JPH08286125A - Illumination optical system for endoscope - Google Patents

Abstract

PURPOSE: To provide an illumination optical system for an endoscope capable of accomplishing a high NA (distribution angle) even in the case of using a light guide whose NA is low, as for an endoscope whose diameter is small and whose visual field is large. CONSTITUTION: As for the endoscope with a slender insertion part provided with an illumination optical system 3 constituted of the light guide 4 for transmitting light emitted from a light source and an illuminating lens group arranged in front of the end face 5 on an object side of the light guide 4, an objective optical system 2 and an image transmitting means arranged in order from the object surface side, the illuminating lens group is the illumination optical system for the endoscope including at least one optical element 7 whose incident end face opposite to the light guide 4 includes an inclined plane inclined with reference to the emitting end face 5 of the light guide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination optical system for an endoscope.

[0002]

2. Description of the Related Art In recent years, an elongated insertion portion has been inserted into an internal inspection of equipment such as a water supply pipe for cooling water in a nuclear power plant or an inside of an aircraft engine that is not easy to disassemble or cannot be disassembled. BACKGROUND ART Endoscopes capable of observing internal conditions and confirming the presence or absence of damage are widely used, and the role played by them is increasing year by year with the development of various industries.

A conventional endoscope includes an objective optical system including an objective lens and an image transmitting means, and an illumination optical system including an illumination lens and a light guide for transmitting light from a light source.

The illuminating lens is arranged on the front side of the light guide facing the object side and is usually a concave lens. here,
It is preferable to use a light guide having a large light distribution angle (hereinafter referred to as NA) as much as possible in order to improve the workability of the concave lens placed on the front surface of the exit end and to reduce the vignetting of light rays in the periphery. . As a light guide having a large NA, a multi-component light guide composed of multi-components is often used.

[0005]

In a conventional endoscope, in a nuclear power plant, which is a typical place of use in the industrial field, neutron rays and γ rays are generated due to a nuclear reaction in a nuclear reactor.
Since lines are emitted, if an endoscope is used in this, not only external components but also internal components, a light guide, an optical lens, and in the case of an electronic endoscope, a solid-state image sensor, etc. are all included. It is exposed to radiation and is affected by radioactivity, which has a significant adverse effect on endoscopic images. Above all, the multi-component light guide has a weak radioactivity resistance, and the light transmittance becomes almost zero after use, which makes it unusable.

On the other hand, it is well known that, in contrast to a multi-component light guide, a light guide whose main component is quartz has a strong radiation resistance. When the quartz light guide is applied to the endoscope, it has relatively good durability even in the radiation region. However, unlike a multi-component light guide, a quartz light guide generally has a small NA. In order to widen the emitted light having a small NA in order to improve the light distribution, the radius of curvature of the concave lens arranged in front of the light guide must be made extremely small, resulting in poor workability.

Further, the endoscope is an insertion device, and it is desired that the endoscope has a smaller diameter, and the outer diameter of the distal end portion is restricted by the size. When a low NA light guide and an objective optical system with a wide viewing angle are combined, even if an attempt is made to reduce the radius of curvature of the illumination concave lens as well, there is a problem in that production is not possible due to the outer diameter restriction.

The present invention has been made in view of the above problems of the prior art. The object of the present invention is to provide a small-diameter wide-field endoscope like a quartz light guide. It is an object of the present invention to provide an endoscope illumination optical system capable of sufficiently illuminating the periphery of a visual field even when a light guide having a small NA is used.

[0009]

To achieve the above object, an endoscope illumination optical system according to the present invention comprises a light guide for transmitting light from a light source and an illumination lens arranged in front of the object-side end face of the light guide. In an endoscope having an elongated insertion portion including an illumination optical system including a group, an objective optical system in order from the object plane side, and an image transmission unit, the illumination lens group has an incident end surface facing the light guide. At least one optical element including an inclined surface inclined with respect to the exit end surface of the light guide is included.

Further, according to the present invention, the shape of the cross section perpendicular to the optical axis of the illumination lens and the shape of the cross section perpendicular to the optical axis of the light guide are different from each other.

