JP2008290338A - Both-side aspheric plastic lens and manufacturing method for both-side aspheric lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a both-side aspheric lens, in which the centers of optical axes of the first and second surfaces of the lens fit accurately with each other, by using a most inexpensive multi-cavity injection molding mold. <P>SOLUTION: The lens 10 has two divided surfaces 11b and 12b divided in the direction of the optical axis between the entry surface 11a and the injection surface 12a, and the divided surfaces 11b and 12b are both flat. The lens are injection-molded by injection-molding the portion from the injection surface 12a to the divided surface 12b with a front member 12 and then separately injection-molding the portion from the divided surface 11b to the entry surface 11a with a rear member 11, with the molded resins being the same. The injection-molded lens members, or the front member 12 and the rear member 11, are bonded together by applying a UV-curable adhesive to between the divided surfaces 11b and 12b. After center-matching of the optical axes of the entry surface 11a and the injection surface 12a, the resultant article is irradiated with UV light to cure the UV-curable adhesive in order to form a single lens. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing an aspheric plastic lens, and more particularly to a method of manufacturing an aspheric plastic lens in which the center of the first surface and the center of the second surface of the lens almost coincide with each other.

  Conventionally, an optical lens is generally manufactured by a mold composed of an upper mold and a lower mold as disclosed in Patent Document 1 below. The upper mold and the lower mold are respectively attached to a pair of mold plates facing on the same axis, and a guide shaft provided on one side of the mold plate is fitted into a guide hole provided on the other side and positioned. Is slidable. For example, when the upper die is slidable, a barrel die is attached to the lower die, and a lower die body portion provided with a lens molding surface is fitted into a cylindrical hole provided in the barrel die. In the upper mold, the upper mold body part fits into the cylindrical hole of the body mold, and the lens molding surface provided in the upper mold faces the lens molding surface provided in the lower mold on the same axis inside the cylindrical hole. Thus, a lens molding space is formed. A preheated glass material is placed on a lens molding surface provided in the lower mold, and the lens molding space is formed by closing the upper mold and the lower mold, and the lens shape is transferred to the glass material.

  Patent Document 2 below describes a method for improving the accuracy of centering by using a ball bearing in the body mold as described above. Further, Patent Document 3 below describes a method of tapering fitting the outer diameter of the body mold with the upper mold or the lower mold, but this is intended to improve accuracy by fitting at a larger part. To do. Further, Patent Document 4 listed below describes a method of centering by using a pedestal made of a material having a larger coefficient of thermal expansion than that of a mirror piece that forms a lens surface, so as to be an interference fit during molding.

Further, in order to cancel the misalignment of the aspherical lens, when the whole or a part of the lens apparatus is assembled, there is a case where the eccentricity adjustment is performed by moving the lens at one or a plurality of locations while performing projection / imaging. . Although a better image can be obtained than when no adjustment is made, in many cases, image deterioration is unavoidable as compared to the case of using an aspherical lens having no misalignment.
JP 2005-206430 A JP 2004-262734 A JP 2006-137142 A JP-A-11-090964

  As shown in the aforementioned Patent Documents 1 to 4, it is essential to accurately align the centers of the first surface and the second surface of the lens, but it is very difficult to mold the lens. Since the molds on the first and second surfaces are processed together, the shape system is relatively easy to get out, but when combining them as a single mold, it is difficult to align the posture and center. This is because the upper die and the lower die are separate bodies, and are caused by the processing accuracy of the guide, the play of the mating surface, and the like. In addition, since it is difficult to measure the shape of an aspherical surface compared to a spherical surface, it is only possible to correct the mold by directly measuring the shape of the molded lens. In particular, centering is generally difficult even if the radius of curvature near the center of the optical surface is large, even if the center of curvature is large, it is difficult to evaluate even the center, even though the effect on performance is large. Further, many lenses having a small diameter are often made with a multi-cavity mold, and in this case, it is further difficult to align the first surface and the second surface.

  In order to solve the problem, the present invention relates to a method of manufacturing an aspheric plastic lens in which the optical axis centers of the first surface and the second surface of the lens are precisely aligned with the least expensive multi-piece injection mold. It is what we propose.

  The aspheric plastic lens according to the present invention includes a split surface that splits into two in the optical axis direction between a first surface (incident surface) and a second surface (exit surface). The lens members divided into the front member from the second surface to the dividing surface and the rear member from the dividing surface to the first surface are injection-molded with the same plastic material. Two injection-molded lens members (front member and rear member) are joined at the dividing surface, and the first and second surfaces are centered on the optical axis, and then fixed by UV curing adhesive or the like. Into one lens. The shape of the dividing surface may be any shape as long as the optical axis position can be adjusted, but is most preferably a flat surface, and then a spherical surface.

  According to the present invention, the two lens members to be molded have a simple shape because only one surface is aspherical and the other surface is flat or spherical, and it is not necessary to have a mirror surface. One of the molds can be simplified, and even a multi-cavity mold can be molded easily. After molding, the first and second surfaces are centered on the optical axis, and then bonded and fixed to one lens. Therefore, it is possible to obtain a highly accurate double-sided aspherical plastic lens having almost no deviation between the optical axis centers of the first surface (incident surface) and the second surface (exit surface).

