JP2022182974A - Endoscope illumination optical system, optical adapter and endoscope - Google Patents

Abstract

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

Description

The present invention relates to an endoscope illumination optical system, an optical adapter, and an endoscope, and more particularly to an endoscope illumination optical system, an optical adapter, and an illumination optical system for an endoscope having an insertion section to be inserted into a subject. endoscope.

Endoscopes are widely used in industrial and medical fields. The endoscope has an insertion section, and illumination light is emitted from the distal end of the insertion section. Reflected light of the illumination light from the object is received by the observation window, and the image of the object inside the object is obtained as an endoscope image by acquiring the image of the object.

An illumination optical system having an optical element for diffusing light is provided in the optical adapter attached to the distal end of the insertion section or in the distal end of the insertion section so that the illumination light has a desired light distribution angle.

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

JP 2015-226712 A

However, the light incident on the optical element also spreads to some extent and enters the incident surface of the optical element. Therefore, if an attempt is made to widen the light distribution angle by increasing the angle of the inclined surface with respect to the plane orthogonal to the optical axis of the optical element, the amount of light totally reflected within the optical element increases. When total reflection occurs within the optical element, the amount of illumination light emitted from the emission surface is reduced. Conversely, the angle of the inclined surface must be made small in order to prevent the emitted light amount of the illumination light from decreasing, but if the angle of the inclined surface is made small, the light distribution angle cannot be increased.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an illumination optical system for an endoscope, an optical adapter, and an endoscope that can widen the light distribution while reducing the amount of decrease in the amount of emitted light.

An illumination optical system for an endoscope according to one aspect of the present invention is an illumination optical system for an endoscope having an insertion portion to be inserted into a subject, the illumination optical system for an endoscope having an incident surface on which light is incident as incident light; and an output surface for outputting the light, the output surface having a diffusion area for diffusing the output light, and the diffusion area having a plurality of diffusion areas arranged on the output surface. a concave portion and a plurality of peripheral regions, each concave portion having a plurality of total reflection surfaces inclined with respect to the emission surface for totally reflecting the incident light, and at least one of the plurality of total reflection surfaces one is inclined at a first angle with respect to the exit surface, each peripheral region is formed to surround the plurality of total reflection surfaces, and I: after passing through the entrance surface, the Reflected light that has been totally reflected by the total reflection surface, and II: It has a transmission surface that transmits and emits the incident light that has not been totally reflected by the total reflection surface after passing through the incident surface.

An optical adapter according to one aspect of the present invention is an optical adapter that can be attached to a distal end portion of an insertion section that is inserted into a subject, and has an incident surface on which light as incident light is incident and the light as illumination light is emitted. and an output surface, the output surface having a diffusion region for diffusing the output light, the diffusion region including a plurality of concave portions and a plurality of peripheral portions arranged on the output surface. each concave portion has a plurality of total reflection surfaces tilted with respect to the exit surface for totally reflecting the incident light, at least one of the plurality of total reflection surfaces inclined at a first angle with respect to the surface, each peripheral region being formed to surround the plurality of total reflection surfaces, and I: being totally reflected at the total reflection surface after passing through the incident surface; and II: a transmission surface that transmits and emits the incident light that has not been totally reflected by the total reflection surface after passing through the incident surface.

An endoscope of one aspect of the present invention includes an optical element having an incident surface on which light is incident as incident light and an exit surface from which the light is emitted as illumination light, and the exit surface emits the exit light. a diffusion region for diffusing, the diffusion region having a plurality of recesses and a plurality of peripheral regions arranged on the exit surface, each recess sloping with respect to the exit surface; having a plurality of total reflection surfaces for totally reflecting incident light, at least one of the plurality of total reflection surfaces being inclined at a first angle with respect to the exit surface, each peripheral region comprising: I: Reflected light totally reflected by the total reflection surface after passing through the incident surface; and II: Light reflected by the total reflection surface after passing through the incident surface. an illumination optical system for an endoscope having a transmission surface for transmitting and emitting the incident light that has not been totally reflected at the endoscope; and an insertion section that is inserted into the subject.

ADVANTAGE OF THE INVENTION According to this invention, the illumination optical system for endoscopes, an optical adapter, and an endoscope which can widen light distribution can be provided, reducing the reduction amount of emitted light quantity.

1 is a configuration diagram showing the configuration of an endoscope apparatus according to an embodiment of the present invention; FIG. FIG. 4 is a perspective view of the distal end to which the optical adapter is attached, according to the embodiment of the present invention; FIG. 4 is a cross-sectional view of the distal end to which the optical adapter is attached, according to the embodiment of the present invention; FIG. 10 is a perspective view of the distal end portion to which the optical adapter is attached, in which the shape of the illumination window is ring-shaped, according to the embodiment of the present invention; FIG. 4 is a cross-sectional view of the distal end portion to which the optical adapter is attached, in which the shape of the illumination window is ring-shaped, according to the embodiment of the present invention; It is a figure of a rod lens seen from the tip side concerning an embodiment of the invention. 1 is a perspective view of a tip portion of a rod lens viewed from an oblique tip side according to an embodiment of the present invention; FIG. It is a figure of a cylindrical rod lens seen from the tip side concerning an embodiment of the invention. It is a figure for demonstrating the shape of the recessed part concerning embodiment of this invention. It is a sectional view showing a section shape of a crevice concerning an embodiment of the invention. FIG. 4 is a diagram for explaining a light transmission region of each concave portion according to the embodiment of the present invention; FIG. 4 is a diagram for explaining a peripheral region from which totally reflected light is emitted, according to the embodiment of the present invention; FIG. 4 is a diagram for explaining a peripheral region having an inclined surface according to the embodiment of the invention; It is a figure for demonstrating the emission direction of light concerning embodiment of this invention. It is a figure for demonstrating the position of the deepest part of a recessed part concerning the modification 1 of embodiment of this invention. It is a figure for demonstrating a recessed part concerning the modification 2 of embodiment of this invention. FIG. 12 is a diagram for explaining the position of the deepest part of the recessed part, which is shifted from the center of gravity of the square, according to Modification 2 of the embodiment of the present invention; It is a figure for demonstrating a recessed part concerning the modification 3 of embodiment of this invention. It is a figure for demonstrating a recessed part concerning the modification 3 of embodiment of this invention. FIG. 10 is a plan view of part of the inclined surface and the peripheral region according to Modification 3 of the embodiment of the present invention; FIG. 11 is a diagram for explaining a configuration on an optical path of illumination light within an optical adapter according to Modification 7 of the embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In each drawing used for the following explanation, the scale of each component is changed in order to make each component recognizable on the drawing. is not limited only to the quantity of components, shapes of components, size ratios of components, and relative positional relationships of components described in .
(Configuration of endoscope device)

FIG. 1 is a configuration diagram showing the configuration of an endoscope apparatus according to this embodiment.

