installed. An optical pickup lens having such an angle means that there is a deviation from the optical axis, and the coma aberration that originally occurs due to the tilt of the optical pickup lens is eliminated while this deviation occurs. There is a need. In designing an optical pickup lens, it is not assumed that it has such a tilt. Therefore, improving the lens performance while generating this tilt in actual manufacturing causes distortion in the optical pickup lens. Become.

  Now, in FIG. 7, by making both the lens surface 28 of the laser incident surface and the outer diameter part from the lens surface 32 on the disk surface side mirror surfaces, it is easy to confirm the positional relationship between the mirror surfaces 36 and 37. It means that it will be possible. That is, measurement using a laser displacement meter or the like can be performed from the mirror surface 37 on the disk surface side. If you want to improve the performance of the optical head such as a light spot when the mirror surface 36 on the laser incident surface side is attached to the optical head by changing the mounting, you can attach an optical pickup lens and fine-tune the angle on the disk side. By irradiating 37 with a laser for tilt adjustment, the mounting angle of the optical pickup lens can be grasped. However, in the first aspect of the present invention, since the lens surface 32 on the disk surface side and the mirror surface 37 provided on the outer side thereof are different molds, there are misalignments of the respective molds in the molding, Since it is not constant, it is only a guideline to grasp the mounting angle of the pickup lens.

  According to a second aspect of the present invention, in the first aspect of the present invention, the mirror surface formed toward the outer diameter from the lens surface on the disk surface side and the lens surface on the disk surface side are produced by a single mold. It shows that an optical pickup lens characterized by the above is manufactured. This will be described with reference to FIG.

  FIG. 8 is a cross-sectional view taken along a plane parallel to the optical axis of the optical pickup lens. The optical pickup lens 38 has a lens surface 39 on the laser incident surface side and a mirror surface 47 provided on the edge outside the lens surface. These lens surface 39 and mirror surface 47 are made of the same mold. The start position 41 of the lens surface 39 and the mirror surface 47 may be connected by an arbitrary curved surface, but the start position 41 and the end position 42 of the mirror surface 47 are mirror surfaces and are smooth. The lens surface 43 on the disk surface side and the mirror surface 48 provided on the outer edge are made of the same mold. The start position 45 of the lens surface 43 and the mirror surface 48 may be connected by an arbitrary curved surface, but the start position 45 and the end position 46 of the mirror surface 48 are mirror surfaces and are smooth. The optical pickup lens 38 is attached to the optical head by the mirror surface 47 on the laser incident surface side.

  In FIG. 8, since the mirror surface formed toward the outer diameter from the lens surface on the disk side and the lens surface on the disk surface side are manufactured by one mold, the lens surface on the disk side is directed toward the outer diameter. This means that the inclination of the formed mirror surface and the lens surface on the disk side can be matched, and the inclination of the optical pickup lens can be easily adjusted when mounting to a more accurate optical head. In particular, the following effectiveness is manifested. In general, the optical pickup lens is attached by grasping the tilt of the lens by irradiating the mirror surface formed toward the outer diameter from the lens surface on the disc surface side, and relying on it for the optical pickup. The lens is attached to the optical head.

  That is, if it is attached to the optical head relying on a mirror surface formed outside the lens surface on the disk side, it can be matched with the inclination of the lens surface on the disk side, and according to the second aspect of the present invention, When wavefront aberration, which is one of the lens performances, is efficiently performed on the optical pickup lens, the result of wavefront aberration can be easily reflected by using this mirror surface.

  The optical pickup lens manufactured according to the second aspect of the present invention measures the wavefront aberration when the wavefront aberration is measured with the mirror surface formed on the outer diameter of the lens surface on the laser incident surface side having no inclination. After this, when this optical pickup lens was attached to the optical head without doing anything, the wavefront aberration was measured with the mirror surface formed at the outer diameter from the lens surface on the laser incident surface side having no inclination. The optical pickup lens is attached with the result reflected. Here, since the optical pickup lens surface on the disk surface side and the mirror surface formed from the outside to the outer diameter are made of the same mold, light is irradiated by irradiating this part with a lens tilt adjustment laser. It becomes easy to grasp the inclination of the pickup lens. Unlike the first aspect of the present invention, since the lens surface and the mirror surface on the disk surface side are made of the same mold, the positional relationship between the lens surface on the disk surface side and the mirror surface is changed by molding. The inclination of the optical pickup lens can be grasped.

