Plastic Lenses and Equipment

Abstract

To provide a technique advantageous in improving an optical performance of a plastic lens 1.SOLUTION: A flange surface 21 includes: a horizontal part 31 alienated from a lens surface 11; and an inclined part 32 between the horizontal part 31 and the lens surface 11. The inclined part 32 is an inclined plane inclined to the horizontal part 31. A difference of elevation of the inclined part 32 is 10 μm or more and less than 100 μm, in a Z direction parallel to an optical axis L of the plastic lens 1.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a plastic lens. [Background technology]

[0002] Patent document 1 discloses forming an annular inclined surface on the edge of a plastic lens in order to reduce the ghost phenomenon in which unwanted light is captured in the imaging area by reflecting the unwanted light toward the object side using the inclined surface.

[0003] Patent Document 2 discloses that, in order to improve the stability of lens assembly, the object side surface of the plastic lens includes a flat surface that is bonded to the flat surface of the glass lens, and an inclined surface that is spaced apart from the inclined surface of the glass lens. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-242504 A [Patent Document 2] JP 2020-027283 A Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Documents 1 and 2 do not consider deformation of plastic lenses. When deformation occurs in a plastic lens, the optical performance of the plastic lens deteriorates. The present invention aims to provide a technique that is advantageous for improving the optical performance of a plastic lens. [Means for solving the problem]

[0006] One aspect of the means for solving the above problem is a plastic lens having a lens portion and a flange portion, wherein the lens portion has a first lens surface forming one of a convex shape and a concave shape, and a second lens surface forming the other of the convex shape and the concave shape, the flange portion has a side surface, a first flange surface extending from the side surface to the first lens surface, and a second flange surface extending from the side surface to the second lens surface, the first flange surface having a first portion away from the first lens surface and a second portion between the first portion and the first lens surface, the second portion being an inclined surface inclined with respect to the first portion, and the height difference of the inclined surface in a direction parallel to the optical axis of the plastic lens is 10 μm or more and less than 100 μm. Effect of the Invention

[0007] According to the present invention, it is possible to provide a technique that is advantageous in improving the optical performance of a plastic lens. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic diagram illustrating a plastic lens. [Diagram 2] FIG. 2 is a schematic diagram illustrating a lens unit. [Diagram 3] FIG. 2 is a schematic diagram illustrating a plastic lens. [Figure 4] FIG. 2 is a schematic diagram illustrating a plastic lens. [Diagram 5] FIG. [Figure 6] Schematic diagrams illustrating an embodiment of a plastic lens. [Figure 7] FIG. 1 is a schematic diagram illustrating a comparative example of a plastic lens. [Figure 8] Schematic diagram illustrating the shape of a plastic lens. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description and drawings, common reference numerals are used to designate components common to multiple drawings. Therefore, common components will be described with mutual reference to multiple drawings, and descriptions of components with common reference numerals will be omitted as appropriate.

[0010] Fig. 1 is a diagram illustrating a plastic lens 1 according to this embodiment. Fig. 1(a) is a perspective view of the plastic lens 1 when viewed from the lens surface 11 side, and Fig. 1(b) is a perspective view of the plastic lens 1 when viewed from the lens surface 12 side. Fig. 1(c) is a perspective view of the plastic lens 1 when viewed in cross section along line AB in Figs. 1(a) and (b).

[0011] In Fig. 1, the X direction, Y direction, and Z direction, which are orthogonal to each other, the Φ direction indicating an angle with respect to the X direction in the XY plane, and the θ direction indicating an angle with respect to the XY plane are described. The X direction and the Y direction are directions intersecting the optical axis L of the plastic lens 1, and the X direction and the Y direction in this example are directions perpendicular to the optical axis L of the plastic lens 1. The Z direction is a direction along the optical axis L of the plastic lens 1, and the Z direction in this example can be a direction parallel to the optical axis L. For convenience, the X direction and the Y direction can be called the horizontal direction, and the Z direction can be called the vertical direction, but the position of the plastic lens 1 is arbitrary. In the following description, the coordinate system in the drawings other than Fig. 1 is the same as that in Fig. 1.

[0012] The plastic lens 1 has a lens portion 10 and a flange portion 20. The lens portion 10 has a lens surface 11 having one of a convex shape and a concave shape, and a lens surface 12 having the other of a convex shape and a concave shape. In this example, the lens surface 11 is a convex lens surface having a convex shape, and the lens surface 12 is a concave lens surface having a concave shape. However, the lens surface 11 may be a concave lens surface having a concave shape, and the lens surface 12 may be a convex lens surface having a convex shape. The flange portion 20 is provided so as to surround the lens portion 10. The flange portion 20 has a side surface 23, a flange surface 21 extending from the side surface 23 to the lens surface 11, and a flange surface 22 extending from the side surface 23 to the lens surface 12. Since flange surface 21 is located above flange surface 22 (on the +Z side) in Fig. 1(c), it can also be called an upper flange surface, and since flange surface 22 is located below flange surface 21 (on the -Z side) in Fig. 1(a), it can also be called a lower flange surface. Side surface 23 is provided so as to surround flange portion 20. In Fig. 1(c), side surface 23 can be inclined with respect to the vertical direction (Z direction), but side surface 23 may also be parallel to the optical axis.

