Lens unit

Abstract

To prevent deformation of a plastic lens due to resilience and repulsion of an O ring.SOLUTION: Provided is a lens unit comprising a first lens which is a resin lens, and a lens holder for holding the first lens. The first lens has a cylindrical rib protruding to the image side, and the rib is formed concentrically with the optical axis on the outside of the effective diameter of the image side surface of the first lens, and the O ring is attached to the outer circumferential surface of the rib. The O ring is sandwiched between the outer circumferential surface of the rib and the inner circumferential surface of the lens holder, and a deformation preventing part for blocking the deformation of the rib and being in contact with the inner circumferential surface of the rib is provided in the lens holder.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a lens unit, and more particularly to a seal structure for a lens unit. [Background technology]

[0002] Patent Document 1 below discloses a lens unit in which an O-ring is compressed in the radial direction by the outer peripheral surface of a plastic lens and the inner peripheral surface of a lens holder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-54798 Summary of the Invention [Problem to be solved by the invention]

[0004] Plastic lenses are less hard than glass lenses and are more susceptible to scratches. If an O-ring is placed between the bottom surface (image side) of the plastic lens and the top surface (object side) of the lens holder, and then the lens surface is pressed down with a jig and crimped in place, there is a risk of scratches on the lens surface. Therefore, a structure in which the O-ring is compressed between the outer surface of the lens and the inner surface of the holder is generally used to seal plastic lenses. However, plastic lenses are more susceptible to deformation than glass lenses, and the restoring and repulsive forces of the O-ring tightening the lens can distort the shape of the lens.

[0005] In view of the above problems, the problem that the present invention aims to solve is to prevent deformation of the plastic lens due to the restoring force and repulsive force of the O-ring. [Means for solving the problem]

[0006] In order to solve the above problem, the lens unit of the present invention comprises a first lens which is a resin lens, and a lens holder which holds the first lens, wherein the first lens has a cylindrical rib protruding toward the image side, the rib being formed concentrically with the optical axis outside the effective diameter of the image side of the first lens, an O-ring being attached to the outer peripheral surface of the rib, and the O-ring being sandwiched between the outer peripheral surface of the rib and the inner peripheral surface of the lens holder, and a deformation prevention portion being provided within the lens holder which contacts the inner peripheral surface of the rib and prevents deformation of the rib.

[0007] By supporting the rib that is fastened to the O-ring from the inside with the deformation prevention part, distortion of the first lens, which is a plastic lens, can be reduced.

[0008] Preferably, the inner peripheral surface of the rib is provided with a first inclined surface that is inclined radially outward from the object side toward the image side, and the surface of the deformation prevention part facing the first inclined surface is provided with a second inclined surface that is a surface of a complementary shape that fits with the first inclined surface. In this case, it is more preferable that the position of the first lens in the optical axis direction is determined by the first inclined surface coming into contact with the second inclined surface. By fitting the rib and the deformation prevention part together at their inclined surfaces, it is possible to eliminate any gap between the rib and the deformation prevention part (i.e., room for deformation) and to tightly fit them from the beginning.

[0009] Furthermore, the length of the rib in the optical axis direction is preferably 1.5 times or less the wire diameter of the O-ring, because the longer the rib, the more easily its tip portion is deformed.

[0010] Furthermore, it is preferable that the deformation prevention portion faces the inner peripheral surface of the rib at the position of the O-ring in the optical axis direction. By supporting the portion of the rib that is directly subjected to the restoring force and repulsive force of the O-ring with the deformation prevention portion, deformation of the rib can be more effectively prevented.

[0011] Preferably, the first lens has a flange-shaped portion that extends radially outward beyond the rib, and the O-ring is attached to a base end portion of the rib. By attaching the O-ring to the most rigid portion of the rib, deformation of the rib can be more effectively prevented.

