CN115951466A - Lens unit - Google Patents

Abstract

The invention provides a lens unit, which can restrain the blur of a first lens by optimizing the holding force when a wide-angle lens is held in a lens barrel. The lens unit (1) has: a lens barrel (20) that holds the first lens (11), the second lens (12), and the plurality of lenses; and an O-ring (310) disposed between the first lens (11) and the second lens (12). When a first holding force when the second lens (12) is fitted to the first part (221) is f1, the number of the second lens (12) and the plurality of lenses is C, a third holding force which is the sum of the first holding force and a second holding force when the plurality of lenses are fitted to the second part (222) is f2, an elastic force of the O-ring (310) is f3, and a fourth holding force when the first cylinder (21) holds the first lens (11) is f4, the lens unit (1) satisfies the following conditional expressions: f1 × C < f2 < f3 < f4.

Description

Lens unit

Technical Field

The present invention relates to a lens unit that holds a plurality of lenses in a lens barrel.

Background

In an imaging device mounted in an automobile, a surveillance camera, or the like, a lens unit is used in which a plurality of lenses are housed in a lens holder. In this lens unit, the object-side lens surface of the first lens closest to the object side is exposed to the outside from the lens barrel.

Such a lens unit is described in patent document 1, for example. 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 accommodated in a resin lens barrel. The lens barrel includes a first housing section for housing a first lens and a second housing section for housing a plurality of lenses. An elastic member is disposed between the flange portion of the first lens and the flange portion of the second lens. The first lens is locked to the first housing section by thermal caulking, and the plurality of lenses are press-fitted into the second housing section. 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 are not in contact with each other. Thereby, the airtightness of the inside of the lens unit is kept constant.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2020-154123

Disclosure of Invention

In the lens unit described above, when the holding force of the first housing section for holding the first lens, the elastic force of the elastic member when compressed, and the holding force of the second housing section for holding the plurality of lenses are not appropriate, there is a possibility that moisture passing through the elastic member may enter the inside of the lens holder when the lens unit is used for a long time. However, the above document does not specifically describe the force relationship.

In view of the above problems, an object of the present invention is to provide a lens unit capable of suppressing blur of a first lens by optimizing a holding force when a plurality of lenses are held in a barrel.

In order to solve the above problem, a lens unit according to the present invention includes: a first lens disposed at a position closest to an object side along an optical axis; a second lens disposed on an image side of the first lens; a plurality of lenses arranged on an image side of the second lens; a lens barrel that holds the first lens, the second lens, and the plurality of lenses; and an annular first elastic member disposed between the first lens and the second lens, the lens barrel including: a first tube section that holds the first lens; a second tube portion that holds the second lens and the plurality of lenses at a position radially inward of the first tube portion; and a positioning step portion that comes into contact with an image side lens, which is disposed closest to the image side, of the plurality of lenses, from the image side, the second tube portion including: a cylindrical first portion that holds the second lens; and a cylindrical second portion that holds the plurality of lenses, wherein the first lens is held in the first cylindrical portion by caulking an object-side end portion of the first cylindrical portion, the second lens is held in the first portion by fitting in the first portion, the plurality of lenses are held in the second portion by fitting in the second portion, the first elastic member is compressed between the first lens and the second lens to such an extent that the first lens and the second lens do not abut against each other, a first holding force when the second lens is fitted in the first portion is f1, the number of lens pieces of the second lens and the plurality of lenses is C, a third holding force that is a sum of a second holding force when the first holding force and the plurality of lenses are fitted in the second portion is f2, an elastic force of the first elastic member is f3, and a fourth holding force when the first cylindrical portion holds the first lens is f4, and the following conditions are satisfied.

f1×C＜f2＜f3＜f4(1)

In the present invention, the first elastic member is compressed between the first lens and the second lens to such an extent that the first lens and the second lens do not abut against each other. Therefore, the amount of compression of the first elastic member can be easily managed as compared with the case where the first lens and the second lens are in contact with each other. As a result, the airtightness inside the lens barrel is easily improved, and therefore, the blur of the lens surface on the image side of the first lens can be suppressed. Further, since the first lens and the second lens do not abut against each other, when the first lens is held by the first tube portion, it is difficult for the first elastic member to be compressed and thereby a large force is not directly applied to the second lens and the plurality of lenses. Therefore, when the first lens is held in the first tube, the lens breakage after the second lens can be suppressed.

