Endoscope illumination optical system, optical adapter, and endoscope

Abstract

To provide an endoscope illumination optical system and the like that can broaden a light distribution while decreasing an amount of reduction in an amount of emitting light.SOLUTION: An illumination optical system for an endoscope 3 has a rod lens 24 as an optical element. The optical element has a base end face 24b on which light is incident, and a tip end face 24a that emits the light. The tip end face 24a has a diffusion region DS that diffuses the emitting light. The diffusion region DS includes a plurality of concavity parts 31, and a plurality of peripheral regions sa surrounding each concavity part 31. Each concavity part 31 includes a plurality of inclined faces 31a, 31b and 31c that serves as a total reflection surface inclined with respect to the tip end face 24a. Each peripheral region sa includes a transmission face that, after passing the base end surface 24b, emits the light totally reflected by the total reflection surface, and the light not totally reflected by the total reflection surface.SELECTED DRAWING: Figure 11

Description

Technical Field

[0004]

[0001] The present invention relates to an illumination optical system for an endoscope, an optical adapter, and an endoscope, and particularly to an illumination optical system for an endoscope having an insertion portion to be inserted into a subject, an optical adapter, and an endoscope having the illumination optical system.

Background Art

[0002] Endoscopes are widely used in the industrial and medical fields. An endoscope has an insertion portion, and illumination light is emitted from the tip of the insertion portion. The reflected light of the illumination light from the subject is received by an observation window, and a subject image inside the subject is obtained as an endoscope image by acquiring the subject image.

[0003] An illumination optical system having an optical element for diffusing light is provided inside an optical adapter attached to the tip of the insertion portion or inside the tip of the insertion portion so that the illumination light has a desired light distribution angle.

[0004] A plurality of inclined surfaces are formed on the incident surface of the optical element, and the plurality of inclined surfaces diffuse light. Due to this diffusion, illumination light having a desired light distribution angle is emitted from the emission surface of the optical element. For example, in the optical element disclosed in Japanese Patent Application Laid-Open No. 2015-226712, a prism surface provided with a plurality of regularly formed prisms having a plurality of inclined surfaces is provided on the incident surface of the optical element.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0007] Therefore, the present invention aims to provide an endoscopic illumination optical system, an optical adapter, and an endoscope that can widen the light distribution while minimizing the reduction in the amount of emitted light. [Means for solving the problem]

[0008] An endoscopic illumination optical system according to one aspect of the present invention is an endoscopic illumination optical system having an insertion portion inserted into a subject, and comprising an optical element having an incident surface into which light is incident as incident light and an exit surface from which the light is emitted as illumination light, wherein the exit surface has a diffusion region for diffusing the emitted light, the diffusion region has a plurality of recesses and a plurality of peripheral regions arranged on the exit surface, each recess has a plurality of total reflection surfaces inclined with respect to the exit surface for total internal reflection of the incident light, at least one of the plurality of total reflection surfaces is inclined at a first angle with respect to the exit surface, and each peripheral region is Opening of each of the recesses It is formed to surround the surface and has a transmitting surface that transmits and emits I: reflected light that has been totally reflected by the totally reflecting surface after passing through the incident surface, and II: incident light that has not been totally reflected by the totally reflecting surface after passing through the incident surface.

[0009] An optical adapter according to one aspect of the present invention is an optical adapter that can be attached to the tip of an insertion part inserted into a subject, and has an optical element having an incident surface into which light is incident as incident light and an exit surface from which the light is emitted as illumination light, the exit surface has a diffusion region for diffusing the emitted light, the diffusion region has a plurality of recesses and a plurality of peripheral regions arranged on the exit surface, each recess has a plurality of total reflection surfaces that are inclined with respect to the exit surface and cause total internal reflection of the incident light, at least one of the plurality of total reflection surfaces is inclined at a first angle with respect to the exit surface, and each peripheral region is Opening of each of the recesses It is formed to surround the surface and has a transmitting surface that transmits and emits I: reflected light that has been totally reflected by the totally reflecting surface after passing through the incident surface, and II: incident light that has not been totally reflected by the totally reflecting surface after passing through the incident surface.

[0010] An endoscope according to one aspect of the present invention has an optical element having an incident surface into which light is incident as incident light and an exit surface from which the light is emitted as illumination light, wherein the exit surface has a diffusion region for diffusing the emitted light, the diffusion region has a plurality of recesses and a plurality of peripheral regions arranged on the exit surface, each recess has a plurality of total reflection surfaces that are inclined with respect to the exit surface and cause total internal reflection of the incident light, at least one of the plurality of total reflection surfaces is inclined with respect to the exit surface at a first angle, and each peripheral region is Opening of each of the aforementioned recesses The endoscopic illumination optical system is formed to surround the object and has a transmissive surface that transmits and emits I: reflected light that has been totally reflected by the totally reflecting surface after passing through the incident surface, and II: incident light that has not been totally reflected by the totally reflecting surface after passing through the incident surface, and an insertion part that is inserted into the subject. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an endoscopic illumination optical system, an optical adapter, and an endoscope that can widen the light distribution while reducing the amount of light emitted. [Brief explanation of the drawing]

[0012] [Figure 1]This is a configuration diagram showing the configuration of an endoscope device according to an embodiment of the present invention. [Figure 2] This is a perspective view of the tip portion to which an optical adapter is attached, according to an embodiment of the present invention. [Figure 3] This is a cross-sectional view of the tip portion to which an optical adapter is attached, according to an embodiment of the present invention. [Figure 4] This is a perspective view of the tip portion to which an optical adapter is attached, according to an embodiment of the present invention, in which the shape of the illumination window is ring-shaped. [Figure 5] This is a cross-sectional view of the tip portion to which an optical adapter is attached, according to an embodiment of the present invention, in which the shape of the illumination window is ring-shaped. [Figure 6] This is a diagram of a rod lens viewed from the tip side, according to an embodiment of the present invention. [Figure 7] This is a perspective view of the tip portion of a rod lens, as seen from the oblique tip side, according to an embodiment of the present invention. [Figure 8] This is a diagram of a cylindrical rod lens viewed from the tip side, according to an embodiment of the present invention. [Figure 9] This is a diagram illustrating the shape of a recess according to an embodiment of the present invention. [Figure 10] This is a cross-sectional view showing the cross-sectional shape of a recess according to an embodiment of the present invention. [Figure 11] This is a diagram illustrating the light transmission region of each recess according to an embodiment of the present invention. [Figure 12] This is a diagram illustrating the peripheral region from which totally reflected light is emitted, according to an embodiment of the present invention. [Figure 13] This is a diagram illustrating a peripheral region having an inclined surface according to an embodiment of the present invention. [Figure 14] This is a diagram illustrating the direction of light emission according to an embodiment of the present invention. [Figure 15] This is a diagram illustrating the position of the deepest part of the recess, according to Modification 1 of the embodiment of the present invention. [Figure 16] This is a diagram illustrating a recess according to a modified example 2 of the present invention. [Figure 17] It is a diagram for explaining the position of the deepest part of a concave portion where the deepest part of the concave portion is displaced from the centroid of a square, which pertains to Modification 2 of the embodiment of the present invention. [Figure 18] It is a diagram for explaining a concave portion, which pertains to Modification 3 of the embodiment of the present invention. [Figure 19] It is a diagram for explaining a concave portion, which pertains to Modification 3 of the embodiment of the present invention. [Figure 20] It is a plan view of an inclined surface and a part of a peripheral region, which pertains to Modification 3 of the embodiment of the present invention. [Figure 21] It is a diagram for explaining the configuration on the optical path of illumination light in an optical adapter, which pertains to Modification 7 of the embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0014] In each of the drawings used in the following description, in order to make each component recognizable on the drawing, the scales are different for each component. The present invention is not limited only to the quantity of the components described in these drawings, the shape of the components, the ratio of the sizes of the components, and the relative positional relationship of each component. (Configuration of Endoscope Device)

[0015] FIG. 1 is a configuration diagram showing the configuration of an endoscope device according to the present embodiment.

