WO2021193337A1

WO2021193337A1 - Endoscope

Info

Publication number: WO2021193337A1
Application number: PCT/JP2021/011029
Authority: WO
Inventors: 将人瀧ヶ平; 雄大松田
Original assignee: 株式会社フジクラ; ファイバーテック株式会社
Priority date: 2020-03-26
Filing date: 2021-03-18
Publication date: 2021-09-30
Also published as: JPWO2021193337A1; JP7362902B2

Abstract

This endoscope comprises an image fiber, an imaging element, and a re-imaging optical system. The re-imaging optical system comprises: a re-imaging optical system that has a first lens optical system and a second lens optical system, is disposed between the image fiber and the imaging element, and re-images, on the imaging element, a subject image transmitted by the image fiber; a first lens barrel that holds the first lens optical system; a second lens barrel that holds the second lens optical system; a housing part that fixes the relative positions of the second lens barrel and the imaging element, and accommodates the first lens barrel to be relatively movable; and an urging member that is disposed between the first lens barrel and the second lens barrel and urges the first lens barrel toward the image fiber. The first lens optical system is configured to convert light incident from the image fiber into parallel light, and the second lens optical system is configured to collect the parallel light onto the imaging element. A diaphragm is disposed between the first lens optical system and the second lens optical system, and the diaphragm is fixed to the first lens barrel.

Description

Endoscope

The present invention relates to an endoscope.
The present application claims priority with respect to Japanese Patent Application No. 2020-056093 filed in Japan on March 26, 2020, the contents of which are incorporated herein by reference.

The following Patent Document 1 describes an image guide (image fiber) that transmits a subject image created by an objective lens unit to an endoscope operation unit, and an endoscope operation unit that reimages the subject image on a solid-state imaging element. Disclosed is an endoscope comprising a reimaging optical system arranged in.

Japanese Patent Application Laid-Open No. 2003-84214

In such an endoscope, if the length of the image fiber varies due to manufacturing error or the like, the end face of the image fiber deviates from the focal position of the lens, and there is a problem that a desired image formation cannot be obtained on the image sensor. be. In order to deal with this problem, in the above-mentioned prior art, a bilateral telecentric optical system is used for the lens system that optically couples the image fiber and the image sensor. The bilateral telecentric optical system is an optical system in which a diaphragm having a small aperture is placed at a focal position between the front lens group and the rear lens group so that the optical axis and the main ray can be regarded as parallel.
This optical system has an advantage that a stable image can be obtained even if the end face position of the image fiber is displaced with respect to the lens. However, although there is no clear description in Patent Document 1, in order to obtain the above effect sufficiently, it is necessary to set the aperture diameter of the diaphragm to 1/5 to 1/10 or less of the effective diameter of the lens. Therefore, there is a problem that the subject image acquired by the image sensor becomes darker than that of a normal lens system.

The present invention has been made in view of the above problems, and it is possible to prevent the end face of the image fiber from deviating from the focal position of the reimaging optical system and obtain a stable image formation on the image sensor. The purpose is to provide an endoscope.

The endoscope according to one aspect of the present invention has an image fiber, an image pickup element, a first lens optical system and a second lens optical system, and is arranged between the image fiber and the image pickup element. A re-imaging optical system for re-imaging the subject image transmitted by the image fiber on the image pickup element, a first lens barrel holding the first lens optical system, and the like.
A second lens barrel that holds the second lens optical system, a housing portion that fixes the relative positions of the second lens barrel and the image pickup element, and accommodates the first lens barrel so as to be relatively movable, and the above. An urging member arranged between the first lens barrel and the second lens barrel and urging the first lens barrel toward the image fiber, and the first lens optical system and the second lens optical system. It is equipped with an optics arranged between and. The first lens optical system is configured to convert light incident from the image fiber into parallel light, and the second lens optical system is configured to focus the parallel light on the image pickup element. There is. The diaphragm is fixed to the first lens barrel.
According to this configuration, the variation in the length of the image fiber in manufacturing is absorbed by the variation in the distance between the first lens optical system and the second lens optical system via the urging member, so that the end face of the image fiber is absorbed. It is always arranged within the depth of field of the first lens optical system. Since there is almost parallel light between the first lens optical system and the second lens optical system, even if the distance between the first lens optical system and the second lens optical system changes, it is on the image pickup element as in the telecentric system. A stable image can be obtained with. Further, since the re-imaging optical system can be a non-telecentric system, the number of lenses is small and the total length can be made compact.
Further, since the diaphragm is arranged between the first lens optical system and the second lens optical system and the diaphragm is fixed to the first lens barrel, unnecessary light that does not need to be incident on the second lens optical system is required. It is possible to leave the light that needs to be incident on the second lens optical system while cutting the light.

