lens unit

Abstract

Provided is a lens unit capable of suppressing blurring of a first lens by optimizing a holding force when a wide-angle lens is held in a lens barrel. A lens unit (1) includes a lens barrel (20) that holds a first lens (11), a second lens (12), and a plurality of lenses, and an O-ring (310) disposed between the first lens (11) and the second lens (12). If a first holding force when the second lens (12) is fitted in a first portion (221) is f1, the number of lens pieces of the second lens (12) and the plurality of lenses is C, a third holding force that is a sum of the first holding force and a second holding force when the plurality of lenses is fitted in a second portion (222) is f2, an elastic force of the O-ring (310) is f3, and a fourth holding force of the first barrel portion (21) that holds the first lens (11) is f4, the lens unit (1) satisfies the following conditional expression: f1xC < f2 < f3 < f4.

Description

TECHNICAL FIELD

[0001] The present application relates to a lens unit that holds a plurality of lenses in a lens barrel. BACKGROUND

[0002] In an imaging device mounted in a vehicle or a monitoring camera, a lens unit that houses a plurality of lenses in a lens holder is used. In this lens unit, a lens surface of a first lens on the object side closest to the object is exposed to the outside from the barrel.

[0003] Such a lens unit is described, for example, in Patent Literature 1. In this document, a first lens and a plurality of lenses including a second lens disposed on the image side of the first lens are housed in a resin-made barrel. The barrel has a first housing portion that houses the first lens and a second housing portion that houses the plurality of lenses. An elastic member is disposed between a flange portion of the first lens and a flange portion of the second lens. The first lens is stopped in the first housing portion by heat staking, and the plurality of lenses are press-fitted in the second housing portion. The elastic member is compressed between the flange portion of the first lens and the flange portion of the second lens in a state where the first lens and the second lens do not abut each other. Thereby, the air tightness of the inside of the lens unit is kept constant.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2020-154123 SUMMARY

[0007] Here, in the above-described lens unit, in a case where the holding force of the first housing portion that holds the first lens, the elastic force when the elastic member is compressed, and the holding force of the second housing portion that holds the plurality of lenses are not appropriate, respectively, if the lens unit is used for a long time, moisture can possibly intrude into the inside of the lens holder through the elastic member. However, in the above-described document, this force relationship is not specifically described.

[0008] In view of the above problems, an object of the present application is to provide a lens unit that can suppress blurring of a first lens by optimizing the holding force when a plurality of lenses are held in a barrel.

[0009] To solve the above problems, the lens unit of the present application is characterized by comprising: a first lens disposed at a position closest to an object along an optical axis; a second lens disposed on an image side of the first lens; a plurality of lenses disposed on an image side of the second lens; a lens barrel holding the first lens, the second lens, and the plurality of lenses; and a first annular elastic member disposed between the first lens and the second lens, the lens barrel including: a first barrel portion holding the first lens; a second barrel portion holding the second lens and the plurality of lenses at a position closer to a radial inner side than the first barrel portion; and a positioning step portion abutting against an image side lens disposed at a position closest to the image side among the plurality of lenses on the image side, the second barrel portion including: a first tubular portion holding the second lens; and a second tubular portion holding the plurality of lenses, the first lens being held to the first barrel portion by caulking an object side end portion of the first barrel portion, the second lens being held to the first portion by fitting with the first portion, the plurality of lenses being held to the second portion by fitting with the second portion, the first elastic member being compressed between the first lens and the second lens to a degree that the first lens and the second lens do not abut against each other, a first holding force when the second lens is fitted to the first portion being f1, a number of lens pieces of the second lens and the plurality of lenses being C, a third holding force being a sum of the first holding force and a second holding force when the plurality of lenses are fitted to the second portion being f2, an elastic force of the first elastic member being f3, and a fourth holding force by which the first barrel portion holds the first lens being f4, the following conditional expression being satisfied.

