Lenses, optical devices, imaging devices, electronic devices, and methods for manufacturing lenses

Abstract

When manufacturing high-angle, large-wall thickness lenses using sheet molding, if the elongation of the sheet forming the central part (optical portion) of the lens is inhibited, wrinkle-like surface defects occur. [Solution] A lens containing resin, wherein the central part has a curved surface, and the surface outside the central part has an inflection point, and the surface at the location of the inflection point is rougher than the surface of the central part.

Description

Technical Field

[0001] The present invention relates to a lens, an optical device, an imaging device, an electronic device, and a method for manufacturing a lens.

Background Art

[0002] In recent years, in the smartphone optical system, the sensor size has been increasing, and the number of lenses has been on the rise in order to suppress aberrations. If the number of lenses increases while maintaining the same thickness as conventional lenses, the protrusion amount of the lens unit from the smartphone body will increase. On the other hand, if the thinning of the lens progresses in the future, it is considered that manufacturing will be difficult with conventional injection molding, so manufacturing methods other than injection molding are required.

[0003] Patent Document 1 discloses preparing a preform of a thermoplastic resin and pressing it to form a lens. Patent Document ۲ discloses manufacturing a lens by pressing using a thermoplastic resin sheet.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a lens with high precision and no appearance defects.

Means for Solving the Problems

[0006] A means for solving the above problems is a lens containing resin, having a curved central portion and a surface with an inflection point outside the central portion, wherein the surface at the location of the inflection point is rougher than the surface of the central portion. Also, an optical device comprising an optical system including the above lens and a housing enclosing the optical system. Also, an imaging device comprising an optical system including the above lens and an image sensor that receives light that has passed through the optical system. Also, an electronic device comprising an optical system including the above lens, an image sensor that receives light that has passed through the optical system and a display element that displays an image captured by the image sensor. Also, an electronic device comprising an optical system including the above lens, an image sensor that receives light that has passed through the optical system and a light-emitting element that illuminates an object to be imaged. Furthermore, a method for manufacturing a lens comprising a preparation step of preparing a sheet containing resin, and a molding step of pressing the sheet with a mold to form a lens shape, wherein in the molding step, a first position of the sheet which will be the central part of the lens is pressed with the mold, and then a second position of the sheet which will be outside the central part is pressed with the mold. Furthermore, a mold for pressing a sheet containing resin to form a lens shape, comprising a portion for pressing the first position of the sheet which will be the central part of the lens, and a portion for pressing the second position of the sheet which will be outside the central part, wherein the portion for pressing the first position is configured to protrude more than the portion for pressing the second position. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide lenses without external defects with high precision. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a sheet molding process using a conventional configuration. [Figure 2] This is a schematic diagram illustrating an example of a lens according to the present invention. [Figure 3] This is a schematic diagram of sheet molding in Embodiment 1 of the present invention. [Figure 4] This is a schematic diagram of sheet molding in Embodiment 1 of the present invention. [Figure 5] This is a schematic diagram of sheet molding in Embodiment 2 of the present invention. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the embodiments described below are just one embodiment of the present invention, and the present invention is not limited thereto. Common components will be described with reference to multiple drawings, and components with common reference numerals will be omitted from the description as appropriate. Different items with the same name can be distinguished by adding "item number ○," such as "item number 1," "item number 2," etc.

[0010] When manufacturing lenses with high-angle, large-walled concave surfaces, such as those found in smartphone optics, by pressing a sheet, if the sheet's stretching in the center is inhibited, wrinkle-like surface defects will occur. While the configurations disclosed in Patent Documents 1 and 2 allow for the manufacture of thin-walled lenses by press molding, they are particularly ineffective at suppressing the occurrence of wrinkles in lenses with concave surfaces having a high opening angle and large thickness variation.

[0011] Using Figure 1, a conventional method for manufacturing lenses by sheet molding is explained. A thermoplastic resin sheet 11 is placed between a heated upper mold 12 and a lower mold 13. The upper mold 12 is driven to sandwich the sheet 11, and the sheet 11 is plastically deformed by pressing while heating, and then demolded after a cooling process. The mold is heated, for example, by a heater, and cooled by turning off the heater and passing cooling water through it. With this method, it is possible to form a desired lens shape according to the mold, but the sheet 11 stretches in the part where it interferes with the mold, and twisting occurs in the sheet 11 at the point where the stretches collide. The present invention suppresses the occurrence of twisting and provides a lens without appearance defects.