  A method for grasping the lens tilt will be described with reference to FIG. A laser 84 is irradiated from a lens tilt adjusting laser device 83 onto a mirror surface formed with an outer diameter from the lens surface on the laser incident surface side. At this time, the lens tilt adjusting laser device 83 is installed in a horizontal relationship with the optical axis 85 and the laser 86 incident on the optical pickup. In this state, the optical pickup lens is attached to the optical head while observing the state of the laser 84 irradiated to the disk surface side. This makes it possible to adjust the tilt of the optical pickup lens by the mirror surface formed on the optical pickup lens on the disk surface side, rather than simply attaching the mirror surface of the optical pickup lens formed on the laser surface side to the optical head. Thus, the tilt adjustment of the optical pickup lens can be facilitated most effectively when attached to the optical head.

  Here, as in the first aspect of the present invention, the importance of simultaneously producing the lens surface and the mirror surface of the edge surface provided outside the lens surface will be additionally described. Since the lens surface is axisymmetric with respect to the optical axis, it is manufactured by fixing a tool for cutting a mold and rotating the mold in cutting or grinding. When the production of the lens surface is completed and a mirror surface of the edge surface provided outside the lens surface is produced as it is, this mirror surface is also axisymmetric with respect to the optical axis. That is, when manufactured by this method, three types of lens cross-sections as shown in FIGS. 9 and 10, as described in the first embodiment of the present invention, if the lens mounting surface of the optical head is flat, the edge surface provided outside the lens surface of the laser incident surface. By simply placing the mirror surface on the lens mounting surface of the optical head, the inclination of the lens mounting surface of the optical head can be matched with the mirror surface of the edge surface provided outside the lens surface, and the lens performance can be measured by wavefront aberration. If it was measured, it can be easily reflected in the optical head.

  However, it is difficult to manage whether it is placed correctly by simply placing it. Therefore, the usefulness of irradiating a lens tilt adjusting laser to the mirror surface of the edge surface provided outside the lens surface on the disk surface side is as described above. Further, even when the shape of the mirror surface of the edge surface provided outside the lens surface of the laser incident surface is as shown in FIG. 11, the second aspect of the present invention is useful. When the shape is as shown in FIG. 11, it is unstable when a mirror surface of the edge surface provided outside the lens surface of the laser incident surface is placed on the lens mounting portion of the optical head. Therefore, the correct lens tilt position can be corrected by irradiating the lens tilt adjusting laser on the mirror surface of the edge surface provided outside the lens surface on the disk surface side with respect to the tilt of the optical pickup lens.

  The third aspect of the present invention shows that any material that can be used for the optical pickup lens can be applied, and a typical example is plastic.

  In the fourth aspect of the present invention, the aspect of the present invention typically defines an opening diameter NA. In a DVD or the like having a low aperture, it can be said that the tolerance for tilting the optical pickup lens attached to the optical head is now wide due to technological progress. However, for an optical pickup lens having a large aperture NA such as a BD optical pickup lens, the present patent is useful in that it can be easily attached to the optical head. For this reason, the aperture diameter NA is limited to 0.84 or more, which is the specification of the BD optical pickup lens.

  The fifth aspect of the present invention is an aspect provided to limit light having a wavelength of 405 nm, which is the specification of the optical pickup lens of the BD, as in the fifth aspect of the present invention. The laser wavelength mounted on the optical pickup has a wide variation with a large variation of 415 nm or less. Since this patent is an invention that is considered to be able to exhibit sufficient performance even at these wavelengths, such a limitation is provided.

  The sixth aspect of the present invention shows a product in which the present invention is actually utilized. This is the first effect of the optical pickup lens of the present invention when mounted on an optical disk reading device and recording device. Therefore, a regulation was made.

  When mounting an optical pickup lens used in an optical head and an optical disk device, an optical pickup lens with a good wavefront aberration measurement result, which is one of the performance evaluations of the optical pickup lens, can easily provide a good light spot on the optical head. Can be obtained.

  Embodiments of the present invention will be specifically described below, but the present invention is not limited to them.