[0016] As shown in FIG. 1, the endoscope device 1 is configured to include a device main body 2 having functions such as a video processor, and an endoscope 3 connected to the device main body 2. The device main body 2 has a display unit 4 such as a liquid crystal panel (LCD) on which an endoscope image, an operation menu, etc. are displayed. A touch panel may be provided on this display unit 4.

[0017] The endoscope 3 is composed of an insertion section 5, which is an endoscope insertion part inserted into the subject, an operating section 6 connected to the base end of the insertion section 5, and a universal cord 7 extending from the operating section 6. The endoscope 3 is detachable from the device body 2 via the universal cord 7.

[0018] The insertion portion 5 is composed of a tip portion 11, a curved portion 12, and a long, flexible portion 13, in that order from the tip side. The curved portion 12 is connected to the base end of the tip portion 11 and is configured to bend freely in directions such as up, down, left, and right. The flexible portion 13 is connected to the base end of the curved portion 12 and is flexible.

[0019] As indicated by the arrow, a direct-viewing optical adapter 10 can be detachably attached to the tip 11. For example, by attaching the direct-viewing optical adapter 10 to the tip 11, the endoscope 3 becomes a direct-viewing endoscope. In other words, the optical adapter 10 can be attached to the tip 11 of the insertion section 5 of the endoscope 3. The optical adapter 10 is attached according to the object to be examined, the purpose of the examination, etc. Therefore, the endoscope device 1 can also be used without attaching the optical adapter 10 to the tip 11. Note that the optical adapter 10 is not limited to direct viewing; it may also be for side viewing or strabismus.

[0020] The control unit 6 is equipped with a bending joystick 6a that bends the bending section 12 in the up, down, left, and right directions. By tilting the bending joystick 6a, the user can bend the bending section 12 in the desired direction. In addition to the bending joystick 6a, the control unit 6 is also equipped with various operation buttons that control the functions of the endoscope, such as a freeze button, a bending lock button, and a record instruction button.

[0021] Furthermore, if the display unit 4 is equipped with a touch panel, the user may use the touch panel to instruct various operations on the endoscope device 1.

[0022] The display unit 4 of the main body 2 displays the endoscopic image captured by the image sensor 23 (Figures 3 and 5) of the imaging unit located in the tip section 11. The main body 2 also contains various circuits, such as a control unit (not shown) for image processing and various controls, and a recording device (not shown) for recording processed images into memory.

[0023] Figure 2 is a perspective view of the tip portion 11 with the optical adapter 10 attached. Figure 3 is a cross-sectional view of the tip portion 11 with the optical adapter 10 attached. Figure 3 shows a cross-section of the tip portion 11 along the longitudinal axis O of the insertion portion 5. In Figure 3, the left side of the dotted line is the optical adapter 10, and the right side of the dotted line is the tip portion 11.

[0024] The optical adapter 10 has a cylindrical shape. The tip surface 10a of the optical adapter 10 is provided with an observation window 21 and an illumination window 22. When the optical adapter 10 is viewed from the tip side, the observation window 21 and the illumination window 22 have a partial circular shape. In particular, the illumination window 22 has an elongated semicircular shape.

[0025] The observation window 21 is formed by a cover glass 21a. The cover glass 21a also serves as a concave lens for the observation window. Behind the cover glass 21a, lenses constituting the lens group 21b that make up the observation optical system are provided within the housing 10b of the optical adapter 10.

[0026] The tip portion 11 of the insertion portion 5 has a hard tip member (not shown), and within this hard tip member are a lens 21c and an image sensor 23 that constitute the observation optical system. The image sensor 23 is, for example, a CCD image sensor or a CMOS image sensor. When the optical adapter 10 is attached to the tip portion 11 of the insertion portion 5, the lens in the optical adapter 10 and the lens in the tip portion 11 form an imaging optical system, i.e., an observation optical system, for the image sensor 23. Thus, the cover glass 21a, lens group 21b, and lens 21c constitute the observation optical system. A signal line 23a extends from the image sensor 23. The signal line 23a is connected to a circuit board inside the main body 2 of the device.

[0027] The illumination window 22 emits illumination light. Reflected light from the subject enters the observation window 21. The light from the subject forms an image of the subject on the imaging surface of the image sensor 23 via the observation optical system.

[0028] The lighting window 22 is composed of a cover glass 22a. The cover glass 22a has two panes of glass 22a1 and 22a2. The two panes of glass 22a1 and 22a2 are bonded together with adhesive.

[0029] For example, the base end face of glass 22a1 is a textured surface (shown by a dotted line). The tip end face of glass 22a1 is flat. Both the base end face and tip end face of glass 22a2 are flat. The two pieces of glass 22a1 and 22a2 are bonded together with adhesive, with the textured surface in between. The textured surface randomly diffuses the light, eliminating the unevenness in light distribution that occurs with the regularity of light distribution of the diffusion element having a diffusion structure described later. For example, the refractive index of both glass 22a1 and 22a2 is 1.52, and the refractive index of the adhesive is 1.56. By using materials with slightly different refractive indices for glass 22a1, 22a2 and the adhesive, unevenness in light distribution is eliminated while preventing excessive scattering. Note that if ensuring sufficient light intensity is prioritized over eliminating unevenness in light distribution, the textured surface does not need to be provided on the base end face of glass 22a1.

[0030] Light incident on the base end face of glass 22a2 exits from the front end face of glass 22a1.

[0031] The cover glass 22a may be arranged so that glass 22a1 and glass 22a2 are arranged in that order from the base end. In that case, the glasses 22a1 and 22a2 are arranged so that an air layer is formed between the glass 22a2 on the tip end side and the glass 22a1 on the base end side.

[0032] A partially cylindrical rod lens 24 is disposed inside the housing 10b of the optical adapter 10, behind the cover glass 22a. The rod lens 24 is made of transparent glass or plastic. A light guide 25, which is a bundle of optical fibers, is disposed inside the insertion section 5. The tip surface of the light guide 25 is positioned on the tip section 11. When the optical adapter 10 is attached to the tip section 11, the tip surface of the light guide 25 faces the base end surface 24b of the rod lens 24.