  A double-sided aspheric plastic lens and a manufacturing method thereof according to an embodiment of the present invention will be described. As shown in FIG. 1, the lens 10 is a plastic lens used as a projection lens of a projector, and has a concave aspherical entrance surface 11a and a convex aspherical exit surface 12a, and the entrance surface 11a and the exit surface. Dividing surfaces 11b and 12b are provided between the surfaces 12a. The split surface 11b of the rear member 11 having the entrance surface 11a and the split surface 12b of the front member 12 having the exit surface 12a are both formed in a plane, and a transparent UV curable adhesive is interposed therebetween. It is bonded and fixed together. The rear member 11 and the front member 12 are each molded by an injection mold. Since the rear member 11 and the front member 12 are originally designed as one lens, it is naturally formed of the same resin. The rear member 11 includes a flange portion 11f.

  As shown in FIG. 2, the rear member 11, which is one of the members constituting the lens 10, is molded by a movable mold 20 and a fixed mold 30 that are eight-piece injection molds. Eight lens-shaped spaces 21 of the rear member 11 are dug in the movable mold 20, but the fixed mold 30 has only a sprue hole 31 for feeding resin melted in the center to the movable mold 20. The lens shape is not dug. The fixed mold 30 is provided with guide shafts 32 at four corners. Guide holes 22 that fit into the guide shafts 32 are provided at the four corners of the movable mold 20, and the guide shafts 32 slide along the guide holes 22 to open and close the movable mold 20 and the fixed mold 30.

  As shown in FIG. 3, the movable mold 20 has a lens molding space 21 at the center, and a mirror piece 23 is fitted in the center thereof, and an aspheric surface formed at the tip of the mirror piece 23 is formed. The surface 23a forms the incident surface 11a when the rear member 11 is molded. A flange forming surface 20f is provided around the periphery of the mirror piece 23. The flange forming surface 20 f forms the flange portion 11 f with the fixed mold 30. On the other hand, since the lens forming surface of the fixed mold 30 may be a flat surface, it is not necessary to use a mirror piece, and the entire PL surface (mold matching surface) 33 is a flat surface.

  As shown in FIG. 4, the movable mold 40 for molding the front member 12 has a lens molding space 41 at the center, and a mirror piece 43 is fitted in the center thereof, and the tip of the mirror piece 43 is inserted. The aspherical surface 43a provided on the surface forms the injection surface 12a when the front member 12 is molded. On the other hand, since the lens forming surface of the fixed mold 50 may be a flat surface, it is not necessary to use a mirror piece, and the entire PL surface 53 is a flat surface.

  Next, a method for adjusting the eccentricity when the rear member 11 and the front member 12 formed by the mold configured as described above are integrated with a UV curing adhesive will be described. As shown in FIG. 5, the eccentricity adjusting device 60 sets in advance such that the laser beam 63 is incident on a fixed point on the area sensor 64 before placing the lens 10. Thereafter, the rear member 11 is placed on the eccentricity adjusting device 60. A UV curable adhesive is applied onto the split surface 11b of the rear member 11 placed on the eccentricity adjusting device 60. The front member 12 is placed on the rear member 11 so that the UV curable adhesive adheres to the divided surface 12b with the divided surface 12b facing downward.

  After the rear member 11 and the front member 12 are placed on the eccentricity adjusting device 60, the adjustment tool 62 is set on the front member 12. At this time, in order to prevent the front member 12 from floating from the rear member 11, a weight (not shown) having a hole in the center may be placed on the front member 12.

  Next, the laser beam 63 is incident from above the eccentricity adjusting device 60, and the adjustment tool 62 is adjusted so that the incident position of the laser beam 63 with respect to the area sensor 64 disposed inside comes to a fixed point. Adjust the lead. Since the adjustment tool 62 is disposed on all sides of the test object (in this case, the front member 12), the position of the test object can be moved.

  The laser beam 63 is set in advance so as to be incident on a fixed point on the area sensor 64. When the front member 12 is eccentric with respect to the rear member 11, the laser beam 63 is emitted from the area sensor 64. Incident at a position outside the fixed point. Therefore, if the incident position of the laser beam 63 and the coordinates of the fixed point are displayed on the monitor by the output from the area sensor 64, the eccentric amount of the front member 12 is shifted from the fixed point coordinates of the incident position of the laser beam 63. It is only necessary to move the front member 12 by pressing the outer periphery of the front member 12 with the adjusting tool 62 so that they match.

  It is also possible to perform automation by calculating based on the amount and direction of deviation between the output from the area sensor 64 and the fixed point coordinates and automatically controlling the movement of the adjustment tool 62. Further, a parallel beam from a collimator is used in place of the laser beam 63, a screen is disposed at the same position in place of the area sensor 64, and the front member is observed while observing the coincidence between the incident position of the parallel beam and a fixed point using a microscope. It is also possible to perform twelve eccentric adjustments. Further, the direction of the light beam is reversed, the chart and an illumination system that illuminates the chart from the lower side of the chart are arranged instead of the area sensor 64, the screen is arranged above, and the chart image projected on the screen is displayed. It is also possible to adjust the eccentricity while observing.