  An optical pickup lens mold was manufactured by cutting or grinding. The mold base material does not affect this patent, and the lens surface or mirror surface may be produced by directly grinding the base material. Alternatively, a lens surface or mirror surface may be formed by cutting after forming a shape close to the shape of the optical pickup lens and then applying nickel plating or the like. In both methods, processing for improving the durability of the surface may be performed after the lens surface or mirror surface is manufactured.

  As a material for molding the optical pickup lens, a transparent material, a resin such as polyolefin resin, polycarbonate resin, acrylic resin, epoxy resin, ABS resin, glass, or the like is used. However, the transmittance around 395 nm to 415 nm is important for reading and writing on a BD disk with a wavelength of 405 nm, and as easy-to-handle resins, cycloolefin polymers, cyclic olefin copolymers, etc. It is preferable to use a transparent resin material exhibiting good transmittance at a wavelength of 405 nm. The resin may be a simple substance, or an additive for improving the light resistance may be added.

  The optical pickup lens can be manufactured by injection molding these transparent resin materials, but is not limited to this manufacturing method, and may be manufactured by a 2P (Photo-Polymer) method, or cured at a specific wavelength. A resin to be cured, for example, an ultraviolet curable resin, may be poured into an optical pickup lens mold and then cured by irradiation with ultraviolet rays. In addition, a resin material such as epoxy is poured into an optical pickup lens mold and cured to cure the lens shape, or a resin that is cured by applying a specific temperature to the optical pickup lens mold. The lens shape may be formed by pouring and mixing and curing. As a material for the optical pickup lens, optical glass may be used, or polishing or molding may be used.

  The lens surface of the optical pickup lens is provided with one aspherical surface, a spherical surface, or a flat surface optimized for each lens surface when forming a lens surface on the laser incident surface side or the disk surface side. A structure may exist on the laser incident surface side of the optical pickup lens or on the lens surface on the disk surface side. For example, an annular zone having a certain width and depth may be formed concentrically or spirally on the lens surface. As for the formation direction of the groove of the annular zone, a step may be formed in a direction in which the sag becomes deep when the lens surface is directed toward the outer diameter, and the step may be formed in a direction in which the step is shallow. . Moreover, the shape which becomes deep outside the annular zone where this level | step difference becomes shallow, and the shape which becomes shallow outside the level | step difference shape which becomes deep conversely may be sufficient. This annular step is a type of optical pickup lens that collects light by using the refraction of light in each annular zone, and the interference effect of light in the adjacent annular zone with each annular zone as a boundary. Any type of optical pickup lens that collects light amplified using light and an optical pickup lens that includes all of these may be used. When such a structure is formed on the lens surface, the same aspheric surface may be provided at the step of each annular zone, but different aspheric surfaces are provided at the step. Also good.

A film for controlling the transmittance, such as an antireflection film or a reflection film, may be provided on the lens surface. For this thin film, a film thickness and a material that can realize the desired transmittance performance of the optical pickup lens can be selected. The structure of this film may be a single-layer film or a plurality of films, that is, a film structure such as a two-layer, three-layer, four-layer, five-layer, six-layer, and seven-layer film. In the case of using a plurality of films, the same material may be repeatedly formed using different films. As the material of the thin _{film, AlF 3, AlN, Al 2} O 3, BaF 2, BeO, Bi 2 O 3, BiF3, CaF 2, CdSe, CdS, CdTe, CeF 3, CeO 2, CsI, Cr 2 O 3, _{DyF 2, Fe 2 O 3,} GaAs, GdF 3, Gd 2 O 3, Ge, HfO 2, HoF 3, In 2 O 3, ITO, LaF 3, La 2 O 3, LiF, MgF 2, MgO, NaF, _{Na 3 AlF 6, Na 5,} Al 3 F 14, Nb 2 O 5, NdF 3, Nd 2 O 3, PbCl 2, PbCl 2, PbF 2, PbTe, PbO, PbS, Pr 6 O 11, Sb 2 S 3 , Sb ₂ O ₃ , Sc ₂ O ₃ Si, Si ₃ N ₄ , SiO, Si ₂ O ₃ , SiO ₂ , SnO ₂ , SrO ₂ , SrF ₂ , Ta ₂ O ₅ , Te, Ti, TiN, TiNxWv, TiO _{2, TlCl, ThF4, ThO 2} , V 2 O 5, WO 3, YF 3, Y 2 O 3, YbF 3, Yb 2 O 3, ZnO, ZnS, ZnSe, ZrO ₂ or the like can be mentioned.

