Optical adapter, endoscope used with the optical adapter attached, and endoscope having an optical system at the tip of the insertion section

Abstract

To provide an optical adapter that enables enlarging an incidence surface of a prism while securing holding strength as maintaining a size of an outer diameter of an adapter main body, and enables securing a wide field of vision.SOLUTION: An optical adapter has: a prism 22 that has an incidence surface 22a upon which observation light from a subject is incident; and a holding member 23a that holds the prism. A projection shape of the prism upon viewing from an insertion axis X direction of an endoscope insertion part 2 is formed into a polygonal shape (the number of corners n≥4; n is a natural number). The polygonal shape has: an incidence side 22a that serves as a part of the incidence surface; one or more opposite sides 22b that face with respect to the incidence side across the insertion axis; and at least more than two oblique sides 22c that couple the incidence side and opposite side, in which the incidence side is formed longer than the opposite side. The holding member holds at least one part of respective oblique sides of the prism, and the polygonal shape has a configuration so that an intersection of a straight line extending the incidence side with each straight line extending respectively each oblique side does not abut with the holding member.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an optical adapter that can be attached and detached to the tip of an endoscope insertion section, and in particular to an optical adapter that can ensure a lateral field of view, an endoscope that is used with this optical adapter attached, and an endoscope that has an optical system at the tip of the insertion section. [Background technology]

[0002] 2. Description of the Related Art Conventionally, endoscopes have been widely used in, for example, the medical field, the industrial field, etc. In general, an endoscope is configured to have an insertion section having a thin and slender tube shape and a tip section provided at the tip of the insertion section.

[0003] A medical endoscope is used by inserting an insertion section equipped with an imaging unit into, for example, a body cavity of a living organism. At this time, images of lesions and the like inside organs of the living organism are acquired using the imaging unit. The endoscope user then observes and examines the condition of the lesions and the like based on the acquired images.

[0004] In addition, industrial endoscopes are used by inserting an insertion section equipped with an imaging unit into equipment or machinery such as jet engines or factory piping. At this time, images of scratches, corrosion, etc. inside the equipment or machinery are obtained using the imaging unit. The endoscope user then observes and inspects the condition of the scratches, corrosion, etc. based on the obtained images.

[0005] In this type of conventional endoscope, an optical adapter is provided as an optional device for obtaining an optimal field of view for the subject to be observed. Various proposals for this type of optical adapter have been made, for example, in International Publication No. WO2017 / 086298A1.

[0006] The optical adapter disclosed in the above-mentioned International Publication No. WO2017 / 086298A1 and the like is a side-viewing optical adapter that is configured to be detachably attached to the tip of the endoscope insertion portion and ensures a lateral field of view in the insertion direction of the endoscope insertion portion.

[0007] Generally, a side-viewing optical adapter or a side-viewing endoscope is configured with a prism or the like, which is an optical element that bends the optical path of a light beam incident from an incident surface and guides it to the light-receiving surface of an imaging element. By using this type of prism, a side-viewing optical adapter or a side-viewing endoscope changes the optical path of light incident from the side relative to the insertion direction (insertion axis direction) of the endoscope insertion portion to a direction along the insertion axis. Therefore, for example, by attaching a side-viewing optical adapter to the tip of the insertion portion of a direct-viewing endoscope, the direct-viewing endoscope can be used as a side-viewing endoscope.

[0008] Conventional optical adapters such as those disclosed in International Publication No. WO2017 / 086298A1 employ a configuration in which a holding portion provided on the main body member holds substantially the entire side surface of the prism. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. WO2017 / 086298A1 Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the prism holding structure of the optical adapter disclosed in International Publication No. WO2017 / 086298A1 and the like, for example, increasing the thickness of the holding portion is considered to ensure the prism holding strength. In this configuration, if the outer diameter of the adapter body is to be maintained, the width of the prism must be reduced. If the prism is made smaller, the entrance surface of the prism becomes narrower. This causes a problem of narrowing the observation field of view.

[0011] On the other hand, if an attempt is made to increase the width of the prism in order to widen the observation field while ensuring the required prism holding strength, the problem arises that the outer diameter of the adapter body becomes larger.

[0012] The present invention aims to provide an optical adapter that can enlarge the entrance surface of the prism while maintaining the outer diameter size of the adapter body and ensuring the holding strength of the prism, thereby ensuring a wide field of view, as well as an endoscope that can be used with this optical adapter attached and an endoscope that has an optical system at the tip of the insertion section. [Means for solving the problem]

[0013] In order to achieve the above object, a side-viewing optical adapter according to one aspect of the present invention is an optical adapter that can be attached / detached to the tip of an endoscope insertion section, and includes a prism having an incident surface onto which observation light from a subject is incident, and a holding member that holds the prism, wherein the prism has a polygonal shape (number of angles n≧4; n is a natural number) projected when viewed from the insertion axis direction of the endoscope insertion section, and the polygonal shape has an incident side that is a part of the incident surface, one or more opposite sides that face the incident side across the insertion axis, and at least two or more oblique sides that connect the incident side and the opposite side, and the incident side is formed longer than the opposite side, and the holding member holds at least a part of each of the oblique sides of the prism, and the holding member is configured such that an intersection of a straight line extending the incident side and each of the at least two or more oblique sides does not abut on the holding member.

[0014] An endoscope according to one aspect of the present invention is an endoscope that is used by attaching a detachable optical adapter to the distal end of an insertion section, the optical adapter having a prism having an incident surface onto which observation light from a subject is incident, and a holding member that holds the prism, , withinThe projection shape when viewed from the insertion axis direction of the endoscope insertion part is formed into a polygonal shape (number of angles n≧4; n is a natural number), and the polygonal shape has an incident side that is a part of the incident surface, one or more opposite sides that face the incident side across the insertion axis, and at least two or more hypotenuses that connect the incident side and the opposite sides, and the incident side is formed to be longer than the opposite sides, and the holding member holds at least a part of each of the hypotenuses of the prism, and the intersections of each straight line extending the incident side and each straight line extending each of the at least two or more hypotenuses do not abut the holding member.

