Endoscopes and endoscope systems

Abstract

Provided is an endoscope capable of performing illumination with a wide distribution of illumination light and little light loss and uneven illumination. The insertion portion of the endoscope (20) has a camera unit (50) and a light guide (60). A front end cover (40) is arranged at the front end (30) of the insertion portion. Illumination light is emitted from the exit surface of the light guide. The front end cover (40) has a through portion for inserting and fixing the camera unit (50). The object side of the front end cover (40) is set as the first surface (41), the hand side is set as the second surface (42), and the outer peripheral portion is set as the side surface (43). The first surface (41) has a first plane and a curved surface, and the curved surface is located between the first plane and the side surface. The second surface (42) has an illumination area (42b) for incident illumination light, and at least a part of the illumination area (42b) is formed by a partial annular surface. The first specified cross section is a cross section that includes the central axis of the front end cover (40) and intersects the exit surface, and in at least one first specified cross section, the following conditional formula (1) is satisfied. 0≤hA / r≤0.5(1).

Description

Technical Field

[0001] The present invention relates to an endoscope and an endoscope system. Background Art

[0002] Patent Document 1 discloses an endoscope having a distal end cover. The distal end cover is attached to the distal end of the insertion portion and is made of a transparent material.

[0003] The objective optical system, light guide, imaging element, and front cover are arranged at the front end of the insertion portion. The light guide is located at two positions on the side of the objective optical system. The imaging element has an image capture range (image capture area).

[0004] The front cover has a first surface, a second surface, and a side surface. The first surface is located on the object side. The second surface is located on the hand side. The side surface is located on the outer periphery.

[0005] The first surface is formed by a flat surface and a curved surface. The curved surface is located between the flat surface and the side surface. By providing the curved surface, the insertion portion can be easily inserted into the body.

[0006] The second surface has a portion facing the light guide's exit surface. This portion is the illumination light diffuser. The illumination light emitted from the light guide's exit surface passes through the illumination light diffuser and then exits from the first surface of the front cover, thereby illuminating the field of view.

[0007] The field of view is the range of the object space that can be seen by an optical device. The field of view of an endoscope is determined by the focal length and distortion of the objective optical system and the image range of the imaging element.

[0008] The illumination light emitted from the illumination light diffuser is incident on both the flat and curved surfaces of the first surface. The curved surface of the first surface has positive refractive power. Therefore, the illumination light incident on the curved surface is refracted toward the center of the field of view. The illumination light refracted toward the center of the field of view is superimposed on the illumination light emitted from the flat surface on the object. As a result, the illumination light is intensified at specific locations within the field of view, causing uneven illumination.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-237790 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] In the endoscope of Patent Document 1, the refraction angle at the curved surface is large, and the angular distribution of illumination light emitted from the flat surface is different from that from the curved surface. Therefore, the illumination light at a specific angle becomes stronger, causing uneven illumination.

[0014] By making the illumination light diffusion portion a scattering surface, it is possible to reduce illumination unevenness. However, scattering causes light loss, thus reducing the amount of illumination light.

[0015] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an endoscope and an endoscope system capable of performing illumination with a wide distribution of illumination light and little light loss and illumination unevenness.

[0016] Solutions for solving problems

[0017] In order to solve the above problems and achieve the purpose, at least some embodiments of the present invention involve an endoscope as follows:

[0018] The insertion portion of the endoscope has an imaging unit and a light guide, and a front end cover is arranged at the front end of the insertion portion.

[0019] The illumination light is emitted from the light guide member exit surface,

[0020] The front cover has a through portion for inserting and fixing the camera unit.

[0021] When the object side of the front cover is defined as the first surface, the hand side of the front cover is defined as the second surface, and the outer peripheral portion of the front cover is defined as the side surface,

[0022] The first surface has a first plane and a curved surface,

[0023] The curved surface is located between the first plane and the side surface.

[0024] The second surface has an illumination area for incident illumination light,

[0025] At least a portion of the illumination area is formed by a partial annulus,

[0026] The first predetermined cross section is a cross section that includes the central axis of the front end cover and intersects the light guide output surface.

[0027] In at least one first predetermined cross section, the following conditional expression (1) is satisfied.

[0028] 0≤hA / r≤0.5 (1)

[0029] Here,

[0030] A local torus is a surface obtained by cutting off a portion of a torus.

[0031] A torus is the surface of a solid of revolution formed when a circle and a straight line that does not intersect the circle are present on a plane. The circle that is rotated is called a small circle.

[0032] hA is the distance between the first and second intersection points,

[0033] The first intersection point is the intersection point of a straight line passing through the center of the small circle and parallel to the central axis and the light guide's exit surface.

[0034] The second intersection point is the intersection point of the light rays passing through the boundary between the first plane and the curved surface and the light rays parallel to the central axis between the light guide member exit surface and the illumination area with the light guide member exit surface.

[0035] When the second intersection point is between the first intersection point and the side surface, the sign of the distance value is set to be positive.

[0036] r is the radius of the small circle.

[0037] An endoscope, wherein the insertion portion of the endoscope has a camera unit and a light guide, and a front end cover is arranged at the front end of the insertion portion.

[0038] The illumination light is emitted from the light guide member exit surface,

[0039] The front cover has a through portion for inserting and fixing the camera unit.

[0040] When the object side of the front cover is defined as the first surface, the hand side of the front cover is defined as the second surface, and the outer peripheral portion of the front cover is defined as the side surface,

[0041] The first surface has a first plane and a curved surface,

[0042] The curved surface is located between the first plane and the side surface.

[0043] The second surface has an illumination area for incident illumination light,

[0044] At least a portion of the illumination area is formed by a partial annulus,

[0045] The first predetermined cross section is a cross section that includes the central axis of the front end cover and intersects the light guide output surface.

[0046] In at least one first predetermined cross section, the following conditional expression (2) is satisfied.

[0047] 0≤(hA×n 2 ) / r≤1.36 (2)

[0048] Here,

[0049] A local torus is a surface obtained by cutting off a portion of a torus.

[0050] A torus is the surface of a solid of revolution formed when a circle and a straight line that does not intersect the circle are present on a plane. The circle that is rotated is called a small circle.

[0051] hA is the distance between the first and second intersection points,

[0052] The first intersection point is the intersection point of a straight line passing through the center of the small circle and parallel to the central axis and the light guide's exit surface.

[0053] The second intersection point is the intersection point of the light rays passing through the boundary between the first plane and the curved surface and the light rays parallel to the central axis between the light guide member exit surface and the illumination area with the light guide member exit surface.

[0054] When the second intersection point is between the first intersection point and the side surface, the sign of the distance value is set to be positive.

[0055] n is the refractive index of the material of the front cover at the e-line,

[0056] r is the radius of the small circle.

[0057] Furthermore, at least some embodiments of the present invention relate to an endoscope system having:

[0058] The endoscope mentioned above; and

[0059] Image processing device.

[0060] Effects of the Invention

[0061] According to the present invention, it is possible to provide an endoscope and an endoscope system capable of performing illumination with wide illumination light distribution and little light loss and illumination unevenness. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 1 and 2 are diagrams showing an endoscope and an endoscope system according to the present embodiment.

[0063] Figure 2 This is a diagram showing a first example of an endoscope having a basic structure.

[0064] Figure 3 is a diagram showing a torus.

[0065] Figure 4 This is a diagram showing a second example of an endoscope having a basic structure.

[0066] Figure 5 This is a diagram of the distal end of the endoscope viewed from the object side.

[0067] Figure 6 It is a cross-sectional view of the front end cover.

[0068] Figure 7 This is a diagram of the distal end of the endoscope viewed from the object side.

[0069] Figure 8 It is a cross-sectional view of the front end cover.

[0070] Figure 9 It is a cross-sectional view of the front end cover.

[0071] Figure 10 It is a cross-sectional view of the front end cover.

[0072] Figure 11 This is a diagram of the distal end of the endoscope viewed from the object side.

[0073] Figure 12 This is a diagram of the front end of the insertion portion and the front end cover.

[0074] Figure 13 It is a cross-sectional view of the front end cover.

[0075] Figure 14 This is a diagram of the distal end of the endoscope viewed from the object side.

[0076] Figure 15 It is a diagram showing the endoscope and light distribution of Example 1.

[0077] Figure 16 It is a diagram showing the endoscope and light distribution of Example 2.

[0078] Figure 17 It is a diagram showing the endoscope and light distribution of Example 3.

[0079] Figure 18 It is a diagram showing the endoscope and light distribution of Example 4.

[0080] Figure 19 This is a diagram showing the endoscope and light distribution of Example 5.

[0081] Figure 20 It is a diagram showing the endoscope and light distribution of Example 6.

[0082] Figure 21 This is a diagram showing the endoscope and light distribution of Example 7.

[0083] Figure 22 This is a diagram showing the endoscope and light distribution of Example 8. DETAILED DESCRIPTION

[0084] The reasons for adopting such a structure and the effects of the endoscope and the endoscope system according to the present embodiment will be described below.

[0085] In the following description, cross-sectional views and views of the distal end of the endoscope viewed from the object side are used. The cross-sectional views are views taken along a section including the central axis of the distal end cover.

[0086] Figure 1 1 is a diagram showing an endoscope and an endoscope system according to this embodiment. The endoscope is, for example, an electronic endoscope.

[0087] The endoscope system 1 is an observation system using an electronic endoscope 2. The endoscope system 1 includes the electronic endoscope 2 and a housing 3 having a camera control unit (CCU) and a light source function. A display unit 4 is connected to the housing 3.

[0088] The electronic endoscope 2 includes an insertion portion 6, an operating portion 5, a universal cable 7, and a connector 8. The insertion portion 6 is elongated and can be inserted into a patient's body cavity. Furthermore, the insertion portion 6 is formed of a flexible member. The observer can perform various operations using, for example, the angle knob provided on the operating portion 5. The universal cable 7 is connected to the housing 3 via the connector 8.