In the endoscope, the image fiber may be held by a fiber holder detachably attached to the housing portion.

In the endoscope, the fiber holder has an insertion portion that is insertably inserted into the housing portion, and the first lens barrel is inserted into the insertion portion by the urging of the urging member. It may be pressed.

In the endoscope, the housing portion has a wall portion in which an insertion hole for the insertion portion is formed, and the insertion portion projects to the accommodation space of the first lens barrel inside the wall portion. You may be.

In the endoscope, the aperture diameter of the diaphragm may be set to 1 / 1.1 or more and 1 / 1.3 or less of the effective diameter of the first lens optical system.

In the endoscope, the length of the diaphragm in the arrangement direction of the first lens barrel and the second lens barrel may be 1.1 mm or more and 3.8 mm or less.

According to the above aspect of the present invention, it is possible to provide an endoscope capable of preventing the end face of the image fiber from deviating from the focal position with the reimaging optical system and obtaining a stable image formation on the image pickup device. ..

It is a perspective view of the endoscope which attached the protective cap which concerns on one Embodiment. It is an endoscope perspective view which removed the protective cap which concerns on one Embodiment. It is sectional drawing of the endoscope which concerns on one Embodiment. It is sectional drawing which enlarged the inside of the endoscope which concerns on one Embodiment. It is a block diagram of the re-imaging optical system which concerns on one Embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, an electronic endoscope for ophthalmology will be illustrated.

First, the overall outline of the endoscope 1 will be described.
FIG. 1 is a perspective view of an endoscope 1 equipped with a protective cap 2 according to an embodiment. FIG. 2 is a perspective view of the endoscope 1 from which the protective cap 2 according to the embodiment is removed. FIG. 3 is a cross-sectional configuration diagram of the endoscope 1 according to the embodiment.
As shown in these figures, the endoscope 1 includes an endoscope operation unit 10, an insertion observation unit 20 extending forward from the endoscope operation unit 10, and a removable protective cap 2 that covers the insertion observation unit 20. And have.

In the following description, the XYZ Cartesian coordinate system may be set, and the positional relationship of each member may be described with reference to this XYZ Cartesian coordinate system. The X-axis direction is the longitudinal direction in which the insertion observation unit 20 extends, and the Y-axis direction and the Z-axis direction are two-axis orthogonal directions (also referred to as the lateral directions of the insertion observation unit 20) orthogonal to the X-axis direction. ..

In the longitudinal direction in which the insertion observation unit 20 extends, the "front" is the tip 21 side (+ X side) in the insertion observation unit 20, and the "rear" is opposite to the tip 21 in the insertion observation unit 20. This is the side (-X side, that is, the base end (root) side of the insertion observation unit 20).

As shown in FIG. 1, the protective cap 2 includes a mounting portion 3 mounted on the endoscope operating portion 10 and a tip accommodating portion 4 extending forward from the mounting portion 3 and covering the insertion observation portion 20. There is. The mounting portion 3 is formed in a substantially cylindrical shape surrounding the outer periphery of the endoscope operating portion 10. The tip accommodating portion 4 is formed in a substantially bottomed cylindrical shape surrounding the outer periphery of the insertion observation portion 20 and the tip 21.

An engagement hole 5 that opens in the Z-axis direction and a plurality of communication holes 6 are formed on the outer periphery of the mounting portion 3. The protective cap 2 is engaged with the engaging hole 5 by the engaging projection 12 formed on the front side of the endoscope operating portion 10 shown in FIGS. 2 and 3 and protruding in the Z-axis direction, whereby the protective cap 2 is attached to the endoscope. It is detachably attached to the operation unit 10. The communication hole 6 enables sterilization of the endoscope operation unit 10 and the insertion observation unit 20 with the protective cap 2 attached. That is, the structure is such that the sterilizing gas can flow into the protective cap 2 from the communication hole 6.

As shown in FIGS. 2 and 3, the insertion observation unit 20 is formed in the shape of an elongated needle extending in the X-axis direction. An objective lens is provided at the tip 21 of the insertion observation unit 20. The insertion observation unit 20 includes an image fiber 22 (optical fiber) that transmits the subject image acquired via the objective lens to the endoscope operation unit 10, and an illumination fiber 23 (optical fiber) that irradiates illumination light forward from the tip 21. Fiber) and.