[0015] Another aspect of the present invention is an endoscope having an optical system at the tip of an insertion section, the optical system having a prism having an incident surface onto which observation light from a subject is incident, and a holding member for holding the prism, , within The projection shape when viewed from the insertion axis direction of the endoscope insertion part is formed into a polygonal shape (number of angles n≧4; n is a natural number), and the polygonal shape has an incident side that is a part of the incident surface, one or more opposite sides that face the incident side across the insertion axis, and at least two or more oblique sides that connect the incident side and the opposite sides, and the incident side is formed to be longer than the opposite sides, and the holding member holds at least a part of each of the oblique sides of the prism, and the intersection of a straight line extending the incident side and a straight line extending each of the at least two or more oblique sides does not abut the holding member. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide an optical adapter that can enlarge the entrance surface of the prism while maintaining the outer diameter size of the adapter body and ensuring holding strength, thereby ensuring a wide field of view, as well as an endoscope that is used by attaching this optical adapter and an endoscope that has an optical system at the tip of the insertion section. [Brief explanation of the drawings]

[0017] [Figure 1]FIG. 1 is a diagram showing the overall configuration of an endoscope device that can be used by attaching an optical adapter according to a first embodiment of the present invention; [Figure 2] FIG. 1 is a perspective view showing the appearance of an optical adapter according to a first embodiment of the present invention; [Figure 3] A cross-sectional view along the plane indicated by the arrow [3] in Figure 2. [Figure 4] Cross-sectional view along line [4]-[4] in Figure 3; [Figure 5] FIG. 3 is an exploded perspective view of the optical adapter of FIG. 2 with the optical adapter cover removed; [Figure 6] FIG. 3 is an exploded perspective view of the optical adapter of FIG. 2; [Figure 7] 3 is a side view of the optical adapter of FIG. 2 other than the optical adapter cover; [Figure 8] Front view seen from the direction of arrow [8] in Figure 7. [Figure 9] FIG. 3 is an external perspective view showing only a prism in the optical adapter of FIG. 2; [Figure 10] 3 is a cross-sectional view showing a first modified example of the prism shape in the optical adapter of FIG. 2; [Figure 11] 3 is a cross-sectional view showing a second modified example of the prism shape in the optical adapter of FIG. 2; [Figure 12] FIG. 10 is a perspective view showing the appearance of an optical adapter according to a second embodiment of the present invention; [Figure 13] 13 is an exploded perspective view of the optical adapter of FIG. 12; [Figure 14] 13 is a perspective view showing the configuration of the optical adapter of FIG. 12 with the optical adapter cover removed; FIG. [Figure 15] Front view seen from the direction of arrow

[15] in Figure 14. [Figure 16] 13 is a cross-sectional view showing a modification of the prism shape in the optical adapter of FIG. 12; [Figure 17] FIG. 10 is a perspective view showing the appearance of an optical adapter according to a third embodiment of the present invention; [Figure 18] A cross-sectional view along the plane indicated by the arrow

[18] in Figure 17; [Figure 19] A cross-sectional view taken along the line

[19] -

[19] in Figure 18. [Figure 20] 18 is an exploded perspective view of the optical adapter of FIG. 17 with the optical adapter cover removed; [Figure 21] 18 is an exploded perspective view of the optical adapter of FIG. 17; [Figure 22] 18 is a side view of the optical adapter of FIG. 17 except for the optical adapter cover; [Figure 23] Front view seen from the direction of arrow

[23] in Figure 22. [Figure 24] 18 is an external perspective view showing only a prism in the optical adapter of FIG. 17. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described below with reference to the illustrated embodiments. The drawings used in the following description are schematic, and the dimensional relationships and scales of the components may be different for each component in order to show each component at a size that allows it to be recognized on the drawing. Therefore, the present invention is not limited to the illustrated embodiments in terms of the number of components shown in the drawings, the shapes of the components, the size ratios of the components, the relative positional relationships of the components, and so on.

[0019] First, the overall configuration of an endoscope device to which the optical adapter of the first embodiment of the present invention can be applied as an optional device will be briefly described below with reference to Fig. 1. The optical adapter exemplified in this embodiment is a side-viewing optical adapter. Fig. 1 is a diagram showing the overall configuration of an endoscope device to which the optical adapter of the first embodiment of the present invention can be attached and used.

[0020] As shown in FIG. 1, the endoscope device 1 mainly includes an insertion section 2, a main body section 3, and an operation section 4.

[0021] The insertion section 2 is formed into an elongated, flexible tubular shape overall, and its base end is connected to the main body section 3. The insertion section 2 is configured by successively arranging a tip section 11, a bending section 12, and a flexible tubular section 13 in this order from the tip side.

[0022] The tip section 11 has a well-known basic configuration including a tip section main body 11a (see reference numeral 11a in FIG. 3), an observation window (not shown), an optical lens (see reference numeral 27b in FIG. 3) that constitutes an imaging optical system, an imaging element (see reference numeral 28 in FIG. 3) that is constituted by a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor), an illumination window, an illumination optical system, etc. The tip side of this tip section 11 is configured so that the side-viewing optical adapter 20 of this embodiment can be appropriately attached. In this case, the attachment and detachment direction of the side-viewing optical adapter 20 is the direction indicated by arrow X in FIG. 1. This attachment and detachment direction indicated by arrow X is a direction parallel to the insertion axis of the insertion section 2.

[0023] The bending section 12 is a tubular section that can actively perform bending motion in response to operation from the operation section 4. The bending section 12 is connected to the base end side of the tip section 11. The tip of the flexible tube section 13 is connected to the base end of the bending section 12. The base end of the flexible tube section 13 is connected to the main body section 3. Note that the basic configurations of the tip section 11, bending section 12, and flexible tube section 13 that make up the insertion section 2 are assumed to be similar to those of similar endoscopes known in the art, and detailed description thereof will be omitted.

[0024] The main body 3 incorporates a central processing unit (CPU), ROM, RAM, image processing unit, light source, large-capacity storage device, display device 14, etc. The base end of the insertion section 2 is connected to the main body 3. The display device 14 of the main body 3 displays various information, including images acquired by an imaging element 28 (see FIG. 3) of the tip section 11.

[0025] The operation unit 4 is connected to the main body 3 via a cable 15. The operation unit 4 has various operation members, such as a joystick and a push button. For example, the endoscope operator can bend the bending section 12 of the insertion section 2 in a desired direction by operating the joystick of the operation unit 4. In addition, the endoscope operator can display a still image on the display device 14 by pressing a predetermined push button.

[0026] An endoscope operator inserts the insertion portion 2 into an object to be inspected, such as a pipe, and positions the observation window of the tip portion 11 near the area to be inspected. This allows the image sensor 28 (see FIG. 3) of the tip portion 11 of the insertion portion 2 in the endoscope device 1 to display an image of the area to be inspected as an endoscopic image on the display device 14. At the same time, the endoscopic image can be recorded in a storage device as still image data or moving image data.

