Imaging unit, endoscope, and method for assembling imaging unit

Abstract

An imaging unit according to an embodiment of the present invention is held by a distal end member of an endoscope, and comprises: a cylindrical lens barrel extending in an optical axis direction; an objective optical system formed from lenses held on an inner peripheral surface of the lens barrel; a holding member attached to the lens barrel and holding an imaging element; and a positioning member attached to the lens barrel. The positioning member has a first positioning part for determining a position in a circumferential direction around an optical axis of the holding member relative to the distal end member. One of the lens barrel and the positioning member has a second positioning part for determining a position in an optical axis direction of the lens barrel relative to the distal end member.

Description

Imaging unit, endoscope, and method for assembling imaging unit

[0001] The present invention relates to an imaging unit, an endoscope, and a method for assembling an imaging unit.

[0002] An endoscope tip section is known that determines the circumferential position of a barrel holding member relative to a support by fitting a protrusion formed on the inner peripheral surface of a support to which the barrel holding member is fixed into a groove formed on the outer peripheral surface of the barrel holding member that holds an imaging device (see, for example, Patent Document 1).With an endoscope tip section configured in this way, the circumferential position of the imaging device can be determined with high precision relative to the support, thereby suppressing so-called image tilt, which is a deviation in the circumferential orientation of an image formed by the endoscope.

[0003] Japanese Patent Application Laid-Open No. 2000-279369

[0004] In the above-described endoscope tip, the support and the barrel holder that holds the barrel housing the objective optical system are brought into contact in the optical axis direction, thereby suppressing variations in the amount of protrusion of the barrel holder from the support. However, with this configuration, if the dimensional tolerances of the support and the barrel holder are both large, the stress applied to the barrel holder tends to be large, which can cause fluctuations in the circumferential position of the image sensor relative to the support. This can result in a deterioration in the quality of the images formed by the endoscope.

[0005] In view of the above circumstances, one of the objects of the present invention is to provide an imaging unit, an endoscope, and an assembly method for an imaging unit that can accurately determine the circumferential position of the holding member relative to the tip member while suppressing the increase in stress applied to the holding member.

[0006] In order to achieve the above object, an imaging unit in one aspect of the present invention is an imaging unit held on a tip member of an endoscope, and comprises: a cylindrical lens barrel extending in the optical axis direction; an objective optical system constituted by a lens held on the inner surface of the lens barrel; a holding member attached to the lens barrel and holding an imaging element; and a positioning member attached to the lens barrel, wherein the positioning member has a first positioning portion that determines the circumferential position of the holding member relative to the tip member, centered on the optical axis, and one of the lens barrel and the positioning member has a second positioning portion that determines the position of the lens barrel in the optical axis direction relative to the tip member.

[0007] An endoscope in one aspect of the present invention comprises the above-mentioned imaging unit and a tip member that holds the imaging unit, the tip member having an insertion hole that penetrates in the optical axis direction, and the imaging unit being positioned inside the insertion hole.

[0008] In one aspect of the present invention, a method for assembling an imaging unit includes a cylindrical lens barrel extending in the optical axis direction, an objective optical system constituted by a lens held on the inner surface of the lens barrel, a holding member fixed to the lens barrel and holding an imaging element, and a positioning member fixed to the lens barrel, wherein the method for assembling the imaging unit includes a fixing process for fixing the holding member to the lens barrel, wherein the positioning member has a third positioning portion protruding toward the base end, and the holding member has a fourth positioning portion recessed toward the base end, and the fixing process includes an application process for applying adhesive to the outer surface of the lens barrel, a first attachment process for attaching the positioning member to the outer surface of the lens barrel via the adhesive, a second attachment process for attaching the holding member to the lens barrel via the adhesive while engaging the third positioning portion with the fourth positioning portion, an adjustment process for adjusting the position of the objective optical system in the optical axis direction relative to the imaging element and the circumferential position around the optical axis, and a curing process for curing the adhesive.

[0009] According to the present invention, it is possible to provide an imaging unit, an endoscope, and an assembling method for an imaging unit that can accurately determine the circumferential position of the holding member relative to the tip member while suppressing an increase in stress applied to the holding member.

[0010] FIG. 1 is a perspective view showing an endoscope system of a first embodiment. FIG. 2 is a cross-sectional view showing an insertion section of the first embodiment. FIG. 3 is a cross-sectional view showing an imaging unit of the first embodiment. FIG. 4 is an exploded perspective view showing a part of the imaging unit of the first embodiment. FIG. 5 is a flowchart showing an assembly method of the imaging unit of the first embodiment. FIG. 6 is a perspective view showing a first attachment step of the assembly method of the imaging unit of the first embodiment. FIG. 7 is a perspective view showing a second attachment step of the assembly method of the imaging unit of the first embodiment. FIG. 8 is a perspective view showing an adjustment step of the assembly method of the imaging unit of the first embodiment. FIG. 9 is a perspective view showing a part of the imaging unit of the second embodiment. FIG. 10 is a perspective view showing a second attachment step of the assembly method of the imaging unit of the second embodiment. FIG. 11 is an exploded perspective view showing a part of the imaging unit of the third embodiment. FIG. 12 is a cross-sectional view showing an imaging unit of the fourth embodiment.

[0011] An imaging unit, an endoscope, and an assembly method for an imaging unit 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 imaging unit in the embodiment described below extends. The optical axis J shown as appropriate in each figure is a virtual axis. The optical axis J is the central axis of the imaging unit. In the following description, the direction in which the optical axis J extends, that is, the direction parallel to the Z axis, will be referred to as the "optical axis 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)."

[0013] In the following description, 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 circumferential direction is indicated by the arrow θ in each drawing. The side of the circumferential direction toward which the arrow θ points will be referred to as the "one circumferential side." The side of the circumferential direction opposite to the side toward which the arrow θ points will be referred to as the "other circumferential side." The one circumferential side is the side that moves clockwise around the optical axis J when viewed from the object side (+θ side). The other circumferential side is the side that moves counterclockwise around the optical axis J when viewed from the object side (-θ side).

[0014] <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 insertion section 6 of this embodiment. Fig. 3 is a cross-sectional view showing an imaging unit 20 of this embodiment. Fig. 4 is an exploded perspective view showing a part of the imaging unit 20 of this embodiment.

[0015] 1 includes an endoscope 2 capable of capturing an image of a subject and generating an image signal of the subject, a processor 3, a light source device 4 to which the endoscope 2 is detachably connected, and a monitor 5 that displays an image of the subject based on the image signal generated by the processor 3. The processor 3 and the monitor 5 are connected by a connection cable 5a.

[0016] The endoscope 2 includes an elongated insertion section 6, an operation section 7 connected to the proximal end of the insertion section 6, and a universal cable 8 extending from the operation section 7 and connected to the light source device 4. 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.

[0017] The insertion section 6 is a portion that is inserted into, for example, the body of a subject when observing the subject. The insertion section 6 is configured by an insertion tip section 6a, a bending section 6b, and a flexible tube section 6c, which are arranged in this order from the object side, which is the tip in the insertion direction into the subject, toward the base end side connected to the operation section 7. The insertion tip section 6a is configured by a metal tube such as stainless steel. As shown in FIG. 2 , in this embodiment, the insertion tip section 6a has a substantially cylindrical shape extending in the optical axis direction. The insertion tip section 6a includes a case 18, a tip member 19, an imaging unit 20, and a container 70. That is, the tip member 19 is disposed at the tip of the insertion section 6 of the endoscope 2. The tip member 19 holds the imaging unit 20. The endoscope 2 includes the imaging unit 20 and the tip member 19 at the tip of the insertion section 6.

[0018] The case 18 accommodates the tip member 19, the imaging unit 20, and the contents 70. The case 18 holds the tip member 19, the imaging unit 20, and the contents 70. In this embodiment, the case 18 has a substantially cylindrical shape extending in the optical axis direction. The case 18 has a cylindrical portion 18a and a tip case 18c.

[0019] The cylindrical portion 18a has a generally cylindrical shape extending in the optical axis direction and is open on both sides in the optical axis direction. The signal cable 34 and the contents 70 are passed through the inside of the cylindrical portion 18a in the optical axis direction.

[0020] The tip case 18c has a generally cylindrical shape that protrudes in the optical axis direction. The tip case 18c surrounds the imaging unit 20 from the radially outer side. The tip case 18c is fixed to the end of the cylindrical portion 18a on the object side (+Z side). The tip case 18c has a tip surface 18d. The tip surface 18d is the surface of the outer surface of the insertion tip portion 6a that faces the object side. The tip surface 18d is formed with a well-known tip opening, an observation window, an illumination window, and the like.

[0021] A signal cable 34 (see FIG. 2, etc.) that electrically connects the imaging unit 20 to the operation unit 7 and the processor 3, and a light guide bundle (not shown) that transmits illumination light to the insertion tip 6a are inserted inside the curved portion 6b and the flexible tube portion 6c shown in FIG. 1.

[0022] The operation unit 7 is provided with an operation knob 7a, a forceps port 7b, and a switch 7c. The operation knob 7a is an operation means for operating the bending portion 6b to bend in four directions, up, down, left, and right. Note that the bending portion 6b is not limited to being bendable in these four directions, and may be bendable in only two directions, up and down, or only left and right, for example. The switch 7c is a switch used to adjust the focal position of the optical image of the subject formed by the light source device 4 and the imaging unit 20. The forceps port 7b is an opening that communicates with the proximal end of a treatment instrument channel that extends from the inside of the operation unit 7 through the insertion portion 6 to the tip of the insertion tip portion 6a.

[0023] A signal cable 34 (see FIG. 2 , etc.) and a light guide bundle (not shown) are inserted inside the universal cable 8. A scope connector 8b is provided at the proximal end of the universal cable 8, which optically couples illumination light from the light source device 4 that supplies illumination light to the incident end of the light guide bundle. The signal cable 34 inside the universal cable 8 extends inside a scope cable that branches off from the scope connector 8b. An electrical connector 8a that connects the signal cable 34 to the processor 3 is provided at the end of the scope cable. When the electrical connector 8a is connected to the processor 3, the signal cable 34 connects electrical components such as the imaging element 31 (see FIG. 2 ) of the imaging unit 20 to the processor 3 so that they can communicate with each other.