The image fiber 22 is arranged inside a hard outer cylinder (stainless steel pipe or the like) (not shown). The illumination fiber 23 is also arranged inside the hard outer cylinder, like the image fiber 22. The other end of the illumination fiber 23 passes through the subcutaneous portion of the outer surface of the endoscope operation unit 10 and is connected to an illumination device (light source) (not shown). Instead of the illumination fiber 23, a small illumination device (LED or the like) may be provided at the tip 21 of the insertion observation unit 20.

As shown in FIG. 2, the endoscope operation unit 10 is formed in a substantially pen shape (also referred to as a substantially columnar shape having a conical portion on the front side) having a grip portion 11 on the front side in the X-axis direction. Inside the endoscope operation unit 10, as shown in FIG. 3, an image pickup device 30 such as a CCD or CMOS and reimaging optics for re-imaging the subject image transmitted by the image fiber 22 on the image pickup device 30. System 40 and.

The image sensor 30 converts the reimaged subject image into electronic image data. As shown in FIG. 2, the electronic image data is transmitted to an image processing device (not shown) via a cable 13 extending rearward from the endoscope operating unit 10. The image processing device displays electronic image data on a monitor or stores it in a storage medium.

Next, the internal configuration of the endoscope 1 will be described in detail with reference to FIGS. 4 and 5.

FIG. 4 is an enlarged cross-sectional configuration view of the inside of the endoscope 1 according to the embodiment. FIG. 5 is a configuration diagram of the re-imaging optical system 40 according to the embodiment.
As shown in these figures, a reimaging optical system 40 is provided between the image fiber 22 and the image sensor 30 to reimage the subject image transmitted by the image fiber 22 on the image sensor 30. ..

As shown in FIG. 5, the re-imaging optical system 40 has a first lens optical system 40A that converts light incident from the end surface 22a of the image fiber 22 into parallel light, and the parallel light is focused on the image pickup element 30. It has a second lens optical system 40B. The first lens optical system 40A is arranged on the image fiber 22 side (front side). Further, the second lens optical system 40B is arranged on the rear side (image sensor 30 side) of the first lens optical system 40A.

The first lens optical system 40A is formed by a lens group in which the first lens 41, the second lens 42, and the third lens 43 are arranged in this order from the image fiber 22 side in the optical axis direction (X-axis direction). The first lens 41 is a plano-convex lens and mainly has a function of converting light incident from the end surface 22a of the image fiber 22 into parallel light. The second lens 42 is a biconvex lens, and is characterized in that the difference in refractive index depending on the color is small. The third lens 43 is a concave meniscus lens, and in the present embodiment, the emitted light is made parallel. Further, since the second lens 42 which is a convex lens and the third lens 43 which is a concave meniscus lens have opposite directions in which spherical aberration occurs, it is possible to suppress spherical aberration by combining them as shown in FIG. Become. Further, the second lens 42 has a small difference in the refractive index depending on the color, and conversely, the third lens 43 has a large difference in the refractive index depending on the color. By combining lenses with different refractive indexes in this way, axial chromatic aberration can be corrected.

The second lens optical system 40B is formed by a lens group in which the fourth lens 44, the fifth lens 45, the sixth lens 46, and the seventh lens 47 are arranged in this order from the image fiber 22 side in the optical axis direction (X-axis direction). It is formed. The fourth lens 44 is a plano-convex lens, and in the present embodiment, it has a function of collecting light incident in parallel. The fifth lens 45 is a biconvex lens, and like the second lens 42, has a feature that the difference in refractive index depending on the color is small. The sixth lens 46 is a plano-concave lens, and similarly, it corrects spherical aberration and axial chromatic aberration by combining with the fifth lens 45, which is a biconvex lens. The seventh lens 47 is an IR cut filter and has a function of preventing infrared light outside the visible region from being incident on the image sensor 30.

As shown in FIG. 4, the first lens optical system 40A is held in the first lens barrel 70. The inner peripheral surface of the first lens barrel 70 has a diameter reduced in two steps toward the front side, and has a first step portion 71 and a second step portion 72. The first lens optical system 40A is arranged in the first step portion 71. The front side of the inner peripheral surface of the first lens barrel 70 from the first step portion 71 has a slightly smaller diameter than the outer diameter of the first lens optical system 40A, and the outer peripheral edge of the first lens optical system 40A and the X-axis. They are facing each other in the direction.

