JP7630355B2 - Illumination optical system, optical adapter and endoscope - Google Patents

Description

The present invention relates to an illumination optical system, an optical adapter, and an endoscope, and in particular to an illumination optical system for an endoscope having an insertion portion that is inserted into a subject, an optical adapter, and an endoscope having the illumination optical system.

Endoscopes are widely used in the industrial and medical fields. Endoscopes have an insertion section, and illumination light is emitted from the tip of the insertion section. The illumination light is reflected from the subject and received by an observation window, and an image of the subject inside the specimen is obtained as an endoscopic image.

When the tip of the insertion part approaches too close to the inner wall of the subject, halation occurs in the endoscopic image. For example, when the tip approaches so as to touch the inner wall of a pipe, the illumination light is irradiated to a large extent on the inner wall near the tip, and halation occurs in the endoscopic image due to the reflected light from the inner wall. When halation occurs, the image processing device adjusts the light to correct the halation by reducing the overall brightness of the illumination so that the subject in the halated area can be easily observed. The halated area is corrected by adjusting the light, but at the same time, the area where halation does not occur becomes dark. In particular, when the tip approaches the inner wall at an angle where the longitudinal axis of the insertion part is nearly parallel to the inner wall surface of the subject, halation occurs noticeably in the area close to the inner wall, and stronger halation occurs in the area close to the inner wall compared to the area far from the inner wall in the image.

Figure 38 is a cross-sectional view of the duct P when the tip of the insertion section IP approaches the inner wall PI of the duct P. Figure 39 is a diagram showing an example of an endoscopic image displayed in the case of Figure 38. An observation window OW and an illumination window IW are provided on the tip surface of the tip.

The light emitted from the illumination window IW is reflected from a portion close to the inner wall PI, causing a strong halation area (shown by the dotted line) in the portion NBA close to the inner wall PI in the image G displayed on the display device DISP, as shown in FIG. 39.

Therefore, to prevent halation from occurring in endoscopic images, for example, Japanese Patent Application Laid-Open Publication No. 6-148527 proposes an illumination mechanism in which an annular illumination head member with an inclined portion is provided at the tip of the insertion portion, and the illumination light is reflected at the illumination head member to change the angle of the illumination light.

Japanese Unexamined Patent Publication No. 6-148527

However, providing an anti-halation mechanism, such as a lighting head member, at the tip of the insertion section narrows the angle of view of the endoscope image and increases the size of the tip.

The present invention aims to provide an illumination optical system, an optical adapter, and an endoscope that can prevent halation from occurring in an endoscopic image while preventing the tip of the insertion section from becoming too large and without narrowing the angle of view of the endoscopic image.

The illumination optical system of one aspect of the present invention is an illumination optical system for an endoscope having an insertion portion to be inserted into a subject, and includes an observation window provided on the tip surface of the tip of the insertion portion, an illumination window provided on the tip surface of the tip portion and having a ring-like or partially circular shape when the tip surface is viewed from the tip side, and an optical element provided behind the illumination window and having an entrance portion into which light is incident and an exit portion that emits the light as illumination light, and the entrance portion or the exit portion has a diffusion portion having at least one or more convex portions that diffuse the light, and the at least one or more convex portions are configured to diffuse the light emitted from the exit portion so that, when the tip surface of the tip portion is viewed from the tip side, the second light emitted in the inner radial direction toward the center of the insertion portion or the third light emitted in the tangential direction of the outer periphery of the insertion portion is greater than the first light emitted in the outer radial direction from the center of the insertion portion.

The optical adapter of one aspect of the present invention is an optical adapter that can be attached to the tip of an endoscope having an insertion portion that is inserted into a subject, and has an optical element having an entrance portion into which light is incident from the tip of the insertion portion as incident light and an exit portion that emits the light as illumination light, and has an observation window provided on the tip surface of the optical adapter, and an illumination window provided on the tip side of the optical element, which has a ring shape or a partial circle when the tip is viewed from the tip side, and emits the illumination light from the exit portion, and the entrance portion or the exit portion has a diffusion portion having at least one or more convex portions that diffuse the light emitted from the exit portion, and the at least one or more convex portions are configured to diffuse the light emitted from the exit portion so that, when the tip surface of the tip is viewed from the tip side, the second light emitted in the inner radial direction toward the center of the insertion portion or the third light emitted in the tangential direction of the outer periphery of the insertion portion is greater than the first light emitted in the outer radial direction from the center of the insertion portion.

An endoscope according to one aspect of the present invention has an illumination optical system according to one aspect of the present invention.

The present invention provides an illumination optical system, an optical adapter, and an endoscope that can prevent halation from occurring in an endoscopic image while preventing the tip of the insertion section from becoming large and without narrowing the angle of view of the endoscopic image.

1 is a configuration diagram showing a configuration of an endoscope apparatus according to a first embodiment of the present invention; 1 is a schematic diagram for explaining an imaging unit and an illumination optical system in an endoscope apparatus according to a first embodiment of the present invention. FIG. 1 is a schematic diagram for explaining an objective optical system and an illumination optical system in an endoscope apparatus using a rigid endoscope according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view of the tip portion along the central axis of the insertion portion according to the first embodiment of the present invention. FIG. 1 is a perspective view of a diffusive optical element according to a first embodiment of the present invention, as viewed obliquely from the front. 1 is a perspective view of a diffusive optical element according to a first embodiment of the present invention, as viewed obliquely from behind; 1 is a side view of a diffusive optical element according to a first embodiment of the present invention as viewed from the tip side. 3 is a cross-sectional view taken along the central axis of the diffusive optical element for explaining the emission direction of light according to the first embodiment of the present invention. FIG. 3 is a diagram showing the diffusive optical element as viewed from the tip side, for explaining the light emission direction according to the first embodiment of the present invention; FIG. 3A to 3C are diagrams for explaining optical characteristics of the diffusive optical element according to the first embodiment of the present invention. FIG. 11 is a perspective view of a diffusive optical element according to a second embodiment of the present invention. 11 is a side view of a diffusive optical element according to a second embodiment of the present invention, as viewed from the tip side of the diffusive optical element. FIG. 13 is a partial cross-sectional view of a tip side portion of a diffusive optical element according to a second embodiment of the present invention, as viewed in a direction perpendicular to the central axis. FIG. 13A and 13B are diagrams for explaining the angles of two inclined surfaces at the tip of a diffusive optical element according to a second embodiment of the present invention. 11 is a cross-sectional view of a tip portion of an insertion portion according to a second embodiment of the present invention. FIG. FIG. 11 is a perspective view of a diffusive optical element according to a third embodiment of the present invention. FIG. 11 is a front view of a diffusive optical element according to a third embodiment of the present invention, as viewed in a direction perpendicular to the central axis of the diffusive optical element. FIG. 13 is a diagram showing the minimum unit that defines the shapes of the two slope portions of each convex portion according to the third embodiment of the present invention. 13A to 13C are diagrams for explaining the cross-sectional shape of each protrusion according to the third embodiment of the present invention. 13 is a cross-sectional view of a convex portion along the central axis of a diffusive optical element for explaining the emission direction of light in a diffusing portion according to a third embodiment of the present invention. FIG. 13A and 13B are diagrams showing the distal end surface and a cross section of the distal end portion to explain the structure of the distal end portion of an insertion section according to a third embodiment of the present invention. FIG. 13 is a schematic diagram for explaining an imaging unit and an illumination optical system in an endoscope apparatus according to a fourth embodiment of the present invention. 13A and 13B are views showing a distal end surface and a cross section of the distal end portion to explain the structure of the distal end portion of an insertion section according to a fourth embodiment of the present invention. FIG. 13 is a perspective view of a diffusive optical element according to a fourth embodiment of the present invention, as viewed from an oblique direction at the tip end side thereof. FIG. 13 is a perspective view of the diffusive optical element according to the fourth embodiment of the present invention, as viewed from an oblique direction on another tip side thereof. 13A and 13B are diagrams illustrating a tip surface and a cross section of a diffusive optical element for explaining the structure of the diffusive optical element according to a fourth embodiment of the present invention. 13 is a cross-sectional view of the tip of a diffusive optical element taken along a line extending from the center in the outer radial direction, according to a fourth embodiment of the present invention. FIG. 13A and 13B are diagrams showing the tip face and cross section of a diffusive optical element having a plurality of convex portions formed so that the central portion protrudes, according to a modified example of the fourth embodiment of the present invention. FIG. 13 is a front view of the tip surface when the tip portion is viewed from the tip side according to the fifth embodiment of the present invention. FIG. 13 is a perspective view showing the shape of an inner region of a diffusive optical element according to a fifth embodiment of the present invention. FIG. 13 is a perspective view showing the shape of an outer region of a diffusive optical element according to a fifth embodiment of the present invention. 13A to 13C are views showing the distal end surface and a cross section of the distal end portion to explain the structure of the distal end portion of an insertion section according to a sixth embodiment of the present invention. FIG. 13 is a perspective view of a diffusive optical element according to a sixth embodiment of the present invention, as viewed from an oblique direction at the tip end side thereof. 13 is a perspective view of a diffusive optical element according to a sixth embodiment of the present invention, as viewed obliquely from the base end side. FIG. 13 is a diagram for explaining a function of a Fresnel lens according to the sixth embodiment of the present invention. FIG. 13 is a diagram for explaining a function of a Fresnel lens according to the sixth embodiment of the present invention. FIG. 11 is a side view of a cover glass according to a modified example of each embodiment of the present invention. 4 is a cross-sectional view of a duct showing a case where a tip portion of an insertion portion of an endoscope approaches an inner wall of the duct. FIG. 39 is a diagram showing an example of an endoscopic image displayed in the case of FIG. 38.

The following describes an embodiment of the present invention with reference to the drawings.

In addition, in each drawing used in the following description, the scale of each component is different so that each component can be recognized on the drawing, and the present invention is not limited to only the quantity of components, the shapes of components, the size ratios of the components, and the relative positional relationships of each component depicted in these drawings.
(First embodiment)
(Configuration of the endoscope device)

Figure 1 is a diagram showing the configuration of an endoscope device according to this embodiment.

As shown in FIG. 1, the endoscope device 1 is configured to have a device main body 2 equipped with 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 endoscopic image, an operation menu, etc. are displayed. This display unit 4 may be provided with a touch panel.

