JP2010160860A - Composite optical element and optical pickup equipped with composite optical element - Google Patents

Abstract

The present invention provides a composite optical element that is light and small and made of an optimum glass material suitable for a plurality of optical disks.
In a composite optical element, a first optical element for condensing a first light beam and a second optical element for condensing a second light beam are arranged in parallel with each other. The composite optical element 10 integrally molded, wherein the first optical element 11 is made of a resin material, and the second optical element 12 is a glass material having a glass transition point higher than the glass transition point of the resin material. Consists of.
[Selection] Figure 1

Description

  The present invention relates to a composite optical element and an optical pickup including the composite optical element.

  In recent years, CDs and DVDs are generally widely used as optical disc recording / reproducing media, and Blu-ray Disc (hereinafter simply referred to as BD) and the like are becoming more popular as higher density optical disc recording / reproducing media. In addition, there is an optical pickup device that can record and reproduce information on a plurality of media, and this device incorporates a composite optical element in which a plurality of types of objective lenses adapted to each medium are combined. ing.

  For example, Patent Document 1 discloses a composite optical element in which a plurality of objective lenses are fixed to a single substrate.

Patent Document 2 discloses a composite optical element in which a plurality of objective lenses are integrally formed by molding.
Japanese Patent Laid-Open No. 10-188323 JP-A-2005-293686

  However, in the composite optical element disclosed in Patent Document 1, the number of components increases because a substrate is used to fix a plurality of objective lenses. As a result, the weight reduction and size reduction of the composite optical element and the optical pickup are hindered.

  The shape and material of the objective lens vary depending on the type of optical disk. The lens material used for DVD / CD is not always suitable as a lens material for BD from the viewpoints of freedom of optical design, ease of molding, cost, and the like. Therefore, it is necessary to select an optimal lens material according to each optical disc. However, Patent Document 2 does not disclose any material for the objective lens.

  An object of the present invention is to provide a composite optical element that is light and small and is made of an optimum glass material suitable for each optical disk. Another object of the present invention is to enable the optical pickup to be reduced in size and cost and cost.

  In order to solve the above-described problem, the composite optical element according to the present invention includes a first optical element that condenses the first light beam and a second optical element that condenses the second light beam, the optical axes of which are parallel to each other. A composite optical element disposed and integrally molded, wherein the first optical element is made of a resin material, and the second optical element is made of a glass material having a glass transition point higher than the glass transition point of the resin material. It has the composition which becomes.

  According to the present invention, it is possible to provide a composite optical element that is light and small and made of an optimum glass material corresponding to each optical disk. In addition, the pickup device can be reduced in weight and size and cost.

  Embodiments of the present invention will be described below with reference to the drawings. In the embodiment, components that perform the same operation may be denoted by the same reference numerals and the description thereof may be omitted.

<Embodiment 1>
1A is a schematic cross-sectional view of the composite optical element 10 according to Embodiment 1, and FIG. 1B is a view when the composite optical element 10 according to Embodiment 1 is viewed from the optical axis direction. FIG.

  As shown in FIG. 1, the composite optical element 10 has a configuration in which a first optical element 11 and a second optical element 12 are joined and integrated by a connecting edge 15. The first optical element 11 and the second optical element 12 have a positional relationship in which their optical axes 16 are substantially parallel. The shapes and sizes of the first optical element 11 and the second optical element 12 are appropriately set according to the required optical design.

  In the present embodiment, the first optical element 11 is optically designed for BD and used as an objective lens for BD. The second optical element 12 is optically designed for DVD / CD and is used as an objective lens for DVD / CD.

  A light beam 17 illustrated in FIG. 1 is an example of a first light beam, a light beam 18 is an example of a second light beam, and a light beam 19 is an example of a third light beam. The light beam 17 is laser light emitted from a first laser element (not shown), and is laser light having a wavelength of 400 to 410 nm corresponding to BD. The light beams 18 and 19 are, for example, laser light emitted from a second laser element (not shown), laser light having a wavelength of 650 to 650 nm corresponding to DVD and laser light having a wavelength of 770 to 830 nm corresponding to CD. is there.

  The lens material of the first optical element 11 in this embodiment is ZEONEX 340R (glass transition point 123 degrees) manufactured by Nippon Zeon, and is an example of a resin material. The lens material of the second optical element 12 is PSK200 (glass transition point 386 degrees, yield point 412 degrees) made by Sumita Optical Glass, which is an example of a glass material. In the present embodiment, the glass transition point of the resin material forming the first optical element is lower than the glass transition point of the glass material forming the second optical element.

  When molding a composite optical element as shown in FIG. 1, it is advantageous to use a lens material having a different glass transition point as in this embodiment in the following points.