  Hereinafter, in order to specifically show the effect of the present invention, it will be specifically described with reference to the drawings. In the embodiment, the advantage of the present invention is shown by using a spot measuring device. However, even in an optical device such as an optical drive in which an optical pickup lens is actually mounted, in order to record and reproduce an optical disc satisfactorily, The light spot formed by the optical pickup lens needs to have a good shape, and this example can be explained. In addition, although an Example demonstrates this invention concretely, the aspect of this invention is not limited by this. The wavefront aberration may be measured using any method such as the Fizeau method, the Mach-Cender method, or the Shack-Hartmann method.

  In measuring the wavefront aberration, the mirror surface on the laser incident surface side of the present invention only needs to have a mirror surface with an area sufficient to adjust the lens tilt when measuring the wavefront aberration of the lens, and once formed on the laser incident surface side. A part of the mirror surface may be roughened. As a roughening method, it may be roughened by a mold, but may be roughened by a molded lens. The reason for intentionally ruining the mirror surface part in this way is that when attaching the optical pickup lens to the optical head, if the laser for adjusting the lens tilt of the optical pickup lens is irradiated to the mirror surface on the disk surface side, this laser is If the mirror surface on the disk surface is semi-transmitted and reflected on the mirror surface on the laser incident surface side, and there is return light on each mirror surface, each return light interferes, and the lens tilt adjustment laser of the optical pickup lens It may not perform its original function. In such a case, it is conceivable to roughen the mirror surface on the laser incident surface side, which becomes unnecessary return light.

  A plastic lens using a cycloolefin polymer having an outer diameter of φ3.50 mm was produced by injection molding. A lens surface using an aspherical coefficient as shown in Table 1 was provided on the lens surface portion on the incident surface side and the lens surface portion on the disk surface side. Further, a mirror surface portion was provided in the outer diameter direction from the outside of the lens surface on the laser incident surface side and the disk surface side. A schematic diagram is shown in FIG.

  The lens surface 28 on the laser incident surface side and the mirror surface portion 36 provided outside the laser surface were manufactured using the same mold. At this time, when producing the mold, the lens surface was continuously made up to the mirror surface when being processed by cutting.

  The lens surface 32 on the disk surface side and the mirror surface portion 37 provided outside the lens surface 32 were produced by separate molds.

  The wavefront aberration measurement of the pickup lens 27 thus manufactured was performed as follows. First, an aberration measurement folder having a lens fixing portion that can support the pickup lens 27 with a mirror surface on the laser incident surface side was prepared. Next, the lens fixing portion of this folder was installed in the wavefront aberration measuring apparatus as shown in FIG. 13 so as to be perpendicular to the incident direction of the laser 62 of the wavefront aberration measuring apparatus. The mirror surface portion 59 provided outside the lens surface on the laser incident surface side of the optical pickup lens was placed on the lens fixing portion 58 of the folder 57 thus adjusted. In this state, wavefront aberration was measured. The measurement aperture diameter of the wavefront aberration is shown in Table 1. The wavefront aberration is measured at a room temperature of 26 ° C., the wavelength of the aberration measurement laser is 407 nm, and the parallel flat glass 60 corresponding to the disk thickness is placed on the disk surface side so that the spherical aberration of the lens is reduced. It was carried out by putting it on the laser emission surface side. Thus, the wavefront aberration was measured, and it was confirmed that the total of all wavefront aberrations of the optical pickup lens was 45 mλrms or less. Next, with the optical pickup lens mounted on the aberration measurement jig as it is, the aberration measurement jig is tilted to tilt the optical pickup lens, and a value that minimizes the third-order coma aberration is searched for. Table 8 shows the third-order coma aberration at this time. Next, the light spot measurement of this optical pickup lens was performed and shown in FIG. When performing the light spot measurement, as in the aberration measurement device, the lens fixing portion 67 of the folder 66 of the light spot measurement device is perpendicular to the incident direction of the laser 65 of the light spot measurement device as shown in FIG. installed. The mirror surface portion 68 provided outside the lens surface on the laser incident surface side of the optical pickup lens was placed on the lens fixing portion 67 of the folder thus adjusted. This state is shown in Table 8 with the lens tilt origin and lens tilt 0 °.

