Imaging unit, endoscope, and lens frame

Abstract

An imaging unit according to an embodiment comprises: a lens frame that has a cylindrical tubular part which extends in the optical axis direction and which is centered on the optical axis; and a first optical system that is constituted by a plurality of lenses. The first optical system includes a first lens which is held by the inner circumferential surface of the tubular part. The tubular part has: a step part that is recessed, from the inner circumferential surface of the tubular part, outward in the radial direction centered on the optical axis; a step surface that is an inner surface of the step part and that, along the circumferential direction centered on the optical axis, faces a part of a first outer circumferential surface, which is a radially-outward-facing surface of the first lens, with a gap therebetween; and a through hole that passes through the tubular part in a direction intersecting the optical axis direction and that reaches the step surface. The first outer circumferential surface is exposed to the outside of the lens frame via the through hole. An adhesive is filled between the step surface and the first outer circumferential surface.

Description

Imaging unit, endoscope, and lens frame

[0001] The present invention relates to an imaging unit, an endoscope, and a lens frame.

[0002] An imaging unit mounted on an endoscope is known, which includes an objective lens and a lens holder that houses the objective lens, and in which the peripheral portion of the surface of the objective lens facing the optical axis direction is adhesively fixed to the lens holder (for example, Patent Document 1).

[0003] JP 2014-119474 A

[0004] In the assembly process of the imaging unit described above, when applying adhesive to the peripheral edge of the surface of the objective lens facing the optical axis direction, there was a risk that the adhesive would accidentally adhere to the effective light width of the surface of the objective lens through which light rays pass. If adhesive adheres to the effective light width of the objective lens, it is necessary to remove the adhesive from the surface of the objective lens, which could increase the number of steps required to assemble the imaging unit.

[0005] In view of the above circumstances, an object of the present invention is to provide an imaging unit, an endoscope, and a lens frame that can suppress an increase in the number of steps required for assembling the imaging unit.

[0006] In one aspect of the present invention to achieve the above-mentioned object, an imaging unit comprises a lens frame having a cylindrical tubular portion extending in the optical axis direction with the optical axis as its center, and a first optical system constituted by a plurality of lenses, wherein the first optical system includes a first lens held on the inner surface of the tubular portion, the tubular portion having a step portion recessed radially outward from the inner surface of the tubular portion with the optical axis as its center, a step surface on the inner surface of the step portion facing a part of a first outer surface of the first lens facing radially outward with a gap in between along the circumferential direction with the optical axis as its center, and a through-hole portion penetrating the tubular portion in a direction intersecting the optical axis direction and connected to the step surface, the first outer surface being exposed to the outside of the lens frame through the through-hole portion, and an adhesive being filled between the step surface and the first outer surface.

[0007] An endoscope according to one aspect of the present invention includes the above-described imaging unit at the tip of the insertion section.

[0008] In one aspect of the present invention, the lens frame is a lens frame provided in an imaging unit, and has a cylindrical tubular portion that extends in the optical axis direction around the optical axis and accommodates a plurality of lenses, the inner surface of the tubular portion holds a first lens included in the plurality of lenses, the tubular portion has a step portion that is recessed radially outward from the inner surface of the tubular portion around the optical axis, an inner surface of the step portion that is a step surface that faces a part of a first outer surface that is the surface of the first lens facing radially outward along the circumferential direction around the optical axis with a gap between them, and a through-hole portion that penetrates the tubular portion in a direction intersecting the optical axis direction and is connected to the step surface, and the first outer surface is exposed to the outside of the lens frame via the through-hole portion.

[0009] According to the present invention, it is possible to provide an imaging unit, an endoscope, and a lens frame that can suppress an increase in the number of steps required for assembling the imaging unit.

[0010] FIG. 1 is a schematic perspective view showing an endoscope system of a first embodiment. FIG. 2 is a cross-sectional view showing an imaging unit of the first embodiment. FIG. 3 is a first enlarged cross-sectional view showing a portion of the imaging unit of the first embodiment. FIG. 4 is a second enlarged cross-sectional view showing a portion of the imaging unit of the first embodiment. FIG. 5 is a first perspective view showing a portion of the imaging unit of the first embodiment. FIG. 6 is a second perspective view showing a portion of the imaging unit of the first embodiment. FIG. 7 is a perspective view showing a portion of an imaging unit of a comparative example. FIG. 8 is a flowchart showing a fixing process of the first embodiment. FIG. 9 is a cross-sectional view showing a filling process of the first embodiment. FIG. 10 is a cross-sectional view showing an aperture member attachment process of the first embodiment. FIG. 11 is an enlarged cross-sectional view showing a portion of the imaging unit of the second embodiment. FIG. 12 is a perspective view showing a portion of the imaging unit of the second embodiment.

[0011] An imaging unit, an endoscope, and a lens frame according to embodiments of the present invention will be described below with reference to the drawings. Note that the scope of the present invention is not limited to the following embodiments and can be modified as desired within the scope of the technical concept of the present invention. In addition, in the following drawings, the scale and number of components may differ from the actual structure in order to make each component easier to understand.

[0012] In each figure, the Z axis is indicated as appropriate. The Z axis is the direction in which the optical axis J of the embodiment described below extends. The optical axis J shown in each figure as appropriate is a virtual axis. In the following description, the direction in which the optical axis J extends, i.e., the direction parallel to the Z axis, will be referred to as the "optical axis direction." The radial direction centered on the optical axis J will be simply referred to as the "radial direction." The circumferential direction centered on the optical axis J will be simply referred to as the "circumferential direction." The side of the optical axis direction toward which the arrow of the Z axis points (+Z side) is the "object side (distal side)," and the side of the optical axis direction opposite to the side toward which the arrow of the Z axis points (-Z side) is the "base end side (proximal side)." The circumferential direction is indicated by arrow θ in each figure.

[0013] <First Embodiment> Fig. 1 is a perspective view showing an endoscope system 1 of this embodiment. Fig. 2 is a cross-sectional view showing an imaging unit 30 of this embodiment. The endoscope system 1 shown in Fig. 1 includes an endoscope 2, a light source device 3, a video processor 4, and a color monitor 5. The use of the endoscope 2 of this embodiment is not particularly limited, and may be, for example, a medical endoscope or an industrial endoscope. The endoscope 2 includes an insertion section 9 that is inserted into a subject, an operation section 10 that is disposed outside the subject, and a universal cord 17 that extends from the operation section 10.

[0014] A light guide bundle (not shown), an electric cable forming an electric signal transmission path, and the like are inserted inside the universal cord 17. A scope connector 18 is provided at the rear end of the universal cord 17, which optically couples illumination light from the light source device 3 that supplies illumination light to the incident end of the light guide bundle. The electric cable inside the universal cord 17 extends inside a scope cable 19 that branches off from the scope connector 18. An electric connector unit 20 is provided at the end of the scope cable 19, which electrically connects the end of the electric cable (not shown) inside the scope cable 19 to the video processor 4. When the electric connector unit 20 is connected to the video processor 4, the electrical components built into the endoscope 2 and the video processor 4 are connected so as to be able to communicate with each other via the electric cable.

[0015] The insertion section 9 has a tip section 6, a bending section 7, and a flexible tube section 8, in this order, from the object side end, which is the tip in the insertion direction into the subject, to the base side end connected to the operation section 10. A well-known tip opening, an observation window 6b, an illumination window, and the like, which are not shown, are formed on the tip surface of the tip section 6. Inside the tip section 6, an imaging unit 30 that images the subject in front of the tip section 6 is disposed at a position opposite the observation window 6b. In other words, the imaging unit 30 is disposed at the tip of the insertion section 9. The endoscope 2 includes the imaging unit 30 at the tip of the insertion section 9. A detailed configuration of the imaging unit 30 will be described later.

[0016] The object-side end of a light guide bundle that transmits illumination light is located on the back side of the illumination window. The light guide bundle is inserted into the insertion section 9, passes through the operation section 10, and extends into the universal cord 17. The proximal end of the light guide bundle is located inside the scope connector 18. When the scope connector 18 is connected to the light source device 3, illumination light from the light source device 3 is optically coupled to the light guide bundle. As a result, illumination light generated by the light source device 3 is optically transmitted to the illumination window in the distal end portion 6, and is emitted from the illumination light to the outside of the distal end portion 6.

[0017] The bending section 7 is connected to the end portion on the proximal side of the distal end section 6. The bending section 7 is tubular and bendable. The amount and direction of bending of the bending section 7 can be changed by operating the operation section 10. This allows the orientation of the distal end section 6 to be changed. The bending section 7 includes, for example, multiple nodal rings. Each nodal ring is rotatably connected to an adjacent nodal ring. In the bending section 7, two systems of operation wires including a first operation wire and a second operation wire, a light guide bundle, an electric cable, a treatment instrument channel, etc. are inserted inside the nodal rings. The operation wires extend from the bending section 7 through the inside of the flexible tube section 8 to the operation section 10.