A second step portion 72 is provided on the rear side of the first step portion 71. A diaphragm 100 is screwed into the second step portion 72. The diaphragm 100 is formed in a cylindrical shape, and a male screw is formed on the outer peripheral surface thereof. The throttle 100 is formed with a slit 101 that can be screwed. The inner peripheral surface of the aperture 100 is slightly reduced in diameter from the outer diameter of the first lens optical system 40A. The diaphragm 100 is fixed to the first lens barrel 70 by screwing with a female screw formed on the inner peripheral surface of the second step portion 72. That is, the aperture 100 is arranged at a fixed position from the first lens barrel 70. As a result, the relative positions of the aperture 100 and the first lens optical system 40A are not changed.

Next, the position of the aperture 100 will be described.
The light emitted from the first lens optical system 40A is parallel light, but the optical path is slightly different depending on the wavelength. The optical paths corresponding to these wavelengths overlap at a position separated from the first lens optical system 40A by a predetermined distance (hereinafter, this position is referred to as an overlapping position). The diaphragm 100 is arranged at this overlapping position. Since the overlapping position is determined by the first lens optical system 40A, it is not necessary to enter the second lens optical system 40B by fixing the aperture 100 to the first lens barrel 70 so that the aperture 100 is located at the overlapping position. It is possible to leave the light that needs to be incident on the second lens optical system 40B while cutting unnecessary light.

The aperture diameter of the aperture 100 may be set to 1 / 1.1 or more and 1 / 1.3 or less of the effective diameter of the first lens optical system 40A. In particular, the aperture diameter of the diaphragm 100 is not limited, but the minimum diaphragm inner diameter that does not block the optical path of the light emitted from the first lens optical system 40A is preferably 1 / 1.1 or more. Further, as the maximum inner diameter of the diaphragm that can be processed, the aperture diameter of the diaphragm 100 is preferably 1 / 1.3 of the effective diameter of the first lens optical system 40A.
The length L of the aperture 100 in the arrangement direction (X-axis direction) of the first lens barrel 70 and the second lens barrel 80 may be 1.1 mm or more and 3.8 mm or less. In particular, the length L of the diaphragm 100 is not limited, but it is preferable that the length L of the diaphragm 100 is 1.1 mm or more as a length that can be manufactured in manufacturing. Further, if the length L of the diaphragm is too long, it interferes with the second lens optical system 40B arranged after the first lens optical system 40A, so that the length L of the diaphragm 100 is 3.8 mm or less. It is preferable to have.

Further, as shown in FIG. 4, the second lens optical system 40B is held in the second lens barrel 80. The inner peripheral surface of the second lens barrel 80 has a stepped portion 81 whose diameter is reduced in one step toward the rear side. The second lens optical system 40B is arranged on the step portion 81. A ring-shaped spacer 82 is arranged between the sixth lens 46 and the seventh lens 47. The rear side of the inner peripheral surface of the second lens barrel 80 from the stepped portion 81 is slightly smaller than the outer diameter of the second lens optical system 40B, and is slightly smaller than the outer diameter of the second lens optical system 40B in the X-axis direction with the outer peripheral edge of the second lens optical system 40B. Are facing each other.

The first lens barrel 70 and the second lens barrel 80 are housed in the housing portion 50 of the endoscope operation unit 10. As shown in FIG. 3, the endoscope operating unit 10 has a housing unit 50 and a fiber holder 60 that is detachably attached to the housing unit 50. The housing portion 50 is the main body portion of the endoscope 1 that holds the re-imaging optical system 40, the image pickup element 30, and the like. The fiber holder 60 is a replacement part for the endoscope 1 that holds the insertion observation unit 20 (image fiber 22 and illumination fiber 23) and the like.

The fiber holder 60 has a bottomed cylindrical hard cover 61 made of polycarbonate or the like, and an elastic cover 62 formed of silicone rubber or the like and covering at least a part of the outer surface of the hard cover 61. A columnar insertion portion 61a projecting rearward toward the housing portion 50 is formed on the front bottom portion of the hard cover 61. The image fiber 22 is arranged so as to pass through the central axis of the insertion portion 61a. As shown in FIG. 4, the end face 22a of the image fiber 22 is end face processed (polished or the like) so as to be flush with the tip of the insertion portion 61a.