  The measurement is performed at a room temperature of 26 ° C., the wavelength of the laser for aberration measurement is 407 nm, and a parallel plate glass corresponding to the disc thickness is placed on the laser emission surface side of the disc surface side so that the spherical aberration of the lens becomes small. In order to measure the light spot with higher accuracy, the parallel plate glass 69 was attached to the surface of the objective lens 63 of the light spot measuring device facing the optical pickup lens, and the light spot was measured. The laser 65 used was a laser having a rim intensity of 80% or more. Here, the aperture diameter of the light spot measurement is shown in Table 1. In this state, the light spot diameter is measured, and in FIG. 14, the optical pickup lens is tilted so that the light spot diameter is good. The measurement results are shown in Table 8. Here, the good light spot diameter is determined by looking at the spot state of the 0th-order light. In general, it is often a laser ellipse to be used. When the maximum position of the light spot of the light spot is the center of the light spot, the long axis of the laser elliptical light used to include that center is the axis. The case where the spot diameter was line symmetric was determined as a good spot.

  A plastic lens using a cycloolefin polymer having an outer diameter of φ3.50 mm was produced by injection molding. A lens surface using an aspherical coefficient as shown in Table 1 was provided on the lens surface portion on the incident surface side and the lens surface portion on the disk surface side. Further, a mirror surface portion was provided in the outer diameter direction from the outside of the lens surface on the laser incident surface side and the disk surface side. A schematic diagram is shown in FIG. The lens surface 39 on the laser incident surface side and the mirror surface portion 47 provided outside the laser surface were manufactured using the same mold. At this time, when producing the mold, the lens surface was continuously made up to the mirror surface when being processed by cutting. Similarly, the lens surface 43 on the disk surface side and the mirror surface portion 48 provided on the outer side thereof were produced with the same mold. At this time, when producing the mold, the lens surface was continuously made up to the mirror surface when being processed by cutting.

  The wavefront aberration of the pickup lens 38 thus manufactured was measured as follows. First, a folder for aberration measurement was prepared in which a lens fixing portion was provided so that the pickup lens 38 can be supported by a mirror surface on the laser incident surface side. Next, in the wavefront aberration measuring apparatus, the lens fixing portion of this folder was installed as shown in FIG. 15 so as to be perpendicular to the laser incident direction of the wavefront aberration measuring apparatus. The mirror surface portion 72 provided outside the lens surface on the laser incident surface side of the optical pickup lens was placed on the lens fixing portion 71 of the folder 70 thus adjusted. In this state, wavefront aberration was measured. The wavefront aberration is measured at room temperature of 26 ° C., the wavelength of the aberration measuring laser is 407 nm, and the parallel flat glass 73 corresponding to the disc thickness is disposed on the disc surface side so that the spherical aberration of the lens is reduced. It was carried out by putting it on the laser emission surface side. Here, the measurement aperture diameter of the wavefront aberration is shown in Table 1. Thus, the wavefront aberration was measured, and an optical pickup lens having all wavefront aberrations of 45 mλrms or less was manufactured.

  Next, with the optical pickup lens mounted on the aberration measurement jig as it is, the aberration measurement jig is tilted to tilt the optical pickup lens, and a value that minimizes the third-order coma aberration is searched for. Table 8 shows the third-order coma aberration at this time. Next, the light spot measurement of this optical pickup lens was performed and shown in FIG. When performing the light spot measurement, as in the aberration measurement device, the lens fixing portion 77 of the folder 76 of the light spot measurement device is perpendicular to the incident direction of the laser 80 of the light spot measurement device as shown in FIG. installed. The mirror surface portion 78 provided outside the lens surface on the laser incident surface side of the optical pickup lens was placed on the lens fixing portion 77 of the folder thus adjusted. This state is shown in Table 8 with the lens tilt origin as the lens tilt 0 °. The laser 80 used was a laser having a rim intensity of 80% or more. Here, the aperture diameter of the light spot measurement is shown in Table 1. In this state, the light spot measurement as in Example 1 was performed, and the measurement results are shown in Table 8.