[0018] The operation unit 10 has an operation unit main body 13 that is held by the user and is used for various operations of the endoscope 2. A bending operation unit 16, a switch unit 23, and an operation lever 24 are provided on the upper part of the operation unit main body 13. The bending operation unit 16 has operation knobs 14 and 15 that operate the amount and direction of bending of the bending portion 7. The operation knobs 14 and 15 can independently pull the first operation wire and the second operation wire, respectively.

[0019] The switch section 23 has at least one switch that is mainly used to operate the imaging function. The operation lever 24 is used to operate the adjustment amount of the focus adjustment function, magnification adjustment function, zoom variable power adjustment function, etc. of the imaging unit 30. A forceps opening 12 and a folding prevention portion 11 are provided at the bottom of the operation section main body 13. The forceps opening 12 is an opening that communicates with the proximal end of the treatment instrument channel that extends from the inside of the operation section 10 through the insertion section 9 to the distal opening of the distal end section 6. The folding prevention portion 11 connects the insertion section 9 and the operation section 10.

[0020] As described above, the imaging unit 30 is disposed at the tip of the insertion portion 9. The imaging unit 30 forms an optical image of the subject. As shown in FIG. 2 , the imaging unit 30 has a cylindrical shape extending in the optical axis direction. In this embodiment, the imaging unit 30 includes a main body frame 31, a lens frame 34, a second lens frame 39, an aperture member 45, a first optical system 50, and a second optical system 59.

[0021] The main body frame 31 has a cylindrical shape extending in the optical axis direction. In this embodiment, the main body frame 31 has a substantially cylindrical shape extending in the optical axis direction with the optical axis J as its center. The main body frame 31 may have other shapes, such as a rectangular cylindrical shape extending in the optical axis direction. The main body frame 31 is open on both the object side (+Z side) and the base end side (-Z side). The main body frame 31 houses the lens frame 34, the second lens frame 39, the aperture member 45, the first optical system 50, and the second optical system 59. The main body frame 31 holds the lens frame 34 and the second lens frame 39. The main body frame 31 has a first main body portion 31a, a second main body portion 31c, and a third main body portion 31e.

[0022] The first main body portion 31a has a generally cylindrical shape extending in the optical axis direction with the optical axis J as its center. The first main body portion 31a is the object side (+Z side) portion of the main body frame 31. The object side end of the first main body portion 31a is the object side end of the main body frame 31. The inner circumferential surface of the first main body portion 31a holds the lens frame 34. The first main body portion 31a has a protrusion 31b. The protrusion 31b protrudes radially inward from the base end side (-Z side) end of the first main body portion 31a. The protrusion 31b extends circumferentially around the inner circumferential surface of the first main body portion 31a. When viewed in the optical axis direction, the protrusion 31b is generally annular.

[0023] The second main body portion 31c is generally cylindrical and extends in the optical axis direction with the optical axis J as its center. The second main body portion 31c is located closer to the base end (-Z side) than the first main body portion 31a. The second main body portion 31c is connected to the first main body portion 31a in the optical axis direction. The outer diameter of the second main body portion 31c and the outer diameter of the first main body portion 31a are generally the same. The inner diameter of the second main body portion 31c is smaller than the inner diameter of the first main body portion 31a. The inner peripheral surface of the second main body portion 31c supports the second lens frame 39 so that it can move in the optical axis direction.

[0024] The third main body portion 31e is the portion on the base end side (-Z side) of the main body frame 31. The base end side end of the third main body portion 31e is the base end side end of the main body frame 31. The third main body portion 31e is substantially cylindrical and extends in the optical axis direction with the optical axis J as its center. The third main body portion 31e is located closer to the base end side than the second main body portion 31c. The third main body portion 31e is connected to the second main body portion 31c in the optical axis direction. The inner diameter of the third main body portion 31e and the inner diameter of the second main body portion 31c are substantially the same size. The outer diameter of the third main body portion 31e is smaller than the outer diameter of the second main body portion 31c.

[0025] The lens frame 34 has a cylindrical shape extending in the optical axis direction. In this embodiment, the lens frame 34 has a substantially cylindrical shape extending in the optical axis direction with the optical axis J as its center. The lens frame 34 is fixed to the main body frame 31. The lens frame 34 has a cylindrical portion 35, a protruding portion 37, and a flange portion 38.

[0026] The tubular portion 35 has a cylindrical shape extending in the optical axis direction with the optical axis J as its center. The tubular portion 35 is open on both the object side (+Z side) and the base end side (-Z side). The tubular portion 35 houses a first optical system 50 composed of multiple lenses. That is, the tubular portion 35 houses multiple lenses. The first optical system 50 includes a first lens 51, a second lens 55, a third lens 56, and a fourth lens 57. The lenses are arranged in the following order from the base end side to the object side: first lens 51, second lens 55, third lens 56, and fourth lens 57. Therefore, the first lens 51 is the lens arranged furthest from the base end side among the multiple lenses constituting the first optical system 50. The inner circumferential surface of the tubular portion 35 holds the first optical system 50. That is, in this embodiment, the inner circumferential surface of the tubular portion 35 holds multiple lenses. The configuration of the first optical system 50 is not limited to that of the present embodiment. For example, the number of lenses constituting the first optical system 50 may be three or less, or may be five or more. Furthermore, the shape of each lens is not limited to that of the present embodiment. The cylindrical portion 35 has a first cylindrical portion 35a, a second cylindrical portion 35c, a third cylindrical portion 35e, a fourth cylindrical portion 35g, a fifth cylindrical portion 35i, and a sixth cylindrical portion 36. In the following description, the surface of the lens facing the object side may be referred to as the front surface, and the surface of the lens facing the base end side may be referred to as the rear surface.

[0027] The first cylindrical portion 35a has a cylindrical shape that extends in the optical axis direction with the optical axis J as its center. The first cylindrical portion 35a is the object side (+Z side) portion of the lens frame 34. The object side end of the first cylindrical portion 35a is the object side end of the lens frame 34. The first cylindrical portion 35a is located closer to the object side than the main body frame 31. The inner peripheral surface of the first cylindrical portion 35a holds the fourth lens 57.

[0028] The second cylindrical portion 35c has a cylindrical shape that extends in the optical axis direction with the optical axis J as its center. The second cylindrical portion 35c is disposed closer to the base end (-Z side) than the first cylindrical portion 35a. The second cylindrical portion 35c is connected to the first cylindrical portion 35a in the optical axis direction. The second cylindrical portion 35c is located closer to the object side (+Z side) than the main body frame 31. The outer diameter of the second cylindrical portion 35c and the outer diameter of the first cylindrical portion 35a are approximately the same size. The inner diameter of the second cylindrical portion 35c is smaller than the inner diameter of the first cylindrical portion 35a.

[0029] The third cylindrical portion 35e has a cylindrical shape that extends in the optical axis direction with the optical axis J as its center. The third cylindrical portion 35e is disposed closer to the base end (-Z side) than the second cylindrical portion 35c. The third cylindrical portion 35e is connected to the second cylindrical portion 35c in the optical axis direction. The outer diameter of the third cylindrical portion 35e is smaller than the outer diameter of the second cylindrical portion 35c. The outer peripheral surface of the third cylindrical portion 35e contacts the inner peripheral surface of the first main body portion 31a. The third cylindrical portion 35e may be fixed to the inner peripheral surface of the first main body portion 31a. The inner diameter of the third cylindrical portion 35e and the inner diameter of the second cylindrical portion 35c are approximately the same dimension. The inner peripheral surface of the third cylindrical portion 35e holds the third lens 56.

[0030] The fourth cylindrical portion 35g has a cylindrical shape extending in the optical axis direction with the optical axis J as its center. The fourth cylindrical portion 35g is positioned closer to the base end (-Z side) than the third cylindrical portion 35e. The fourth cylindrical portion 35g is connected to the third cylindrical portion 35e in the optical axis direction. The outer diameter of the fourth cylindrical portion 35g and the outer diameter of the third cylindrical portion 35e are approximately the same. The outer peripheral surface of the fourth cylindrical portion 35g contacts the inner peripheral surface of the first main body portion 31a. The outer peripheral surface of the fourth cylindrical portion 35g may be fixed to the inner peripheral surface of the first main body portion 31a. The inner diameter of the fourth cylindrical portion 35g is smaller than the inner diameter of the third cylindrical portion 35e. The radially outer portion of the surface of the fourth cylindrical portion 35g facing the base end contacts the protrusion 31b in the optical axis direction. This determines the position of the lens frame 34 in the optical axis direction relative to the main body frame 31.