[0027] In the endoscopic device 1 shown in FIG. 1, a configuration in which the insertion section 2 and the main body section 3 are integrally formed is illustrated. However, this configuration is not limiting, and for example, the insertion section 2 and the main body section 3 may be configured to be detachable using a connector or the like. Furthermore, an endoscopic device of the type in which the insertion section 2 and the main body section 3 are separable may be configured as an endoscope in which the insertion section 2 and the operation section 4 are integrated, as a configuration different from the configuration illustrated in FIG. 1. In this case, the endoscope may be configured to be detachable from a main body section having a display device. Furthermore, the endoscopic device may be of a type in which the insertion section 2, operation section 4, and display device 14 are integrated into an endoscope and the main end section.

[0028] Next, the configuration of an optical adapter according to a first embodiment of the present invention will be described below with reference to FIGS. 2 to 9. FIG. 2 is a perspective view showing the appearance of the optical adapter according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view taken along the plane indicated by the arrow [3] in FIG. 2. Note that FIGS. 2 and 3 show a state in which the optical adapter (side-viewing optical adapter) of this embodiment, which is for side viewing, is attached to the tip of the insertion section 2. FIG. 4 is a cross-sectional view taken along the line [4]-[4] in FIG. 3. FIG. 5 is an exploded perspective view of the side-viewing optical adapter of FIG. 2 with the side-viewing optical adapter cover removed. FIG. 6 is an exploded perspective view of the side-viewing optical adapter of FIG. 2. Note that FIGS. 5 and 6 show only the side-viewing optical adapter of this embodiment. FIG. 7 is a side view of the configuration of the side-viewing optical adapter of FIG. 2 excluding the side-viewing optical adapter cover. FIG. 8 is a front view seen from the direction of the arrow [8] in FIG. 7. FIG. 9 is an external perspective view showing only the prism of the side-viewing optical adapter of FIG. 2.

[0029] The side-viewing optical adapter 20 of the first embodiment of the present invention is an optical adapter configured to be detachable from the distal end portion 11 of the insertion section 2 of the endoscope device 1 shown in Fig. 1. This side-viewing optical adapter 20 is configured as an optical adapter particularly for ensuring a lateral field of view.

[0030] 2 and the like, the virtual line (two-dot chain line) indicated by the symbol X will be referred to as the insertion axis of the side-viewing optical adapter 20. This insertion axis X is the central axis of the side-viewing optical adapter 20.

[0031] As shown in the figure, the side-viewing optical adapter 20 of this embodiment is mainly composed of a tip cover 21 which is the side-viewing optical adapter cover, a prism 22, an adapter main body 23 which is the side-viewing optical adapter main body, a connecting member 24, and a holding member (described in detail later).

[0032] The tip cover 21 is provided at a location on the tip side of the side-viewing optical adapter 20. A prism 22 is disposed inside the tip cover 21. As a result, the tip cover 21 functions as a protective member that protects part of the outer surface of the prism 22.

[0033] The tip cover 21 is formed into a generally cylindrical shape as a whole. As shown in Figures 5 and 6, the tip surface 21a of the tip cover 21 is closed, and the base surface 21b is open. The tip cover 21 also has an opening 21c formed by cutting out a portion of the outer circumferential surface. This opening 21c is an opening that exposes a portion of the prism 22 (an incident surface 22a and a second side surface 22f, which will be described later) to the outside and allows the light beam from the subject to enter the inside of the prism 22. The base surface 21b of the tip cover 21 abuts against the abutment surface 23b of the adapter main body 23 when the side-viewing optical adapter 20 is in an assembled state. Therefore, the outer diameter of the tip cover 21 is formed to be generally the same as the outer diameter of the adapter main body 23.

[0034] Furthermore, a part of the tip cover 21 functions as a second holding member that holds a part of the prism 22. The second holding member has a partial area near the base end of the tip cover 21 and near the opening 21c as a second holding portion 21d (described in detail later; see FIG. 4, etc.).

[0035] The prism 22 is an optical element that changes the optical path of incident light from the side of the insertion axis X to an optical path that is directed in a direction substantially parallel to the insertion axis X. The prism 22 is held by a holding member (described in detail later) provided on the adapter body 23 and the tip cover 21.

[0036] 2 and other figures, the optical axis (dash-dotted line) of the optical path of light incident from the side is indicated by the symbol O1, and will be referred to as the first optical axis O1 in the following description. Furthermore, the optical axis (dash-dotted line) of the optical path that travels in a direction parallel to the insertion axis X after being changed by the prism 22 is indicated by the symbol O2, and will be referred to as the second optical axis O2 in the following description. This second optical axis O2 coincides with the optical axis of the optical lens 27b (see FIG. 3) that constitutes part of the imaging optical system provided in the distal end 11 of the insertion section 2. Furthermore, the second optical axis O2 is perpendicular to the imaging surface (see symbol Im in FIG. 3) of the imaging element 28 (see FIG. 3) and coincides with the approximate center point of the imaging element 28.

[0037] As shown in Fig. 8, the prism 22 is formed so that its projected shape when viewed from the insertion axis X direction is polygonal. In this case, the polygonal shape has n=4 (n is a natural number), where n is the number of corners. In this embodiment, the case where n=8, i.e., an octagonal shape, is illustrated.

[0038] The prism 22 is a polyhedron. Therefore, in the following description, each face constituting the prism 22 will be assigned a reference symbol. In this case, a portion of a portion that is assigned a reference symbol and described as a specific "face" corresponds to one "side" of the polygonal shape when viewed from the insertion axis X direction. Specifically, for example, in FIG. 8, one specific side 22a of the polygonal shape when the prism 22 is viewed from the insertion axis X direction is part of the entrance surface 22a, which is one specific face of the prism 22. In this case, the specific side 22a is referred to as the entrance side. In this case, since the entrance side 22a is part of the entrance surface, the entrance side and the entrance surface will be referred to by the same reference symbol 22a.

[0039] The configuration of the prism 22 applied to the side-viewing optical adapter 20 of this embodiment will be described in detail below. As shown in FIGS. 4, 7 to 9, etc., the prism 22 has an incident surface 22a onto which observation light from the subject is incident. This incident surface 22a is arranged facing laterally with respect to the direction of the insertion axis X when the prism 22 is assembled to the side-viewing optical adapter 20. The optical axis O1 is perpendicular to this incident surface 22a and passes through approximately the center of the incident surface 22a. Note that, although the planar shape of the incident surface 22a is illustrated as being approximately rectangular in this embodiment, it is not limited to this.

[0040] The prism 22 has an opposite surface 22b that faces the incident surface 22a across the insertion axis X. In this embodiment, the planar shape of the incident surface 22a is illustrated as being substantially rectangular, but is not limited thereto. The incident surface 22a and the opposite surface 22b are formed parallel to each other. As shown in FIG. 4, the length W1 of the incident surface 22a in the width direction (the horizontal direction perpendicular to the insertion axis X) is longer than the length W2 of the opposite surface 22b in the width direction (same as above) (W1>W2).

