JPH04242213A - Side view type endoscope for in-tube observation - Google Patents

Abstract

PURPOSE:To remove halation and to improve light distribution and lighting efficiency. CONSTITUTION:An in-tube surface 17 is observed through the side view type endoscope by fitting a centering device to the endoscope or nearly equalizing the outer circumference to the internal diameter of the in-tube surface 17 as to the outward shape of the endoscope itself. The incidence window of an object optical system and the exit window 19 of a lighting optical system are provided to the tip part of the endoscope, and the objective optical system and lighting optical system are so arranged that the luminous flux area for forming an image 18a of the in-tube surface 17 by the light through the entrance pupil 18 of the objective optical system does not overlap with the exit window 19 of the lighting optical system. Consequently, the reflected right L of light irradiating the observation range 17a on the in-tube surface 17 from the exit window 19 of the lighting optical system is not made incident on the entrance pupil 18 and no halation is generated. Further, the exit window 19 is positioned by or nearby the incidence window.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a side-viewing endoscope for observing a substantially circular inner surface of a tube, that is, a wall surface of a tube from the side.

0002

2. Description of the Related Art In recent years, endoscopes have been widely used as a non-destructive inspection means for inspecting damage on the inner surface of gas pipes, water pipes, etc. and the welding condition of pipe connections. Forward-looking endoscopes are useful, but because they obliquely observe the inner surface of the tube, the size of scratches and welds changes depending on their position on the monitor screen, making it easier to avoid scratches and welds. It is not suitable for quantitatively measuring the width of a welded part, etc. Additionally, if a conical mirror is attached to the front of the tip of a forward-looking endoscope, it is possible to view almost the entire circumference of the tube's inner surface from the front at once, but the image distortion is large and this is also difficult for accurate measurements. Not suitable. On the other hand, although side-viewing endoscopes cannot observe the entire circumference of the inner surface of the tube at once, they are extremely useful for such applications because they can view the inner surface of the tube straight on and the image is less distorted. be.

By the way, in order to obtain an image with little distortion over the entire circumference of the inner surface of the tube using a side-viewing endoscope, the following means, for example, are required. First, in order to observe the entire circumference of the inner surface of the tube, it is necessary that the observation optical system consisting of an objective and an illumination optical system at the tip of the endoscope is rotatable with respect to the tube. If the distal end of the endoscope is connected to the rear end on the proximal side, the structure is generally such that the distal end can be rotated for observation by twisting and rotating the proximal end. be. However, in order to accurately control the rotation of the tip, a rotation device as shown in FIG. 25 is required. That is, a motor 3 is built into the distal end 2 of the endoscope 1, and the distal end is fixed to the inner surface of the tube by an appropriate method. The main body 5, in which a mirror 4 and an observation optical system (not shown) are integrated, is rotated. A rotation control signal and electric power are supplied to the motor 3 through the main body 5. Further, the main body 5 side is made to be easily twisted so that it can be easily rotated, and by rotating it by a certain angle in both directions, the entire circumference of the inner surface of the tube can be observed.

Furthermore, when measuring the inner surface of a tube, it is necessary to ensure that the distance between the endoscope and the observation surface of the inner surface of the tube does not change significantly regardless of the rotational position. For this purpose, an endoscope 1 having an outer diameter close to the inner diameter of the tube 6 to be observed is used as shown in FIG. 26, or an endoscope 1 as shown in FIG.
As shown in FIG. 28, a substantially ring-shaped member made of rubber or the like and having an outer diameter close to the inner diameter of the tube 6, called a centering device 7, may be attached to the outer periphery of the endoscope 1. There are two types of centering device 7: one whose outer diameter can be expanded and contracted according to the inner diameter of the pipe, and another which allows devices 7 of different diameters to be exchanged.

Next, a conventional side-viewing endoscope will be explained. Figure 29 shown in Utility Model Application Publication No. 53-101482
This endoscope is a typical example of a side-viewing endoscope. In the figure,
An entrance window of an objective optical system 10 having an objective lens 9 including an image guide 8 and a side viewing prism 9a, a light guide 11 whose tip portion is bent toward the inner surface of the tube, and an illumination lens 1.
2 and exit windows of the illumination optical system 13 are arranged in the longitudinal direction of the endoscope 1. This endoscope can be used when there is a certain distance from the inner surface of the tube, but in the case of a narrow pipe with a small inner diameter, the observation distance becomes short, so the objective optical system 10 and the illumination optical system 13 The effect of parallax due to the positional shift of each window becomes noticeable. As a result, one side of the image becomes dark, making it impractical for practical purposes such as measurement. In addition, when the object to be observed is a metal pipe, etc., and the inner surface of the tube is relatively mirror-like, the illumination light is reflected from the inner surface of the tube (hereinafter referred to as specular reflection) and falls within the observation light flux area (field of view) of the objective optical system. There is also the problem that very strong halation occurs in this area, which interferes with observation and measurement.