[0012] <Embodiment> The lens according to the present invention is a lens containing resin, having a curved central portion and a surface with an inflection point outside the central portion, characterized in that the surface at the location of the inflection point is rougher than the surface of the central portion. Figure 2 is a diagram showing an example of the lens according to the present invention. The central portion 21 has a curved (concave) surface and an inflection point 22 is located outside the central portion 21. In the embodiments described herein, the inflection point can be a point where the sign of the curvature of the lens surface changes (including points where it changes from positive to negative, positive to 0, and negative to 0). In the embodiments described herein, the central portion of the lens is the optical portion (optically effective region), but the central portion and the optical portion do not necessarily have to coincide perfectly; they only need to coincide to the extent that the effects of the present invention can be obtained.

[0013] The present invention relates to a method for manufacturing a lens, comprising a preparation step of preparing a sheet containing resin, and a molding step of pressing the sheet with a mold to form a lens shape, wherein the molding step is characterized in that, after pressing a first position of the sheet which will be the central part of the lens with the mold, a second position of the sheet which will be outside the central part with the mold is pressed with the mold.

[0014] The press molding of the lens in the first embodiment will be described with reference to Figures 3(a) to 3(d). First, a sheet containing resin is prepared in the preparation step. Figure 3 is a schematic diagram showing a thermoplastic resin sheet 31 placed between the upper mold 32 and the lower mold 33. For the material of the sheet 31, for example, a cycloolefin resin can be used. In addition to thermoplastic resin, the sheet 31 can be made of any material that can be deformed by the pressure of the mold and satisfies the optical properties, such as a thermosetting resin.

[0015] The mold that presses the sheet 31 has a portion that presses a first position 31-1 of the sheet 31, which is the central part of the lens, and a portion that presses a second position 31-2 of the sheet 31, which is located outside the central part, and the portion that presses the first position 31-1 can be configured to protrude more than the portion that presses the second position 31-2. Furthermore, the portion that presses the first position can be configured so that the amount of protrusion decreases as the pressing progresses. In addition, the portion that presses the first position can be held via an elastic body. By using a mold as described above, molding can be performed efficiently without separating the process of pressing the first position and the process of pressing the second position. In this embodiment, the piece 34 that forms the central part of the lens is connected to the upper mold 32 via a spring. The upper mold 32 and the lower mold 33 are heated, for example, using a heater.

[0016] In the stage before the start of the molding process, the spring is extended as shown in Figure 3(a), so as the upper mold 32 descends during the molding process, the piece 34 makes contact with the sheet 31 in advance as shown in Figure 3(b). Subsequently, as the spring compresses and the upper mold 32 descends, as shown in Figure 3(c), the sheet 31 and the upper mold 32 come into contact at the second position, which is outside the first position. Finally, as shown in Figure 3(d), the piece 34 comes into contact with the upper mold 32, stopping the movement of the piece 34 by the spring and forming the desired lens shape. After the molding process, the mold can be demolded by cooling it with cooling water.

[0017] In conventional press molding, there was a concern that the elongation of the sheet at the first position corresponding to the optical part would be hindered by the elongation of the sheet at the second position corresponding to the non-optical part outside the optical part, resulting in distortion of the sheet at the first position. In this embodiment, since the die 34 presses the sheet 31 in advance, the elongation of the sheet at the first position is not hindered, and even if elongation occurs at the second position outside the first position and the elongations interfere with each other, the distortion of the sheet 31 is formed at the second position. In other words, the distortion generated at the first position can be stretched toward the second position during molding. As a result, it is possible to make a lens in which the surface at the inflection point is rougher than the surface at the center.

[0018] This is particularly advantageous when forming a shape in which the curved surface of the central portion is, for example, a concave surface. For example, it can be formed into a shape of a lens having a concave surface at the central portion and a lens thickness at the central portion of 0.3 mm or less. Further, when the central portion of the lens to be formed has a convex surface, it is particularly advantageous when forming, for example, a sheet having a convex surface into a shape of a lens having a gentler (smaller curvature) convex surface.

[0019] The size of the lens is not particularly limited, but when forming a small lens by using the present invention, it can be precisely formed. The size of the lens can be, for example, 10 mm or more and 20 mm or less in diameter. As the shape of the lens, the lens thickness at the central portion can be made thinner than the lens thickness at a position outside the central portion (for example, the inflection point). Further, the thickness can be such that the lens thickness at the central portion is 0.3 mm or less.