[0089] The universal cable 7 includes built-in signal cables and light guide cables for transmitting and receiving various signals. Examples of these signals include power supply voltage signals and CCD drive signals. These signals are transmitted from the housing 3 to the electronic endoscope 2. Another example of these signals is an image signal, which is transmitted from the electronic endoscope 2 to the housing 3.

[0090] Furthermore, peripheral devices such as a VTR tape recorder and a video printer (not shown) can be connected to the video processor in the housing 3. The video processor processes the image signal from the electronic endoscope 2. Based on the image signal, the display unit 4 displays an endoscopic image.

[0091] A distal end cover 9 is disposed at the distal end of the insertion portion of the electronic endoscope 2 .

[0092] The endoscope of this embodiment will be described using the endoscope of the first embodiment and the endoscope of the second embodiment. The endoscope of the first embodiment and the endoscope of the second embodiment have a basic structure.

[0093] The basic structure is that the insertion portion has a camera unit and a light guide. A front end cover is arranged at the front end of the insertion portion. Illumination light is emitted from the exit surface of the light guide. The front end cover has a through portion for inserting and fixing the camera unit. The object side of the front end cover is set as the first surface, the hand side of the front end cover is set as the second surface, and the outer peripheral portion of the front end cover is set as the side surface. The first surface has a first plane and a curved surface, and the curved surface is located between the first plane and the side surface. The second surface has an illumination area for incident illumination light, and at least a part of the illumination area is formed by a partial annular surface. The first specified cross section is a cross section that includes the central axis of the front end cover and intersects with the exit surface of the light guide.

[0094] An endoscope, for example, has an operating section and an insertion section. One end of the insertion section is located on the object side, while the other end is located on the operating section side. The operator performs various operations at the operating section. Thus, the operating section is positioned at the operator's hand. The hand side is the side where the operating section is located.

[0095] Figure 2This is a diagram showing a first example of the endoscope according to the present embodiment. Figure 2 (a) is a cross-sectional view of the front end of the insertion portion. Figure 2 (b) is a cross-sectional view of the front end cover.

[0096] like Figure 2 As shown in FIG. 2( a ), a distal end cover 40 is disposed at the distal end 30 of the insertion portion of the endoscope 20 . Furthermore, an outer tube 31 and a metal tube 32 are disposed at the distal end 30 , for example. The outer tube 31 and the metal tube 32 are in contact with the distal end cover 40 .

[0097] The imaging unit 50 and the light guide 60 are located at the insertion portion distal end 30. The imaging unit 50 includes an objective optical system 51 and an imaging element 52. The light guide 60 includes a light guide emission surface 61. Illumination light is emitted from the light guide emission surface 61.

[0098] The illumination light emitted from the light guide exit surface 61 enters the distal end cover 40. The distal end cover 40 is formed of a transparent material. For example, resin can be used as the transparent material. The illumination light entering the distal end cover 40 is refracted and transmitted through the distal end cover 40 before being emitted from the distal end cover 40.

[0099] In the endoscope 20, the light guide 60 is located side by side with the imaging unit 50. Thus, illumination light is irradiated onto the object from one direction.

[0100] like Figure 2 As shown in FIG. 1 ( b ), the front cover 40 has a first surface 41 , a second surface 42 , and a side surface 43 . The first surface 41 is the object-side surface of the front cover 40 . The second surface 42 is the hand-side surface. The side surface 43 is the outer peripheral surface of the front cover 40 .

[0101] A through hole 44 is formed in the front cover 40 . After the imaging unit 50 is inserted into the through hole 44 , the imaging unit 50 is fixed to the through hole 44 .

[0102] The first surface 41 has a first flat surface 41 a and a curved surface 41 b . The curved surface 41 b is located between the first flat surface 41 a and the side surface 43 .

[0103] The first plane 41a, the curved surface 41b, and the side surface 43 are formed so that the boundaries of the respective regions are smoothly connected. Arrow 45 indicates the position of the boundary between the first plane 41a and the curved surface 41b. Arrow 46 indicates the position of the boundary between the curved surface 41b and the side surface 43.

[0104] The central axis 47 is the central axis of the front cover 40 . The center of the through hole 44 is not located on the central axis 47 .

[0105] The second surface 42 of the front cover 40 has a non-illumination area 42a and an illumination area 42b. The non-illumination area 42a is a flat surface.

[0106] A recessed portion 48 is formed in the front end cover 40 at a position facing the light guide 60. The illumination region 42b is the bottom surface of the recessed portion 48, and the illumination light emitted from the light guide emission surface 61 enters the illumination region 42b.

[0107] Since the front end cover 40 is formed of a transparent material, the illumination light incident on the illumination region 42 b is refracted and transmitted therethrough and is emitted from the first surface 41 .

[0108] In the first example of the basic structure, at least a portion of the illumination area is a partial toroidal surface (hereinafter referred to as a "PT surface"). In the endoscope 20, the entire surface of the illumination area 42b is formed by the PT surface.

[0109] A PT plane is a surface obtained by cutting out a portion of a torus. A torus is the surface of a solid of revolution formed when a circle and a straight line that does not intersect the circle are present on a plane and the circle is rotated about the straight line. This rotated circle is called a small circle.

[0110] Figure 3 is a diagram showing a torus. Figure 3 (a) is a diagram showing a torus. Figure 3 (b) is a diagram showing the positions of the small circle and the central axis. Figure 3 (c) is a diagram showing arcs for forming the PT plane.

[0111] like Figure 3 As shown in (a) of FIG. 8 , the annular surface 70 is the surface of an annular solid 71 .

[0112] like Figure 3 As shown in (b), torus 70 is the surface of a rotating body formed when circle 72 and a straight line 73 that does not intersect circle 72 are present on a plane and circle 72 is rotated about straight line 73. This rotating circle 72 is referred to as a small circle. Rotating circle 72 moves circumference 74, and the movement of circumference 74 forms torus 70. Torus 70 is the trajectory of circle 74.

[0113] The PT surface is a surface obtained by cutting out a portion of the annular surface 70. The annular surface 70 is formed by moving the circumference 74. Thus, the PT surface is formed by moving a portion of the circumference 74.

[0114] Figure 3 (c) of FIG. 7 shows an arc 75. The arc 75 is a portion of the circumference 74. The PT plane is formed by rotating the arc 75 around the straight line 73.

[0115] Figure 4 It is a diagram showing a second example of the basic structure. Figure 4 (a) is a cross-sectional view of the front end of the insertion portion. Figure 4 (b) is a cross-sectional view of the front end cover.

[0116] like Figure 4 As shown in FIG. 8( a ), a distal end cover 100 is disposed at the distal end 90 of the insertion portion of the endoscope 80 . Also, an outer tube 91 and a metal tube 92 are disposed at the distal end 90 of the insertion portion. The outer tube 91 and the metal tube 92 are in contact with the distal end cover 100 .

[0117] The imaging unit 110 and the light guide 120 are located at the insertion portion front end 90. The imaging unit 110 includes an objective optical system 111 and an imaging element 112. The light guide 120 includes a light guide emission surface 121. Illumination light is emitted from the light guide emission surface 121.

[0118] The illumination light emitted from the light guide exit surface 121 enters the front end cover 100. The front end cover 100 is formed of a transparent material. For example, resin can be used as the transparent material. The illumination light entering the front end cover 100 is refracted and transmitted through the front end cover 100 before being emitted from the front end cover 100.

[0119] In the endoscope 80, the light guides 120 are located at two positions symmetrical to the imaging unit 110. Thus, illumination light is irradiated onto the object from two directions.

[0120] like Figure 4 As shown in FIG. 1 ( b ), the front cover 100 has a first surface 101 , a second surface 102 , and a side surface 103 . The first surface 101 is the object-facing surface of the front cover 100 . The second surface 102 is the hand-facing surface. The side surface 103 is the outer peripheral surface of the front cover 100 .

[0121] A through hole 104 is formed in the front cover 100 . After the imaging unit 110 is inserted into the through hole 104 , the imaging unit 110 is fixed to the through hole 104 .

[0122] The first surface 101 has a first flat surface 101 a and a curved surface 101 b . The curved surface 101 b is located between the first flat surface 101 a and the side surface 103 .

[0123] The first plane 101a, the curved surface 101b, and the side surface 103 are formed so that the boundaries of the respective regions are smoothly connected. Arrow 105 indicates the position of the boundary between the first plane 101a and the curved surface 101b. Arrow 106 indicates the position of the boundary between the curved surface 101b and the side surface 103.

[0124] The central axis 107 is the central axis of the front cover 100 . The center of the through hole 104 is located on the central axis 107 .

[0125] The second surface 102 of the front cover 100 has a non-illumination area 102a and an illumination area 102b. The non-illumination area 102a is a flat surface.

[0126] A recess 108 is formed in the front cover 100 at a position facing the light guide 120. The illumination region 102b is the bottom surface of the recess 108, and the illumination light emitted from the light guide emission surface 121 enters the illumination region 102b.

[0127] The front cover 100 is formed of a transparent material, so the illumination light incident on the illumination area 102 b is refracted and transmitted and then emitted from the first surface 101 .

[0128] In the second example of the basic structure, at least a portion of the illumination area is formed by a PT surface. In the endoscope 80, the entire surface of the illumination area 102b is formed by a PT surface.

[0129] Because the torus's cross-section is a small circle, it has a refractive power. Consequently, the PT surface also has a refractive power. By using the PT surface in at least a portion of the illumination area, the illumination light emitted from the light guide's exit surface can be refracted. This allows for a wider distribution of illumination light.

[0130] As described above, the endoscope of this embodiment includes an imaging unit. The imaging unit includes an imaging element and an objective optical system. The imaging element has a rectangular image capture range.