As shown in FIG. 1, an endoscope apparatus 1 includes an apparatus main body 2 having functions such as a video processor, and an endoscope 3 connected to the apparatus main body 2 . The apparatus main body 2 has a display unit 4 such as a liquid crystal panel (LCD) for displaying endoscope images, operation menus, and the like. The display unit 4 may be provided with a touch panel.

The endoscope 3 includes an insertion section 5 as an endoscope insertion section to be inserted into a subject, an operation section 6 connected to the proximal end of the insertion section 5, and a universal cord extending from the operation section 6. 7. The endoscope 3 is detachable from the device body 2 via a universal cord 7 .

The insertion portion 5 includes, in order from the distal end side, a distal end portion 11, a bending portion 12, and an elongated flexible portion 13. As shown in FIG. The bending portion 12 is connected to the proximal end of the distal end portion 11 and is configured to be bendable, for example, in the vertical and horizontal directions. The flexible portion 13 is connected to the proximal end of the bending portion 12 and has flexibility.

An optical adapter 10 for direct viewing can be detachably attached to the distal end portion 11 as indicated by an arrow. For example, by attaching the optical adapter 10 for direct viewing to the distal end portion 11, the endoscope 3 becomes an endoscope for direct viewing. That is, the optical adapter 10 can be attached to the distal end portion 11 of the insertion portion 5 of the endoscope 3 . The optical adapter 10 is attached according to the object to be inspected, the application for inspection, and the like. Therefore, the endoscope apparatus 1 can also be used without attaching the optical adapter 10 to the distal end portion 11 . Note that the optical adapter 10 is not limited to one for direct viewing, and may be for side viewing or oblique viewing.

The operation unit 6 is provided with a bending joystick 6a that bends the bending portion 12 vertically and horizontally. 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 provided with buttons for instructing endoscope functions, for example, various operation buttons such as a freeze button, a bending lock button, and a recording instruction button.

In addition, in the case where the display unit 4 is provided with a touch panel, the user may operate the touch panel to instruct various operations of the endoscope apparatus 1 .

The display unit 4 of the apparatus main body 2 displays an endoscope image captured by the imaging element 23 (FIGS. 3 and 5) of the imaging unit provided in the distal end portion 11. FIG. Further, inside the apparatus main body 2, various circuits such as a control unit (not shown) that performs image processing and various controls, a recording device that records processed images in a memory (not shown), and the like are provided.

FIG. 2 is a perspective view of the distal end portion 11 to which the optical adapter 10 is attached. FIG. 3 is a cross-sectional view of the distal end portion 11 to which the optical adapter 10 is attached. FIG. 3 shows a cross section of the distal end portion 11 along the longitudinal axis O of the insertion portion 5. As shown in FIG. In FIG. 3 , the left side of the dotted line is the optical adapter 10 and the right side of the dotted line is the distal end portion 11 .

The optical adapter 10 has a cylindrical shape. An observation window 21 and an illumination window 22 are provided on the distal end surface 10 a of the optical adapter 10 . The observation window 21 and the illumination window 22 have a partially circular shape when the optical adapter 10 is viewed from the distal end side. In particular, illumination window 22 has an elongated semicircular shape.

The observation window 21 is composed of a cover glass 21a. The cover glass 21a also serves as a concave lens for the observation window. Lenses forming a lens group 21b forming an observation optical system are provided in the housing 10b of the optical adapter 10 behind the cover glass 21a.

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

The illumination window 22 emits illumination light. Reflected light from the subject enters the observation window 21 . Light from the subject forms a subject image on the imaging surface of the imaging device 23 via the observation optical system.

The illumination window 22 is composed of a cover glass 22a. The cover glass 22a has two glasses 22a1 and 22a2. The two glasses 22a1 and 22a2 are bonded together with an adhesive.

For example, the base end surface of the glass 22a1 is a grained surface (indicated by dotted lines). The tip surface of the glass 22a1 is flat. Both the base end surface and the tip end surface of the glass 22a2 are flat. The two glasses 22a1 and 22a2 are fixed by bonding with an adhesive so as to sandwich the grained surface. Light is randomly diffused by the grained surface, and uneven light distribution caused by the regularity of light distribution of a diffusion element having a diffusion structure, which will be described later, is eliminated. For example, the refractive indices of the glasses 22a1 and 22a2 are both 1.52, and the refractive index of the adhesive is 1.56. By using members having slightly different refractive indices for the glasses 22a1 and 22a2 and the adhesive, uneven light distribution is eliminated while preventing excessive scattering. If priority is given to securing the amount of light over elimination of light distribution unevenness, the base end surface of the glass 22a1 does not need to be grained.

The light incident on the base end face of the glass 22a2 is emitted from the tip end face of the glass 22a1.

Note that the cover glass 22a may be arranged so that the glass 22a1 and the glass 22a2 are arranged in this order from the base end side. In this case, the glasses 22a1 and 22a2 are arranged so that an air layer is formed between the glass 22a2 on the distal side and the glass 22a1 on the proximal side.

A partially cylindrical rod lens 24 is arranged in the housing 10b of the optical adapter 10 behind the cover glass 22a. The rod lens 24 is made of transparent glass or plastic. A light guide 25 that is an optical fiber bundle is arranged in the insertion portion 5 . A tip surface of the light guide 25 is arranged at the tip portion 11 . When the optical adapter 10 is attached to the distal end portion 11 , the distal end surface of the light guide 25 faces the proximal end surface 24 b of the rod lens 24 .

Light from the light source in the apparatus main body 2 is incident on the base end surface of the light guide 25 . Light emitted from the distal end surface of the light guide 25 enters the proximal end surface 24 b of the rod lens 24 . The light incident on the base end surface 24b of the rod lens 24 passes through the rod lens 24 and is emitted from the tip surface 24a of the rod lens 24. The tip surface 24a of the rod lens 24 has a diffusion structure for diffusing the emitted light. have.

That is, the rod lens 24 is an optical element having a base end surface 24b as an incident surface for incident light and a distal end surface 24a as an exit surface for emitting light as illumination light.