[0013] The boundary surface 15 between the lens portion 10 and the flange portion 20 is a surface connecting a boundary line 16 between the lens surface 11 and the flange surface 21, and a boundary line 17 between the lens surface 12 and the flange surface 22. This boundary surface 15 and the boundary lines 16 and 17 do not need to be visualized.

[0014] The thickness Ta of the lens unit 10 can be defined as the distance from the top 110 of the lens surface 11 to the lens surface 12. The thickness Tb of the flange unit 20 can be defined as the distance from the flange surface 21 to the flange surface 22. The distance (thickness Ta) from the top 110 of the lens surface 11 to the lens surface 12 can be equal to or less than twice the distance (thickness Tb) from the flange surface 21 to the flange surface 22 (Ta ≦ 2 × Tb). The distance (thickness Ta) from the top 110 of the lens surface 11 to the lens surface 12 may be smaller than the distance (thickness Tb) from the flange surface 21 to the flange surface 22 (Ta < Tb). The distance (thickness Ta) from the top 110 of the lens surface 11 to the lens surface 12 can be equal to or greater than 1 / 4 of the distance (thickness Tb) from the flange surface 21 to the flange surface 22 (Ta ≧ Tb / 4). The distance (thickness Ta) from the top 110 of the lens surface 11 to the lens surface 12 may be equal to or greater than 1 / 2 of the distance (thickness Tb) from the flange surface 21 to the flange surface 22 (Ta ≧ Tb / 2). The distance (thickness Ta) from the top 110 of the lens surface 11 to the lens surface 12 is, for example, 0.1 to 10 mm, 0.1 to 1 mm for a small-diameter lens, 1 to 5 mm for a medium-diameter lens, and 5 to 10 mm for a large-diameter lens.

[0015] The distance (thickness Ta) from the top 110 of the lens surface 11 to the lens surface 12 can be equal to or less than 1 / 5 of the width W of the plastic lens 1 in the X direction and Y direction perpendicular to the optical axis L of the plastic lens 1 (Ta ≦ W / 5). The distance (thickness Ta) from the top 110 of the lens surface 11 to the lens surface 12 may be equal to or less than 1 / 10 of the width W of the plastic lens 1 in the X direction and Y direction perpendicular to the optical axis L of the plastic lens 1 (Ta ≦ W / 10). The distance (thickness Ta) from the top 110 of the lens surface 11 to the lens surface 12 can be equal to or greater than 1 / 50 of the width W of the plastic lens 1 in the X direction and Y direction perpendicular to the optical axis L of the plastic lens 1 (Ta ≦ W / 50). The width W of the plastic lens 1 in the X direction and Y direction perpendicular to the optical axis L of the plastic lens 1 is, for example, 1 mm to 100 mm, 1 to 10 mm for a small-diameter lens, 10 to 50 mm for a medium-diameter lens, and 50 to 100 mm for a large-diameter lens.

[0016] This embodiment may be characterized in that, as shown in Fig. 1(a), flange surface 21 has a horizontal portion 31 and an inclined portion 32. Also, as shown in Fig. 1(b), this embodiment may be characterized in that flange surface 22 has a horizontal portion 33 and an inclined portion 34. Details of each of these portions will be described later.

[0017] A typical plastic lens 1 is manufactured by injection molding. As shown in Figs. 1(a) and (b), the plastic lens 1 has a gate mark 25 on a side surface 23. The plastic lens 1 can be manufactured by cutting and polishing a solid plastic material, but it is more efficient to manufacture the plastic lens 1 by injection molding. Injection molding uses at least an upper mold (mirror piece) having a mirror surface corresponding to the lens surface 11 and a lower mold having a mirror surface corresponding to the lens surface 12. The upper mold may be formed of a single part having a mirror surface corresponding to the lens surface 11 and a surface corresponding to the flange surface 21. Alternatively, the upper mold may be divided into a part (mirror piece) having a mirror surface corresponding to the lens surface 11 and a part (support piece) having a surface corresponding to the flange surface 21. The lower mold may be formed of a single part having a mirror surface corresponding to the lens surface 12 and a surface corresponding to the flange surface 22. Alternatively, the lower mold may be divided into a part having a mirror surface corresponding to lens surface 12 (mirror piece) and a part having a surface corresponding to flange surface 22 (support piece).

[0018] In the example of the plastic lens 1 shown in FIG. 1(b), the flange portion 20 has at least one (two in this example) protrusion 26 on the flange surface 22 side. The protrusion 26 protrudes downward (in the -Z direction) from a portion of the flange surface 22 surrounding the protrusion 26. The flange portion 20 also has at least one (six in this example) protrusion 27 on the flange surface 22 side. The protrusion 27 protrudes downward (in the -Z direction) from a portion of the flange surface 22 surrounding the protrusion 27. The protrusion height of the protrusion 27 is smaller than the protrusion height of the protrusion 26, and may be less than 1 / 2 or even less than 1 / 4 of the protrusion height of the protrusion 26. The flange portion 20 also has at least one (four in this example) eject pin mark 28 on the flange surface 22 side. At least one of the gate mark 25, the protrusion 26, the protrusion 27, and the eject pin mark 28 may be eliminated.