The endoscope 3 is composed of an insertion section 5 that serves as an endoscope insertion section that is inserted into the subject, an operation section 6 that is connected to the base end of the insertion section 5, and a universal cord 7 that extends from the operation section 6. The endoscope 3 is detachable from the device body 2 via the universal cord 7.

The insertion section 5 is configured to have, in order from the tip side, a tip section 11, a curved section 12, and a long flexible section 13. The curved section 12 is connected to the base end of the tip section 11 and is configured to bend freely, for example, in the up, down, left, and right directions. The flexible section 13 is connected to the base end of the curved section 12 and is flexible.

The tip 11 of the insertion section 5 has an imaging element 23b (Fig. 2) such as a CMOS image sensor built in. An observation window 21 (Fig. 2) is provided on the tip surface 11a of the tip 11 of the insertion section 5. The imaging element 23b receives incident light that is incident on the observation window 21.

As shown by the arrow, the optical adapter 10 for direct viewing can be detachably attached to the tip 11. For example, by attaching the optical adapter 10 for direct viewing 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 subject of inspection, the purpose of inspection, etc. Note that the endoscope device 1 can also be used without attaching the optical adapter 10 to the tip 11.

The operation unit 6 is provided with a bending joystick 6a for bending the bending portion 12 in the up, down, left, and right directions. The user can bend the bending portion 12 in a desired direction by tilting the bending joystick 6a. In addition to the bending joystick 6a, the operation unit 6 is also provided with various operation buttons for instructing the endoscope functions, such as a freeze button, a bending lock button, and a recording instruction button.

In addition, if the display unit 4 is configured to have a touch panel, the user may operate the touch panel to instruct various operations of the endoscope device 1, which are the same instructions as those given by the various operation buttons that instruct the endoscope functions.

The display unit 4 of the device body 2 displays an endoscopic image captured by the imaging element 23b (Figs. 2 and 3) of the imaging unit provided in the tip portion 11. Inside the device body 2, various circuits are provided, such as a control unit (not shown) that processes images and performs various controls, and a recording device that records processed images in a memory (not shown).

Figure 2 is a schematic diagram for explaining the imaging unit and illumination optical system in the endoscope device. The tip surface 11a of the tip 11 of the insertion section 5 has a circular shape, and an observation window 21 is provided in the center of the tip surface 11a. A ring-shaped illumination window 22 is provided on the tip surface 11a so as to surround the observation window 21. A concave lens 21a for the observation window 21 and a cover glass 22a for the illumination window 22 are provided on the tip surface 11a of the tip 11. That is, the illumination window 22 is provided on the tip surface 11a of the tip 11, and has a ring shape when the tip surface 11a is viewed from the tip side.

Note that here, the ring shape of the illumination window 22 is formed from a single ring shape, but it may be formed from multiple arc shapes (e.g., two arc shapes).

The imaging unit 23 is provided behind the concave lens 21a. The imaging unit 23 has an imaging element 23b (Fig. 4) arranged on the base end side of the lens group 23a that constitutes the objective optical system (Fig. 4). The imaging element 23b is, for example, a CMOS image sensor. The angle of view of the objective optical system is wide, as shown by the dashed line. The concave lens 21a is also part of the objective optical system, and constitutes the objective optical system in combination with the lens group 23a.

Behind the cover glass 22a, the tip end face of the light guide 25, which is an optical fiber bundle, is arranged in a ring shape to match the ring shape of the illumination window 22, sandwiching the diffusion optical element 27. The base end face of the light guide 25 is arranged at a position where it can receive light from the light source 26 provided in the operation unit 6. The base end face of the light guide 25 is formed in a circular shape. Here, the light guide 25 is arranged in the insertion unit 5 so that the optical fiber bundle is unraveled from the base end side to the tip side, and the tip end face of the light guide 25 is ring-shaped. Note that even if the optical fiber bundle is not unraveled until it is completely ring-shaped, but is unraveled to the extent that it forms a semicircle, it is possible to diffuse the light when passing through the cylindrical part of the diffusion optical element 27.

Here, the light source 26 is an LED light source and is provided in the operation unit 6, but it may be provided in the device body 2. In this case, light may be guided from the light source 26 in the device body 2 using an optical fiber or the like.

Light reflected from the subject enters the observation window 21. The light that enters the observation window 21 forms an image on the imaging surface of the imaging element 23b of the imaging unit 23. Multiple signal lines 24 extending from the imaging element 23b are connected to a drive circuit and a signal processing circuit (both not shown) in the device body 2. The imaging element 23b is driven by a drive circuit (not shown) in the device body 2 and outputs an imaging signal. The signal processing circuit in the device body 2 generates an endoscopic image based on the imaging signal and displays it on the display unit 4.

As described above, the diffusion optical element 27 is provided between the illumination window 22 and the tip surface of the light guide 25. The configuration of the diffusion optical element 27 will be described later.

The endoscope described above is a flexible endoscope, but it may also be a rigid endoscope. Figure 3 is a schematic diagram for explaining the objective optical system and the illumination optical system in an endoscope device using a rigid endoscope.

The rigid endoscope 3a has an insertion section 5a and an eyepiece section 5b provided at the base end of the insertion section 5a. The insertion section 5a is made of a rigid cylindrical member. A circular observation window 21 is provided in the center of the tip surface 11a of the insertion section 5a. A ring-shaped illumination window 22 is provided on the tip surface 11a so as to surround the observation window 21.

A lens group 23a is provided in the insertion section 5a behind the concave lens 21a. A relay lens 31 is disposed on the base end side of the lens group 23a. An eyepiece lens 32 is disposed on the base end side of the relay lens 31.

Behind the cover glass 22a, the tip end face of the light guide 33, which is an optical fiber bundle, is arranged in a ring shape to match the ring shape of the illumination window 22, sandwiching the diffusion optical element 27.

A mounting section 34 is provided midway through the insertion section 5a for detachably mounting a light guide cable 33a extending from the light source device 33. The light source device 33 has a light source 35, which is an LED light source, inside. A light guide 36, which is an optical fiber bundle, is disposed within the light guide cable 33a. The base end surface of the light guide 36 is positioned and fixed within the light source device 33 so as to receive light from the light source 35.

The base end of the light guide 33 is fixed to the mounting portion 34. When the tip of the light guide cable 33a is mounted to the mounting portion 34, the tip surface of the light guide 36 is disposed to face the base end surface of the light guide 33. Thus, light from the light source 35 passes through the light guide 36 and enters the base end surface of the light guide 33. The light that enters the base end surface of the light guide 33 exits from the tip of the light guide 33 and exits as illumination light from the illumination window 22.

The base end surface of the light guide 33 is formed in a circular shape. The light guide 33 is arranged in the insertion section 5a such that the optical fiber bundle is unraveled from the base end side toward the tip end side, and the tip end surface of the light guide 33 is ring-shaped. The ring-shaped tip surface of the light guide 33 is arranged to correspond to the base end surface 27a of the diffusion optical element 27.

When the user brings his/her eye close to the eyepiece 5b, the subject image can be seen through the eyepiece lens 32. A diffusion optical element 27 is provided between the illumination window 22 and the tip surface of the light guide 33.

Figure 4 is a cross-sectional view of the tip 11 along the central axis O of the insertion section 5. Figure 4 shows a cross-section of the tip surface 11a having the ring-shaped illumination window 22 shown in Figure 2. The central axis of the cylindrical diffusion optical element 27 coincides with the central axis O of the insertion section 5. The tip 11 has an imaging unit 23 in a cylindrical housing 11x. The imaging unit 23 is fixed to a hard member (not shown). The imaging unit 23 has a lens group 23a and an imaging element 23b. The imaging unit 23 is fixed in the tip 11 so that light from the observation window 21 enters the objective optical system as shown in Figure 4.

4, a diffusing optical element 27 is disposed behind the illumination window 22. The diffusing optical element 27 is disposed such that a base end surface 27a faces the tip surface of the light guide 25 and a tip surface 27b faces the base end surface of the cover glass 22a.
(Configuration of Diffusion Optical Element)

Figures 5 to 7 are diagrams showing the configuration of the diffusing optical element 27. Figure 5 is a perspective view of the diffusing optical element 27 as viewed diagonally from the front. Figure 6 is a perspective view of the diffusing optical element 27 as viewed diagonally from the rear. Figure 7 is a side view of the diffusing optical element 27 as viewed from the tip side.

The diffusing optical element 27 has a cylindrical shape. The diffusing optical element 27 is made of glass or plastic. These are transparent members with a refractive index of about 1.3 to 2.2. The base end surface 27a of the diffusing optical element 27 is an entrance surface on which light is incident, and has a ring shape. The tip surface 27b of the diffusing optical element 27 is an exit surface on which light is incident. The base end surface 27a and the tip surface 27b of the diffusing optical element 27 have planes parallel to a plane perpendicular to the central axis O of the diffusing optical element 27. The central axis O of the diffusing optical element 27 coincides with the optical axis of the objective optical system of the imaging unit 23. The diffusing optical element 27 has a hollow portion 27d along the central axis O of the diffusing optical element 27.

That is, the diffusion optical element 27 is an optical element that is provided behind the illumination window 22 and has a base end surface 27a as an entrance portion where light enters, and a tip end surface 27b as an exit portion where light exits as illumination light.

A plurality of V-grooves 27v are formed along the circumferential direction on the tip side portion of the outer peripheral surface 27c of the diffusion optical element 27. That is, each V-groove 27v is provided on the tip side outer peripheral portion of the cylindrical diffusion optical element 27. Each V-groove 27v is formed at a predetermined angle with respect to the central axis O. The diffusion optical element 27 has a tapered portion 27e having a conical shape on the tip side. Each V-groove 27v is formed in a range including the tapered portion 27e. When the inclination angle of the tapered portion 27e on the plane passing through the central axis O is α, α is an angle in the range of 2 degrees to 20 degrees.

In other words, a plurality of elongated protrusions 27p, shown by dotted lines in Figs. 5 to 7, are provided at predetermined intervals along the circumferential direction on the tip side surface of the cylindrical diffusion optical element 27 including the tapered portion 27e. The cross-sectional shape of each protrusion 27p perpendicular to the longitudinal axis O is triangular. Two inclined surfaces 27s of two adjacent protrusions 27p form one V-shaped groove 27v. The longitudinal axis Os of each inclined surface 27s is inclined by an angle α with respect to the longitudinal axis O in a plane including the longitudinal axes O and Os.