[0031] The fifth cylindrical portion 35i has a cylindrical shape extending in the optical axis direction with the optical axis J as its center. The fifth cylindrical portion 35i is disposed closer to the base end (-Z side) than the fourth cylindrical portion 35g. The fifth cylindrical portion 35i is connected to the fourth cylindrical portion 35g in the optical axis direction. The outer diameter of the fifth cylindrical portion 35i is smaller than the outer diameter of the fourth cylindrical portion 35g. The fifth cylindrical portion 35i is disposed radially spaced apart from the main body frame 31. The inner diameter of the fifth cylindrical portion 35i and the inner diameter of the fourth cylindrical portion 35g are approximately the same dimension. The inner circumferential surface of the fifth cylindrical portion 35i holds the second lens 55. The fifth cylindrical portion 35i has a protrusion 35k. The protrusion 35k protrudes radially inward from the base end of the fifth cylindrical portion 35i. The protrusion 35k extends circumferentially around the inner circumferential surface of the fifth cylindrical portion 35i and has a substantially annular shape when viewed in the optical axis direction.

[0032] FIG. 3 is a first enlarged cross-sectional view showing a portion of the imaging unit 30 of this embodiment. FIG. 4 is a second enlarged cross-sectional view showing a portion of the imaging unit 30 of this embodiment. Note that FIG. 4 is a cross-sectional view of a portion of the imaging unit 30 as viewed from a position rotated approximately 30° circumferentially from FIG. 3. FIG. 5 is a first perspective view showing a portion of the imaging unit 30 of this embodiment. As shown in FIG. 2, the sixth cylindrical portion 36 has a cylindrical shape extending in the optical axis direction with the optical axis J as its center. The sixth cylindrical portion 36 is disposed closer to the base end (-Z side) than the fifth cylindrical portion 35i. The sixth cylindrical portion 36 is connected to the fifth cylindrical portion 35i in the optical axis direction. The outer diameter of the sixth cylindrical portion 36 is smaller than the outer diameter of the fifth cylindrical portion 35i. The sixth cylindrical portion 36 is disposed radially spaced apart from the main body frame 31. The inner diameter of the sixth cylindrical portion 36 and the inner diameter of the fifth cylindrical portion 35i are approximately the same dimension. The inner peripheral surface of the sixth cylindrical portion 36 holds the first lens 51. As shown in Fig. 3, the sixth cylindrical portion 36 has a step portion 36a, a step surface 36b, a through-hole portion 36c, and a fixing surface 36e. That is, the cylindrical portion 35 has the step portion 36a, the step surface 36b, the through-hole portion 36c, and the fixing surface 36e.

[0033] As shown in FIGS. 3 and 4 , the step portion 36a is a recess recessed radially outward from the inner circumferential surface of the sixth cylindrical portion 36. That is, the step portion 36a is recessed radially outward from the inner circumferential surface of the cylindrical portion 35 centered on the optical axis J. Although not shown, the step portion 36a extends in the circumferential direction along the inner circumferential surface of the sixth cylindrical portion 36. That is, the step portion 36a extends along the circumferential direction. In this embodiment, the step portion 36a extends all the way around in the circumferential direction. The step portion 36a does not have to extend all the way around in the circumferential direction. In this embodiment, the base-side (−Z side) end of the step portion 36a is located at the base-side end of the sixth cylindrical portion 36. The base-side end of the step portion 36a may be located closer to the object side (+Z side) than the base-side end of the sixth cylindrical portion 36. From the viewpoint of increasing the adhesive strength between the step surface 36b (described later) and the first lens 51, it is preferable that the base end of the step portion 36a be located closer to the base end than the first outer peripheral surface 51a, which is the surface facing radially outward of the first lens 51. When viewed from the radial direction, the object side (+Z side) end of the step portion 36a overlaps with the first lens 51. In this embodiment, when viewed from the radial direction, the step portion 36a overlaps with the base end side portion of the first lens 51.

[0034] The step surface 36b is an inner surface of the step portion 36a and faces radially inward. The step surface 36b faces a portion of the first outer peripheral surface 51a of the first lens 51 on the base end side (-Z side) with a gap in the radial direction. The step surface 36b extends along the circumferential direction. Therefore, the step surface 36b faces a portion of the first outer peripheral surface 51a with a gap in the circumferential direction centered on the optical axis J. In this embodiment, the step surface 36b extends all the way around the circumferential direction. Therefore, the step surface 36b faces a portion of the first outer peripheral surface 51a with a gap in the circumferential direction. Note that the step surface 36b does not have to extend all the way around the circumferential direction.

[0035] As shown in FIG. 5, the through-hole portion 36c is a hole that penetrates the sixth cylindrical portion 36 in a direction intersecting the optical axis direction. In this embodiment, the through-hole portion 36c is a hole that penetrates the sixth cylindrical portion 36 in a radial direction. In this embodiment, the through-hole portion 36c is substantially rectangular when viewed in the radial direction. When viewed in the radial direction, the through-hole portion 36c may have other shapes, such as a circular shape or a triangular shape. In this embodiment, the through-hole portion 36c is open on the base end side (-Z side). The through-hole portion 36c does not have to be open on the base end side. As shown in FIG. 3, the through-hole portion 36c is connected to the step surface 36b. As a result, the interior of the through-hole portion 36c is connected to the gap between the step surface 36b and the first outer peripheral surface 51a.

[0036] As shown in FIG. 5 , in this embodiment, the cylindrical portion 35 has a plurality of through-hole portions 36c. In this embodiment, the cylindrical portion 35 has four through-hole portions 36c. The number of through-hole portions 36c included in the cylindrical portion 35 may be three or less, or five or more. The plurality of through-hole portions 36c are arranged at intervals along the circumferential direction. Although not shown, each through-hole portion 36c is connected to the step surface 36b. Therefore, the interior of each through-hole portion 36c is connected to the gap between the step surface 36b and the first outer peripheral surface 51a.

[0037] The fixing surface 36e is a surface of the outer surface of the sixth cylindrical portion 36 that faces the base end side (-Z side). In other words, the fixing surface 36e is a surface of the outer surface of the cylindrical portion 35 that faces the base end side. In this embodiment, the cylindrical portion 35 has four fixing surfaces 36e. The fixing surfaces 36e are arranged at intervals in the circumferential direction. One through-hole portion 36c is arranged between a pair of fixing surfaces 36e that are arranged adjacent to each other in the circumferential direction. When viewed from the optical axis direction, each fixing surface 36e has a substantially arc shape centered on the optical axis J.

[0038] The protrusion 37 is columnar and protrudes from a portion of the fixing surface 36e toward the base end (-Z side). That is, the protrusion 37 protrudes from the base end of the cylindrical portion 35 toward the base end. When viewed in the optical axis direction, the fixing surface 36e has a generally arcuate shape centered on the optical axis J. In this embodiment, the lens frame 34 has multiple protrusions 37. Each protrusion 37 protrudes toward the base end from a different portion of the fixing surface 36e. The protrusions 37 are arranged at intervals along the circumferential direction. The fixing surfaces 36e and the protrusions 37 are arranged along the circumferential direction. In this embodiment, the total length of the circumferential dimensions of the multiple protrusions 37 is shorter than the total length of the circumferential dimensions of the lens frame 34 other than the multiple protrusions 37. More specifically, the total length of the circumferential dimensions of each protrusion 37 is shorter than the total length of the circumferential dimensions of each through-hole portion 36c and each fixing surface 36e.

[0039] As shown in FIG. 2, the flange portion 38 protrudes radially outward from the cylindrical portion 35. More specifically, the flange portion 38 is an annular plate-like member protruding radially outward from the second cylindrical portion 35c. The plate surface of the flange portion 38 faces the optical axis direction. When viewed from the optical axis direction, the flange portion 38 has a substantially annular shape. The surface of the flange portion 38 facing the base end side (-Z side) faces the surface of the main body frame 31 facing the object side (+Z side) in the optical axis direction. In this embodiment, the flange portion 38 is fixed to the main body frame 31 with an adhesive (not shown). This fixes the lens frame 34 to the main body frame 31. This also makes it possible to accurately determine the position of the lens frame 34 relative to the main body frame 31 in the optical axis direction.

[0040] The second lens frame 39 is cylindrical and extends in the optical axis direction, centered on the optical axis J. The second lens frame 39 is open on both the object side (+Z side) and the base end side (-Z side). The second lens frame 39 houses the second optical system 59. In this embodiment, the second optical system 59 includes a fifth lens 59a. The second optical system 59 may include other lenses in addition to the fifth lens 59a. The second optical system 59 is disposed closer to the base end than the first optical system 50. The second optical system 59 is fixed to the inner circumferential surface of the second lens frame 39. In the radial direction, the object side portion of the second lens frame 39 is disposed between the main body frame 31 and the cylindrical portion 35. As described above, the second lens frame 39 is supported by the inner circumferential surface of the main body frame 31 so as to be movable in the optical axis direction. When the second lens frame 39 moves in the optical axis direction by an actuator device (not shown), the second optical system 59 moves together with the second lens frame 39 in the optical axis direction. This makes it possible to adjust the focal position of the optical image of the subject formed by the first optical system 50 and the second optical system 59 so that it coincides with the light receiving surface of the image sensor arranged closer to the proximal end than the second optical system 59. In other words, by moving the second lens frame 39 in the optical axis direction, the focal point of the optical image of the subject in the endoscope 2 can be adjusted.