[0010] f1xC < f2 < f3 < f4 (1)

[0011] In the present application, the first elastic member is compressed between the first lens and the second lens to a degree that the first lens and the second lens do not abut against each other. Therefore, compared with a case where the first lens and the second lens abut against each other, it is easy to manage the compression amount of the first elastic member. As a result, it is easy to improve the air tightness inside the lens barrel, and therefore, it is possible to suppress blurring of a lens surface on the image side of the first lens. In addition, since the first lens and the second lens do not abut against each other, when the first lens is held to the first barrel portion, it is not easy to directly apply a large force to the second lens and the plurality of lenses by the compression of the first elastic member. Therefore, when the first lens is held to the first barrel portion, it is possible to suppress breakage of the second lens and the subsequent lenses.

[0012] In addition, in the present application, in a case where the fourth holding force f4 is greater than the elastic force f3, even if the lens unit is used for a long time, the first lens does not fall off from the first barrel portion due to the elastic force f3 of the first elastic member. As a result, even if the lens unit is used for a long time, the moisture that has passed through the first elastic member can be suppressed from entering the inside of the lens unit.

[0013] In addition, in a case where the elastic force f3 is greater than the third holding force f2, when the first lens is held to the first barrel portion by riveting, the image side lens can be pressed to the positioning step portion by the third holding force f2 via the second lens or the like. As a result, the image side lens can be reliably positioned by the positioning step portion.

[0014] Furthermore, in a case where the third holding force f2 is greater than the first holding force f1 x the lens piece number C, the first holding force f1 is smaller than an average holding force obtained by dividing the second holding force when the plurality of lenses are fitted to the second portion by the lens piece number C. Therefore, when the first lens is held to the first barrel portion by riveting, a large force is not easily applied to the second lens, and thus the second lens is not easily deformed. As a result, the first elastic member can be uniformly in close contact between the first lens and the second lens, and thus, even if the lens unit is used for a long time, the moisture that has passed through the first elastic member can be suppressed from entering the inside of the lens holder.

[0015] In the present application, it is preferable that a plurality of first ribs that position the second lens in the radial direction be provided on the inner circumferential surface of the first portion at a plurality of portions in the circumferential direction. In this way, even in a case where deformation due to the outer shape of the lens barrel is likely to occur, the generation of center shift of the second lens due to deformation of the first portion can be suppressed by the first ribs.

[0016] In the present application, it is preferable that a plurality of second ribs that position the plurality of lenses in the radial direction be provided on the inner circumferential surface of the second portion at a plurality of portions in the circumferential direction. In this way, even in a case where deformation due to the outer shape of the lens barrel is likely to occur, the generation of center shift of the plurality of lenses due to deformation of the second portion can be suppressed by the second ribs.

[0017] In the present application, it is preferable that the number of the first ribs be smaller than the number of the second ribs. In this way, the first holding force f1 when the second lens is fitted to the first portion is easily made smaller than the average holding force obtained by dividing the second holding force when the plurality of lenses are fitted to the second portion by the lens piece number C.

[0018] In the present application, it is preferable that the first elastic member overlap the positioning step portion in the optical axis direction. In this way, the force in the optical axis direction when the first lens compresses the first elastic member is concentrated on the positioning step portion. Thus, when the operation of mounting the first lens is performed, the deformation of the lens barrel can be suppressed.

[0019] In the present application, it is preferable that the first lens has a first lens portion and a first annular portion that surrounds a portion of the first lens portion, the lens barrel has an abutting surface portion that abuts against the first annular portion from the image side between the first barrel portion and the second barrel portion, the abutting surface portion has an annular groove portion that is recessed toward the image side, and an annular second elastic member that is compressed between the first annular portion and the groove portion is disposed in the groove portion. In this way, it is easier to ensure the air tightness between the first lens and the second lens.

[0020] Effects of Invention

[0021] In the present application, since the condition formula (1) is satisfied, the holding force when the lens is held in the lens barrel can be optimized. As a result, the air tightness between the first lens and the second lens can be ensured, and thus the lens surface on the image side of the first lens can be prevented from being blurred. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a cross-sectional view of a lens unit to which the present application is applied.

[0023] Figure 2 is an exploded perspective view of the lens unit.

[0024] Figure 3 is a cross-sectional view of a lens barrel.