The endoscope 3 is a direct-view endoscope here, and the base end surface 24b, which is the light incident surface of the rod lens 24, and the distal end surface 24a, which is the light exit surface, are parallel.

Diffused light from the tip surface 24 a of the rod lens 24 is incident on the cover glass 22 a and emitted from the illumination window 22 .

Although the endoscope 3 shown in FIGS. 2 and 3 has an elongated semicircular illumination window 22, the illumination window 22 may have a ring shape.

FIG. 4 is a perspective view of the distal end portion 11A to which the optical adapter 10A is attached, with the illumination window 22 having a ring shape. FIG. 5 is a cross-sectional view of the distal end portion 11A to which the optical adapter 10A is attached, the illumination window 22 of which is ring-shaped. FIG. 5 shows a cross section of the distal end portion 11 along the longitudinal axis O of the insertion portion 5. As shown in FIG. In FIG. 5, the left side of the dotted line is the optical adapter 10A, and the right side of the dotted line is the distal end portion 11A.

The optical adapter 10A of FIGS. 4 and 5 has a cylindrical shape. An observation window 21A and an illumination window 22A are provided on the distal end surface 10a of the optical adapter 10A. The observation window 21A has a circular shape when the optical adapter 10A is viewed from the distal end side. The illumination window 22A has a ring shape when the optical adapter 10A is viewed from the distal end side.

The observation window 21A is composed of a cover glass 21Aa. Lenses forming a lens group 21b are provided in the housing 10b of the optical adapter 10 behind the cover glass 21Aa.

A distal end portion 11A of the insertion portion 5 has a distal end hard member (not shown), and a lens 21c and an imaging element 23 that constitute an observation optical system are built in the distal end hard member. That is, when the optical adapter 10 is attached to the insertion portion 5, the observation optical system is composed of the cover glass 21a, the lens group 21b, and the lens 21c.

22 A of illumination windows are comprised by ring-shaped cover glass 22Aa. The cover glass 22Aa has two ring-shaped glasses 22Aa1 and 22Aa2.

For example, the base end surface of the glass 22Aa1 is a grained surface (indicated by dotted lines). The tip surface of the glass 22Aa1 is flat. Both the base end face and the tip end face of the glass 22Aa2 are flat. The two glasses 22Aa1 and 22Aa2 are fixed by bonding with an adhesive so as to sandwich the grained surfaces. For example, the refractive indices of the glasses 22Aa1 and 22Aa2 are both 1.88, and the refractive index of the adhesive is 1.56. By using members with slightly different refractive indices for the glasses 22Aa1 and 22Aa2 and the adhesive, uneven light distribution is eliminated while preventing excessive scattering.

In the cover glass 22Aa, light incident on the base end face of the glass 22Aa2 is emitted from the tip end face of the glass 22Aa1.

Note that the cover glass 22Aa may be arranged so that the glass 22Aa1 and the glass 22Aa2 are arranged in this order from the base end side. In that case, the glass 22Aa1 and the glass 22Aa2 are arranged apart so that an air layer is formed between the glass 22Aa2 on the distal side and the glass 22Aa1 on the proximal side.

A cylindrical rod lens 24A is arranged in the housing 10b of the optical adapter 10A behind the cover glass 22Aa. A light guide 25A, which is an optical fiber bundle, is arranged in the insertion portion 5 . The tip portion of the light guide 25A has a ring-shaped tip surface and is arranged at the tip portion 11A. When the optical adapter 10A is attached to the distal end portion 11A, the distal end surface of the light guide 25A faces the proximal end surface 24Ab of the rod lens 24A.

Light from the light source in the apparatus main body 2 is incident on the base end surface of the light guide 25A. Light emitted from the distal end surface of the light guide 25A enters the proximal end surface 24Ab of the rod lens 24A. The light incident on the base end surface 24Ab of the rod lens 24A passes through the inside of the rod lens 24A and exits from the distal end surface 24Aa of the rod lens 24A. A tip surface 24Aa of the rod lens 24A has a diffusion structure that diffuses emitted light.

That is, the rod lens 24A is an optical element having a base end surface 24Ab as an incident surface for incident light and a distal end surface 24Aa as an exit surface for emitting light as illumination light.

Diffused light from the tip surface 24Aa of the rod lens 24A is incident on the cover glass 22Aa and emitted from the illumination window 22 .

As described above, the rod lens 24 or 24A has a diffusing structure on the tip surface 24a or 24Aa. Next, the diffusion structure will be described.

In the above example, the rod lenses 24, 24A having diffusion structures on the tip surfaces 24a, 24Aa are provided inside the optical adapters 10, 10A. However, the present invention is not limited to this, and the rod lenses 24, 24A may be provided inside the distal end portions 11, 11A of the insertion portion 5 of the endoscope 3 that allows observation of the subject without the optical adapters 10, 10A. That is, rod lenses 24 and 24A having a diffusing structure may be provided behind the illumination windows 22 and 22A of the distal end portions 11 and 11A (in the case of a direct viewing endoscope, the proximal side).

Next, the diffusion structure of the rod lens 24 will be described.

FIG. 6 is a diagram of the rod lens 24 viewed from the tip side. FIG. 7 is a perspective view of the tip portion of the rod lens 24 seen from the oblique tip side.

A plurality of recesses 31 are formed in the tip surface 24a of the rod lens 24. As shown in FIG. Each recess 31 has a polygonal pyramid shape. Here, the opening of each recess 31 has an equilateral triangle shape, and each recess 31 has a regular triangular pyramid shape. A peripheral area sa indicated by a chain double-dashed line is provided around the opening of each recess 31 on the tip surface 24a.

That is, the tip surface 24a, which is the exit surface, has a diffusion area DS that diffuses the emitted light. The diffusion region DS has a plurality of recesses 31 and a plurality of peripheral regions sa arranged on the tip surface 24a.

FIG. 8 is a view of the cylindrical rod lens 24A viewed from the tip side. A plurality of recesses 31 having the same shape as in FIGS. 6 and 7 are also formed on the tip surface 24Aa of the rod lens 24A, and a peripheral region sa indicated by a chain double-dashed line is provided around the opening of each recess 31. .

Next, the shape of the recess 31 will be described.

FIG. 9 is a diagram for explaining the shape of the recess 31. As shown in FIG. The concave portion 31 has a shape into which an equilateral triangular pyramid-shaped object OB is fitted. The object OB has the shape of an equilateral triangular pyramid whose cross-sectional shape parallel to the bottom surface BP is an equilateral triangle. The bottom surface BP of the object OB has the shape of an equilateral triangle. The bottom surface BP has three vertices BPa and three sides BPa1. The object OB has a fourth vertex BPb and three sides BPb1 connecting the three vertices BPa and BPb.