[0041] In this embodiment, the imaging element may be, for example, an image sensor such as a CCD or a CMOS. The imaging element converts an optical image of the subject formed by the first optical system 50 and the second optical system 59 into a video signal. The imaging element is communicably connected to the video processor 4 shown in FIG. 1 via an electric cable (not shown). The video signal converted by the imaging element is transmitted to the video processor 4 via the electric cable, and an image of the subject is formed in the video processor 4.

[0042] As described above, the first optical system 50 shown in FIG. 2 includes the first lens 51. Furthermore, as described above, the first lens 51 is the lens arranged furthest from the base end (−Z side) of the multiple lenses constituting the first optical system 50. The first lens 51 is housed inside the sixth cylindrical portion 36. As shown in FIG. 3 , the first lens 51 has a first outer peripheral surface 51 a and a cemented portion 51 c. As described above, the first outer peripheral surface 51 a is the surface of the first lens 51 facing radially outward. The first outer peripheral surface 51 a faces the inner peripheral surface of the sixth cylindrical portion 36 in the radial direction. In this embodiment, the first lens 51 is a cemented lens formed by cementing together a first cemented lens 52 and a second cemented lens 53 that are arranged side by side in the optical axis direction.

[0043] The first cemented lens 52 is disposed closer to the object side (+Z side) than the second cemented lens 53. The first cemented lens 52 is, for example, a concave meniscus lens recessed toward the object side. The first cemented lens 52 may be a lens of another shape. The first cemented lens 52 has a first surface 52a, a second surface 52b, a third surface 52c, and a first outer circumferential portion 52e. The first outer circumferential portion 52e is a surface facing radially outward of the first cemented lens 52. In this embodiment, the first outer circumferential portion 52e contacts the inner circumferential surface of the sixth cylindrical portion 36. This determines the radial position of the first lens 51 with respect to the lens frame 34.

[0044] The first surface 52a is the front surface of the first cemented lens 52. The first surface 52a intersects with the optical axis J. The radial outer edge of the first surface 52a contacts the protrusion 35k of the cylindrical portion 35 in the optical axis direction. This determines the position of the first lens 51 in the optical axis direction relative to the lens frame 34. The radial outer edge of the first surface 52a is connected to the first outer periphery 52e.

[0045] The second surface 52b is the rear surface of the first cemented lens 52. The second surface 52b intersects with the optical axis J. The second surface 52b has a generally mortar-shaped configuration that is recessed toward the object side (+Z side). The radial outer edge of the second surface 52b is disposed at a radial distance from the inner circumferential surface of the cylindrical portion 35. The third surface 52c connects the second surface 52b and the first outer circumferential portion 52e. The third surface 52c is an inclined surface that is positioned toward the object side as it extends radially outward. The third surface 52c faces between the base end side (-Z side) and the radially outward side.

[0046] The second cemented lens 53 is, for example, a biconvex lens. The second cemented lens 53 may have a lens of another shape. The second cemented lens 53 has a fourth surface 53a, a fifth surface 53b, and a second outer peripheral portion 53d. The second outer peripheral portion 53d is a surface facing radially outward of the second cemented lens 53. The first outer peripheral surface 51a of the first lens 51 is composed of a first outer peripheral portion 52e and a second outer peripheral portion 53d. As shown in FIGS. 3 and 4 , in this embodiment, the object-side (+Z side) portion of the second outer peripheral portion 53d contacts the inner peripheral surface of the sixth cylindrical portion 36. This determines the radial position of the first lens 51 relative to the lens frame 34. The base-end side (-Z side) portion of the second outer peripheral portion 53d faces the stepped surface 36b with a radial gap therebetween. This means that the stepped surface 36b faces a portion of the first outer peripheral surface 51a with a circumferential gap therebetween. In this embodiment, the step surface 36b faces a part of the first outer peripheral surface 51a with a gap therebetween over the entire circumference. As shown in Fig. 5, the base end side portion of the second outer peripheral portion 53d is exposed to the outside of the lens frame 34 through the through hole 36c. As a result, the first outer peripheral surface 51a is exposed to the outside of the lens frame 34 through the through hole 36c.

[0047] As shown in FIG. 3 , the fourth surface 53a is the front surface of the second cemented lens 53. The fourth surface 53a intersects with the optical axis J. The fourth surface 53a is cemented to the second surface 52b of the first cemented lens 52. In this embodiment, the fourth surface 53a is adhesively fixed to the second surface 52b with an optical adhesive. The radially outer edge of the fourth surface 53a is connected to the second outer periphery 53d. A gap is provided between the radially outer edge of the fourth surface 53a and the third surface 52c of the first cemented lens 52. As a result, when the first lens 51 is viewed from between the base end side (−Z side) and the radially outer side, the third surface 52c can be seen.

[0048] In this embodiment, the bonding portion 51c is a bonding portion between the first cemented lens 52 and the second cemented lens 53. In this embodiment, the bonding portion 51c is configured by the second surface 52b, the third surface 52c, and the fourth surface 53a. As described above, a gap is provided between the radial outer edge of the fourth surface 53a and the third surface 52c of the first cemented lens 52. Therefore, in this embodiment, the third surface 52c is visible from outside the first lens 51. That is, in this embodiment, the bonding portion 51c is visible from outside the first lens 51. In this embodiment, the bonding portion 51c is covered from the radial outside by the sixth cylindrical portion 36. Therefore, in this embodiment, the bonding portion 51c of the first lens 51 is not visible from outside the lens frame 34.

[0049] The fifth surface 53b is the rear surface of the second cemented lens 53. The fifth surface 53b intersects with the optical axis J. The radial outer edge of the fifth surface 53b is connected to the second outer periphery 53d.

[0050] In this embodiment, light rays (not shown) pass through the first surface 52a and the second surface 52b of the first cemented lens 52 and the fourth surface 53a and the fifth surface 53b of the second cemented lens 53 toward the base end (-Z side). Therefore, during the manufacturing of the first cemented lens 52, the first surface 52a and the second surface 52b are each cut and then polished. During the manufacturing of the second cemented lens 53, the fourth surface 53a and the fifth surface 53b are each cut and then polished. This allows the first surface 52a, the second surface 52b, the fourth surface 53a, and the fifth surface 53b to be formed into a mirror-like surface. This prevents light rays from scattering when passing through the first lens 51, thereby preventing degradation of the optical image of the subject. In this embodiment, the light rays do not pass through the third surface 52c. Therefore, in this embodiment, the third surface 52 c is not polished after being cut. Therefore, the surface roughness of the third surface 52 c is greater than the surface roughness of the fourth surface 53 a. As described above, in this embodiment, the third surface 52 c is not polished, so that an increase in the number of manufacturing steps and manufacturing costs of the first cemented lens 52 can be suppressed.

[0051] The adhesive 60 adhesively fixes the lens frame 34 and the first lens 51. In this embodiment, the adhesive 60 has a first adhesive portion 60a and a second adhesive portion 60b. The first adhesive portion 60a is filled between the stepped surface 36b of the lens frame 34 and the first outer peripheral surface 51a of the first lens 51. In other words, the adhesive 60 is filled between the stepped surface 36b and the first outer peripheral surface 51a. The first adhesive portion 60a adhesively fixes the stepped surface 36b and the first outer peripheral surface 51a. Although not shown in the drawings, the first adhesive portion 60a is filled around the entire circumference in the circumferential direction between the stepped surface 36b and the first outer peripheral surface 51a. The first adhesive portion 60a adhesively fixes the stepped surface 36b and the first outer peripheral surface 51a. In this way, the adhesive 60 adhesively fixes the lens frame 34 and the first lens 51. In this embodiment, the first adhesive portion 60a adhesively fixes the stepped surface 36b and the first outer peripheral surface 51a over the entire circumference in the circumferential direction.

[0052] The second adhesive portions 60b are disposed inside each through-hole portion 36c. The second adhesive portions 60b adhesively fix the inner surface of each through-hole portion 36c to the first outer peripheral surface 51a. As a result, the inner surface of the through-hole portion 36c is fixed to the first outer peripheral surface 51a by the adhesive 60. Therefore, the adhesive 60 adhesively fixes the lens frame 34 to the first lens 51. Note that in this embodiment, the adhesive 60 can be, for example, a thermosetting adhesive such as an epoxy resin adhesive, a melamine resin adhesive, or a phenol resin adhesive.