[0012] The lens unit of the present invention further includes a second lens disposed closer to the image side than the first lens, the deformation prevention portion being a cylindrical portion made of resin, the second lens being fixed by crimping to the object-side end of the deformation prevention portion, and the object-side end of the deformation prevention portion preferably being thinner than the remaining portion of the deformation prevention portion or having a notch or cutout formed on its circumferential surface. The deformation prevention portion of the present invention is a support portion having sufficient rigidity to prevent deformation of the rib, and is therefore formed thicker and larger than a support portion that simply holds the second lens. In other words, the deformation prevention portion requires additional measures to crimp the second lens. Therefore, by intentionally thinning only the end of the deformation prevention portion or providing a notch or cutout in that end, it is possible to achieve both the rigidity to prevent deformation of the rib and the ease of crimping the second lens.

[0013] The first lens may be coated with an anti-scratch coating, an anti-reflection coating, or a water-repellent coating on at least its object-side surface. According to the present invention, deformation of the first lens is prevented, thereby preventing cracks and peeling of the surface coating that accompany such deformation. [Effects of the Invention]

[0014] In this way, the lens unit of the present invention can prevent deformation of the plastic lens due to the restoring force and repulsive force of the O-ring. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a side cross-sectional view showing the internal structure of the lens unit 50. [Figure 2]3A and 3B are diagrams showing a sealing structure of the lens unit 50. FIG. [Figure 3] 4 is a schematic diagram showing the structure of a second crimping portion 26. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of a lens unit of the present invention will be described below with reference to the drawings. The lens unit 50 described below is a small lens assembly that can be incorporated into various devices. The front lens of the lens unit 50 is made of plastic, and an O-ring is attached to its outer periphery to ensure airtightness within the unit. The lens unit 50 is characterized by having a deformation prevention portion that supports from the inside the portion of the front lens that is fastened by the O-ring, thereby preventing deformation of the front lens. This feature and its accompanying features will be described below based on an embodiment.

[0017] <Configuration overview> FIG. 1 is a side cross-sectional view showing the internal structure of lens unit 50. As shown in FIG. 1, lens unit 50 is composed of multiple lenses arranged from the object side to the image side, and lens holder 20 that holds these multiple lenses. The vertical line L1-L2 shown in FIG. 1 indicates the optical axis direction, with L1 being the object side and L2 being the image side. In the following description, "radial direction" and "horizontal" refer to directions perpendicular to the optical axis direction L1-L2.

[0018] The first lens 10, which is the lens closest to the object among the lenses held in the lens holder 20, is a lens with negative power, with a convex curved surface on the object side and a concave curved surface on the image side L2. The second lens 41 is a lens located on the image side of the first lens 10, has a smaller lens diameter than the first lens 10, and has negative power. On the image side of the second lens 41, in this order, are a third lens 43 with positive power, a fourth lens 45 with negative power, and a fifth lens 46 with positive power. The fourth lens 45 and the fifth lens 46 form a cemented lens with positive power. A light-shielding sheet 42 is disposed between the second lens 41 and the third lens 43, and an aperture 44 is disposed between the third lens 43 and the fourth lens 45. An infrared filter 47 is disposed on the image side of the fifth lens 46. These lenses form a reverse telephoto (so-called retrofocus) single-focus wide-angle lens consisting of four groups and five lenses. These lenses are made of plastic because of their ease of processing and economical efficiency.

[0019] Lens holder 20 is a lens holder made of resin that constitutes a lens barrel. Lens holder 20 has a double-cylinder structure consisting of an outer cylinder 21 and an inner cylinder 22, which are connected by a connecting portion 23 provided near the object-side opening of inner cylinder 22. First lens 10 is held by outer cylinder 21 of lens holder 20, and other lenses and filters are held by inner cylinder 22.

[0020] The first lens 10 and the second lens 41 are fixed to the lens holder 20 by thermal caulking at their peripheral edges to position them and prevent them from coming off. More specifically, the peripheral edge of the first lens 10 is thermally caulked by a first caulking portion 25 provided at the object-side end of the outer tube 21, and the peripheral edge of the second lens 41 is thermally caulked by a second caulking portion 26 provided at the object-side end of the inner tube 22.