[0025] Figure 4 is a plan view of the lens barrel as viewed from the object side. DETAILED DESCRIPTION

[0026] Embodiments of the present application will be described with reference to the accompanying drawings. In the drawings referred to in the following description, the number and scale of components are made different in size so as to be recognizable on the drawings. In the following description, the optical axis L direction in which the optical axis L extends is described with La on the object side and Lb on the image side.

[0027] Structure of Lens Unit

[0028] Figure 1 is a cross-sectional view of a lens unit to which the present application is applied. Figure 2 is an exploded perspective view of the lens unit. The lens unit 1 of the present embodiment is used for an optical device such as an image pickup device. The lens unit 1 has substantially the same structure around the optical axis L. Figure 1 The lens unit 1 shown has a wide-angle lens 10 in which a plurality of lenses are disposed in the optical axis L direction and a lens barrel 20 that holds the wide-angle lens 10 on the inner side. An image pickup element is provided on the image side Lb of the lens barrel 20. The image pickup element is a CMOS or the like.

[0029] (Wide-angle lens)

[0030] like Figure 1 and Figure 2 As shown, the wide-angle lens 10 has, for example, a lens structure of 6 elements in 5 groups. In this embodiment, the wide-angle lens 10 includes: a first lens 11 disposed closest to the object side La; a second lens 12 disposed on the image side Lb of the first lens 11; and a plurality of lenses disposed on the image side Lb of the second lens 12. More specifically, the wide-angle lens 10 from the object side La to the image side Lb includes a first lens 11 with negative optical power, a second lens 12 with negative optical power, a third lens 13 with positive optical power, a fourth lens 14 with positive optical power, and a conjoined lens 18 (a fifth lens 15 and a sixth lens 16) with positive optical power. The plurality of lenses are composed of the third lens 13 to the conjoined lens 18.

[0031] The first lens 11 is a glass lens or a plastic lens. The first lens 11 is a concave-convex lens. The first lens surface 111 on the object side La of the first lens 11 is a convex surface protruding towards the object side La, and the second lens surface 112 on the image side Lb is a concave surface recessed towards the object side La. The first lens 11 includes a first lens portion 113 and a first annular portion 114 surrounding the first lens portion 113. The first lens surface 111 and the second lens surface 112 constitute the first lens portion 113. The flange surface 115 of the first annular portion 114 facing the image side Lb is located radially outward of the second lens surface 112.

[0032] The second lens 12 is a plastic lens. The first lens surface 121 on the object side La of the second lens 12 is a convex curved surface protruding towards the object side La, and the second lens surface 122 on the image side Lb is a concave curved surface recessed towards the object side La. The second lens 12 includes a second lens portion 123 and a second annular portion 124, which surrounds the second lens portion 123 and has a gate mark G1 remaining on its outer peripheral surface. The first lens surface 121 and the second lens surface 122 constitute the second lens portion 123. The outer shape of the second annular portion 124 is circular in the optical axis L direction. The gate mark G1 is formed during resin molding of the second lens 12. The gate mark G1 protrudes slightly radially outward from the outer peripheral surface of the second annular portion 124.

[0033] The flange surface 125 of the second annular portion 124 facing the object side La is located radially outward of the first lens surface 121. The flange surface 126 of the second annular portion 124 facing the image side Lb is located radially outward of the second lens surface 122. Furthermore, the second annular portion 124 includes an annular stepped portion 127 protruding towards the object side La. The annular stepped portion 127 positions the first elastic member 31 radially.

[0034] The third lens 13 is a plastic lens. The first lens face 131 of the object side La of the third lens 13 is a convex curved face protruding toward the object side La, and the second lens face 132 of the image side Lb is a concave curved face recessed toward the object side La. The third lens 13 has a third lens portion 133 and a third annular portion 134 which surrounds the third lens portion 133 and in which a portion of the flat face portion 134a of the outer peripheral face has a gate mark G2 remaining. The first lens face 131 and the second lens face 132 constitute the third lens portion 133. The outer shape of the third annular portion 134 is a D shape in the direction of the optical axis L. The gate mark G2 is formed when the second lens 12 is resin molded. The gate mark G2 slightly protrudes from the flat face portion 134a toward the radial direction outside. At this time, the gate mark G2 is located inside an imaginary circle formed by the outer shape of the third annular portion 134. The flange face 135 of the third annular portion 134 toward the object side La is located radially outside the first lens face 131. The flange face 136 of the third annular portion 134 toward the image side Lb is located radially outside the second lens face 132.