  Example 3 uses an optical pickup lens manufactured by the same manufacturing method as Example 2, but the optical spot measurement method is different.

  First, a procedure similar to that in the second embodiment is taken. A folder for aberration measurement was prepared in which a lens fixing portion was provided so that the pickup lens could be supported by a mirror surface on the laser incident surface side. Next, in the wavefront aberration measuring apparatus, the lens fixing portion of this folder was installed as shown in FIG. 15 so as to be perpendicular to the laser incident direction of the wavefront aberration measuring apparatus. The mirror surface portion 59 provided outside the lens surface on the laser incident surface side of the optical pickup lens was placed on the lens fixing portion 58 of the folder 57 thus adjusted. In this state, wavefront aberration was measured. In measuring the wavefront aberration, the wavefront aberration is measured at a room temperature of 26 ° C., the wavelength of the laser for aberration measurement is 405 nm, and the parallel flat glass corresponding to the disk thickness is used so that the spherical aberration of the lens is reduced. 60 was placed on the laser emission surface side of the disk surface side. Thus, the wavefront aberration was measured, and an optical pickup lens having all wavefront aberrations of 45 mλrms or less was manufactured.

  Next, with the optical pickup lens mounted on the aberration measurement jig as it is, the aberration measurement jig is tilted to tilt the optical pickup lens, and a value that minimizes the third-order coma aberration is searched for. Table 8 shows the third-order coma aberration at this time. Next, the light spot of this optical pickup lens was measured. In performing the light spot measurement, as in the aberration measuring apparatus, the lens fixing portion of the folder of the light spot measuring apparatus was installed as shown in FIG. 16 so as to be perpendicular to the laser incident direction of the light spot measuring apparatus. A lens surface on the laser incident surface side of the optical pickup lens and a mirror surface portion provided outside the lens surface were placed on the lens fixing portion of the folder thus adjusted.

  This is different from the second embodiment. As shown in FIG. 17, the laser beam 84 is applied from the angle adjusting laser device 83 to the mirror surface on the disk surface side, and the laser spot irradiated on the mirror surface is observed, so that the spot is minimal and becomes a perfect circle. The light spot measuring jig was adjusted. At this time, the incident angle of the angle adjusting laser 84 was set to be horizontal with respect to the laser incident direction 88 of the light spot measuring device. This state is shown in Table 8 with the lens tilt origin and lens tilt 0 °. Next, the same light spot measurement as in Example 2 was performed, and the measurement results are shown in Table 8.

  Except for using the lens shown in Table 2, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 2, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 2, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 3, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 3, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 3, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 4, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 4, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 4, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 5, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 5, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 5, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 6, there is no difference from Example 1 to Example 3.

  Except for using the lens shown in Table 6, there is no difference from Example 1 to Example 3.

Except for using the lens shown in Table 6, there is no difference from Example 1 to Example 3.
(Comparative Example 1)

  A plastic lens using a cycloolefin polymer having an outer diameter of φ3.50 mm was produced by injection molding. The lens surface portion on the incident surface side and the lens surface on which the aspheric coefficient such as the lens shown in Table 7 is used are provided on the disk surface side lens. Further, a mirror surface portion was provided in the outer diameter direction from the outside of the lens surface on the laser incident surface side and the disk surface side.

  The lens surface on the laser incident surface side and the mirror surface portion provided on the outside thereof were produced with separate molds.

The lens surface on the disk surface side and the mirror surface portion provided on the outside thereof were produced with separate molds.
Measurement of the light spot of the pickup lens thus fabricated was evaluated in the same manner as in Example 1. The measurement results are shown in Table 8.
(Comparative Example 2)

  The lens produced as in Comparative Example 1 was evaluated in the same manner as in Example 3. The measurement results are shown in Table 8.

  Table 8 shows the results of Examples 1 to 18 and Comparative Examples 1 to 2.