[0033] Light from a light source inside the device body 2 is incident on the base end surface of the light guide 25. Light emitted from the tip surface of the light guide 25 is incident on the base end surface 24b of the rod lens 24. Light incident on the base end surface 24b of the rod lens 24 passes inside the rod lens 24 and is emitted from the tip surface 24a of the rod lens 24, but the tip surface 24a of the rod lens 24 has a diffusion structure that diffuses the emitted light.

[0034] In other words, the rod lens 24 is an optical element having a base end surface 24b as an incident surface into which light enters as incident light, and a front end surface 24a as an exit surface from which light is emitted as illumination light.

[0035] In this case, endoscope 3 is a straight-viewing endoscope, and the proximal end surface 24b, which is the light incidence surface of the rod lens 24, and the tip surface 24a, which is the light emission surface, are parallel.

[0036] Diffused light from the tip surface 24a of the rod lens 24 enters the cover glass 22a and exits from the illumination window 22.

[0037] The endoscope 3 shown in Figures 2 and 3 has an elongated, semi-circular illumination window 22, but the illumination window 22 may also have a ring shape.

[0038] Figure 4 is a perspective view of the tip portion 11A to which the optical adapter 10A is attached, with the illumination window 22 having a ring shape. Figure 5 is a cross-sectional view of the tip portion 11A to which the optical adapter 10A is attached, with the illumination window 22 having a ring shape. Figure 5 shows a cross-section of the tip portion 11 along the longitudinal axis O of the insertion portion 5. In Figure 5, the left side of the dotted line is the optical adapter 10A, and the right side of the dotted line is the tip portion 11A.

[0039] The optical adapter 10A in Figures 4 and 5 has a cylindrical shape. The tip surface 10a of the optical adapter 10A is provided with an observation window 21A and an illumination window 22A. The observation window 21A has a circular shape when viewed from the tip side of the optical adapter 10A. The illumination window 22A has a ring shape when viewed from the tip side of the optical adapter 10A.

[0040] The observation window 21A is made up of a cover glass 21Aa. Behind the cover glass 21Aa, lenses constituting the lens group 21b are provided within the housing 10b of the optical adapter 10.

[0041] The tip portion 11A of the insertion portion 5 has a hard tip member (not shown), and the lens 21c and image sensor 23 that constitute the observation optical system are built into this hard tip member. In other words, when the optical adapter 10 is attached to the insertion portion 5, the cover glass 21a, lens group 21b, and lens 21c constitute the observation optical system.

[0042] The lighting window 22A is composed of a ring-shaped cover glass 22Aa. The cover glass 22Aa has two ring-shaped glass panes 22Aa1 and 22Aa2.

[0043] For example, the base end face of glass 22Aa1 is a textured surface (shown by a dotted line). The tip end face of glass 22Aa1 is flat. Both the base end face and tip end face of glass 22Aa2 are flat. The two pieces of glass 22Aa1 and 22Aa2 are bonded together with adhesive, sandwiching each other's textured surfaces. For example, the refractive indices of both glass 22Aa1 and 22Aa2 are 1.88, and the refractive index of the adhesive is 1.56. By using materials with slightly different refractive indices for glass 22Aa1, 22Aa2 and the adhesive, excessive scattering is prevented while eliminating uneven light distribution.

[0044] In the cover glass 22Aa, light incident on the base end face of glass 22Aa2 exits from the front end face of glass 22Aa1.

[0045] The cover glass 22Aa may be arranged in the order of glass 22Aa1 and glass 22Aa2 from the base end. In that case, glass 22Aa1 and glass 22Aa2 are arranged separately so that an air layer is formed between glass 22Aa2 on the tip end side and glass 22Aa1 on the base end side.

[0046] Behind the cover glass 22Aa, a cylindrical rod lens 24A is disposed within the housing 10b of the optical adapter 10A. A light guide 25A, which is a bundle of optical fibers, is disposed within the insertion section 5. The tip of the light guide 25A has a ring-shaped tip surface and is positioned on the tip section 11A. When the optical adapter 10A is attached to the tip section 11A, the tip surface of the light guide 25A faces the base end surface 24Ab of the rod lens 24A.

[0047] Light from the light source inside the device body 2 is incident on the base end surface of the light guide 25A. Light emitted from the tip surface of the light guide 25A is incident on the base end surface 24Ab of the rod lens 24A. Light incident on the base end surface 24Ab of the rod lens 24A passes through the rod lens 24A and is emitted from the tip surface 24Aa of the rod lens 24A. The tip surface 24Aa of the rod lens 24A has a diffusion structure that diffuses the emitted light.

[0048] In other words, the rod lens 24A is an optical element having a base end surface 24Ab as an incident surface into which light is incident as incident light, and a front end surface 24Aa as an exit surface from which light is emitted as illumination light.

[0049] Diffused light from the tip surface 24Aa of the rod lens 24A enters the cover glass 22Aa and exits from the illumination window 22.

[0050] As described above, the rod lens 24 or 24A has a diffusion structure on its tip surface 24a or 24Aa. Next, the diffusion structure will be explained.

[0051] In the example described above, rod lenses 24 and 24A, having a diffusion structure on their tip surfaces 24a and 24Aa, are provided within the optical adapters 10 and 10A. However, the example is not limited to this, and rod lenses 24 and 24A may also be provided within the tip portions 11 and 11A of the insertion portion 5 of the endoscope 3, which can observe a subject without the optical adapters 10 and 10A. That is, rod lenses 24 and 24A with a diffusion structure may be provided behind the illumination windows 22 and 22A of the tip portions 11 and 11A (on the proximal end side in the case of a direct-viewing endoscope).

[0052] Next, we will describe the diffusion structure of the rod lens 24.

[0053] Figure 6 is a view of the rod lens 24 from the tip side. Figure 7 is a perspective view of the tip portion of the rod lens 24 from the oblique tip side.

[0054] Multiple recesses 31 are formed on the tip surface 24a of the rod lens 24. Each recess 31 has a polygonal pyramidal shape. Here, the opening of each recess 31 is an equilateral triangle, and each recess 31 has a regular triangular pyramidal shape. A peripheral region sa, indicated by a dashed line, is provided around the opening of each recess 31 on the tip surface 24a.

[0055] In other words, the tip surface 24a, which is the emission surface, has a diffusion region DS that diffuses the emitted light. The diffusion region DS has a plurality of recesses 31 and a plurality of peripheral regions sa arranged on the tip surface 24a.

[0056] Figure 8 is a view of the cylindrical rod lens 24A from the tip side. Multiple recesses 31 having the same shape as those in Figures 6 and 7 are formed on the tip surface 24Aa of the rod lens 24A, and a peripheral region sa, indicated by a dashed line, is provided around the opening of each recess 31.

[0057] Next, the shape of the recess 31 will be described.

[0058] Figure 9 is a diagram illustrating the shape of the recess 31. The recess 31 has a shape into which an object OB, which is shaped like a regular triangular pyramid, fits. Object OB has a regular triangular pyramid shape with a cross-sectional shape parallel to the base BP being an equilateral triangle. The base BP of object OB has an equilateral triangle shape. The base BP has three vertices BPa and three edges BPa1. Object OB has a fourth vertex BPb and three edges BPb1 connecting the three vertices BPa and vertex BPb.