[0035] The fourth lens 14 is a glass lens. The joint lens 18 is a joint lens of the fifth lens 15 which is a plastic lens having a negative optical power and the sixth lens 16 which is a plastic lens having a positive optical power. The outer shape of the fifth lens 15 is a D shape in the direction of the optical axis L. On the flat face portion 15a of the outer peripheral face of the fifth lens 15, a gate mark G3 slightly protruding toward the radial direction outside remains. The gate mark G3 is located inside an imaginary circle formed by the outer shape of the fifth lens 15. The outer shape of the sixth lens 16 is a D shape in the direction of the optical axis L. On the flat face portion 16a of the outer peripheral face of the sixth lens 16, a gate mark G4 slightly protruding toward the radial direction outside remains. The gate mark G4 is located inside an imaginary circle formed by the outer shape of the sixth lens 16.

[0036] The lens unit 1 has the circular ring-shaped light shield 2 between the second lens 12 and the third lens 13, and has the circular ring-shaped diaphragm 3 between the fourth lens 14 and the fifth lens 15.

[0037] The outer diameter of the first lens 11 is larger than the outer diameters of the second lens 12, the third lens 13, the fourth lens 14, and the joint lens 18. The outer diameters of the second lens 12, the third lens 13, and the joint lens 18 are substantially equal, and in the joint lens 18, the outer shape of the fifth lens 15 is larger than that of the sixth lens 16. The outer diameter of the fourth lens 14 is smaller than the outer diameters of the second lens 12 and the like.

[0038] (lens barrel)

[0039] Figure 3 is a sectional view of the lens barrel. Figure 4is a plan view of the lens barrel as viewed from the object side. The lens barrel 20 is made of resin. As the material of the lens barrel 20, crystalline plastic (polyethylene, polyamide, polytetrafluoroethylene) excellent in weather resistance, amorphous plastic (polycarbonate or the like) low in moisture absorption, or the like is used. The lens barrel 20 is in a cylindrical shape. As shown in Figures 1 to 4

[0040] In addition, the lens barrel 20 includes an abutment surface portion 24 connecting the first barrel portion 21 and the second barrel portion 22, and a positioning step portion 25 extending from the inner peripheral surface of the second barrel portion 22 to the radial inner side.

[0041] The first barrel portion 21 is in a cylindrical shape, and surrounds the outer peripheral surface of the first lens 11. A riveting portion 211 that fixes the first lens 11 is provided at the end portion of the object side La of the first barrel portion 21. The inner diameter dimension of the first barrel portion 21 is slightly larger than the outer diameter dimension of the first lens 11.

[0042] The abutment surface portion 24 is an annular surface portion toward the object side La. The abutment surface portion 24 abuts against the flange surface 115 of the first annular portion 114 from the image side Lb. The abutment surface portion 24 includes an annular groove portion 241 recessed toward the image side Lb. The second elastic member 32 is disposed in the groove portion 241.

[0043] The second barrel portion 22 is in a cylindrical shape. The inner diameter of the second barrel portion 22 slightly decreases toward the image side Lb. The second barrel portion 22 includes a first portion 221 that holds the second lens 12, and a second portion 222 that holds a plurality of lenses. The first portion 221 surrounds the outer peripheral surface of the lens of the second lens 12. A recessed portion 223 is provided on the inner peripheral surface of the first portion 221 in such a manner that the open end faces the object side La. The recessed portion 223 is also a gate mark receiving recessed portion that receives the gate mark G1. In the present embodiment, the recessed portion 223 is provided at four places at equal intervals in the circumferential direction.

[0044] A plurality of first ribs 224 are provided on the inner peripheral surface of the first portion 221 in the circumferential direction. The first ribs 224 protrude toward the radial inner side, and extend in the optical axis L direction. The first ribs 224 position the second lens 12 in the radial direction when the second lens 12 is pressed into the first portion 221. In the present embodiment, the first ribs 224 are provided at four places at equal intervals in the circumferential direction.