When the object OB is turned upside down and fitted into the concave portion 31, the bottom surface BP of the equilateral triangle becomes flush with the tip surfaces 24a and 24Aa of the rod lenses 24 and 24A (the rod lens 24 will be described below as an example). However, the same applies to the rod lens 24A).

That is, as shown in FIG. 9, each recess 31 has a shape such that when the regular triangular pyramid object OB is turned upside down and fitted into the recess 31, the bottom surface BP is parallel to the tip surface 24a of the rod lens 24. is doing.

Accordingly, the recess 31 has three inclined surfaces 31a, 31b, 31c. Each inclined surface 31a, 31b, 31c has an isosceles triangle (or an equilateral triangle) when viewed from a direction perpendicular to each inclined surface 31a, 31b, 31c. A point 33 where boundary lines 32 a , 32 b , and 32 c of two adjacent inclined surfaces meet is the deepest portion of the recess 31 .

Each concave portion 31 has a polygonal pyramid shape (regular triangular pyramid) with the apex as the deepest portion and the opening of the bottom surface BP of a regular polygon (here, an equilateral triangle). When viewed from the direction, the point 33, which is the vertex, is located at the center of gravity of the regular polygon (here, an equilateral triangle).

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

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

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

FIG. 10 is a cross-sectional view showing the cross-sectional shape of the recess 31. As shown in FIG. The lower side of FIG. 10 shows a cross section of the recess 31 along a plane LL including the boundary line 32a and perpendicular to the tip surface 24a. When the material of the rod lens 24 is glass and the refractive index n is in the range of 1.4 to 2.0, the inclination angle α of the inclined surface 31a with respect to the direction perpendicular to the tip surface 24a on the plane LL is 5 degrees or more. is an angle within the range of less than 20 degrees. The inclination angles of the other inclined surfaces 31b and 31c are also the same as the inclination angle α of the inclined surface 31a, and are angles within the range of 5 degrees or more and less than 20 degrees. In other words, the angle (first angle) of each inclined surface 31a, 31b, . )≦85°.

Part of the light traveling from the proximal end surface 24b to the distal end surface 24a of the rod lens 24 is totally reflected at each of the inclined surfaces 31a, 31b, and 31c. The totally reflected light L1 is emitted from the peripheral area sa of the concave portion 31, which is a transmissive area. That is, each recess 31 has a plurality of (here, three) inclined surfaces 31a, 31b, and 31c, which are total reflection surfaces for totally reflecting incident light. Each inclined surface 31a, 31b, 31c is a total reflection surface inclined at an angle (90-α) with respect to the tip end surface 24a, which is the emitting surface.

The opening of each recess 31 has an equilateral triangle. The aperture has three sides EL. A peripheral region sa is provided to surround the three sides EL of the opening of each recess 31 . Each peripheral region sa is formed so as to surround a plurality of (here, three) inclined surfaces 31a, 31b, and 31c, and includes reflected light totally reflected by each inclined surface 31a, 31b, and 31c, and light inclined from the base end surface 24b. It is a transmission surface that transmits and emits light that has not been totally reflected by the surfaces 31a, 31b, and 31c.

As shown in FIGS. 6 to 8, a plurality of recesses 31 and peripheral regions sa surrounding the recesses 31 as shown in FIG. is formed.

That is, each recess 31 has a triangular pyramidal shape with the vertex BPb as the deepest part and an equilateral triangular bottom BP as an opening. faces 31a, 31b, 31c).

In the case of FIG. 6, the plurality of concave portions 31 are arranged at regular intervals on the distal end surface 24a of the rod lens 24 such that one of the three sides EL is parallel to the straight portion 24c of the partially circular distal end surface 24a. formed. Furthermore, the plurality of recesses 31 are arranged such that the two adjacent sides EL of the two adjacent recesses 31 are parallel to each other and all the intervals between the two adjacent sides EL of the two adjacent recesses 31 are equal. It is arranged on the tip surface 24a.

FIG. 11 is a diagram for explaining the light transmission region of each concave portion 31. As shown in FIG. FIG. 11 is a plan view of the recess 31 when the tip end surface 24a is viewed from a direction perpendicular to the tip end surface 24a.

As described above, three recesses 31 (indicated by chain double-dashed lines) are provided for one recess 31 (indicated by solid lines) such that two adjacent sides EL of two adjacent recesses 31 are parallel. formed around. Regions other than the plurality of recesses 31 on the distal end surface 24a are the plurality of peripheral regions sa.

FIG. 12 is a diagram for explaining the peripheral area sa where the totally reflected light is emitted. Light totally reflected by one inclined surface 31a of one concave portion 31 is emitted from a peripheral region sa (indicated by oblique lines) having a width (d/2). Light that has not been totally reflected by the inclined surface 31a (or 31b or 31c) and has directly reached the peripheral area sa from the base end surface 24b is also emitted from the peripheral area sa (indicated by oblique lines).

The peripheral area sa surrounding each inclined surface 31a, 31b, 31c is a surface parallel to the tip end surface 24a of the rod lens 24, but may have an inclined portion.

FIG. 13 is a diagram for explaining the peripheral area sa1 having an inclined surface. The peripheral region sa1 is an inclined surface provided so as to surround the opening of each recess 31 . Therefore, two inclined surfaces 34 are provided between two parallel sides EL of two adjacent recesses 31 . The inclined surface provided so as to surround the opening of each recess 31 is the peripheral area sa1.

The two inclined surfaces 34 are formed symmetrically with respect to a plane that includes a line CL separated from two adjacent sides EL by a distance (d/2) and perpendicular to the tip surface 24a. The angle β of the inclined surface 34 with respect to the tip surface 24a is 0°<β≦25°. That is, the angle β of the inclined surface 34 is an angle in the range of greater than 0 degrees and less than or equal to 25 degrees with respect to the virtual distal end surface 24 a of the rod lens 24 . In other words, each peripheral region sa1 has an angle β (second angle) that is larger than 0 degrees and smaller than the angle (90−α) with respect to the tip surface 24a. By providing the two inclined surfaces 34 in the peripheral area sa1, it is possible to further widen the light distribution angle while suppressing a decrease in the amount of light.