That is, each convex portion 27p has two inclined portions 27s, and is formed on the outer periphery of the diffusion optical element 27 at a predetermined angle α with respect to the central axis O of the cylindrical shape so that the tip side portion of each convex portion 27p approaches the central axis O of the cylindrical shape. As shown in FIG. 7, when the tip surface 11a of the tip portion 11 is viewed from the tip side, the tip surface 27b has a shape in which multiple triangles formed by the two inclined portions 27s are arranged in a ring shape.

The light emitted from the tip of the light guide 25 is incident on the base end surface 27a. The light incident on the base end surface 27a travels through the diffusion optical element 27. The inclination angle α of the slope portion 27s is small enough to totally reflect the light from the base end surface 27a. Therefore, a part of the light incident on the base end surface 27a is totally reflected at the slope portion 27s and emitted from the tip end surface 27b. Another part of the light incident on the base end surface 27a is not totally reflected at the slope portion 27s and is emitted from the tip end surface 27b. In other words, the light emitted from the tip end surface 27b includes at least two components: a component that is totally reflected at the slope portion 27s once or more times and a component that is not totally reflected at the slope portion 27s. In addition, some of the light emitted from the tip end surface 27b is totally reflected at two or more times at two adjacent slope portions 27s.

That is, the light incident on the base end surface 27a, which is the entrance portion, is totally reflected by the two sloped surfaces 27s before passing through the tip end surface 27b, and is also emitted so as to pass through the tip end surface 27b without being totally reflected by the two sloped surfaces 27s.

Figure 8 is a cross-sectional view along the central axis O of the diffusing optical element 27 to explain the direction of light emission. Figure 9 is a view of the diffusing optical element 27 as seen from the tip side to explain the direction of light emission.

When the diffusing optical element 27 is viewed from the tip side, the tip surface 27b has a ring shape with a circular inner side and multiple triangles arranged in a circle on the outside, as shown in FIG. 9. That is, the tip surface 27b has a ring shape with an outer periphery having a shape of multiple connected triangles and an inner periphery having a circle. When the apex of each outer triangle is vt, the length from the central axis O to each apex vt is equal. Such a ring-shaped tip surface 27b is a light transmitting surface, and light from the tip surface 27b is emitted in a direction inclined toward the central axis O as shown in FIG. 8, and spreads in the tangent direction of the ring shape as shown in FIG. 9.

The multiple convex portions 27p are arranged at equal intervals at a predetermined angle along the circumferential direction of the diffusion optical element 27, so that the light emitted from the multiple convex portions 27p is emitted from multiple locations arranged in a ring shape when the diffusion optical element 27 is viewed from the tip side. As a result, the illumination light is irradiated approximately evenly onto the subject. The more convex portions 27p there are, the more evenly the illumination light is irradiated onto the subject.

Specifically, multiple convex portions 27p are arranged at equal intervals along the outer peripheral surface of the diffusion optical element 27, so that the light from the multiple convex portions 27p arranged in a ring shape is combined on the tip surface 27b to form a substantially uniform illumination light. Therefore, in order to form a substantially uniform illumination light, it is preferable that the number N of convex portions 27p is 4 or more.

That is, the diffusive optical element 27 has a tip surface 27b as an emitting portion, and a plurality of convex portions 27p formed on the tapered portion on the tip side. The plurality of convex portions 27p diffuse the light emitted from the tip surface 27b. The plurality of convex portions 27p are configured to diffuse the light emitted from the emitting portion so that, when the tip surface of the tip portion is viewed from the tip side, more light is emitted in the inner diameter direction toward the central axis O of the insertion portion 5 than in the outer diameter direction from the central axis O of the insertion portion 5. Thus, the emitting portion of the diffusive optical element 27 includes a diffusion portion DS having a plurality of convex portions 27p that emit light in a diffused manner.

Also, by providing the V-groove 27v, light traveling in the outer diameter direction is totally reflected by one surface of two adjacent V-grooves 27v and travels toward the tip at approximately the same diameter, or as shown by the two-dot chain line in FIG. 9, it may travel along the optical path in the tip direction at approximately the same diameter after being reflected twice between two adjacent V-grooves 27v and changing direction. Therefore, the reflected light reaches the exit surface of the diffusing optical element 27 before being reflected by the inner peripheral surface. For this reason, the diffusing optical element 27 is configured to be able to fulfill the role of minimizing the proportion of light rays that are reflected again by the inner peripheral surface of the diffusing optical element 27 and spread outward.

Figure 10 is a diagram for explaining the optical characteristics of the diffusive optical element 27. Since Figure 10 shows the diffusive optical element 27 shown in Figures 5 to 7, the number of V-grooves 27v is less than the number of V-grooves 27v shown in Figures 5 to 7.

When the angle between two adjacent inclined surfaces 27s of two adjacent V-grooves of the tip surface 27b in a plane perpendicular to the central axis O is θ, θ is an angle in the range of 75 degrees to 105 degrees. θ is preferably 90 degrees.

Furthermore, when the outer diameter of the cylindrical portion of the diffusive optical element 27 is Φout, the inner diameter of the hollow portion 27d of the diffusive optical element 27 is Φin, the diameter of the circumscribing circle of the triangular portion of the tip surface 27b is Sout, and the diameter of the inscribing circle of the triangular portion of the tip surface 27b is Sin, it is preferable that the following inequalities (1) and (2) hold.

Here, Sout<Φout, Sin>Φin. The refractive index n of the diffusion optical element 27 is 2.2>n>1.33. The value of this refractive index depends on the material (glass, plastic, etc.) of the diffusion optical element 27 mentioned above.

The larger the value of the central equation in inequality (1), the greater the amount of light that is totally reflected in the emitted light, meaning that less halation occurs. However, it is preferable for the value of the central equation to be 0.5 or close to 0.5.

As described above, inequality (1) indicates the ratio of the amount of reflected light at the inclined surface portion 27s to the amount of incident light. It is desirable for this ratio to be a value between 0.2 and 0.8. If the ratio of the amount of reflected light exceeds 0.8, the opening portion through which the light reflected by total reflection can exit from the front becomes smaller, resulting in a loss of light. Furthermore, if it falls below 0.2, the proportion of the total reflected light that exits diagonally inward from the front surface of the diffusing optical element 27 becomes smaller, and the effect of changing the light distribution of the illumination light to prevent halation cannot be obtained.

The following inequality (2) shows the ratio of the sloped surface 27s to the length of the base end surface 27a in the radial direction when the diffusive optical element 27 is viewed from the tip side. The larger this ratio is, the greater the amount of total reflection by each sloped surface 27s.

(Sout-Sin)/(Φout-Φin)>0.1...(2)

If the angle α becomes too large, the area of the tip surface 27b becomes small, and the light emitted from the tip surface 27b in the direction of the central axis O decreases. If the angle α becomes too small, the area of the tip surface 27b becomes large, and the light emitted from the tip surface 27b in the direction of the central axis O increases, but the light emitted from the tip surface 27b in the outer diameter direction of the central axis O increases.

Therefore, when inequality (1) holds, it is possible to suppress the amount of light emitted from tip surface 27b in the outer diameter direction of central axis O while ensuring the amount of light emitted from tip surface 27b in the direction of central axis O.

Note that, although the circumscribing circle of the tip surface 27b is circular here, it does not have to be a perfect circle. For example, it may be an ellipse.

Furthermore, here, the diffusive optical element 27 is a single cylindrical member, but it may be composed of multiple partial cylindrical members divided into two or more parts along a plane parallel to the central axis O.

As described above, according to the first embodiment described above, it is possible to provide an illumination optical system that can suppress the increase in size of the tip of the insertion section without narrowing the angle of view of the endoscopic image. Suppressing the increase in size of the tip contributes to making the diameter of the insertion section 5 thinner.

In particular, for example, even if the tip portion 11 approaches the inner wall of the pipe, when the tip portion 11 is viewed from the tip side, the amount of light directed in the outer diameter direction of the tip portion is reduced, so that the amount of light irradiated to the inner wall is reduced, thereby preventing halation from occurring in the endoscopic image.
Second Embodiment

In the first embodiment, the diffusive optical element 27 has a cylindrical outer peripheral surface with multiple elongated protrusions that are inclined at a predetermined angle with respect to the central axis O so that the tip side approaches the central axis O. In contrast, in the second embodiment, the diffusive optical element has a ring-shaped protrusion on the cylindrical tip surface that has two sloped portions whose central portions protrude toward the tip side.

The configuration of the endoscope device of this embodiment is substantially the same as that of the endoscope device 1 of the first embodiment described above, so the same components are designated by the same symbols and will not be described again. The second embodiment will be described mainly with respect to the configuration that differs from the first embodiment. In addition, the material and characteristics such as the refractive index of the diffusing optical element of this embodiment are the same as those of the diffusing optical element 27 of the first embodiment.

Figure 11 is a perspective view of the diffusive optical element of this embodiment. Figure 12 is a side view of the diffusive optical element of this embodiment as viewed from the tip side of the diffusive optical element.

As shown in Figures 11 and 12, the diffusing optical element 27A of this embodiment has a cylindrical shape. The diffusing optical element 27A is made of glass or plastic. The base end surface 27Aa of the diffusing optical element 27A is an entrance surface where light is incident, and has a ring shape. The tip portion 27Ab of the diffusing optical element 27A is an exit portion where light is incident. The base end surface 27Aa of the diffusing optical element 27A is parallel to a plane perpendicular to the central axis O of the diffusing optical element 27A.

The tip 27Ab of the diffusion optical element 27A has a ring shape when the tip 11 is viewed from the tip side. The tip 27Ab of the diffusion optical element 27A is a ring-shaped convex portion having two sloped surfaces 27Ab1 and 27Ab2. The tip 27Ab has a circular tip edge 27Ab3 formed by the two sloped surfaces 27Ab1 and 27Ab2. The plane including the circular tip edge 27Ab3 is perpendicular to the central axis O of the diffusion optical element 27A.

The diffusion optical element 27A has a cylindrical shape, but the tip 27Ab has a tapered portion formed by the slope portion 27Ab1. The tip 27Ab of the diffusion optical element 27A has a ring-shaped slope formed by the slope portion 27Ab2 on the inside of the tapered portion. In other words, the tip 27Ab has the slope portion 27Ab1 and the slope portion 27Ab2 provided on the inside of the slope portion 27Ab1. The slope portion 27Ab1 and the slope portion 27Ab2 form the diffusion section DS.