[0045] ​The second portion 222 surrounds the outer peripheral surface of the plurality of lenses. A plurality of second ribs 225 are provided on the inner peripheral surface of the second portion 222 in the circumferential direction. The second ribs 225 project toward the radially inner side and extend in the optical axis L direction. The second ribs 225 position the plurality of lenses in the radial direction when the plurality of lenses are pressed into the second portion 222. In the present embodiment, the second ribs 225 are provided at 12 places at equal intervals in the circumferential direction. In addition, the second ribs 225 are disposed at positions that do not overlap the first ribs 224 in the optical axis L direction.

[0046] The positioning step portion 25 abuts against the engagement lens 18 disposed at the most image side (image side lens) from the image side Lb. The positioning step portion 25 has a projection portion 251 that projects toward the radially inner side at the end portion on the image side Lb.

[0047] (Fixing of wide-angle lens)

[0048] Next, the fixing of the wide-angle lens 10 will be described. First, the engagement lens 18 is pressed into the second barrel portion 22 from the second lens 12. The engagement lens 18 is positioned in the optical axis L direction by the flange portion 150 of the fifth lens 15 abutting against the positioning step portion 25 from the object side La. The fourth lens 14 is held by the holder 4, and the holder 4 abuts against the flange portion 150 of the fifth lens from the object side La. The third circular ring portion 134 of the third lens 13 abuts against the holder 4 from the object side La with the diaphragm 3 interposed therebetween. The second lens 12 is pressed into the first portion 221 with the gate mark G1 positioned inside the recessed portion 223. The second circular ring portion 124 of the second lens 12 abuts against the third circular ring portion 134 of the third lens 13 from the object side La with the diaphragm 2 interposed therebetween. At this time, the flange surface 135 of the third circular ring portion 134 abuts against the flange surface 126 of the second circular ring portion 124 with the diaphragm 2 interposed therebetween, and is positioned at a position that is on the object side La from the bottom surface 226 of the image side Lb of the recessed portion 223.

[0049] Here, in the present embodiment, the recessed portion 223 is provided at 4 places at equal intervals in the circumferential direction. Therefore, when the second lens 12 is pressed into the first portion 221, in the case where the center of the second lens 12 deviates from the optical axis L, the center of the second lens 12 can be made to coincide with the optical axis L by rotating the second lens 12 90° with respect to the first portion 221 each time around the optical axis L. After the center of the second lens 12 is made to coincide with the optical axis L, the second lens 12 is pressed into the first portion 221 with the gate mark G1 positioned inside the recessed portion 223.

[0050] The first lens is inserted into the interior of the first cylindrical portion 21. The first lens 11 is restricted from moving toward the object side La by being covered from the object side La by the riveting portion 211. As a result, the first lens 11 is held inside the first cylindrical portion 21. At this time, the flange surface 115 of the first annular portion 114 abuts against the abutting surface 24 from the object side La, thereby positioning the first lens 11 in the optical axis L direction.

[0051] A first elastic member 31 is provided between the first annular portion 114 of the first lens 11 and the second annular portion 124 of the second lens 12. In this embodiment, the first elastic member 31 is an O-ring 310. The O-ring 310 is disposed on the outer periphery of the annular step portion 127. The O-ring 310 is radially positioned by abutting the annular step portion 127 with its inner peripheral portion. When viewed from the optical axis L direction, the O-ring 310 overlaps with the positioning step portion 25. The O-ring 310 is in close contact with the flange surface 115 of the first lens 11 and the flange surface 125 of the second lens 12 when it is elastically deformed along the optical axis L direction. At this time, the first lens 11 and the second lens 12 are in a state where they do not abut against each other.

[0052] like Figure 1 As shown, a second elastic member 32 is provided on the outer side of the O-ring 310, between the flange surface 115 of the first lens 11 and the abutment surface 24. The second elastic member 32 is the O-ring 320. The O-ring 320 is disposed in the groove 241. The O-ring 320 is in close contact with the flange surface 115 of the first lens 11 and the bottom surface of the groove 241 when it is elastically deformed along the optical axis L.