It is preferable that the light distribution of the illumination light emitted from the peripheral area sa, which is the light transmission area, be uniform as a whole.

In FIG. 11, when the tip end face 24a is viewed from a direction orthogonal to the tip end face 24a, the projected area (second area) of the inclined face 31a onto the tip end face 24a is A, and the projected area of the inclined face 31b onto the tip end face 24a. Let B be the (second area), let C be the projected area (second area) of the inclined surface 31c onto the tip surface 24a, and as shown in FIG. ), let D be the area (first area) of the peripheral region sa in the range of . The peripheral area sa has a triangular shape without a central portion which is a projected portion of the three inclined surfaces 31a, 31b, and 31c.

That is, when the distance between the two parallel sides EL of the two adjacent recesses 31 is d, the area surrounded by the imaginary line L2 separated from each side EL by the distance (d/2) is the peripheral area sa (indicated by hatching).

As shown in FIG. 11, the length of one side EL of the recess 31 is a, and the length of one side of the peripheral region sa is b.

The ratio r of D to A (or B or C) is preferably 1 in order to make the two-dimensional light distribution of the illumination light emitted from the tip surface 24a uniform. If the ratio of D to A (or B or C) is 1, the amount of light emitted from the peripheral area sa after being totally reflected by each of the inclined surfaces 31a, 31b, and 31c is The amount of light emitted from the peripheral area sa is equal to that of the light emitted from the peripheral area sa without being totally reflected, so that uniform illumination can be obtained.

However, practically, the ratio r may be in the range of (1/3) to 3, even if it is not 1. That is, it is preferable that (1/3)<r<3. If the ratio r is out of this range, the amount of light emitted from the peripheral area sa after being totally reflected by each of the inclined surfaces 31a, 31b, and 31c is , the amount of light directly emitted from the peripheral area sa is biased, and the two-dimensional light distribution becomes non-uniform, leading to illumination unevenness.

That is, when the projected area of each peripheral region sa and the inclined surface 31a (or 31b or 31c) onto the tip surface 24a when the tip surface 24a is viewed from the direction perpendicular to the tip surface 24a is defined as D and A), respectively. , D to A is preferably a value in the range of greater than (1/3) and less than three.

A, B, C, and D are expressed by the following formulas (1) and (2).

The following equation (3) holds from equations (1) and (2).

For example, to set A=D, (b/a) is given by the following equation (5) from the following equation (4).

Therefore, for example, to satisfy (1/3)<(D/A)<3, Equation (8) is obtained from Equations (6) and (7) below.

Further, for example, when the tip end surface of the rod lens 24 is a ring-shaped tip end surface 24Aa as shown in FIG. Φin is the inner diameter of the cylindrical rod lens 24A, and Φout is the outer diameter of the cylindrical rod lens 24A.

A plurality of recesses 31 as described above are formed on the tip surface 24a of the rod lens 24, and a peripheral region sa is provided around each recess 31. is diffused by each concave portion 31 of the tip end surface 24a of and the peripheral region sa surrounding each concave portion 31. As shown in FIG. In particular, the light that hits the three slopes 31a, 31b, and 31c of each concave portion 31 is totally reflected and then emitted from the peripheral region sa, which is a transmission region, so that the amount of light decreases very little. Also, part of the light from the base end surface 24b of the rod lens 24 is directly emitted from the peripheral area sa without being totally reflected by the concave portion 31 .

In particular, two adjacent recesses 31 diffuse light from the peripheral region sa in six directions. FIG. 14 is a diagram for explaining the emission direction of light.

As shown in FIG. 14, in two adjacent concave portions 31, light reflected by each of the inclined surfaces 31a, 31b, and 31c travels from the peripheral region sa in six directions D1, D2, D3, D4, D5, and D6. Since the light is emitted, there is little light distribution unevenness.

Furthermore, the shape of the opening of the recess 31 may be an isosceles triangle, a right triangle, or the like instead of the equilateral triangle.

As described above, in the present embodiment, light reflected by each of the inclined surfaces 31a, 31b, and 31c is totally reflected and emitted from the peripheral area sa. In the conventional technology, the totally reflected light becomes return light and does not exit from the exit surface, resulting in a loss of light intensity. Light loss can be reduced. Further, since the configuration is such that the totally reflected light is transmitted from the peripheral region sa, it is not necessary to reduce the angles of the inclined surfaces 31a, 31b, and 31c in order to reduce the return light, and the wideness of the light distribution angle can be maintained. I can.

Therefore, according to the embodiment described above, it is possible to provide an illumination optical system for an endoscope that can widen the light distribution while reducing the amount of decrease in the amount of emitted light.

Next, a modification of the embodiment described above will be described.
(Modification 1)

In the above-described embodiment, each concave portion 31 has a regular triangular pyramid shape with the bottom surface up and the apex down. When viewed from the surface 24a, it is positioned at the center of gravity of the equilateral triangle. However, when the tip surface 24a is viewed from the direction orthogonal to the tip surface 24a, the deepest part of each recess is shifted from the center of gravity. It may be in position.

FIG. 15 is a diagram for explaining the position of the deepest part of the concave portion 31A according to Modification 1. As shown in FIG.

As shown in FIG. 15, the deepest part of the concave portion 31A is located at a point Q deviated from the point P, which is the position of the center of gravity.

Therefore, the inclination angles α1 and α2 of the two adjacent planes of the two adjacent recesses 31A shown in FIG. 15 are angles within the range of more than 3 degrees and less than 20 degrees. In other words, 70°<(90−α1)<97° and 70°<(90−α2)<97°. The tilt angles α1 and α2 may be the same or different.

Light distribution can be adjusted by changing the position of the deepest part of the recess 31A. Alternatively, the light distribution can be adjusted by changing the inclination angles of the inclined surfaces 31a, 31b, and 31c of the recess 31A.

As described above, the same effects as those of the above-described embodiment can be obtained by the first modification.
(Modification 2)

Although the recesses 31 and 31A have a triangular pyramid shape in the above-described embodiment and modification 1, the recesses may have a quadrangular pyramid shape.

FIG. 16 is a diagram for explaining a concave portion 31B according to Modification 2. As shown in FIG.

As shown in FIG. 16, each concave portion 31B has a rectangular bottom surface parallel to the tip end surface 24a of the rod lens 24 when an object OB (not shown) having a square pyramid shape is fitted into the concave portion 31B with the bottom surface facing up. It has a shape such that

Therefore, the recess 31B has four inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd. The four inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd have a square shape when the tip surface 24a is viewed from a direction orthogonal to the tip surface 24a. A point 33B where four boundary lines of two adjacent inclined surfaces join together is the deepest part of the recess 31B. The angles of the inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd with respect to the tip surface 24a are equal.