  In Examples 1 to 18, it can be seen that the angle at which the optical pickup lens is tilted together with the folder until the satisfactory light spot diameter is obtained is small from the angle at the origin in the light spot measurement. In particular, it can be seen that the angle at which the optical pickup lens is tilted together with the folder is small before Example 3 and Example 6, Example 9, Example 12, Example 15, Example 18, and Example 18 obtain a good light spot diameter. . These examples are manufactured with a mold having the same surface diameter as the disk-side mirror surface. By applying a lens tilt adjustment laser to this mirror surface, the lens can be tilted more accurately. It can be seen that the angle at which the optical pickup lens is tilted together with the folder becomes smaller before a good light spot diameter is obtained. In contrast, Comparative Example 1 and Comparative Example 2 show that the angle at which the optical pickup lens is tilted together with the folder is small before a good light spot diameter is obtained. From this result, if the mirror surface or mounting surface on the laser incident surface side is a mold different from the lens surface, simply mounting it on the optical head, together with the folder until a good light spot diameter can be obtained. It is hard to say that the optical pickup lens has to be tilted greatly, and it easily reflects the performance of the optical pickup lens.

Further, Comparative Example 2 is a mirror surface on the disk surface side, and the tilt is grasped and the lens is tilted for adjustment. The tilt angle of the optical pickup lens together with the folder is obtained until a good light spot diameter is obtained. Although smaller than Comparative Example 1, it is larger than Examples 1 to 18 of this patent. Comparative Example 2 shows that adjustment is insufficient even when a lens tilt adjusting laser is applied to the mirror surface because the mirror surface and the lens surface on the disk surface side are separate molds.