[0059] When object OB is turned upside down and fitted into the recess 31, the base BP of the equilateral triangle becomes flush with the tip surfaces 24a and 24Aa of the rod lenses 24 and 24A (the following explanation will use rod lens 24 as an example, but the same applies to rod lens 24A).

[0060] In other words, as shown in Figure 9, each recess 31 has a shape such that when the triangular pyramidal object OB is inverted and fitted into the recess 31, the base surface BP is parallel to the tip surface 24a of the rod lens 24.

[0061] Therefore, the recess 31 has three inclined surfaces 31a, 31b, and 31c. Each of the inclined surfaces 31a, 31b, and 31c has an isosceles triangle (or equilateral triangle) when viewed from a direction perpendicular to each of the inclined surfaces 31a, 31b, and 31c. The point 33 where the boundaries 32a, 32b, and 32c of two adjacent inclined surfaces meet is the deepest part of the recess 31.

[0062] Each recess 31 has a pyramidal shape (regular triangular pyramid) with its deepest point at the vertex, and its base BP is an opening of a regular polygon (in this case, an equilateral triangle). When the tip surface 24a is viewed from a direction perpendicular to the tip surface 24a, the vertex point 33 is located at the centroid of the regular polygon (in this case, an equilateral triangle).

[0063] Boundary line 32a faces inclined surface 31a, boundary line 32b faces inclined surface 31b, and boundary line 32c faces inclined surface 31c. The angles of each inclined surface 31a, 31b, and 31c with respect to the tip surface 24a are equal.

[0064] In this case, the deepest part of the recess 31 is point 33, but it may also be a flat surface parallel to the tip surface 24a. In that case, the recess 31 has a truncated triangular shape.

[0065] A peripheral region sa is provided so as to surround the opening of the recess 31. The peripheral region sa is part of the tip surface 24a, which is the ejection surface.

[0066] Figure 10 is a cross-sectional view showing the cross-sectional shape of the recess 31. The lower part of Figure 10 shows a cross-section of the recess 31 along a plane LL that includes the boundary line 32a and is perpendicular to the tip surface 24a. When the material of the rod lens 24 is glass and the refractive index n is in the range of 1.4 to 2.0, the inclination angle α of the inclined surface 31a with respect to the direction perpendicular to the tip surface 24a in the plane LL is an angle in the range of 5 degrees or more and less than 20 degrees. The inclination angles of the other inclined surfaces 31b, 31c are the same as the inclination angle α of inclined surface 31a, and are angles in the range of 5 degrees or more and less than 20 degrees. In other words, the angle of each inclined surface 31a, 31b, ... with respect to the tip surface 24a (the first angle) is an angle in the range of 85 degrees or less and greater than 70 degrees, i.e., 70° < (90-α) ≤ 85°.

[0067] At each of the inclined surfaces 31a, 31b, and 31c, a portion of the light traveling from the base end surface 24b of the rod lens 24 towards the tip surface 24a undergoes total internal reflection. The totally reflected light L1 exits from the peripheral region sa of the recess 31, which is the transmission region. In other words, each recess 31 has multiple (in this case, three) inclined surfaces 31a, 31b, and 31c, which are total internal reflection surfaces that cause incident light to undergo total internal reflection. Each of the inclined surfaces 31a, 31b, and 31c is a total internal reflection surface that is inclined at an angle (90-α) with respect to the tip surface 24a, which is the exit surface.

[0068] Each recess 31 has an equilateral triangle opening. The opening has three sides EL. A peripheral region sa is provided so as to surround the three sides EL of the opening of each recess 31. Each peripheral region sa is formed so as to surround multiple (in this case, three) inclined surfaces 31a, 31b, and 31c, and is a transmitting surface that transmits and emits reflected light that has been totally reflected at each inclined surface 31a, 31b, and 31c, as well as light that has not been totally reflected at the inclined surfaces 31a, 31b, and 31c from the base end surface 24b.

[0069] As shown in Figures 6 to 8, multiple recesses 31 and surrounding regions sa, as shown in Figure 9, are provided on the tip surface 24a, which is the exit surface, thereby forming a diffusion region DS.

[0070] In other words, each recess 31 has a triangular pyramidal shape with its deepest point at vertex BPb and an opening at its triangular base BP, and the multiple total reflection surfaces are the three planes (inclined surfaces 31a, 31b, and 31c) excluding the base BP of the triangular pyramidal shape.

[0071] In Figure 6, the multiple recesses 31 are formed at equal intervals on the tip surface 24a of the rod lens 24 such that one of the three sides EL is parallel to the straight portion 24c of the partially circular tip surface 24a. Furthermore, the multiple recesses 31 are arranged on the tip surface 24a such that the two adjacent sides EL of two adjacent recesses 31 are parallel to each other, and the distance between all the adjacent sides EL of two adjacent recesses 31 is equal.

[0072] Figure 11 is a diagram illustrating the light transmission region of each recess 31. Figure 11 is a plan view of the recess 31 when the tip surface 24a is viewed from a direction perpendicular to the tip surface 24a.

[0073] As described above, three recesses 31 (shown by dashed lines) are formed around one recess 31 (shown by a solid line) such that the two adjacent sides EL of two adjacent recesses 31 are parallel. On the tip surface 24a, the area other than the multiple recesses 31 constitutes multiple peripheral regions sa.

[0074] Figure 12 is a diagram illustrating the peripheral region sa from which totally reflected light is emitted. Light totally reflected at one inclined surface 31a of one recess 31 is emitted from a peripheral region sa (shown by the shaded area) having a width (d / 2). Light that does not undergo totally reflected at the inclined surface 31a (or 31b or 31c) and reaches the peripheral region sa directly from the base end surface 24b is also emitted from the peripheral region sa (shown by the shaded area).

[0075] The peripheral region sa surrounding each inclined surface 31a, 31b, and 31c is a surface parallel to the tip surface 24a of the rod lens 24, but it may also have an inclined portion.

[0076] Figure 13 is a diagram illustrating the peripheral region sa1 having an inclined surface. The peripheral region sa1 is an inclined surface provided to surround the opening of each recess 31. Therefore, there are two inclined surfaces 34 between the two parallel sides EL of two adjacent recesses 31. The inclined surface provided to surround the opening of each recess 31 is the peripheral region sa1.

[0077] The two inclined surfaces 34 are formed symmetrically with respect to a plane that includes a line CL located at a distance (d / 2) from two adjacent sides EL and is perpendicular to the tip surface 24a. The angle β of the inclined surfaces 34 with respect to the tip surface 24a is 0° < β ≤ 25°. That is, the angle β of the inclined surfaces 34 is an angle greater than 0 degrees and less than or equal to 25 degrees with respect to the imaginary tip surface 24a of the rod lens 24. In other words, each peripheral region sa1 has an angle β (second angle) greater than 0 degrees and less than (90-α) with respect to the tip surface 24a. By providing two inclined surfaces 34 in the peripheral region sa1, the beam angle can be widened while suppressing the reduction in light intensity.

[0078] It is preferable that the light distribution of the illumination light emitted from the peripheral region sa, which is the light transmission region, be uniform overall.