  After the eccentric adjustment of the front member 12, the UV curable adhesive is irradiated with ultraviolet rays from above the front member 12 while the adjustment tool 62 is fixed at the adjusted position. When the UV curing adhesive is cured, the front member 12 is fixed to the rear member 11, and one lens 10 is completed here. Thereafter, the adjustment tool 62 is removed. Even if an external force such as vibration is applied in the process of curing the adhesive, the adjustment tool 62 is fixed at the adjusted position until the curing of the adhesive is completed. There is no deviation from the position.

  The lens 10 in the embodiment has been described with respect to the case where the split surfaces 11b and 12b of the rear member 11 and the front member 12 are flat, but depending on the shape of the entrance surface 11a or the exit surface 12a of the lens 10, it is split in a plane. There are times when you can't. In this case, it is desirable to divide the lens 10 into a rear member and a front member by a spherical surface that is divided at a substantially central portion in the thickness direction.

  As shown in FIG. 6, the lens 70 is formed by bonding a rear member 71 having a concave aspherical entrance surface 71a and a front member 72 having a convex aspherical exit surface 72a by using a UV curing adhesive. It is what. The rear member 71 has a convex dividing surface 71b on the front member 72 side, and the front member 72 has a concave dividing surface 72b on the rear member 71 side. Both the dividing surface 71b and the dividing surface 72b have the same R spherical shape. The rear member 71 and the front member 72 are each molded by an injection mold. The rear member 71 includes a flange portion 71f.

  In the above embodiment, the case where the dividing surface is a plane or a spherical surface has been described. However, the shape of the dividing surface is not limited to this, and any shape may be used. However, it must be possible to move the front member on the rear member to adjust the eccentricity.

  In the above embodiment, the front member and the rear member are integrated by applying a UV curable adhesive to the entire surface of the dividing surface. However, the present invention is not limited to this, and how is the front member and the rear member integrated? Various methods may be used. For example, as shown in FIG. 7, the lens 80 may be constituted by a front member 82 and a rear member 71 in which a flat surface portion 82d is provided at the peripheral edge of the dividing surface 82b. By bringing the flat portion 82d into contact with the rear member 71, a slight gap 82c is formed between the dividing surface 71b and the dividing surface 82b, and oil is filled therein. Even if there are scratches on the surfaces of the dividing surface 71b and the dividing surface 82b, the influence is erased by the oil. The flat portion 82d is bonded to the rear member 71 with a UV curable adhesive, and the oil is sealed.

  In the above embodiment, the flange portions 11f and 71f are provided on the rear members 11 and 71. However, the flange portions 11f and 71f may be provided on the front members 12, 72 and 82, or may be provided on both the front member and the rear member. Alternatively, there may be no flange portion at all.

  In the above-described embodiment, a double-sided aspheric surface used as a projection lens of a projector has been described. However, the method for manufacturing a lens according to the present invention may be employed even when the first surface (incident surface) is a spherical surface, for example. In addition, the center of the second surface (exit surface), which is an aspherical surface, can be easily adjusted to the center of the first surface.

It is a perspective view when the lens by this invention is halved. It is a perspective view of a fixed mold and a movable mold for injection molding a rear member. It is a fragmentary sectional view of the metal mold | die of the part which shape | molds a rear member. It is a fragmentary sectional view of the metal mold | die of the part which shape | molds a front member. It is explanatory drawing of eccentric adjustment of a front member with an eccentricity adjustment apparatus. It is sectional drawing of another lens. It is sectional drawing of another lens.

Explanation of symbols

10, 70, 80 Lens 11, 71 Rear member 11a Incident surface 11b, 12b, 71b, 72b, 82b Dividing surface 12, 72, 82 Front member 12a Ejection surface 20, 40 Movable type 23, 43 Mirror surface piece 30, 50 Fixed type

Claims (4)

In a double-sided aspheric plastic lens having an entrance surface and an exit surface,
A split surface that splits the front member having the exit surface and the rear member having the entrance surface between the entrance surface and the exit surface, and molding the front member and the rear member with the same resin, A double-sided aspherical plastic lens, wherein the front surface and the rear surface of the divided surface are aligned, and the optical axis centers of the entrance surface and the exit surface are made to coincide with each other and then bonded and fixed.   The double-sided aspheric plastic lens according to claim 1, wherein the dividing surface is a flat surface.   The double-sided aspheric plastic lens according to claim 1, wherein the dividing surface is a spherical surface. In a method for manufacturing a double-sided aspheric plastic lens having an entrance surface and an exit surface,
The front member having the exit surface and the rear member having the entrance surface are divided between the entrance surface and the exit surface, and the front member and the rear member are formed of the same resin, and the front member is divided. A method for producing a double-sided aspherical plastic lens, wherein the optical axis centers of the incident surface and the exit surface are matched after the surface and the split surface of the rear member are aligned.

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