[0024] As shown in Fig. 2, the tip member 19 has a generally circular ring shape extending in the optical axis direction. The tip member 19 holds the imaging unit 20 and the contents 70. The tip member 19 is disposed inside the tip case 18c. The tip member 19 is fixed to the inner circumferential surface of the tip case 18c. As shown in Fig. 3, the tip member 19 has a base 19a, a tip protrusion 19g, and an abutment surface 19h. As shown in Fig. 4, the tip member 19 is provided with an insertion hole 19c and a plurality of through-holes 19i.

[0025] As shown in Fig. 2, the base 19a has a substantially circular ring shape extending in the optical axis direction. The outer peripheral surface of the base 19a is fixed to the inner peripheral surface of the tip case 18c. As shown in Fig. 3, the insertion hole 19c is a hole that penetrates the base 19a in the optical axis direction. That is, the tip member 19 is provided with the insertion hole 19c that penetrates in the optical axis direction. When viewed from the optical axis direction, the insertion hole 19c has a substantially circular shape centered on the optical axis J. The imaging unit 20 is disposed inside the insertion hole 19c. As shown in Fig. 4, a positioning hole 19e is provided in the inner peripheral surface of the insertion hole 19c.

[0026] The positioning hole 19e is a recess recessed radially outward from the inner circumferential surface of the insertion hole 19c. When viewed in the optical axis direction, the positioning hole 19e has a substantially rectangular shape. As shown in FIG. 3, the positioning hole 19e extends in the optical axis direction. The end on the base end side (-Z side) of the positioning hole 19e is located at the end on the base end side of the base 19a. As a result, as shown in FIG. 4, the positioning hole 19e is open on the base end side. As shown in FIG. 3, the end on the object side (+Z side) of the positioning hole 19e is located near the center of the base 19a in the optical axis direction.

[0027] The tip protrusion 19g protrudes radially inward from the object side (+Z side) end of the inner circumferential surface of the insertion hole 19c. In this embodiment, the tip protrusion 19g has a substantially annular shape centered on the optical axis J.

[0028] The abutment surface 19h is a surface of the outer surface of the tip protrusion 19g that faces the base end side (-Z side). When viewed from the optical axis direction, the abutment surface 19h has a substantially annular shape centered on the optical axis J. As shown in Fig. 2, the through-hole portion 19i is a hole that penetrates the base portion 19a in the optical axis direction. As shown in Fig. 4, in this embodiment, the tip member 19 is provided with a plurality of through-hole portions 19i.

[0029] As shown in FIG. 2 , the contents 70 are passed through the through-holes 19i in the optical axis direction. Although not shown, in this embodiment, the insertion tip 6a includes multiple contents 70. Each of the contents 70 is passed through a different through-hole 19i in the optical axis direction and attached to the inner circumferential surface of the through-hole 19i. In this embodiment, the multiple contents 70 include an air and water supply unit 71, a light guide unit, and a treatment tool unit. The air and water supply unit 71 is a flow path that supplies air and liquid, such as water, to the outer surface of the lens 23c, which is located closest to the object (+Z side) among the lenses 23a constituting the objective optical system 23 of the imaging unit 20. By supplying air and liquid to the outer surface of the lens 23c, bodily fluids, blood, and the like are removed from the lens 23c. In this way, the air and water supply unit 71 cleans the lens 23c. The air and water supply unit 71 is connected to a pump (not shown) that pumps air and liquid. The light guide unit (not shown) is an optical path for irradiating the subject with light. The proximal end of the light guide unit is connected to the light guide bundle. The treatment tool unit (not shown) houses treatment tools such as forceps, a snare, and a syringe needle, as well as cables connected to the treatment tools. These cables are connected to the operation unit 7.

[0030] 3, the imaging unit 20 is disposed inside the insertion hole 19c. The imaging unit 20 forms an optical image of the subject and converts the optical image into an image signal. The imaging unit 20 includes a lens barrel 21, an objective optical system 23, a holding member 25, an imaging element 31, and a positioning member 36.

[0031] The lens barrel 21 is tubular and extends in the optical axis direction with the optical axis J as its center. In this embodiment, the lens barrel 21 is substantially cylindrical and centered on the optical axis J. The lens barrel 21 may have other shapes, such as a rectangular tube shape centered on the optical axis J. The lens barrel 21 is open on both the object side (+Z side) and the base end side (-Z side). The lens barrel 21 has a first lens barrel portion 21a, a second tube portion 21b, a first tube portion 21c, a second lens barrel portion 21e, and a second positioning portion 21g. That is, one of the lens barrel 21 and the positioning member 36 has the second positioning portion 21g.

[0032] The first barrel portion 21a has a generally cylindrical shape and extends in the optical axis direction with the optical axis J as its center. The first barrel portion 21a is disposed closer to the base end (-Z side) than the distal end protrusion 19g of the distal end member 19. The first barrel portion 21a makes radial contact with the inner circumferential surface of the insertion hole 19c of the distal end member 19. This determines the radial position of the barrel 21 relative to the distal end member 19, and also determines the radial position of the imaging unit 20 relative to the distal end member 19. In this embodiment, the first barrel portion 21a is adhesively fixed to the inner circumferential surface of the insertion hole 19c. This fixes the barrel 21 to the distal end member 19.

[0033] The second tube portion 21b protrudes from the first lens barrel portion 21a toward the base end (-Z side). The second tube portion 21b is tubular and extends in the optical axis direction with the optical axis J as its center. In this embodiment, the second tube portion 21b is substantially cylindrical and centered on the optical axis J. The second tube portion 21b may have other shapes, such as a rectangular tube, centered on the optical axis J. The outer diameter of the second tube portion 21b is smaller than the outer diameter of the first lens barrel portion 21a. The second tube portion 21b faces the inner circumferential surface of the insertion hole 19c with a radial gap between them. The base end of the second tube portion 21b is located closer to the base end than the object side (+Z side) end of the positioning hole 19e. As a result, a circumferential portion of the base end portion of the second tube portion 21b faces the inner surface of the positioning hole 19e in the radial direction.

[0034] The first tube portion 21c protrudes from the second tube portion 21b toward the base end (-Z side). The first tube portion 21c is tubular and extends in the optical axis direction with the optical axis J as its center. In this embodiment, the first tube portion 21c is substantially cylindrical and centered on the optical axis J. The first tube portion 21c may have another shape, such as a rectangular tube, centered on the optical axis J. The outer diameter of the first tube portion 21c is smaller than the outer diameter of the second tube portion 21b. The first tube portion 21c faces the inner circumferential surface of the insertion hole 19c with a gap in the radial direction. The base end of the first tube portion 21c is located closer to the object side (+Z side) than the base end of the tip member 19. A circumferential portion of the first tube portion 21c faces the inner surface of the positioning hole 19e in the radial direction.

[0035] The second lens barrel portion 21e protrudes from the first lens barrel portion 21a toward the object side (+Z side). The second lens barrel portion 21e is substantially cylindrical and extends in the optical axis direction with the optical axis J as its center. The object side end of the second lens barrel portion 21e is located outside the insertion hole 19c. The outer diameter of the second lens barrel portion 21e is smaller than the outer diameter of the first lens barrel portion 21a. The base end side (-Z side) portion of the outer peripheral surface of the second lens barrel portion 21e radially contacts the inner peripheral surface of the tip protrusion portion 19g of the tip member 19. This determines the radial position of the lens barrel 21 relative to the tip member 19, and therefore the radial position of the imaging unit 20 relative to the tip member 19.

[0036] The second positioning portion 21g is a portion of the surface of the first barrel portion 21a facing the object side (+Z side) that is radially outward of the second barrel portion 21e. In other words, the second positioning portion 21g is a surface facing the object side. When viewed from the optical axis direction, the second positioning portion 21g has a substantially annular shape centered on the optical axis J. The second positioning portion 21g faces the abutment surface 19h of the tip member 19 in the optical axis direction. In this embodiment, the second positioning portion 21g contacts the abutment surface 19h in the optical axis direction. This allows the second positioning portion 21g to determine the position of the barrel 21 in the optical axis direction relative to the tip member 19. The second positioning portion 21g determines the position of the imaging unit 20 in the optical axis direction relative to the tip member 19.

[0037] The objective optical system 23 forms an optical image of the subject. The objective optical system 23 is composed of lenses 23a. In this embodiment, the objective optical system 23 is composed of a plurality of lenses 23a arranged side by side along the optical axis direction. Each of the plurality of lenses 23a is held on the inner circumferential surface of the lens barrel 21. Of the plurality of lenses 23a, lens 23c, which is arranged closest to the object (+Z side), is held on the inner circumferential surface of the second lens barrel section 21e. The surface of lens 23c facing the object side is exposed from the lens barrel 21 to the object side. In this embodiment, the objective optical system 23 is composed of five lenses 23a. The number of lenses 23a constituting the objective optical system 23 may be four or less, or six or more. Furthermore, the shape, etc. of each lens 23a is not limited to this embodiment.

[0038] The holding member 25 is attached to the lens barrel 21 and holds the image sensor 31. The holding member 25 is cylindrical and extends in the optical axis direction with the optical axis J as its center. The holding member 25 is open on both the object side (+Z side) and the base end side (-Z side). The holding member 25 has a cylindrical portion 26 and an image sensor holding portion 27.