[0019] A lens unit 8 including a plastic lens 1 and a support part 4 that supports the plastic lens 1 will be described with reference to FIG. 2. In recent years, with the advancement of high performance image sensors and development of communication technology, cameras are being installed in all kinds of devices, and the demand for inexpensive plastic lenses is increasing. There are an increasing number of cases where cameras are installed not only for imaging purposes such as digital cameras, action cameras, and surveillance cameras, but also for detection purposes in automobiles and industrial robots. In addition, cameras in smartphones are becoming increasingly multi-lensed. The lens unit 8 can be incorporated into electronic devices such as cameras and camera modules that include an imaging device (image sensor), and mobile terminals (smartphones, tablets, and laptop computers). The electronic devices can include a signal processing device that processes signals output from the imaging device, and a display device that displays the captured image.

[0020] Alternatively, the lens unit 8 can be incorporated into an optical device (interchangeable lens) that can be attached to a camera body equipped with an image sensor. In addition to the lens unit 8, the interchangeable lens can include an exterior part that houses the lens unit 8 and a mount for attaching the interchangeable lens to a camera body. The interchangeable lens can also include a drive device that drives at least one of the multiple lenses of the lens unit 8 for focusing and zooming. Devices that include the plastic lens 1 are not limited to cameras and interchangeable lenses, but can also be office equipment such as copiers, printers, and scanners, medical equipment such as endoscopes, analytical equipment such as microscopes, industrial equipment such as robots, and transportation equipment such as automobiles, ships, and airplanes.

[0021] Fig. 2(a) is a perspective view of a lens unit 8 in which a plastic lens 1 is incorporated into a support part 4 together with another lens, as viewed from the object side (subject side). Fig. 2(b) is a perspective view of the lens unit 8 as viewed from the image side (sensor side). The plastic lens 1 is located closest to the object side, and a part of the lens surface 11, which is a convex lens surface, is exposed to the outside of the lens unit 8.

[0022] FIG. 2(c) is a cross-sectional view of the EE' line in FIG. 2(b), showing a cross-section of the center of the lens unit 8. Inside the support part 4, the plastic lens 1, lens 2, spacer 5, lens 3, and retaining ring 6 are housed in this order from the object side. The support part 4 in this example is a lens barrel. Multiple plastic lenses are housed inside the lens barrel (support part 4), and an image sensor is assembled on the image side to form an integrated imaging module. The lenses must be fixed to the lens barrel by some method to prevent disassembly. The lenses can be assembled inside the lens barrel with adhesive via the flange. Multiple lenses can be stacked from the image side opening of the lens barrel and sealed together by pressing the retaining ring. The support part 4 and the retaining ring 6 are made of the same plastic material, and are integrated by thermocompression in the final process of assembling the lens unit 8. Therefore, a pressure mark 7 remains at the boundary between the support part 4 and the retaining ring 6, where a soldering iron was pressed from the -Z direction. The lenses are not bonded together, and disassembly is prevented by simply sealing the support part 4 with a presser ring 6. In order to prevent the lens from rattling inside the support part 4, sufficient pressure can be applied during thermocompression bonding to eliminate unnecessary gaps between the lenses. In this manner, the flange portion 20 of the plastic lens 1 can be sandwiched between the support part 4 and another lens 2.

[0023] Although not shown in FIG. 2(c), the protrusion 26 described in FIG. 1 can determine the mounting angle of the plastic lens 1 by fitting into a recess provided in the lens 2 or the support part 4. In order to use the protrusion 26 as such a positioning part, the height of the protrusion 26 can be set to 0.5 mm or more. The lower surface of the protrusion 27 described in FIG. 1 can determine the mounting height of the plastic lens 1 by abutting the lens 2 adjacent to the plastic lens 1. In order to use the protrusion 27 as such a positioning part, the flatness of the lower surface of the protrusion 27 can be set to be higher than the flatness of the portion of the flange surface 22 surrounding the protrusion 27. The height of the protrusion 27 can be 0.1 mm or more. Since the protrusion 27 abuts against the lens 2, a gap corresponding to the height of the protrusion 27 can be generated between the portion of the flange surface 22 surrounding the protrusion 27 and the lens 2. In order to reduce this gap, the protrusion height of the protrusion 27 can be set to less than 0.5 mm.

[0024] FIG. 8(a) shows the design shape of a lens having a convex lens surface and a concave lens surface. If this is to be realized with a plastic lens, the plastic lens actually manufactured may be deformed from the design shape so that the concave lens surface side is narrower than the design shape, as shown in FIG. 8(b). This is because of the asymmetry of one lens surface being convex and the other being concave, and the fact that the thickness of the lens part tends to be thin, making it difficult to increase the rigidity of the lens part. When such a deformed plastic lens is incorporated into the lens unit 8 as shown in FIG. 2, a force is applied from the optical axis direction. Although this force is minute, since the lens is a high-precision part, the deterioration of optical performance due to deformation and distortion cannot be ignored.

[0025] As a result of extensive research, the present inventors have found that the stress in the plastic lens can be controlled by controlling the shape of the flange 20. The shape of the flange 20 will be described in detail below.

[0026] 3 shows four types of shapes of flange surface 21 in the vicinity of boundary line 16. Fig. 3(a) shows type A, Fig. 3(b) shows type B, Fig. 3(c) shows type C, and Fig. 3(d) shows type C.