[0021] A cylindrical rib formed concentrically with the optical axis is provided on the image side surface of the first lens 10 outside its effective diameter. Rib 11 protrudes toward the image side, and an O-ring 30 is attached to its outer peripheral surface. The O-ring is compressed radially by the outer peripheral surface of rib 11 and the inner peripheral surface of outer barrel 21, sealing the lens unit 50. In addition, the object side surface of first lens 10 is coated with an anti-scratch film (a so-called hard coat), an anti-reflection film (a so-called AR coat), and a water-repellent or hydrophilic film, in that order.

[0022] The lens configuration and use, lens holder structure, lens power, lens surface shape, and the like of the lens unit of the present invention are not limited to the embodiment of lens unit 50. As long as first lens 10 is a plastic lens and the lens unit is provided with rib 11 fastened to O-ring 30 and a deformation prevention portion described below, other configurations and structures may be changed as desired.

[0023] <Seal structure> Figure 2 is a diagram showing the sealing structure of the lens unit 50. Figure 2(a) is an enlarged view of the area surrounded by the dashed line in Figure 1, and Figure 2(b) is a schematic diagram showing a modified example of the sealing structure of this embodiment. The sealing structure of the lens unit 50 will be described below with reference to Figure 2.

[0024] As described above, the lens unit 50 of this embodiment includes a first lens 10, which is a resin front lens, and a resin lens holder 20 that holds multiple lenses, including the first lens 10. The first lens 10 has a cylindrical rib 11 that protrudes toward the image side, and an O-ring 30 is attached to the outer peripheral surface 11b of the rib 11. The O-ring 30 is radially sandwiched between the outer peripheral surface 11b of the rib 11 and the inner peripheral surface 21a of the outer tube 21 of the lens holder 20. In other words, the rib 11 is constantly fastened by the restoring force of the O-ring 30, which is stretched when the lens is attached. Furthermore, when the rib 11 is compressed between the lens holder 20 and the O-ring 30, the O-ring 30 is also pressed by its repulsive force. Plastic lenses are more easily deformed than glass lenses, and the restoring and repulsive forces of the O-ring 30 tightening the lens may distort its shape. Therefore, the lens unit 50 includes a deformation prevention portion 24 that prevents the rib 11 from deforming.

[0025] The deformation prevention portion 24 in this embodiment is a part of the lens holder 20, and is a cylindrical portion that comes into contact with the inner peripheral surface 11a of the rib 11. As will be described later, the deformation prevention portion 24 in this embodiment also serves as a support portion for the second lens 41. The lens unit 50 prevents distortion of the first lens 10, which is a plastic lens, by supporting the rib 11, which is fastened to the O-ring 30, from its inside with the deformation prevention portion 24. Note that the deformation prevention portion 24 may be prepared as a component separate from the lens holder 20.

[0026] As shown in FIG. 2A, the inner peripheral surface 11a of the rib 11 in this embodiment forms a first inclined surface that is inclined radially outward from the object side toward the image side. The outer peripheral surface 24a of the deformation prevention portion 24, which faces the inner peripheral surface 11a of the rib 11, forms a second inclined surface that is a surface of a complementary shape that fits with the first inclined surface. In this embodiment, the inner peripheral surface 11a of the rib 11 is the first inclined surface as a whole, and the outer peripheral surface 24a of the deformation prevention portion 24 facing it is also the second inclined surface as a whole. The position of the first lens 10 in the optical axis direction is determined by the contact of the inner peripheral surface 11a (first inclined surface) of the rib 11 with the outer peripheral surface 24a (second inclined surface) of the deformation prevention portion 24. In this way, the lens unit 50 of this embodiment positions the first lens 10 in the optical axis direction by fitting the rib 11 and the deformation prevention portion 24 together, thereby tightly fitting them together. In other words, the gap between the rib 11 and the deformation prevention portion 24, that is, the room for deformation of the first lens 10, is eliminated from the beginning of assembly.