[0039] The cylindrical portion 26 is the object-side (+Z side) portion of the holding member 25. The cylindrical portion 26 is cylindrical and extends in the optical axis direction with the optical axis J as its center. In this embodiment, the cylindrical portion 26 is substantially cylindrical and is centered on the optical axis J. The cylindrical portion 26 is disposed inside the insertion hole 19c. The cylindrical portion 26 is disposed closer to the base end (-Z side) than the second cylindrical portion 21b of the lens barrel 21. The outer diameter of the cylindrical portion 26 is smaller than the inner diameter of the insertion hole 19c of the tip member 19. The cylindrical portion 26 faces the inner circumferential surface of the insertion hole 19c with a radial gap between them. The inner diameter of the cylindrical portion 26 is larger than the outer diameter of the first cylindrical portion 21c. In this embodiment, the inner diameter of the cylindrical portion 26 is slightly larger than the outer diameter of the first cylindrical portion 21c. The cylindrical portion 26 surrounds the first cylindrical portion 21c from the radial outside. The inner peripheral surface of the cylindrical portion 26 is fixed to the outer peripheral surface of the first cylindrical portion 21c by adhesive G (not shown). In this way, the holding member 25 is attached to the lens barrel 21. The cylindrical portion 26 is provided with a fourth positioning portion 26a. In other words, the holding member 25 has the fourth positioning portion 26a.

[0040] 4, the fourth positioning portion 26a is a recess recessed from the surface facing the object side (+Z side) of the cylindrical portion 26 toward the base end side (-Z side). In this embodiment, the fourth positioning portion 26a is open radially outward. When viewed radially, the fourth positioning portion 26a has a substantially rectangular shape extending in the optical axis direction.

[0041] The imaging holding portion 27 is the portion on the base end side (-Z side) of the holding member 25. The imaging holding portion 27 is a square tube shape that extends in the optical axis direction with the optical axis J as its center. When viewed in the optical axis direction, the outer edge of the imaging holding portion 27 is rectangular. As shown in FIG. 3, the imaging holding portion 27 is positioned closer to the base end than the tubular portion 26. The imaging holding portion 27 is connected to the tubular portion 26 in the optical axis direction. The end on the base end side of the imaging holding portion 27 is located outside the insertion hole 19c.

[0042] The imaging element 31 receives the optical image of the subject formed by the objective optical system 23 and converts it into an image signal. The imaging element 31 is, for example, an image sensor such as a CCD or CMOS. The imaging element 31 is disposed closer to the proximal end (-Z side) than the objective optical system 23. The light receiving surface of the imaging element 31 faces the object side (+Z side). The light receiving surface of the imaging element 31 faces the lens 24 held on the inner peripheral surface of the imaging holding unit 27 in the optical axis direction. The imaging element 31 is fixed to the surface of the imaging holding unit 27 facing the proximal end. This allows the holding member 25 to hold the imaging element 31. As shown in FIG. 4, the imaging element 31 is substantially rectangular. When viewed from the optical axis direction, the outer edge of the imaging element 31 is rectangular. As shown in FIG. 2, an imaging board 32 is connected to the imaging element 31.

[0043] The imaging board 32 is, for example, a flexible printed circuit board (FPC board). Electronic components mounted on the imaging board 32 include, for example, a digital IC that generates a drive signal for the imaging element 31 and a capacitor that stabilizes the drive power supply for the digital IC. The imaging board 32 is disposed closer to the base end (-Z side) than the imaging element 31. A signal cable 34 is connected to the imaging board 32. This connects the imaging board 32 and the processor 3 (see FIG. 1) so that they can communicate with each other.

[0044] The signal cable 34 connects the imaging board 32 and the processor 3 so that they can communicate with each other. The proximal end of the signal cable 34 is connected to the processor 3 shown in FIG. 1. The signal cable 34 is passed through the interior of the universal cable 8 and the interior of the flexible tube portion 6c. As shown in FIG. 2, the signal cable 34 extends in the optical axis direction. In this embodiment, the signal cable 34 is a cable bundle formed by bundling multiple cables 34a. The object side (+Z side) end of each cable 34a is joined to the imaging board 32 by, for example, soldering. In this way, the signal cable 34 is joined to the imaging board 32.

[0045] As shown in Fig. 4, the positioning member 36 has a substantially circular ring shape centered on the optical axis J. As shown in Figs. 3 and 4, the positioning member 36 surrounds the second cylindrical portion 21b of the lens barrel 21 from the radially outer side. As shown in Fig. 4, the positioning member 36 has a main body portion 37, a first positioning portion 38, and a third positioning portion 39.

[0046] The main body 37 has a substantially annular shape centered on the optical axis J. As shown in FIGS. 3 and 4 , the main body 37 surrounds the second cylindrical portion 21b of the lens barrel 21 from the radially outer side. The main body 37 extends circumferentially along the outer peripheral surface of the second cylindrical portion 21b. As a result, the positioning member 36 extends circumferentially along the outer peripheral surface of the lens barrel 21. The inner diameter of the main body 37 is larger than the outer diameter of the second cylindrical portion 21b. As a result, the inner diameter of the positioning member 36 is larger than the outer diameter of the second cylindrical portion 21b. In this embodiment, the inner diameter of the positioning member 36 is slightly larger than the outer diameter of the second cylindrical portion 21b. The inner peripheral surface of the main body 37 is fixed to the outer peripheral surface of the second cylindrical portion 21b with adhesive G (not shown). In other words, the inner peripheral surface of the positioning member 36 is fixed to the outer peripheral surface of the second cylindrical portion 21b with adhesive G (not shown). The positioning member 36 is fixed to the outer peripheral surface of the lens barrel 21. In this way, the positioning member 36 is attached to the lens barrel 21. Alternatively, the inner diameter of the positioning member 36 may be set to be substantially the same as the outer diameter of the second cylindrical portion 21b, and the positioning member 36 may be attached to the lens barrel 21 by fitting.

[0047] As shown in FIG. 4 , the first positioning portion 38 is a protrusion that protrudes radially outward from the main body portion 37. The first positioning portion 38 is generally rectangular. When viewed in the optical axis direction, the first positioning portion 38 is generally rectangular. As shown in FIG. 3 , the first positioning portion 38 is positioned inside the positioning hole 19e of the tip member 19. Although not shown, the surface of the first positioning portion 38 facing one circumferential side (+θ side) and the surface facing the other circumferential side (−θ side) each face the inner surface of the positioning hole 19e in the circumferential direction. The first positioning portion 38 is clearance-fitted into the positioning hole 19e. This uniquely determines the circumferential position of the positioning member 36 relative to the tip member 19. As described above, the positioning member 36 and the holding member 25 are each fixed to the lens barrel 21. As a result, the first positioning portion 38 accurately determines the circumferential position of the holding member 25 relative to the tip member 19 via the lens barrel 21. That is, the positioning member 36 accurately determines the circumferential position of the holding member 25 relative to the tip member 19. Furthermore, as described above, the image pickup element 31 is held by the holding member 25. Therefore, the first positioning unit 38 determines the circumferential position of the image pickup element 31 relative to the tip member 19. That is, the positioning member 36 determines the circumferential position of the image pickup element 31 relative to the tip member 19. As a result, in this embodiment, it is possible to suppress so-called image tilt, which is a deviation in the circumferential orientation of an image formed by the endoscope 2, and therefore the quality of the image formed by the endoscope 2 can be improved.

[0048] As shown in FIG. 4 , the third positioning portion 39 has a protrusion shape that protrudes from the main body portion 37 toward the proximal end (−Z side). The third positioning portion 39 has a substantially rectangular parallelepiped shape. When viewed radially, the third positioning portion 39 has a substantially rectangular shape extending in the optical axis direction. The third positioning portion 39 is inserted into the fourth positioning portion 26 a of the holding member 25. In the present embodiment, the third positioning portion 39 is engaged with the fourth positioning portion 26 a. This uniquely determines the circumferential position of the holding member 25 relative to the positioning member 36. As described above, the first positioning portion 38 uniquely determines the circumferential position of the positioning member 36 relative to the distal end member 19. Therefore, the first positioning portion 38 and the third positioning portion 39 uniquely determine the circumferential position of the holding member 25 relative to the distal end member 19. As a result, in the present embodiment, image collapse can be more effectively suppressed, thereby more effectively improving the quality of images formed by the endoscope 2.

[0049] Fig. 5 is a flowchart showing a method for assembling the imaging unit 20 of this embodiment. Fig. 6 is a perspective view showing a first attachment step P02 of the method for assembling the imaging unit 20 of this embodiment. Fig. 7 is a perspective view showing a second attachment step P04 of the method for assembling the imaging unit 20 of this embodiment. Fig. 8 is a perspective view showing an adjustment step P05 of the method for assembling the imaging unit 20 of this embodiment.

[0050] Next, a method for assembling the imaging unit 20 of this embodiment will be described. The method for assembling the imaging unit 20 of this embodiment includes a fixing step Pf in which the holding member 25 is fixed to the lens barrel 21. The method for assembling the imaging unit 20 may include steps other than the fixing step Pf. The fixing step Pf includes an application step P01 in which adhesive G is applied to the outer peripheral surface of the lens barrel 21, a first attachment step P02 in which the positioning member 36 is attached to the outer peripheral surface of the lens barrel 21 via the adhesive G, an imaging element fixing step P03 in which the imaging element 31 is fixed to the holding member 25, a second attachment step P04 in which the holding member 25 is attached to the lens barrel 21 via the adhesive G while engaging the third positioning portion 39 with the fourth positioning portion 26a, an adjustment step P05 in which the position of the objective optical system 23 in the optical axis direction and the circumferential direction relative to the imaging element 31 is adjusted, and a curing step P06 in which the adhesive G is cured. In the following description, the term "worker" includes the worker performing each step and the assembly device. 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.

[0051] In the application step P01, the worker applies adhesive G to the outer peripheral surface of the lens barrel 21. As shown in FIG. 6 , the worker applies adhesive G to the outer peripheral surfaces of the second tube portion 21b and the first tube portion 21c of the lens barrel 21. In this embodiment, the worker applies adhesive G to the entire circumferential direction of each of the outer peripheral surfaces of the second tube portion 21b and the first tube portion 21c. The worker may apply adhesive G to only a portion of the circumferential direction of the outer peripheral surface of the second tube portion 21b, or may apply adhesive G to only a portion of the circumferential direction of the outer peripheral surface of the first tube portion 21c. Once the worker applies adhesive G to the outer peripheral surface of the lens barrel 21, the application step P01 is completed. Note that in the fixing step Pf of this embodiment, the objective optical system 23 is attached to the lens barrel 21 in a step prior to the application step P01. The objective optical system 23 may also be attached to the lens barrel 21 in a step subsequent to the application step P01.