[0079] In Figure 11, when viewing the tip surface 24a from a direction perpendicular to the tip surface 24a, let A be the projected area of ​​the inclined surface 31a onto the tip surface 24a (second area), let B be the projected area of ​​the inclined surface 31b onto the tip surface 24a (second area), and let C be the projected area of ​​the inclined surface 31c onto the tip surface 24a (second area). As shown in Figure 11, let D be the area (first area) of the peripheral region sa on the tip surface 24a within a distance (d / 2) from each side EL. The peripheral region sa has a triangular shape and lacks a central part which is the projected portion of the three inclined surfaces 31a, 31b, and 31c.

[0080] In other words, when the distance between the two parallel sides EL of two adjacent recesses 31 is d, the region enclosed by the imaginary line L2, which is at a distance of (d / 2) from each side EL, is the surrounding region sa (shown by the diagonal lines).

[0081] As shown in Figure 11, let the length of one side EL of the recess 31 be a, and the length of one side of the surrounding region sa be b.

[0082] In order to uniformize the two-dimensional light distribution of the illumination light emitted from the front end surface 24a, it is preferable that the ratio r of D to A (or B or C) is 1. If the ratio of D to A (or B or C) is 1, the amount of light emitted from the peripheral region sa by total reflection on each inclined surface 31a, 31b, 31c is equal to the amount of light directly emitted from the peripheral region sa without total reflection on each inclined surface 31a, 31b, 31c, and uniform illumination can be obtained.

[0083] However, in practical use, the ratio r may be in the range of (1 / 3) to 3 even if it is not 1. That is, it is preferable that (1 / 3) < r < 3. When the ratio r is outside this range, a bias occurs between the amount of light emitted from the peripheral region sa by total reflection on each inclined surface 31a, 31b, 31c and the amount of light directly emitted from the peripheral region sa without total reflection on each inclined surface 31a, 31b, 31c, and the two-dimensional light distribution becomes non-uniform, leading to uneven illumination.

[0084] That is, when the projected areas of each peripheral region sa and the front end surface of the inclined surface 31a (or 31b or 31c) on the front end surface 24a when viewed from a direction perpendicular to the front end surface 24a are D and A respectively, the ratio of D to A is preferably a value in the range greater than (1 / 3) and less than 3.

[0085] A, B, C, D are expressed by the following formulas (1) and (2). TIFF0007856440000001.tif25149TIFF0007856440000002.tif2591

[0086] From formulas (1) and (2), the following formula (3) holds. TIFF0007856440000003.tif28162

[0087] For example, in order to make A = D, from the following formula (4), (b / a) becomes formula (5). TIFF0007856440000004.tif2388TIFF0007856440000005.tif1870

[0088] Therefore, for example, to set (1 / 3) < (D / A) < 3, from the following equations (6) and (7) Equation (8) is obtained. TIFF0007856440000006.tif2385TIFF0007856440000007.tif2385TIFF0007856440000008.tif1888

[0089] Furthermore, for example, when the tip surface of the rod lens 24 is a ring-shaped tip surface 24Aa as shown in Figure 8, it is preferable that the pitch Ep of each recess 31 is within the range where the following equation (9) holds true. Φin is the inner diameter of the cylindrical rod lens 24A, and Φout is the outer diameter of the cylindrical rod lens 24A. TIFF0007856440000009.tif22144

[0090] As described above, multiple recesses 31 are formed on the tip surface 24a of the rod lens 24, and a peripheral region sa is provided around each recess 31. Therefore, light from the light guide 25 is diffused by each recess 31 on the tip surface 24a of the rod lens 24 and the peripheral region sa surrounding each recess 31. In particular, light that strikes the three inclined surfaces 31a, 31b, and 31c, which are the slopes of each recess 31, undergoes total internal reflection and is emitted from the peripheral region sa, which is the transmitted region, so the reduction in light intensity is extremely small. In addition, some of the light from the base end surface 24b of the rod lens 24 is emitted directly from the peripheral region sa without undergoing total internal reflection in the recesses 31.

[0091] In particular, due to the two adjacent recesses 31, light diffuses in six directions from the surrounding region sa. Figure 14 is a diagram illustrating the direction of light emission.

[0092] As shown in Figure 14, in two adjacent recesses 31, the light reflected by the respective inclined surfaces 31a, 31b, and 31c is emitted from the surrounding region sa in six directions D1, D2, D3, D4, D5, and D6, resulting in less unevenness in light distribution.

[0093] Furthermore, the shape of the opening of the recess 31 may be changed from an equilateral triangle to an isosceles triangle, a right triangle, or the like.

[0094] As described above, in this embodiment, the light reflected by each inclined surface 31a, 31b, and 31c undergoes total internal reflection and is emitted from the surrounding region sa. In the conventional technology, the light that undergoes total internal reflection becomes backlight and does not emit from the emission surface, leading to a loss of light intensity. However, with the above configuration, the light that undergoes total internal reflection can be emitted without leakage, reducing the loss of emitted light intensity. Furthermore, since the total internal reflection light is transmitted from the surrounding region sa, it is not necessary to reduce the angles of the inclined surfaces 31a, 31b, and 31c to reduce backlight, and the width of the beam angle can be maintained.

[0095] Therefore, according to the above-described embodiment, it is possible to provide an endoscopic illumination optical system that can widen the light distribution while reducing the amount of light emitted.

[0096] Next, a modified example of the above-described embodiment will be explained. (Variation 1)

[0097] In the embodiment described above, each recess 31 has a regular triangular pyramidal shape with its base facing upwards and its vertex downwards. Therefore, the deepest point 33 is located at the centroid of the equilateral triangle when the tip surface 24a is viewed from a direction perpendicular to the tip surface 24a. However, the deepest point of each recess may be located at a position offset from its centroid when the tip surface 24a is viewed from a direction perpendicular to the tip surface 24a.

[0098] Figure 15 is a diagram illustrating the position of the deepest part of the recess 31A in the modified example 1.

[0099] As shown in Figure 15, the deepest part of the recess 31A is located at point Q, which is offset from point P, the center of gravity.

[0100] Therefore, as shown in Figure 15, the inclination angles α1 and α2 of the two adjacent planes of the two adjacent recesses 31A are angles within the range of greater than 3 degrees and less than 20 degrees. In other words, 70° < (90 - α1) < 97° and 70° < (90 - α2) < 97°. The inclination angles α1 and α2 may be the same or different.

[0101] The light distribution can be adjusted by changing the position of the deepest part of the recess 31A. Alternatively, the light distribution can be adjusted by changing the inclination angle of each inclined surface 31a, 31b, and 31c of the recess 31A.

[0102] Therefore, the same effects as those of the above-described embodiment can be obtained by the modified example 1 as well. (Modification 2)

[0103] In the above-described embodiment and modification 1, the recesses 31 and 31A have a triangular pyramidal shape, but the recesses may also have a square pyramidal shape.

[0104] Figure 16 is a diagram illustrating the recess 31B related to the second modification.

[0105] As shown in Figure 16, each recess 31B has a shape such that when a regular square pyramidal object OB (not shown) is fitted into the recess 31B with its base facing upwards, the square base is parallel to the tip surface 24a of the rod lens 24.