Furthermore, according to the invention, at least one tubular reflector is arranged on the object side of the illumination lens.

Further, according to the present invention, the cross section perpendicular to the optical axis direction of the optical element and the cross section perpendicular to the optical axis rear direction of the cylindrical reflector are different from each other in shape.

Further, according to the present invention, the entrance end surface of the optical element is formed of one surface inclined with respect to the exit end surface of the light guide, or the directions of the inclination with respect to the exit end surface of the light guide are different from each other. It is composed of two inclined surfaces or four inclined surfaces having different inclination directions with respect to the exit end surface of the light guide.

Further, according to the present invention, the optical element is formed by combining a plurality of transparent optical members each having an inclined surface such that the directions of the inclined surfaces are different from each other, or in the optical axis direction. The shape of the cross section perpendicular to is substantially non-circular, or the shape of the cross section perpendicular to the optical axis direction is substantially rectangular or substantially square including an arc.

Furthermore, according to the present invention, the adapter is detachably provided at the tip of the insertion portion of the endoscope.

Further, according to the present invention, the optical element has the periphery mirror-polished or a metal vapor deposition film provided on the periphery.

Furthermore, according to the present invention, an illumination optical system including a light guide for transmitting light from a light source, an illumination lens group arranged in front of the object-side end face of the light guide, and an objective optical system in order from the object plane side. In an endoscope apparatus including an endoscope main body having an elongated insertion portion including a system and an image transmission unit, and a detachable adapter at a tip of the insertion portion, an illumination lens group and an exit end surface of a light guide. Between at least 1
An optical element that converts the numerical aperture of the illumination light is arranged.

Further, according to the present invention, the optical element for converting the numerical aperture is arranged in the endoscope body.

[0019]

The light from the light source is emitted from the end surface of the light guide on the object side with a low NA and is guided to the incident end surface of the optical element. Since at least one of the incident end faces of this optical element is not parallel to the object-side end face of the light guide, the light distribution angle of the light emitted from the optical element is the original distribution angle due to the law of refraction. Will be larger than.

Further, since the area of the cross section of the illumination lens perpendicular to the optical axis is larger than the cross-sectional area of the light guide perpendicular to the optical axis, the light emitted from the vicinity of the peripheral edge of the end face of the light guide on the object side is outside. Even if diffused into, it can pass through the illumination lens. Furthermore, since the area of the exit end surface of the illumination lens is larger than the area of the entrance end surface of the illumination lens, the law of refraction works more,
The light passing through it can be emitted as light having a larger light distribution angle.

Further, when the tubular reflector is installed in front of the illumination lens, the light emitted from the illumination lens can be reflected by the side surface of the tubular reflector and averaged.

[0022]

Embodiments of the present invention will be described below. 1 to 4 are explanatory views of a first embodiment of an endoscope illumination optical system according to the present invention.

FIG. 1 is a sectional view of the object side tip of the endoscope illumination optical system according to the present invention, and FIG. 2 is a front view of the object side tip seen from the direction of the arrow in FIG. In FIGS. 1 and 2, reference numeral 1 denotes an endoscope distal end portion, which includes an objective optical system 2, a solid-state imaging device (not shown), and an illumination optical system 3.

In particular, the illumination optical system 3 is a quadrangular pyramid-shaped optic with the apex 6 directed toward the object-side end face 5 of the light guide 4 in front of the object side of the light guide 4 made of quartz with NA = 0.35. The device 7 is arranged.

FIG. 3A is a perspective view of the optical element 7,
(B) is an enlarged view showing a positional relationship between the optical element 7 and the light guide 4. In FIGS. 3A and 3B, 8 and 9 are slopes of the optical element 7, and are formed so that the angle α with the bottom surface 10 is 22 °. The refractive index of the optical element 7 is 1.78472.

In the thus constructed endoscope illumination optical system 3, the principle by which the NA of the light beam emitted from the light guide 4 is converted via the optical element 7 will be described below with reference to FIG. In FIG. 4, the object-side end surface 5 of the light guide 4
The luminous flux emitted from is NA = 0.35, that is, θ =
After being distributed at 40 °, the light is then incident on the slopes 8 and 9 of the optical element 7, and after passing through the optical element 7 according to the law of refraction, θ ′ =
It is emitted with a luminous flux of 80 °. In this way, the NA of the light flux finally increases by about 40 °.