[0052] In this embodiment, the adhesive G may be a thermosetting adhesive such as an epoxy resin adhesive, a melamine resin adhesive, a phenol resin adhesive, or a mixture of these adhesives. In this embodiment, the adhesive G is an epoxy resin adhesive.

[0053] In the first attachment step P02, the worker attaches the positioning member 36 to the outer peripheral surface of the lens barrel 21 using adhesive G. The worker moves the positioning member 36 from the base end (-Z side) of the lens barrel 21 toward the object side (+Z side) to pass the lens barrel 21 through the main body 37. As shown in FIG. 7 , the worker attaches the positioning member 36 to the outer peripheral surface of the second tube portion 21b. At this time, the positioning member 36 is attached to the outer peripheral surface of the lens barrel 21 using uncured adhesive G. Also, as described above, the inner diameter of the positioning member 36 is larger than the outer diameter of the second tube portion 21b. Therefore, at this time, the worker can rotate the positioning member 36 around the optical axis J relative to the lens barrel 21. Once the worker attaches the positioning member 36 to the outer peripheral surface of the lens barrel 21 using adhesive G, the first attachment step P02 is complete.

[0054] In the imaging element fixing process P03, the worker fixes the imaging element 31 to the holding member 25. More specifically, the worker fixes the imaging element 31 to the surface facing the base end (-Z side) of the imaging holding unit 27 using an adhesive (not shown). The worker fixes the imaging element 31 to the surface facing the base end of the imaging holding unit 27 so that, when viewed from the base end, each of the four sides constituting the outer edge of the imaging element 31 is parallel to different sides constituting the outer edge of the imaging holding unit 27. This makes it possible to accurately determine the circumferential position of the imaging element 31 relative to the holding member 25. Once the worker fixes the imaging element 31 to the holding member 25, the imaging element fixing process P03 is completed.

[0055] In the second attachment step P04, the worker attaches the holding member 25 to the lens barrel 21 using adhesive G while engaging the third positioning portion 39 with the fourth positioning portion 26a. The worker inserts the first cylindrical portion 21c of the lens barrel 21 into the cylindrical portion 26 by moving the holding member 25 from the base end side (-Z side) of the lens barrel 21 toward the object side (+Z side). As shown in FIG. 8 , the worker inserts the first cylindrical portion 21c into the cylindrical portion 26 while adjusting the circumferential position of the holding member 25 relative to the positioning member 36 so that the third positioning portion 39 of the positioning member 36 engages with the fourth positioning portion 26a of the holding member 25. Once the first cylindrical portion 21c is inserted into the cylindrical portion 26, the holding member 25 is attached to the lens barrel 21 using uncured adhesive G. As described above, the inner diameter of the cylindrical portion 26 is larger than the outer diameter of the first cylindrical portion 21c. Therefore, at this time, the worker or the like can rotate the lens barrel 21 around the optical axis J relative to the holding member 25. The worker or the like can also move the holding member 25 in the optical axis direction relative to the lens barrel 21. The worker or the like attaches the holding member 25 to the lens barrel 21 via adhesive G while engaging the third positioning portion 39 with the fourth positioning portion 26a, and the second attachment process P04 is completed.

[0056] In adjustment step P05, the worker or the like adjusts the optical axis direction position and circumferential direction position of the objective optical system 23 relative to the image sensor 31. The worker or the like first adjusts the optical axis direction position of the holding member 25 relative to the lens barrel 21, thereby adjusting the optical axis direction position of the objective optical system 23 relative to the image sensor 31. At this time, the worker or the like adjusts the optical axis direction position of the objective optical system 23 relative to the image sensor 31 so that the image generated from the image signal converted by the image sensor 31 is in focus. Next, the worker or the like rotates the lens barrel 21 about the optical axis J relative to the holding member 25, thereby adjusting the circumferential direction position of the objective optical system 23 relative to the image sensor 31. This allows the worker or the like to adjust the deflection angle of the objective optical system 23 relative to the image sensor 31. Once the worker or the like has adjusted the optical axis direction position and circumferential direction position of the objective optical system 23 relative to the image sensor 31, adjustment step P05 is completed.

[0057] In the curing step P06, the worker or the like cures the adhesive G. The worker or the like heats the lens barrel 21, to which the holding member 25 and the positioning member 36 are attached, in a heating furnace (not shown), thereby heating and curing the adhesive G. As a result, the holding member 25 and the positioning member 36 are fixed to the lens barrel 21. The worker or the like cures the adhesive G and fixes the holding member 25 and the positioning member 36 to the lens barrel 21, and the curing step P06 is completed. When the curing step P06 is completed, the fixing step Pf, in which the holding member 25 is fixed to the lens barrel 21, is completed.

[0058] The order of the steps in the fixing step Pf is not limited to that of this embodiment, and for example, the imaging element fixing step P03 may be performed before the application step P01 or the first attachment step P02.

[0059] After the fixing step Pf is completed, the worker inserts the imaging unit 20 into the insertion hole 19c of the distal end member 19 in the assembly process of the endoscope 2, as shown in FIG. 4 . At this time, the worker inserts the first positioning portion 38 into the positioning hole 19e. As shown in FIG. 3 , when the second positioning portion 21g of the lens barrel 21 contacts the abutment surface 19h of the distal end member 19 in the optical axis direction, the worker stops inserting the imaging unit 20 into the insertion hole 19c. Thereafter, the worker fixes the lens barrel 21 to the distal end member 19 by hardening an adhesive (not shown) that was previously applied to the outer peripheral surface of the first lens barrel portion 21a of the lens barrel 21. This holds the imaging unit 20 in the distal end member 19.

[0060] As described above, second positioning portion 21g comes into contact with abutment surface 19h in the optical axis direction, thereby enabling accurate determination of the position of imaging unit 20 in the optical axis direction relative to tip member 19. This makes it possible to reduce variation in the amount of protrusion of second barrel portion 21e of barrel 21 toward the object side from tip member 19. Therefore, the air and water supply unit 71 shown in FIG. 2 can improve the cleanability when cleaning lens 23c, which is positioned closest to the object side.

[0061] 3, the first positioning portion 38 is disposed inside the positioning hole 19e, and therefore, as described above, the circumferential position of the positioning member 36 relative to the tip end member 19 can be uniquely determined. Also, as described above, the third positioning portion 39 can uniquely determine the circumferential position of the holding member 25 relative to the positioning member 36. These make it possible to uniquely determine the circumferential position of the holding member 25 relative to the tip end member 19, as described above.

[0062] According to this embodiment, the imaging unit 20 is held by the distal end member 19 of the endoscope 2 and includes: a cylindrical lens barrel 21 extending in the optical axis direction; an objective optical system 23 constituted by a lens 23a held on the inner circumferential surface of the lens barrel 21; a holding member 25 attached to the lens barrel 21 and holding an imaging element 31; and a positioning member 36 attached to the lens barrel 21. The positioning member 36 has a first positioning portion 38 that determines the circumferential position of the holding member 25 relative to the distal end member 19, and the lens barrel 21 has a second positioning portion 21g that determines the optical axis position of the lens barrel 21 relative to the distal end member 19. Therefore, as described above, the second positioning portion 21g can reduce variation in the amount of protrusion of the second lens barrel portion 21e of the lens barrel 21 from the distal end member 19 toward the object side (+Z side). Therefore, the air and water supply unit 71 can improve the cleanability of the lens 23c located closest to the object side.

[0063] Furthermore, as described above, the first positioning portion 38 accurately determines the circumferential position of the holding member 25 relative to the distal end member 19, and therefore the circumferential position of the image pickup element 31 can be accurately determined relative to the distal end member 19. Therefore, image tilt, which is a deviation in the circumferential direction of the image formed by the endoscope 2, can be suppressed, and the quality of the image formed by the endoscope 2 can be improved.

[0064] Furthermore, in this embodiment, as described above, the position of the holding member 25 in the optical axis direction relative to the distal end member 19 is determined by the second positioning portion 21g of the lens barrel 21. Furthermore, the circumferential position of the holding member 25 relative to the distal end member 19 is determined with high precision by the first positioning portion 38 of the positioning member 36. Therefore, even if the dimensional tolerances of the lens barrel 21 and the holding member 25 are both large, stress is not applied directly to the holding member 25 from the distal end member 19. This makes it possible to accurately determine the circumferential position of the holding member 25 relative to the distal end member 19 while preventing excessive stress from being applied to the holding member 25. This makes it possible to effectively prevent fluctuations in the relative positions of the objective optical system 23 and the image sensor 31, and in the circumferential position of the image sensor 31 relative to the distal end member 19, and therefore effectively prevent degradation in the quality of images formed by the endoscope 2.

[0065] According to this embodiment, the positioning member 36 has a third positioning portion 39 that protrudes toward the base end (-Z side), the holding member 25 has a fourth positioning portion 26a that is recessed toward the base end, and the third positioning portion 39 is engaged with the fourth positioning portion 26a. Therefore, the third positioning portion 39 and the fourth positioning portion 26a can uniquely determine the circumferential position of the holding member 25 relative to the positioning member 36. This makes it possible to more accurately determine the circumferential position of the image sensor 31 relative to the tip member 19. This makes it possible to more effectively suppress image collapse, thereby more effectively improving the quality of images formed by the endoscope 2.

[0066] Furthermore, in this embodiment, in the second attachment step P04, the circumferential position of the holding member 25 relative to the positioning member 36 can be uniquely determined by the simple task of attaching the holding member 25 to the lens barrel 21 while engaging the third positioning portion 39 with the fourth positioning portion 26a. Therefore, in the second attachment step P04, the task of adjusting the circumferential positions of the holding member 25 and the image sensor 31 relative to the positioning member 36 is not required, and an increase in the number of steps in the second attachment step P04 can be suppressed. Therefore, an increase in the number of steps for assembling the image pickup unit 20 can be suppressed.