[0041] Prism 22 also has four inclined surfaces connecting the four peripheral edges of incident surface 22a to the four peripheral edges of opposing surface 22b, respectively. Of these, two inclined surfaces connecting two side peripheral edges along insertion axis X among the four peripheral edges of incident surface 22a to the corresponding two side peripheral edges of opposing surface 22b are referred to as side inclined surfaces 22c (see FIGS. 4 and 7 to 9).

[0042] Furthermore, two inclined surfaces connecting two of the four peripheral edges of the incident surface 22a that are perpendicular to the insertion axis X to the corresponding two peripheral edges of the opposing surface 22b are referred to as the reflecting surface 22d and the exit surface 22g, respectively (see FIG. 9, etc.). Here, the reflecting surface 22d is a surface that reflects the observation light incident from the incident surface 22a. The exit surface 22g is a surface from which the observation light reflected by the reflecting surface 22d is emitted to the outside of the prism 22. In this embodiment, the planar shapes of the two side inclined surfaces 22c, the reflecting surface 22d, and the exit surface 22g are illustrated as being substantially rectangular, but are not limited thereto.

[0043] As shown in Fig. 8, in the polygonal shape of prism 22 when viewed from the direction of insertion axis X, incident side 22a and opposite side 22b are parallel to each other. Incident side 22a is longer than opposite side 22b (W1>W2). In this case, opposite side 22b is located within a region facing incident side 22a. Two lateral oblique sides 22c connecting each end of incident side 22a and each end of opposite side 22b are inclined downward in Fig. 8 so as to approach each other.

[0044] 8, the prism 22 has two first side edges 22e that are not parallel to the incident side 22a, the opposite side 22b, and the two side hypotenuses 22c. A straight line extending from each of the two first side edges 22e intersects with each of the two side hypotenuses 22c. Therefore, the first side edges 22e abut the side hypotenuses 22c.

[0045] Furthermore, as shown in Fig. 8, the prism 22 has an incident side 22a, an opposite side 22b, two lateral oblique sides 22c, and two second side sides 22f that are not parallel to the two first side sides 22e. Lines extending from the two second side sides 22f intersect with the two first side sides 22e and the incident side 22a, respectively. Therefore, the second side sides 22f abut against the first side sides 22e and the incident side 22a. When the prism 22 is assembled in the side-viewing optical adapter 20, the two second side sides 22f and the incident surface 22a are exposed to the outside through the opening 21c of the tip cover 21.

[0046] As described above, the prism 22 is held by holding members provided on the adapter body 23 and the tip cover 21. That is, as shown in Fig. 4 and other figures, at least a portion of each of the two side oblique sides (side slopes) 22c of the prism 22 is held by the first holding portion 23a (first holding member) of the adapter body 23. In this case, the side oblique sides 22c of the prism 22 and the first holding portion 23a are fixed together with an adhesive or the like (not shown).

[0047] When tip cover 21 is assembled and fixed to adapter main body 23 to which prism 22 is adhesively fixed, gap 23x (see FIG. 4) is formed between the outer surface of first holding portion 23a and the inner surface of tip cover 21. Because the base end portion of tip cover 21 and adapter main body 23 are joined by means such as laser welding, gap 23x is not filled with adhesive. By providing a space in gap 23x, even if an impact is applied to tip cover 21 from the outside, the external force is not transmitted to the contents contained in tip cover 21, resulting in a structure that is even more resistant to damage or deformation due to external forces.

[0048] Furthermore, at least a portion of the first side edge (first side surface) 22e of the prism 22 is held by the second holding portion 21d (second holding member) of the tip cover 21. In this case, a gap is formed between the first side edge 22e and the second holding portion 21d, and this gap is filled with adhesive. The first side edge 22e and the second holding portion 21d are then fixed watertightly by the adhesive. The adhesive serves to maintain watertightness and absorb shock, and also absorbs external force when the tip cover 21 is subjected to external force.

[0049] Furthermore, the second optical axis O2 after being reflected by the reflecting surface 22d of the prism 22 is disposed at a position offset toward the opposite side 22b on the opposite side of the insertion axis X from the incident surface 22a. For example, in Fig. 8, the second optical axis O2 is disposed at a position offset by the amount indicated by the symbol D toward the opposite side 22b from the insertion axis X (the central axis of the side-viewing optical adapter 20).

[0050] As shown in FIG. 8, when the distance between the entrance side 22a and the opposite side 22b in the polygonal shape when viewed from the insertion axis X direction is defined as a prism height h1, and the perpendicular line extending from the end point of the side oblique side 22c to the opposite side is defined as a hypotenuse height h2, the prism 22 satisfies the following conditional formula (1): h1<2h2 …… (1) By satisfying this conditional expression, it is possible to ensure an appropriate thickness of the first holding portion 23a, and it is possible to maintain sufficient strength for holding the prism.

[0051] 3 and other figures, adapter body 23 is configured to include optical lens 27a that constitutes part of the imaging optical system, illumination opening 25, illumination light guide path 26, etc. Note that the internal configuration of adapter body 23 is assumed to be a well-known configuration used in conventional optical adapters, etc., and detailed description thereof will be omitted.

[0052] The adapter body 23 is also formed with first holding portions 23a. The first holding portions 23a are two arm-shaped portions that protrude forward from both side surfaces of the adapter body 23. More specifically, the first holding portions 23a protrude forward from positions near the outer peripheral edge of the adapter body 23 in a direction substantially parallel to the insertion axis X. The first holding portions 23a are provided at positions that face each other across the insertion axis X. The two first holding portions 23a are part of holding members that respectively hold the two side inclined surfaces 22c of the prism 22. In other words, the two first holding portions 23a hold the prism 22 from both side surfaces.

[0053] As shown in FIG. 8, the intersection C1 between a straight line A extending from the incident side 22a and a straight line B extending from the lateral oblique side 22c does not abut on the first holding portion 23a.

[0054] The holding member is a member that holds the prism 22. The holding member has a first holding member and a second holding member that is separate from the first holding member. The first holding member is the side-viewing optical adapter main body, and more specifically, the first holding portion 23a of the adapter main body 23. The second holding member is the side-viewing optical adapter cover, and more specifically, the second holding portion 21d of the tip cover 21.

[0055] The connecting member 24 is a member for connecting the adapter main body 23 and the tip of the insertion section 2. The connecting member 24 is formed in a substantially cylindrical shape with both axial ends open. Note that the means for connecting the connecting member 24 and the tip of the insertion section 2 is assumed to apply known technology employed in conventional optical adapters, etc., and detailed illustrations and explanations thereof will be omitted.