Although the above ray tracing is performed only in the direction with respect to the slopes 8 and 9, the same can be said in the direction perpendicular to this. Further, as in the present embodiment, if an optical element having a slender cross section is used, the internal space at the tip of the endoscope can be used more effectively than that having a circular cross section, and the cross sectional area becomes large to increase the light quantity as much as possible. can do.

Further, according to the structure of this embodiment, even when the quartz NA light guide 4 is used for the endoscope illumination optical system 3, a good light distribution is achieved to the periphery without using a polishing lens. Can be obtained.

FIG. 5A is a perspective view of the optical element 11,
(B) is an enlarged view showing the positional relationship between the optical element 11 and the light guide 4, and (c) is a front view of the distal end portion of the endoscope in which the optical element 11 is arranged.

In FIGS. 5 (a), 5 (b) and 5 (c),
The optical element 11 is an optical element having a shape as shown in FIGS. 5A and 5B, and is arranged as shown in FIGS. 5B and 5C. Optical element 1 having such a shape
If 1 is used, the area facing the object-side end surface 5 of the light guide 4 is larger than that of an optical element having a rectangular cross section, and the amount of light can be increased.

Further, like the optical element 12 shown in FIG. 5D, the surface of the optical element 12 projected to the light guide 4 side is different from the object side end surface 5 of the light guide 4 and more than the end surface 5. When the optical element having a large area is used and the light guide 4 is arranged as shown in FIGS. 5D and 5E,
As shown in FIG. 5E, the object-side end surface 5 of the light guide 4
The light flux emitted from the vicinity of the peripheral edge of the light guide can also enter the optical element 12, and the light quantity transmitted through the light guide 4 can be used without leakage.

6 to 9 are explanatory views of a second embodiment of the endoscope illumination optical system according to the present invention. FIG. 6 shows a front view of the distal end portion of an endoscope including the endoscope illumination optical system according to the present invention. In FIG. 6, reference numeral 13 denotes a distal end portion of the endoscope, in which an objective lens 14 and an optical element 15 having a square cross section are arranged below the objective lens 14.

FIG. 7 shows a perspective view of the optical element 15. 8 shows the positional relationship between the optical element 15 and the light guide 4. In FIG. 7, the optical element 15
Is an optical element having a square base and a pyramid-shaped apex angle, and is arranged with the apex angle opposed to the object-side end surface 5 of the light guide 4. The light guide 4 is formed into a substantially square shape according to the layout of the endoscope tip.

When the illumination optical system having such a structure is used, the light beam emitted from the light guide 4 passes through the optical element 15 so that the light beam can be divided into four spotlights for irradiation.

By the way, in the industrial field, a side wall inside a tubular object such as a pipe may be observed using an endoscope. Since the purpose is to find cracks or damages inside the pipe, it is desirable that the observation field of view be wide. Further, in recent years, the endoscope is becoming electronic, and it is often observed on a TV monitor.

The case where the optical element 15 is used as an endoscope for observing the inside of the pipe will be described below.
FIG. 9 shows an optical element 15 in the endoscope illumination optical system according to the present invention.
It is the figure which showed the TV monitor image at the time of using. 10 does not use the endoscope illumination optical system according to the present invention,
It is the figure which showed the TV monitor image which projected the inside of a pipe. FIG. 11 is a diagram showing a TV monitor image when the optical element 15 is used in the endoscope illumination optical system according to the present invention.

When the inside of the pipe is observed using the endoscope constructed as shown in FIGS. 6 to 8, the observation field of view becomes a quadrangle as shown in the TV monitor frame 16 of FIG. When the inside is observed, the result is as shown in FIG. 10 on the TV monitor, and the front center part (the center of the pipe) 17 is completely dark because there is no subject. Therefore, it is useless to illuminate the vicinity of the center of the field of view, and if the amount of light illuminating the vicinity of the center of the field of view is dispersed to the periphery of the field of view, the amount of light around the field of view can be increased and a farther subject can be observed. it can.