[0106] Therefore, the recess 31B has four inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd. The four inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd form a square when viewed from a direction perpendicular to the tip surface 24a. The point 33B where the boundaries of four adjacent inclined surfaces meet is the deepest part of the recess 31B. The angles of each inclined surface 31Ba, 31Bb, 31Bc, and 31Bd with respect to the tip surface 24a are equal.

[0107] In other words, each recess 31B has a square pyramidal shape with its apex being the deepest part and its square base being an opening, and the multiple total reflection surfaces are the four planes (inclined surfaces 31Ba, 31Bb, 31Bc, 31Bd) excluding the base of the square pyramidal shape.

[0108] Each recess 31B has a square opening. The opening has four sides EL. A peripheral region sa (shown by diagonal lines) is provided to surround the opening of each recess 31B. Between two adjacent parallel sides EL of two adjacent recesses 31B, there is a transparent region with a width d1. The two peripheral regions sa of two adjacent recesses 31B constitute the transparent region between the two adjacent recesses 31B.

[0109] In Figure 16, when viewing the tip surface 24a from a direction perpendicular to the tip surface 24a, let A be the projected area of ​​the inclined surface 31Ba onto the tip surface 24a, B be the projected area of ​​the inclined surface 31Bb onto the tip surface 24a, C be the projected area of ​​the inclined surface 31Bc onto the tip surface 24a, and D be the projected area of ​​the inclined surface 31Bd onto the tip surface 24a. As shown in Figure 16, let E be the area of ​​the peripheral region sa on the tip surface 24a, within a distance (d1 / 2) from each side EL. The peripheral region sa has a quadrilateral shape and lacks a central part which is the projected portion of the four inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd.

[0110] In other words, when d1 is the distance between two parallel sides EL of two adjacent recesses 31B, the region enclosed by imaginary lines at a distance of (d1 / 2) from each side EL is the surrounding region sa (shown by the diagonal lines).

[0111] The inclination angles α3 of each inclined surface 31Ba, 31Bb, 31Bc, and 31Bd with respect to the tip surface 24a are angles in the range of 5° to 25°. In other words, the angle (90-α3) of each total reflective surface with respect to the tip surface 24a is an angle between less than 85° and greater than 65°, i.e., 65° < (90-α3) < 85°.

[0112] As shown in Figure 16, the length of side EL of the recess 31B is a1, and the length of one side of the surrounding region sa is b1.

[0113] In order to make the two-dimensional light distribution of the illumination light emitted from the tip surface 24a uniform, it is preferable that the ratio of E to A (or B or C or D) is in the range of (1 / 3) to 3, as described above.

[0114] For example, the following equation (11) holds true for A and E. TIFF0007856440000010.tif18141

[0115] From equation (11), the following equation (12) holds true. TIFF0007856440000011.tif25101

[0116] Therefore, (1 / 3) < (E / A) < 3 means that the following relationship (13) holds. TIFF0007856440000012.tif2082

[0117] Equation (14) can be obtained from equation (13). TIFF0007856440000013.tif2082

[0118] From equation (14), the following equation (15) holds true. TIFF0007856440000014.tif2167

[0119] Therefore, when the recess is in the shape of a square pyramid, it is preferable that the transparent region satisfies the relationship in equation (15) above.

[0120] Therefore, the same effects as those of the embodiment described above can be obtained by the modified example 2 as well.

[0121] In addition, in this modification 2, as in modification 1, the deepest point may be located at a position offset from its center of gravity. That is, point 33C at the deepest part of the square pyramidal recess may be located at a position offset from the center of gravity of the square.

[0122] Figure 17 is a diagram illustrating the position of the deepest part of the recess 31C, which is offset from the centroid of the square. As shown in Figure 17, point 33C, the deepest point of the recess 31C, is located offset from the centroid. The lower part of Figure 17 shows a cross-section of the tip surface 24a along the dashed line LL in the upper part.

[0123] Therefore, as shown in Figure 17, the inclination angles α4 and α5 of the two adjacent inclined surfaces of the two adjacent recesses 31C are angles within the range of 3 to 20 degrees. In other words, 80° < (90 - α4) < 97° and 80° < (90 - α5) < 97°. The inclination angles α4 and α5 may be the same or different.

[0124] In the case of Figure 17, when viewing the tip surface 24a from a direction perpendicular to the tip surface 24a, if the projected areas of the inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd onto the tip surface 24a are A, B, C, and D respectively, then the following equations (16) and (17) hold. TIFF0007856440000015.tif1362TIFF0007856440000016.tif1875

[0125] By changing the position of the deepest part of the recess 31C, the light distribution in four directions can be adjusted. Alternatively, the light distribution can be adjusted by changing the inclination angle of each inclined surface 31Ba, 31Bb, 31Bc, and 31Bd of the recess 31C.

[0126] Furthermore, the shape of the opening of the recess 31C may be changed from a square to a rectangle. By changing the shape of the opening of the recess 31C to a rectangle, the light distribution in four directions can be further adjusted. Also, the position of the deepest part of the rectangle may be shifted from the center of gravity.

[0127] Therefore, the same effects as those of the embodiment described above can be obtained by the modified example 2 as well. (Variation 3)

[0128] In the above-described embodiment and modification 1, the recesses 31 and 31A have a triangular pyramidal shape, and in modification 2, the recess 31B has a square pyramidal shape, however, the recesses may also have a hexagonal pyramidal shape.

[0129] Figures 18 and 19 are diagrams illustrating the recess 31D related to Modification 3.

[0130] As shown in Figure 18, each recess 31D has a shape such that when a regular hexagonal pyramidal object OB (not shown) is fitted into the recess 31D with its base facing upwards, the hexagonal base is parallel to the tip surface 24a of the rod lens 24.

[0131] Therefore, each recess 31D has six inclined surfaces 31Da, 31Db, 31Dc, 31Dd, 31De, and 31Df. The six inclined surfaces 31Da, 31Db, 31Dc, 31Dd, 31De, and 31Df form a regular hexagon when viewed from a direction perpendicular to the tip surface 24a. The point 33D where the six boundary lines of two adjacent inclined surfaces meet is the deepest part of each recess 31D. The angles of each inclined surface 31Da, 31Db, 31Dc, 31Dd, 31De, and 31Df with respect to the tip surface 24a are equal.

[0132] In other words, each recess 31D has a hexagonal pyramidal shape with its vertex being the deepest part and its base being a regular hexagon with an opening, and the multiple total reflective surfaces are the six planes (inclined surfaces 31Da, 31Db, 31Dc, 31Dd, 31De, 31Df) excluding the base of the hexagonal pyramidal shape.

[0133] Each recess 31D has a regular hexagonal opening. The opening has six sides EL. A peripheral region sa is provided on the tip surface 24a so as to surround the opening of each recess 31D.

[0134] As shown in Figure 19, there is a transparent region with a width d2 between the two parallel sides EL of two adjacent recesses 31D. The right-hand side of Figure 19 shows a cross-section of the tip surface 24a along the dashed line LL1 on the left side.