[0056] In the side-viewing optical adapter 20 of this embodiment configured as described above, the incident light beam L1 (see dotted line L1 in FIGS. 2, 3, and 8) incident on the incident surface 22a is reflected by the reflecting surface 22d and its optical path is changed. Here, the trapezoidal dotted area indicated by the symbol R1 in FIG. 8 indicates the area of reflected light reflected by the reflecting surface 22d. Note that this dotted area R1 is the area of light that enters the effective area of the imaging element, and in reality, the light itself also enters reflecting surfaces other than the dotted area R1.

[0057] The reflected light beam L2 (see dotted line L2 in FIGS. 3 and 8) reflected by the reflecting surface 22d passes through the optical lens 27a. When the side-viewing optical adapter 20 is attached to the tip of the insertion section 2 (see FIG. 3), the reflected light beam L2 passes through the optical lens 27a, and then further passes through the optical lens 27b at the tip 11 of the insertion section 2, and is incident on the imaging surface of the imaging element 28. As a result, an optical image of the subject is formed on the imaging surface of the imaging element 28. Here, the rectangular dotted line area indicated by the symbol Im in FIG. 8 indicates the imaging area on the imaging surface of the imaging element 28 (see also the symbol Im in FIG. 3).

[0058] As described above, according to the first embodiment, the side-viewing optical adapter 20 has the prism 22 and a holding member.

[0059] The prism 22 is formed so that its projected shape when viewed from the insertion axis X direction of the insertion portion 2 is polygonal (number of angles n≧4; n is a natural number). The polygonal shape of the prism 22 has an incident side 22a, an opposite side 22b facing the incident side 22a across the insertion axis X, and two lateral oblique sides 22c connecting the incident side 22a and the opposite side 22b. The incident side 22a and the opposite side 22b are parallel. The incident side 22a is formed longer than the opposite side 22b (W1>W2).

[0060] First holding portion 23a, which is one of the holding members, holds at least a portion of each of two side oblique sides 22c of prism 22. At this time, intersection C1 between straight line A extending from incident side 22a and straight line B extending from each of two side oblique sides 22c does not abut on first holding portion 23a. In other words, first holding portion 23a holds a portion of the middle of each of two side oblique sides 22c of prism 22.

[0061] Furthermore, the holding member has a second holding portion 21d separate from the first holding portion 23a. Accordingly, the prism 22 has a first side edge 22e that is not parallel to the incident side 22a, the opposite side 22b, and the lateral oblique side 22c. The second holding portion 21d holds at least a part of the first side edge 22e.

[0062] Furthermore, the prism 22 has a second side 22f that is not parallel to the incident side 22a, the opposite side 22b, the lateral oblique side 22c, and the first side 22e. The second side 22f, together with the incident surface 22a, is exposed to the outside of the side-viewing optical adapter 20.

[0063] In other words, the prism 22 has an incident side 22a, an opposite side 22b, and two side oblique sides 22c in its projected shape when viewed from the insertion axis X direction of the insertion portion 2, and the incident side 22a and the opposite side 22b are parallel, with the incident side 22a being longer than the opposite side 22b. Therefore, the shape is, for example, approximately trapezoidal. The prism 22 having an approximately trapezoidal projected shape is configured so that the middle portions of the side oblique sides 22c are held by the first holding portion 23a.

[0064] In this case, the prism 22 in this embodiment has side slopes 22c formed by partially removing an unused area where the effective light beam incident on the imaging element does not pass in the conventional triangular prism 22. With this configuration, the prism 22 is formed so that the projected shape when viewed from the insertion axis X direction is polygonal (in this embodiment, an octagonal shape that is approximately trapezoidal).

[0065] A first holding portion 23a that holds at least a portion of the side oblique side 22c is provided on the adapter body 23. This first holding portion 23a is provided at an intersection C1 between a straight line B extending from the side oblique side 22c and a straight line A extending from the incident side 22a, i.e., at a position that does not abut on a lateral region of the incident surface 22a. Furthermore, the optical axis (second optical axis O2) of the reflected light from the reflecting surface 22d of the prism 22 is positioned at a position offset by the symbol D in FIG. 8 toward the opposite side 22b on the opposite side from the incident surface 22a across the insertion axis X.

[0066] In other words, the prism 22 has a lateral oblique side 22c formed thereon, and the optical axis (second optical axis O2) of the reflected light from the reflecting surface 22d is positioned at a position biased toward the opposite side 22b on the opposite side of the insertion axis X from the incident surface 22a.

[0067] In the side-viewing optical adapter 20 of this embodiment, which is configured by devising the shape and arrangement of the prism 22 in this way, it is possible to enlarge the entrance surface 22a of the prism 22 (widen the angle of view) without increasing the outer diameter of the adapter. Conventionally, when an attempt was made to shift the second optical axis O2 toward the opposite side 22b opposite the entrance surface 22a in order to enlarge the entrance surface 22a of the prism 22, the size of the prism made it impossible to ensure the thickness of the first holding portion 23a, resulting in a decrease in holding performance. While attempting to simultaneously ensure holding performance required an increase in the outer diameter of the adapter, this configuration allows the side-viewing optical adapter 20 to maintain holding performance and achieve a wide angle of view while maintaining the outer diameter of the adapter.

[0068] Furthermore, prism 22 is held and adhesively fixed by first holding portion 23a of adapter body 23. When tip cover 21 is assembled into adapter body 23 to which prism 22 is adhesively fixed, gap 23x (see FIG. 4) is formed between the outer surface of first holding portion 23a and the inner surface of tip cover 21. Because the base end portion of tip cover 21 and adapter body 23 are joined by means such as laser welding, no adhesive is filled in gap 23x.

[0069] With this configuration in which the adapter body 23 holds the prism 22, even if an unintended external force is applied to the tip cover 21, for example, when the side-viewing optical adapter 20 is dropped, the external force will not affect the prism 22. In this case, even if the tip cover 21 is deformed, the gap 23x prevents the first holding portion 23a from deforming. This not only prevents damage to the prism 22, but also prevents the holding position of the prism 22 from being affected. This allows the fixed position of the prism 22 to be maintained, eliminating the risk of optical axis misalignment. This prevents distortion in the imaging results and ensures consistently good imaging results.

[0070] In addition, since the lateral area of the entrance surface 22a of the prism 22 does not come into contact with the aforementioned intersection C1, the area for fixing the prism 22 from the side (as described in Patent Document 1) can be omitted and used to expand the entrance surface, thereby expanding the angle of view.

[0071] Furthermore, second holding portion 21d of tip cover 21 is bonded and fixed by adhesive that fills the gap between second holding portion 21d and first side edge 22e, which is a region different from side slope 22c of prism 22. Watertightness is ensured by the configuration in which second holding portion 21d and first side edge 22e are bonded and fixed.