[0027] In types A, B, C, and D shown in FIG. 3(a) to (d), the flange surface 21 has a horizontal portion 31 away from the lens surface 11 and an inclined portion 32 between the horizontal portion 31 and the lens surface 11. The horizontal portion 31 is a horizontal surface along the X direction or the Y direction (horizontal direction). The inclined portion 32 is an inclined surface inclined with respect to the horizontal portion 31. The inclined portion 32 being inclined means that the angle with respect to the horizontal portion 31 is neither 0 degrees (180 degrees) nor 90 degrees (270 degrees). A typical inclination angle of the inclined portion 32 with respect to the horizontal portion 31 is, for example, 5 to 85 degrees, for example, 30 to 60 degrees, or for example, 40 to 50 degrees. If the inclination angle is too small or too large, the effect of deformation control may be reduced. If the inclination angle is small, the width of the inclined portion 32 in the X and Y directions becomes large, and the width of the flange surface 22 also tends to become large. 3(a) to (d) show a boundary line 41 of the inclined portion 32 on the horizontal portion 31 side.

[0028] 3(a)-(d), the height difference Ha of the inclined portion 32 in the direction parallel to the optical axis L of the plastic lens 1 is less than 100 μm. If the height difference Ha is less than 100 μm, the effect on the overall thickness distribution of the plastic lens 1 is small, and the adverse effect of the inclined portion 32 on the lens precision is small. The height difference Ha is preferably 10 μm or more, and more preferably 30 μm or more.

[0029] 3(a) and 3(b), the inclined portion 32 is inclined in a direction (-θ direction) from the horizontal portion 31 toward the lens surface 12. The inclination direction of types A and B is a direction that reduces the thickness of the flange portion 20, and therefore can generate portions in the flange portion 20 that have locally low mechanical strength.

[0030] 3(c) and (d), inclined portion 32 is inclined in the direction (+θ direction) opposite to the direction (-θ direction) from horizontal portion 31 toward lens surface 12. The inclination direction of types C and D increases the thickness of flange portion 20, so that flange portion 20 can have locally high mechanical strength portions.

[0031] In types A, B, C, and D shown in Fig. 3(a) to (d), the distance between the horizontal portion 31 and the inclined portion 32 is smaller than the height difference Ha of the inclined portion 32. In other types not shown, the distance between the horizontal portion 31 and the inclined portion 32 may be equal to the height difference Ha of the inclined portion 32 or may be larger than the height difference Ha of the inclined portion 32. The distance between the horizontal portion 31 and the inclined portion 32 is preferably less than 100 µm. In types A, B, C, and D, the distance between the horizontal portion 31 and the inclined portion 32 is less than 30 µm. In types A, B, C, and D, the distance between the horizontal portion 31 and the inclined portion 32 may be less than 10 µm, less than 3 µm, less than 1 µm, or 0 µm.

[0032] 3(a) to (d), the distance between inclined portion 32 and lens surface 11 is smaller than the height difference Ha of inclined portion 32. In other types not shown, the distance between inclined portion 32 and lens surface 11 may be equal to or larger than the height difference Ha of inclined portion 32. The distance between inclined portion 32 and lens surface 11 is preferably less than 100 μm.

[0033] In types A and C shown in Figures 3(a) and (c), flange surface 21 has an intermediate portion 36 between inclined portion 32 and lens surface 11. Inclined portion 32 is an inclined surface inclined with respect to intermediate portion 36 of flange surface 21. The distance between inclined portion 32 and lens surface 11 via intermediate portion 36 can be 30 µm or more. Figures 3(a) to (d) show a boundary line 42 on the lens surface 11 side (intermediate portion 36 side) of inclined portion 32.

[0034] Types B and D shown in Figures 3(b) and (d) do not have intermediate portion 36 as in types A and C, and the distance between inclined portion 32 and lens surface 11 is less than 30 µm. In types B and D, the distance between inclined portion 32 and lens surface 11 may be less than 10 µm, less than 3 µm, less than 1 µm, or 0 µm. In Figures 3(b) and (d), the boundary line of inclined portion 32 on the lens surface 11 side is indicated by boundary line 16.

[0035] Fig. 4 shows four types of shapes of flange surface 22 in the vicinity of boundary line 17. Fig. 4(a) shows type E, Fig. 3(b) shows type F, Fig. 3(c) shows type G, and Fig. 3(d) shows type H.

[0036] In types E, F, G, and H shown in Fig. 4(a) to (d), the flange surface 22 has a horizontal portion 33 away from the lens surface 12 and an inclined portion 34 between the horizontal portion 33 and the lens surface 12. The horizontal portion 33 is a horizontal surface along the X direction or the Y direction (horizontal direction). The inclined portion 34 is an inclined surface inclined with respect to the horizontal portion 33. Inclined means that the angle with respect to the horizontal portion 33 is neither 0 degrees (180 degrees) nor 90 degrees (270 degrees). A typical inclination angle of the inclined portion 34 with respect to the horizontal portion 33 is, for example, 5 to 85 degrees, for example, 30 to 60 degrees, or for example, 40 to 50 degrees. If the inclination angle is too small or too large, the effect of deformation control may be reduced. If the inclination angle is small, the width of the inclined portion 34 in the X and Y directions becomes large, and the width of the flange surface 22 also tends to become large. 4(a) to (d) show a boundary line 43 of the inclined portion 34 on the horizontal portion 33 side.