[0131] Because the image plane is rectangular within the image sensor's imageable range, the field of view is also roughly rectangular. Hereinafter, the direction of the diagonal line of the field of view within the range in which the image sensor can capture a subject image, i.e., the imageable range, is referred to as the "diagonal direction of the field of view," the direction of the long side of the imageable range is referred to as the "long side direction of the field of view," and the direction of the short side of the imageable range is referred to as the "short side direction of the field of view."

[0132] use Figure 5 The first predetermined cross section will be described. Figure 5 This is a diagram of the distal end of the endoscope viewed from the object side.

[0133] Figure 5 (a) is a diagram showing a first example of the position of the first predetermined cross section. Figure 5 (b) is a diagram showing a second example of the position of the first predetermined cross section. Figure 5 (c) is a diagram showing a third example of the position of the first predetermined cross section. Figure 5 (d) is a diagram showing a fourth example of the position of the first predetermined cross section.

[0134] The first predetermined cross section is a cross section that includes the central axis of the front cover and intersects the light guide exit surface. The light guide exit surface has a limited width. Therefore, there are multiple first predetermined cross sections.

[0135] The shape of the imageable range is a rectangle. The X axis is parallel to the long side of the imageable range, and the Y axis is parallel to the short side of the imageable range.

[0136] like Figure 5 As shown in FIG. 1 (a), when the insertion portion distal end 131 of the endoscope 130 is viewed from the object side, an imaging unit 132 and a light guide emission surface 133 are arranged at the insertion portion distal end 131. The endoscope 130 uses one light guide.

[0137] The imaging unit 132 includes an objective optical system and an imaging element. The imaging element has an image capture range 134. The center of the imaging unit 132 is offset in the X and Y directions relative to the central axis 135 of the front end cover.

[0138] The light guide exit surface 133 is located at a position in the X direction of the imaging unit 132. The shape of the light guide exit surface 133 is an ellipse.

[0139] The straight line 136 passes through the central axis 135 and intersects the light guide member exit surface 133. A cross section perpendicular to the paper plane and including the straight line 136 is a cross section including the central axis 135 and intersecting the light guide member exit surface 133.

[0140] The first predetermined section is a section that includes the central axis of the distal end cover and intersects the light guide exit surface. Therefore, the section that includes the line 136 and is perpendicular to the paper is the first predetermined section, and the line 136 indicates the position of the first predetermined section when the distal end of the endoscope is viewed from the object side.

[0141] like Figure 5 As shown in FIG. 1( b ), when the distal end 141 of the insertion portion of the endoscope 140 is viewed from the object side, an imaging unit 142 and a light guide emission surface 143 are arranged. The endoscope 140 uses one light guide.

[0142] The imaging unit 142 includes an objective optical system and an imaging element. The imaging element has an image capture range 144. The center of the imaging unit 142 is offset in the X direction relative to the central axis 145 of the front cover, but is not offset in the Y direction.

[0143] The light guide exit surface 143 is located at a position in the X direction of the imaging unit 142. The light guide exit surface 143 has a circular shape.

[0144] Line 146 passes through central axis 145 and contacts the outer periphery of light guide exit surface 143. This state is also included in the state where line 146 intersects light guide exit surface 143. A cross section perpendicular to the paper plane and including line 146 is a cross section including central axis 145 and intersecting light guide exit surface 143.

[0145] The first predetermined cross section is defined as described above. Therefore, the cross section perpendicular to the paper plane and including the straight line 146 is the first predetermined cross section, and the straight line 146 indicates the position of the first predetermined cross section when the distal end of the endoscope is viewed from the object side.

[0146] like Figure 5 As shown in FIG. 1( c ), when the distal end 151 of the insertion portion of the endoscope 150 is viewed from the object side, an imaging unit 152 and a light guide emission surface 153 are arranged. The endoscope 150 uses two light guides.

[0147] The imaging unit 152 includes an objective optical system and an imaging element. The imaging element has an image capture range 154. The center of the imaging unit 152 is not eccentric in the X direction but is eccentric in the Y direction relative to the central axis 155 of the front cover.

[0148] The light guide emission surface 153 is located at a position in the X direction of the imaging unit 152. The light guide emission surface 153 has a rectangular shape with one side being an arc.

[0149] The straight line 156 passes through the central axis 155 and intersects the light guide member exit surface 153. A cross section perpendicular to the paper plane and including the straight line 156 is a cross section including the central axis 155 and intersecting the light guide member exit surface 153.

[0150] The first predetermined cross section is defined as described above. Therefore, the cross section perpendicular to the paper plane and including the straight line 156 is the first predetermined cross section, and the straight line 156 indicates the position of the first predetermined cross section when the distal end of the endoscope is viewed from the object side.

[0151] like Figure 5 As shown in FIG. 1 (d), when the distal end 161 of the insertion portion of the endoscope 160 is viewed from the object side, an imaging unit 162 and a light guide emission surface 163 are arranged. The endoscope 160 uses two light guides.

[0152] The imaging unit 162 includes an objective optical system and an imaging element. The imaging element has an image capture range 164. The center of the imaging unit 162 is not eccentric in the X direction and is not eccentric in the Y direction relative to the central axis 165 of the front cover.

[0153] The light guide emission surface 163 is located in the Y direction of the imaging unit 162. The light guide emission surface 163 is in the shape of an annular sector.

[0154] The straight line 166 passes through the central axis 165 and intersects the light guide member exit surface 163. A cross section perpendicular to the paper plane and including the straight line 166 is a cross section including the central axis 165 and intersecting the light guide member exit surface 163.

[0155] The first predetermined cross section is defined as described above. Therefore, the cross section perpendicular to the paper plane and including the straight line 166 is the first predetermined cross section, and the straight line 166 indicates the position of the first predetermined cross section when the distal end of the endoscope is viewed from the object side.

[0156] The number and shape of the light guide's exit surfaces are not limited to Figure 5 The eccentric direction and eccentric amount of the camera unit relative to the central axis are not limited to Figure 5 The relative position between the light guide exit surface and the camera unit is also not limited to Figure 5 The relative positions shown.

[0157] The endoscope according to the first embodiment includes the above-described basic structure, and satisfies the following conditional expression (1) in at least one first predetermined cross section.

[0158] 0≤hA / r≤0.5 (1)

[0159] Here,

[0160] A local torus is a surface obtained by cutting off a portion of a torus.

[0161] A torus is the surface of a solid of revolution formed when a circle and a straight line that does not intersect the circle are present on a plane. The circle that is rotated is called a small circle.

[0162] hA is the distance between the first and second intersection points,

[0163] The first intersection point is the intersection point of a straight line passing through the center of the small circle and parallel to the central axis and the light guide's exit surface.

[0164] The second intersection point is the intersection point of the light rays passing through the boundary between the first plane and the curved surface and the light rays parallel to the central axis between the light guide member exit surface and the illumination area with the light guide member exit surface.

[0165] When the second intersection point is between the first intersection point and the side surface, the sign of the distance value is set to be positive.

[0166] r is the radius of the small circle.

[0167] use Figure 6 The parameters used in conditional expression (1) will be described. Figure 6 It is a cross-sectional view of the front end cover.

[0168] Front cover 170 has a first surface 171, a second surface 172, and a side surface 173. First surface 171 has a first flat surface 171a and a curved surface 171b. Curved surface 171b is located between first flat surface 171a and side surface 173. Second surface 172 has a non-illuminated area 172a and an illuminated area 172b. Illuminated area 172b faces light guide exit surface 174.

[0169] In the front cover 170, the entire surface of the illumination area 172b is formed by the PT surface. Figure 6 As shown, the illumination area 172b is formed by a portion of a circle 175, whose radius is r. The circle 175 is a small circle of the annulus.

[0170] Next, hA will be described.

[0171] The first intersection is Figure 6 The first intersection point is the intersection point between the light guide exit surface 174 and a straight line passing through the center of the circle 175 and parallel to the central axis 176 of the front cover.

[0172] The second intersection is Figure 6 The point A is shown in the middle. The light emitted from the point A in a manner parallel to the central axis 176 of the front cover is refracted in the illumination area 172b and passes through the boundary point between the first plane and the curved surface.

[0173] hA is the distance between the first intersection and the second intersection. If the second intersection is between the first intersection and the side surface, the sign of the distance is set to positive. If the second intersection is between the first intersection and the central axis, the sign of the distance is set to negative. Figure 6 , point A is located between point O and side surface 173. Therefore, the sign of the value of hA is positive.

[0174] Light is emitted from the light guide at various angles. Light emitted from the light guide exit surface 174 is refracted in the illumination area 172b, thereby widening the light distribution angle.

[0175] Light emitted from illumination area 172b is incident on first flat surface 171a and curved surface 171b of first surface 171. Because first flat surface 171a is a plane, the light is refracted in a direction that further widens the light distribution angle. Because curved surface 171b is convex and has positive refractive power, the light is refracted in a direction that narrows the light distribution angle.

[0176] To simplify the explanation, use Figure 6 The following describes the light emitted in a direction perpendicular to the light guide's exit surface. Light is emitted from the light guide's exit surface in various directions. Of the illumination light emitted from the light guide, the light emitted in a direction perpendicular to the light guide's exit surface has the highest intensity.

[0177] Point O is the intersection of the light guide exit surface 174 and a line passing through the center of circle 175 and parallel to the central axis 176 of the distal end cover. Points P and Q are located on the light guide exit surface 174 and are closer to the outer periphery of the endoscope than point O. Points P and Q are arranged in this order from point O toward the outer periphery.

[0178] The light emitted from the point O in a manner parallel to the central axis 176 is not refracted in the illumination area 172 b and the first plane 171 a but travels in a straight line.