[0053] FIG. 6 is a second perspective view showing a portion of the imaging unit 30 of this embodiment. FIG. 7 is a perspective view showing a portion of an imaging unit 130 of a comparative example. As shown in FIG. 6, the diaphragm member 45 has a circular plate shape extending in the radial direction. The plate surface of the diaphragm member 45 faces the optical axis direction. As shown in FIG. 2, the diaphragm member 45 is disposed between the first optical system 50 and the second optical system 59 in the optical axis direction. The diaphragm member 45 limits the amount of light incident from the first optical system 50 to the second optical system 59. As shown in FIGS. 3 and 4, the radial outer edge of the diaphragm member 45 is fixed to the fixing surface 36e. In this embodiment, the diaphragm member 45 is adhesively fixed to the fixing surface 36e. As a result, the diaphragm member 45 is fixed to the end of the base end side (-Z side) of the tubular portion 35. As shown in FIG. 6, the diaphragm member 45 has an opening 45a and a recess 45c.

[0054] 2, the opening 45a is a hole that penetrates the diaphragm member 45 in the optical axis direction. When viewed from the optical axis direction, the opening 45a has a substantially circular shape centered on the optical axis J. Of the light rays that pass through the first optical system 50 toward the base end side (-Z side), those that pass through the opening 45a pass through the diaphragm member 45. This makes it possible to limit the amount of light rays that enter the second optical system 59 and the image sensor (not shown).

[0055] As shown in FIG. 6 , the recess 45c is provided on the radial outer edge of the diaphragm member 45. The recess 45c is recessed radially inward from the radial outer edge of the diaphragm member 45. In this embodiment, the recess 45c penetrates the diaphragm member 45 in the optical axis direction. The recess 45c may be recessed from the surface of the diaphragm member 45 facing the object side (+Z side) to the base end side (-Z side). In this embodiment, the shape of the recess 45c is substantially the same as the shape of the protrusion 37 when viewed from the optical axis direction. The protrusion 37 passes through the recess 45c in the optical axis direction. In this embodiment, the protrusion 37 is loosely fitted into the recess 45c. This allows the radial and circumferential positions of the diaphragm member 45 relative to the lens frame 34 to be determined with high precision. Therefore, the radial position of the diaphragm member 45 relative to the optical axis J can be determined with high precision.

[0056] In this embodiment, the diaphragm member 45 is provided with a plurality of recesses 45c. The recesses 45c are arranged at intervals from one another in the circumferential direction. Different protrusions 37 are loosely fitted into the recesses 45c, respectively. This makes it possible to determine with greater precision the radial and circumferential positions of the diaphragm member 45 relative to the lens frame 34. Therefore, it is possible to determine with greater precision the radial position of the diaphragm member 45 relative to the optical axis J.

[0057] 7 , the total length of the circumferential dimensions of each of the multiple protrusions 137 of the lens frame 134 is longer than the total length of the circumferential dimensions of the portions of the lens frame 134 other than the multiple protrusions 137. As a result, in the imaging unit 130 of the comparative example, the circumferential length over which each protrusion 137 and each recess 145c are gap-fitted tends to be long, and therefore the amount of light rays leaking from the gaps between each protrusion 137 and each recess 145c toward the second optical system 59 tends to increase. In other words, in the imaging unit 130 of the comparative example, the amount of light rays leaking from the gaps between the lens frame 134 and the diaphragm member 145 toward the second optical system 59 tends to increase.

[0058] 6 , as described above, the total length of the circumferential dimensions of each of the plurality of protrusions 37 is shorter than the total length of the circumferential dimensions of the portions of the lens frame 34 other than the plurality of protrusions 37. This makes it easier to shorten the length of the clearance fit between each protrusion 37 and each recess 45c compared to the imaging unit 130 of the comparative example, thereby suppressing an increase in the amount of light rays leaking from the gaps between each protrusion 37 and each recess 45c toward the second optical system 59. In other words, it is possible to suppress an increase in the amount of light rays leaking from the gaps between the lens frame 34 and the diaphragm member 45 toward the second optical system 59. Therefore, it is possible to suppress an increase in the amount of light rays incident on the imaging element (not shown).

[0059] FIG. 8 is a flowchart showing the fixing step S1 of the imaging unit 30 of this embodiment. FIG. 9 is a cross-sectional view showing the filling step S02 of this embodiment. FIG. 10 is a cross-sectional view showing the diaphragm member attachment step S03 of this embodiment. Next, the fixing step S1 of fixing the first lens 51 to the lens frame 34 in this embodiment will be described. The fixing step S1 is part of the assembly process of the imaging unit 30. As shown in FIG. 8 , the fixing step S1 includes a first lens attachment step S01 of attaching the first lens 51 to the lens frame 34, a filling step S02 of filling uncured adhesive 60 between the stepped surface 36 b and the first outer peripheral surface 51 a, an diaphragm member attachment step S03 of attaching the diaphragm member 45 to the lens frame 34, and a curing step S04 of curing the uncured adhesive 60 to fix the first lens 51 to the lens frame 34. In the following description, the term "workers, etc." includes workers performing the respective steps and assembly equipment, etc. The work in each process may be performed by a worker alone, by an assembly device alone, or by a worker and an assembly device.

[0060] In the first lens attachment step S01, the first lens 51 is attached to the lens frame 34. The worker inserts the first lens 51 into the sixth cylindrical portion 36 from the base end side (-Z side) of the lens frame 34, which is fixed to a jig or the like. As shown in FIG. 9 , the worker inserts the first lens 51 into the sixth cylindrical portion 36 until the radially outer edge of the first surface 52a of the first cemented lens 52 contacts the protrusion 35k in the optical axis direction, completing the first lens attachment step S01. At this time, the protrusion 35k determines the position of the first lens 51 in the optical axis direction relative to the lens frame 34. The first outer peripheral surface 51a is also supported in the radial direction by the inner peripheral surface of the sixth cylindrical portion 36. As a result, the first lens 51 is attached to the lens frame 34. Note that in the first lens attachment step S01, a lens other than the first lens 51 constituting the first optical system 50 may be attached to the lens frame 34.

[0061] In the filling step S02, uncured adhesive 60 is filled between the step surface 36b and the first outer peripheral surface 51a. In this embodiment, an operator uses a filling jig 91 capable of injecting uncured adhesive 60 to pour the uncured adhesive 60 between the step surface 36b and the first outer peripheral surface 51a through each through-hole 36c. This allows the operator to fill the adhesive 60 between the step surface 36b and the first outer peripheral surface 51a through the through-hole 36c. The operator can use capillary action between the step surface 36b and the first outer peripheral surface 51a to cause the uncured adhesive 60 to flow in the circumferential direction. This prevents the adhesive 60 that has flowed between the step surface 36b and the first outer peripheral surface 51a from leaking onto the fifth surface 53b of the second cemented lens 53. This prevents the uncured adhesive 60 from adhering to the fifth surface 53b. This prevents adhesive 60 from adhering to the first surface 52a and the fifth surface 53b of first lens 51 within the effective light width of first lens 51, which is the region through which light passing through opening 45a of diaphragm member 45 passes. When an operator fills uncured adhesive 60 between step surface 36b and first outer peripheral surface 51a around the entire circumference, an uncured first adhesive portion 60a is formed, and filling step S02 is completed. At this time, a portion of uncured adhesive 60 comes into contact with the inner surface of through-hole portion 36c. This forms an uncured second adhesive portion 60b.

[0062] In the diaphragm member attachment step S03, the diaphragm member 45 is attached to the lens frame 34. First, the worker applies an adhesive (not shown) to at least one of the fixing surface 36e and the diaphragm member 45. In this embodiment, the adhesive is preferably a thermosetting adhesive. The adhesive may be made of the same material as the adhesive 60 or a different material from the adhesive 60. Next, as shown in FIG. 10 , the worker moves the diaphragm member 45 from the base end side (−Z side) of the lens frame 34 toward the object side (+Z side), and attaches the diaphragm member 45 to the fixing surface 36e as shown in FIG. 3 while passing the different protrusions 37 through the recesses 45c in the optical axis direction. Once the worker attaches the diaphragm member 45 to the lens frame 34, the diaphragm member attachment step S03 is complete.