[0135] In Figures 18 and 19, when the tip surface 24a is viewed from a direction perpendicular to the tip surface 24a, let A be the projected area of ​​the inclined surface 31Da onto the tip surface 24a, B be the projected area of ​​the inclined surface 31Db onto the tip surface 24a, C be the projected area of ​​the inclined surface 31Dc onto the tip surface 24a, D be the projected area of ​​the inclined surface 31Dd onto the tip surface 24a, E be the projected area of ​​the inclined surface 31De onto the tip surface 24a, and F be the projected area of ​​the inclined surface 31Df onto the tip surface 24a. As shown in Figure 19, let G be the area of ​​the peripheral region sa on the tip surface 24a within a distance (d² / 2) from each side EL. The peripheral region sa has a hexagonal shape and lacks a central part which is the projected portion of the six inclined surfaces 31Da, 31Db, 31Dc, 31Dd, 31De, and 31Df.

[0136] In other words, when the distance between two parallel sides EL of two adjacent recesses 31D is d2, the region enclosed by imaginary lines at a distance of (d2 / 2) from each side EL is the surrounding region sa (shown by the diagonal lines).

[0137] The inclination angle α6 of each inclined surface 31Da, 31Db, 31Dc, 31Dd, 31De, and 31Df with respect to the tip surface 24a is in the range of 3° to 20°. In other words, the angle (90-α6) of each total reflective surface with respect to the tip surface 24a is in the range of less than 87° and greater than 70°, i.e., 70° < (90-α6) < 87°.

[0138] Figure 20 is a plan view of the inclined surface 31Dc and a portion of the surrounding region sa. The length of one side EL of the recess 31D is denoted as a2, and the length of one side of the surrounding region sa is denoted as b2.

[0139] For example, the area C of the projection surface of the inclined surface 31Dc onto the tip surface 24a, and the area G1 of a portion of the surrounding region sa near the inclined surface 31Dc are given by equations (21) and (22), respectively. TIFF0007856440000017.tif28124TIFF0007856440000018.tif2390

[0140] Then, from equations (21) and (22), the ratio of the area G of the surrounding region sa to the area C of the projection surface of the inclined surface 31Dc onto the tip surface 24a is given by the following equation (23). TIFF0007856440000019.tif46168

[0141] In order to make the two-dimensional light distribution of the illumination light emitted from the tip surface 24a uniform, it is preferable that the ratio of G to C (or A or B or D or E or F) is in the range of (1 / 3) to 3, as described above.

[0142] From equation (23), we can obtain equations (24), (25), and (26). TIFF0007856440000020.tif21111TIFF0007856440000021.tif21111TIFF0007856440000022.tif21111

[0143] Therefore, when the recess is hexagonal pyramidal in shape, it is preferable that the surrounding region sa satisfies the relationship in equation (26) above.

[0144] Therefore, the same effects as those of the above-described embodiment can be obtained by the modified example 3.

[0145] In this modification 3, as in modification 1, the deepest point may be located at a position offset from its center of gravity. That is, point 33D at the deepest point of the hexagonal pyramidal recess may be located at a position offset from the center of gravity of the square. (Modification 4)

[0146] In the above-described embodiment and modification 1, the recesses 31 and 31A have a triangular pyramidal shape; in modification 2, the recesses 31B and 31C have a square pyramidal shape; and in modification 3, the recess 31D has a hexagonal pyramidal shape. However, the recesses may also have a conical shape or a polygonal pyramidal shape close to a cone.

[0147] The same effects as those of the above-described embodiment can be obtained by the 4th modified example. (Variation 5)

[0148] In the embodiments and modifications described above, the multiple inclined surfaces 31a etc. of each recess and the surrounding region sa are separated by three or more sides EL of the opening of the recess. However, a flat or curved portion connecting each inclined surface 31a etc. and the surrounding region sa may be provided between each inclined surface 31a etc. and the surrounding region sa.

[0149] For example, a planar portion formed by chamfering the edge EL may be located between each inclined surface and the surrounding region sa. Furthermore, multiple planar portions may be located between each inclined surface and the surrounding region sa.

[0150] Alternatively, a curved surface with a gentle curve connecting each inclined surface 31a, etc., to the surrounding region sa may be located between each inclined surface and the surrounding region sa.

[0151] The same effects as those of the above-described embodiment can be obtained by the modified example 5. (Experimental variation 6)

[0152] In the embodiments and modifications described above, the shapes of the multiple recesses formed on the tip surface 24a are the same. However, the invention is not limited to this, and recesses of different shapes may be mixed and formed on the tip surface 24a. For example, the tip surface 24a, which is the discharge surface, may be provided with two recess regions: one region in which multiple triangular pyramidal recesses 31 are formed as diffusion regions DS, and another region in which multiple square pyramidal recesses 31B are formed as diffusion regions DS, so that multiple recess regions with different recess shapes are mixed on the tip surface 24a.

[0153] The same effects as those of the above-described embodiment can be obtained by the modified example 6. (Example 7)

[0154] In the embodiments described above and each of the modifications 1 to 6, a diffusion structure (diffusion region DS that diffuses emitted light) is provided on the tip surfaces 24a and 24Aa of the rod lenses 24 and 24A. However, the diffusion structure may also be provided on a component separate from the rod lenses 24 and 24A.

[0155] Figure 21 is a diagram illustrating the configuration of the optical path of illumination light within the optical adapter 10, relating to Modification 7. In the following description, a configuration having a cover glass 22a and a rod lens 24 will be used as an example, but the same applies to a configuration having a cover glass 22Aa and a rod lens 24A.

[0156] For example, a plate member 26 is placed between the cover glass 22a and the rod lens 24. In Figure 21, the plate member 26 is positioned at a distance from the rod lens 24, but the plate member 26 may also be joined to the rod lens 24 using an adhesive or the like.

[0157] The plate member 26 is molded from, for example, transparent glass or transparent plastic. A diffusion structure is formed on the leading edge surface 26a of the plate member 26 to diffuse the emitted light. As described above, the diffusion structure is configured as a diffusion region DS having a plurality of recesses 31 (or recesses 31A, 31B, 31C, 31D, etc.) and a plurality of peripheral regions sa (or peripheral region sa1). Multiple plate members 26 may be manufactured simultaneously by cutting them from a large sheet of material on which the diffusion structure is formed.

[0158] Light incident from the light guide 25 onto the base end surface 24b of the rod lens 24 passes through the rod lens 24, exits from the tip surface 24a of the rod lens 24, and is incident on the base end surface 26b of the plate member 26. The light that has passed through the plate member 26 is diffused by the diffusion region DS and exits from the tip surface 26a, and is incident on the cover glass 22a.

[0159] In modification 7, a textured surface (shown by a dotted line) may be provided on the cover glass 22a to eliminate uneven light distribution, or it may be omitted if ensuring sufficient light output is prioritized over eliminating uneven light distribution.

[0160] The same effects as those of the above-described embodiment can be obtained with the modified example 7, and there is no need to process the tip surface 24a of the rod lens 24 to provide a diffusion region DS, allowing the use of an existing rod lens 24. (Variation 8)

[0161] In the embodiments described above and each of the modifications 1 to 7, an elongated, semi-circular lighting window 22 as shown in Figure 2, or a ring-shaped lighting window 22A as shown in Figure 4, is provided. However, the shape of the lighting window is not limited to these. Various shapes of lighting windows, such as circular, polygonal, or combinations of multiple shapes, may be used as lighting windows. Furthermore, the number of lighting windows is not limited to one, and multiple windows may be provided. For example, two circular lighting windows may be provided.