[0072] In the side-viewing optical adapter 20 of the first embodiment described above, the first side edge 22e is provided, and the second holding portion 21d of the tip cover 21 is adhesively fixed to this first side edge 22e. However, this configuration is not necessarily required.

[0073] For example, as shown in Fig. 10, the prism 22A may have a square shape (projected shape when viewed from the insertion axis X direction) with n = 4. Here, Fig. 10 is a diagram showing a first modified example of the prism shape. Note that Fig. 10 is a cross-sectional view of the first modified example, corresponding to Fig. 4. This first modified example is an example in which the first side edge 22e of the prism 22 in the first embodiment described above is omitted.

[0074] Even with the configuration of the first modified example shown in Figure 10 (i.e., a configuration in which the first side edge 22e of the prism 22 in the first embodiment described above is omitted), it is possible to achieve a wide angle of view while maintaining the outer diameter dimension of the adapter, and the fixed position of the prism 22A can be maintained, eliminating the risk of optical axis misalignment, etc.

[0075] Furthermore, the side-viewing optical adapter 20 of the first embodiment described above is further provided with a second side edge 22f, and this second side edge 22f, together with the incident surface 22a, is configured to be exposed to the outside through the opening 21c of the tip cover 21. However, this configuration is not necessarily required.

[0076] Therefore, for example, the second side 22f of the prism 22 in the first embodiment described above can be omitted. However, even in this case, the entrance surface 22a must be configured to be exposed to the outside through the opening 21c of the tip cover 21.

[0077] For example, as shown in Fig. 11, the prism 22B may have a hexagonal shape (projected shape when viewed from the insertion axis X direction) with n=6. Fig. 11 is a diagram showing a second modified example of the prism shape. Fig. 11 is a cross-sectional view of the second modified example, corresponding to the cross-section of Fig. 4.

[0078] In this way, even with the configuration of the second modified example shown in Figure 11 (i.e., a configuration in which the second side edge 22f of the prism 22 in the first embodiment described above is omitted), it is possible to achieve a wide angle of view while maintaining the outer diameter dimension of the adapter, and the fixed position of the prism 22B can be maintained, eliminating the risk of optical axis misalignment, etc.

[0079] Next, a side-viewing optical adapter according to a second embodiment of the present invention will be described. The side-viewing optical adapter of this embodiment basically has a configuration substantially similar to that of the first embodiment described above. In this embodiment, the configurations of the first holding portion (adapter main body side) and the second holding portion (tip cover side) as holding members are different. Therefore, when describing the configuration of this embodiment, the same components as those of the first embodiment described above will be assigned the same reference numerals and their description will be omitted, and only the different components will be described below.

[0080] 12 to 15 are diagrams showing a side-viewing optical adapter according to a second embodiment of the present invention. Of these, Fig. 12 is a perspective view showing the appearance of the optical adapter according to the second embodiment of the present invention. Fig. 13 is an exploded perspective view of the side-viewing optical adapter of Fig. 12. Fig. 14 is a perspective view showing the configuration of the side-viewing optical adapter of Fig. 12 with the side-viewing optical adapter cover removed. Fig. 15 is a front view seen from the direction of arrow

[15] in Fig. 14.

[0081] Similar to the side-viewing optical adapter 20 of the first embodiment described above, the side-viewing optical adapter 20C of this embodiment is mainly composed of a tip cover 21C which is a side-viewing optical adapter cover, a prism 22, an adapter main body 23C which is a side-viewing optical adapter main body, a connecting member 24, and a holding member. Of these, the configurations of the tip cover 21C, the adapter main body 23C, and the holding member differ from those of the first embodiment described above.

[0082] The tip cover 21C is similar to the first embodiment in that it is formed in a generally cylindrical shape as a whole. As shown in Fig. 13 etc., the tip cover 21C in this embodiment is similar to the first embodiment in that it has a closed tip surface 21a, an open base end surface 21Cb, and an opening 21c formed by cutting out a portion of the outer circumferential surface.

[0083] In addition, the tip cover 21C in this embodiment has two second holding portions 21Cd. The second holding portions 21Cd are a pair of arm-shaped portions extending from the base end surface 21Cb in the direction of the insertion axis X. The second holding portions 21Cd are respectively arranged in opposing positions near both side surfaces of the tip cover 21C across the insertion axis X.

[0084] When the side-viewing optical adapter 20C is assembled, the end faces of the two second holding portions 21Cd abut against the abutment surfaces 23Cd of the adapter main body 23C. Therefore, the outer diameter of the tip cover 21 is formed to be approximately the same as the outer diameter of the adapter main body 23C. At this time, the end faces of 21Cd and the abutment surfaces 23Cd are adhesively fixed to each other with, for example, an adhesive. Note that laser welding or the like may be used instead of adhesive.

[0085] At this time, although not shown, the two second holding portions 21Cd are adhered and fixed by filling the gap between them and the first side edges 22e with adhesive. This configuration ensures watertightness between the second holding portions 21Cd and the first side edges 22e.

[0086] Furthermore, when the side-viewing optical adapter 20C is assembled, the base end surface 21Cb of the tip cover 21C abuts against the tip surface 23Cb of the adapter main body 23C. Therefore, the outer diameter of the tip cover 21 is formed to be approximately the same as the outer diameter of the adapter main body 23C. At this time, the base end surface 21Cb of the tip cover 21C and the tip surface 23Cb of the adapter main body 23C are adhesively fixed to each other using, for example, an adhesive. Note that laser welding or the like may be used instead of an adhesive.

[0087] Similar to the first embodiment, the adapter body 23C is configured to include an optical lens (not shown) that constitutes part of the imaging optical system, an illumination opening 25, an illumination light guide path (not shown), etc. Also in this embodiment, the internal configuration of the adapter body 23C itself is assumed to be a well-known configuration employed in conventional optical adapters, etc., and a detailed description thereof will be omitted.

[0088] A first holding portion 23Ca is formed on the adapter main body 23C. In this embodiment, the first holding portion 23Ca has portions that cover and hold the two side inclined surfaces 22c of the prism 22, respectively, and a portion that covers the opposite side 22b, and these portions are formed continuously. The first holding portion 23Ca is formed to protrude forward in the insertion axis X direction from the outer peripheral edge portion of the adapter main body 23C. The first holding portion 23Ca is formed to cover approximately half of the outer periphery on the tip side of the adapter main body 23C. In other words, the first holding portion 23Ca is formed in a form in which both left and right side surfaces are connected.

[0089] In this case, the intersection (C1) of the straight line (A) extending from the incident side 22a and the straight lines (B) extending from each of the two lateral oblique sides 22c does not abut the first holding portion 23Ca, as in the first embodiment described above.