[0063] In the curing step S04, the uncured adhesive 60 is cured to fix the first lens 51 to the lens frame 34. The worker heats the lens frame 34, for example, in a heating furnace. As a result, when the uncured adhesive 60 is cured, the first lens 51 is fixed to the lens frame 34 by the first adhesive portion 60a and the second adhesive portion 60b. In other words, the first lens 51 is fixed to the lens frame 34 by the adhesive 60. Furthermore, the adhesive applied to at least one of the fixing surface 36e and the diaphragm member 45 is cured, so that the diaphragm member 45 is adhesively fixed to the lens frame 34. When the worker cures the uncured adhesive 60 to adhesively fix the first lens 51 to the lens frame 34, the curing step S04 is completed. When the curing step S04 is completed, the fixing step S1 is completed. 3 and 4, the first lens 51 and the diaphragm member 45 are each fixed to the lens frame 34. The diaphragm member attachment step S03 may be a step subsequent to the curing step S04. In this case, it is preferable to cure the uncured adhesive that bonds and fixes the diaphragm member 45 and the lens frame 34 in a step subsequent to the diaphragm member attachment step S03.

[0064] According to this embodiment, the imaging unit 30 includes a lens frame 34 having a cylindrical tubular portion 35 that extends in the optical axis direction around the optical axis J, and a first optical system 50 composed of a plurality of lenses. The first optical system 50 includes a first lens 51 held on the inner circumferential surface of the tubular portion 35. The tubular portion 35 has a step portion 36a that is recessed radially outward from the inner circumferential surface of the tubular portion 35 about the optical axis J, a step surface 36b that is the inner surface of the step portion 36a and faces a portion of a first outer circumferential surface 51a, which is the surface of the first lens 51 that faces radially outward, with a gap therebetween along the circumferential direction, and a through-hole portion 36c that penetrates the tubular portion 35 in a direction intersecting the optical axis direction and is connected to the step surface 36b. The first outer circumferential surface 51a is exposed to the outside of the lens frame 34 via the through-hole portion 36c, and an adhesive 60 is filled between the step surface 36b and the first outer circumferential surface 51a. Therefore, as described above, in the fixing step S1, after the first lens 51 is attached to the lens frame 34 in the first lens attachment step S01, the uncured adhesive 60 can be filled between the step surface 36b and the first outer peripheral surface 51a through the through-hole portion 36c in the filling step S02. This makes it possible to prevent the adhesive 60 from adhering to the effective light width of the surface of the first lens 51 in the filling step S02, thereby eliminating the need for the work of removing the adhesive 60 from the surface of the first lens 51 in the fixing step S1. This makes it possible to prevent an increase in the number of steps in the fixing step S1, and therefore to prevent an increase in the number of steps in assembling the imaging unit 30.

[0065] Furthermore, in this embodiment, as described above, the step surface 36b faces the first outer peripheral surface 51a with a gap therebetween over the entire circumference. This allows the adhesive 60 to be filled between the step surface 36b and the first outer peripheral surface 51a over the entire circumference, thereby adhesively fixing the step surface 36b to the first outer peripheral surface 51a over the entire circumference. This increases the bonding area between the lens frame 34 and the first lens 51 compared to a configuration in which only a portion of the first outer peripheral surface 51a is adhesively fixed to the step surface 36b over the entire circumference. This therefore advantageously increases the bonding strength between the lens frame 34 and the first lens 51.

[0066] According to this embodiment, the inner surface of the through-hole portion 36c and the first outer peripheral surface 51a are fixed with the adhesive 60. Therefore, the first outer peripheral surface 51a is adhesively fixed to the inner surface of the through-hole portion 36c in addition to the step surface 36b, which makes it possible to more preferably increase the bonding area between the lens frame 34 and the first lens 51. Therefore, it is possible to more preferably increase the bonding strength between the lens frame 34 and the first lens 51.

[0067] According to this embodiment, the first lens 51 is the lens arranged furthest from the base end (negative Z side) among the multiple lenses constituting the first optical system 50, and the through-hole portion 36c is open toward the base end. Therefore, compared to a case where the through-hole portion 36c is a hole that is not open toward the base end, it is easier to increase the area of ​​the through-hole portion 36c as viewed from the radial direction. Therefore, in the filling step S02, it is easier to fill the gap between the step surface 36b and the first outer peripheral surface 51a through the through-hole portion 36c. Therefore, an increase in the number of steps in the filling step S02 can be suppressed, and therefore an increase in the number of steps in the fixing step S1 can be more effectively suppressed. Therefore, an increase in the number of steps in the assembly of the imaging unit 30 can be more effectively suppressed.

[0068] According to this embodiment, the cylindrical portion 35 has a plurality of through-holes 36c, each of which is spaced apart from one another in the circumferential direction. Therefore, the adhesive 60 can be filled between the stepped surface 36b and the first outer peripheral surface 51a through each through-hole 36c. This makes it easier to fill the gap between the stepped surface 36b and the first outer peripheral surface 51a along the circumferential direction compared to a configuration in which the cylindrical portion 35 has only one through-hole 36c. In this embodiment, the adhesive 60 can be easily filled between the stepped surface 36b and the first outer peripheral surface 51a all around the circumference. This makes it easier to bond and fix the stepped surface 36b and the first outer peripheral surface 51a. This prevents an increase in the number of steps in the filling step S02, thereby more effectively preventing an increase in the number of steps required to assemble the imaging unit 30.

[0069] The imaging unit 30 has an annular plate shape extending radially and includes an aperture member 45 fixed to the end of the base end (-Z side) of the cylindrical portion 35. The radial outer edge of the aperture member 45 is provided with a recess 45c recessed radially inward. The lens frame 34 has a protrusion 37 protruding from the base end of the cylindrical portion 35 toward the base end, and the protrusion 37 is gap-fitted into the recess 45c. Therefore, as described above, in the aperture member attachment step S03, the radial position of the aperture member 45 relative to the optical axis J can be accurately determined by the simple operation of moving the aperture member 45 from the base end (-Z side) of the lens frame 34 toward the object side (+Z side) and passing the protrusion 37 through the recess 45c. This eliminates the need for the operation of adjusting the radial position of the aperture member 45 relative to the optical axis J in the aperture member attachment step S03, thereby suppressing an increase in the number of steps required for the aperture member attachment step S03. Therefore, an increase in the number of steps required to assemble the imaging unit 30 can be suppressed.

[0070] Furthermore, in this embodiment, the radial positional accuracy of the diaphragm member 45 relative to the optical axis J can be improved, and therefore the radial positional accuracy of the opening 45a relative to the optical axis J can be improved. Therefore, the quality of the optical image formed by the endoscope 2 can be improved.

[0071] Furthermore, in this embodiment, as described above, each fixing surface 36e and each protrusion 37 is arranged along the circumferential direction. Therefore, compared to a configuration in which the radial position of the diaphragm member 45 with respect to the optical axis J is determined by fitting the diaphragm member 45 into a circular recess recessed from the surface facing the base end side (-Z side) of the tubular portion 35 toward the object side (+Z side), it is possible to prevent the radial thickness of the tubular portion 35 from increasing. This makes it easy to reduce the outer diameter of the lens frame 34, which makes it easy to prevent an increase in the radial dimension of the imaging unit 30. Therefore, it is easy to prevent an increase in the radial dimension of the endoscope 2.

[0072] According to this embodiment, the diaphragm member 45 is provided with a plurality of recesses 45c arranged along the circumferential direction, the lens frame 34 has a plurality of protrusions 37 arranged along the circumferential direction, and different protrusions 37 are gap-fitted into each of the plurality of recesses 45c. Therefore, the radial position of the diaphragm member 45 can be determined by the plurality of protrusions 37, and the radial position of the diaphragm member 45 relative to the optical axis J can be determined with greater precision. This makes it possible to more suitably improve the quality of the optical image formed by the endoscope 2.

[0073] According to this embodiment, the total length of the circumferential dimensions of each of the multiple protrusions 37 is shorter than the total length of the circumferential dimensions of the lens frame 34 other than the multiple protrusions 37. Therefore, as described above, it is easy to shorten the length of the clearance fit between each protrusion 37 and each recess 45c. This makes it possible to suppress an increase in the amount of light rays leaking toward the second optical system 59 from the gap between the lens frame 34 and the diaphragm member 45. This in turn makes it possible to suppress an increase in the amount of light rays entering an imaging element (not shown). Therefore, the quality of the optical image formed by the endoscope 2 can be more suitably improved.

[0074] According to this embodiment, the imaging unit 30 includes a main body frame 31 that houses a lens frame 34, and the lens frame 34 has a flange portion 38 that protrudes radially outward from the cylindrical portion 35, and the flange portion 38 is adhesively fixed to the main body frame 31. Therefore, compared to a configuration in which the lens frame 34 does not have the flange portion 38, the adhesive area between the lens frame 34 and the main body frame 31 can be made larger. Therefore, the adhesive strength between the lens frame 34 and the main body frame 31 can be increased.

[0075] Furthermore, in this embodiment, as described above, the flange portion 38 contacts the main body frame 31 in the optical axis direction, so the position of the lens frame 34 in the optical axis direction relative to the main body frame 31 can be determined with high precision. This makes it possible to determine with high precision the position of the first optical system 50 in the optical axis direction relative to the imaging element (not shown). Therefore, the quality of the optical image formed by the endoscope 2 can be more suitably improved.