[0037] The horizontal portion 33 is a portion of the flange surface 22 surrounding the protrusion 26, the protruding portion 27, and the eject pin mark 28, which are described in FIG.

[0038] In types E, F, G, and H shown in Figures 4(a) to (d), the height difference Hb of inclined portion 34 in the Z direction parallel to optical axis L of plastic lens 1 is less than 100 µm. If the height difference Hb is less than 100 µm, the effect on the overall thickness distribution of plastic lens 1 is small, and the adverse effect of inclined portion 34 on lens precision is small. The height difference Hb is preferably 10 µm or more, and more preferably 30 µm or more.

[0039] 4(a) and (b), inclined portion 34 is an inclined surface that is inclined in a direction (+θ direction) from horizontal portion 33 toward lens surface 11. The inclination direction of types E and F is a direction that reduces the thickness of flange portion 20, and therefore can generate portions in flange portion 20 that have locally low mechanical strength.

[0040] 4(c) and (d), inclined portion 34 is inclined in the opposite direction (-θ direction) from horizontal portion 33 toward lens surface 11 (+θ direction). The inclination direction of types G and H increases the thickness of flange portion 20, so that flange portion 20 can have locally high mechanical strength portions.

[0041] In types E, F, G, and H shown in Fig. 3(a) to (d), the distance between the horizontal portion 33 and the inclined portion 34 is smaller than the height difference Hb of the inclined portion 34. In other types not shown, the distance between the horizontal portion 33 and the inclined portion 34 may be equal to the height difference Hb of the inclined portion 34 or may be larger than the height difference Hb of the inclined portion 34. The distance between the horizontal portion 33 and the inclined portion 34 is preferably less than 100 µm. In types E, F, G, and H, the distance between the horizontal portion 33 and the inclined portion 34 is less than 30 µm. In types E, F, G, and H, the distance between the horizontal portion 33 and the inclined portion 34 may be less than 10 µm, less than 3 µm, less than 1 µm, or 0 µm.

[0042] 4(b) and (d), the distance between the inclined portion 34 and the lens surface 12 is smaller than the height difference Hb of the inclined portion 34. In other types not shown, the distance between the inclined portion 34 and the lens surface 12 may be equal to the height difference Hb of the inclined portion 34 or may be larger than the height difference Hb of the inclined portion 34. The distance between the inclined portion 34 and the lens surface 12 is preferably less than 100 μm.

[0043] In types E and G shown in Figures 4(a) and (c), flange surface 22 has an intermediate portion 37 between inclined portion 34 and lens surface 12. Inclined portion 34 is an inclined surface inclined with respect to intermediate portion 37 of flange surface 22. The distance between inclined portion 34 and lens surface 12 via intermediate portion 37 can be 30 µm or more. Figures 4(a) to (d) show a boundary line 44 on the lens surface 12 side (intermediate portion 37 side) of inclined portion 34.

[0044] Types F and H shown in Figures 4(b) and (d) do not have intermediate portion 37 as in types E and G, and the distance between inclined portion 34 and lens surface 12 is less than 30 µm. In types F and G, the distance between inclined portion 34 and lens surface 12 may be less than 10 µm, less than 3 µm, less than 1 µm, or 0 µm. In Figures 4(b) and (d), the boundary line of inclined portion 34 on the lens surface 12 side is indicated by boundary line 17.

[0045] In this way, by providing at least one of the inclined portion 32 of the flange surface 21 and the inclined portion 34 of the flange surface 22 on the flange portion 20, the deformation of the plastic lens 1 can be controlled. By concentrating stress on the inclined portions 32 and 34 or dispersing stress from the inclined portions 32 and 34, the deformation of the plastic lens 1 can be concentrated on the flange portion 20, and the deformation can be prevented from reaching the lens portion 10. Which of the types A, B, C, and D is best combined with which of the types E, F, G, and H depends on the shape of the plastic lens 1 before applying these types, so that the shape of the plastic lens 1 can be selected to be a desired shape. The degree of deterioration of the lens shape accuracy changes depending on the size and thickness deviation of the plastic lens 1. When the thickness Ta of the lens portion 10 of the plastic lens 1 is larger, the degree of deterioration of the shape accuracy caused by increasing the height differences Ha and Hb of the inclined portions 32 and 34 tends to be relatively mitigated.

[0046] 1(a) and (b), the inclined portions 32, 34 (inclined surfaces) can be provided so as to surround the optical axis L in a plan view from a direction along the optical axis L (e.g., the Z direction). By providing the inclined portions 32, 34 (inclined surfaces) all around the plastic lens 1 in the circumferential direction (Φ direction) in this manner, uneven distribution of deformation and distortion occurring in the plastic lens 1 can be suppressed compared to a case in which the inclined portions 32, 34 are provided discontinuously in the circumferential direction (Φ direction).