Figure 13 is a partial cross-sectional view of the tip 27Ab of the diffusion optical element 27A when viewed from a direction perpendicular to the central axis O. Figure 14 is a diagram for explaining the angles of the two slopes 27Ab1 and 27Ab2 of the tip 27Ab of the diffusion optical element 27A.

As shown in FIG. 13, the inclined surfaces 27Ab1 and 27Ab2 of the tip 27Ab have angles θa and θb, respectively, with respect to a plane RP perpendicular to the central axis O. The angle θb is smaller than the angle θa.

The angles θa and θb are within the ranges of the following expressions (3) and (4).
60° <θa≦85° ...(3)

0° <θb≦30° (4)

That is, when viewed from a direction perpendicular to the central axis O, the angle θa is an angle in the range of more than 60° and not more than 85° with respect to the plane RP perpendicular to the central axis O, and the angle θb is an angle in the range of more than 0° and not more than 30° with respect to the plane RP perpendicular to the central axis O. Thus, the tip portion 27Ab has a ring-shaped portion that protrudes toward the tip direction by the two inclined portions 27Ab1 and 27Ab2.

Equation (3) shows the relationship for total reflection of incident light at inclined surface portion 27Ab1. Equation (4) shows the relationship for transmitting reflected light from inclined surface portion 27Ab1 at inclined surface portion 27Ab2. Thus, inclined surface portion 27Ab1 is a reflective surface that reflects light within diffusion optical element 27A, and inclined surface portion 27Ab2 is a transmissive surface that transmits light within diffusion optical element 27A. In other words, the outside of tip portion 27Ab is a reflective surface, and the inside of tip portion 27Ab is a transmissive surface.

As described above, in a cross section passing through the central axis O of the cylindrical diffusive optical element 27A and parallel to the central axis O, the inclined surface portion 27Ab1 has an angle θa with respect to a plane perpendicular to the central axis O so as to totally reflect light from the base end surface 27Aa. In a cross section passing through the central axis O of the cylindrical diffusive optical element 27A and parallel to the central axis O, the inclined surface portion 27Ab2 has an angle θb with respect to a plane perpendicular to the central axis O so as to transmit light from the base end surface 27Aa and light totally reflected by the inclined surface portion 27Ab1.

Figure 15 is a cross-sectional view of the tip 11 of the insertion section 5 of this embodiment. Figure 15 shows a cross-section of the tip surface 11a having the ring-shaped illumination window 22 shown in Figure 2.

As shown in FIG. 15, the diffusive optical element 27A is positioned so that the base end surface 27Aa faces the tip surface of the light guide 25, and the tip portion 27Ab faces the base end surface of the cover glass 22a.

The light emitted from the light guide 25 is incident on the base end surface 27Aa of the diffusion optical element 27A. The light incident on the base end surface 27Aa passes through the cylindrical diffusion optical element 27A and is emitted from the tip end portion 27Ab.

A portion of the light incident on the base end surface 27Aa is not totally reflected within the diffusive optical element 27A, and exits directly from the inclined surface 27Ab2, which is the transmitting surface. The other portion of the light incident on the base end surface 27Aa is totally reflected within the diffusive optical element 27A, and then exits from the inclined surface 27Ab2, which is the transmitting surface.

In particular, most of the light is reflected by the sloping surface 27Ab1, which is a reflective surface, and is emitted from the sloping surface 27Ab2, which is a transparent surface, toward the central axis O. For example, as shown in FIG. 15, light L1 is emitted from the sloping surface 27Ab2 toward the central axis O.

On the other hand, light parallel or nearly parallel to the central axis O is refracted at the inclined surface 27Ab2, which is a transmitting surface, so as to spread slightly from the tip 27Ab toward the outer diameter of the central axis O before being emitted. For example, as shown in FIG. 15, light L2 is emitted from the inclined surface 27Ab2 without being refracted so as to spread significantly toward the outer diameter side from the central axis O.

The light emitted from the tip 27Ab passes through the cover glass 22a and exits from the illumination window 22 as illumination light.

In particular, as shown in FIG. 15, in the ring-shaped illumination window 22, on the side closer to the radial outside, light is emitted radially inward, and on the side closer to the center, light is emitted radially outward. Therefore, even when the tip 11 approaches the inner wall of the subject with the axis of the insertion section 5 and the inner wall surface nearly parallel, illumination light is emitted radially inward from the part of the illumination window 22 on the radial outside that is closest to the inner wall, not toward the inner wall, so halation is unlikely to occur. Although there is light emitted toward the inner wall (radially outward), this light component is emitted from the side closer to the center of the insertion section 5, and is farther from the inner wall than the light emitted from the radial outside. Therefore, although it is toward the inner wall, halation is unlikely to occur.

As described above, according to the second embodiment, it is possible to provide an illumination optical system that can suppress an increase in size of the tip of the insertion part without narrowing the angle of view of the endoscopic image. Also, as in the first embodiment, even if the tip 11 approaches the inner wall of the pipe, when the tip 11 is viewed from the tip side, the amount of light directed toward the outer diameter direction of the tip 11 is reduced, so that the amount of light irradiated to the inner wall is reduced, and it is possible to prevent halation from occurring in the endoscopic image.
Third Embodiment

In the first embodiment, the cylindrical diffusion optical element 27 has a plurality of elongated protrusions 27p provided at a predetermined interval along the circumferential direction on the outer peripheral surface, and each of the elongated protrusions 27p is inclined toward the central axis O of the cylindrical diffusion optical element 27 by a predetermined angle with respect to the central axis O. In the second embodiment, the diffusion optical element 27A has a ring-shaped tip portion 27Ab having two sloped portions at the tip portion, and the two sloped portions 27Ab1, 27Ab2 are formed in a ring shape. In contrast, in the third embodiment, the diffusion optical element has a plurality of protrusions extending radially from the central axis O on the cylindrical tip portion.

The configuration of the endoscope device of this embodiment is substantially the same as that of the endoscope device 1 of the first embodiment described above, so the same components are designated by the same symbols and will not be described again. The second embodiment will be described mainly with respect to the configuration that differs from the first embodiment. In addition, the material and characteristics such as the refractive index of the diffusing optical element of this embodiment are the same as those of the diffusing optical element 27 of the first embodiment.

Figure 16 is a perspective view of the diffusive optical element of this embodiment. Figure 17 is a front view of the diffusive optical element of this embodiment, as viewed from a direction perpendicular to the central axis of the diffusive optical element.

As shown in Figures 16 and 17, the diffusing optical element 27B of this embodiment has a cylindrical shape. The diffusing optical element 27B is made of glass or plastic. The base end surface 27Ba of the diffusing optical element 27B is an entrance surface into which light is incident, and has a ring shape. A diffusion section DS from which light exits is formed at the tip end portion 27Bb of the diffusing optical element 27B. The base end surface 27Ba of the diffusing optical element 27B is parallel to a plane perpendicular to the central axis O of the diffusing optical element 27B.

The diffusion section DS at the tip 27Bb of the diffusion optical element 27B is formed by connecting multiple convex portions 27Bx in a ring shape. Each convex portion 27Bx has two convex portions P1 and P2. Each convex portion P1 and P2 has an inclined surface portion IP1 and IP2 that extends along the radial direction of the diffusion optical element 27B. In other words, each convex portion 27Bx has an inclined surface portion IP1 and an inclined surface portion IP2, and has an elongated shape that extends radially along the outer diameter direction from the central axis O of the cylindrical diffusion optical element 27B.

As shown in FIG. 16, imaginary lines (shown by two-dot chain lines) extending along the two edges be corresponding to the two protrusions P1, P2 at the tip side of each protrusion 27Bx intersect at point p1 on the central axis O. Imaginary lines (shown by two-dot chain lines) extending along the valley va1 between the two protrusions P1, P2 of each protrusion 27Bx intersect at point p2 on the central axis O. Imaginary lines (shown by two-dot chain lines) extending along the valley va2 between two adjacent protrusions 27Bx intersect at point p3 on the central axis O.

In other words, an imaginary line extended along the edge portion be that includes the vertex of each of the protrusions P1 and P2 intersects with the central axis O. Therefore, an imaginary line extended along multiple edge portions be intersects with a single point p1 on the central axis O.

In addition, an imaginary line extending along the valley portion va1 between the two protrusions P1 and P2 intersects with the central axis O. Therefore, an imaginary line extending along the multiple valley portions va1 intersects with the central axis O at a point p2.

In addition, an imaginary line extending along the valley portion va2 between two adjacent protrusions 27Bx intersects with the central axis O. Therefore, an imaginary line extending along the multiple valley portions va2 intersects with a point p3 on the central axis O.

Next, the shape of the convex portion 27Bx will be described in detail. FIG. 18 is a diagram showing the minimum unit MU that defines the shape of the two sloped portions IP1 and IP2 of each convex portion 27Bx. FIG. 19 is a diagram for explaining the cross-sectional shape of each convex portion 27Bx.

The minimum unit MU has a triangle with two sloped surfaces SSa and SSb. That is, the shapes of the multiple protrusions P1 and P2 are defined based on the shape of this minimum unit MU. As shown in FIG. 18, the minimum unit MU has a bottom surface BS, a sloped surface SSa having an angle (interior angle) θa1 with respect to the bottom surface BS, and a sloped surface SSb having an angle (interior angle) θb1 with respect to the bottom surface BS. The shape of each protrusion 27Bx is defined based on the shapes of these two sloped surfaces SSa and SSb.

As shown in FIG. 19, the shapes of the two protrusions P1 and P2 are determined based on the two slopes SSa and the two slopes SSb when they are symmetrical with respect to a line PP that is perpendicular to the bottom surface BS and passes through a point on the slope SSb. The slopes IP1 and IP2 that form each of the protrusions P1 and P2 have cross-sectional shapes that correspond to parts of the two slopes SSa and SSb in a plane perpendicular to the longitudinal axis of the protrusion 27Bx.

As shown in FIG. 16, the diffusion section DS is an uneven section formed by being disposed on the tip 27Bb of the diffusion optical element 27B. The uneven section has a plurality of convex sections 27Bx, each of which has two convex sections P1 and P2. Each of the convex sections P1 and P2 has an approximately triangular pyramid shape.

The joint JP between the inclined surface portions IP1 and IP2 in each of the protrusions P1 and P2 does not have to be sharp, and may have, for example, a rounded shape or a chamfered shape cut with multiple facets.