  For example, a BD objective lens has a larger numerical aperture (NA: numerical aperture; hereinafter simply referred to as NA) and a shorter focal length than a DVD / CD objective lens. Therefore, the objective lens for BD has a smaller lens diameter and the like than the objective lens for DVD / CD, so the shape of the objective lens itself becomes smaller. Further, the objective lens for BD has a small curvature of the optical effective surface 25 and a large thickness deviation ratio. Here, the “thickness ratio” is the ratio of the thickest part to the thinnest part in the thickness of the objective lens in the optical axis direction.

  A lens with a small shape is difficult to mold with a mold compared to a lens with a large shape. In addition, a lens having a large thickness deviation ratio is generally difficult to mold and transfer with a mold as compared with a lens having a small thickness deviation ratio.

  On the other hand, a glass material having a low glass transition point is easy to mold because it requires a smaller amount of shrinkage during molding than a glass material having a high glass transition point. In the present embodiment, the first optical element as the BD objective lens is molded from a resin material having a glass transition point lower than that of the second optical element as the DVD / CD objective lens. Therefore, even a BD objective lens that is more difficult to mold than a DVD / CD objective lens can be easily molded by the following method. Therefore, by using lens materials suitable for BD and DVD / CD, it is possible to provide a composite optical element having different lens materials as shown in FIG.

  Hereinafter, a method for manufacturing the composite optical element 10 will be described with reference to FIGS. 2 and 3. In the composite optical element 10 according to this embodiment, the second optical element 12 having a high glass transition point is first molded, and then the first optical element 11 is molded so as to be joined to the second optical element 12.

  FIG. 2 is a schematic cross-sectional view showing the manufacturing process of the second optical element 12. The second optical element mold 20 includes an upper mold 21, a lower mold 22, and a body mold 23. FIG. 2A is a diagram showing a preparation stage for molding the second optical element, and FIG. 2B is a diagram showing a stage where the molding of the second optical element is completed.

  First, a glass material 14 for the second optical element is prepared. Next, the lower mold 22 is inserted into the body mold 23, and the second optical element glass material 14 is placed on the lower mold 22. Thereafter, the upper die 21 is inserted into the barrel die 23 and placed on the glass material 14 for the second optical element.

  Next, the second optical element mold 20 containing the second optical element glass material 14 is placed in a molding apparatus (not shown). The second optical element mold 20 placed in the molding apparatus is sequentially fed through a preliminary heating process, a pressing process, and a cooling process by an arm or the like. In the present embodiment, the mold temperature in the pressing process for molding the second optical element is 570 degrees. Thereby, as shown in FIG.2 (b), the 2nd optical element 12 is shape | molded.

  The second optical element mold 20 is further cooled by a cooling plate after the cooling process is completed. When the mold temperature becomes 200 ° C. or less, the second optical element mold 20 is taken out from the molding machine. Then, the upper mold 21 is removed, and the second optical element 12 is taken out.

  Next, molding of the first optical element 11 will be described. FIG. 3 is a schematic cross-sectional view showing a manufacturing process of the first optical element 11. The first optical element mold 30 includes an upper mold 31, a lower mold 32, a body mold 33, and a second optical element mold 34. Consists of.

  FIG. 4 is a schematic cross-sectional view of the body mold 33 when viewed from the pressing direction. As shown in FIG. 4, the body mold 33 surrounds the outer peripheries of the upper mold 31, the lower mold 32, and the second optical element mold 34, and is cut to form the connection edge 15. A notch 35 is provided. The notch 35 is provided from the upper end of the body mold 33 to a position reaching the lower mold 32.

  First, the 2nd optical element 12 obtained by shape | molding previously and the resin material 13 for 1st optical elements are prepared. Next, the lower mold 32 and the second optical element mold 34 are inserted into the body mold 33. In the present embodiment, the second optical element mold 34 is a mold for placing the previously molded second optical element 12, and does not press the second optical element 12. The lower mold 32 and the second optical element mold 34 are arranged in a direction perpendicular to the pressing direction of the first optical element mold 30.

  Next, the second optical element 12 is placed on the second optical element mold 34, and the first optical element resin material 13 is placed on the lower mold 32. Thereafter, the upper mold 31 is inserted into the body mold 33 and placed on the first optical element resin material 13.

  Next, the first optical element mold 30 containing the first optical element resin material 13 and the second optical element 12 is placed in a molding apparatus (not shown). The first optical element mold 30 placed in the molding apparatus is sequentially fed through the preheating step, the pressing step, and the cooling step by an arm or the like in the same manner as in the manufacturing process of the second optical element 12 described above. In the present embodiment, the mold temperature in the pressing process of the first optical element is 260 degrees. In the pressing process of the first optical element, the resin material 13 for the first optical element is pressed by the upper mold 31 and the lower mold 32 and deforms in accordance with the shape of the mold. At this time, the first optical element resin material 13 is deformed so as to extend in a direction perpendicular to the pressing direction, and is joined to the second optical element 12 through the notch 35.