[0090] With this configuration, the prism 22 in the side-viewing optical adapter 20C of this embodiment is held and adhesively fixed by the first holding portion 23Ca of the adapter main body 23C. In this case, the first holding portion 23Ca is adhesively fixed not only to the lateral oblique side 22c of the prism 22 but also to the opposite side 22b.

[0091] When the tip cover 21C is assembled into the adapter main body 23C to which the prism 22 is adhered, the tip surface 23Cb of the first holding portion 23Ca of the adapter main body 23C abuts against and is adhered to the base end surface 21Cb of the tip cover 21C. At the same time, the end surface of the second holding portion 21Cd of the tip cover 21C abuts against and is adhered to the abutment surface 23Cd of the adapter main body 23C.

[0092] The holding member is a member that holds the prism 22. The holding member has a first holding member and a second holding member that is separate from the first holding member. The first holding member is the side-viewing optical adapter main body, more specifically, the first holding portion 23Ca of the adapter main body 23C. The second holding member is the side-viewing optical adapter cover, more specifically, the second holding portion 21Cd of the tip cover 21C.

[0093] The configurations of the prism 22 and the connecting member 24 are exactly the same as those of the first embodiment described above. The other configurations are the same as those of the first embodiment described above.

[0094] The side-viewing optical adapter 20C of the second embodiment configured as above can also provide the same functions and effects as those of the first embodiment described above.

[0095] In the first embodiment described above, each side of the prism 22, such as the entrance side and side sides, may be rounded as long as it does not affect the design. In other words, the projected shape as viewed from the insertion axis direction of the endoscope insertion portion does not necessarily have to be a straight line. Furthermore, the intersections of each side do not necessarily have to be sharp, and may be chamfered. In this case, too, the intersections of the straight lines extending from each side can be considered as the vertices of the projected shape.

[0096] In the first embodiment described above, the projected shape of the prism 22 is mainly an octagon where n = 8. However, the projected shape of the prism 22 is not limited to this as long as n ≥ 4 (n is a natural number). For example, the example shown in FIG. 16 shows a case where n = 7, i.e., the projected shape of the prism 22D is a heptagon. Here, FIG. 16 is a diagram showing a modified prism shape of the second embodiment. Note that FIG. 16 is a cross-sectional view of this modified example, corresponding to the cross-section of FIG. 4. As shown in FIG. 16, when n is an odd number, there may be two or more opposite sides to the incident side. Even in this case, a wide angle of view can be achieved while maintaining the outer diameter of the adapter, and the fixed position of the prism 22D can be maintained, eliminating the risk of optical axis misalignment.

[0097] In each of the above-described embodiments, an optical adapter configured to be detachable from the tip 11 of the insertion portion of the endoscope is exemplified. However, apart from the configuration in which the optical adapter is detachable from the tip 11, the configuration of the present invention can also be applied to an endoscope in which the optical system built into the optical adapter is integrally configured at the tip of the insertion portion.

[0098] Specifically, for example, a configuration is conceivable in which the prism, first holding member, second holding member, etc. of each of the above-described embodiments are built into the tip portion 11 of the endoscope as an imaging optical system. Furthermore, in this configuration, the insertion portion 2 may be configured to be detachable from the main body portion 3.

[0099] In each of the above-described embodiments, examples have been shown in which the present invention is applied to a side-viewing optical adapter or a side-viewing endoscope to ensure a side field of view, but the configuration of the present invention is not limited to the above-described form (for side viewing).

[0100] The configuration of the present invention can be applied to, for example, an optical adapter for oblique viewing or an endoscope for oblique viewing, which ensures an oblique field of view.

[0101] Figures 17 to 24 are diagrams showing an optical adapter according to a third embodiment of the present invention, which correspond to Figures 2 to 9 of the first embodiment described above, respectively.

[0102] 17 is a perspective view showing the appearance of an optical adapter according to a third embodiment of the present invention (corresponding to FIG. 2). FIG. 18 is a cross-sectional view taken along the plane indicated by the arrow

[18] in FIG. 17 (corresponding to FIG. 3). Note that FIGS. 17 and 18 show the side-viewing optical adapter of this embodiment attached to the tip of the insertion section 2.

[0103] FIG. 19 is a cross-sectional view taken along the line

[19] -

[19] in FIG. 18 (corresponding to FIG. 4). FIG. 20 is an exploded perspective view of the optical adapter in FIG. 17 with the optical adapter cover removed (corresponding to FIG. 5). FIG. 21 is an exploded perspective view of the optical adapter in FIG. 17 (corresponding to FIG. 6). Note that FIGS. 20 and 21 only show the side-viewing optical adapter of this embodiment. FIG. 22 is a side view of the configuration of the optical adapter in FIG. 17 excluding the optical adapter cover. FIG. 23 is a front view seen from the direction of arrow

[23] in FIG. 22. FIG. 24 is an external perspective view showing only the prism in the optical adapter in FIG. 17.

[0104] An optical adapter for oblique viewing 20E according to a third embodiment of the present invention is similar to the first embodiment described above in that it is an optical adapter configured to be detachable from the distal end portion 11 of the insertion section 2 of the endoscope device 1 shown in Fig. 1. The optical adapter for oblique viewing 20E according to this embodiment differs from the first embodiment described above in that it is configured as an optical adapter specifically for ensuring an oblique field of view. Therefore, in the following description of this embodiment, the same components as those in the first embodiment described above will be assigned the same reference numerals, and their description will be omitted, with only the differences being described in detail.

[0105] As shown in the figure, the side-view optical adapter 20E of this embodiment is mainly composed of a tip cover 21E, which is an optical adapter cover for oblique viewing, a prism 22E, an adapter main body 23, which is the side-view optical adapter main body, a connecting member 24, and a holding member.

[0106] The tip cover 21E basically has the same configuration as the tip cover 21 in the first embodiment described above, with only the shapes of the opening 21c and the second holding portion 21d being slightly different to match the shape of the prism 22E (see Figures 17 to 21, etc.).

[0107] The prism 22E is an optical element that changes the optical path of incident light from an oblique direction with respect to the insertion axis X to an optical path that is directed in a direction substantially parallel to the insertion axis X. The prism 22E is held by holding members provided on the adapter body 23 and the tip cover 21.

[0108] Prism 22E is similar to prism 22 in the first embodiment described above in that it is a polyhedron. In prism 22E in this embodiment, incident surface 22a onto which observation light from the subject is incident is arranged facing sideways and inclined forward with respect to the insertion axis X direction when prism 22E is assembled into optical adapter for oblique viewing 20E. Other surfaces of prism 22E are substantially similar to those of prism 22 in the first embodiment described above. Furthermore, two side inclined surfaces 22c of prism 22E are sandwiched by first holding portions 23a of adapter main body 23, thereby holding prism 22E in adapter main body 23. Other configurations are substantially similar to those of the first embodiment described above.