[0053] Here, if the first holding force when the second lens 12 is fitted into the first part 221 is set as f1, the number of lens elements of the second lens 12 and the plurality of lenses is set as C, the sum of the first holding force and the second holding force when the plurality of lenses are fitted into the second part 222, i.e., the third holding force, is set as f2, the elastic force of the O-ring 310 is set as f3, and the fourth holding force of the first cylindrical part 21 holding the first lens 11 is set as f4, then the following condition (1) is satisfied.

[0054] f1×C<f2<f3<f4(1)

[0055] When the fourth holding force f4 of the first barrel 21 holding the first lens 11 is greater than the elastic force f3 of the O-ring 310, even if the lens unit 1 is used for a long time, the first lens 11 will not fall off from the first barrel 21 due to the elastic force f3 of the O-ring 310. As a result, even if the lens unit 1 is used for a long time, it is possible to prevent moisture passing through the O-ring 310 from entering the interior of the lens unit 1.

[0056] Further, in a case where the elastic force f3 is greater than a third retaining force f2 that is a sum of the first retaining force fl when the second lens 12 is fitted in the first portion 221 and the second retaining force when the plurality of lenses are fitted in the second portion 222, the joint lens 18 can be pressed against the positioning step portion 25 via the second lens 12 or the like by the third retaining force f2 when the first lens 11 is retained to the first barrel portion 21 by riveting. As a result, the joint lens 18 can be reliably positioned by the positioning step portion 25.

[0057] Further, in a case where the third retaining force f2 is greater than the first retaining force fl x the number of lens pieces C, the first retaining force fl is smaller than an average retaining force obtained by dividing the second retaining force when the plurality of lenses are fitted in the second portion 222 by the number of lens pieces C. Therefore, when the first lens 11 is retained to the first barrel portion 21 by riveting, it is difficult to apply a large force to the second lens 12, and thus the second lens 12 is less likely to be deformed. As a result, the O-ring 310 can be uniformly in close contact between the first lens 11 and the second lens 12, and thus even if the lens unit 1 is used for a long time, the intrusion of moisture that has passed through the O-ring 310 into the inside of the lens unit 1 can be suppressed.

[0058] In the present embodiment, the first retaining force fl when the second lens 12 is fitted in the first portion 221 is 3 N. The second lens 12 and the plurality of lenses are the second lens 12, the third lens 13, the fourth lens, and the joint lens 18, and the number of lens pieces C is 4 pieces. The third retaining force f2 that is a sum of the first retaining force fl and the second retaining force when the plurality of lenses are fitted in the second portion 222 is 20 N. The elastic force f3 of the O-ring 310 is 30 N. The fourth retaining force f4 with which the first barrel portion 21 retains the first lens 11 is 250 N. Therefore, the condition condition formula (1) is satisfied.

[0059] (EFFECTS)

[0060] In the present embodiment, the first elastic member 31 is compressed between the first circular ring portion 114 and the second circular ring portion 124 to a degree that the first lens 11 and the second lens 12 do not abut on each other. Therefore, compared to a case where the first lens 11 and the second lens 12 abut on each other, it is easy to manage the compression amount of the first elastic member 31. As a result, it is easy to improve the air tightness inside the lens barrel 20, and thus the blurring of the lens surface on the image side of the first lens 11 can be suppressed. In addition, since the first lens 11 and the second lens 12 do not abut on each other, when the first lens 11 is retained to the first barrel portion 21, it is difficult to directly apply a large force to the second lens 12 and the plurality of lenses due to the compression of the first elastic member 31. Therefore, when the first lens 11 is retained to the first barrel portion 21, the breakage of the second lens 12 and the subsequent lenses can be suppressed.

[0061] In the present embodiment, if the first retaining force when the second lens 12 is fitted in the first portion 221 is denoted as f1, the number of lens pieces of the second lens 12 and the plurality of lenses is denoted as C, the third retaining force which is the sum of the first retaining force and the second retaining force when the plurality of lenses is fitted in the second portion 222 is denoted as f2, the elastic force of the O-ring 310 is denoted as f3, and the fourth retaining force with which the first barrel portion 21 retains the first lens 11 is denoted as f4, the following conditional expression (1) is satisfied.