[0067] According to this embodiment, positioning member 36 extends circumferentially along the outer peripheral surface of lens barrel 21 and is fixed to the outer peripheral surface of lens barrel 21. Therefore, in first attachment step P02, positioning member 36 can be attached to lens barrel 21 by the simple task of moving positioning member 36 toward the object side (+Z side) and passing lens barrel 21 through positioning member 36. Therefore, an increase in the number of steps in first attachment step P02 can be suppressed, and an increase in the number of steps for assembling imaging unit 20 can be more preferably suppressed.

[0068] According to this embodiment, the holding member 25 has a cylindrical tubular portion 26 that extends in the optical axis direction around the optical axis J, and the lens barrel 21 has a cylindrical first tubular portion 21c that extends in the optical axis direction around the optical axis J. The inner diameter of the tubular portion 26 is larger than the outer diameter of the first tubular portion 21c, and the inner circumferential surface of the tubular portion 26 is fixed to the outer circumferential surface of the first tubular portion 21c with adhesive G. Therefore, as described above, in the adjustment step P05, the lens barrel 21 can be rotated around the optical axis J relative to the holding member 25 and moved in the optical axis direction. This allows the circumferential position of the objective optical system 23 relative to the image sensor 31 to be adjusted in the adjustment step P05, thereby adjusting the deflection angle of the objective optical system 23 relative to the image sensor 31. Furthermore, the optical axial position of the objective optical system 23 relative to the image sensor 31 can be adjusted, thereby adjusting the focus of the image formed by the imaging unit 20. These features make it possible to more suitably improve the quality of images formed by the endoscope 2.

[0069] According to this embodiment, the lens barrel 21 has a cylindrical second tube portion 21b that extends in the optical axis direction with the optical axis J as its center. The inner diameter of the positioning member 36 is larger than the outer diameter of the second tube portion 21b, and the inner circumferential surface of the positioning member 36 is fixed to the outer circumferential surface of the second tube portion 21b with adhesive G. Therefore, in the adjustment step P05, the lens barrel 21 can be rotated around the optical axis J relative to the positioning member 36. Therefore, in the adjustment step P05, the lens barrel 21 can be rotated around the optical axis J relative to the holding member 25 while the third positioning portion 39 is engaged with the fourth positioning portion 26a. This allows the circumferential position of the objective optical system 23 relative to the image sensor 31 to be adjusted in the adjustment step P05, and therefore the deflection angle of the objective optical system 23 relative to the image sensor 31 to be adjusted. This makes it possible to more suitably improve the quality of images formed by the endoscope 2.

[0070] According to this embodiment, the holding member 25 has a rectangular cylindrical imaging holding portion 27 that extends in the optical axis direction with the optical axis J as its center, the imaging element 31 is fixed to a surface of the imaging holding portion 27 that faces the base end side (-Z side), and the outer edges of the imaging element 31 and the imaging holding portion 27 are each rectangular when viewed in the optical axis direction. Therefore, in the imaging element fixing step P03, as described above, the imaging element 31 is fixed to the surface facing the base end side of the imaging holding portion 27 so that, when viewed from the base end side, each of the four sides that form the outer edge of the imaging element 31 is parallel to different sides that form the outer edge of the imaging holding portion 27, thereby making it possible to accurately determine the circumferential position of the imaging element 31 relative to the holding member 25. Therefore, since the circumferential position of the imaging element 31 relative to the distal end member 19 can be determined more accurately, image tilt can be more effectively suppressed.

[0071] According to the present embodiment, the endoscope 2 includes an imaging unit 20 and a distal end member 19 that holds the imaging unit 20. The distal end member 19 is provided with an insertion hole 19c that penetrates in the optical axis direction centered on the optical axis J, and the imaging unit 20 is disposed inside the insertion hole 19c. As described above, the imaging unit 20 of the present embodiment can prevent excessive stress from being applied to the holding member 25 even when the dimensional tolerances of the lens barrel 21 and the holding member 25 are both large. Therefore, the circumferential position of the holding member 25 with respect to the distal end member 19 can be accurately determined while preventing excessive stress from being applied to the holding member 25. As a result, fluctuations in the relative positions of the objective optical system 23 and the imaging element 31, and in the circumferential position of the imaging element 31 with respect to the distal end member 19, can be preferably prevented, and deterioration in the quality of images formed by the endoscope 2 can be preferably prevented.

[0072] According to this embodiment, the inner circumferential surface of the insertion hole 19c is provided with a positioning hole 19e that is recessed radially outward and extends in the optical axis direction. The positioning hole 19e is open toward the proximal end (-Z side). The first positioning portion 38 is a protrusion that protrudes radially outward and is located inside the positioning hole 19e. Therefore, as described above, the first positioning portion 38 and the positioning hole 19e can uniquely determine the circumferential position of the positioning member 36 relative to the distal end member 19. Furthermore, as described above, the third positioning portion 39 and the fourth positioning portion 26a can uniquely determine the circumferential position of the holding member 25 relative to the positioning member 36. As a result, the circumferential position of the holding member 25 relative to the distal end member 19 can be uniquely determined, and therefore the circumferential position of the image sensor 31 relative to the distal end member 19 can be determined with greater accuracy. Therefore, image collapse can be more effectively suppressed, and degradation in the quality of images formed by the endoscope 2 can be more effectively suppressed.

[0073] Furthermore, in this embodiment, as described above, in the assembly process of the endoscope 2, the imaging unit 20 can be attached to the distal end member 19 by the simple operation of inserting the first positioning portion 38 into the positioning hole 19e and inserting the imaging unit 20 into the insertion hole 19c. Therefore, an increase in the number of steps in assembling the endoscope 2 can be suppressed.

[0074] Furthermore, in the process of assembling the endoscope 2, the circumferential position of the holding member 25 relative to the tip member 19 can be uniquely determined by the simple task of inserting the imaging unit 20 into the insertion hole 19c while inserting the first positioning portion 38 into the positioning hole 19e. This eliminates the need for the task of adjusting the circumferential position of the imaging element 31 relative to the tip member 19 in the process of assembling the endoscope 2, thereby more preferably preventing an increase in the number of steps required to assemble the endoscope 2.

[0075] According to this embodiment, the assembly method for the imaging unit 20 includes a fixing step Pf of fixing the holding member 25 to the lens barrel 21, and the fixing step Pf includes an application step P01 of applying adhesive G to the outer peripheral surface of the lens barrel 21, a first attachment step P02 of attaching the positioning member 36 to the outer peripheral surface of the lens barrel 21 via the adhesive G, a second attachment step P04 of attaching the holding member 25 to the lens barrel 21 via the adhesive G while engaging the third positioning portion 39 with the fourth positioning portion 26 a, an adjustment step P05 of adjusting the position in the optical axis direction and the position in the circumferential direction of the objective optical system 23 relative to the image sensor 31, and a curing step P06 of curing the adhesive G. As described above, with the imaging unit 20 of this embodiment, even if the dimensional tolerances of the lens barrel 21 and the holding member 25 are both large, excessive stress on the holding member 25 can be suppressed. Therefore, it is possible to accurately determine the circumferential position of the holding member 25 relative to the tip member 19, while preventing excessive stress from being applied to the holding member 25. Therefore, it is possible to preferably prevent fluctuations in the relative positions of the objective optical system 23 and the image sensor 31, and in the circumferential position of the image sensor 31 relative to the tip member 19, and therefore it is possible to preferably prevent deterioration in the quality of the image formed by the endoscope 2.

[0076] In this embodiment, as shown in FIG. 3 , the second positioning portion 21g is a portion of the surface of the first barrel portion 21a facing the object side (+Z side) that is radially outward of the second barrel portion 21e. However, the second positioning portion 36a may be a surface of the positioning member 36 facing the object side. That is, one of the barrel 21 and the positioning member 36 has the second positioning portion 36a. In this case, although not shown, the second positioning portion 36a contacts the abutment surface 19m, which is the surface facing the base end side (-Z side) of the base portion 19a, in the optical axis direction. This allows the position of the imaging unit 20 in the optical axis direction relative to the tip member 19 to be accurately determined. In this case, the positioning member 36 has the second positioning portion 36a that determines the position of the barrel 21 in the optical axis direction relative to the tip member 19. Furthermore, in this case, it is preferable that the second positioning portion 21g and the abutment surface 19h be spaced apart in the optical axis direction. As a result, the position of the lens barrel 21 in the optical axis direction relative to the tip member 19 can be determined with high precision by the second positioning portion 36a and the abutment surface 19m.

[0077] Second Embodiment Fig. 9 is a perspective view showing a portion of an imaging unit 220 of this embodiment. Fig. 10 is a perspective view showing a second attachment step P04 of the method for assembling the imaging unit 220 of this embodiment. In this embodiment, the imaging unit 220 includes a lens barrel 221, an objective optical system 23 (see Fig. 3), a holding member 25 (see Fig. 3), an imaging element 31 (see Fig. 3), and a positioning member 236. In the following description, components that are the same as those in the first embodiment described above are designated by the same reference numerals, and description thereof will be omitted.

[0078] The lens barrel 221 has a cylindrical shape that extends in the optical axis direction and is centered on the optical axis J. In this embodiment, the lens barrel 221 has a substantially cylindrical shape that is centered on the optical axis J. The lens barrel 221 has a first lens barrel portion 221 a, a first tube portion 21 c, a second lens barrel portion 21 e, and a second positioning portion 21 g.

[0079] The first lens barrel portion 221a has a substantially cylindrical shape that extends in the optical axis direction with the optical axis J as its center. Although not shown in the drawings, the first lens barrel portion 221a comes into radial contact with the inner circumferential surface of the insertion hole 19c of the tip member 19. This determines the radial position of the lens barrel 221 relative to the tip member 19, and also determines the radial position of the imaging unit 220 relative to the tip member 19. In this embodiment, the first lens barrel portion 221a is adhesively fixed to the inner circumferential surface of the insertion hole 19c. This fixes the lens barrel 221 to the tip member 19. In this embodiment, a groove 221h is provided in the first lens barrel portion 221a.