[0179] A ray emitted from point P parallel to central axis 176 is refracted in illumination area 172b. The angle between central axis 176 and the refracted ray is α1. Next, the ray is refracted by first plane 171a. The angle between the central axis and the refracted ray is α2.

[0180] A ray emitted from point Q parallel to central axis 176 is refracted at illumination area 172b. The angle between the central axis and the refracted ray is β1. Next, the ray is refracted at curved surface 171b. The angle between central axis 176 and the refracted ray is β2.

[0181] When Figure 6 As shown, when β2 < α2, the intensity at a specific angle in the angular distribution of the illumination light becomes higher. This causes uneven illumination. If the difference in angle between the illumination light emitted from the first flat surface 171a and the illumination light emitted from the curved surface 171b is large, the uneven illumination becomes more noticeable.

[0182] The angle of light actually emitted from the light guide varies within a range below the angle represented by the numerical aperture. If the position of a ray of light that is emitted from the light guide exit surface 174 parallel to the central axis 176 of the front end cover and then passes through the boundary between the first flat surface 171a and the curved surface 171b is defined as point A on the light guide exit surface 174, and the distance between point O and point A is defined as hA, then within the range shown in conditional expression (1), uneven illumination is not noticeable and does not hinder observation.

[0183] When hA is further increased, all the illumination light emitted from the light guide passes through the first plane 171a. In this case, the illumination light from the curved surface disappears, eliminating the uneven illumination. However, since the outer diameter of the endoscope tip increases, the effectiveness of the endoscope decreases.

[0184] The technical significance of conditional expression (1) will be described. In this description, a range is assumed until the illumination unevenness reaches a maximum. In addition, the ease with which the insertion portion can be inserted into the body is referred to as "insertability."

[0185] When the upper limit value of the conditional expression (1) is exceeded, the second intersection point is too far from the central axis, or the radius of the small circle becomes too small.

[0186] When the second intersection is away from the central axis, the angle difference between the illumination light emitted from the first plane 171a and the illumination light emitted from the curved surface 171b increases, and uneven illumination becomes noticeable, making good observation difficult and hindering accurate diagnosis.

[0187] In addition, if the second intersection point is too far from the central axis, the curved surface is too far from the central axis. In this case, the outer diameter of the insertion portion increases, thereby deteriorating the insertability.

[0188] When the radius of the small circle becomes too small, the curvature radius of the PT surface becomes smaller, and thus the refractive power of the illumination area becomes larger. Therefore, the light distribution of the illumination light emitted from the illumination area becomes wider.

[0189] However, when the entire illumination area is formed by the PT surface, the range of the illumination area becomes narrower. When the range of the illumination area becomes narrower, the range of the emission surface will inevitably become narrower. Therefore, the amount of illumination light is insufficient.

[0190] When the range of the emission surface is not narrowed, the illumination area is formed by, for example, the PT surface and a plane located outside the PT surface.

[0191] In this case, the illumination light emitted from the light guide member's exit surface is incident on the PT surface and the flat surface. The flat surface has no refractive power. Therefore, the illumination light emitted from the flat surface diverges less than when the PT surface is used.

[0192] Part of the illumination light that has passed through the flat surface is incident on the curved surface. The illumination light incident on the curved surface is refracted toward the central axis, resulting in greater illumination unevenness.

[0193] If the lower limit value of conditional expression (1) is exceeded, the second intersection point is too close to the central axis, or the radius of the small circle becomes too large.

[0194] If the second intersection point is too close to the central axis, even if the light distribution angle is widened within the illumination area, most of the light will be incident on the curved surface and refracted in a direction where the light distribution angle becomes narrower.

[0195] If the radius of the small circle becomes too large, the curvature radius of the PT surface becomes too large. In this case, the refractive power of the illumination area becomes smaller, and the light distribution of the illumination light becomes narrower.

[0196] When the illumination light distribution becomes narrow, the amount of light in the periphery of the field of view becomes insufficient, making it difficult to observe the periphery of the field of view well, hindering accurate diagnosis.

[0197] The endoscope according to the second embodiment includes the above-described basic structure, and satisfies the following conditional expression (2) in at least one first predetermined cross section.

[0198] 0≤(hA×n 2 ) / r≤1.36 (2)

[0199] Here,

[0200] A local torus is a surface obtained by cutting off a portion of a torus.

[0201] A torus is the surface of a solid of revolution formed when a circle and a straight line that does not intersect the circle are present on a plane. The circle that is rotated is called a small circle.

[0202] hA is the distance between the first and second intersection points,

[0203] The first intersection point is the intersection point of a straight line passing through the center of the small circle and parallel to the central axis and the light guide's exit surface.

[0204] The second intersection point is the intersection point of the light rays passing through the boundary between the first plane and the curved surface and the light rays parallel to the central axis between the light guide member exit surface and the illumination area with the light guide member exit surface.

[0205] When the second intersection point is between the first intersection point and the side surface, the sign of the distance value is set to be positive.

[0206] n is the refractive index of the material of the front cover at the e-line,

[0207] r is the radius of the small circle.

[0208] The technical meaning of conditional expression (2) is the same as that of conditional expression (1).

[0209] In the endoscope of the first embodiment and the endoscope of the second embodiment, the light distribution of the illumination light can be widened, so that the illumination light is sufficiently irradiated not only in the longitudinal direction of the field of view but also in the diagonal direction of the field of view.

[0210] In the endoscope of this embodiment, the imaging unit includes an imaging element having a rectangular image capture range. The first cross section is a cross section represented by the following equation (3), and the second cross section is a cross section that satisfies the following conditional equation (4). The first cross section and the second cross section are first predetermined cross sections, and the first cross section and the second cross section satisfy the conditional equation (1).

[0211] ψ1=0 (3)

[0212] 0.2≤ψ2 / ε≤0.7 (4)

[0213] Here,

[0214] ψ1 is the angle between the second specified section and the first section,

[0215] ψ2 is the angle between the second specified section and the second section,

[0216] The second predetermined cross section is a cross section parallel to the long side of the imageable range and including the central axis.

[0217] ε is the angle between a cross section including the long side of the image-capable range and a cross section including the diagonal line of the image-capable range.

[0218] In the endoscope of this embodiment, the imaging unit includes an imaging element having a rectangular image capture range.

[0219] The first cross section is a cross section represented by the equation (3). The second cross section is a cross section that satisfies the conditional equation (4).

[0220] Formula (3) is a formula for the angle between the second predetermined section and the first section. Conditional formula (4) is a conditional formula for the angle between the second predetermined section and the second section. The second predetermined section is a section parallel to the long side of the imageable range and containing the central axis.

[0221] use Figure 7 The parameters used in equation (3) and conditional equation (4) are explained. Figure 7 This is a diagram of the distal end of the endoscope viewed from the object side.

[0222] Figure 7 (a) is a diagram showing a first example of the position of the first predetermined cross section and the position of the second predetermined cross section. Figure 5 (a) The same structures are denoted by the same reference numerals, and description thereof is omitted. Figure 7 (b) is a diagram showing a second example of the position of the first predetermined cross section and the position of the second predetermined cross section. Figure 5 The same structures as in (b) are denoted by the same reference numerals, and description thereof is omitted.

[0223] like Figure 7 As shown in FIG. 1 (a), an imaging unit 132 and a light guide emission surface 133 are provided at the distal end 131 of the insertion portion of the endoscope 130. The imaging unit 132 includes an imaging element. The imaging element has an imageable range 134. The imageable range 134 is rectangular in shape.

[0224] Line 180 is parallel to the long side of imageable range 134 and passes through central axis 135. The second predetermined cross section is a cross section parallel to the long side of the imageable range and including the central axis of the front end cover. Therefore, the cross section that includes line 180 and is perpendicular to the paper is the second predetermined cross section.

[0225] Similarly, when considering line 181, a cross section perpendicular to the paper plane and including line 181 includes central axis 135 and intersects light guide exit surface 133. Therefore, the cross section perpendicular to the paper plane and including line 181 can be considered the first predetermined cross section. If this cross section is considered the first cross section, then the angle ψ1 formed between line 180 and line 181 is the angle formed between the second predetermined cross section and the first cross section.

[0226] Since the first cross section intersects the second predetermined cross section, the angle ψ1 formed therebetween is not 0°.

[0227] As described above, the second predetermined cross section is a cross section that includes line 180 and is perpendicular to the paper. When considering line 182, the cross section that includes line 182 and is perpendicular to the paper includes central axis 135 and intersects light guide exit surface 133. Therefore, the cross section that includes line 182 and is perpendicular to the paper can be considered the first predetermined cross section. If this cross section is defined as the second cross section, the angle ψ2 formed between line 180 and line 182 is the angle formed between the second predetermined cross section and the second cross section.

[0228] A cross section perpendicular to the paper plane and including line 183 is parallel to the long side of imageable range 134. A cross section perpendicular to the paper plane and including line 184 overlaps with a diagonal line of the imageable range. Therefore, the angle ε formed between lines 183 and 184 is the angle formed between the cross section including the long side of the imageable range and the cross section including the diagonal line of the imageable range.

[0229] like Figure 7 As shown in (a), the angle represented by ψ2 is slightly larger than half the angle represented by ε.

[0230] like Figure 7 As shown in FIG. 1 (b), an imaging unit 152 and a light guide emission surface 153 are provided at the distal end 151 of the insertion portion of the endoscope 150. The imaging unit 152 includes an imaging element. The imaging element has an imageable range 154. The imageable range 154 is rectangular in shape.

[0231] Line 190 is parallel to the long side of imageable range 154 and passes through central axis 155. The second predetermined cross section is a cross section parallel to the long side of the imageable range and including the central axis of the front end cover. Therefore, the cross section that includes line 190 and is perpendicular to the paper is the second predetermined cross section.