[0062] f1 x C < f2 < f3 < f4 (1)

[0063] In the present embodiment, the fourth retaining force f4 with which the first barrel portion 21 retains the first lens 11 is greater than the elastic force f3 of the O-ring 310, and thus, even if the lens unit 1 is used for a long time, the first lens 11 does not fall off from the first barrel portion 21 due to the elastic force f3 of the O-ring 310. As a result, even if the lens unit 1 is used for a long time, the intrusion of moisture that has passed through the O-ring 310 into the inside of the lens unit 1 can be suppressed.

[0064] In addition, the elastic force f3 is greater than the third retaining force f2 which is the sum of the first retaining force f1 when the second lens 12 is fitted in the first portion 221 and the second retaining force when the plurality of lenses is fitted in the second portion 222, and thus, when the first lens 11 is retained in the first barrel portion 21 by riveting, the joining lens 18 can be pressed against the positioning step portion 25 via the second lens 12 or the like by the third retaining force f2. As a result, the joining lens 18 can be reliably positioned by the positioning step portion 25.

[0065] Furthermore, since the third retaining force f2 is greater than the first retaining force f1 x the number of lens pieces C, the first retaining force f1 is smaller than the average retaining force obtained by dividing the second retaining force when the plurality of lenses is fitted in the second portion 222 by the number of lens pieces C. Thus, when the first lens 11 is retained in the first barrel portion 21 by riveting, a large force is not easily applied to the second lens 12, and thus, the second lens 12 is not easily deformed. As a result, the O-ring 310 can be uniformly in close contact between the first lens 11 and the second lens 12, and thus, even if the lens unit 1 is used for a long time, the intrusion of moisture that has passed through the O-ring 310 into the inside of the lens unit 1 can be suppressed.

[0066] In the present embodiment, the first ribs 224 that position the second annular portion 124 in the radial direction are provided at a plurality of positions in the circumferential direction on the inner circumferential surface of the first portion 221. Thus, even in a case where deformation due to the outer shape of the lens barrel 20 is likely to occur, the occurrence of the center shift of the second lens 12 due to the deformation of the first portion 221 can be suppressed by the first ribs 224.

[0067] In the present embodiment, the second ribs 225 that position the plurality of lenses in the radial direction are provided at a plurality of locations in the circumferential direction on the inner peripheral surface of the second portion 222. Therefore, even in a case where deformation due to the outer shape of the lens barrel 20 is likely to occur, the generation of center shift of the plurality of lenses due to deformation of the second portion 222 can be suppressed by the second ribs 225.

[0068] In the present embodiment, the first ribs 224 are provided at 4 locations, and the second ribs 225 are provided at 12 locations. Therefore, since the number of the first ribs 224 is less than the number of the second ribs 225, the first holding force fl when the second lens 12 is fitted to the first portion 221 can be made smaller than the average holding force obtained by dividing the second holding force when the plurality of lenses are fitted to the second portion 222 by the number of lens pieces C.

[0069] In the present embodiment, the first elastic member 31 overlaps the positioning step portion 25 in the optical axis L direction. Therefore, the force in the optical axis L direction when the first lens 11 compresses the first elastic member 31 is concentrated on the positioning step portion 25. Thus, when the operation of mounting the first lens 11 is performed, deformation of the lens barrel 20 can be suppressed.

[0070] In the present embodiment, the first lens 11 includes a first lens portion 113 and a first annular portion 114 that surrounds the first lens portion 113. The lens barrel 20 includes an abutting surface portion 24 that abuts against the first annular portion 114 from the image side Lb between the first barrel portion 21 and the second barrel portion 22. The abutting surface portion 24 includes a ring-shaped groove portion 241 that is recessed toward the image side Lb. The ring-shaped second elastic member 32 that is compressed between the first annular portion 114 and the groove portion 241 is disposed in the groove portion 241. Therefore, it is easier to ensure the air tightness between the first lens 11 and the second lens 12.