[0162] Modification 8 also provides the same effects as the embodiment described above, while increasing the flexibility of the lighting window layout.

[0163] In the embodiments and variations 1 to 8 described above, the endoscope is a straight-viewing endoscope, but the embodiments and variations described above can also be applied to side-viewing or oblique-viewing endoscopes.

[0164] As described above, according to the embodiments and modifications described above, it is possible to realize an endoscopic illumination optical system, optical adapter, and endoscope that can widen the light distribution while reducing the amount of light emitted.

[0165] The present invention is not limited to the embodiments described above, and various changes and modifications are possible without altering the essence of the invention. [Explanation of Symbols]

[0166] 1 Endoscope device, 2 Device body, 3 Endoscope, 4 Display unit, 5 Insertion unit, 6 Control unit, 6a Curved joystick, 7 Universal cord, 10, 10A Optical adapter, 10a Tip surface, 10b Housing, 11, 11A Tip section, 12 Curved section, 13 Flexible section, 21, 21A Observation window, 21Aa, 21a Cover glass, 21b Lens group, 22, 22A Illumination window, 22a, 22Aa Cover glass, 22a1, 22a2, 22Aa1, 22Aa2 Glass, 23 Image sensor, 23a Signal line, 24, 24A Rod lens, 24a, 24Aa Tip surface, 24b, 24Ab Base surface, 24c Straight section, 25, 25A Light guide, 26 Plate member, 31, 31A, 31B, 31C, 31D Recess, 31Ba, 31Bb, 31Bc, 31Bd Inclined surface, 31Da, 31Db, 31Dc, 31Dd, 31De, 31Df Inclined surface, 31a, 31b, 31c Inclined surface, 32a, 32b, 32c Boundary line, 33, 33B, 33C, 33D deepest point, 34 slope, sa, sa1 surrounding area.

Claims

1. An illumination optical system for an endoscope having an insertion portion that is inserted into a subject, An optical element having an incident surface into which light enters as incident light, and an exit surface from which the light exits as illumination light, The emission surface has a diffusion region that diffuses the emitted light, The diffusion region has a plurality of recesses and a plurality of peripheral regions arranged on the emission surface. Each recess has a plurality of total reflection surfaces that are inclined with respect to the exit surface and cause total internal reflection of the incident light. At least one of the plurality of total reflective surfaces is inclined at a first angle with respect to the emission surface, Each peripheral region is formed to surround the opening of each recess, I: After passing through the incident surface, the reflected light that has been totally reflected by the total reflection surface, and II: The incident light that, after passing through the incident surface, was not totally reflected at the total reflection surface. Having a penetrating surface that allows light to pass through and be emitted, Endoscope illumination optical system.

2. Each of the aforementioned recesses has a triangular pyramidal shape with its apex being the deepest part and its base being an equilateral triangle with an opening. The aforementioned plurality of total reflective surfaces are the three planes excluding the base surface of the triangular pyramidal shape. The illumination optical system for endoscopes according to claim 1.

3. The angle of each total reflecting surface with respect to the aforementioned emission surface is an angle between 85 degrees and greater than 70 degrees. The illumination optical system for endoscopes according to claim 2.

4. Each of the aforementioned peripheral regions is parallel to the emission surface. The illumination optical system for endoscopes according to claim 1.

5. Each of the aforementioned peripheral regions has a second angle with respect to the emission surface that is greater than 0 degrees and smaller than the first angle. The illumination optical system for endoscopes according to claim 1.

6. The plurality of recesses are arranged on the ejection surface such that two adjacent sides of two adjacent recesses are parallel to each other. The illumination optical system for endoscopes according to claim 1.

7. When the exit surface is viewed from a direction perpendicular to the exit surface, the projected areas of each peripheral region and each total reflecting surface onto the exit surface are denoted as the first area and the second area, respectively, and the ratio of the first area to the second area is a value greater than (1 / 3) and less than 3. The illumination optical system for endoscopes according to claim 1.

8. Each of the aforementioned recesses has a square pyramidal shape with its apex being the deepest part and its square or rectangular base being an opening. The aforementioned plurality of total reflective surfaces are the four planes excluding the base surface of the square pyramidal shape. The illumination optical system for endoscopes according to claim 1.

9. The angle of each total reflecting surface with respect to the aforementioned emission surface is an angle between less than 85 degrees and greater than 65 degrees. The illumination optical system for endoscopes according to claim 8.

10. Each of the aforementioned recesses has a hexagonal pyramidal shape with its apex being the deepest part and its base being an opening, The aforementioned plurality of total reflective surfaces are the six planes excluding the base surface of the hexagonal pyramidal shape. The illumination optical system for endoscopes according to claim 1.

11. The angle of each total reflecting surface with respect to the aforementioned emission surface is an angle between less than 87 degrees and greater than 70 degrees. The illumination optical system for endoscopes according to claim 10.

12. Each of the aforementioned recesses has a polygonal pyramidal shape with its apex being the deepest part and its base being an opening. When the ejection surface is viewed from a direction perpendicular to the ejection surface, the vertex is located at the centroid of the regular polygon. The illumination optical system for endoscopes according to claim 1.

13. The aforementioned endoscope is a direct-viewing endoscope, In the optical element, the incident surface and the exit surface are parallel. The illumination optical system for endoscopes according to claim 1.

14. An optical adapter that can be attached to the tip of an insertion part inserted into a subject, An optical element having an incident surface into which light enters as incident light, and an exit surface from which the light exits as illumination light, The emission surface has a diffusion region that diffuses the emitted light, The diffusion region has a plurality of recesses and a plurality of peripheral regions arranged on the emission surface. Each recess has a plurality of total reflection surfaces that are inclined with respect to the exit surface and cause total internal reflection of the incident light. At least one of the plurality of total reflective surfaces is inclined at a first angle with respect to the emission surface, Each peripheral region is formed to surround the opening of each recess, I: After passing through the incident surface, the reflected light that has been totally reflected by the total reflection surface, and II: The incident light that, after passing through the incident surface, was not totally reflected at the total reflection surface. Having a penetrating surface that allows light to pass through and be emitted, Optical adapter.

15. An optical element having an incident surface into which light enters as incident light, and an exit surface from which the light exits as illumination light, The emission surface has a diffusion region that diffuses the emitted light, The diffusion region has a plurality of recesses and a plurality of peripheral regions arranged on the emission surface. Each recess has a plurality of total reflection surfaces that are inclined with respect to the exit surface and cause total internal reflection of the incident light. At least one of the plurality of total reflective surfaces is inclined at a first angle with respect to the emission surface, Each peripheral region is formed to surround the opening of each recess, I: After passing through the incident surface, the reflected light that has been totally reflected by the total reflection surface, and II: The incident light that, after passing through the incident surface, was not totally reflected at the total reflection surface. Having a penetrating surface that allows light to pass through and be emitted, Endoscope illumination optical system, The insertion part that is inserted into the subject, An endoscope having

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