The housing portion 50 has a first tubular body 51 having a wall portion 51a, a second tubular body 52 fitted to the rear side of the first tubular body 51, and a second tubular body 52 fitted to the rear side of the second tubular body 52. It has a three-cylinder body 53 and. The wall portion 51a is formed with an insertion hole 51b into which the insertion portion 61a is inserted in the X-axis direction. A protrusion (not shown) is formed on the outer peripheral surface of the first cylinder 51, and the connection piece 54 of the fiber holder 60 is engaged with the protrusion. The fiber holder 60 is bayonet-connected to the outer peripheral surface of the first tubular body 51 via a connecting piece 54.

As shown in FIG. 4, the first cylinder body 51 accommodates the above-mentioned first lens barrel 70 so as to be movable in the X-axis direction. The wall portion 51a described above is provided on the front side of the first tubular body 51, and the second tubular body 52 is fitted on the rear side of the first tubular body 51. The second lens barrel 80 is fixed to the second cylinder 52 via a set screw 84. The second lens barrel 80 projects forward from the second barrel 52 and is inserted inside the first barrel 51.

The third cylinder 53 is fitted on the rear side of the second cylinder 52. The image sensor 30 is fixed to the third cylinder 53. By fitting the third cylinder 53 into the second cylinder 52, the relative positions of the second lens barrel 80 and the image sensor 30 are fixed. The first lens barrel 70 is housed in the first barrel body 51 and is configured to be movable relative to the second lens barrel 80 in the X-axis direction.

As shown in FIG. 4, an urging member 90 is arranged between the first lens barrel 70 and the second lens barrel 80. The urging member 90 of the present embodiment is a coil spring that urges the first lens barrel 70 toward the image fiber 22. A spring receiver 83 for the urging member 90 is formed on the outer peripheral surface of the front end portion of the second lens barrel 80. The urging member 90 may be an elastic member such as a rubber ring as long as it has an elastic force without obstructing the optical path like the coil spring.

The front side of the first lens barrel 70 is pressed against the tip of the insertion portion 61a of the fiber holder 60 (hard cover 61) by the urging of the urging member 90. The insertion portion 61a projects to a space inside the wall portion 51a of the first cylinder body 51 (accommodation space of the first lens barrel 70). That is, the first lens barrel 70 is in contact with the insertion portion 61a due to the urging of the urging member 90, but is not in contact with the wall portion 51a.

According to the endoscope 1 having the above configuration, the first lens barrel 70 is pressed against the insertion portion 61a by the urging of the urging member 90, and the relative position between the end surface 22a of the image fiber 22 and the first lens optical system 40A. The relationship is fixed. Therefore, the variation in the length of the image fiber 22 in manufacturing (the variation in the position in the X-axis direction due to the processing of the end face 22a (tip of the insertion portion 61a) of the image fiber 22) is caused by the urging member 90. It is absorbed by the fluctuation of the distance between the one-lens optical system 40A and the second lens optical system 40B. Therefore, the end face 22a of the image fiber 22 is always arranged within the depth of field of the first lens optical system 40A. Since there is almost parallel light between the first lens optical system 40A and the second lens optical system 40B, even if the distance between the first lens optical system 40A and the second lens optical system 40B changes, the same as in the telecentric system. , A stable image can be obtained on the image pickup element 30. Further, since the re-imaging optical system 40 can be a non-telecentric system, the number of lenses is small and the total length can be made compact.

As described above, according to the above-described embodiment, the image fiber 22, the image pickup element 30, and the subject image transmitted between the image fiber 22 and the image pickup element 30 are captured by the image pickup element 30. The re-imaging optical system 40 includes a re-imaging optical system 40 that reimages the light, and the re-imaging optical system 40 captures the first lens optical system 40A that converts the light incident from the image fiber 22 into parallel light and the parallel light. A first lens barrel 70 that has a second lens optical system 40B that condenses light on the element 30 and holds the first lens optical system 40A, and a second lens barrel 80 that holds the second lens optical system 40B. The housing portion 50, which fixes the relative positions of the second lens barrel 80 and the image pickup element 30 and accommodates the first lens barrel 70 so as to be relatively movable, and the first lens barrel 70 and the second lens barrel 80. By adopting a configuration in which the first lens barrel 70 is provided with an urging member 90 for urging the image fiber 22 toward the image fiber 22, the end face 22a of the image fiber 22 is reimaged with the optical system 40. It is possible to prevent deviation from the focal position with and to obtain a stable image formation on the image pickup element 30.