[0071] Symbol Explanation

[0072] 1…lens unit, 2…shutter, 3…aperture, 4…holder, 10…wide-angle lens, 11…first lens, 12…second lens, 13…third lens, 14…fourth lens, 15…fifth lens, 15a…flat portion, 16…sixth lens, 16a…flat portion, 18…joint lens, 20…lens barrel, 21…first barrel portion, 22…second barrel portion, 23…outer diameter barrel portion, 24…abutment face portion, 25…positioning step portion, 29…recess, 31…first elastic member, 32…second elastic member, 111…first lens face, 112…second lens face, 113…first lens portion, 114…first annular portion, 115…flange face, 121…first lens face, 122…second lens face, 123…second lens portion, 124…second annular portion, 125…flange face, 126…flange face, 127…annular step portion, 131…first lens face, 132…second lens face, 133…third lens portion, 134…third annular portion, 134a…flat portion, 135…flange face, 136…flange face, 150…flange portion, 211…rivet portion, 221…first portion, 222…second portion, 223…recess, 224…first rib, 225…second rib, 226…bottom face, 241…groove portion, 251…protruding portion, 310…ring, 320…ring, G1-G4…gate mark, L…optical axis, La…object side, Lb…image side.

Claims

1. A lens unit characterized by comprising: has: a first lens disposed at a position closest to an object along an optical axis; a second lens disposed on an image side of the first lens; a plurality of lenses disposed on an image side of the second lens; a lens barrel holding the first lens, the second lens, and the plurality of lenses; and a first annular elastic member disposed between the first lens and the second lens, the lens barrel includes a first barrel portion holding the first lens, a second barrel portion holding the second lens and the plurality of lenses at a position radially inward of the first barrel portion, and a positioning step portion abutting against an image-side lens disposed at a position closest to the image side among the plurality of lenses from the image side, the second barrel portion includes a first portion in a cylindrical shape holding the second lens and a second portion in a cylindrical shape holding the plurality of lenses, the first lens is held to the first barrel portion by caulking an object-side end portion of the first barrel portion, the second lens is held to the first portion by fitting into the first portion, the plurality of lenses are held to the second portion by fitting into the second portion, the first elastic member is compressed between the first lens and the second lens to a degree that the first lens and the second lens do not abut against each other, if a first holding force when the second lens is fitted into the first portion is f1, a number of lens pieces of the second lens and the plurality of lenses is C, a third holding force that is a sum of the first holding force and a second holding force when the plurality of lenses are fitted into the second portion is f2, an elastic force of the first elastic member is f3, and a fourth holding force by which the first barrel portion holds the first lens is f4, the following conditional expression is satisfied: f1xC < f2 < f3 < f4, a diameter of the first portion is larger than a diameter of the second portion, and a gate mark receiving recess for receiving a gate mark formed when the second lens is resin-molded is provided on an inner peripheral surface of the first portion by being recessed to a radial outer side.

2. The lens unit according to claim 1, wherein a plurality of portions of the first ribs are provided on the inner peripheral surface of the first portion in a circumferential direction.

3. The lens unit according to claim 2, wherein a plurality of portions of the second ribs are provided on the inner peripheral surface of the second portion in a circumferential direction.

4. The lens unit according to claim 3, wherein a number of the first ribs is smaller than a number of the second ribs.

5. The lens unit according to any one of claims 1 to 4, wherein the first elastic member overlaps the positioning step portion in the optical axis direction.

6. The lens unit according to any one of claims 1 to 4, wherein the first lens includes a first lens portion and a first annular portion that surrounds a portion of the first lens portion, The lens barrel has an abutment surface portion that abuts against the first annular portion from the image side between the first barrel portion and the second barrel portion, The abutment surface portion has a ring-shaped groove portion recessed toward the image side, A ring-shaped second elastic member is disposed in the groove portion and compressed between the first annular portion and the groove portion.

7. The lens unit according to claim 5, wherein The first lens has a first lens portion and a first annular portion that surrounds a portion of the first lens portion, The lens barrel has an abutment surface portion that abuts against the first annular portion from the image side between the first barrel portion and the second barrel portion, The abutment surface portion has a ring-shaped groove portion recessed toward the image side, A ring-shaped second elastic member is disposed in the groove portion and compressed between the first annular portion and the groove portion.

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