[0232] Similarly, considering line 191, a cross section perpendicular to the paper plane and including line 191 includes central axis 155 and intersects light guide exit surface 153. Therefore, the cross section perpendicular to the paper plane and including line 191 can be considered the first predetermined cross section. If this cross section is considered the first cross section, then the angle ψ1 formed between line 190 and line 191 is the angle formed between the second predetermined cross section and the first cross section.

[0233] Since the first cross section and the second predetermined cross section are the same plane, the angle ψ1 formed therebetween is 0°.

[0234] As described above, the second predetermined cross section is a cross section that includes line 190 and is perpendicular to the paper. When considering line 192, the cross section that includes line 192 and is perpendicular to the paper includes central axis 155 and intersects light guide exit surface 153. Therefore, the cross section that includes line 192 and is perpendicular to the paper can be considered the first predetermined cross section. If this cross section is defined as the second cross section, the angle ψ2 formed between lines 190 and 192 is the angle formed between the second predetermined cross section and the second cross section.

[0235] A cross section perpendicular to the paper plane and including straight line 193 is parallel to the long side of imageable range 154. A cross section perpendicular to the paper plane and including straight line 194 overlaps with a diagonal line of imageable range 154. Therefore, the angle ε formed between straight lines 193 and 194 is the angle formed between the cross section including the long side of imageable range 154 and the cross section including the diagonal line of imageable range 154.

[0236] like Figure 7 As shown in (b), the angle represented by ψ2 is slightly larger than half the angle represented by ε.

[0237] The first cross section is a cross section represented by equation (3). The cross section represented by equation (3) is a cross section parallel to the long side of the imageable range and including the central axis, and corresponds to the long side direction of the field of view.

[0238] The first cross section is a first predetermined cross section, and in the first cross section, conditional expression (1) is satisfied. This reduces illumination unevenness in the longitudinal direction of the field of view and widens the distribution of illumination light.

[0239] The second cross section satisfies conditional expression (4). The cross section that satisfies conditional expression (4) is a cross section that intersects the long side of the imageable range and includes the central axis, and is in a direction that intersects the long side of the field of view. The direction that intersects the long side of the field of view is a direction that is close to the diagonal direction of the field of view.

[0240] The second cross section is the first predetermined cross section, and in the second cross section, conditional expression (1) is satisfied. This reduces illumination unevenness in a direction close to the diagonal direction of the field of view and broadens the distribution of illumination light.

[0241] According to the above results, by satisfying the equation (3) and the conditional equation (4), it is possible to reduce illumination unevenness in almost all directions.

[0242] If the value exceeds the upper limit of conditional expression (4), the angle between the second cross section and the second predetermined cross section increases, and the second cross section approaches the diagonal direction or even exceeds the diagonal direction. Alternatively, if the value exceeds the upper limit of conditional expression (4), the length of the short side of the image range becomes too short.

[0243] The second cross section is a first predetermined cross section. The first predetermined cross section is a cross section that includes the central axis of the front end cover and intersects the light guide exit surface. Therefore, it is assumed that the second cross section intersects the light guide exit surface.

[0244] The increasing angle between the second cross section and the second predetermined cross section means that there are many light guide exit surfaces along the short side of the imageable range, resulting in an increase in the amount of illumination light projected outside the field of view. When the amount of illumination light projected from the light guide exit surfaces that projects outside the field of view increases, the efficiency of the illumination system (hereinafter referred to as illumination efficiency) decreases, resulting in a dimmer illumination light even if the number of optical fibers used in the light guide remains the same.

[0245] Furthermore, the number of optical fibers that do not contribute to illumination increases. The number of optical fibers affects the outer diameter and flexibility of the insertion section's tip. When there are many optical fibers that do not contribute to illumination, the outer diameter of the insertion section's tip becomes unnecessarily large. Furthermore, the flexibility of the insertion section's tip decreases, increasing the risk of optical fiber breakage.

[0246] When the length of the short side of the image-capable range becomes too short, the image acquisition range becomes too narrow in the short-side direction of the field of view.

[0247] If the lower limit value of conditional expression (4) is not reached, the second cross section is too close to the second predetermined cross section, or the length of the short side of the imageable range becomes too long.

[0248] The first cross-section overlaps with the second predetermined cross-section. If the second cross-section is too close to the second predetermined cross-section, the difference from the first cross-section becomes too small. In this case, it is possible to reduce illumination unevenness along the long side of the field of view and broaden the illumination light distribution. However, in directions intersecting the long side of the field of view, it becomes difficult to reduce illumination unevenness and broaden the illumination light distribution.

[0249] If the short side of the imageable range becomes too long, the image sensor becomes too large. In this case, the outer diameter of the insertion portion becomes larger, thus deteriorating the insertability.

[0250] The endoscope of this embodiment satisfies the following conditional expression (5).

[0251] 0<(dy×n) / R<0.5 (5)

[0252] Here,

[0253] dy is the distance between the first and third intersection points,

[0254] The third intersection point is the intersection point of a straight line passing through the center of curvature of the curved surface of the first surface and parallel to the central axis and the light guide member output surface,

[0255] When the third intersection point is between the first intersection point and the side surface, the sign of the distance value is set to be positive.

[0256] n is the refractive index of the material of the front cover at the e-line,

[0257] R is the radius of curvature of the curved surface of the first surface.

[0258] use Figure 8 The parameters used in conditional expression (5) will be described. Figure 8 This is a cross-sectional view of the front end cover. Figure 6 The same structures are denoted by the same reference numerals, and description thereof is omitted.

[0259] n is the refractive index at the e-line of the material of the front end cover 170. R is the curvature radius of the curved surface 171b.

[0260] The third intersection is Figure 8 The third intersection point is the intersection point of the light guide member exit surface 174 and a straight line passing through the center of curvature C2 of the curved surface 171 b and parallel to the central axis 176 .

[0261] dy is the distance between the first intersection and the third intersection. If the third intersection is between the first intersection and the side, the sign of the distance is set to positive. If the third intersection is between the first intersection and the central axis, the sign of the distance is set to negative. Figure 8 , the intersection B is located between the intersection O and the side surface 173. Therefore, the sign of the value of dy is positive.

[0262] When the upper limit value of conditional expression (5) is exceeded, the third intersection point is too far from the central axis, or the curvature radius of the curved surface becomes too small.

[0263] If the third intersection point is too far from the central axis, as explained in the technical meaning of conditional expression (1), the illumination unevenness increases and the insertion performance deteriorates.

[0264] When the radius of curvature of the curved surface becomes too small, the difference in angle between the illumination light emitted from the first flat surface 171a and the illumination light emitted from the curved surface 171b becomes larger, and uneven illumination becomes noticeable, making good observation difficult and hindering accurate diagnosis.

[0265] Furthermore, when the curvature radius of the curved surface becomes too small, the shape of the distal end of the insertion portion becomes angular, thereby deteriorating the insertability.

[0266] If the lower limit value of conditional expression (5) is not reached, the third intersection point is too close to the central axis, or the curvature radius of the curved surface becomes infinite.

[0267] When the third intersection point is too close to the central axis, the light distribution of the illumination light becomes narrower as described in the technical meaning of the conditional expression (1).

[0268] When the radius of curvature of the curved surface becomes infinite, it cannot be used as an endoscope.

[0269] The endoscope of this embodiment satisfies the following conditional expression (6).

[0270] -0.15<n×(Rrt)<0 (6)

[0271] Here,

[0272] n is the refractive index of the material of the front cover at the e-line,

[0273] R is the radius of curvature of the first surface,

[0274] r is the radius of the small circle,

[0275] t is the shortest distance between the first plane and the illumination area.

[0276] use Figure 9 The parameters used in conditional expression (6) will be described. Figure 9 This is a cross-sectional view of the front end cover. Figure 8 The same structures are denoted by the same reference numerals, and description thereof is omitted.

[0277] t in Figure 9 t is the distance between point P1 and point P2. The distance between point P1 and point P2 is the smallest distance between the first plane 171a and the illumination area 172b. The sign of the value of t is always positive.

[0278] If the upper limit value of conditional expression (6) is exceeded, the curvature radius of the curved surface becomes too large, or the radius of the small circle becomes too small.

[0279] When the curvature radius of the curved surface becomes too large, the curved surface is too far away from the central axis. As a result, the outer diameter of the insertion portion becomes too large, resulting in poor insertability.

[0280] When the radius of the small circle becomes too small, the amount of illumination light becomes insufficient as described in the technical meaning of conditional expression (1).

[0281] If the lower limit value of conditional expression (6) is exceeded, the curvature radius of the curved surface becomes too small, or the radius of the small circle becomes too large.

[0282] When the curvature radius of the curved surface becomes too small, as explained in the technical meaning of conditional expression (5), it is impossible to reduce uneven illumination or insertion performance deteriorates.

[0283] When the radius of the small circle becomes too large, the light distribution of the illumination light becomes narrower as described in the technical meaning of the conditional expression (1).

[0284] In the endoscope of this embodiment, the illumination region includes the second plane and the partial annular surface, and the second plane is located closer to the central axis than the partial annular surface.

[0285] Figure 10 This is a cross-sectional view of the front end cover. Figure 6 The same structures are denoted by the same reference numerals, and description thereof is omitted.

[0286] In the front cover 200, the second surface 201 has a non-illumination area 201a and an illumination area 201b. The illumination area 201b has a second plane 202 and a PT surface 203. The second plane 202 is located closer to the central axis 176 than the PT surface 203.

[0287] The illumination light emitted from the light guide member emission surface 174 enters the illumination area 201 b . The illumination light emitted from the light guide member emission surface 174 is divergent light, and thus the divergent light enters the second plane 202 and the PT surface 203 .

[0288] The divergent light incident on the second plane 202 travels toward the first surface 171. The second plane 202 has no refractive power. Therefore, the degree of divergence of the illumination light emitted from the second plane 202 is smaller than when a PT plane is used.