[0047] When manufacturing the plastic lens 1 by injection molding, the inclined surface can be formed mainly by two methods. In the first method (cutting method), a mold having a right-angled portion composed of a horizontal plane and a vertical plane is prepared, and a molded product having a flange portion 20 with the right-angled portion transferred by the horizontal plane and the vertical plane of the mold is molded by the mold. Then, the corners of this molded product are chamfered by cutting to form the inclined surface. The horizontal plane transferred by the mold becomes the horizontal parts 31 and 33, and the inclined surface formed by the cutting becomes the inclined parts 32 and 34. In the second method (transfer method), a mold having a non-right-angled portion composed of a horizontal plane and an inclined surface is prepared, and a molded product having a non-right-angled portion transferred by the horizontal plane and the inclined surface of the mold is molded by the mold. The horizontal plane transferred by the mold becomes the horizontal parts 31 and 33, and the inclined surface transferred by the mold becomes the inclined parts 32 and 34. In this way, the cutting process as in the first method can be omitted, and productivity is improved. In addition, the inclined surface can be used as a draft angle for the mold, which can reduce the mold release resistance when the molded product is removed from the mold during injection molding, thereby improving the yield of mass-produced products.

[0048] The horizontal portion 31 may be formed rougher than the lens surface 11. That is, the lens surface 11 may be a mirror surface, while the horizontal portion 31 may be a rough surface. The inclined portion 32 and the intermediate portion 36 may be rougher than the lens surface 11. That is, the inclined portion 32 and the intermediate portion 36 may be rough surfaces. The horizontal portion 31 may be rougher than the inclined portion 32 and the intermediate portion 36. In this case, the inclined portion 32 and the intermediate portion 36 may be a mirror surface. The inclined portion 32 and the intermediate portion 36 may be rougher than the lens surface 11, and the horizontal portion 31 may be rougher than the inclined portion 32 and the intermediate portion 36. In this way, the surface roughness of the inclined portion 32 may be different from at least one of the surface roughness of the horizontal portion 31 and the surface roughness of the lens surface 11.

[0049] The horizontal portion 33 may be formed rougher than the lens surface 12. That is, the lens surface 12 may be a mirror surface, while the horizontal portion 33 may be a rough surface. The inclined portion 34 and the intermediate portion 37 may be rougher than the lens surface 12. That is, the inclined portion 34 and the intermediate portion 37 may be rough surfaces. The horizontal portion 33 may be rougher than the inclined portion 34 and the intermediate portion 37. In this case, the inclined portion 34 and the intermediate portion 37 may be a mirror surface. The inclined portion 34 and the intermediate portion 37 may be rougher than the lens surface 12, and the horizontal portion 33 may be rougher than the inclined portion 34 and the intermediate portion 37. In this way, the surface roughness of the inclined portion 34 may be different from at least one of the surface roughness of the horizontal portion 33 and the surface roughness of the lens surface 12.

[0050] It is preferable to improve the recognizability of at least any of boundary lines 41, 42, 43, 44, 16, and 17, which are the boundaries between inclined portions 32 and 34. Recognizability here is not limited to visual inspection, but includes visibility using a surface shape measuring device such as an optical microscope, an electron microscope, or a contact microscope. By improving the recognizability of at least any of boundary lines 41, 42, 43, 44, 16, and 17, the accuracy of inspection of plastic lens 1 and assembly of lens unit 8 can be improved.

[0051] 5(a) to (d) show an example of a convex portion 35 for improving the visibility of the boundary line. The convex portion 35 protrudes from both the horizontal portions 31, 33 and the inclined portions 32, 34 adjacent to each other with the boundary lines 41, 42 in between. Alternatively, the convex portion 35 protrudes from both the inclined portions 32, 34 and the intermediate portions 36, 37 adjacent to each other with the boundary lines 43, 44 in between. Alternatively, the convex portion 35 protrudes from both the inclined portions 32, 34 and the lens surfaces 11, 12 adjacent to each other with the boundary lines 16, 17 in between. The height of the convex portion 35 may be less than 10 μm. The height of the convex portion 35 may be 5 μm or less. The height of the convex portion 35 may be 1 μm or more. The width of the convex portion 35 may be less than 30 μm. The width of the convex portion 35 may be 20 μm or less. The width of the convex portion 35 may be 1 μm or more, or may be 3 μm or more.

[0052] Note that, instead of the protrusions 35, recesses for improving the visibility of the boundary line may be provided. The depth of the recesses for improving the visibility of the boundary line may be less than 10 μm and may be 1 μm or more. The width of the recesses for improving the visibility of the boundary line may be less than 30 μm and may be 1 μm or more.

[0053] The convex portion 35 on the flange surface 21 can be provided at least one between the horizontal portion 31 and the inclined portion 32 and between the inclined portion 32 and the lens surface 11. The convex portion 35 between the horizontal portion 31 and the inclined portion 32 can be used as a means for improving the visibility of the boundary line 41. Of the convex portions 35 between the inclined portion 32 and the lens surface 11, the convex portion 35 between the inclined portion 32 and the intermediate portion 36 in types A and C can be used as a means for improving the visibility of the boundary line 42. Of the convex portions 35 between the inclined portion 32 and the lens surface 11, the convex portion 35 between the inclined portion 32 and the lens surface 11 in types B and D can be used as a means for improving the visibility of the boundary line 16.

[0054] The convex portion 35 on the flange surface 22 can be provided at least one between the horizontal portion 33 and the inclined portion 34 and between the inclined portion 34 and the lens surface 12. The convex portion 35 between the horizontal portion 33 and the inclined portion 34 can be used as a means for improving the visibility of the boundary line 43. Of the convex portions 35 between the inclined portion 34 and the lens surface 12, the convex portion 35 between the inclined portion 34 and the intermediate portion 37 in types E and G can be used as a means for improving the visibility of the boundary line 44. Of the convex portions 35 between the inclined portion 34 and the lens surface 11, the convex portion 35 between the inclined portion 34 and the lens surface 11 in types F and H can be used as a means for improving the visibility of the boundary line 17.