In this embodiment, a pyramidal optical element 15 is arranged in front of the end face of the light guide 4 on the object side, and the light distribution shape is divided into four parts like a spotlight as shown in FIG. Thus, the light flux passing through the light guide 4 can be concentratedly applied to the four corners of the observation visual field without irradiating the periphery of the pipe center 17 to increase the light amount, and the depth of the observation area can be increased.

Further, based on the same idea, when the observation field of view has a rectangular shape, a light distribution shape similar to that of the observation field of view can be obtained by using an optical element having two light guide facing surfaces. it can.

12 and 13 are explanatory views relating to the third embodiment of the endoscope illumination optical system according to the present invention. 12
(A) is an exploded perspective view of the optical element 18, (b)
FIG. 6 is an enlarged view showing a positional relationship between the optical element 18 and the light guide 4. FIG. 13 is an explanatory diagram showing a problem when another optical element is used.

In FIG. 12 (a), reference numeral 18 denotes an optical element having a recessed central portion 19 formed by joining two optical elements 18a and 18b in front of the light guide 4 on the object side. As shown in b), the edges 18c and 18d are
The light guide 4 is arranged so as to come into contact with the object-side end surface 5.

When the optical element having the above-mentioned structure is used, in addition to the optical effect similar to that of the first embodiment, another advantage is the assembling property. For example, in the first embodiment,
In FIG. 4, if the vertex 6 of the optical element 7 comes into contact with the object-side end surface 5 of the light guide 4, damage is likely to occur. Therefore, it is necessary to fix the optical element 7 with the frame 19 having a complicated shape as shown in FIG. 13 so as to avoid the contact.

However, the optical element 18 used in this embodiment is
Can be abutted against the object-side end surface 5 of the light guide 4 at the edge portions 18c and 18d, so that the frame structure can be simplified as shown in FIG. 12 (b).

Further, there is a problem that it is very difficult to integrally process an optical element having a depressed central portion as used in this embodiment. However, as in this embodiment, two optical elements are joined together. By assembling in, processing can be performed relatively easily.

FIG. 14 is an explanatory view of a fourth embodiment of the endoscope illumination optical system according to the present invention. In FIG.
Reference numeral 20 is a single fiber that is formed in front of the light guide 4 on the object side and is joined to the optical element 7 used in the first embodiment to form an integrated optical element.

When the optical element having such a structure is used, a light beam having a low NA is generated by the optical element 7 as in the first embodiment.
Is converted into a large light distribution angle, and when passing through the single fiber 20, it is possible to obtain good illumination light without uneven light distribution by repeating reflection on the side surface portion 21. In this case, the single fiber 2 is used as the tubular reflector.
Although 0 was used, the same effect can be obtained by using a glass rod or a glass rod whose periphery is plated with metal. The same effect can be obtained by the technique disclosed in Japanese Examined Patent Publication No. 3-73844. However, in the technique disclosed in the Japanese Patent Publication No. 3-73844, the end face of the single fiber is polished when the end face of the single fiber is directly polished and processed. However, there is a problem in processing such that the clad is easily peeled off.

On the other hand, in this embodiment, the single fiber 20 is used.
Since it is not necessary to directly grind it, and only the separate optical element 7 is bonded, workability is good and the same effects as those described in the publication can be obtained.

Further, in consideration of the constraint of the outer diameter of the distal end insertion portion of the endoscope, the optical element 7 has one surface which is not parallel to the incident surface and two surfaces.
Even in the case of a surface, a surface 4 or the like, the light flux can be averaged by joining with the single fiber 20, and the same effect can be obtained.

Further, for the purpose of reducing the diameter of the endoscope, the light guide and the optical element in the present invention are often formed in a deformed shape such as a rectangle, and accordingly, as shown in FIG. The single fiber 22 arranged on the front side is
Cylindrical body 23 having a cross-section 8 and joining two tubular bodies
By arranging it inside, it is possible to effectively use the internal space at the tip of the endoscope and prevent the loss of light quantity.