[0289] A through hole 204 is formed in the front end cover 200. When the degree of diffusion of the illumination light traveling toward the first surface 171 is large, the amount of illumination light traveling toward the through hole 204 increases.

[0290] The imaging unit is located in the through hole 204. When the illumination light emitted from the second surface 201 reaches the through hole 204, light is absorbed and reflected by the side surfaces of the through hole 204 and the imaging unit.

[0291] Heat is generated by the absorption of light, and thus the temperature of the distal end of the insertion portion rises.

[0292] In the reflection of light, the reflected light is totally reflected by the first plane 171a or is transmitted through the first plane 171a. In either case, the illumination light travels outside the field of view or travels inside the field of view.

[0293] When the illumination light travels outside the field of view, more illumination light reaches outside the field of view, thus reducing illumination efficiency. When the illumination light travels inside the field of view, uneven illumination occurs.

[0294] As described above, the second plane 202 has no refractive power. Therefore, in the front cover 200, little illumination light travels toward the through hole 204. As a result, heat generation, a decrease in illumination efficiency, and the occurrence of uneven illumination can be suppressed.

[0295] The divergent light incident on the PT surface 203 travels toward the first surface 171. The PT surface 203 functions as a surface with negative refractive power. In this case, the divergent light incident on the PT surface 203 further diverges. The divergent light emitted from the PT surface 203 is incident on the first flat surface 171a and the curved surface 171b.

[0296] The first plane 171a has no refractive power. Therefore, divergent light is emitted from the first plane 171a. The illumination light emitted from the first plane 171a is divergent light. Therefore, the illumination light distribution can be widened.

[0297] In the endoscope of this embodiment, the imaging unit includes an imaging element having a rectangular image capture range. The outer periphery of the light guide's exit surface is formed by an inner edge, an intermediate edge, and an outer edge. The inner edge is located closer to the central axis than the outer edge, and the intermediate edge is located between the inner edge and the outer edge. The outer edge is an arc of a circle centered on the central axis and satisfies the following conditional equation (7).

[0298] 0.7<θ / ε<1.2 (7)

[0299] Here,

[0300] θ is the angle between the second specified section and the third section,

[0301] The second predetermined cross section is a cross section parallel to the long side of the imageable range and including the central axis.

[0302] The third section is a section including the intersection of the outer edge and the middle edge, and the central axis.

[0303] ε is the angle between a cross section including the long side of the image-capable range and a cross section including the diagonal line of the image-capable range.

[0304] Figure 11 This is a diagram of the endoscope tip viewed from the object side. Figure 7 The same structures as in (b) are denoted by the same reference numerals, and description thereof is omitted.

[0305] The light guide emission surface 153 is a rectangular shape with one side being an arc. The outer periphery 210 of the light guide emission surface 153 is formed by an inner edge 211 , a middle edge 212 , and an outer edge 213 .

[0306] Inner edge 211 is located closer to central axis 155 than outer edge 213. Intermediate edge 212 is located between inner edge 211 and outer edge 213. Inner edge 211 and intermediate edge 212 are straight lines. Outer edge 213 is an arc of a circle centered on central axis 155.

[0307] By making the light guide exit surface 153 a rectangular shape with one side formed into an arc, the light guide exit surface 153 can be made larger than in the case of a rectangle, and the illumination light emitted from the light guide exit surface 153 can reach the periphery of the illumination area. Therefore, the illumination light emitted from the light guide exit surface 153 can be diverged, thereby widening the illumination light distribution. As a result, good observation can be achieved at the periphery of the field of view.

[0308] Furthermore, by making the outer edge 213 into an arc shape, the workability of the light guide exit surface 153 can be improved. By improving the workability, the light guide exit surface 153 can be processed with high precision. As a result, the dimensional error of the light guide exit surface 153 can be reduced.

[0309] The shape of the recessed portion of the front end cover can also be easily processed with high precision. Since the dimensional error of the front end cover can be reduced, the front end cover and the light guide exit surface 153 can be easily assembled.

[0310] exist Figure 11 In the embodiment, the light guide member exit surface 153 is located on both sides of the camera unit 152. However, the light guide member exit surface 153 may also be located on a single side of the camera unit 152.

[0311] use Figure 11 The parameters used in conditional expression (7) will be described.

[0312] As described above, ε is the angle between the cross section including the long side of the imageable range and the cross section including the diagonal line of the imageable range. In addition, the cross section including the straight line 190 and perpendicular to the paper is the second predetermined cross section.

[0313] Considering line 214, a cross section perpendicular to the paper plane that includes line 214 includes the intersection P3 of outer edge 213 and middle edge 212, as well as central axis 155. The third cross section is a cross section that includes the intersection of the outer edge and middle edge, as well as the central axis. Therefore, the cross section perpendicular to the paper plane that includes line 214 can be considered the third cross section. Therefore, the angle θ formed between line 190 and line 214 is the angle formed between the second predetermined cross section and the third cross section.

[0314] The intersection point P3 represents one end of the light guide member exit surface 153 in the short side direction of the image range 154. Figure 11 In the figure, when the intersection point P3 moves away from the X-axis in the upward direction, the light guide member output surface 153 expands along the short side direction of the image range 154.

[0315] By satisfying conditional expression (7), the illumination light distribution can be widened. Consequently, illumination light is sufficiently applied not only along the long side of the field of view but also along its diagonal directions. Furthermore, since less illumination light is directed outside the field of view along its short side, illumination efficiency can be improved.

[0316] In the case of a value higher than the upper limit of conditional expression (7), the light guide member's exit surface becomes too large in the short side direction of the image range, or the length of the short side of the image range becomes too short. When the light guide member's exit surface becomes too large in the short side direction of the image range, the lighting efficiency decreases as explained in the technical significance of conditional expression (4). In addition, when the area of the light guide member's exit surface increases, the number of optical fibers increases, and thus the outer shape of the endoscope becomes larger. When the number of optical fibers is increased while maintaining the thin outer shape of the endoscope, the risk of optical fiber breakage increases at the curved portion of the endoscope insertion portion, etc.

[0317] When the length of the short side of the image-capable range becomes too short, the image acquisition range becomes too narrow in the short-side direction of the field of view.

[0318] If the value of conditional expression (7) is below the lower limit, the light guide's exit surface becomes too small in the direction of the short side of the imageable range, or the length of the short side of the imageable range becomes too long. As a result, the illumination light distribution becomes narrower in the diagonal direction of the field of view. In addition, the illumination light intensity is insufficient.

[0319] As a result, it is difficult to perform good observation around the visual field in the diagonal direction, and it is difficult to perform accurate diagnosis because it is difficult to perform good observation.

[0320] When the length of the short side of the image-capable range becomes too long, the insertability deteriorates as explained in the technical meaning of conditional expression (3).

[0321] In the endoscope of this embodiment, the outer periphery of the light guide's exit surface is formed by an inner edge, an intermediate edge, and an outer edge. The inner edge is located closer to the central axis than the outer edge, and the intermediate edge is located between the inner edge and the outer edge. The outer edge is an arc of a circle centered on the central axis, and satisfies the following conditional expression (8) in at least one first predetermined cross-section.

[0322] 0.6<L / r≤1.0 (8)

[0323] Here,

[0324] L is the distance between the first intersection point and the outer edge,

[0325] r is the radius of the small circle.

[0326] Figure 12 This is a diagram of the front end of the insertion portion and the front end cover. Figure 12(a) is a diagram of the front end of the endoscope viewed from the object side. Figure 11 The same structures are denoted by the same reference numerals, and description thereof is omitted. Figure 12 (b) is a cross-sectional view of the front end cover. Figure 6 The same structures are denoted by the same reference numerals, and description thereof is omitted.

[0327] Circumference 220 is a circumference formed by the center of circle 175 when circle 175 is rotated about central axis 155 .

[0328] The straight line 221 passes through the central axis 155 and intersects the light guide member exit surface 153. A cross section perpendicular to the paper plane and including the straight line 221 is a cross section including the central axis 155 and intersecting the light guide member exit surface 153.

[0329] The first predetermined section is a section that includes the central axis of the distal end cover and intersects the light guide's exit surface. Therefore, the section that includes the line 221 and is perpendicular to the paper is the first predetermined section, and the line 221 indicates the position of the first predetermined section when the distal end of the endoscope is viewed from the object side.

[0330] The parameters used in conditional expression (8) will be described.

[0331] As described above, the intersection O is the first intersection, and L is the distance between the first intersection and the outer edge 213 .

[0332] When the upper limit value of conditional expression (8) is exceeded, the distance between the first intersection point and the outer edge becomes too long, or the radius of the small circle becomes too small.

[0333] If the distance from the first intersection to the outer edge becomes too long, the PT plane alone cannot form the illumination area. The illumination area is formed by the PT plane and the plane outside the PT plane. Therefore, as the technical significance of conditional expression (1) indicates, the illumination unevenness increases.

[0334] As a result, it is difficult to perform good observation around the visual field. In addition, since it is difficult to perform good observation, it is difficult to perform accurate diagnosis.

[0335] Furthermore, when the light guide exit surface is located in the longitudinal direction of the imageable range, the light guide exit surface becomes too wide in the longitudinal direction of the imageable range. Consequently, the outer diameter of the insertion portion becomes too large, resulting in poor insertability.

[0336] When the radius of the small circle becomes too small, the amount of illumination light becomes insufficient as described in the technical meaning of conditional expression (1).

[0337] If the lower limit value of conditional expression (8) is exceeded, the distance between the first intersection point and the outer edge becomes too short, or the radius of the small circle becomes too large.

[0338] If the distance between the first intersection and the outer edge is too short, the range of the light guide member's emission surface in the first predetermined cross section becomes too narrow, thereby causing insufficient light intensity of the illumination light or narrowing the light distribution of the illumination light.