[0006] Also, FIG.
In the endoscope shown in FIG. 31, reflective mirrors 14 are respectively arranged to reflect the light beams of the objective optical system and the illumination optical system by a common mirror. Further, in FIG. 30, a plurality of exit end surfaces of the light guide 11 are arranged in a substantially crescent shape around the objective lens 9 provided at the center of the endoscope (see FIG. 30(B)). In FIG. 31, the exit end surface of the light guide 11 is similarly arranged in an annular manner around the objective lens 9. Therefore, even if the inner diameter of the tube is relatively small, compared to the conventional device described above, the distance between the inner surface of the tube and the objective optical system and the illumination optical system is increased by the amount of reflection by the reflection mirror 14, so the influence of parallax is reduced. Decrease. However, when observing the inner surface of a tube close to the endoscope, parallax due to the difference in the installation positions of the objective optical system and the illumination optical system is difficult to ignore, and uneven illumination remains on the inner surface of the tube. There is. On the other hand, if the light distribution is widened in order to eliminate uneven illumination, the efficiency of the illumination will drop, making it impossible to satisfy the requirements for wide light distribution and illumination efficiency at the same time. Furthermore, when the inner surface of the tube of the object to be observed is close to a mirror surface, there is a drawback that the reflected light enters the observation light flux area of the objective optical system, causing intense halation, similar to the above-mentioned conventional technology. .

[0007] On the other hand, Japanese Patent Application Laid-open No. 61 (1983) shown in FIG.
The endoscope described in Publication No. 39019 has a light guide 11
Half of the luminous flux emitted from the exit end face of the side viewing prism 9
a, and the remaining half is reflected by the mirror 15a located in front of the side viewing prism 9a.
The light is reflected at point b and focused on the observation range on the inner surface of the tube. Moreover, this device has two mirrors 15a,
Both mirrors 15a and 15b are arranged at a considerable distance from the exit window of the objective optical system in the longitudinal direction so that the image of the mirror 15b does not enter the field of view of the objective optical system. This makes it possible to prevent halation due to specular reflection on the inner surface of the tube and to ensure light distribution.

[0008]

However, in such a configuration, the distance between the mirrors 15a and 15b in the front and back direction is quite large, and both mirrors are arranged at a large angle. The disadvantage is that the tip is very long. Furthermore, since uneven light distribution rapidly occurs when the observation distance changes, it can only be used for tubes with a certain predetermined inner diameter. Furthermore, the inner surface of the tube must be illuminated obliquely, and with this configuration, due to the characteristics of the endoscope, there is not enough space to place a mirror large enough for illumination, which reduces the efficiency of illumination. It has the disadvantage of being bad and dark. In addition, if the inner diameter of the tube is close to the outer diameter of the endoscope, it is necessary to increase the tilt angle of the mirror and further distance it from the exit window of the objective optical system, which also reduces the efficiency of light distribution and illumination. The problem is that it is bad.

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide a side-viewing endoscope for observing inside a tube, which eliminates halation and has good light distribution and illumination efficiency.

0010

[Means for Solving the Problems] A side-viewing endoscope for observing inside a tube according to the present invention uses a tube having a substantially circular cross section as an object to be observed, and uses a centering device attached to the endoscope or a centering device attached to the endoscope itself. In a side-viewing endoscope for observing inside a tube, the outer circumference is made equal to the inner diameter of the tube, and the endoscope is used to observe the inner surface of the tube. The objective optical system and the illumination optical system are arranged so that the light flux area of the image formed by the inner surface of the tube of the entrance pupil of the objective optical system does not overlap with the exit window of the illumination optical system. It is characterized by the fact that

Further, the entrance pupil of the objective optical system is located near the central axis of the tube.

0012

[Operation] During observation, the illumination light emitted from the exit window of the illumination optical system illuminates the observation range on the inner surface of the tube, but the reflected light does not enter the entrance pupil of the objective optical system, so no halation occurs. .