In the present invention, when the fourth holding force f4 is larger than the elastic force f3, the first lens does not fall off the first cylindrical portion due to the elastic force f3 of the first elastic member even if the lens unit is used for a long time. As a result, even if the lens unit is used for a long time, the moisture passing through the first elastic member can be suppressed from entering the inside of the lens unit.

When the elastic force f3 is larger than the third holding force f2, the image side lens can be pressed against the positioning step portion via the second lens or the like by the third holding force f2 when the first lens is held by the first tube portion by caulking. As a result, the image side lens can be reliably positioned by the positioning step portion.

When the third holding force f2 is larger than the first holding force f1 × the number of lenses 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 number of lenses C. Therefore, when the first lens is held by the first tube portion by caulking, a large force is not easily applied to the second lens, and therefore the second lens is not easily deformed. As a result, the first elastic member can be uniformly adhered between the first lens and the second lens, and therefore, even if the lens unit is used for a long time, the moisture passing through the first elastic member can be prevented from entering the inside of the lens holding frame.

In the present invention, it is preferable that the first portion has a plurality of first ribs provided on an inner peripheral surface thereof to position the second lens in a radial direction. In this way, even when deformation due to the external shape of the lens barrel is likely to occur, the first ribs can suppress the occurrence of center shift of the second lens due to deformation of the first portion.

In the present invention, it is preferable that second ribs for positioning the plurality of lenses in the radial direction are provided at a plurality of positions in the circumferential direction on the inner circumferential surface of the second portion. In this way, even when deformation due to the external shape of the lens barrel is likely to occur, the second ribs can suppress the occurrence of center shift of the plurality of lenses due to the deformation of the second portion.

In the present invention, it is preferable that the number of the first ribs is smaller than the number of the second ribs. Thus, 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 number C of lens pieces.

In the present invention, it is preferable that the first elastic member overlaps with the positioning step portion in the optical axis direction. In this way, the force in the optical axis direction when the first elastic member is compressed by the first lens is concentrated on the positioning step portion. This can suppress deformation of the lens barrel during the work of attaching the first lens.

In the present invention, it is preferable that the first lens includes a first lens portion and a first annular portion which is a portion surrounding the first lens portion, the lens barrel includes a contact surface portion which is in contact with the first annular portion from an image side between the first cylindrical portion and the second cylindrical portion, the contact surface portion includes an annular groove portion which is recessed toward the image side, and an annular second elastic member which is compressed between the first annular portion and the groove portion is disposed in the groove portion. In this way, airtightness between the first lens and the second lens is more easily ensured.

Effects of the invention

In the present invention, since the conditional expression (1) is satisfied, the holding force when the lens is held in the lens barrel can be optimized. As a result, airtightness between the first lens and the second lens can be ensured, and therefore, blur of the lens surface on the image side of the first lens can be suppressed.

Drawings

Fig. 1 is a sectional view of a lens unit to which the present invention is applied.

Fig. 2 is an exploded perspective view of the lens unit.

Fig. 3 is a sectional view of the lens barrel.

Fig. 4 is a plan view of the lens barrel viewed from the object side.

Detailed Description

Embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings referred to in the following description, the number and scale of the members are different so that the members are as large as they can be recognized in the drawings. In the following description, the object side is denoted by La and the image side is denoted by Lb in the direction of the optical axis L along which the optical axis L extends.