[0339] As a result, it is difficult to perform good observation around the visual field. In addition, since it is difficult to perform good observation, it is difficult to perform accurate diagnosis.

[0340] When the radius of the small circle becomes too large, the light distribution of the illumination light becomes narrower as described in the technical meaning of the conditional expression (1).

[0341] The endoscope of this embodiment satisfies the following conditional expression (9).

[0342] 10<a / r<16 (9)

[0343] Here,

[0344] a is the outer diameter of the front cover,

[0345] r is the radius of the small circle.

[0346] Even if the object is the same, the outer diameter of the insertion portion of the endoscope varies depending on the purpose of use. For example, endoscopes used in the field of otolaryngology include those for observation only and those for observation and treatment.

[0347] An endoscope used only for observation does not have a channel for treatment instruments, so an imaging element with a wide image capture range can be used.

[0348] The larger the imageable range, the greater the number of pixels. Therefore, a high-quality image can be obtained. However, due to the large imageable range, the outer diameter of the insertion portion tends to increase.

[0349] In addition, regarding endoscopes for observing the stomach, there are two types: transoral endoscopes and transnasal endoscopes. In the case of a transoral endoscope, the insertion portion is inserted through the mouth. In the case of a transnasal endoscope, the insertion portion is inserted through the nose.

[0350] The space between the nose and mouth where the insertion section passes is narrow. Therefore, the outer diameter of the insertion section of a transnasal endoscope is smaller than that of a transoral endoscope. When the outer diameter of the insertion section is small, it is impossible to use an imaging element with a large image capture range.

[0351] Therefore, the number of pixels in the imaging element of a transnasal endoscope is smaller than that of a transoral endoscope. As a result, the image quality of the image through the transnasal endoscope is likely to be lower than that of the image through the transoral endoscope.

[0352] When observing the same object with an oral endoscope and a transnasal endoscope, it is preferable that the object be observed in the same manner. Depth of field is one of the conditions for being able to observe the object in the same manner. Therefore, it is preferable that the depth of field in the oral endoscope is the same as the depth of field in the transnasal endoscope.

[0353] The depth of field is determined by the focal length and aperture value of the objective optical system and the permissible circle of confusion of the imaging element. As mentioned above, the number of pixels in the imaging element of a transnasal endoscope is less than that of an oral endoscope. Therefore, the focal length of an oral endoscope is larger. In addition, if the pixel size is the same, the permissible circle of confusion is the same. Therefore, it is necessary to increase the aperture value of the objective optical system in an oral endoscope to achieve the same depth of field.

[0354] Brightness is one of the conditions for uniform observation of objects. As mentioned above, the aperture value of the objective optical system in an oral endoscope is larger than that of the objective optical system in a transnasal endoscope. Therefore, the area of the light guide's exit surface in an oral endoscope must be larger than that in a transnasal endoscope.

[0355] The outer diameter of the insertion portion of the endoscope, the size of the imageable range, and the size of the light guide's emission surface are related to each other. The following ratios fall within a fixed range.

[0356] (A) Ratio of the outer diameter of the insertion portion of the endoscope to the size of the imageable range.

[0357] (B) Ratio of the outer diameter of the insertion portion of the endoscope to the size of the light guide exit surface.

[0358] (C) The ratio of the size of the image range to the size of the light guide's exit surface can be taken.

[0359] use Figure 13 The parameters used in conditional expression (9) will be described.

[0360] Figure 13 It is a cross-sectional view of the front end cover. Figure 13 (a) is a diagram showing a first example of a front end cover. Figure 2 The same structures as in (b) are denoted by the same reference numerals, and description thereof is omitted. Figure 13 (b) is a diagram showing a second example of a front end cover. Figure 4 The same structures as in (b) are denoted by the same reference numerals, and description thereof is omitted.

[0361] In the front cover 40 , the illumination area 42 b is located on one side of the through hole 44 . In the front cover 100 , the illumination area 102 b is located on both sides of the through hole 104 .

[0362] exist Figure 13In (a), a is the outer diameter of the front cover 40. Figure 13 In (b), a is the outer diameter of the front cover 100. Circle 175 is the small circle of the annulus. r is the radius of the small circle.

[0363] The side surfaces of the distal end cover 40 and the distal end cover 100 can be cylindrical side surfaces. In this case, the outer diameters of the distal end cover 40 and the distal end cover 100 are represented by the diameter of the bottom surface of the cylinder.

[0364] When the upper limit value of conditional expression (9) is exceeded, the outer diameter of the front end cover becomes too large, or the radius of the small circle becomes too small.

[0365] If the outer diameter of the front cover becomes too large, the insertability deteriorates.

[0366] When the radius of the small circle becomes too small, the amount of illumination light becomes insufficient as described in the technical meaning of conditional expression (1).

[0367] If the value falls below the lower limit of conditional expression (9), the outer diameter of the front end cover becomes too small, or the radius of the small circle becomes too large.

[0368] If the outer diameter of the front end cover becomes too small, the range of the light guide's emission surface becomes too narrow, thereby causing insufficient light quantity of the illumination light or narrowing the light distribution of the illumination light.

[0369] In addition, the diameter of the imaging unit becomes too small. In this case, the image range that can be captured by the imaging element becomes smaller and the number of pixels decreases. As a result, it is difficult to obtain high-quality images.

[0370] When the radius of the small circle becomes too large, the light distribution of the illumination light becomes narrower as described in the technical meaning of the conditional expression (1).

[0371] The endoscope system according to the present embodiment includes the endoscope according to the present embodiment and an image processing device.

[0372] The endoscope system of the present embodiment can perform illumination with a wide distribution of illumination light and little light loss and illumination unevenness.

[0373] As described above, the endoscope of this embodiment can achieve illumination with a wide illumination distribution and minimal light loss and uneven illumination. Consequently, images with minimal noise and brightness unevenness can be acquired. Consequently, the endoscope system of this embodiment can maintain high image quality even when image processing is performed.

[0374] Hereinafter, an embodiment of the endoscope will be described in detail based on the drawings. However, the present invention is not limited to the embodiment.

[0375] Figure 14 This is a diagram of the endoscope tip viewed from the object side. Figure 7The same structures as in (b) are denoted by the same reference numerals, and description thereof is omitted.

[0376] In Examples 1 to 8, the light guide exit surface 153 is located on both sides of the imaging unit 152. The imageable range 154 is rectangular in shape. The outer edge of the light guide exit surface 153 is an arc of a circle centered on the central axis 155.

[0377] IUD is the outer diameter of the imaging unit 152. LGD is the diameter of the circle forming the outer edge of the light guide exit surface 153. LGX is the length of the light guide exit surface 153 in the second predetermined cross section. LGY is the length of the light guide exit surface 153 in a cross section perpendicular to the second predetermined cross section. IML is the length of the long side of the imageable range 154. IMS is the length of the short side of the imageable range 154.

[0378] The following are figures illustrating various embodiments. Figures 15 to 22 In FIG. 1 , (a) is a view of the distal end of the endoscope viewed from the object side. (b) is a cross-sectional view of the distal end of the insertion portion taken along the cutting line AA. (c) is a cross-sectional view of the distal end of the insertion portion taken along the cutting line BB. (d) is a graph showing the distribution of illumination light.

[0379] Section line AA indicates the position of the first cross section, and section line BB indicates the position of the second cross section.

[0380] The insertion portion of the endoscope of Example 1 includes an imaging unit and a light guide, and a distal end cover is disposed at the distal end of the insertion portion.

[0381] The entire illumination area is formed by the PT surface. In the first cross section, the PT surface is approximately semicircular. The light guide member has an exit surface that is a rectangular shape with one side being an arc.

[0382] The insertion portion of the endoscope of Example 2 includes an imaging unit and a light guide, and a distal end cover is disposed at the distal end of the insertion portion.

[0383] The illumination area is formed by the PT surface and the flat surface. The flat surface is located closer to the central axis than the PT surface. In the first cross section, the PT surface is generally fan-shaped. The light guide's exit surface is a rectangular shape with one side being an arc.

[0384] The insertion portion of the endoscope of Example 3 includes an imaging unit and a light guide, and a distal end cover is disposed at the distal end of the insertion portion.

[0385] The entire illumination area is formed by the PT surface. In the first cross section, the PT surface is substantially fan-shaped. The shape of the light guide member's exit surface is substantially annular fan-shaped.

[0386] The insertion portion of the endoscope of Example 4 includes an imaging unit and a light guide, and a distal end cover is disposed at the distal end of the insertion portion.

[0387] The illumination area is formed by the PT surface and the flat surface. The flat surface is located closer to the central axis than the PT surface. In the first cross section, the PT surface is generally fan-shaped. The light guide member's exit surface is generally annular fan-shaped.

[0388] The insertion portion of the endoscope of Example 5 includes an imaging unit and a light guide, and a distal end cover is disposed at the distal end of the insertion portion.

[0389] The entire illumination area is formed by the PT surface. In the first cross section, the PT surface is substantially fan-shaped. The light guide member has an exit surface that is a rectangular shape with one side being an arc.

[0390] The insertion portion of the endoscope of Example 6 includes an imaging unit and a light guide, and a distal end cover is disposed at the distal end of the insertion portion.

[0391] The entire illumination area is formed by the PT surface. In the first cross section, the PT surface is approximately semicircular. The light guide member has an exit surface that is a rectangular shape with one side being an arc.

[0392] The insertion portion of the endoscope of Example 7 includes an imaging unit and a light guide, and a distal end cover is disposed at the distal end of the insertion portion.

[0393] The illumination area is formed by the PT surface and the flat surface. The flat surface is located closer to the central axis than the PT surface. In the first cross section, the PT surface is generally fan-shaped. The light guide's exit surface is a rectangular shape with one side being an arc.

[0394] The insertion portion of the endoscope of Example 8 includes an imaging unit and a light guide, and a distal end cover is disposed at the distal end of the insertion portion.