[0027] Furthermore, in the lens unit 50 of this embodiment, the length of the rib 11 in the optical axis direction is approximately the same as the wire diameter of the O-ring 30. Therefore, the O-ring 30 is necessarily attached to the base end, which is the end on the root side (object side) of the rib 11. The first lens 10 of this embodiment also has a flange portion 12, which is a brim-shaped portion that extends radially outward from the position of the rib 11. The flange portion 12 facilitates positioning of the O-ring 30 and prevents misalignment of the O-ring 30. The deformation prevention portion 24 contacts the inner circumferential surface 11a of the rib 11 at the position of the O-ring 30 in the optical axis direction. In this way, in the lens unit 50 of this embodiment, the O-ring 30 is attached to the most rigid portion of the rib 11, i.e., its base portion. Furthermore, the deformation prevention portion 24 supports from the inside the portion that directly receives the restoring force and repulsive force of the O-ring 30, thereby more effectively preventing deformation of the rib 11, i.e., distortion of the first lens 10.

[0028] The method of fitting the rib 11 and the deformation prevention portion 24 is not limited to the embodiment of the lens holder 50 of this embodiment. For example, the first and second inclined surfaces may be provided on parts of the inner and outer peripheral surfaces 11a and 24a, which are the opposing surfaces of the rib 11 and the deformation prevention portion 24. Furthermore, as shown in FIG. 2(b), the inner and outer surfaces of the rib 11 may be vertical. The length of the rib 11 in the optical axis direction is also arbitrary, but considering its rigidity, it is preferable that the length be approximately 1.5 times the wire diameter of the O-ring 30. Furthermore, the positioning of the first lens 10 in the optical axis direction may be performed by placing its flange portion 12 on the mounting surface 21b, which is a horizontal surface provided on the outer tube 21 of the lens holder 20.

[0029] In this way, in lens unit 50 of this embodiment, rib 11 of first lens 10 is supported from the inside by deformation prevention portion 24, thereby preventing deformation of first lens 10 due to the restoring force and repulsive force of O-ring 30. This also prevents cracking and peeling of the hard coating or the like applied to first lens 10.

[0030] <Structure of the second crimping part> 3 is a schematic diagram showing the structure of the second crimping portion 26. As described above, the second lens 41 of the lens unit 50 is thermally crimped by the second crimping portion 26, which is part of the deformation prevention portion 24. The deformation prevention portion 24 is a support portion having enough rigidity to prevent deformation of the rib 11. Therefore, it is formed to be thicker and larger than a support portion that simply holds the second lens 41. In other words, the deformation prevention portion 24 requires additional measures to crimp and fix the second lens 41.

[0031] As shown in Fig. 3(a), the second crimping portion 26 in this embodiment is formed to be stepped thinner than the other portions of the deformation prevention portion 24. This can also be considered as a cutout portion 28 shown by the dashed line in Fig. 3(a). Alternatively, as shown in Fig. 3(b), a notch 29 may be formed in the second crimping portion 26. This allows the deformation prevention portion 24 to achieve both the rigidity required to prevent deformation of the rib 11 and the ease with which the second lens 41 can be crimped.