(Structure of lens Unit)

Fig. 1 is a sectional view of a lens unit to which the present invention is applied. Fig. 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 imaging device. The lens unit 1 has substantially the same structure as a whole around the optical axis L. The lens unit 1 shown in fig. 1 includes a wide-angle lens 10 in which a plurality of lenses are arranged in the direction of the optical axis L, and a lens barrel 20 that holds the wide-angle lens 10 inside. An imaging element is provided on the image side Lb of the lens barrel 20. The image pickup element is a CMOS or the like.

(Wide-angle lens)

As shown in fig. 1 and 2, the wide-angle lens 10 has, for example, a lens structure of 5 groups of 6 lenses. In the present 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 includes, from the object side La to the image side Lb, a first lens 11 having negative optical power, a second lens 12 having negative optical power, a third lens 13 having positive optical power, a fourth lens 14 having positive optical power, and a cemented lens 18 (a fifth lens 15 and a sixth lens 16) having positive optical power. The plurality of lenses include a third lens 13 to a cemented lens 18.

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

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 toward the object side La, and the second lens surface 122 on the image side Lb is a concave curved surface recessed toward 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 is a portion where the gate mark G1 remains on the outer circumferential surface. The first lens surface 121 and the second lens surface 122 constitute a second lens portion 123. The second annular portion 124 has a circular outer shape in the direction of the optical axis L. The gate mark G1 is formed when the second lens 12 is resin-molded. The gate mark G1 slightly protrudes outward in the radial direction from the outer peripheral surface of the second annular portion 124.

A flange surface 125 of the second annular portion 124 facing the object side La is located radially outward of the first lens surface 121. A flange surface 126 of the second annular portion 124 facing the image side Lb is located radially outward of the second lens surface 122. The second annular portion 124 includes an annular step portion 127 protruding toward the object side La. The annular step portion 127 positions the first elastic member 31 in the radial direction.

The third lens 13 is a plastic lens. The first lens surface 131 on the object side La of the third lens 13 is a convex curved surface protruding toward the object side La, and the second lens surface 132 on the image side Lb is a concave curved surface recessed toward the object side La. The third lens 13 includes a third lens portion 133 and a third annular portion 134 which surrounds the third lens portion 133 and in which a gate mark G2 remains in a flat portion 134a of the outer circumferential surface. The first lens surface 131 and the second lens surface 132 constitute a third lens portion 133. The outer shape of the third annular portion 134 is D-shaped 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 radially outward from the flat surface portion 134 a. At this time, the gate mark G2 is located inside an imaginary circle formed by the outer shape of the third circular portion 134. A flange surface 135 of the third annular portion 134 facing the object side La is located radially outward of the first lens surface 131. A flange surface 136 of the third annular portion 134 facing the image side Lb is located radially outward of the second lens surface 132.

The fourth lens 14 is a glass lens. The cemented lens 18 is a cemented lens of the fifth lens 15 as a plastic lens having a negative power and the sixth lens 16 as a plastic lens having a positive power. The outer shape of the fifth lens 15 is D-shaped in the direction of the optical axis L. A gate mark G3 slightly protruding radially outward remains on the flat surface portion 15a of the outer peripheral surface of the fifth lens 15. 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 D-shaped in the direction of the optical axis L. A gate mark G4 slightly protruding radially outward remains on the flat surface portion 16a of the outer peripheral surface of the sixth lens 16. The gate mark G4 is located inside an imaginary circle formed by the outer shape of the sixth lens 16.

The lens unit 1 has an annular light-shielding sheet 2 between the second lens 12 and the third lens 13, and has an annular diaphragm 3 between the fourth lens 14 and the fifth lens 15.

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

(lens barrel)

Fig. 3 is a sectional view of the lens barrel. Fig. 4 is a plan view of the lens barrel viewed from the object side. The lens barrel 20 is made of resin. As a material of the lens barrel 20, crystalline plastics (polyethylene, polyamide, polytetrafluoroethylene) having excellent weather resistance, amorphous plastics (polycarbonate, etc.) having low moisture absorption, and the like are used. The lens barrel 20 is cylindrical. As shown in fig. 1 to 4, the lens barrel 20 includes a first cylindrical portion 21 that holds the first lens, a second cylindrical portion 22 that holds the second lens 12 and the plurality of lenses, and an outer diameter cylindrical portion 23 that extends from the image side Lb of the first cylindrical portion 21. An annular recess 29 for thinning is formed between the outer diameter tube portion 23 and the second tube portion 22.