That is, each recess 31B has a quadrangular pyramid shape with the apex as the deepest part and a square bottom as an opening. , 31Bc, 31Bd).

The opening of each recess 31B has a square shape. The aperture has four sides EL. A peripheral area sa (indicated by diagonal lines) is provided so as to surround the opening of each recess 31B. A transmissive region having a width d1 is provided between two adjacent parallel sides EL of two adjacent recesses 31B. Two peripheral regions sa of two adjacent recesses 31B constitute a transmission region between two adjacent recesses 31B.

In FIG. 16, when the tip end face 24a is viewed from a direction perpendicular to the tip end face 24a, A is the projected area of the inclined face 31Ba onto the tip end face 24a, and B is the projected area of the inclined face 31Bb onto the tip end face 24a. Let C be the projected area of the surface 31Bc onto the distal end surface 24a, and D be the projected area of the inclined surface 31Bd onto the distal end surface 24a. As shown in FIG. ) is the area of the peripheral region sa. The peripheral area sa has a quadrangular shape without a central portion that is a projected portion of the four inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd.

That is, when the distance between the two parallel sides EL of the two adjacent recesses 31B is d1, the area surrounded by the imaginary line separated from each side EL by the distance (d1/2) is the peripheral area sa ( shown with diagonal lines).

The inclination angle α3 of each of the inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd with respect to the tip surface 24a ranges from 5° to 25°. In other words, the angle (90-α3) of each total reflection surface with respect to the tip surface 24a is an angle between less than 85 degrees and greater than 65 degrees, that is, 65°<(90-α3)<85°. .

As shown in FIG. 16, the length of the side EL of the recess 31B is a1, and the length of one side of the peripheral region sa is b1.

In order to homogenize the two-dimensional light distribution of the illumination light emitted from the tip surface 24a, as described above, the ratio of E to A (or B or C or D) should be in the range of (1/3) to 3. preferably in

For example, for A and E, the following equation (11) holds.

From equation (11), the following equation (12) holds.

Therefore, setting (1/3)<(E/A)<3 means that the following equation (13) holds.

Equation (14) is obtained from equation (13).

From equation (14), the following equation (15) holds.

Therefore, when the concave portion has a quadrangular pyramid shape, the transmissive region preferably satisfies the relationship of the above formula (15).

As described above, the same effects as those of the above-described embodiment can be obtained by the second modification.

It should be noted that, even in the present modified example 2, the deepest part may be located at a position shifted from the center of gravity as in the modified example 1. FIG. That is, the deepest point 33C of the quadrangular pyramid-shaped concave portion may be located at a position deviated from the center of gravity of the square.

FIG. 17 is a diagram for explaining the position of the deepest part of the recess 31C, where the deepest part of the recess is shifted from the center of gravity of the square. As shown in FIG. 17, the deepest point 33C of the concave portion 31C is located at a position shifted from the center of gravity. The drawing at the bottom of FIG. 17 shows a cross section of the tip surface 24a along the two-dot chain line LL at the top.

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

In the case of FIG. 17, when the tip end face 24a is viewed from the direction orthogonal to the tip end face 24a, and the projected areas of the inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd onto the tip end face 24a are A, B, C, and D, respectively, The following expressions (16) and (17) hold.

Light distribution in four directions can be adjusted by changing the position of the deepest part of the recess 31C. Alternatively, the light distribution can be adjusted by changing the inclination angles of the inclined surfaces 31Ba, 31Bb, 31Bc, and 31Bd of the concave portion 31C.

Furthermore, the shape of the opening of the recess 31C may be rectangular instead of square. By making the shape of the opening of the recess 31C rectangular, it is possible to further adjust the light distribution in four directions. Also, the position of the deepest part of the rectangle may be shifted from the center of gravity.

As described above, the same effects as those of the above-described embodiment can be obtained by the second modification.
(Modification 3)

In the above-described embodiment and Modification 1, the recesses 31 and 31A have a triangular pyramid shape, and in Modification 2, the recess 31B has a quadrangular pyramid shape, but the recess has a hexagonal pyramid shape. may have.

18 and 19 are diagrams for explaining the recess 31D according to Modification 3. FIG.

As shown in FIG. 18, each recess 31D has a hexagonal bottom surface that is aligned with the tip surface 24a of the rod lens 24 when a regular hexagonal pyramidal object OB (not shown) is fitted into the recess 31D with the bottom surface facing up. It has a parallel shape.

Therefore, each recess 31D has six inclined surfaces 31Da, 31Db, 31Dc, 31Dd, 31De, and 31Df. The six inclined surfaces 31Da, 31Db, 31Dc, 31Dd, 31De, and 31Df have regular hexagons when viewed from a direction perpendicular to the tip end face 24a. A point 33D where six boundary lines of two adjacent inclined surfaces join together is the deepest part of each recess 31D. The angles of the inclined surfaces 31Da, 31Db, 31Dc, 31Dd, 31De, and 31Df with respect to the tip surface 24a are equal.

That is, each recess 31D has a hexagonal pyramidal shape with an apex as the deepest part and a regular hexagonal bottom as an opening, and the plurality of total reflection surfaces are six planes (inclined surfaces 31Da , 31Db, 31Dc, 31Dd, 31De, 31Df).

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

As shown in FIG. 19, there is a transmissive region having a width d2 between two parallel sides EL of two adjacent recesses 31D. The drawing on the right side of FIG. 19 shows a cross section of the tip surface 24a along the two-dot chain line LL1 on the left side.

18 and 19, when the tip end face 24a is viewed from the direction orthogonal to the tip end face 24a, A is the projected area of the inclined face 31Da onto the tip end face 24a, and B is the projected area of the inclined face 31Db onto the tip end face 24a. Let C be the projected area of the inclined surface 31Dc onto the distal end surface 24a, D be the projected area of the inclined surface 31Dd onto the distal end surface 24a, E be the projected area of the inclined surface 31De onto the distal end surface 24a, and E be the projected area of the inclined surface 31Df. is projected onto the tip end face 24a, and as shown in FIG. The peripheral area sa has a hexagonal shape without a central portion, which is a projected portion of the six inclined surfaces 31Da, 31Db, 31Dc, 31Dd, 31De, and 31Df.