It is sectional drawing of a general pickup lens. It is sectional drawing of a general pickup lens. It is an assumed sectional view of a general pickup lens. It is an assumed sectional view of a general pickup lens. It is an assumed sectional view of a general pickup lens. It is an assumed sectional view of a general pickup lens. It is sectional drawing of the optical pick-up lens of this invention. It is sectional drawing of the optical pick-up lens of this invention. It is an example of an assumed sectional view of the optical pickup lens of the present invention. It is an example of an assumed sectional view of the optical pickup lens of the present invention. It is an example of an assumed sectional view of the optical pickup lens of the present invention. It is an example of an assumed sectional view of an optical pickup lens which is not the present invention. It is a wavefront aberration measurement measurement method diagram of the optical pickup lens of the present invention. It is a light spot measurement measuring method figure of the optical pick-up lens of the present invention. It is a wavefront aberration measurement measurement method diagram of the optical pickup lens of the present invention. It is a light spot measurement measuring method figure of the optical pick-up lens of the present invention. It is a lens tilt adjustment method diagram as a pre-stage of the light spot measurement of the present invention. Outline of mold division for lens molding in FIG. Overview of mold division for lens molding in FIG. Overview of mold division for lens molding in FIG. Overview of mold division for lens molding in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 General pick-up lens 2 Lens surface of optical pick-up lens of laser incident surface side 3 Lens surface of optical pick-up lens of disc surface side 4 Laser incident surface side specular inner diameter 5 Laser incident surface side specular outer diameter 6 Laser incident surface side specular surface Area 7 Laser incident surface side mirror surface and optical head mounting surface 8 Disc surface side mirror surface 9 Optical axis 10 Optical pickup head laser 11 General pickup lens 12 Lens surface of optical pickup lens on laser incident surface side 13 Disc surface side Lens surface of optical pickup lens 14 Laser incident surface side mirror inner diameter 15 Laser incident surface side mirror outer diameter 16 Laser incident surface side mirror surface region 17 Disk surface side mirror surface 18 Optical pickup head laser 19 Optical axis 20 Optical axis 21 Optical axis 22 Optical pickup Lens laser incident surface side mirror Surface and optical head mounting surface 23 Optical axis 24 Optical pickup lens Laser incident surface side mirror surface and optical head mounting surface 25 Optical axis 26 Laser incident surface side mirror surface 27 Optical pickup lens 28 Lens surface of optical pickup lens on laser incident surface side 29 Laser Incident surface side mirror surface region 30 Laser incident surface side mirror surface inner diameter 31 Laser incident surface side mirror surface outer diameter 32 Lens surface of optical pickup lens on disk surface side 33 Disc surface side mirror surface region 34 Disc surface side mirror surface inner diameter 35 Disc surface side mirror surface outer diameter 36 Laser incident surface side mirror surface and optical head mounting surface 37 Disk surface side mirror surface 38 Optical pickup lens 39 Lens surface of optical pickup lens on laser incident surface side 40 Laser incident surface side mirror surface region 41 Laser incident surface side mirror surface inner diameter 42 Laser Incident surface side mirror surface outer diameter 3 Lens surface of optical pickup lens on disk surface side 44 Disk surface side mirror surface area 45 Disk surface side mirror surface inner diameter 46 Disk surface side mirror surface outer diameter 47 Laser incident surface side mirror surface and optical head mounting surface 48 Disk surface side mirror surface 49 Light Axis 50 Optical pickup lens laser incident surface side mirror surface and optical head mounting surface 51 Optical axis 52 Optical pickup lens laser incident surface side mirror surface and optical head mounting surface 53 Optical axis 54 Optical pickup lens laser incident surface side mirror surface and optical head mounting surface 55 Optical axis 56 Optical pickup lens Laser incident surface side mirror surface and optical head mounting surface 57 Folder for wavefront aberration measurement 58 Lens fixing portion 59 Mirror surface portion 60 Parallel plate glass 61 Optical axis 62 Laser of wavefront aberration measuring device 63 Optical spot measuring device Objective lens 64 light 65 Laser for optical spot measuring device 66 Folder for optical spot measuring device 67 Lens fixing portion 68 Mirror surface portion 69 Parallel plate glass 70 Folder for wavefront aberration measurement 71 Lens fixing portion 72 Mirror surface portion 73 Parallel plate glass 74 Optical axis 75 Wavefront aberration measurement Laser of the device 76 Folder of the light spot measuring device 77 Lens fixing part 78 Mirror surface portion 79 Parallel flat glass 80 Laser of the light spot measuring device 81 Objective lens of the light spot measuring device 82 Optical axis 83 Laser device for angle adjustment 84 For angle adjustment Laser 85 Optical axis 86 Laser of wavefront aberration measuring device 87 Disk surface side lens surface mold of the lens in FIG. 1 88 Laser entrance surface side lens surface mold of the lens in FIG. 1 89 Disk surface side edge surface metal of the lens in FIG. Type 90 Laser incident surface side of the lens in FIG. Bar surface mold 91 Drum body mold for molding the lens of FIG. 1 92 Disk surface side lens surface mold of the lens of FIG. 2 Laser incident surface side lens surface mold of the lens of FIG. The disk surface side edge surface mold 95 of the lens in FIG. 2 The laser incident surface side edge surface mold 96 of FIG.
97 Disk surface side lens surface mold of the lens of FIG. 7 98 Laser surface side lens surface mold of the lens of FIG. 7 99 Disk surface side edge surface mold of the lens of FIG. 7 100 Laser input surface side of the lens of FIG. Edge surface mold 101 Body mold of mold for lens molding of FIG. 7 102 Disk surface side lens surface mold of the lens of FIG. 8 Laser incident surface side lens surface mold of the lens of FIG. 8 disk surface side edge mold 105 laser incident surface side edge mold of the lens of FIG. 8 106 mold body mold for lens molding 201 optical pickup lens laser incident surface side mirror surface and optical head mounting surface

Claims (6)

It is characterized in that both the edge surface of the mounting surface outside the effective diameter of the laser light path on the laser incident surface side of the optical pickup lens and the edge surface outside the effective diameter of the laser light path on the disk surface side are mirror surfaces. An optical pickup lens that
The mirror surface formed toward the outer diameter from the lens surface on the laser incident surface side is a mounting surface for the optical head, and is formed toward the outer diameter from the lens surface on the laser incident surface side. The optical pickup lens is characterized in that the mirror surface and the lens surface on the laser incident surface side are manufactured by a single mold.   2. The optical pickup lens according to claim 1, wherein the mirror surface formed from the lens surface on the disk surface side toward the outer diameter and the lens surface on the disk surface side are produced by a single mold.   3. The optical pickup lens according to claim 1, wherein the optical pickup lens is made of plastic.   An optical pickup lens having an aperture diameter NA of 0.84 or more.   5. The optical pickup lens according to claim 1, wherein light having a wavelength of 415 nm or less is used.   6. An optical head and an optical disc apparatus, wherein the optical pickup lens according to claim 1 is used.

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