As described above, the two inclined surface portions IP1 are formed symmetrically with respect to a plane (passing through line PP) parallel to a line extending radially outward from the central axis O of the cylindrical shape of the diffusion optical element 27B, and the two inclined surface portions IP2 are formed symmetrically with respect to a plane (passing through line PP) parallel to a line extending radially outward from the central axis O of the cylindrical shape of the diffusion optical element 27B.

Figure 20 is a cross-sectional view of the convex portion 27Bx along the central axis O of the diffusion optical element 27B to explain the direction of emission of light in the diffusion portion DS. A part of the light traveling from the base end surface 27Ba toward the diffusion portion DS becomes the light L1, L3 that is totally reflected at the inclined surface IP1 of the convex portions P1, P2 and refracted at the inclined surface IP2 and emitted. Another part of the light traveling toward the diffusion portion DS becomes the light L2, L4 that is incident on the inclined surface IP2 of the convex portions P1, P2 and refracted at the inclined surface IP2 and emitted. As a result, the light L1, L2 and the light L3, L4 are emitted symmetrically with respect to the plane PP0. The plane PP0 is a surface parallel to the central axis O along the valley portion va1. Since each convex portion 27Bx has two convex portions P1, P2, the emitted light is emitted with little unevenness in the light distribution in the vertical direction in Figure 20. By adopting a structure in which the diffusion section DS has a steeply sloping surface IP1 and a gently sloping surface IP2, light can be emitted without generating backflow, and a decrease in the amount of light can be prevented.

As shown in FIG. 20, the distance from edge be to valley va2 along an axis parallel to central axis O is Ha, and the distance from edge be to valley va1 along an axis parallel to central axis O is Hb. Also, as shown in FIG. 20, when the lengths of inclined surface portions IP1 and IP2 in a direction perpendicular to central axis O in a plane parallel to the longitudinal axis direction of elongated convex portion 27Bx are a and b, respectively, it is desirable that they have the following relationship.

60° <θa1≦85° (11)

0° <θb1≦30° (12)

Ha≧Hb...(13)

a≦b (14)

Equation (11) shows the relationship for total reflection of incident light at the slope portion IP1. Equation (12) shows the relationship for transmitting the reflected light from the slope portion IP1 at the slope portion IP2. Equation (13) shows the relationship for transmitting a larger amount of the reflected light from the slope portion IP1. Equation (14) shows the relationship for outputting the reflected light from the slope portion IP1 from the slope portion IP2 with less loss. Equation (4) is also a relational equation for adjusting the light distribution by changing the light intensity ratio between the light L1, L3 that has a large angle when emitted to the plane PP0 and the light L2, L4 that has a small angle when emitted to the plane PP0.

In other words, when viewed from a direction perpendicular to the central axis O, the angle θa1 is an angle in the range of more than 60° and not more than 85° with respect to the base end face 27Ba, which is the incident surface, and the angle θb1 is an angle in the range of more than 0° and not more than 30° with respect to the incident surface 27Ba.

In addition, the distance Ha from the edge be to the valley va2 in the direction of the central axis O is longer than the distance Hb from the edge be to the valley va1.

As described above, each convex portion 27Bx has two inclined surface portions IP1 that have an angle θa1 with respect to the base end face 27Ba and serve as total reflection surfaces that totally reflect incident light, and two inclined surface portions IP2 that have an angle θb1 with respect to the base end face 27Ba and serve as transmission surfaces that transmit the incident light. The angle θb1 is smaller than the angle θa1. The inclined surface portions IP2 serve as transmission surfaces that transmit and emit the reflected light totally reflected by the inclined surface portions IP1 and the incident light that is directly incident on the inclined surface portions IP2.

Figure 21 is a diagram showing the tip surface and cross section of the tip 11 to explain the structure of the tip 11 of the insertion section 5 of this embodiment. Figure 21 shows a cross section of the tip surface 11a having the ring-shaped illumination window 22 shown in Figure 2.

As shown in FIG. 21, the diffusive optical element 27B is positioned so that the base end surface 27Ba faces the tip surface of the light guide 25, and the tip portion 27Bb faces the base end surface of the cover glass 22a.

The light emitted from the light guide 25 is incident on the base end surface 27Ba of the diffusion optical element 27B. The light incident on the base end surface 27Ba passes through the cylindrical diffusion optical element 27B and is emitted from the tip end portion 27Bb.

At this time, the emitted light is diffused at tip 27Bb, which is the diffusion section DS. The light diffusion direction is parallel to the tangent direction of ring-shaped tip 27Bb when tip 11 is viewed from the tip side, as shown by the dashed arrow in Figure 21. The emitted light has a spread, but is refracted so that it does not easily spread outward from tip 27Bb in the outer diameter direction of the central axis O.

The light emitted from the tip 27Bb of the diffusion optical element 27B passes through the cover glass 22a and exits from the illumination window 22 as illumination light.

As described above, according to the third embodiment described above, it is possible to provide an illumination optical system that can suppress the size of the tip of the insertion section without narrowing the angle of view of the endoscopic image. Also, as in the previous embodiment, even if the tip 11 approaches the inner wall of the pipe, when the tip 11 is viewed from the tip side, the amount of light directed toward the outer diameter of the tip 11 is reduced, so that the amount of light irradiated onto the inner wall is reduced, and halation in the endoscopic image can be prevented. In the case of this embodiment, when the inner wall of the subject and the axis of the insertion section 5 approach each other while being nearly parallel, the illumination light emitted from the portion of the illumination window 22 approaching the inner wall is emitted in the tangent direction of the circle, so that the component irradiated toward the inner wall is small, and halation is less likely to occur.

In the embodiment described above, each protrusion 27Bx of the tip 27Bb has two protrusions P1 and P2 as shown in FIG. 19, but may have one protrusion as shown in FIG. 18.

Furthermore, in the above-described embodiment, the diffusion portion DS is provided at the tip portion 27Bb of the diffusion optical element 27B, but it may be provided on the base end surface 27Ba side. That is, the diffusion portion DS may be provided on the base end surface 27Ba side, and the light may be diffused at an incident portion where the light is incident on the diffusion optical element 27B. In this case, a plurality of recesses corresponding to the shapes of the protrusions 27Bx are formed on the base end surface 27Ba.
(Fourth embodiment)

In the first to third embodiments, when the tip 11 of the insertion section 5 of the endoscope 3 is viewed from the tip direction, the illumination window 22 on the tip surface of the tip 11 has a ring shape (or a ring shape made up of multiple arc shapes), but in this embodiment, the illumination window of the tip 11 has a semicircular shape.

The configuration of the endoscope device of this embodiment is substantially the same as that of the endoscope device 1 of the first embodiment described above, so the same components are designated by the same symbols and will not be described again. The second embodiment will be described mainly with respect to the configuration that differs from the first embodiment. In addition, the material and characteristics such as the refractive index of the diffusing optical element of this embodiment are the same as those of the diffusing optical element 27 of the first embodiment.

Figure 22 is a schematic diagram for explaining the imaging unit and the illumination optical system in the endoscope device according to this embodiment. An observation window 21A is provided on the distal end surface 11a of the distal end portion 11 of the insertion section 5. The observation window 21A has a semicircular shape and is provided offset from the center of the distal end surface 11a. A semicircular illumination window 22A is provided on the distal end surface 11a on the opposite side of the observation window 21A with respect to the center of the distal end surface 11a. A cover glass 21Aa for the observation window 21A and a cover glass 22Aa for the illumination window 22A are provided on the distal end surface 11a of the distal end portion 11. That is, the illumination window 22A is provided on the distal end surface 11a of the distal end portion 11 and has a partially circular shape when the distal end surface 11a is viewed from the distal end side.

Here, the illumination window 22A has a semicircular shape when viewed from the tip side, but it may also be a partial circle smaller than the semicircular shape, such as a crescent shape.

The imaging unit 23 is provided behind the cover glass 21Aa. The imaging unit 23 has an imaging element 23b disposed on the base end side of the lens group 23a (Figure 23).

Behind the cover glass 22Aa, the distal end face of the light guide 25, which is an optical fiber bundle, is arranged to match the shape of the illumination window 22A, with a diffusion optical element 27C in between. The proximal end face of the light guide 25 is arranged in a position where it can receive light from a light source 26 provided in the operation unit 6. The proximal end face of the light guide 25 is formed in a circular shape. On the other hand, the distal end face of the light guide 25 has the same shape as the illumination window 22A.

The diffusion optical element 27C is provided between the cover glass 22Aa and the tip surface of the light guide 25. The configuration of the diffusion optical element 27 will be described later.

The endoscope described above is a flexible endoscope, but it may also be a rigid endoscope.

Figure 23 is a diagram showing the tip surface and cross section of the tip 11 to explain the structure of the tip 11 of the insertion section 5 of this embodiment. As shown in Figure 23, the diffusion optical element 27C is arranged so that the base end surface 27Ca faces the tip surface of the light guide 25 and the tip portion 27Cb faces the base end surface of the cover glass 22Aa.

The light emitted from the light guide 25 is incident on the base end surface 27Ca of the diffusion optical element 27C. The light incident on the base end surface 27Ca passes through the partially cylindrical diffusion optical element 27C and is emitted from the tip end portion 27Cb. The tip end portion 27Cb has a diffusion portion DS.

Figures 24 and 25 are diagrams for explaining the shape of the diffusion section DS of the diffusion optical element 27C. Figures 24 and 25 are perspective views of the diffusion optical element 27C as viewed from an oblique direction on the tip side. Figure 26 is a diagram showing the tip surface and cross section of the diffusion optical element 27C to explain the structure of the diffusion optical element 27C of this embodiment.

As shown in Figures 24 and 25, the diffusion optical element 27C has a partially cylindrical shape. As shown in Figure 23, when the tip surface 11a is viewed from the tip side, the illumination window 22A has a partially circular shape (here, a semicircular shape). The tip portion 27Cb of the diffusion optical element 27C has a semicircular shape corresponding to the illumination window 22A.

Specifically, as shown in FIG. 26, when the diffusive optical element 27C is viewed from the tip side, the tip of the diffusive optical element 27C has a straight portion 41 corresponding to a line extending in the outer diameter direction (here, the diameter direction) from the center CO of the semicircle, two side portions 42 cut on both sides of the straight portion 41 in a direction perpendicular to the straight portion, and an arc portion 43 along the outer periphery of the semicircular tip surface 11a.

The tip 27Cb is an emission section that emits light and has a diffusion section DS. The diffusion section DS has multiple convex sections 27Cx arranged along multiple semicircular arcs with different radii of the diffusion optical element 27C.