[0080] As shown in Fig. 10 , groove 221h is a groove that is recessed radially inward from the outer circumferential surface of first barrel portion 221a and extends circumferentially. In this embodiment, groove 221h extends around the entire circumferential circumference. As shown in Fig. 9 , a positioning member 236 is housed inside groove 221h. First inner surface 221j shown in Fig. 10 is the inner surface of groove 221h that faces radially outward. First inner surface 221j is part of the outer circumferential surface of barrel 221.

[0081] In this embodiment, the first cylindrical portion 21c protrudes from the first lens barrel portion 221a toward the base end (-Z side). Although not shown, the cylindrical portion 26 of the holding member 25 is fixed to the outer peripheral surface of the first cylindrical portion 21c with adhesive G, as in the first embodiment described above.

[0082] The second lens barrel portion 21e protrudes from the first lens barrel portion 221a toward the object side (+Z side). The second lens barrel portion 21e is substantially cylindrical and extends in the optical axis direction with the optical axis J as its center. Although not shown, as in the first embodiment described above, the second positioning portion 21g comes into contact with the abutment surface 19h of the tip member 19 in the optical axis direction. In this way, the second positioning portion 21g determines the position of the lens barrel 221 in the optical axis direction relative to the tip member 19. The second positioning portion 21g determines the position of the imaging unit 220 in the optical axis direction relative to the tip member 19. Other configurations of the lens barrel 221 of this embodiment are similar to those of the lens barrel 21 of the first embodiment described above.

[0083] 9 , the positioning member 236 has a substantially circular ring shape centered on the optical axis J. As described above, in this embodiment, the positioning member 236 is housed inside the groove portion 221h. The positioning member 236 surrounds the first inner surface 221j from the radially outer side. In other words, the positioning member 236 surrounds the outer peripheral surface of the lens barrel 221 from the radially outer side. The positioning member 236 has a main body portion 237 and a first positioning portion 38.

[0084] The main body portion 237 has a substantially circular ring shape centered on the optical axis J. The main body portion 237 surrounds the first inner surface 221j from the radially outer side. The main body portion 237 extends circumferentially along the first inner surface 221j. As a result, the positioning member 236 extends circumferentially along the outer peripheral surface of the lens barrel 221. The inner diameter of the main body portion 237 is slightly larger than the inner diameter of the groove portion 221h. In other words, the inner diameter of the positioning member 236 is slightly larger than the inner diameter of the groove portion 221h. The inner peripheral surface of the main body portion 237 is fixed to the first inner surface 221j by adhesive G (not shown). In other words, the inner peripheral surface of the positioning member 236 is fixed to the outer peripheral surface of the lens barrel 221 by adhesive G (not shown). As a result, the positioning member 236 is fixed to the lens barrel 221. As shown in FIG. 10 , the main body portion 237 is composed of multiple arc portions 237a and 237b. That is, the positioning member 236 has a plurality of arcuate portions 237a and 237b.

[0085] Each of the arc portions 237a, 237b has a substantially arc shape centered on the optical axis J. As shown in FIG. 9 , each of the arc portions 237a, 237b extends circumferentially along the first inner surface 221j, i.e., the outer peripheral surface of the lens barrel 221. In this embodiment, the central angle of each of the arc portions 237a, 237b is approximately 180°. The arc portions 237a, 237b are arranged side by side in the circumferential direction. Each of the multiple arc portions 237a, 237b is fixed to the first inner surface 221j, i.e., the outer peripheral surface of the lens barrel 221, with adhesive G (not shown). Furthermore, each of the multiple arc portions 237a, 237b is fixed to each other with adhesive G (not shown).

[0086] The first positioning portion 38 has a protrusion-like shape that protrudes radially outward from the arc portion 237a. Although not shown, similar to the first embodiment described above, the first positioning portion 38 is positioned inside the positioning hole 19e of the distal end member 19. The first positioning portion 38 is clearance-fitted into the positioning hole 19e. This uniquely determines the circumferential position of the positioning member 236 relative to the distal end member 19. As described above, the positioning member 236 and the holding member 25 are each fixed to the lens barrel 221. Therefore, similar to the first embodiment described above, the positioning member 236 can accurately determine the circumferential positions of the holding member 25 and the image sensor 31 relative to the distal end member 19. This can suppress image collapse, thereby improving the quality of images formed by the endoscope 202. Other configurations of the positioning member 236 of this embodiment are similar to those of the positioning member 36 of the first embodiment described above. Other configurations of the endoscope 202 of this embodiment are similar to those of the endoscope 2 of the first embodiment described above.

[0087] Next, we will describe the first attachment step P02 of the fixing step Pf of this embodiment, in which the positioning member 236 is attached to the outer peripheral surface of the lens barrel 221 via adhesive G. As shown in FIG. 10 , an operator moves each of the arc portions 237a, 237b from the radially outer side of the lens barrel 21 to the radially inner side, thereby inserting each of the arc portions 237a, 237b into the groove 221h and attaching them to the first inner surface 221j. At this time, each of the arc portions 237a, 237b is attached to the first inner surface 221j via the uncured adhesive G that was applied to the first inner surface 221j in the application step P01. As a result, the positioning member 236 is attached to the outer peripheral surface of the lens barrel 221 via the uncured adhesive G. As described above, the inner diameter of the positioning member 236 is slightly larger than the inner diameter of the groove 221h. Therefore, at this time, the worker or the like can rotate the positioning member 236 relative to the lens barrel 221 about the optical axis J. Therefore, similar to the first embodiment described above, in the adjustment step P05, the worker or the like can rotate the lens barrel 221 about the optical axis J relative to the holding member 25. Furthermore, the arc portions 237a, 237b are in contact with each other in the circumferential direction via adhesive G (not shown). When the worker or the like attaches the positioning member 236 to the outer peripheral surface of the lens barrel 221 via adhesive G, the first attachment step P02 is completed.

[0088] Thereafter, in a curing step P06, when the adhesive G hardens, the holding member 25 and the positioning member 236 are each fixed to the lens barrel 221. The arc portions 237a, 237b are also fixed to each other by the adhesive G to form the main body 37. The other steps in the method for assembling the imaging unit 220 of this embodiment are the same as the other steps in the method for assembling the imaging unit 20 of the first embodiment described above.

[0089] According to this embodiment, the positioning member 236 has a plurality of arc portions 237 a, 237 b that extend circumferentially along the outer peripheral surface of the lens barrel 221 and are arranged side by side in the circumferential direction, and each of the plurality of arc portions 237 a, 237 b is fixed to each other and to the outer peripheral surface of the lens barrel 221. Therefore, in the first attachment step P02, the positioning member 236 can be attached to the lens barrel 221 by the simple task of moving each of the arc portions 237 a, 237 b radially inward and inserting them into the grooves 221 h. Therefore, an increase in the number of steps in the first attachment step P02 can be suppressed, and an increase in the number of steps for assembling the imaging unit 220 can be suitably suppressed.

[0090] Furthermore, in this embodiment, as described above, the position of the holding member 25 in the optical axis direction relative to the distal end member 19 is determined by the second positioning portion 21g of the lens barrel 221, and the circumferential position of the holding member 25 relative to the distal end member 19 is accurately determined by the first positioning portion 38 of the positioning member 236. Therefore, even if the dimensional tolerances of the lens barrel 221 and the holding member 25 are large, stress is not applied directly to the holding member 25 from the distal end member 19. This makes it possible to accurately determine the circumferential position of the holding member 25 relative to the distal end member 19 while preventing excessive stress from being applied to the holding member 25. Therefore, fluctuations in the relative positions of the objective optical system 23 and the image sensor 31, and in the circumferential position of the image sensor 31 relative to the distal end member 19, can be effectively prevented, thereby effectively preventing a deterioration in the quality of images formed by the endoscope 202.

[0091] In this embodiment, the arc portions 237a, 237b are fixed to each other, but they do not have to be fixed to each other. The number of arc portions included in the positioning member 236 may be three or more. Furthermore, the first barrel portion 221a does not have to be provided with the groove portion 221h. In this case, the arc portions 237a, 237b are fixed to the outer peripheral surface of the first barrel portion 221a.

[0092] 11 is an exploded perspective view showing a portion of an imaging unit 320 of this embodiment. In this embodiment, an endoscope 302 includes a tip member 319 and an imaging unit 320. The imaging unit 320 includes a lens barrel 321, an objective optical system 23 (see FIG. 3), a holding member 25 (see FIG. 3), an imaging element 31 (see FIG. 3), and a positioning member 336. In the following description, components that are the same as those in the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted.

[0093] As shown in Figure 11, the tip member 319 has a generally circular ring shape extending in the optical axis direction. Although not shown, the tip member 319 is fixed to the inner circumferential surface of the tip case 18c. The tip member 319 has a base 319a, a tip protrusion 19g (see Figure 3), and an abutment surface 19h (see Figure 3). The tip member 319 is provided with an insertion hole 319c and a plurality of through-holes 19i.

[0094] The base 319a has a generally circular ring shape extending in the optical axis direction. The insertion hole 319c is a hole that penetrates the base 319a in the optical axis direction. Although not shown, the imaging unit 320 is disposed inside the insertion hole 319c. A positioning protrusion 319e is provided on the inner circumferential surface of the insertion hole 319c.

[0095] The positioning protrusion 319e is a protrusion that protrudes radially inward from the inner circumferential surface of the insertion hole 319c. When viewed from the optical axis direction, the positioning protrusion 319e is substantially rectangular. The positioning protrusion 319e extends in the optical axis direction. The base end side (-Z side) end of the positioning protrusion 319e is located at the base end side end of the base 319a. Although not shown in the figures, the object side (+Z side) end of the positioning protrusion 319e is located near the center of the base 319a in the optical axis direction. Other configurations of the tip member 319 of this embodiment are similar to those of the tip member 319 of the first embodiment described above.