[0032] <Other> The present technology can be configured as follows. (1) a first lens which is a resin lens; a lens holder that holds the first lens, the first lens has a cylindrical rib protruding toward the image side, the rib is formed concentrically with the optical axis on the image side surface of the first lens outside the effective diameter, an O-ring is attached to the outer peripheral surface of the rib, and the O-ring is sandwiched between the outer peripheral surface of the rib and the inner peripheral surface of the lens holder; a deformation prevention portion is provided in the lens holder, the deformation prevention portion being in contact with an inner peripheral surface of the rib to prevent the rib from being deformed; Lens unit. (2) a first inclined surface that is a surface inclined radially outward from the object side toward the image side is provided on an inner peripheral surface of the rib; A second inclined surface is provided on a surface of the deformation prevention part facing the first inclined surface, the second inclined surface being a surface of a complementary shape that fits with the first inclined surface. The lens unit according to (1). (3) The position of the first lens in the optical axis direction is determined by the first inclined surface coming into contact with the second inclined surface. A lens unit according to (1) or (2). (4) The length of the rib in the optical axis direction is 1.5 times or less the wire diameter of the O-ring. A lens unit according to any one of (1) to (3). (5) the deformation prevention portion faces the inner peripheral surface of the rib at a position of the O-ring in the optical axis direction; A lens unit according to any one of (1) to (4). (6) the first lens has a flange-like portion that extends radially outward beyond the rib, The O-ring is attached to the base end portion, which is the end portion on the base side of the rib. (5) The lens unit described above. (7) a second lens disposed closer to the image side than the first lens; the deformation prevention portion is a cylindrical portion made of resin, the second lens is fixed by caulking to an object-side end of the deformation prevention part, The object-side end of the deformation prevention part has a thickness thinner than other parts of the deformation prevention part, or has a notch or cut on its circumferential surface. A lens unit according to any one of (1) to (6). (8) The first lens is coated with an anti-scratch film, an anti-reflection film, or a water-repellent film on at least its object-side surface. A lens unit according to any one of (1) to (7).

[0033] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0034] 10: first lens, 11: rib, 11a: inner peripheral surface of rib (first inclined surface), 11b: outer peripheral surface of rib, 12: flange portion, 20: lens holder, 21: outer barrel, 21a: inner peripheral surface of outer barrel, 21b: mounting surface, 22: inner barrel, 23: connecting portion, 24: deformation prevention portion, 24a: outer peripheral surface of deformation prevention portion (second inclined surface), 25: first crimping portion, 26: second crimping portion, 28: notch portion, 29: notch, 30: O-ring, 41: second lens, 42: light-shielding sheet, 43: third lens, 44: aperture, 45: fourth lens, 46: fifth lens, 47: infrared filter, 50: lens unit, L1: object side, L2: image side

Claims

1. a first lens that is a resin lens; a lens holder that holds the first lens, the first lens has a cylindrical rib protruding toward the image side, the rib is formed concentrically with the optical axis on the image side surface of the first lens outside the effective diameter, an O-ring is attached to the outer peripheral surface of the rib, and the O-ring is sandwiched between the outer peripheral surface of the rib and the inner peripheral surface of the lens holder; a deformation prevention portion is provided in the lens holder, the deformation prevention portion being in contact with an inner peripheral surface of the rib to prevent the rib from being deformed; Lens unit.

2. a first inclined surface that is a surface inclined radially outward from the object side toward the image side is provided on an inner peripheral surface of the rib; a second inclined surface, which is a surface having a complementary shape that fits with the first inclined surface, is provided on a surface of the deformation prevention portion that faces the first inclined surface; The lens unit according to claim 1 .

3. the first inclined surface contacts the second inclined surface, and the position of the first lens in the optical axis direction is determined by the contact. The lens unit according to claim 2 .

4. The length of the rib in the optical axis direction is 1.5 times or less the wire diameter of the O-ring. The lens unit according to claim 1 .

5. the deformation prevention portion faces the inner peripheral surface of the rib at a position of the O-ring in the optical axis direction; The lens unit according to claim 1 .

6. the first lens has a flange-like portion that extends radially outward beyond the rib, The O-ring is attached to a base end portion, which is an end portion on the base side of the rib. The lens unit according to claim 5 .

7. a second lens disposed closer to the image side than the first lens; the deformation prevention portion is a cylindrical portion made of resin, the second lens is fixed by caulking to an object-side end of the deformation prevention part, The object-side end of the deformation prevention part has a thickness thinner than other parts of the deformation prevention part, or has a notch or cut on its circumferential surface. The lens unit according to claim 1 .

8. The first lens is coated with an anti-scratch film, an anti-reflection film, a water-repellent film, or a hydrophilic film on at least its object-side surface. The lens unit according to claim 1 .

Images