[0055] The convex portions 35 can be provided so as to surround the optical axis L in a plan view from a direction (e.g., Z direction) along the optical axis L of the plastic lens 1. By providing the convex portions 35 all around the circumferential direction (Φ direction) of the plastic lens 1 in this way, the effort required to find the convex portions 35 can be reduced, and inspection and assembly can be made more efficient, compared to a case in which the convex portions 35 are provided discontinuously in the circumferential direction (Φ direction).

[0056] The method of forming the convex portion 35 can be formed by cutting so that the convex portion 35 remains near the inclined portion 34 in the cutting method of the above-mentioned method of forming the inclined surface. Also, in the transfer method of the above-mentioned method of forming the inclined surface, the convex portion 35 can be formed by forming a recess corresponding to the convex portion 35 in the mold. The recess corresponding to the convex portion 35 formed in the mold may be provided in the mirror piece or in the holding piece. The recess corresponding to the convex portion 35 formed in the mold may be a recess formed at the boundary between the mirror piece and the holding piece. The convex portion 35 generated by transferring the recess at the dividing boundary of the mold is generally called a dividing line. If the convex portion 35 is formed on the flange surface 21, a recess corresponding to the convex portion 35 may be provided in the upper mold, and if the convex portion 35 is formed on the flange surface 22, a recess corresponding to the convex portion 35 may be provided in the lower mold. EXAMPLES

[0057] Fig. 6(a) is a central cross-sectional view of a plastic lens 1 in an embodiment, in which lens surface 11 is convex, lens surface 12 is concave, and the plastic lens 1 has a flange 20. Fig. 6(b) is an enlarged view of part A in Fig. 6(a). The plastic lens 1 is a small diameter lens, with an outer diameter of 5 mm, a thickness Ta of the lens portion 10 of about 0.4 mm, and a thickness Tb of the flange 20 of 0.8 mm.

[0058] A plastic lens 1 was manufactured by injection molding using a mold having an inclined surface corresponding to the inclined portions 32 and 34 in FIG. 6(a). The shape of the flange surface 21 corresponds to type B shown in FIG. 3(b), and the shape of the flange surface 22 corresponds to type F shown in FIG. 4(b). The height difference Ha of the inclined portion 32 is 30 μm. The inclination angle of the inclined portion 32 is 45 degrees. The height difference Hb of the inclined portion 34 is 30 μm. The inclination angle of the inclined portion 34 is 45 degrees. A convex portion 35 (not shown) indicating the positions of the boundary line 41 and the boundary line 17 was formed by a secant line of the mold. The inclined portion 34 functioned as a draft angle when the plastic lens 1 was removed from the mold during injection molding, and it was also possible to reduce the mold release resistance. Therefore, the lens surface accuracy during mold release was good.

[0059] The pressure applied when assembling lens unit 8 can distort the internal plastic lens 1. However, because plastic lens 1 has locally thin portions due to inclined portions 32, 34, deformation is concentrated at the inclined portions, and deterioration of the surface accuracy of lens portion 10 is suppressed. The lens unit where deformation is concentrated is located outside eyepiece-side aperture 9 of the telescope barrel and outside effective optical area 18, so there is little effect on the optical performance of plastic lens 1. This lens unit was judged to be good in a resolution evaluation using MTF (Modulation Transfer Function) performed after assembly.

[0060] <Comparative Example 1> 7(a) is an enlarged view of flange portion 20 in Comparative Example 1. Flange surfaces 21, 22 were formed only by horizontal portions 31, 33, without providing inclined portions 32, 34. When the lens and lens barrel were assembled in the same manner as in the examples, the plastic lens 1 of Comparative Example 1 did not have a locally thin portion, and therefore the entire lens surface of plastic lens 1 was deformed by external forces during assembly. The resolution evaluation of the lens unit incorporating plastic lens 1 of Comparative Example 1 was determined to be a defective product.

[0061] <Comparative Example 2> 7(b) is an enlarged view of flange portion 20 in comparative example 2. Vertical portions 38, 39 are provided instead of inclined portions 32, 34. Vertical portion 38 has a height difference Hc of 30 μm. Vertical portion 39 has a height difference Hd of 30 μm. Vertical portion 38 causes mold release problems, which deteriorates the lens surface accuracy of plastic lens 1 in comparative example 2, resulting in a lower yield of mass-produced products. The resolution evaluation of the lens unit incorporating plastic lens 1 in comparative example 2 was determined to be defective.

[0062] <Comparative Example 3> FIG. 7(c) is an enlarged view of the flange portion 20 in Comparative Example 3. The height difference Ha of the inclined portion 32 is 130 μm. The height difference Hb of the inclined portion 34 is 130 μm. In the plastic lens 1, there was a large difference in the cooling speed between the lens portion 10 and the flange portion 20 in the mold during injection molding. This difference resulted in a difference in the amount of shrinkage, which increased the amount of deformation of the lens due to shrinkage, resulting in poor lens shape accuracy at the pre-assembly stage compared to the plastic lens 1 shown in the example. The resolution evaluation of the lens unit incorporating the plastic lens 1 of Comparative Example 3 was judged to be a defective product.