[0013]

EXAMPLES The present invention will be explained in detail below based on examples. 1 and 2 are diagrams showing the principle of the present invention when the entrance pupil of the objective optical system is located approximately on the central axis of the inner diameter of the tube. In FIG. 1, 17 is the approximately circular inner surface of the tube to be observed, and 18 is the entrance pupil of the objective optical system of the endoscope located approximately on the central axis O of the tube inner surface 17 (for ease of explanation, (represented as a point in FIG. 1), an objective lens and the like are arranged so that the entrance pupil 18 is located near the central axis of the outer periphery of the endoscope (not shown). Further, the position of the entrance pupil 18 with respect to the tube inner surface 17 is adjusted by fitting a centering device to the endoscope depending on the size of the tube inner diameter. 19, 19 are exit windows of a pair of illumination optical systems arranged on a plane A that is perpendicular to a line segment connecting the center point of the observation range 17a on the tube inner surface 17 and the entrance pupil 18 and that includes the central axis O; these windows 19
, 19 are arranged symmetrically with respect to the central axis O.

Here, the arrangement position of the exit window 19 will be explained based on FIG. 2. FIG. 2(A) is a cross-sectional view in a direction perpendicular to the longitudinal direction of the tube (hereinafter referred to as orthogonal cross section),
(B) is a sectional view in the longitudinal direction of the tube (hereinafter referred to as longitudinal section). In Figure (A), when the entrance pupil 18 is an object, the light flux La heading from there toward the tube inner surface 17 is reflected at the observation range 17a (width Do), converged again on the entrance pupil 18, and forms an image. In addition, in Figure (B), the light beam La emitted from the entrance pupil 18 is reflected at the observation range 17a, passes through the central axis O with a spread 2Do that is approximately twice the width Do of the observation range 17a, and forms an image. . These reflected light fluxes L form an image 18a of the tube inner surface 17 of the entrance pupil 18, but if the exit window of the illumination optical system is arranged at a position that does not overlap with this linearly spread reflected light flux L, the illumination Light is inside the tube 1
Even if it is reflected by 7, it will not enter the entrance pupil 18. Therefore, in FIG. 1, the exit windows 19, 19 are located at such positions.
If this is provided, halation will not occur even if the inner surface of the tube is close to a mirror surface.

Note that the exit windows 19, 19 are the entrance pupil 1 in FIG.
8, but it may be placed offset in the longitudinal direction of the endoscope. Further, the number of exit windows 19 may be selected as appropriate.

As described above, according to the first principle of the present invention, when observing the tube inner surface 17, the illumination irradiates the observation range 17a of the tube inner surface 17 from the exit windows 19, 19 of the illumination optical system of the endoscope. The reflected light does not enter the entrance pupil 18 of the objective optical system, and no halation occurs. Moreover, there is no need to arrange the exit windows of the illumination optical system at long intervals before and after the longitudinal direction of the entrance pupil, as in the prior art described above.
The tip of the endoscope can be made compact. Furthermore, since the illumination light illuminates the observation range 17a from substantially lateral to the entrance pupil 18, both light distribution and illumination efficiency are good.

A first embodiment based on the first principle of the present invention will be described below with reference to FIG. In the figure, 21 is the tube inner surface 17
22 is an objective lens located in front of the solid-state image sensor 21, and 23 is an aperture diaphragm provided between the objective lenses 22. It is arranged so as to be located on the central axis O of the tube inner surface 17 (see Figures (A) and (B)), and constitutes an objective optical system. 24, 24 are a pair of light guides whose tips are bent toward the inner surface 17 of the tube; 25, 25 are the tips of the light guides 24, 24 symmetrically with respect to the central axis O and in front of the entrance pupil 18 in the longitudinal direction; A pair of illumination lenses are arranged on the sides (see Figure C), and their exit surfaces are formed to be inclined so that the illumination light overlaps the field of view toward the observation range 17a. Moreover, each illumination lens 25, 25
The exit surface of is located outside the area of the reflected light beam L of the entrance pupil 18. In this embodiment, the illumination lens 25 is connected to the entrance pupil 18.
, 25 are shifted in the longitudinal direction, so
The endoscope can be made relatively small in diameter. It goes without saying that the solid-state image sensor 21 may be replaced with an image guide that is bent at its tip.