  In the present embodiment, the glass transition point of the second optical element 12 is 430 degrees, which is sufficiently higher than 260 degrees that is the mold temperature of the first optical element 11. Therefore, the shape of the second optical element 12 does not change during the molding of the first optical element.

  The first optical element mold 30 is further cooled by a cooling plate after the cooling process is completed, and is taken out when the mold temperature becomes 200 degrees or less. Since the upper end of the notch 35 is open, the molded composite optical element 10 can be easily taken out from the first optical element mold 30.

  As described above, the composite optical element according to the present embodiment employs a process in which the second optical element is first molded and then bonded to the second optical element while the first optical element is molded. . Therefore, even with lens materials having different properties, a composite optical element in which two types of optical elements as shown in FIG. 1 are integrated can be obtained without complicated process control.

<Embodiment 2>
FIG. 5A is a schematic cross-sectional view of the composite optical element 40 according to Embodiment 2, and FIG. 5B is a view when the composite optical element 40 according to Embodiment 2 is viewed from the optical axis direction. FIG.

  In the composite optical element 40 according to the second embodiment, the first optical element and the second optical element are integrated as in the composite optical element 10 according to the first embodiment. The composite optical element 40 according to Embodiment 2 has the first diffraction grating portion 43 on the optical effective surface 25 of the first optical element, and the second diffraction grating portion 44 on the optical effective surface 25 of the second optical element. Is different from the composite optical element 10 according to the first embodiment described above.

  The first diffraction grating portion 43 and the second diffraction grating portion 44 have a relief shape as shown in FIG. 5 and are formed concentrically around the optical axis 16. The diffraction grating portion 43 has a lens action by gradually changing the grating pitch from the optical axis 16 toward the outer periphery.

  The composite optical element 40 according to Embodiment 2 has the following effects by having the first diffraction grating portion 43 and the second diffraction grating portion 44 as described above.

  For example, by forming the first diffraction grating portion 43 in the first optical element as the BD objective lens, it is possible to correct chromatic aberration caused by the difference in the wavelength of the light that has passed through the optical element.

  Further, for example, by forming the second diffraction grating portion 44 in the second optical element as the DVD / CD objective lens, the focal position of the DVD laser light or the CD laser light can be freely changed and adjusted. It becomes possible.

  The first diffraction grating portion 43 and the second diffraction grating portion 44 are formed by a mold having a shape obtained by inverting the diffraction grating shape on the transfer surface. When a diffraction grating is formed on an optical element, the larger the curvature of the optically effective surface, the more difficult it is to transfer the diffraction grating shape by the mold and to maintain the transferred shape. However, since the first optical element 41 according to the second embodiment is molded with a lens material having a glass transition point lower than that of the second optical element 42 as in the first embodiment, it is easy to mold. Therefore, even with an optical element having a small curvature of the optically effective surface such as the first optical element, the diffraction grating shape can be formed relatively easily. Thus, by using lens materials suitable for BD and DVD / CD, a composite optical element as shown in FIG. 5 can be provided.

<Embodiment 3>
The third embodiment relates to an optical pickup using the composite optical element described in the first and second embodiments. FIG. 6 is a schematic perspective view showing an optical pickup 50 equipped with the composite optical element 10 of the type disclosed in the first embodiment.

  The optical pickup 50 according to the second embodiment includes the composite optical element 10, a holding member 52 that holds the composite optical element 10, and an optical system 51.

  The composite optical element 10 includes a first optical element 11 and a second optical element 12. In the present embodiment, the first optical element 11 is an objective lens optically designed for CD / DVD, and the second optical element 12 is an objective lens optically designed for BD.

  The holding member 52 has a drive mechanism. When the holding member 52 is driven with respect to the optical disc, either the first optical element or the second optical element is selected. For example, when the first optical element is selected, the first optical element is incorporated into the optical system 51 of the optical pickup 50. When the second optical element is selected, the second optical element is incorporated into the optical system 51 of the optical pickup 50.

  The optical system 51 includes a laser element 53, a light receiving element 54, a rising mirror 55, an optical chassis 56, and the like. Optical members such as a collimator lens and a prism beam splitter (not shown) are mounted inside the optical chassis 56.