[0076] According to this embodiment, the endoscope 2 includes the imaging unit 30 at the tip of the insertion section 9. As described above, in this embodiment, the filling step S02 can prevent the adhesive 60 from adhering within the effective light width on the surface of the first lens 51, and therefore, in the fixing step S1, the task of removing the adhesive 60 from the surface of the first lens 51 is not required. Therefore, an increase in the number of steps for assembling the imaging unit 30 included in the endoscope 2 can be prevented, and therefore an increase in the number of steps for assembling the endoscope 2 can be prevented.

[0077] According to this embodiment, the lens frame 34 is a lens frame 34 provided in the imaging unit 30, and has a cylindrical tubular portion 35 that extends in the optical axis direction centered on the optical axis J and accommodates a plurality of lenses, the inner surface of the tubular portion 35 holds a first lens 51 included in the plurality of lenses, the tubular portion 35 has a step portion 36a that is recessed radially outward from the inner surface of the tubular portion 35, a step surface 36b that is the inner surface of the step portion 36a and faces a part of the first outer surface 51a, which is the surface facing radially outward of the first lens 51, with a gap in the circumferential direction, and a through-hole portion 36c that penetrates the tubular portion 35 in a direction intersecting the optical axis direction and is connected to the step surface 36b, and the first outer surface 51a is exposed to the outside of the lens frame 34 via the through-hole portion 36c. Therefore, as described above, in the filling step S02, the uncured adhesive 60 can be filled between the step surface 36b and the first outer peripheral surface 51a through the through-hole portion 36c. This, as described above, in the filling step S02, can prevent the adhesive 60 from adhering to the surface of the first lens 51 within the effective light width, thereby preventing an increase in the number of steps in the fixing step S1. Therefore, an increase in the number of steps for assembling the imaging unit 30 can be prevented.

[0078] Furthermore, in this embodiment, as described above, the adhesive 60 can be filled between the step surface 36b and the first outer peripheral surface 51a all around the circumference, thereby increasing the bonding area between the lens frame 34 and the first lens 51. This makes it possible to suitably increase the bonding strength between the lens frame 34 and the first lens 51.

[0079] Second Embodiment Fig. 11 is an enlarged cross-sectional view showing a portion of an imaging unit 230 of this embodiment. Fig. 12 is a perspective view showing a portion of an imaging unit 230 of this embodiment. In the following description, the same components as those in the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted. As shown in Fig. 11 , in this embodiment, the imaging unit 230 provided in the endoscope 202 includes a main body frame 31 (see Fig. 2 ), a lens frame 234, a second lens frame 39 (see Fig. 2 ), an aperture member 45, a first optical system 50, and a second optical system 59 (see Fig. 2 ).

[0080] The lens frame 234 has a cylindrical shape extending in the optical axis direction. In this embodiment, the lens frame 234 has a substantially cylindrical shape extending in the optical axis direction with the optical axis J as its center. Although not shown, the lens frame 234 is fixed to the main body frame 31. The lens frame 234 has a cylindrical portion 235, a protrusion 37, and a flange portion 38. The configurations of the protrusion 37 and the flange portion 38 in this embodiment are similar to the configurations of the protrusion 37 and the flange portion 38 in the first embodiment described above.

[0081] The cylindrical portion 235 has a cylindrical shape extending in the optical axis direction with the optical axis J as its center. The cylindrical portion 235 has a first cylindrical portion 35a (see FIG. 2), a second cylindrical portion 35c (see FIG. 2), a third cylindrical portion 35e (see FIG. 2), a fourth cylindrical portion 35g (see FIG. 2), a fifth cylindrical portion 35i, and a sixth cylindrical portion 236.

[0082] The sixth cylindrical portion 236 has a cylindrical shape that extends in the optical axis direction with the optical axis J as its center. The sixth cylindrical portion 236 is disposed closer to the base end (-Z side) than the fifth cylindrical portion 35i. The sixth cylindrical portion 236 is connected to the fifth cylindrical portion 35i in the optical axis direction. The inner circumferential surface of the sixth cylindrical portion 236 holds the first lens 51. The sixth cylindrical portion 236 has a step portion 236a, a step surface 36b, a through-hole portion 236c, and a fixing surface 36e. That is, the cylindrical portion 235 has the step portion 236a, the step surface 236b, the through-hole portion 236c, and the fixing surface 36e.

[0083] The step portion 236a is a recess recessed radially outward from the inner circumferential surface of the sixth cylindrical portion 236. That is, the step portion 236a is recessed radially outward from the inner circumferential surface of the cylindrical portion 235 about the optical axis J. Although not shown, the step portion 236a extends in the circumferential direction. In this embodiment, the step portion 236a extends all the way around in the circumferential direction. The step surface 236b does not have to extend all the way around in the circumferential direction. In this embodiment, the base end side (−Z side) end of the step portion 236a is located at the base end side end of the sixth cylindrical portion 236. When viewed in the radial direction, the object side (+Z side) end of the step portion 236a overlaps with the first outer circumferential portion 52e of the first cemented lens 52. In this embodiment, the object side end of the step portion 236 a is located closer to the object side than the joint portion 51 c of the first lens 51 .

[0084] The step surface 236b is an inner surface of the step portion 236a and faces radially inward. The step surface 236b faces a portion of the first outer peripheral surface 51a of the first lens 51 on the base end side (-Z side) of the first outer peripheral portion 52e and the entire second outer peripheral portion 53d with a gap in the radial direction. Although not shown, the step surface 236b extends in the circumferential direction. The step surface 236b faces a portion of the first outer peripheral surface 51a with a gap in the circumferential direction centered on the optical axis J. In this embodiment, the step surface 236b extends all the way around in the circumferential direction. In this embodiment, the step surface 236b faces a portion of the first outer peripheral surface 51a with a gap in the circumferential direction. Note that the step surface 236b does not have to extend all the way around in the circumferential direction.

[0085] As shown in FIG. 12 , the through-hole portion 236c is a hole that penetrates the sixth cylindrical portion 236 in a direction intersecting the optical axis direction. In this embodiment, the through-hole portion 236c is a hole that penetrates the sixth cylindrical portion 236 in the radial direction. The through-hole portion 236c is open on the base end side (−Z side). As shown in FIG. 11 , the through-hole portion 236c is connected to the step surface 236b. As a result, the interior of the through-hole portion 236c is connected to the gap between the step surface 236b and the first outer peripheral surface 51a. In this embodiment, the object-side (+Z side) end of the through-hole portion 236c is located closer to the object than the joint portion 51c. Therefore, as shown in FIG. 12 , in this embodiment, the joint portion 51c between the first cemented lens 52 and the second cemented lens 53 is exposed to the outside of the lens frame 234 through the through-hole portion 236c.

[0086] In this embodiment, the cylindrical portion 235 has a plurality of through-holes 236c. In this embodiment, the cylindrical portion 235 has four through-holes 236c. Although not shown in the drawings, each through-hole 236c is connected to the step surface 236b. Therefore, the interior of each through-hole 236c is connected to the gap between the step surface 236b and the first outer peripheral surface 51a. In this embodiment, the joint 51c between the first cemented lens 52 and the second cemented lens 53 is exposed to the outside of the lens frame 234 through each through-hole 236c. Other configurations of the lens frame 234 of this embodiment are similar to those of the lens frame 34 of the first embodiment described above.

[0087] As shown in FIG. 11 , the object-side (+Z side) portion of the first outer peripheral portion 52e of the first cemented lens 52 contacts the inner peripheral surface of the sixth cylindrical portion 236. This determines the radial position of the first lens 51 relative to the lens frame 234. As shown in FIG. 12 , the third surface 52c is exposed to the outside of the lens frame 234 via the through-hole portion 236c. This allows the third surface 52c to be seen when viewing the lens frame 234, to which the first lens 51 is fixed, from between the base end side (−Z side) and the radially outer side. As described above, the fourth surface 53a is polished after being cut. Therefore, as described above, the fourth surface 53a is formed into a mirror-like finish. Furthermore, as described above, the third surface 52c is not polished after being cut. Therefore, as described above, the surface roughness of the third surface 52c is greater than the surface roughness of the fourth surface 53a. Therefore, in this embodiment, when the joint portion 51c of the first lens 51 is viewed through the through-hole portion 236c, the amount of light reflected by the third surface 52c is smaller than the amount of light reflected by the fourth surface 53a.