The lens barrel 20 includes a contact surface portion 24 connecting the first cylindrical portion 21 and the second cylindrical portion 22, and a positioning step portion 25 projecting radially inward from the inner peripheral surface of the second cylindrical portion 22.

The first cylindrical portion 21 has a cylindrical shape and surrounds the outer peripheral surface of the first lens 11. A caulking portion 211 for fixing the first lens 11 is provided at an object side La end of the first cylinder portion 21. The inner diameter of the first tube 21 is slightly larger than the outer diameter of the first lens 11.

The abutment surface portion 24 is an annular surface portion facing 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 contact surface portion 24 includes an annular groove portion 241 recessed toward the image side Lb. The groove 241 is provided with the second elastic member 32.

The second cylindrical portion 22 has a cylindrical shape. The inner diameter of the second cylindrical portion 22 slightly decreases toward the image side Lb. The second tube 22 includes a first portion 221 holding the second lens 12 and a second portion 222 holding the plurality of lenses. The first portion 221 surrounds the outer peripheral surface of the lens of the second lens 12. A recess 223 is provided on the inner circumferential surface of the first portion 221 so that the open end faces the object side La. The recess 223 is also a gate mark accommodating recess that accommodates the gate mark G1. In the present embodiment, the concave portions 223 are provided at 4 places at equal intervals in the circumferential direction.

A plurality of first ribs 224 are provided in the circumferential direction on the inner circumferential surface of the first portion 221. The first rib 224 protrudes radially inward and extends 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 4 positions at equal intervals in the circumferential direction.

The second portion 222 surrounds the outer peripheral surfaces of the plurality of lenses. A plurality of second ribs 225 are provided on the inner circumferential surface of the second portion 222 in the circumferential direction. The second rib 225 protrudes radially inward, and extends in the optical axis L direction. The second rib 225 positions the plurality of lenses in the radial direction when the plurality of lenses are press-fitted into the second portion 222. In the present embodiment, the second ribs 225 are provided at 12 positions at equal intervals in the circumferential direction. The second rib 225 is disposed at a position not overlapping the first rib 224 in the direction of the optical axis L.

The positioning stepped portion 25 abuts on the cemented lens 18 (image side lens) disposed on the most image side from the image side Lb. The positioning step portion 25 includes a protruding portion 251 protruding radially inward at an end portion of the image side Lb.

(fixation of Wide-angle lens)

Next, the fixation of the wide angle lens 10 will be described. First, the cemented lens 18 is press-fitted into the second cylindrical portion 22 through the second lens 12. The cemented lens 18 is positioned in the optical axis L direction by the flange portion 150 of the fifth lens 15 abutting 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 on the flange portion 150 of the fifth lens from the object side La. The third annular portion 134 of the third lens 13 abuts the holder 4 from the object side La via the diaphragm 3. The second lens 12 is press-fitted into the first portion 221 so that the gate mark G1 is located inside the recess 223. The second annular portion 124 of the second lens 12 abuts on the third annular portion 134 of the third lens 13 from the object side La via the light-shielding sheet 2. At this time, the flange surface 135 of the third annular portion 134 is in contact with the flange surface 126 of the second annular portion 124 via the light-shielding sheet 2, and is located on the object side La with respect to the bottom surface 226 of the image side Lb of the concave portion 223.

Here, in the present embodiment, the concave portions 223 are provided at 4 places at equal intervals in the circumferential direction. Therefore, when the center of the second lens 12 is displaced from the optical axis L when the second lens 12 is press-fitted into the first portion 221, the center of the second lens 12 can be aligned with the optical axis L by rotating the second lens 12 by 90 ° around the optical axis L with respect to the first portion 221. After the center of the second lens 12 is aligned with the optical axis L, the second lens 12 is press-fitted into the first portion 221 so that the gate mark G1 is positioned inside the recess 223.