[0020] Further, after the forming step, a separating step of separating the shape into a lens may be further provided. As shown in FIG. 4(a), a large number of pieces 34 are provided, and the upper die 32 and the lower die 33 are made into an integral structure to form a large number of lenses at once. After the upper die 32 is lifted and released, a punch die 35 having a structure of cutting the sheet 31 in place of the upper die 32 as shown in FIG. 4(b) is opposed to the lower die 33 and lowered as shown in FIG. 4(c) to separate the shape into a lens. Since a cut mark may remain at the time of separation, a protruding shape may exist over the entire circumference at the outer peripheral end of the lens.

[0021] Next, the press molding of the lens in the second embodiment will be described with reference to Figures 5(a) to (c). In this embodiment, the sheet 41 used has a first position 41-1 corresponding to the optical part (center) that is thicker than the outer part (second position 41-2), as shown in Figure 5(a). As the sheet 41 is sandwiched between the upper die 42 and the lower die 43 as shown in Figure 5(b), the first position 41-1 of the sheet is pressed against the upper die 42 first. Further lowering of the upper die 42 forms the desired lens shape as shown in Figure 5(c). In this embodiment, since the first position of the sheet that forms the central part (optical part) of the lens is pressed against the mold first, the sheet stretches to the second position, preventing the formation of distortion on the central part of the lens, similar to the first embodiment. The other configurations and functions are the same as in the first embodiment.

[0022] An optical device can be constructed by enclosing an optical system including a lens according to the present invention in a housing. Furthermore, an imaging device can be constructed by combining an optical system including a lens according to the present invention with an image sensor that receives light passing through the optical system. Additionally, an electronic device such as a smartphone can be constructed by combining an optical system including a lens according to the present invention with an image sensor that receives light passing through the optical system and a display element that displays an image captured by the image sensor. Moreover, an electronic device such as an endoscope can be constructed by combining an optical system including a lens according to the present invention with an image sensor that receives light passing through the optical system and a light-emitting element that illuminates an object to be imaged.

[0023] The present invention is not limited to the embodiments described above, and many modifications are possible within the technical concept of the present invention. Furthermore, the effects described in the embodiments are merely a list of the most preferred effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments.

[0024] The embodiments described above can be modified as appropriate without departing from the technical concept. For example, multiple embodiments can be combined. In addition, some aspects of at least one embodiment can be deleted or replaced.

[0025] Furthermore, new matters may be added to at least one embodiment. The disclosures of this specification include not only those explicitly stated herein, but also all matters that can be understood from this specification and the accompanying drawings.

[0026] This embodiment includes the following configurations and methods. (Composition 1) A lens containing resin, The surface has a curved central portion and an inflection point on the outside of the central portion. A lens characterized in that the surface at the location of the inflection point is rougher than the surface of the central part. (Configuration 2) The lens according to configuration 1, characterized in that the curved surface in the central part is a concave surface. (Composition 3) The lens according to configuration 1 or 2, characterized in that a protruding shape exists around the entire circumference of the outer edge of the lens. (Composition 4) The lens according to any one of configurations 1 to 3, characterized in that the resin is a thermoplastic resin. (Composition 5) The lens according to any one of configurations 1 to 4, characterized in that the thickness of the lens in the central portion is thinner than the thickness of the lens at the inflection point. (Composition 6) The lens according to any one of configurations 1 to 5, characterized in that the thickness of the lens in the central portion is 0.3 mm or less. (Composition 7) The lens according to any one of configurations 1 to 6, characterized in that the resin is a cycloolefin resin. (Composition 8) An optical system including the lens described in any of configurations 1 to 7, A housing containing the aforementioned optical system, An optical device equipped with the following features. (Composition 9) An optical system including the lens described in any of configurations 1 to 7, An image sensor that receives light that has passed through the optical system, An imaging device equipped with the following features. (Composition 10) An optical system including the lens described in any of configurations 1 to 7, An image sensor that receives light that has passed through the optical system, A display element that displays the image captured by the image sensor, Electronic devices equipped with these features. (Composition 11) An optical system including the lens described in any one of items 1 to 7, An image sensor that receives light that has passed through the optical system, A light-emitting element that illuminates the object to be imaged, Electronic devices equipped with these features. (Method 12) A method for manufacturing a lens, comprising a preparation step of preparing a sheet containing resin, and a molding step of pressing the sheet with a mold to form a lens shape, The manufacturing method is characterized in that, in the molding step, a first position of the sheet which is the central part of the lens is pressed with the mold, and then a second position of the sheet which is outside the central part is pressed with the mold. (Method 13) The manufacturing method according to method 12, characterized in that the molding step is performed while heating the sheet. (Method 14) The manufacturing method according to method 12 or 13, characterized in that the molding step involves molding the lens so that the thickness of the lens in the central part is thinner than the thickness of the lens in positions outside the central part. (Method 15) The manufacturing method according to any one of methods 12 to 14, characterized in that the molding step involves molding the lens into a shape in which the central part has a concave surface and the thickness of the lens in the central part is 0.3 mm or less. (Method 16) The manufacturing method according to any one of methods 12 to 15, further comprising a separation step of separating the lens shape after the molding step. (Composition 17) A mold for pressing a resin-containing sheet into a lens shape, The lens has a portion that presses on a first position of the sheet which is the central part of the lens, and a portion that presses on a second position of the sheet which is located outside the central part. A mold characterized in that the portion that presses the first position protrudes more than the portion that presses the second position. (Composition 18) The type according to configuration 17, characterized in that the portion that presses the first position is configured such that the amount of protrusion decreases as the pressing progresses. (Composition 19) The type according to configuration 18, wherein the part that presses the first position is held via an elastic body. [Explanation of Symbols]