Further, in the present embodiment, the diaphragm 100 is arranged between the first lens optical system 40A and the second lens optical system 40B. According to this configuration, by fixing the aperture 100 to the first lens barrel 70 so that the aperture 100 is located at the overlapping position, unnecessary light that does not need to be incident on the second lens optical system 40B (unnecessary place). It is possible to leave the light that needs to be incident on the second lens optical system 40B while cutting the reflected light and the light that passes through the outer edge of the lens. As a result, the endoscope according to the present embodiment can obtain a clear image.
Since the aperture diameter of the diaphragm is set to 1 / 1.1 or more and 1 / 1.3 or less of the effective diameter of the first lens optical system 40A, the aperture of the diaphragm 100 is large and the image is brighter than that of the telecentric system. Is obtained.

Further, in the present embodiment, as shown in FIG. 3, the image fiber 22 is held by the fiber holder 60 which is detachably attached to the housing portion 50. According to this configuration, even if there is a variation in the length of the image fiber 22 for each replacement part of the fiber holder 60, this variation is caused by the first lens optical system 40A and the second lens optical via the urging member 90. It can be absorbed by the variation of the distance of the system 40B.

Further, in the present embodiment, the fiber holder 60 has an insertion portion 61a that is insertably inserted into the housing portion 50, and the first lens barrel 70 is an urging member 90 as shown in FIG. It is pressed against the insertion portion 61a by the urging of. According to this configuration, since the first lens barrel 70 is pressed against the fiber holder 60 itself that holds the image fiber 22, it is possible to prevent the end surface 22a of the image fiber 22 from deviating from the focal position of the first lens optical system 40A.

Further, in the present embodiment, the housing portion 50 has a wall portion 51a in which the insertion hole 51b of the insertion portion 61a is formed, and the insertion portion 61a accommodates the first lens barrel 70 inside the wall portion 51a. It protrudes to the space. According to this configuration, the first lens barrel 70 is not pressed against the wall portion 51a but is pressed only against the insertion portion 61a, so that the end face 22a of the image fiber 22 is surely the depth of field of the first lens optical system 40A. Placed inside.

Although the preferred embodiments of the present invention have been described and described above, it should be understood that these are exemplary of the present invention and should not be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the scope of the invention. Therefore, the present invention should not be considered limited by the above description, but is limited by the claims.

1 ... Endoscope, 22 ... Image fiber, 22a ... End face, 30 ... Imaging element, 40 ... Reimaging optical system, 40A ... 1st lens optical system, 40B ... 2nd lens optical system, 50 ... Housing 51a ... wall part, 51b ... insertion hole, 60 ... fiber holder, 61a ... insertion part, 70 ... first lens barrel, 80 ... second lens barrel, 90 ... urging member

Claims

Image fiber and
Image sensor and
Reconnection that has a first lens optical system and a second lens optical system, is arranged between the image fiber and the image sensor, and reimages a subject image transmitted by the image fiber on the image sensor. Image optics and
The first lens barrel that holds the first lens optical system and
A second lens barrel that holds the second lens optical system and
A housing portion that fixes the relative position of the second lens barrel and the image sensor and accommodates the first lens barrel so as to be relatively movable.
An urging member arranged between the first lens barrel and the second lens barrel and urging the first lens barrel toward the image fiber.
A diaphragm arranged between the first lens optical system and the second lens optical system,
With
The first lens optical system is configured to convert light incident from the image fiber into parallel light.
The second lens optical system is configured to collect the parallel light on the image pickup device.
An endoscope in which the diaphragm is fixed to the first lens barrel.
The endoscope according to claim 1, wherein the image fiber is held by a fiber holder detachably attached to the housing portion.
The fiber holder has an insertion portion that is removably inserted inside the housing portion.
The endoscope according to claim 2, wherein the first lens barrel is pressed against the insertion portion by the urging of the urging member.
The housing portion has a wall portion in which an insertion hole for the insertion portion is formed.
The endoscope according to claim 3, wherein the insertion portion projects to the accommodation space of the first lens barrel inside the wall portion.
The method according to any one of claims 1 to 4, wherein the aperture diameter of the diaphragm is set to 1 / 1.1 or more and 1 / 1.3 or less of the effective diameter of the first lens optical system. Endoscope.
The length of the diaphragm in the arrangement direction of the first lens barrel and the second lens barrel is
The endoscope according to any one of claims 1 to 5, which is 1.1 mm or more and 3.8 mm or less.