16 to 18 are explanatory views of a fifth embodiment of the endoscope illumination optical system according to the present invention. FIG.
Shows the endoscope body and the conversion adapter. In FIG. 16, reference numeral 24 denotes a distal end portion of an elongated insertion portion of the endoscope main body, to which a conversion adapter 25 can be attached.

FIG. 17 shows an enlarged view of the portion surrounded by the alternate long and short dash line in FIG. In FIG. 17, the conversion adapter 25 is configured to be screwed in the direction of the arrow with respect to the distal end portion 24 of the endoscope main body so that the optical axis centers of the illumination system and the objective system are aligned and used.

FIG. 18 is a sectional view showing the case where the conversion adapter is connected to the endoscope main body used in the radiation region. In FIG. 18, reference numeral 26 denotes an endoscope main body, in which an endoscope objective optical system 27 and an endoscope illumination optical system 28 are respectively installed.

On the other hand, 29 is a conversion adapter connectable to the endoscope main body 26, and inside thereof, an adapter objective optical system 30 and an adapter illumination optical system 31 are respectively installed. The viewing angle of the optical system in which the adapter objective optical system 30 and the endoscope objective optical system 27 are combined is 100 ° in this case. The adapter illumination optical system 31 includes an optical element 32 and a single fiber 33.

The endoscope illumination system 28 includes a quartz light guide 34 with NA = 0.35, and an optical element 35 in front of the object side surface. The optical element 35 in this case is the same as the optical element used in the first embodiment, and has the refractive index of 1.78472 and α of 22 °.

According to this structure, the NA of the light emitted from the endoscope main body can be converted to obtain a good light distribution, and the optical element 35 is changed even when a light guide having a different NA is used. As a result, the NA of the light emitted from the endoscope body can be converted, and various conversion adapters can be used, which is convenient in terms of cost. The optical element 35 is capable of converting NA,
For example, a polishing lens may be used.

19 (a) and 19 (b) are explanatory views relating to the sixth embodiment of the endoscope illumination optical system according to the present invention.
19A is a diagram showing a positional relationship between the optical element 36 and the light guide 4, and FIG. 19B is a diagram showing FIG.
It is an enlarged view of the part enclosed with the dashed-dotted line (a). FIG.
In (a) and (b), the optical element 36 is an optical element formed by integrally joining two optical elements 36a and 36b, and is disposed on the object-side front surface of the light guide 4. Then, the side surface portions 36c and 36d of the optical element 36
Is coated with an aluminum metal vapor deposition film.

With this structure, the light guide 4
The light flux emitted from is reflected by 36c and 36d, and returns to the inside of the optical element 36 again. Therefore, since the light amount can be effectively used without leaking, the emitted light amount can be increased.

Further, there is an advantage that even a shape that is difficult to process with one part can be manufactured at a relatively low cost by joining two parts that can be easily processed. The present embodiment can be applied and utilized in any of the first to fourth embodiments described above, and similar effects can be obtained. Also,
The same effect can be obtained by applying a metal coating other than aluminum to the side surface portions 36c and 36d, or mirror-finishing when the optical element 36 is optical glass.

As described above, the endoscope illumination optical system according to the present invention has the following features in addition to the features described in the claims. (1) The endoscope illumination optical system according to claim 2, wherein a cross section perpendicular to the optical axis direction of the optical element and a cross section perpendicular to the optical axis direction of the tubular reflector have different shapes from each other. .

(2) The endoscope illumination according to any one of claims 1 to 3, wherein the entrance end surface of the optical element is one surface inclined with respect to the exit end surface of the light guide. Optical system.

(3) The incident end surface of the optical element is composed of two inclined surfaces having different inclination directions with respect to the emission end surface of the light guide. Endoscope illumination optical system.

(4) The entrance end surface of the optical element is formed of four inclined surfaces having different inclination directions with respect to the exit end surface of the light guide. Endoscope illumination optical system.

(5) The optical element is constructed by combining a plurality of transparent optical members each having an inclined surface such that the directions of the inclined surfaces are different from each other. The endoscope illumination optical system according to any one of claims.