When the diffusion optical element 27C is viewed from the tip side, the diffusion section DS has an inner region IR on the inside (center CO side) of an arc passing through a point at a predetermined length d1 from the center CO in the outer radial direction, and an outer region OR on the outside of the arc. The inner region IR and outer region OR are provided with a plurality of arc-shaped convex portions 27Cx formed around the center CO.

Figure 27 is a cross-sectional view of the tip 27Cb along a line extending from the center CO in the outer diameter direction. Each convex portion 27Cx formed on the tip 27Cb has two inclined surface portions IP1a and IP2a. The angle of the inclined surface portion IP1a with respect to the plane PP1 perpendicular to the axis AO passing through the center CO of the semi-cylindrical diffusion optical element 27C is the same as θa described above. The axis AO passes through the center CO and is perpendicular to the base end surface 27Ca, which is the entrance surface of the diffusion optical element 27C. The angle of the inclined surface portion IP2a is the same as θb described above. Therefore, the angle θa is an angle in the range of more than 60° and less than 85° with respect to the plane RP perpendicular to the central axis O, and the angle θb is an angle in the range of more than 0° and less than 30° with respect to the plane RP perpendicular to the central axis O.

As shown in Figures 26 and 27, in each convex portion 27Cx in the inner region IR, two inclined surface portions IP1a, IP2a are formed so that the inclined surface portion IP1a is located on the inside of the arc and the inclined surface portion IP2a is located on the outside of the arc. In addition, in each convex portion 27Cx in the outer region OR, two inclined surface portions IP1a, IP2a are formed so that the inclined surface portion IP1a is located on the outside of the arc and the inclined surface portion IP2a is located on the inside of the arc. The inclined surface portion IP1a is a reflective surface that totally reflects light within the diffusive optical element 27C, and the inclined surface portion IP2a is a transmissive surface that transmits light from within the diffusive optical element 27C.

As described above, the inclined surface portion IP1a is formed at an angle θa with respect to a plane perpendicular to the central axis of the insertion portion 5 so as to totally reflect light from the base end portion 27Ca in a cross section passing through the center CO of the semicircle and parallel to the central axis O of the insertion portion 5. The inclined surface portion IP2a is formed at an angle θb with respect to a plane perpendicular to the central axis O of the insertion portion 5 so as to transmit light from the base end portion 27Ca in a cross section passing through the center CO of the semicircle and parallel to the central axis of the insertion portion 5. In the inner region IR, the inclined surface portion IP1a is provided on the inner diameter side of the semicircle than the inclined surface portion IP2a, and in the outer region OR, the inclined surface portion IP1a is provided on the outer diameter side of the semicircle than the inclined surface portion IP2a. Note that in the diffusion portion DS, a plurality of convex portions 27Cx may be formed so that the central portion between the center CO and the outer arc portion 43 protrudes.

Figure 28 shows the tip surface and cross section of a diffusive optical element 27C1, which is a modified version of this embodiment and has multiple convex portions 27Cx formed so that the central portion protrudes.

In the two adjacent convex portions 27Cx in the inner region IR, the convex portion 27Cx on the outer side of the arc is positioned so as to protrude further toward the tip than the convex portion 27Cx on the inner side of the arc. In addition, in the two adjacent convex portions 27Cx in the outer region OR, the convex portion 27Cx on the inner side of the arc is positioned so as to protrude further toward the tip than the convex portion 27Cx on the outer side of the arc.

As described above, in the diffusion section DS of this embodiment, light incident on the base end surface 27Ca is emitted outward in the inner region IR, and is emitted inward in the outer region OR.

Specifically, in the inner region IR on the semicircular center CO side, when the tip surface 11a of the tip portion 11 is viewed from the tip side, light is emitted in the outer radial direction from the center of the insertion portion 5, and in the outer region IR outside the semicircular inner region IR, light is emitted in the inner radial direction toward the center CO of the insertion portion 5, when the tip surface 11a of the tip portion 11 is viewed from the tip side.

Therefore, although the outer region OR is close to the outer circumference of the tip surface 11a of the tip portion 11, the light emitted from the outer region OR is refracted in the inner diameter direction.

Therefore, even if the inner wall of the pipe is located near the outer periphery of the tip 11, halation is unlikely to occur.

As described above, according to the fourth embodiment, it is possible to provide an illumination optical system that can suppress the size of the tip of the insertion part without narrowing the angle of view of the endoscope image. Also, as in the above-mentioned embodiment, even if the tip part 11 approaches the inner wall of the pipe, when the tip part 11 is viewed from the tip side, the amount of light directed toward the outer diameter direction of the tip part 11 is reduced, so that the amount of light irradiated to the inner wall is reduced, and it is possible to prevent halation from occurring in the endoscope image. In the case of this embodiment, when the inner wall of the subject and the axis of the insertion part approach each other in a state close to parallel, the illumination light emitted from the part of the illumination window 22A approaching the inner wall is emitted inward in the radial direction, so that the component irradiated from the part close to the inner wall toward the inner wall is small, and halation is unlikely to occur.
Fifth embodiment

In the fourth embodiment, the illumination window of the tip 11 has a semicircular shape, and the diffusive optical element 27C emits light from the outer region from the tip diagonally inward (inner diameter direction) toward the tip, and emits light from the inner region diagonally outward (outer diameter direction) toward the tip, but the diffusive optical element of this embodiment emits light from the outer region from the tip diagonally inward (inner diameter direction) toward the tip.

The configuration of the endoscope device of this embodiment is substantially the same as that of the endoscope device 1 of the fourth embodiment described above, so the same components are designated by the same symbols and will not be described again. The fifth embodiment will be described mainly with respect to the configuration that differs from the fourth embodiment. In addition, the material and characteristics such as the refractive index of the diffusion optical element of this embodiment are the same as those of the diffusion optical element 27 of the first embodiment.

Figure 29 is a front view of the tip surface 11a of the tip portion 11 of this embodiment when viewed from the tip side. Figure 30 is a perspective view showing the shape of the inner region of the diffusion optical element 27D of this embodiment. Figure 31 is a perspective view showing the shape of the outer region of the diffusion optical element 27D of this embodiment. Note that the cover glass 22a is omitted in Figure 29.

As shown in Figures 29 to 31, the uneven shape of the tip 27Db of the diffusing optical element 27D of this embodiment is different from that of the diffusing optical element 27C of the fourth embodiment. As shown in Figure 29, the illumination window 22 has a partial circular shape (semicircular in this case). As shown in Figures 30 and 31, the diffusing optical element 27C has a partial cylindrical shape.

The diffusion section DS of the tip 27Db has a semicircular inner region IR1 and an outer region OR1. When the tip 27Db of the diffusion optical element 27D is viewed from the tip side, the inner region IR1 has an inner region IR1 on the inside (center CO1 side) of an arc passing through a point at a predetermined length d2 from the center CO1 in the outer radial direction, and an outer region OR1 on the outside of the arc. The inner region IR1 has multiple arc-shaped convex portions 27Dx formed around the center CO1 and having different radii. The outer region OR1 has multiple elongated convex portions 27Dy extending along the radial direction of the semicircle.

Each convex portion 27Dx of the inner region IR1 has two inclined surface portions IP1b and IP2b. The inclined surface portion IP1b is provided on the outside of the inclined surface portion IP2b in the outer diameter direction of the semicircle. The angle of the inclined surface portion IP1b with respect to a plane perpendicular to the axis AO1 passing through the center CO1 of the semicylindrical diffusion optical element 27D is the same as θa in FIG. 18 described above. The axis AO1 passes through the center CO1 and is perpendicular to the base end surface 27Da, which is the entrance surface of the diffusion optical element 27D. The angle of the inclined surface portion IP2b is the same as θb in FIG. 18 described above. Therefore, the angle θa is an angle in the range of more than 60° and less than 85° with respect to the plane perpendicular to the central axis O, and the angle θb is an angle in the range of more than 0° and less than 30° with respect to the plane perpendicular to the central axis O.

Each protrusion 27Dy in the outer region OR1 is formed along the outer diameter direction from the center CO1. Each protrusion 27Dy has two inclined surfaces IP1c, IP2c. Each inclined surface IP1c, IP2c is formed along the inner diameter direction toward the axis AO1. As shown in FIG. 31, the multiple protrusions 27Dy are arranged in an arc shape.

When the diffusion optical element 27D is viewed from the tip side, the angle of the inclined surface portion IP1c in a cross section taken along the tangent direction of the semicircle around the center CO1 is the same as θa in FIG. 18 described above. The angle of the inclined surface portion IP2c in a cross section taken along the tangent direction of the semicircle around the center CO1 is the same as θb in FIG. 18 described above.

The cross-sectional shape of each protrusion 27Dy in a cross section along the tangent direction of the semicircle may have two protrusions P1 and P2 as shown in FIG. 20.

In the case of the above-mentioned diffusive optical element 27D, the light from the light guide 25 is incident on the base end surface 27Da. As shown in FIG. 30, the light incident on the base end surface 27Da is emitted from the inner region IR1 of the tip portion 27Db in a diagonal inward direction (inner diameter direction) toward the tip.

In addition, the light incident on the base end surface 27Da is emitted from the outer region OR1 of the tip portion 27Db so as to spread in the tangent direction of the semicircle, as shown in FIG. 31.

As described above, when the tip surface 11a of the tip portion 11 is viewed from the tip side, in the inner region IR1 on the side of the center CO1 of the semicircle, multiple convex portions 27Dx are provided at the emission portion of the diffusion optical element 27D along multiple arcs with different radii of the semicircle, and emit light in the inner diameter direction from the central axis of the insertion portion 5.

When the tip surface 11a of the tip portion 11 is viewed from the tip side, in the outer region OR1 outside the semicircular inner region IR1, the multiple protrusions 27Dy have an elongated shape that extends from the center CO1 of the semicircle along the outer diameter direction, and emit light in the tangent direction of the semicircle.

The inclined surface portion IP1b of each convex portion 27Dx has an angle θa with respect to a plane perpendicular to the central axis of the insertion portion 5 so as to totally reflect light from the base end portion 27Da in a cross section passing through the center CO1 of the semicircle and parallel to the central axis of the insertion portion 5. The inclined surface portion IP2b has an angle θb with respect to a plane perpendicular to the central axis of the insertion portion 5 so as to transmit light from the base end portion 27Da in a cross section passing through the center CO1 of the semicircle and parallel to the central axis of the insertion portion 5.