[0109] The third embodiment configured in this manner can also achieve the same effects as the above-mentioned embodiments. That is, the present invention can be applied in exactly the same way to an optical adapter for oblique viewing, and can achieve the same effects. Furthermore, the configuration of this embodiment can also be applied to an oblique-viewing endoscope in which the optical system built into the oblique-viewing optical adapter of the third embodiment described above is integrally configured at the tip of the insertion section.

[0110] The present invention is not limited to the above-described embodiments, and various modifications and applications can be made without departing from the spirit and scope of the invention. Furthermore, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining the disclosed multiple constituent elements. For example, if the problem to be solved by the invention can be solved and the effects of the invention can be obtained even if some constituent elements are deleted from all the constituent elements shown in one embodiment, the configuration from which these constituent elements are deleted can be extracted as the invention. Furthermore, constituent elements from different embodiments may be appropriately combined. The present invention is not limited by specific embodiments other than as limited by the appended claims. [Explanation of symbols]

[0111] 1...Endoscopic device 2...Insertion section 3...Main body 4...Operation unit 11...Tip 11a...Tip body 12...Bend 13...Flexible tube section 14...Display device 15...Cable 20, 20C...Side-viewing optical adapter 20E...Optical adapter for strabismus 21, 21C, 21D, 21E...Tip cover 21a…Tip surface 21b,21Cb…Proximal surface 21c…Aperture 21d, 21Cd…Second holding part 22, 22A, 22B, 22D, 22E...Prism 22a...incident surface, incident side 22b…opposite side 22c...Side slope, side oblique edge 22d…Reflective surface 22g…Emission surface 23, 23C...Adapter body 23a, 23Ca…1st holding part 23b…Abutting surface 23Cb…Tip surface 23Cd…Contact surface 23x…gap 24...Connecting member 25...Lighting opening 26...Light guide 27a, 27b...Optical lenses 28...Image sensor

Claims

1. An optical adapter that can be attached and detached to the tip of an endoscope insertion part, a prism having an incident surface onto which observation light from the subject is incident; a holding member for holding the prism; and the prism is formed so that its projected shape when viewed in the insertion axis direction of the endoscope insertion portion is polygonal (number of corners n≧4; n is a natural number); the polygonal shape has an incident side that is a part of the incident surface, one or more opposite sides that face the incident side across the insertion axis, and at least two or more oblique sides that connect the incident side and the opposite side, The incident side is formed longer than the opposite side, the holding member holds at least a portion of each of the hypotenuses of the prism; The intersection of the straight line extending from the incident side and each straight line extending from each of the at least two or more oblique sides does not come into contact with the holding member. An optical adapter characterized by:

2. Further comprising a second holding member different from the holding member, the prism has a first side that is not parallel to the incident side, the opposite side, and the hypotenuse, and the first side is formed in contact with the hypotenuse; The second holding member holds at least a portion of the first side edge.

2. The optical adapter according to claim 1.

3. the prism further has a second side edge that is not parallel to the incident side, the opposite side, the hypotenuse, and the first side edge, and the second side edge is formed in contact with the first side edge and the incident side, The second side is exposed to the outside of the optical adapter.

3. The optical adapter according to claim 2.

4. the prism has a reflecting surface that reflects the observation light incident on the incident surface, The optical axis of the light reflected by the reflecting surface is formed at a position offset toward the opposite side opposite the incident surface across the insertion axis.

2. The optical adapter according to claim 1.

5. An optical adapter cover that is a protective member that protects at least a part of the outer surface of the prism, a gap is provided between the holding member and the inner surface of the optical adapter cover; 2. The optical adapter according to claim 1.

6. When the distance between the incident side and the opposite side is defined as a prism height h1 and the perpendicular line extending from the end point of the hypotenuse to the opposite side is defined as a hypotenuse height h2, the prism satisfies the conditional formula (1) h1<2h2... (1) fulfill 2. The optical adapter according to claim 1.

7. An optical adapter cover that is a protective member that protects at least a part of the outer surface of the prism, The holding member is formed on the optical adapter body, The second holding member is formed on the optical adapter cover.

2. The optical adapter according to claim 1.

8. The prism has a first side edge that is not parallel to each of the incident side, the opposite side, and the hypotenuse, There is a gap between the second holding member and the first side edge.

8. The optical adapter according to claim 7.

9. The incident surface is exposed to the outside of the optical adapter.

2. The optical adapter according to claim 1.

10. A first holding member formed on the optical adapter body; an optical adapter cover that is a protective member that protects at least a part of the outer surface of the prism, The left and right sides of the holding member are connected and are flush with the outer surface of the optical adapter cover. The optical adapter cover and the first holding member are butted against each other, and the butted surfaces are fixed by adhesive or laser welding.

2. The optical adapter according to claim 1.

11. The incident side and the opposite side are parallel 2. The optical adapter according to claim 1.

12. The optical adapter is for side viewing or oblique viewing.

2. The optical adapter according to claim 1.

13. An endoscope used by attaching a detachable optical adapter to the distal end of an insertion section, the optical adapter includes a prism having an incident surface onto which observation light from a subject is incident, and a holding member that holds the prism; The prism has a polygonal projection shape (number of angles n≧4; n is a natural number) when viewed from the insertion axis direction of the insertion part of the endoscope, and the polygonal shape has an incident side that is a part of the incident surface, one or more opposite sides that face the incident side across the insertion axis, and at least two or more oblique sides that connect the incident side and the opposite side, and the incident side is formed longer than the opposite side, the holding member holds at least a portion of each of the hypotenuses of the prism; The intersection of the straight line extending from the incident side and the straight lines extending from each of the at least two or more oblique sides does not come into contact with the holding member. An endoscope characterized by:

14. An endoscope having an optical system at the tip of an insertion section, the optical system includes a prism having an incident surface onto which observation light from a subject is incident, and a holding member that holds the prism; The prism has a polygonal projection shape (number of angles n≧4; n is a natural number) when viewed from the insertion axis direction of the insertion part of the endoscope, and the polygonal shape has an incident side that is a part of the incident surface, one or more opposite sides that face the incident side across the insertion axis, and at least two or more oblique sides that connect the incident side and the opposite side, and the incident side is formed longer than the opposite side, the holding member holds at least a portion of each of the hypotenuses of the prism; The intersection of the straight line extending from the incident side and the straight lines extending from each of the at least two or more oblique sides does not come into contact with the holding member. An endoscope characterized by:

Images