(6) The optical element is characterized in that the shape of its cross section perpendicular to the optical axis direction is not substantially circular.
4. The endoscope illumination optical system according to any one of 1 to 3.

(7) The endoscope according to any one of claims 1 to 3, wherein the optical element has a substantially rectangular cross section perpendicular to the optical axis direction or a substantially quadrangle including an arc. Illumination optics.

(8) The endoscope according to any one of (1) to (7) or (1) to (7) above, wherein an adapter is detachably provided at a tip of an insertion portion of the endoscope. Endoscope illumination optical system.

(9) The optical element is mirror-polished at the periphery, or a metal vapor deposition film is provided at the periphery, or (1) above.
The endoscope illumination optical system according to any one of (8) to (8).

(10) An illumination optical system including a light guide for transmitting light from a light source, and an illumination lens group arranged in front of the end face of the light guide on the object side, an objective optical system and an image transmitting means in order from the object plane side. In an endoscope apparatus including an endoscope main body having an elongated insertion portion including a and an adapter detachably attached to a distal end of the insertion portion, illumination is provided between the illumination lens group and an emission end surface of a light guide. An endoscope illumination optical system, wherein at least one optical element for converting the numerical aperture of light is arranged.

(11) The endoscope illumination optical system described in (10) above, wherein the optical element for converting the numerical aperture is arranged in the endoscope body.

[0070]

Since the present invention is configured as described above, it has the following effects. (1) The NA of the light guide can be easily used by using the law of refraction.
Is converted, it is possible to obtain illumination with good light distribution even with a light guide having a small NA.

(2) The light flux emitted from the vicinity of the peripheral portion of the object-side end face of the light guide is made incident on the optical element without leaking, so that all the light amount transmitted from the light guide can be used without waste. You can

(3) It is possible to improve the workability by eliminating the work of directly polishing and processing the single fiber, and the light beam in which a low NA light beam is largely converted by passing through the optical element is a single fiber. By repeating the reflection on the side surface when passing through, it is possible to obtain good illumination light without uneven light distribution.

[Brief description of drawings]

FIG. 1 is a transverse cross-sectional view showing an object-side tip portion of an endoscope illumination optical system according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an object-side tip portion of the endoscope illumination optical system according to the first embodiment of the present invention as viewed in the direction of the arrow in FIG.

FIG. 3A is a perspective view of an optical element. (B)
FIG. 4 is a schematic configuration diagram illustrating an enlarged positional relationship between an optical element and a light guide.

FIG. 4 is an explanatory diagram showing a principle that a light beam emitted from a light guide undergoes NA conversion through an optical element in the endoscope illumination optical system according to the first embodiment of the present invention.

FIG. 5A is a perspective view showing an optical element in the endoscope illumination optical system according to the first embodiment of the present invention. (B)
FIG. 3 is a schematic configuration diagram illustrating an enlarged positional relationship between an optical element and a light guide in the endoscope illumination optical system according to the first embodiment of the present invention. FIG. 3C is a schematic configuration diagram showing a state in which an optical element is arranged at the tip of the endoscope illumination optical system according to the first embodiment of the present invention. (D) In the endoscope illumination optical system according to the first embodiment of the present invention, an optical element and a light guide in which a projected area of a surface facing the light guide is larger than an area of an end surface on the object side of the light guide. It is a perspective view which shows the positional relationship of. (E) is an explanatory view showing a principle in which the light beam emitted from the peripheral portion of the light guide has the NA converted through the optical element in the endoscope illumination optical system of the first embodiment of the present invention. is there.

FIG. 6 is a schematic configuration diagram of an object-side tip portion of an endoscope illumination optical system according to a second embodiment of the present invention when viewed from the front.

FIG. 7 is a perspective view of an optical element in the endoscope illumination optical system according to the second embodiment of the present invention.

FIG. 8 is a schematic configuration diagram showing a positional relationship between an optical element and a light guide in the endoscope illumination optical system according to the second embodiment of the present invention.