Each convex portion 27Dy in the outer region OR1 has a slope portion IP1c and a slope portion IP2c. In a cross section taken along the tangential direction around the center CO1 of the semicircle and parallel to the central axis O, the slope portion IP1c has an angle θa with respect to a plane perpendicular to the central axis O of the insertion portion 5 so as to totally reflect light from the base end portion 27Da. In a cross section taken along the tangential direction around the center CO1 of the semicircle and parallel to the central axis O, the slope portion IP2c has an angle θb with respect to a plane perpendicular to the central axis O of the insertion portion 5 so as to transmit light from the base end portion 27Da.

With this configuration, even if there is an inner wall of the pipe near the outer periphery of the tip 11, the amount of illumination light traveling from the outer region OR1 toward the inner wall is small, making it difficult for halation to occur.

In the above-described embodiment, the light emitted from the inner region IR1 is emitted in the inner diameter direction when the tip surface 11a is viewed from the tip side, as shown by the dashed line in FIG. 29, but it may be emitted in the outer diameter direction.

As described above, according to the fifth embodiment, it is possible to provide an illumination optical system that can suppress an increase in size of the tip of the insertion section without narrowing the angle of view of the endoscopic image.
Sixth embodiment

In the first to fifth embodiments described above, the diffusing optical element has multiple convex portions each having two sloped surfaces, but a Fresnel lens may also be used as the diffusing optical element.

The configuration of the endoscope device of this embodiment is substantially the same as that of the endoscope device 1 of the fourth embodiment described above, so the same components are designated by the same symbols and will not be described again. The second embodiment will be described mainly with respect to the configuration that differs from the fourth embodiment. In addition, the material and characteristics such as the refractive index of the diffusing optical element of this embodiment are the same as those of the diffusing optical element 27 of the first embodiment.

Figure 32 is a diagram showing the tip surface and cross section of the tip 11 to explain the structure of the tip 11 of the insertion section 5 in this embodiment. As shown in Figure 32, in this embodiment, the diffusing optical element 27E serves as a cover glass and has a diffusing section DS.

A light guide element 25A is provided at the tip of the light guide 25 inserted into the tip 11 of the insertion section 5. The light guide element 25A has a semi-cylindrical shape. Light emitted from the tip surface of the light guide 25 is incident on the base end surface of the light guide element 25A. The incident light is emitted from the tip surface of the light guide element 25A and is incident on the base end 27Ea of the diffusion optical element 27E. A plurality of arc-shaped convex portions 27Ex (Figure 34) are formed on the base end 27Ea. The multiple convex portions 27Ex are provided at the entrance portion of the diffusion optical element 27E along multiple arcs with different semicircular radii.

The diffusing optical element 27E is diffused at the base end 27Ea and exits from the tip surface 27Eb. As shown in FIG. 32, the illumination window 22 has a partial circle (semicircle in this case) when the tip surface 11a is viewed from the tip side. As shown in FIG. 33 and FIG. 34, the diffusing optical element 27E has a partial cylindrical shape (semi-cylindrical shape).

Figures 33 and 34 are diagrams for explaining the shape of the diffusion optical element 27E. Figure 33 is an oblique view of the tip end side of the diffusion optical element 27E, as viewed obliquely. Figure 34 is an oblique view of the base end side of the diffusion optical element 27E, as viewed obliquely in a direction different from that of Figure 33. The diffusion optical element 27E has a partially cylindrical shape.

More specifically, the tip surface 27Eb of the diffusion optical element 27E is a surface parallel to a plane that passes through the center CO2 of the semicircle and is perpendicular to the central axis O of the tip portion 11. The base end portion 27Ea of the diffusion optical element 27E has a diffusion section DS. Light that is incident on the tip surface 27Eb from the light-guiding element 25A is incident on the diffusion section DS. The diffusion optical element 27E has a Fresnel lens with multiple convex portions 27Ex on the base end portion 27Ea.

The diffusion section DS has a semicircular inner region IR2 and an outer region OR2. When the diffusion optical element 27E is viewed from the base end side, the diffusion section DS has an inner region IR2 on the inside (center CO2 side) of an arc passing through a point at a predetermined length d3 from the center CO2 in the outer radial direction, and an outer region OR2 on the outside of the arc. The inner region IR2 is provided with a plurality of arc-shaped convex portions 27Dz1 formed around the center CO2. The outer region OR2 is provided with a plurality of arc-shaped convex portions 27Dz2 formed around the center CO2. That is, the plurality of convex portions 27Ex includes a plurality of convex portions 27Dz1 and a plurality of convex portions 27Dz2.

The multiple convex portions 27Dz1 and 27Dz2 in the inner region IR2 are part of the Fresnel lens.

Figures 35 and 36 are diagrams for explaining the function of a Fresnel lens. Figure 35 is a diagram for explaining the refraction of light in a Fresnel lens FL1 that functions as a concave lens. One surface of the circular Fresnel lens FL1 is a concave-convex surface CC1 with a sawtooth cross section, and the other surface is a plane PL1. As shown in Figure 35, when light parallel to the optical axis O1 is incident on the concave-convex surface CC1, the light exits from the plane PL1 so as to spread out from the optical axis O1.

Figure 36 is a diagram to explain the refraction of light in a Fresnel lens FL2 that functions as a circular convex lens. One surface of the Fresnel lens FL2 is a concave-convex surface CC2 with a sawtooth cross section, and the other surface is a plane PL2. As shown in Figure 36, when light parallel to the optical axis O1 is incident on the concave-convex surface CC2, the light exits from the plane PL2 so as to converge at a point on the optical axis O1.

As shown in FIG. 34, the inner region IR2 of the diffusive optical element 27E has the uneven surface CC1 of the Fresnel lens FL1 described above formed therein, and the outer region OR2 has the uneven surface CC2 of the Fresnel lens FL2 described above formed therein. Specifically, the inner region IR2 has a Fresnel lens whose optical axis O1 coincides with the central axis AO2 of the tip portion 11 passing through the center CO2 and whose cross-sectional shape is the same as the central portion of the uneven surface CC1 of the Fresnel lens FL1. The outer region OR2 has a Fresnel lens whose optical axis O1 coincides with the central axis AO2 and whose cross-sectional shape is the same as the outer portion of the uneven surface CC2 of the Fresnel lens FL2 formed therein.

In the case of the above-mentioned diffusion optical element 27E, the light from the light guide 25 passes through the light guide element 25A and enters the base end 27Ea of the diffusion optical element 27E. As shown in FIG. 34, the light that enters the base end 27Ea exits from the inner region IR2 in a diagonal outward direction (outer diameter direction) toward the tip, and exits from the outer region OR2 in a diagonal inward direction (inner diameter direction) toward the tip.

That is, in the inner region IR2 on the semicircular center CO2 side, when the tip surface 11a of the tip portion 11 is viewed from the tip side, light is emitted in the outer radial direction from the central axis of the insertion portion 5, and in the outer region OR2 outside the semicircular inner region IR2, light is emitted in the inner radial direction toward the central axis O of the insertion portion 5, when the tip surface 11a of the tip portion 11 is viewed from the tip side.

Therefore, even if there is an inner wall of the pipe near the outer periphery of the tip 11, the amount of illumination light traveling from the outer region OR2 toward the inner wall is small, making it difficult for halation to occur.

As described above, according to the sixth embodiment described above, it is possible to provide an illumination optical system that can prevent the tip of the insertion section from becoming large without narrowing the angle of view of the endoscopic image.

In the above-described embodiment, the cover glass is used as a diffusion optical element, but a diffusion optical element using the Fresnel lens described above may be provided behind the cover glass in addition to the cover glass.

As described above, according to each of the above-mentioned embodiments, it is possible to provide an illumination optical system, an optical adapter, and an endoscope that can prevent halation from occurring in an endoscopic image while preventing the tip of the insertion section from becoming large without narrowing the angle of view of the endoscopic image.

Next, a modified example will be described.
(Variation 1)

In each of the above-described embodiments, the diffusion optical element is provided in the tip 11 of the insertion section 5 of the endoscope 3, but it may also be provided in the optical adapter 10.

In this case, an observation window 21 and an illumination window 22 are provided on the tip surface of the optical adapter 10, and a diffusion optical element is disposed behind the illumination window 22.

For example, the optical adapter 10 includes the above-mentioned diffusing optical element and some of the lenses that make up the objective optical system. Inside the insertion section 5, other lenses that make up the objective optical system, an image sensor 23b, and a light guide 25 are arranged.

When the optical adapter 10 in Figure 1 is attached to the tip 11, the light from the tip surface of the light guide 25 passes through the diffusion optical element and is irradiated in the outer diameter direction with a small amount of light, as described above.

Therefore, the diffusive optical element may be provided within the optical adapter 10 .
(Variation 2)

In the above-described embodiments, when a cover glass is provided on the lighting window, the cover glass may be made of multiple sheets, and one surface of one of the cover glasses may be provided with a grained surface that is processed to resemble frosted glass. The grained surface diffuses light isotropically (randomly), eliminating uneven light distribution.

Figure 37 is a side view of the cover glass according to the second modified example. The cover glass 51 includes multiple pieces of glass 51a, 51b (two in this example). Each piece of glass 51a, 51b has a shape corresponding to the shape of the illumination window 22. For example, if the illumination window 22 is ring-shaped, each piece of glass 51a, 51b has a ring-shaped plate shape. Also, if the illumination window 22 is semicircular, each piece of glass 51a, 51b has a semicircular plate shape. Glass 51b is disposed on the side from which light is emitted. It is even more preferable if the side surface is mirror-finished all around, as this reduces light loss at the side surface.

As shown in FIG. 37, the base end surface 51c of the glass 51b is a grained surface. The two pieces of glass 51a and 51b are fixed together with the grained surfaces sandwiched between them using optical adhesive 51d.

Light incident on the base end surface of glass 51a is diffused by the base end surface 51c of glass 51b. At this time, there is a slight difference in the refractive index between glass 51b and optical adhesive 51d, and the light is slightly isotropically scattered by the base end surface 51c in a limited angular range sufficient to eliminate uneven illumination. An example of the refractive index in this case is 1.8 for glass and 1.5 for optical adhesive.

By using a cover glass having such a grained surface, the illumination light is diffused more uniformly.
(Variation 3)

Note that while the above-mentioned embodiments are examples of endoscopes for direct vision, the diffusing optical element of each of the above-mentioned embodiments can also be applied to endoscopes for side vision, oblique vision, etc.