That is, when the distance between the two parallel sides EL of the two adjacent recesses 31D is d2, the area surrounded by the imaginary line separated from each side EL by the distance (d2/2) is the peripheral area sa ( shown with diagonal lines).

The inclination angle α6 of each of the inclined surfaces 31Da, 31Db, 31Dc, 31Dd, 31De, and 31Df with respect to the tip end surface 24a ranges from 3° to 20°. In other words, the angle (90-α6) of each total reflection surface with respect to the tip surface 24a is an angle between less than 87 degrees and greater than 70 degrees, that is, 70°<(90-α6)<87°. .

FIG. 20 is a plan view of part of the inclined surface 31Dc and the peripheral area sa. The length of one side EL of the recess 31D is a2, and the length of one side of the peripheral region sa is b2.

For example, the area C of the projected surface of the inclined surface 31Dc onto the tip surface 24a and the area G1 of the part of the peripheral region sa near the inclined surface 31Dc are given by the following equations (21) and (22), respectively.

Then, from the equations (21) and (22), the ratio of the area G of the peripheral region sa to the area C of the projected surface of the inclined surface 31Dc onto the tip surface 24a is given by the following equation (23).

In order to homogenize the two-dimensional light distribution of the illumination light emitted from the tip surface 24a, as described above, the ratio of G to C (or A or B or D or E or F) is (1/3) It is preferably in the range of ~3.

Equations (24), (25) and (26) are obtained from Equation (23).

Therefore, when the concave portion has a hexagonal pyramid shape, the peripheral area sa preferably satisfies the relationship of formula (26) above.

As described above, the same effects as those of the above-described embodiment can be obtained by the modification 3 as well.

It should be noted that, even in this modified example 3, the deepest part may be located at a position deviated from the center of gravity as in the modified example 1. FIG. That is, the deepest point 33D of the hexagonal pyramid-shaped recess may be located at a position shifted from the center of gravity of the square.
(Modification 4)

In the above-described embodiment and modification 1, the recesses 31 and 31A have a triangular pyramid shape, in modification 2 the recesses 31B and 31C have a quadrangular pyramid shape, and in modification 3 the recess 31D , has a hexagonal pyramid shape, but the recess may have a conical shape or a polypyramidal shape close to a conical shape.

Modification 4 can also provide the same effects as those of the above-described embodiment.
(Modification 5)

In the embodiment and each modified example described above, the plurality of inclined surfaces 31a and the like of each recess and the peripheral region sa are partitioned by three or more sides EL of the opening of the recess. Between the regions sa, there may be provided a flat portion or a curved portion connecting each of the inclined surfaces 31a and the like to the peripheral region sa.

For example, a flat portion formed by chamfering the side EL portion may be provided between each inclined surface and the peripheral area sa. Furthermore, a plurality of flat portions may be present between each inclined surface and the peripheral area sa.

Alternatively, a curved surface portion having a gentle curve connecting each inclined surface 31a and the like to the peripheral area sa may be present between each inclined surface and the peripheral area sa.

Modification 5 can also provide the same effects as those of the above-described embodiment.
(Modification 6)

In the embodiment and each modified example described above, the shapes of the plurality of recesses formed in the tip surface 24a are the same. However, it is not limited to this, and recesses of different shapes may be mixed and formed on the tip surface 24a. For example, on the tip surface 24a, which is the emission surface, there are two regions: a region in which a plurality of triangular pyramid-shaped concave portions 31 are formed as the diffusion region DS, and a region in which a plurality of quadrangular pyramid-shaped concave portions 31B are formed as the diffusion region DS. A plurality of recessed regions having different recessed shapes may be mixed on the tip surface 24a by, for example, providing a recessed region.

According to Modification 6 as well, the same effects as those of the above-described embodiment can be obtained.
(Modification 7)

In the above-described embodiment and modifications 1 to 6, the tip surfaces 24a and 24Aa of the rod lenses 24 and 24A are provided with diffusion structures (diffusion regions DS for diffusing emitted light). Alternatively, the diffusion structure may be provided in a separate member.

FIG. 21 is a diagram for explaining the configuration on the optical path of the illumination light within the optical adapter 10 according to Modification 7. As shown in FIG. A configuration including the cover glass 22a and the rod lens 24 will be described below as an example, but the same applies to a configuration including the cover glass 22Aa and the rod lens 24A.

For example, the plate member 26 is arranged between the cover glass 22a and the rod lens 24. As shown in FIG. 21, the plate member 26 is arranged at a position separated from the rod lens 24, but the plate member 26 may be joined to the rod lens 24 using an adhesive or the like.

The plate member 26 is made of transparent glass or transparent plastic, for example. A diffusing structure for diffusing emitted light is formed on the tip surface 26 a of the plate member 26 . As described above, the diffusion structure is configured as a diffusion region DS including a plurality of recesses 31 (or recesses 31A, 31B, 31C, 31D, etc.) and a plurality of peripheral regions sa (or peripheral region sa1). The plate members 26 may be cut from a large piece of material with diffusion structures formed therein so that a plurality of plate members 26 may be manufactured at the same time.

The light incident on the proximal end surface 24b of the rod lens 24 from the light guide 25 passes through the rod lens 24, is emitted from the distal end surface 24a of the rod lens 24, and is incident on the proximal end surface 26b of the plate member 26. The light that has passed through the plate member 26 is diffused by the diffusion region DS, emitted from the tip surface 26a, and enters the cover glass 22a.

Also in Modification 7, the cover glass 22a may be provided with a grained surface (indicated by a dotted line) in order to eliminate uneven light distribution. It does not matter if the grained surface is not provided.

According to Modification 7, the same effects as those of the above-described embodiment can be obtained, and the existing rod lens 24 can be used without the need to process the tip surface 24a of the rod lens 24 to provide the diffusion region DS. .
(Modification 8)

In the above-described embodiment and modifications 1 to 7, the elongated semicircular illumination window 22 as shown in FIG. 2 or the ring-shaped illumination window 22A as shown in FIG. 4 is provided. . However, the shape of the illumination window is not limited to these. As the illumination window, an illumination window of various shapes such as a circular shape, a polygonal shape, or a combination of a plurality of figures may be employed. Also, the number of illumination windows is not limited to one, and a plurality of illumination windows may be provided. For example, two circular illumination windows may be provided.

According to Modification 8 as well, effects similar to those of the above-described embodiment can be obtained, and the degree of freedom in layout of the lighting windows is increased.