The first lens is inserted into the first tube 21. The first lens 11 is covered from the object side La by the caulking portion 211, and is restricted from moving to the object side La. As a result, the first lens 11 is held inside the first tube 21. At this time, the flange surface 115 of the first annular portion 114 abuts the abutment surface portion 24 from the object side La, whereby the first lens 11 is positioned in the optical axis L direction.

The 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 the present embodiment, the first elastic member 31 is an O-ring 310. The O-ring 310 is disposed on the outer circumferential side of the annular step portion 127. The O-ring 310 is positioned in the radial direction by the inner peripheral portion abutting against the annular step portion 127. The O-ring 310 overlaps the positioning step portion 25 when viewed from the optical axis L direction. The O-ring 310 is in close contact with the flange surface 115 of the first lens element 11 and the flange surface 125 of the second lens element 12 in a state of being elastically deformed in the direction of the optical axis L. At this time, the first lens 11 and the second lens 12 are not in contact with each other.

As shown in fig. 1, the second elastic member 32 is provided between the flange surface 115 of the first lens 11 and the abutment surface portion 24 on the outer side of the O-ring 310. The second resilient member 32 is an O-ring 320. An 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 in a state of being elastically deformed in the direction of the optical axis L.

Here, if the first holding force when the second lens 12 is fitted to the first portion 221 is f1, the number of lens pieces of the second lens 12 and the plurality of lenses is C, the third holding force that is the sum of the first holding force and the second holding force when the plurality of lenses are fitted to the second portion 222 is f2, the elastic force of the O-ring 310 is f3, and the fourth holding force when the first tube 21 holds the first lens 11 is f4, the following conditional expression (1) is satisfied.

f1×C＜f2＜f3＜f4(1)

When the fourth holding force f4 with which the first tube part 21 holds the first lens 11 is larger than the elastic force f3 of the O-ring 310, the first lens 11 does not fall off the first tube part 21 due to the elastic force f3 of the O-ring 310 even if the lens unit 1 is used for a long time. As a result, even if the lens unit 1 is used for a long time, the intrusion of moisture passing through the O-ring 310 into the lens unit 1 can be suppressed.

In addition, when the elastic force f3 is larger than the third holding force f2 which is the sum of the first holding force f1 when the second lens 12 is fitted to the first portion 221 and the second holding force when the plurality of lenses are fitted to the second portion 222, the cemented lens 18 can be pressed against the positioning stepped portion 25 through the second lens 12 by the third holding force f2 when the first lens 11 is held by caulking to the first tube portion 21. As a result, the cemented lens 18 can be reliably positioned by the positioning step portion 25.

When the third holding force f2 is larger than the first holding force f1 × the number of lenses 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 222 by the number of lenses C. Therefore, when the first lens 11 is held in the first tube part 21 by caulking, a large force is not easily applied to the second lens 12, and therefore, the second lens 12 is not easily deformed. As a result, the O-ring 310 can be uniformly adhered between the first lens 11 and the second lens 12, and therefore, even if the lens unit 1 is used for a long time, the moisture passing through the O-ring 310 can be suppressed from entering the inside of the lens unit 1.

In the present embodiment, the first holding force f1 when the second lens 12 is fitted to the first portion 221 is 3N. The second lens 12 and the plurality of lenses are the second lens 12, the third lens 13, the fourth lens, and the cemented lens 18, and the number of lenses C is 4. The third holding force f2, which is the sum of the first holding force and the second holding force when the plurality of lenses are fitted to the second portion 222, is 20N. The elastic force f3 of the O-ring 310 is 30N. The fourth holding force f4 with which the first barrel portion 21 holds the first lens 11 is 250N. Therefore, conditional expression (1) is satisfied.