As described above, according to each of the above-mentioned embodiments, it is possible to provide an illumination optical system, an optical adapter, and an endoscope that can prevent halation from occurring in an endoscopic image while preventing the tip of the insertion section from becoming large without narrowing the angle of view of the endoscopic image.

The present invention is not limited to the above-described embodiment, and various changes and modifications are possible without departing from the spirit of the present invention.

1 Endoscope device, 2 Device body, 3 Endoscope, 3a Rigid endoscope, 4 Display unit, 5 Insertion unit, 5a Insertion unit, 5b Eyepiece unit, 6 Operation unit, 6a Curved joystick, 7 Universal cord, 10 Optical adapter, 11 Tip portion, 11a Tip surface, 11x Housing, 12 Curved portion, 13 Flexible portion, 21, 21A Observation window, 21Aa, 21a Concave lens, 22, 22A Illumination window, 22Aa, 22a Cover glass, 23 Imaging unit, 23a Lens group, 23b Imaging element, 24 Signal line, 25 Light guide, 25A Light guide element, 26 Light source, 27, 27A Diffusion optical element, 27Aa Base end surface, 27Ab Tip portion, 27Ab1, 27Ab2 Slope portion, 27Ab3 Distal edge portion, 27B diffusive optical element, 27Ba base end surface, 27Bb tip portion, 27Bx convex portion, 27C, 27C1 diffusive optical element, 27Ca base end surface, 27Cb tip portion, 27Cx convex portion, 27D diffusive optical element, 27Da base end surface, 27Db tip portion, 27Dx, 27Dy, 27Dz1, 27Dz2 convex portion, 27E diffusive optical element, 27Ea base end portion, 27Eb tip surface, 27Ex convex portion, 27a base end surface, 27b tip surface, 27c outer circumferential surface, 27d hollow portion, 27e tapered portion, 27p convex portion, 27s inclined surface portion, 27v V-groove, 31 relay lens, 32 eyepiece lens, 33 light guide, 33 Light source device, 33a light guide cable, 34 attachment portion, 35 light source, 36 light guide, 41 straight portion, 42 both sides, 43 arc portion, 51 cover glass, 51a, 51b glass, 51c base end surface, 51d adhesive layer.

Claims (15)

An illumination optical system for an endoscope having an insertion portion to be inserted into a subject,
an observation window provided on a distal end surface of the distal end of the insertion portion;
an illumination window provided on the tip surface of the tip portion and having a ring shape or a partial circle shape when the tip surface is viewed from the tip side;
an optical element provided behind the illumination window and having an entrance portion into which light is incident and an exit portion from which the light is emitted as illumination light;
having
the entrance portion or the exit portion has a diffusion portion having at least one convex portion that diffuses the light,
an illumination optical system configured to diffuse the light emitted from the emission portion such that, when the tip surface of the tip portion is viewed from the tip side, a second light emitted in an inner radial direction toward the center of the insertion portion or a third light emitted in a tangential direction of the outer periphery of the insertion portion is greater than a first light emitted in an outer radial direction from the center of the insertion portion. the optical element has a cylindrical shape;
The illumination window is ring-shaped,
The at least one or more protrusions are plural,
Each of the protrusions has two inclined surfaces, and is formed on the outer periphery of the optical element at a predetermined angle with respect to the central axis of the cylindrical shape so that a tip side portion of each of the protrusions approaches the central axis of the cylindrical shape.
The illumination optical system according to claim 1 . The emission portion has a flat surface,
The light incident on the incident portion is emitted from the emission portion including at least two components, that is, a component that is totally reflected by the two inclined surface portions and then transmits through the flat surface, and a component that is not totally reflected by the two inclined surface portions and transmits through the flat surface as it is.
The illumination optical system according to claim 2 . When the tip surface of the tip portion is viewed from the tip side, the plane has a shape in which a plurality of triangles formed by the two inclined portions are arranged in the ring shape.
The illumination optical system according to claim 3 . the optical element has a cylindrical shape;
The illumination window is ring-shaped,
the at least one protruding portion is in the shape of a ring when the tip portion is viewed from the tip side,
the ring-shaped protrusion has a first inclined surface portion and a second inclined surface portion provided inside the first inclined surface portion,
the first inclined surface portion has a first angle with respect to a plane perpendicular to the central axis so as to totally reflect the light from the base end portion of the insertion portion in a cross section passing through the central axis of the cylindrical shape and parallel to the central axis;
the second inclined surface portion has a second angle with respect to a plane perpendicular to the central axis so as to transmit the light from the base end portion in a cross section passing through the central axis of the cylindrical shape and parallel to the central axis;
The illumination optical system according to claim 1 . the optical element has a cylindrical shape;
The illumination window is ring-shaped,
The at least one or more protrusions are plural,
Each of the protruding portions has a first inclined surface portion and a second inclined surface portion, and has an elongated shape extending along an outer diameter direction from a central axis of the cylindrical shape,
the first inclined surface portion has a first angle with respect to a plane perpendicular to the central axis in a cross section along a tangential direction about a central axis of the cylindrical shape so as to totally reflect the light from the base end portion of the insertion portion ;
the second inclined surface portion has a second angle with respect to the plane in a cross section along a tangential direction about a central axis of the cylindrical shape;
The illumination optical system according to claim 1 . Each of the protrusions further includes a third inclined surface portion and a fourth inclined surface portion,
7. The illumination optical system according to claim 6, wherein the third inclined surface portion and the fourth inclined surface portion are formed in plane symmetry with the first inclined surface portion and the second inclined surface portion, respectively, with respect to the plane. the optical element has a partial cylindrical shape;
The illumination window has the partial circular shape,
the at least one or more convex portions are provided on the emission portion of the optical element along a plurality of arcs having different radii of the partial circle,
Each of the protrusions has a first inclined surface portion and a second inclined surface portion,
In a first region on the center side of the partial circle, when the tip surface of the tip portion is viewed from the tip side, a first light is emitted in an outer radial direction from a central axis of the insertion portion, and in a second region outside the first region of the partial circle, when the tip surface of the tip portion is viewed from the tip side, a second light is emitted in an inner radial direction toward the center of the insertion portion.
The illumination optical system according to claim 1 . the first inclined surface portion has a first angle with respect to a plane orthogonal to the central axis in a cross section passing through a center of the partial circle and parallel to the central axis of the insertion portion so as to totally reflect the light from the base end portion, and the second inclined surface portion has a second angle with respect to a plane orthogonal to the central axis in a cross section passing through a center of the partial circle and parallel to the central axis of the insertion portion so as to transmit the light from the base end portion,
In the first region, the first inclined surface portion is provided on an inner diameter side of the partial circle relative to the second inclined surface portion,
In the second region, the first inclined surface portion is provided on an outer diameter side of the partially circular shape relative to the second inclined surface portion.
7. The illumination optical system according to claim 6. the optical element has a partial cylindrical shape;
The illumination window has the partial circular shape,
When the tip surface of the tip portion is viewed from the tip side, in a first region on the center side of the partial circle, the at least one or more convex portions are provided in a plurality of arcs having different radii of the partial circle on the emission portion of the optical element, and a first light is emitted in an inner diameter direction or an outer diameter direction from a central axis of the insertion portion,
When the tip surface of the tip portion is viewed from the tip side, in a second region outside the first region of the partial circle, the at least one convex portion has an elongated shape extending along an outer radial direction from a center of the partial circle, and emits a third light in a tangential direction of the partial circle.
The illumination optical system according to claim 1 . Each of the convex portions in the first region has a first inclined surface portion and a second inclined surface portion,
the first inclined surface portion has a first angle with respect to a plane orthogonal to the central axis in a cross section passing through the center of the partial circle and parallel to the central axis of the insertion portion so as to totally reflect the light from the base end of the insertion portion , and the second inclined surface portion has a second angle with respect to a plane orthogonal to the central axis in a cross section passing through the central axis of the partial circle and parallel to the central axis of the insertion portion so as to transmit the light from the base end,
Each of the convex portions in the second region has a third inclined surface portion and a fourth inclined surface portion,
the third inclined surface portion has a third angle with respect to a plane perpendicular to a central axis of the insertion portion in a cross section along a tangential direction about a center of the partial circle so as to totally reflect the light from the base end portion, and the fourth inclined surface portion has a fourth angle with respect to a plane perpendicular to the central axis of the insertion portion in a cross section along a tangential direction about a center of the partial circle so as to transmit the light from the base end portion.
The illumination optical system according to claim 10. 5. The illumination optical system according to claim 4, wherein the optical element has an outer diameter of Φout, an inner diameter of a hollow portion of the optical element is Φin, a diameter of a circumscribing circle of the triangular portion of the plane is Sout, and a diameter of an inscribing circle of the triangular portion of the plane is Sin, which satisfies the following formula (1) or (2):

(Sout-Sin)/(Φout-Φin)>0.1...(2) the optical element includes a Fresnel lens having a plurality of convex portions,
The illumination window has the partial circular shape,
the plurality of convex portions are provided on the entrance portion of the optical element along a plurality of arcs having different radii of the partial circles,
In a first region on the center side of the partial circle, when the tip surface of the tip portion is viewed from the tip side, a first light is emitted in an outer radial direction from a central axis of the insertion portion, and in a second region outside the first region of the partial circle, when the tip surface of the tip portion is viewed from the tip side, a second light is emitted in an inner radial direction toward the central axis of the insertion portion.
The illumination optical system according to claim 1 . An optical adapter that can be attached to a tip portion of an endoscope having an insertion portion to be inserted into a subject,
an optical element having an entrance portion into which light is incident as incident light from a tip portion of the insertion portion and an exit portion from which the light is emitted as illumination light;
an observation window provided on a tip surface of the optical adapter;
an illumination window that is provided on the tip end side of the optical element, has a ring shape or a partial circle shape when the tip end is viewed from the tip end side, and emits the illumination light from the emission portion;
having
the entrance portion or the exit portion has a diffusion portion having at least one or more convex portions that diffuse the light emitted from the exit portion,
The at least one or more convex portions are configured to diffuse the light emitted from the emission portion so that, when the tip surface of the tip portion is viewed from the tip side, a second light emitted in an inner radial direction toward the center of the insertion portion or a third light emitted in a tangential direction of an outer periphery of the insertion portion is greater than a first light emitted in an outer radial direction from a central axis of the insertion portion.
Optical adapter. An endoscope comprising the illumination optical system according to claim 1 .

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