[0096] The lens barrel 321 has a cylindrical shape that extends in the optical axis direction and is centered on the optical axis J. In this embodiment, the lens barrel 321 has a substantially cylindrical shape that is centered on the optical axis J. The lens barrel 321 has a first lens barrel portion 321a, a first tube portion 21c, a second lens barrel portion 21e, and a second positioning portion 21g.

[0097] The first barrel portion 321a has a generally cylindrical shape that extends in the optical axis direction with the optical axis J as its center. In this embodiment, the first barrel portion 21c protrudes from the first barrel portion 321a toward the base end side (-Z side). Although not shown, as in the first embodiment described above, the cylindrical portion 26 of the holding member 25 is fixed to the outer peripheral surface of the first barrel portion 21c with adhesive G.

[0098] The second lens barrel portion 21e protrudes from the first lens barrel portion 321a toward the object side (+Z side). The second lens barrel portion 21e is substantially cylindrical and extends in the optical axis direction with the optical axis J as its center. Although not shown, as in the first embodiment described above, the second positioning portion 21g comes into contact with the abutment surface 19h of the tip member 319 in the optical axis direction. In this way, the second positioning portion 21g determines the position of the lens barrel 321 in the optical axis direction relative to the tip member 319. The second positioning portion 21g determines the position of the imaging unit 320 in the optical axis direction relative to the tip member 319. Other configurations of the lens barrel 321 of this embodiment are similar to those of the lens barrel 21 of the first embodiment described above.

[0099] The positioning member 336 has a generally cylindrical shape centered on the optical axis J. The positioning member 336 surrounds the first barrel portion 321a from the outside in the radial direction. The positioning member 336 has a main body portion 337 and a first positioning portion 338.

[0100] The main body 337 has a substantially cylindrical shape centered on the optical axis J. The main body 337 surrounds the first barrel 321a from the radially outer side. The main body 337 extends circumferentially along the outer peripheral surface of the first barrel 321a. As a result, the positioning member 336 extends circumferentially along the outer peripheral surface of the barrel 321a. The inner diameter of the main body 337 is larger than the outer diameter of the first barrel 321a. In this embodiment, the inner diameter of the positioning member 336 is slightly larger than the outer diameter of the first barrel 321a. The inner peripheral surface of the main body 337 is fixed to the outer peripheral surface of the first barrel 321a with adhesive G (not shown). In other words, the inner peripheral surface of the positioning member 336 is fixed to the outer peripheral surface of the first barrel 321a with adhesive G (not shown). As a result, the positioning member 336 is fixed to the outer peripheral surface of the barrel 321. That is, the positioning member 336 is fixed to the lens barrel 321 .

[0101] The first positioning portion 338 is a groove recessed radially outward from the outer circumferential surface of the main body portion 337 and extending in the optical axis direction. When viewed in the optical axis direction, the first positioning portion 338 has a substantially rectangular shape. In this embodiment, the first positioning portion 338 penetrates the main body portion 337 in the radial direction. The first positioning portion 338 may be a groove having a bottom surface facing radially outward, rather than penetrating the main body portion 337 in the radial direction. The first positioning portion 338 is open on the object side (+Z side). Furthermore, the first positioning portion 338 is open on the base end side (-Z side). The first positioning portion 338 does not have to be open on the base end side.

[0102] Although not shown in the drawings, the positioning protrusion 319e is located inside the first positioning portion 338. Although not shown in the drawings, the surface of the positioning protrusion 319e facing one circumferential side (+θ side) and the surface facing the other circumferential side (−θ side) each face the inner surface of the first positioning portion 338 in the circumferential direction. The positioning protrusion 319e is clearance-fitted into the first positioning portion 338. This uniquely determines the circumferential position of the positioning member 336 relative to the tip member 319. Other configurations of the positioning member 336 of this embodiment are similar to those of the positioning member 36 of the first embodiment described above. Other configurations of the endoscope 302 of this embodiment are similar to those of the endoscope 2 of the first embodiment described above.

[0103] The fixing step Pf included in the assembly method of the imaging unit 320 of this embodiment is the same as the fixing step Pf of the first embodiment described above. After completing the fixing step Pf, the worker inserts the imaging unit 320 into the insertion hole 319c of the tip member 319 in the assembly process of the endoscope 302, as shown in FIG. 11 . At this time, the worker inserts the positioning protrusion 319e into the first positioning portion 338. Although not shown, similar to the first embodiment described above, when the second positioning portion 21g of the lens barrel 321 contacts the abutment surface 19h of the tip member 319 in the optical axis direction, the worker stops inserting the imaging unit 320 into the insertion hole 319c. Thereafter, the worker fixes the lens barrel 321 to the tip member 319 by curing an adhesive (not shown) that was previously applied to the outer peripheral surface of the first lens barrel portion 321a of the lens barrel 321. This holds the imaging unit 320 in the tip member 319.

[0104] According to this embodiment, a positioning protrusion 319e protruding radially inward is provided on the inner circumferential surface of the insertion hole 319c, and the first positioning portion 338 is a groove recessed radially inward, extending in the optical axis direction, and opening toward the object side (+Z side). The positioning protrusion 319e is located inside the first positioning portion 338. Therefore, the first positioning portion 338 and the positioning protrusion 319e can uniquely determine the circumferential position of the positioning member 336 relative to the tip member 319. Furthermore, as described above, the positioning member 336 and the holding member 25 are each fixed to the lens barrel 321. Therefore, similar to the first embodiment described above, the positioning member 336 can accurately determine the circumferential positions of the holding member 25 and the image sensor 31 relative to the tip member 319. This can suppress image collapse, thereby improving the quality of images formed by the endoscope 302.

[0105] Furthermore, in this embodiment, as described above, in the assembly process of the endoscope 302, the imaging unit 320 can be attached to the tip member 319 by the simple operation of inserting the imaging unit 320 into the insertion hole 319c while inserting the positioning convex portion 319e into the inside of the first positioning portion 338. Therefore, an increase in the number of steps in assembling the endoscope 302 can be suppressed.

[0106] Furthermore, in this embodiment, as described above, the position of the holding member 25 in the optical axis direction relative to the tip member 319 is determined by the second positioning portion 21g of the lens barrel 321, and the circumferential position of the holding member 25 relative to the tip member 319 is determined with high precision by the first positioning portion 338 of the positioning member 336. Therefore, as in the first embodiment described above, even if the dimensional tolerances of the lens barrel 321 and the holding member 25 are both large, it is possible to prevent excessive stress from being applied to the holding member 25. Therefore, it is possible to preferably prevent fluctuations in the relative positions of the objective optical system 23 and the image sensor 31, and in the circumferential position of the image sensor 31 relative to the tip member 319, and therefore it is possible to preferably prevent degradation in the quality of images formed by the endoscope 302.

[0107] 12 is a cross-sectional view showing an imaging unit 420 of this embodiment. In this embodiment, an endoscope 402 includes a tip member 419 and an imaging unit 420. The imaging unit 420 includes a lens barrel 21, an objective optical system 23, a holding member 25, an imaging element 31, and a positioning member 436. In the following description, components that are the same as those in the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted.

[0108] The tip member 419 has a generally circular ring shape extending in the optical axis direction. Although not shown, the tip member 419 is fixed to the inner circumferential surface of the tip case 18c. The tip member 419 has a base 419a, a tip protrusion 19g, and an abutment surface 19h. The tip member 419 is provided with an insertion hole 419c, a plurality of through-holes 19i (see FIG. 4), and a hole 419j.

[0109] The base 419a has a substantially circular ring shape extending in the optical axis direction. The insertion hole 419c is a hole that penetrates the base 419a in the optical axis direction. When viewed from the optical axis direction, the insertion hole 419c has a substantially circular shape centered on the optical axis J. The imaging unit 420 is disposed inside the insertion hole 419c.

[0110] The hole 419j is a hole that penetrates the base 419a in the radial direction. The hole 419j connects the outer peripheral surface of the base 419a, i.e., the outer peripheral surface of the tip member 419, to the inner peripheral surface of the insertion hole 419c. The interior of the insertion hole 419c is radially connected to the outside of the tip member 419 via the hole 419j. In this embodiment, a female thread portion 419k is provided on the inner peripheral surface of the hole 419j. In this embodiment, the hole 419j is a female threaded hole. The female thread portion 419k does not necessarily have to be provided on the inner peripheral surface of the hole 419j. When viewed from the radial direction, the hole 419j overlaps with the second tubular portion 21b. When viewed from the radial direction, the hole 419j overlaps with the positioning member 436. Other configurations of the tip member 419 of this embodiment are similar to those of the tip member 19 of the first embodiment described above.

[0111] The positioning member 436 has a substantially circular ring shape centered on the optical axis J. The positioning member 436 surrounds the second cylindrical portion 21b of the lens barrel 21 from the radially outer side. The positioning member 436 has a main body portion 437, a first positioning portion 438, and a third positioning portion 39.

[0112] The main body portion 437 has a substantially circular ring shape centered on the optical axis J. The main body portion 437 surrounds the second cylindrical portion 21b from the radially outer side. The main body portion 437 extends circumferentially along the outer peripheral surface of the second cylindrical portion 21b. As a result, the positioning member 436 extends circumferentially along the outer peripheral surface of the lens barrel 21. The inner diameter of the main body portion 437 is larger than the outer diameter of the second cylindrical portion 21b. In this embodiment, the inner diameter of the positioning member 436 is slightly larger than the outer diameter of the second cylindrical portion 21b. The inner peripheral surface of the main body portion 437 is fixed to the outer peripheral surface of the second cylindrical portion 21b by adhesive G (not shown). As a result, the positioning member 436 is fixed to the lens barrel 21.

[0113] The first positioning portion 438 is a recess recessed radially inward from the surface of the main body portion 437 facing radially outward. The first positioning portion 438 may be a hole that penetrates the main body portion 437 in the radial direction. When viewed from the radial direction, the first positioning portion 438 has a substantially circular shape. When viewed from the radial direction, the first positioning portion 438 overlaps with the hole portion 419j. Other configurations of the positioning member 436 of this embodiment are similar to those of the positioning member 36 of the first embodiment described above.