In the above-described embodiment and modifications 1 to 8, the endoscope is a direct-view endoscope, but the above-described embodiment and modifications can also be applied to side-view or oblique-view endoscopes. be.

As described above, according to the above-described embodiments and modifications, an illumination optical system for an endoscope, an optical adapter, and an endoscope that can widen the light distribution while reducing the amount of decrease in the amount of emitted light are provided. can be realized.

The present invention is not limited to the above-described embodiments, and various modifications and alterations are possible without departing from the gist of the present invention.

Reference Signs List 1 endoscope device 2 device main body 3 endoscope 4 display unit 5 insertion unit 6 operation unit 6a bending joystick 7 universal cord 10, 10A optical adapter 10a tip surface 10b housing 11, 11A tip portion 12 bending portion 13 flexible portion 21, 21A observation window 21Aa, 21a cover glass 21b lens group 22, 22A illumination window 22a, 22Aa cover glass 22a1, 22a2, 22Aa1, 22Aa2 glass, 23 image sensor, 23a signal line, 24, 24A rod lens, 24a, 24Aa distal end surface, 24b, 24Ab base end surface, 24c straight portion, 25, 25A light guide, 26 plate member, 31, 31A, 31B, 31C, 31D concave portion , 31Ba, 31Bb, 31Bc, 31Bd Inclined surface 31Da, 31Db, 31Dc, 31Dd, 31De, 31Df Inclined surface 31a, 31b, 31c Inclined surface 32a, 32b, 32c Boundary line 33, 33B, 33C, 33D Deepest part point, 34 slope, sa, sa1 peripheral area.

Claims (15)

An illumination optical system for an endoscope having an insertion section to be inserted into a subject,
An optical element having an incident surface on which light is incident as incident light and an exit surface from which the light is emitted as illumination light,
the emission surface has a diffusion area for diffusing the emission light,
the diffusion region has a plurality of recesses and a plurality of peripheral regions arranged on the exit surface;
each recess has a plurality of total reflection surfaces that are inclined with respect to the exit surface and that totally reflect the incident light;
at least one of the plurality of total internal reflection surfaces is inclined at a first angle with respect to the exit surface;
each peripheral region is formed to surround the plurality of total reflection surfaces;
I: Reflected light totally reflected by the total reflection surface after passing through the incident surface;
and II: having a transmission surface that transmits and emits the incident light that has not been totally reflected by the total reflection surface after passing through the incident surface;
Illumination optical system for endoscopes. Each recess has a triangular pyramid shape with an apex as the deepest portion and an equilateral triangle bottom as an opening,
The plurality of total reflection surfaces are three planes excluding the bottom surface of the triangular pyramid,
The illumination optical system for an endoscope according to claim 1. The angle of each total reflection surface with respect to the exit surface is an angle between 85 degrees or less and greater than 70 degrees.
The illumination optical system for an endoscope according to claim 2. each of the peripheral regions is parallel to the exit surface;
The illumination optical system for an endoscope according to claim 1. each peripheral region has a second angle greater than 0 degrees and less than the first angle with respect to the exit surface;
The illumination optical system for an endoscope according to claim 1. The plurality of recesses are arranged on the exit surface such that two adjacent sides of two adjacent recesses are parallel to each other.
The illumination optical system for an endoscope according to claim 1. When the projected areas of the peripheral regions and the total reflection surfaces on the exit surface when the exit surface is viewed from a direction perpendicular to the exit surface are defined as a first area and a second area, respectively, The ratio of the first area to the two areas is a value in the range of greater than (1/3) and less than 3.
The illumination optical system for an endoscope according to claim 1. Each of the recesses has a quadrangular pyramid shape with an apex as the deepest portion and a square or rectangular bottom surface as an opening,
The plurality of total reflection surfaces are four planes excluding the bottom surface of the quadrangular pyramid,
The illumination optical system for an endoscope according to claim 1. The angle of each total reflection surface with respect to the exit surface is an angle between less than 85 degrees and greater than 65 degrees.
The illumination optical system for an endoscope according to claim 8. Each recess has a hexagonal pyramid shape with an apex as the deepest part and a regular hexagonal bottom as an opening,
The plurality of total reflection surfaces are six planes excluding the bottom surface of the hexagonal pyramid,
The illumination optical system for an endoscope according to claim 1. The angle of each total reflection surface with respect to the exit surface is an angle between less than 87 degrees and greater than 70 degrees.
The illumination optical system for an endoscope according to claim 10. Each of the recesses has a polygonal pyramid shape with the apex as the deepest portion and a regular polygonal bottom surface as an opening,
When the exit surface is viewed from a direction perpendicular to the exit surface, the vertex is located at the center of gravity of the regular polygon.
The illumination optical system for an endoscope according to claim 1. The endoscope is a direct viewing endoscope,
The incident surface and the exit surface of the optical element are parallel,
The illumination optical system for an endoscope according to claim 1. An optical adapter that can be attached to the distal end of an insertion section that is inserted into a subject,
An optical element having an incident surface on which light is incident as incident light and an exit surface from which the light is emitted as illumination light,
the emission surface has a diffusion area for diffusing the emission light,
the diffusion region has a plurality of recesses and a plurality of peripheral regions arranged on the exit surface;
each recess has a plurality of total reflection surfaces that are inclined with respect to the exit surface and that totally reflect the incident light;
at least one of the plurality of total internal reflection surfaces is inclined at a first angle with respect to the exit surface;
each peripheral region is formed to surround the plurality of total reflection surfaces;
I: Reflected light totally reflected by the total reflection surface after passing through the incident surface;
and II: having a transmission surface that transmits and emits the incident light that has not been totally reflected by the total reflection surface after passing through the incident surface;
optical adapter. An optical element having an incident surface on which light is incident as incident light and an exit surface from which the light is emitted as illumination light,
the emission surface has a diffusion area for diffusing the emission light,
the diffusion region has a plurality of recesses and a plurality of peripheral regions arranged on the exit surface;
each recess has a plurality of total reflection surfaces that are inclined with respect to the exit surface and that totally reflect the incident light;
at least one of the plurality of total internal reflection surfaces is inclined at a first angle with respect to the exit surface;
each peripheral region is formed to surround the plurality of total reflection surfaces;
I: Reflected light totally reflected by the total reflection surface after passing through the incident surface;
and II: having a transmission surface that transmits and emits the incident light that has not been totally reflected by the total reflection surface after passing through the incident surface;
an illumination optical system for an endoscope;
an insertion section inserted into a subject;
an endoscope.

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