[0027] 31...Sheet, 32...Upper mold, 33...Lower mold, 34...Die, 35...Punch mold

Claims

1. A lens containing resin, The surface has a curved central portion and an inflection point on the outside of the central portion. A lens characterized in that the surface at the location of the inflection point is rougher than the surface of the central part.

2. The lens according to claim 1, characterized in that the curved surface in the central part is a concave surface.

3. The lens according to claim 1, characterized in that a protruding shape is present around the entire circumference of the outer edge of the lens.

4. The lens according to claim 1, characterized in that the resin is a thermoplastic resin.

5. The lens according to claim 1, characterized in that the thickness of the lens in the central portion is thinner than the thickness of the lens at the inflection point.

6. The lens according to claim 1, characterized in that the thickness of the lens in the central portion is 0.3 mm or less.

7. The lens according to claim 1, characterized in that the resin is a cycloolefin resin.

8. An optical system including a lens according to any one of claims 1 to 7, A housing containing the aforementioned optical system, An optical device equipped with the following features.

9. An optical system including a lens according to any one of claims 1 to 7, An image sensor that receives light that has passed through the optical system, An imaging device equipped with the following features.

10. An optical system including a lens according to any one of claims 1 to 7, An image sensor that receives light that has passed through the optical system, A display element that displays the image captured by the image sensor, Electronic devices equipped with the following features.

11. An optical system including a lens according to any one of claims 1 to 7, An image sensor that receives light that has passed through the optical system, A light-emitting element that illuminates the object to be imaged, Electronic devices equipped with the following features.

12. A method for manufacturing a lens, comprising a preparation step of preparing a sheet containing resin, and a molding step of pressing the sheet with a mold to form a lens shape, The manufacturing method is characterized in that, in the molding step, a first position of the sheet which is the central part of the lens is pressed with the mold, and then a second position of the sheet which is outside the central part is pressed with the mold.

13. The manufacturing method according to claim 12, characterized in that the molding step is performed while heating the sheet.

14. The manufacturing method according to claim 12, characterized in that the molding step involves molding the lens so that the thickness of the lens in the central part is thinner than the thickness of the lens in positions outside the central part.

15. The manufacturing method according to claim 12, characterized in that the molding step involves molding the lens into a shape in which the central portion has a concave surface and the thickness of the lens in the central portion is 0.3 mm or less.

16. The manufacturing method according to claim 12, further comprising a separation step of separating the lens shape after the molding step.

17. A mold for pressing a resin-containing sheet into a lens shape, The lens has a portion that presses on a first position of the sheet which is the central part of the lens, and a portion that presses on a second position of the sheet which is located outside the central part. A mold characterized in that the portion that presses the first position protrudes more than the portion that presses the second position.

18. The type according to claim 17, characterized in that the portion that presses the first position is configured such that the amount of protrusion decreases as the pressing progresses.

19. The mold according to claim 18, wherein the part that presses the first position is held via an elastic body.

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