[0114] In the present embodiment, a fastening member 481 is passed radially through the hole 419j. The fastening member 481 has a generally cylindrical shape extending radially. An external thread 481a is provided on the outer circumferential surface of the fastening member 481, and the external thread 481a is screwed into the internal thread 419k. This secures the fastening member 481 to the tip member 419. Note that if the internal thread 419k is not provided on the inner circumferential surface of the hole 419j, the fastening member 481 may be secured to the inner circumferential surface of the hole 419j with an adhesive or may be press-fitted into the inner circumferential surface of the hole 419j.

[0115] A radially inner end portion of the fastening member 481 is disposed inside the first positioning portion 438. The outer peripheral surface of the fastening member 481 faces the inner surface of the first positioning portion 438 in the circumferential direction. This uniquely determines the circumferential position of the positioning member 436 relative to the tip member 419. Other configurations, etc. of the positioning member 436 of this embodiment are similar to other configurations, etc. of the positioning member 36 of the first embodiment described above. Other configurations, etc. of the endoscope 402 of this embodiment are similar to other configurations, etc. of the endoscope 2 of the first embodiment described above.

[0116] The fixing step Pf included in the assembly method of the imaging unit 420 of this embodiment is the same as the fixing step Pf of the first embodiment described above. After completing the fixing step Pf, the worker inserts the imaging unit 420 into the insertion hole 419c of the tip member 419 in the assembly process of the endoscope 402, as shown in FIG. 12 . As in the first embodiment described above, when the second positioning portion 21g of the lens barrel 21 contacts the abutting surface 19h of the tip member 419 in the optical axis direction, the worker stops inserting the imaging unit 420 into the insertion hole 419c. At this time, the worker may rotate at least one of the lens barrel 21 and the holding member 25 around the optical axis J so that the first positioning portion 438 overlaps with the hole portion 419j when viewed from the radial direction. Then, the worker tightens the fastening member 481 into the hole portion 419j from the radial outside of the tip member 419. When the radially inner tip of the fastening member 481 is positioned inside the first positioning portion 438, the worker or the like stops tightening the fastening member 481 into the hole portion 419j. This uniquely determines the circumferential position of the positioning member 436 with respect to the tip member 419. The worker or the like then fixes the lens barrel 21 to the tip member 419 by hardening an adhesive (not shown) that has been applied in advance to the outer peripheral surface of the first lens barrel portion 21a of the lens barrel 21. This causes the imaging unit 420 to be held by the tip member 419.

[0117] According to this embodiment, the tip member 419 is provided with a hole 419j that connects the outer peripheral surface of the tip member 419 with the inner peripheral surface of the insertion hole 419c. The first positioning portion 438 is a recess recessed radially inward, and a radially inner end of a fastening member 481 that is passed radially through the hole 419j and fixed to the tip member 419 is disposed in the first positioning portion 438. Therefore, the first positioning portion 438 and the fastening member 481 can uniquely determine the circumferential position of the positioning member 436 relative to the tip member 419. Also, as in the first embodiment described above, the positioning member 436 and the holding member 25 are each fixed to the lens barrel 21. Therefore, as in the first embodiment described above, the positioning member 436 can accurately determine the circumferential positions of the holding member 25 and the image sensor 31 relative to the tip member 419. This can suppress image collapse, thereby improving the quality of images formed by the endoscope 402.

[0118] According to this embodiment, a female thread portion 419k is provided on the inner circumferential surface of the hole portion 419j, and a male thread portion 481a that is screwed into the female thread portion 419k is provided on the outer circumferential surface of the fastening member 481. Therefore, as described above, in the assembly process of the endoscope 402, an operator can fix the fastening member 481 to the tip member 419 by the simple task of screwing the fastening member 481 into the hole portion 419j, and can also determine the circumferential position of the positioning member 436 relative to the tip member 419 by the fastening member 481. Therefore, an increase in the number of steps in assembling the endoscope 402 can be suppressed.

[0119] Furthermore, in this embodiment, as described above, the position of the holding member 25 in the optical axis direction relative to the tip member 419 is determined by the second positioning portion 21g of the lens barrel 21, and the circumferential position of the holding member 25 relative to the tip member 419 is determined with high precision by the first positioning portion 438 of the positioning member 436. Therefore, as in the first embodiment described above, even if the dimensional tolerances of the lens barrel 21 and the holding member 25 are both large, it is possible to prevent excessive stress from being applied to the holding member 25. Therefore, it is possible to preferably prevent fluctuations in the relative positions of the objective optical system 23 and the image sensor 31, and in the circumferential position of the image sensor 31 relative to the tip member 419, and therefore it is possible to preferably prevent degradation in the quality of images formed by the endoscope 402.

[0120] 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.

[0121] 2, 202, 302, 402...endoscope 6...insertion section 19, 319, 419...tip member 19c, 319c, 419c...insertion hole 19e...positioning hole 20, 220, 320, 420...imaging unit 21, 221, 321...lens barrel 21b...second cylindrical section 21c...first cylindrical section 21g...second positioning section 23...objective optical system 23a...lens 31...imaging element 36, 236, 336, 436...positioning member 36a...second positioning section 38, 338, 438...first positioning section 39...third positioning section 237a, 237b...arc section 319e...positioning protrusion 419j...hole 419k...female threaded section 481...fastening member 481a...male threaded section J...Optical axis P01...Application process P02...First mounting process P04...Second mounting process P05...Adjustment process P06...Curing process Pf...Fixing process

Claims

1. An imaging unit held on a tip member of an endoscope, comprising: a cylindrical lens barrel extending in the optical axis direction; an objective optical system constituted by a lens held on the inner peripheral surface of the lens barrel; a holding member attached to the lens barrel and holding an imaging element; and a positioning member attached to the lens barrel, wherein the positioning member has a first positioning portion that determines the circumferential position of the holding member relative to the tip member, centered on the optical axis, and one of the lens barrel and the positioning member has a second positioning portion that determines the position of the lens barrel in the optical axis direction relative to the tip member.

2. An imaging unit as described in claim 1, wherein the positioning member has a third positioning portion that protrudes toward the base end, the holding member has a fourth positioning portion that is recessed toward the base end, and the third positioning portion is engaged with the fourth positioning portion.

3. The imaging unit according to claim 1, wherein the positioning member extends in the circumferential direction along the outer peripheral surface of the lens barrel and is fixed to the outer peripheral surface of the lens barrel.

4. The imaging unit according to claim 1, wherein the positioning member has a plurality of arcuate portions that extend in the circumferential direction along the outer peripheral surface of the lens barrel and are arranged side by side in the circumferential direction, and each of the arcuate portions is fixed to each other and to the outer peripheral surface of the lens barrel.

5. The imaging unit described in claim 1, wherein the holding member has a cylindrical tubular portion that extends in the optical axis direction with the optical axis as its center, the lens barrel has a first cylindrical portion that extends in the optical axis direction with the optical axis as its center, the inner diameter of the cylindrical portion is larger than the outer diameter of the first cylindrical portion, and the inner surface of the cylindrical portion is fixed to the outer surface of the first cylindrical portion with an adhesive.

6. The imaging unit according to claim 1, wherein the lens barrel has a cylindrical second cylindrical portion that extends in the optical axis direction with the optical axis as its center, the inner diameter of the positioning member is larger than the outer diameter of the second cylindrical portion, and the inner peripheral surface of the positioning member is fixed to the outer peripheral surface of the second cylindrical portion with an adhesive.

7. The imaging unit according to claim 1, wherein the holding member has a rectangular cylindrical imaging holding section that extends in the optical axis direction with the optical axis as its center, the imaging element is fixed to a surface facing the base end of the imaging holding section, and the outer edges of the imaging element and the imaging holding section are each rectangular when viewed in the optical axis direction.

8. An endoscope comprising an imaging unit according to claim 1 and a tip member that holds said imaging unit, said tip member having an insertion hole that penetrates in the direction of said optical axis, and said imaging unit being placed inside said insertion hole.

9. An endoscope as described in claim 8, wherein the inner surface of the insertion hole is provided with a positioning hole that is recessed radially outward from the optical axis and extends in the direction of the optical axis, the positioning hole being open on the base end side, and the first positioning portion protruding radially outward and positioned inside the positioning hole.

10. An endoscope as described in claim 8, wherein the inner surface of the insertion hole is provided with a positioning protrusion that protrudes radially inward around the optical axis, the first positioning portion is a groove that is recessed radially inward and extends in the optical axis direction and is open to the object side, and the positioning protrusion is located inside the first positioning portion.

11. An endoscope as described in claim 8, wherein the tip member is provided with a hole portion connecting the outer peripheral surface of the tip member and the inner peripheral surface of the insertion hole, the first positioning portion is a recess recessed radially inward, and the first positioning portion is arranged to receive the radially inner end of a fastening member that is passed radially through the hole portion and fixed to the tip member.

12. An endoscope according to claim 11, wherein the inner peripheral surface of the hole is provided with a female thread portion, and the outer peripheral surface of the fastening member is provided with a male thread portion that is screwed into the female thread portion.

13. A method for assembling an imaging unit comprising: a cylindrical lens barrel extending in the optical axis direction; an objective optical system constituted by a lens held on the inner peripheral surface of the lens barrel; a holding member fixed to the lens barrel and holding an imaging element; and a positioning member fixed to the lens barrel, the method for assembling the imaging unit comprising: a fixing step of fixing the holding member to the lens barrel, the positioning member having a third positioning portion protruding toward the base end, and the holding member having a fourth positioning portion recessed toward the base end, the fixing step comprising: an application step of applying adhesive to the outer peripheral surface of the lens barrel; a first attachment step of attaching the positioning member to the outer peripheral surface of the lens barrel via the adhesive; a second attachment step of attaching the holding member to the lens barrel via the adhesive while engaging the third positioning portion with the fourth positioning portion; an adjustment step of adjusting the position of the objective optical system in the optical axis direction relative to the imaging element and its position in the circumferential direction around the optical axis; and a curing step of curing the adhesive.

Images