[0063] The above-described embodiments can be modified as appropriate without departing from the technical spirit of the present invention. For example, multiple embodiments can be combined. In addition, some features of at least one embodiment can be deleted or replaced. In addition, new features can be added to at least one embodiment.

[0064] The disclosure of this specification includes not only what is explicitly described in this specification, but also all matters that can be understood from this specification and the drawings attached hereto. The disclosure of this specification also includes the complement of each concept described in this specification. In other words, if this specification contains a statement that "A is B," for example, this specification can be said to disclose that "A is not B," even if the statement that "A is not B" is omitted. This is because when a statement that "A is B" is made, it is assumed that the case in which "A is not B" is taken into consideration. [Explanation of symbols]

[0065] 10 Lens section 11 Lens surface 12 Lens Surface 20. Collar 21 Brim surface 22 Brim surface 23 Side 31 Horizontal part 32 Slope section 33 Horizontal part 34 Slope section Height difference Ha Height difference Hb Optical axis L

Claims

1. A plastic lens having a lens portion and a flange portion, The lens portion has a first lens surface having one of a convex shape and a concave shape, the flange portion has a side surface and a first flange surface extending from the side surface to the first lens surface, the first flange surface has a first portion away from the first lens surface and a second portion between the first portion and the first lens surface, the second portion is an inclined surface inclined with respect to the first portion, and a height difference of the inclined surface in a direction parallel to an optical axis of the plastic lens is 10 μm or more and less than 100 μm, A plastic lens, characterized in that the distance between the inclined surface and the first lens surface is less than 100 μm.

2. The plastic lens of claim 1 , wherein the first flange surface has an intermediate portion between the second portion and the first lens surface, and the second portion is an inclined surface inclined with respect to the intermediate portion of the first flange surface.

3. 3. The plastic lens according to claim 1, wherein a convex portion having a height of less than 10 μm is provided at least one of between the first portion and the second portion and between the second portion and the first lens surface.

4. The plastic lens according to claim 3 , wherein the convex portion is provided between the second portion and the first lens surface.

5. The plastic lens according to claim 1 , wherein a surface roughness of the second portion is different from at least one of a surface roughness of the first portion and a surface roughness of the first lens surface.

6. the lens portion further has a second lens surface forming the other of the convex shape and the concave shape, 6. The plastic lens according to claim 1, wherein the flange portion further includes a second flange surface extending from the side surface to the second lens surface.

7. The plastic lens according to claim 6 , wherein the second portion is inclined in a direction from the first portion toward the second lens surface.

8. The plastic lens according to claim 6 or 7, wherein the second portion is inclined in a direction opposite to a direction from the first portion toward the second lens surface.

9. 9. The plastic lens according to claim 6, wherein a first distance from a vertex of the first lens surface to the second lens surface satisfies at least one of the following: a first distance from a vertex of the first lens surface to the second lens surface is equal to or less than twice a second distance from the first flange surface to the second flange surface; and a second distance from the vertex of the first lens surface to the second flange surface is equal to or less than ⅕ of a width of the plastic lens in a direction perpendicular to an optical axis of the plastic lens.

10. 10. The plastic lens according to claim 6, wherein the first lens surface has the convex shape and the second lens surface has the concave shape.

11. the second flange surface has a third portion spaced from the second lens surface and a fourth portion between the first portion and the second lens surface, the fourth portion is an inclined surface inclined with respect to the third portion, A height difference of the fourth portion in a direction parallel to the optical axis is 10 μm or more and less than 100 μm. The plastic lens according to any one of claims 6 to 10.

12. The plastic lens of claim 11 , wherein the fourth portion is inclined in a direction from the first portion toward the first lens surface.

13. The plastic lens of claim 11 , wherein the fourth portion is inclined in a direction opposite to a direction from the third portion toward the first lens surface.

14. The plastic lens according to claim 11 , wherein a distance between the fourth portion and the second lens surface is smaller than the height difference of the fourth portion.

15. The plastic lens of claim 11 , wherein the second flange surface has an intermediate portion between the fourth portion and the second lens surface, and the fourth portion is an inclined surface inclined with respect to the intermediate portion of the second flange surface.

16. 16. The plastic lens according to claim 11, wherein a convex portion having a height and a width of less than 10 μm is provided at least one of between the third portion and the fourth portion and between the fourth portion and the second lens surface.

17. The plastic lens according to claim 16 , wherein the convex portion is provided between the fourth portion and the second lens surface.

18. 18. The plastic lens according to claim 1, wherein the inclined surface is provided so as to surround the optical axis in a plan view from a direction along the optical axis.

19. 17. The plastic lens according to claim 3, wherein the convex portion is provided so as to surround the optical axis in a plan view from a direction along the optical axis.

20. The plastic lens according to claim 6 , wherein the flange portion has a plurality of protrusions on a side of the second flange surface.

21. 21. An apparatus comprising the plastic lens according to any one of claims 1 to 20 and a support part for supporting the plastic lens.

22. 22. The device of claim 21, further comprising a lens separate from the plastic lens, the flange being sandwiched between the support piece and the separate lens.

Images