(Effect)

In the present embodiment, the first elastic member 31 is compressed between the first annular portion 114 and the second annular portion 124 to such an extent that the first lens 11 and the second lens 12 do not abut against each other. Therefore, the amount of compression of the first elastic member 31 can be easily controlled as compared with the case where the first lens 11 and the second lens 12 are in contact with each other. As a result, the airtightness inside the lens barrel 20 is easily improved, and therefore, the blur of the lens surface on the image side of the first lens 11 can be suppressed. Further, since the first lens 11 and the second lens 12 do not abut against each other, when the first lens 11 is held by the first tube 21, it is difficult for the first elastic member 31 to be compressed and thereby apply a large force directly to the second lens 12 and the plurality of lenses. Therefore, when the first lens 11 is held by the first tube 21, damage to the second lens 12 and subsequent lenses can be suppressed.

In the present embodiment, the following conditional expression (1) is satisfied where f1 is a first holding force when the second lens 12 is fitted to the first portion 221, C is a number of lenses of the second lens 12 and the plurality of lenses, f2 is 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 to the second portion 222, f3 is an elastic force of the O-ring 310, and f4 is a fourth holding force when the first tube 21 holds the first lens 11.

f1×C＜f2＜f3＜f4(1)

In the present embodiment, since the fourth holding force f4 by which the first tube part 21 holds the first lens 11 is larger than the elastic force f3 of the O-ring 310, the first lens 11 does not fall off the first tube part 21 due to the elastic force f3 of the O-ring 310 even if the lens unit 1 is used for a long time. As a result, even if the lens unit 1 is used for a long time, the intrusion of moisture passing through the O-ring 310 into the lens unit 1 can be suppressed.

Further, the elastic force f3 is larger than the third holding force f2 which is the sum of the first holding force f1 when the second lens 12 is fitted in the first portion 221 and the second holding force when the plurality of lenses are fitted in the second portion 222, and therefore, when the first lens 11 is held in the first tube portion 21 by caulking, the cemented lens 18 can be pressed against the positioning step portion 25 via the second lens 12 and the like by the third holding force f 2. As a result, the cemented lens 18 can be reliably positioned by the positioning step portion 25.

Since the third holding force f2 is larger than the first holding force f1 × the number of lenses C, the first holding force f1 is 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 lenses C. Therefore, when the first lens 11 is held by the first tube 21 by caulking, a large force is not easily applied to the second lens 12, and therefore, the second lens 12 is not easily deformed. As a result, the O-ring 310 can be uniformly adhered between the first lens 11 and the second lens 12, and therefore, even if the lens unit 1 is used for a long time, the moisture passing through the O-ring 310 can be suppressed from entering the inside of the lens unit 1.

In the present embodiment, first ribs 224 that position the second annular portion 124 in the radial direction are provided at a plurality of circumferential positions on the inner circumferential surface of the first portion 221. Therefore, even when deformation due to the outer shape of the lens barrel 20 is likely to occur, the first ribs 224 can suppress the occurrence of center shift of the second lens 12 due to deformation of the first portion 221.

In the present embodiment, second ribs 225 that position a plurality of lenses in the radial direction are provided at a plurality of positions in the circumferential direction on the inner circumferential surface of the second portion 222. Therefore, even when deformation due to the outer shape of the lens barrel 20 is likely to occur, the second ribs 225 can suppress the occurrence of center shift of the plurality of lenses due to the deformation of the second portion 222.

In the present embodiment, the first rib 224 is provided at 4, and the second rib 225 is provided at 12. Therefore, since the number of the first ribs 224 is smaller than the number of the second ribs 225, the first holding force f1 when the second lens 12 is fitted to the first portion 221 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 222 by the number C of the lens pieces.

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 elastic member 31 is compressed by the first lens 11 is concentrated on the positioning step portion 25. This can suppress deformation of the lens barrel 20 during the work of attaching the first lens 11.