FIG. 9 is a state diagram showing an observation visual field of a TV monitor in the endoscope illumination optical system according to the second embodiment of the present invention.

FIG. 10 is a diagram showing a state in which the interior of the pipe is projected on a TV monitor by the objective optical system without being illuminated by the endoscope illumination optical system according to the second embodiment of the present invention.

FIG. 11 is a diagram showing a state in which the inside of the pipe illuminated by the endoscope illumination optical system according to the second embodiment of the present invention is displayed on the TV monitor by the objective optical system.

FIG. 12A is an exploded perspective view of an optical element in the endoscope illumination optical system according to the third embodiment of the present invention. (B)
FIG. 9 is an enlarged view showing a positional relationship between an optical element formed by joining two optical elements and a light guide in the endoscope illumination optical system according to the third embodiment of the present invention.

FIG. 13 is a comparative explanatory diagram when an optical element is used in the endoscope illumination optical system according to the third embodiment of the present invention.

FIG. 14 is a schematic configuration diagram showing a mutual positional relationship among a single fiber, an optical element, and a light guide as an endoscope illumination optical system according to a fourth example of the present invention.

FIG. 15 is a schematic configuration diagram in the case where a single fiber and an 8-shaped tubular body are used in the endoscope illumination optical system of the fourth example of the present invention.

FIG. 16 is an explanatory diagram of the configuration and usage of the conversion adapter and the endoscope main body in the endoscope illumination optical system according to the fifth embodiment of the present invention.

FIG. 17 is an enlarged view of a portion surrounded by an alternate long and short dash line in FIG. 16 in the endoscope illumination optical system according to the fifth embodiment of the present invention.

FIG. 18 is a lateral cross-sectional configuration diagram of a conversion adapter and an endoscope main body in the endoscope illumination optical system according to the fifth embodiment of the present invention.

FIG. 19A is a schematic configuration diagram showing a positional relationship between an optical element and a light guide in the endoscope illumination optical system according to the sixth embodiment of the present invention. (B) is an explanatory view of the principle that the light flux emitted from the light guide is reflected on the inner side surface of the optical element in the endoscope illumination optical system of the sixth embodiment of the present invention.

[Explanation of symbols]

1,13 End of endoscope 2,14 Objective optical system 3 Illumination optical system 4,34 Quartz light guide 5 Object side end face 6 Vertex 7,35 Optical element 8,9 Slope 10 Bottom surface 11,12 Mountain optical element 15 quadrangular pyramid optical element 16 TV monitor observation field of view 17 TV deep inside pipe
Monitor image 18 Recessed optical element 18a Left recessed optical element 18b Right recessed optical element 18c, 18d Edge 19 Frame 20, 22, 33 Single fiber 21 Cylindrical reflector 23 8-shaped reflector 24 End of endoscope body Part 25 Conversion adapter 26 Endoscope body frame 27 Endoscope-side objective optical system 28 Endoscope-side illumination optical system 29 Adapter frame 30 Adapter-side objective optical system 31 Adapter-side illumination optical system 32 Objective lens 36 Optical with metal deposition film Element 36a Left side metal vapor deposition film-coated optical element 36b Right side metal vapor deposition film-coated optical element 36c, 36d Metal vapor deposition film side surface α Slopes 8 and 9 are bottom surfaces 10
Angle θ initial distribution angle θ'converted distribution angle

Claims (3)

[Claims] 1. An illumination optical system comprising a light guide for transmitting light from a light source, an illumination lens group arranged in front of the object side end face of the light guide, an objective optical system in order from the object plane side, and image transmission. In the endoscope having an elongated insertion portion including: an illumination element group, the illumination lens group includes an optical element in which an incident end surface facing the light guide includes an inclined surface inclined with respect to an exit end surface of the light guide. An endoscopic illumination optical system comprising at least one. 2. The endoscope according to claim 1, wherein a cross section perpendicular to the optical axis of the illumination lens group and a cross section perpendicular to the optical axis of the light guide have different shapes. Illumination optics. 3. The at least one tubular reflector is arranged on the object side of the illumination lens group.
The endoscopic illumination optical system described in.