FIG. 4 shows a modification of the first embodiment, in which only one illumination optical system is used and a light emitting diode 26 or a semiconductor laser is arranged in place of the light guide. (See Figures (A) and (B)). Also, lighting lens 2
5 is arranged diagonally in front of the entrance pupil 18.

FIG. 5 shows a second embodiment, in which a side viewing prism 28 is disposed close to the entrance window as an objective optical system, and an aperture stop 29 is provided on the entrance surface of the side viewing prism 28. An objective lens 22 and a solid-state image sensor 21 are arranged behind the prism 28. Therefore, the entrance pupil 18 on the central axis of the tube inner surface 17 is located at the same position as the aperture stop 29. a light guide 24 that constitutes an exit window of the illumination optical system;
The exit end surfaces 24a, 24a of No. 24 are arranged obliquely upward behind the entrance window of the objective optical system (Figure (B)).
, (C)). In this embodiment, the light guides 24, 2
The exit end surfaces 24a, 24a of No. 4 are arranged slightly above the plane A including the central axis O of the tube and outside the area of the reflected light beam L. According to this configuration, effective illumination with less unevenness in light distribution can be achieved for the observation range 17a of the tube inner surface 17.

FIG. 6 shows a third embodiment, in which a light guide 31 constituting an illumination optical system is bifurcated at the tip and bent toward the inner surface 17 of the tube (see FIG. (A)).
The exit end surfaces 31a, 31a constituting the exit window extend linearly on both sides in the longitudinal direction of the entrance window of the objective optical system (Fig.
See B). Furthermore, the emission end surfaces 31a, 31a are arranged to be inclined inward so that the illumination light emitted from the emission end surfaces 31a, 31a efficiently illuminates the observation range 17a (see figure (C)). In addition, the injection end surfaces 31a, 31a
As long as the shape is outside the area of the reflected light beam L, the shape is not limited to a straight line, and any suitable shape such as an arc or a ring can be selected. In the case of this embodiment, since the exit end faces 31a, 31a are thin, the distal end of the endoscope can be made small in diameter and short even if it is placed right next to the entrance window.

FIG. 7 shows a fourth embodiment, and in the figure, reference numerals 33 and 33 are located in front of the tips of a pair of light guides 34 and 34, respectively, on both sides of the side viewing prism 28 of the objective optical system. It is a single fiber for illumination with a circular cross section and a cladding formed around the core. The input side end surface 33a of this single fiber 33 is cut obliquely to form a transflective surface or a Fresnel surface, which reflects a part of the illumination light incident from the light guide 34 to the observation range 17a of the tube inner surface 17. , allowing the remaining light to pass through. Furthermore, the exit side end surface 33b is also cut diagonally in the same direction to form a total reflection surface (it may be coated with a metal film) to reflect the illumination light toward the observation range 17a. good. In addition, as shown in FIG. 8, a bonding surface 3 in which a semi-transparent film is disposed obliquely in the middle part of the single fiber 33 is formed.
3c may be formed to reflect part of the illumination light. In any case, since each single fiber 33 can be irradiated with illumination light from at least two directions, the observation range 1
This is effective in eliminating shadows within 7a. Further, as for the structure of the single fiber, in addition to the structure of the embodiment, an appropriate structure such as a rectangular prism glass rod surrounded by a low refractive index layer can be adopted.

FIGS. 9 and 10 show modifications of the objective optical system of each of the above-described embodiments. In FIG. 9, an aperture stop 29 and an objective lens 22 located at the entrance window of the objective optical system are shown.
The side viewing prism 36 located between the two prisms 3
6a and 36b are formed with a bonding layer 37 having a smaller refractive index than these prisms sandwiched therebetween. The light flux from the object passes through the aperture diaphragm 29 and enters the prism 36, and is reflected by the reflecting surface 36c.
After being reflected and bent upward, it is totally reflected by the bonding layer 37 and enters the objective lens 22 . This configuration has the advantage that the objective lens 22 can be easily brought to the center of the endoscope.

FIG. 10 shows the objective optical system with side viewing prism 2.
8 and a diamond-shaped prism 38 are combined. According to this configuration, since the objective optical system is arranged relatively above, the illumination optical system of the part other than the exit window and the objective optical system can be arranged so as to overlap in the vertical direction, and the endoscope Effective for downsizing.