[0088] The adhesive 260 shown in FIG. 11 adhesively fixes the lens frame 234 and the first lens 51. The adhesive 260 has a first adhesive portion 260a and a second adhesive portion 260b. The first adhesive portion 260a is filled between the stepped surface 236b of the lens frame 234 and the first outer peripheral surface 51a of the first lens 51. Although not shown, the first adhesive portion 260a is filled between the stepped surface 236b and the first outer peripheral surface 51a along the entire circumferential direction. The first adhesive portion 260a adhesively fixes the stepped surface 236b and the first outer peripheral surface 51a. In this embodiment, the first adhesive portion 260a adhesively fixes the stepped surface 236b and the first outer peripheral surface 51a along the entire circumferential direction.

[0089] The second adhesive portions 260b are disposed inside each through-hole portion 236c. The second adhesive portions 260b adhesively fix the inner surface of each through-hole portion 236c to the first outer peripheral surface 51a. As a result, the inner surface of the through-hole portion 236c is fixed to the first outer peripheral surface 51a by the adhesive 260. Therefore, the adhesive 260 adhesively fixes the lens frame 234 to the first lens 51. Other configurations of the adhesive 260 of this embodiment are similar to other configurations of the adhesive 60 of the first embodiment described above. Other configurations of the imaging unit 230 of this embodiment are similar to other configurations of the imaging unit 30 of the first embodiment described above. Furthermore, the assembly procedure of the fixing step S1 of the imaging unit 230 of this embodiment is similar to the assembly procedure of the fixing step S1 of the imaging unit 30 of the first embodiment described above.

[0090] According to this embodiment, the first lens 51 is a cemented lens formed by cementing together a first cemented lens 52 and a second cemented lens 53 that are arranged side by side in the optical axis direction, and the cemented portion 51c of the first cemented lens 52 and the second cemented lens 53 is exposed to the outside of the lens frame 234 through the through-hole 236c. As described above, in this embodiment, the surface roughness of the third surface 52c is greater than the surface roughness of the fourth surface 53a. Therefore, as described above, the amount of reflected light on the third surface 52c is smaller than the amount of reflected light on the fourth surface 53a. Therefore, after attaching the first lens 51 to the lens frame 234 in the first lens attachment step S01, an operator or the like can visually check the cemented portion 51c from between the base end side (-Z side) and the radially outer side through the through-hole 236c. If the amount of reflected light on the radially outer edge of the cemented portion 51c is small, the operator or the like can determine that the third surface 52c faces between the base end side and the radially outer side. This allows the worker to confirm that the first lens 51 is attached to the lens frame 234 in the correct orientation in the optical axis direction. On the other hand, if the amount of reflected light from the radially outer edge of the joint 51c is large, the worker can confirm that the fourth surface 53a faces between the base end side and the radially outward direction. This allows the worker to confirm that the first lens 51 is attached to the lens frame 234 in the reverse orientation in the optical axis direction. If the worker confirms that the first lens 51 is attached to the lens frame 234 in the reverse orientation in the optical axis direction, the worker can remove the first lens 51 from the lens frame 234, then correctly orient the first lens 51 in the optical axis direction and attach the first lens 51 to the lens frame 234. This prevents the first lens 51 from being adhesively fixed to the lens frame 234 in the reverse orientation in the optical axis direction in the curing step S04, thereby preventing an increase in the number of steps required to manufacture the imaging unit 230.

[0091] Furthermore, in this embodiment, the first outer peripheral surface 51a is exposed to the outside of the lens frame 234 via the through-hole portion 236c, and the gap between the stepped surface 236b and the first outer peripheral surface 51a is filled with adhesive 260. Therefore, similar to the first embodiment described above, in the filling step S02, uncured adhesive 260 can be filled between the stepped surface 236b and the first outer peripheral surface 51a via the through-hole portion 236c. This prevents the adhesive 260 from adhering to the effective light width of the surface of the first lens 51 in the filling step S02, thereby eliminating the need to remove the adhesive 260 from the surface of the first lens 51 in the fixing step S1. Therefore, an increase in the number of steps in the fixing step S1 can be suppressed, and an increase in the number of steps for assembling the imaging unit 230 can be suppressed.

[0092] Although the embodiments of the present invention have been described above, the configurations and combinations thereof in the embodiments are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments.

[0093] The configuration of the imaging unit is not limited to this embodiment, and for example, the main body frame and the second lens frame may be integrally configured. That is, the main body frame and the second holding frame may be part of the same single member. Furthermore, the second lens frame may be fixed to the main body frame.

[0094] The first lens is not limited to a cemented lens in which two lenses, the first cemented lens and the second cemented lens, are cemented together, but may be composed of a single lens, or may be a cemented lens in which three or more lenses are cemented together.

[0095] The fixing step is not limited to this embodiment, and for example, the filling step may be performed after the diaphragm member attaching step and before the curing step, and the diaphragm member attaching step may be performed before the first lens attaching step.

[0096] 2, 202... Endoscope 9... Insertion section 30, 230... Imaging unit 31... Main body frame 34, 234... Lens frame 35, 235... Cylindrical section 36a, 236a... Step section 36b, 236b... Step surface 36c, 236c... Through-hole section 37... Projection section 38... Flange section 45... Aperture member 45c... Recess 50... First optical system 51... First lens 51a... First outer peripheral surface 52... First cemented lens 53... Second cemented lens 60, 260... Adhesive J... Optical axis

Claims

1. An imaging unit comprising: a lens frame having a cylindrical tubular portion extending in the optical axis direction with the optical axis as its center; and a first optical system constituted by a plurality of lenses, wherein the first optical system includes a first lens held on the inner peripheral surface of the tubular portion, and the tubular portion has: a stepped portion recessed from the inner peripheral surface of the tubular portion outward in a radial direction centered on the optical axis; a stepped surface that is an inner surface of the stepped portion and faces a part of a first outer peripheral surface that is the surface of the first lens facing outward in the radial direction, with a gap in between along a circumferential direction centered on the optical axis; and a through-hole portion that penetrates the tubular portion in a direction intersecting the optical axis direction and is connected to the stepped surface, wherein the first outer peripheral surface is exposed to the outside of the lens frame through the through-hole portion, and an adhesive is filled between the stepped surface and the first outer peripheral surface.

2. The imaging unit according to claim 1, wherein the inner surface of the through-hole portion and the first outer circumferential surface are fixed together with an adhesive.

3. The imaging unit according to claim 1, wherein the first lens is a cemented lens formed by cementing together a first cemented lens and a second cemented lens arranged side by side in the optical axis direction, and the cemented portion of the first cemented lens and the second cemented lens is exposed to the outside of the lens frame through the through-hole portion.

4. The imaging unit according to claim 1, wherein the first lens is the lens arranged furthest from the base end of the plurality of lenses constituting the first optical system, and the through-hole portion is open on the base end side.

5. An imaging unit according to any one of claims 1 to 4, wherein the cylindrical portion has a plurality of through-hole portions, and each of the plurality of through-hole portions is arranged at intervals from one another along the circumferential direction.

6. An imaging unit as claimed in any one of claims 1 to 4, comprising an aperture member in the shape of a circular ring plate extending in the radial direction and fixed to the base end side end of the tubular portion, wherein the outer edge of the aperture member in the radial direction is provided with a recess recessed inward in the radial direction, the lens frame has a protrusion protruding from the base end side end of the tubular portion towards the base end side, and the protrusion is loosely fitted into the recess.

7. An imaging unit as described in claim 6, wherein the aperture member is provided with a plurality of recesses arranged along the circumferential direction, the lens frame has a plurality of protrusions arranged along the circumferential direction, and different protrusions are fitted into each of the plurality of recesses with a gap.

8. An imaging unit as described in claim 7, wherein the total length of the circumferential dimensions of each of the multiple protrusions is shorter than the total length of the circumferential dimensions of the lens frame other than each of the multiple protrusions.

9. An imaging unit as described in any one of claims 1 to 4, comprising a main body frame that houses the lens frame, the lens frame having a flange portion that protrudes radially outward from the cylindrical portion, and the flange portion is adhesively fixed to the main body frame.

10. An endoscope having the imaging unit according to any one of claims 1 to 4 at the tip of an insertion section.

11. A lens frame provided in an imaging unit, comprising a cylindrical tubular portion extending in the optical axis direction around an optical axis and accommodating a plurality of lenses, wherein the inner peripheral surface of the tubular portion holds a first lens included in the plurality of lenses, and wherein the tubular portion has: a stepped portion recessed from the inner peripheral surface of the tubular portion outward in a radial direction around the optical axis; a stepped surface on the inner surface of the stepped portion facing a part of a first outer peripheral surface, which is the surface of the first lens facing outward in the radial direction, along a circumferential direction around the optical axis, with a gap between them; and a through-hole portion that penetrates the tubular portion in a direction intersecting the optical axis direction and is connected to the stepped surface, wherein the first outer peripheral surface is exposed to the outside of the lens frame via the through-hole portion.

Images