In the present embodiment, the first lens 11 includes a first lens portion 113 and a first annular portion 114 that is a portion surrounding the first lens portion 113. The lens barrel 20 includes a contact surface portion 24 that contacts the first annular portion 114 from the image side Lb between the first cylindrical portion 21 and the second cylindrical portion 22. The contact surface portion 24 includes an annular groove portion 241 recessed toward the image side Lb. The groove 241 is provided with an annular second elastic member 32 compressed between the first annular portion 114 and the groove 241. Therefore, it is easier to ensure airtightness between the first lens 11 and the second lens 12.

Description of the symbols

1 lens unit, 2 light-shielding sheet, 3 diaphragm, 4 holder, 10 wide-angle lens, 11 first lens, 12 second lens, 13 third lens, 14 fourth lens, 15 fifth lens, 15a plane portion, 16 sixth lens, 16a plane portion, 18 cemented lens, 20 lens barrel, 21 first barrel, 22 second barrel, 23 outer diameter barrel, 24 abutting surface, 25 positioning step portion, 29 concave portion, 31 first elastic member, 32 second elastic member, 111 first lens surface, 112 second lens surface, 113 first lens portion, 114 first ring portion, 115 flange surface, 121 first lens surface, 122 second lens surface, 123 second lens portion, 124 second ring portion, 125 flange surface, 126 flange surface, 127 annular step portion, 131 first lens surface, 132 second lens surface, 133 third lens portion, 134 third ring portion, 134a plane portion, 135 flange surface, 136 flange surface, 150, 211 flange portion, 221 first lens portion, 226 second lens surface, 223 second lens portion, 223 optical axis ring portion, 123 optical axis ring portion, 110 optical axis ring portion, 320 optical axis ring, 123 optical axis ring, 110, and optical axis ring portion.

Claims (6)

1. A lens unit, comprising:

a first lens disposed at a position closest to an object side along an optical axis;

a second lens element disposed on an image side of the first lens element;

a plurality of lenses disposed on an image side of the second lens element;

a lens barrel that holds the first lens, the second lens, and the plurality of lenses; and

a ring-shaped first elastic member disposed between the first lens and the second lens,

the lens barrel includes: a first tube section that holds the first lens; a second cylinder portion that holds the second lens and the plurality of lenses at a position radially inward of the first cylinder portion; and a positioning step section which is brought into contact with an image side lens disposed at a position closest to the image side among the plurality of lenses from the image side,

the second tube section includes a tubular first portion for holding the second lens and a tubular second portion for holding the plurality of lenses,

the first lens is held by the first cylindrical portion by caulking an object-side end portion of the first cylindrical portion,

the second lens is held by the first portion by being fitted to the first portion,

the plurality of lenses are held by the second portion by fitting to the second portion,

the first elastic member is compressed between the first lens and the second lens to such an extent that the first lens and the second lens do not abut against each other,

when a first holding force when the second lens is fitted to 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 to the second portion is f2, an elastic force of the first elastic member is f3, and a fourth holding force when the first barrel portion holds the first lens is f4, the following conditional expression is satisfied:

f1×C＜f2＜f3＜f4。

2. the lens unit of claim 1,

first ribs for positioning the second lens in a radial direction are provided at a plurality of circumferential positions on an inner circumferential surface of the first portion.

3. The lens unit of claim 2,

second ribs for positioning the plurality of lenses in the radial direction are provided at a plurality of locations in the circumferential direction on the inner circumferential surface of the second portion.

4. The lens unit of claim 3,

the number of the first ribs is smaller than the number of the second ribs.

5. The lens unit according to any one of claims 1 to 4,

the first elastic member overlaps with the positioning step portion in the optical axis direction.

6. The lens unit according to any one of claims 1 to 5,

the first lens includes a first lens portion and a first annular portion that is a portion surrounding the first lens portion,

the lens barrel includes a contact surface portion that contacts the first annular portion from an image side between the first tube portion and the second tube portion,

the contact surface portion includes an annular groove portion recessed toward the image side,

an annular second elastic member compressed between the first annular portion and the groove portion is disposed in the groove portion.

Images