[0395] The illumination area is formed by the PT surface and the flat surface. The flat surface is located closer to the central axis than the PT surface. In the first cross section, the PT surface is generally fan-shaped. The light guide's exit surface is a rectangular shape with one side being an arc.

[0396] Numerical data of the above-mentioned embodiments are shown below.

[0397]

[0398]

[0399] The values of the conditional expressions in each example are as follows.

[0400]

[0401] In the endoscope of this embodiment, a light guide is used for illumination. However, light-emitting diodes can also be used for illumination. In this case, a light guide is not used, so the packaging surface of the light-emitting diode can be regarded as the light guide's emission surface. Alternatively, a laser diode and a phosphor can be used for illumination. In this case, a light guide is not used, so the surface of the phosphor can be regarded as the light guide's emission surface.

[0402] Industrial applicability

[0403] The present invention is suitable for an endoscope and an endoscope system capable of performing illumination with a wide distribution of illumination light and little light loss and illumination unevenness.

[0404] Description of Reference Numerals

[0405] 1: Endoscope system; 2: Electronic endoscope; 3: Housing; 4: Display unit; 5: Operation unit; 6: Insertion unit; 7: Universal cable; 8: Connector; 9: Front end cover; 20: Endoscope; 30: Front end of insertion unit; 31: External tube; 32: Metal tube; 40: Front end cover; 41: First surface; 41a: First plane; 41b: Curved surface; 42: Second surface; 42a: Non-illuminated area; 42b: Illuminated area; 43: Side surface; 44: Through hole; 45, 46: Arrows; 47: Center axis; 48: Recess; 50: Image pickup unit; 51: Objective optical system; 52: Image pickup element; 60: Light guide; 61: Light guide exit surface; 70: Torus; 71: Solid; 72: Small circle (circle); 73: Straight line; 74: Circumference; 75: Arc; 80: Endoscope; 90: Front end of insertion portion; 91: External tube; 92: Metal tube; 100: Front end cover; 101: First surface; 101a: First plane; 101b: Curved surface; 102: Second surface; 102a: Non-illuminated area; 102b: Illuminated area; 103: Side surface; 104: Through hole; 105, 106: Arrows; 107: Central axis; 108: Recess; 110: Imaging unit; 111: Objective optical system; 112: Imaging element; 120: Light guide; 121: Light guide exit surface; 130, 140, 150, 160: Endoscope; 131, 141, 151, 161: Front end of the insertion portion; 132, 142, 152, 162: Camera unit; 133, 143, 153, 163: Light guide exit surface; 134, 144, 154, 164: Image range; 135, 145, 155, 165: Center axis; 136, 146, 156, 166: Linear; 170: Front end cover; 171: First surface; 171a: First plane; 171b: Curved surface; 172: Second surface; 172a: Non-illuminated area; 172 b: illumination area; 173: side; 174: light guide exit surface; 175: circle; 176: center axis; 180, 181, 182, 183, 184: straight line; 190, 191, 192, 193, 194: straight line; 200: front end cover; 201: second surface; 201a: non-illumination area; 201b: illumination area; 202: second plane; 203: PT surface; 204: through hole; 210: outer periphery; 211: inner edge; 212: middle edge; 213: outer edge; 214: straight line; 220: circumference; 221: straight line; O, A, B, P, P1, P2, P3, Q: points.

Claims

1. An endoscope, characterized in that: The insertion portion of the endoscope has an imaging unit and a light guide, and a front end cover is arranged at the front end of the insertion portion. The illumination light is emitted from the light guide member exit surface, The front cover has a through portion for inserting and fixing the camera unit. When the object side of the front end cover is defined as the first surface, the hand side of the front end cover is defined as the second surface, and the outer peripheral portion of the front end cover is defined as the side surface, The first surface has a first plane and a curved surface, The curved surface is located between the first plane and the side surface, The second surface has an illumination area into which the illumination light is incident. At least a portion of the illumination area is formed by a partial annulus, The first predetermined cross section is a cross section that includes the central axis of the front end cover and intersects the light guide output surface. In at least one of the first predetermined cross sections, the following conditional expression (1) is satisfied: 0≤hA / r≤0.5 (1) Here, The local annulus is a surface obtained by cutting a part of the annulus. The torus is the surface of a rotating body formed when a circle and a straight line that does not intersect the circle exist on a plane and the circle is rotated about the straight line as an axis. The rotated circle is called a small circle. hA is the distance between the first and second intersection points, The first intersection point is the intersection point of a straight line passing through the center of the small circle and parallel to the central axis and the light guide member exit surface. The second intersection point is an intersection point between the light ray passing through the boundary between the first plane and the curved surface and the light ray parallel to the central axis between the light guide member exit surface and the illumination area and the light guide member exit surface. When the second intersection point is located between the first intersection point and the side surface, the sign of the value of the distance is set to be positive. r is the radius of the small circle.

2. The endoscope according to claim 1, wherein: The imaging unit includes an imaging element. The imaging element has a rectangular range in which an image of a subject can be acquired from the imaging element, that is, an image capture range. The first cross section is a cross section represented by the following formula (3), The second cross section is a cross section that satisfies the following conditional expression (4): The first cross section and the second cross section are the first prescribed cross sections, In the first cross section and the second cross section, the conditional expression (1) is satisfied. ψ1=0 (3) 0.2≤ψ2 / ε≤0.7 (4) Here, ψ1 is the angle between the second specified section and the first section, ψ2 is the angle between the second predetermined section and the second section, The second predetermined cross section is a cross section parallel to the long side of the imageable range and including the central axis. ε is the angle formed by a cross section including the long side of the image-capable range and a cross section including the diagonal line of the image-capable range.

3. The endoscope according to claim 1, wherein Satisfy the following conditional formula (5), 0<(dy×n) / R<0.5 (5) Here, dy is the distance between the first intersection point and the third intersection point, The third intersection point is an intersection point of a straight line passing through the center of curvature of the curved surface of the first surface and parallel to the central axis and the exit surface, In the case where the third intersection point is located between the first intersection point and the side surface, the sign of the value of the distance is positive, n is the refractive index of the material of the front cover at the e-line, R is the radius of curvature of the curved surface of the first surface.

4. The endoscope according to claim 3, wherein: The following condition (6) is satisfied: -0.15<n×(Rrt)<0 (6) Here, n is the refractive index of the material of the front cover at the e-line, R is the radius of curvature of the curved surface of the first surface, r is the radius of the small circle, t is the shortest distance between the first plane and the illumination area.

5. The endoscope according to claim 1, wherein The illumination area has a second plane and the partial annular surface, The second plane is located closer to the central axis than the partial annular surface.

6. The endoscope according to claim 1, wherein The imaging unit includes an imaging element. The image sensor has a rectangular image range. The outer periphery of the light guide member's exit surface is formed by an inner edge, a middle edge and an outer edge. The inner edge is located closer to the central axis than the outer edge. The intermediate edge is located between the inner edge and the outer edge, The outer edge is an arc of a circle centered on the central axis, The endoscope satisfies the following conditional formula (7): 0.7<θ / ε<1.2 (7) Here, θ is the angle between the second specified section and the third section, The second predetermined cross section is a cross section parallel to the long side of the imageable range and including the central axis. The third cross section is a cross section including the intersection of the outer edge and the middle edge, and the central axis. ε is the angle formed by a cross section including the long side of the image-capable range and a cross section including the diagonal line of the image-capable range.

7. The endoscope according to claim 1, wherein The outer periphery of the light guide member's exit surface is formed by an inner edge, a middle edge and an outer edge. The inner edge is located closer to the central axis than the outer edge. The intermediate edge is located between the inner edge and the outer edge, The outer edge is an arc of a circle centered on the central axis, In at least one of the first predetermined cross sections, the following conditional expression (8) is satisfied: 0.6＜L / r≤1.0 (8) Here, L is the distance between the first intersection point and the outer edge, r is the radius of the small circle.

8. The endoscope according to claim 1 or 7, characterized in that The following conditional formula (9) is satisfied: 10＜a / r＜16 (9) Here, a is the outer diameter of the front end cover, r is the radius of the small circle.

9. An endoscope, characterized in that: The insertion portion of the endoscope has an imaging unit and a light guide, and a front end cover is arranged at the front end of the insertion portion. The illumination light is emitted from the light guide member exit surface, The front cover has a through portion for inserting and fixing the camera unit. When the object side of the front end cover is defined as the first surface, the hand side of the front end cover is defined as the second surface, and the outer peripheral portion of the front end cover is defined as the side surface, The first surface has a first plane and a curved surface, The curved surface is located between the first plane and the side surface, The second surface has an illumination area into which the illumination light is incident. At least a portion of the illumination area is formed by a partial annulus, The first predetermined cross section is a cross section that includes the central axis of the front end cover and intersects the light guide output surface. In at least one of the first predetermined cross sections, the following conditional expression (2) is satisfied: 0≤(hA×n 2 ) / r≤1.36 (2) Here, The local annulus is a surface obtained by cutting a part of the annulus. The torus is the surface of a rotating body formed when a circle and a straight line that does not intersect the circle exist on a plane and the circle is rotated about the straight line as an axis. The rotated circle is called a small circle. hA is the distance between the first and second intersection points, The first intersection point is the intersection point of a straight line passing through the center of the small circle and parallel to the central axis and the light guide member exit surface. The second intersection point is an intersection point between the light ray passing through the boundary between the first plane and the curved surface and the light ray parallel to the central axis between the light guide member exit surface and the illumination area and the light guide member exit surface. When the second intersection point is located between the first intersection point and the side surface, the sign of the value of the distance is set to be positive. n is the refractive index of the material of the front cover at the e-line, r is the radius of the small circle.

10. An endoscope system, characterized in that: have: The endoscope according to claim 1 or 9; and Image processing device.

Images