  The laser light emitted from the laser element 53 passes through the inside of the optical chassis 56, is reflected by the rising mirror 55, enters the composite optical element 10, is condensed, and is collected on the information recording surface of the optical disc (not shown). Irradiated. The laser light applied to the optical disk is reflected by the optical disk and enters the light receiving element 54 via the rising mirror 55 and the optical chassis 56. The laser light incident on the light receiving element 54 is converted into an electrical signal, whereby information on the optical disk is read.

  In the present embodiment, the composite optical element 10 is a substrate for fixing the first optical element 11 and the second optical element 12 because the first optical element 11 and the second optical element 12 are integrally molded. Such a member becomes unnecessary and is directly held by the holding member 52. Therefore, the number of parts is reduced, and the optical pickup can be reduced in size and weight.

<Other embodiments>
In the first to third embodiments, the first optical element and the second optical element are joined via the connection edge 15, but the first optical element and the second optical element are directly connected to each outer peripheral part. It may be a joined shape. Such a shape can be realized by reducing the distance between the first optical element mold 30 and the second optical element mold 34.

  In the first to third embodiments, the optical axis of the first optical element 11 and the optical axis of the second optical element 12 are arranged substantially in parallel, but the present invention is not limited to this. For example, the optical axis of the first optical element may be arranged to have a predetermined angle with respect to the optical axis of the second optical element. Since the positional relationship between the first optical element and the second optical element is appropriately set according to the required optical design and the specifications of the optical pickup, the degree of freedom in designing the composite optical element 10 is increased.

  In the first and second embodiments, the first optical element resin material 13 is ZEONEX 340R made by Nippon Zeon and the second optical element glass material 14 is PSK200 made by Sumita Optical Glass, but is not limited thereto. Absent. For example, any glass material having desired optical characteristics can be applied.

  In the first to third embodiments, the two optical elements are integrated. However, the number of optical elements is not limited to this. If necessary, a third optical element or a fourth optical element can be added as appropriate. For example, when a third optical element is added to the composite optical element 10 according to Embodiment 1, a lens material for the third optical element having a smaller glass transition point than the lens materials of the first and second optical elements If selected, the shapes of the first and second optical elements do not change during the molding of the third optical element.

  In the second embodiment, the shape of the diffraction grating portions 43 and 44 is a relief shape. However, the shape is not limited to this. For example, any shape that acts as a diffraction grating, such as a sine wave shape or a rectangular shape. Good.

  In the first and second embodiments, the composite optical element 10 is manufactured using press molding, but the present invention is not limited to this. For example, in the case of a lens material having a small glass transition point, productivity can be improved by adopting injection molding or the like.

(A) Schematic sectional view of the composite optical element according to Embodiment 1, (b) Schematic view when the composite optical element according to Embodiment 1 is viewed from the optical axis direction. Schematic sectional view showing the manufacturing process of the second optical element according to the first embodiment Schematic sectional view showing the manufacturing process of the first optical element according to the first embodiment Schematic sectional view when the body mold of the first optical element molding die according to Embodiment 1 is viewed from the pressing direction. (A) Schematic sectional view of the composite optical element according to the second embodiment, (b) Schematic view when the composite optical element according to the second embodiment is viewed from the optical axis direction. Schematic perspective view of an optical pickup according to Embodiment 3

DESCRIPTION OF SYMBOLS 10 Composite optical element 11 1st optical element 12 2nd optical element 13 Resin material for 1st optical elements 14 Glass material for 2nd optical elements 15 Connection edge part 16 Optical axis 17 1st light beam 18 2nd light beam 19 3rd light beam 20 Second optical element mold 21 Upper mold 22 Lower mold 23 Body mold 25 Optical effective surface 30 First optical element mold 31 Upper mold 32 Lower mold 33 Body mold 34 Second optical element mold 35 Notch 40 Compound Optical Element 41 First Optical Element 42 Second Optical Element 43 First Diffraction Grating Part 44 Second Diffraction Grating Part 50 Optical Pickup 51 Optical System 52 Lens Holding Member 53 Laser Element 54 Light Receiving Element 55 Raising Mirror 56 Optical Chassis

Claims (5)

A first optical element that condenses the first light beam and a second optical element that condenses the second light beam are composite optical elements in which the respective optical axes are arranged in parallel and are integrally molded,
The first optical element is made of a resin material,
The second optical element is made of a glass material having a glass transition point higher than that of the resin material.
Composite optical element. 2. The composite optical element according to claim 1, wherein a curvature of an optical effective surface of the first optical element is larger than a curvature of an optical effective surface of the second optical element. The first optical element includes a first diffraction grating portion on an optically effective surface of the first optical element.
The composite optical element according to claim 1 or 2. The second optical element includes a second diffraction grating portion on an optical effective surface of the second optical element.
The composite optical element according to claim 1. An optical pickup comprising the composite optical element according to claim 1.

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