FIG. 11 shows a fifth embodiment, in which the objective optical system is arranged on the distal end side, which is the opposite side from the illumination optical system. That is, in the illumination optical system, a pair of light guides 34, 34 and triangular right angle prisms 40, 40 for bending the illumination light upward and deflecting it toward the observation range 17a are arranged in sequence from the proximal side of the endoscope. ing. On the other hand, in the objective optical system, a solid-state image sensor 21, an objective lens 22, and a side-viewing prism 28 located between a pair of triangular right-angle prisms 40, 40 are sequentially arranged from the distal end of the endoscope. In the case of this embodiment, since the objective optical system and the illumination optical system do not overlap, a small diameter endoscope can be realized. Moreover, the endoscope tip can be made relatively short in length.

FIG. 12 shows a sixth embodiment, in which a solid-state image sensor 21, an image relay lens system 42, and a light guide (not shown) arranged in the same manner as in FIG.
An objective optical system consisting of an aperture diaphragm 43 and an imaging lens 44 sandwiched between this relay lens system 42 is arranged. Moreover, the image of the aperture stop 43, that is, the entrance pupil 18, is formed on the reflection mirror 45. Here, this reflecting mirror 45 constitutes a common mirror that reflects the light beam of the objective optical system and the illumination light beam of the illumination optical system, and moreover, the pair of illumination light beams and the entrance pupil formed by the tube inner surface 17 are formed on the mirror 45. Each optical system is arranged so that the 18 images are parallel and do not overlap. Note that 46 is an intermediate image of the observation range 17a formed by the imaging lens 44. In addition, if the objective optical system and illumination optical system can be completely separated, such as by using separate reflection mirrors, and there is no influence of flare, etc., the reflection mirror should be set to the minimum size necessary to cover the field of view. Alternatively, the relay lens system 42 and the aperture diaphragm 43 may be omitted, and the reflecting mirror may have the function of an entrance pupil.

FIG. 13 shows a seventh embodiment,
A light guide 34, a triangular right angle prism 40, and an illumination lens 48 are arranged in the center of the endoscope 1 to constitute an illumination optical system. The illumination lens 48 is formed with an inclined exit surface so as to deflect the illumination light toward the observation range 17a of the tube inner surface 17 located above the rear (front side) of the illumination lens 48. or,
Behind the illumination lens 48 and on both sides of the light guide 34,
A pair of objective optical systems consisting of a solid-state image sensor 21 and an objective lens 49 are arranged. In order to deflect the light beams from each of the objective lenses 49, 49 so as to proceed along the optical axis, the incident surfaces are formed to be inclined in opposite directions. The reflected light flux L reflected on the tube inner surface 17 due to this deflection is
Each of them extends in the longitudinal direction at the position of the other objective lens 49, and does not overlap with the exit window of the illumination optical system.

In the case of this embodiment, the observation range 17a can be observed from different viewing directions using the two objective optical systems, and stereoscopic viewing of the observed image becomes possible. Next, regarding the stereoscopic viewing method, images observed by two objective optical systems are displayed alternately on a monitor, while the viewer uses a shutter that opens and closes in synchronization with the switching of the monitor images. All you have to do is wear glasses and observe. By combining so-called three-dimensional display devices in this way, three-dimensional observation becomes possible. Furthermore, three-dimensional measurement data can be obtained by this objective optical system. Note that a light emitting diode, semiconductor laser, etc. may be used in place of the light guide 34 of the illumination optical system, and that the exit window of the illumination optical system may be arranged in a position relative to the entrance window of the objective optical system. Similarly to the above-mentioned embodiments, it can be disposed on the front side in the longitudinal direction or just to the side.

Furthermore, in each of the embodiments described above, when the centering device is attached to the endoscope, it is not necessarily necessary that the central axes of both devices coincide. It is only necessary that the entrance pupil of the objective optical system coincides with the central axis of the tube when the centering device is attached to the endoscope.

In each of the embodiments described above, the entrance pupil of the objective optical system is located on the central axis O of the inner surface of the tube, facing the observation range, but in the present invention, the entrance pupil is not located on the central axis O. However, in the orthogonal cross section of the tube, approximately ±R/2 (R: radius of the inner surface of the tube) on a line perpendicular to the plane A shown in Figure 1 from the central axis O.
If the entrance pupil is within the range of , the same effect as in the above case can be obtained. The second principle of the present invention is
This will be explained based on FIGS. 14 to 16. In FIG. 14, the entrance pupil 18 of the objective optical system is located at a distance x downward from the central axis O of the tube inner surface 17 (in FIG. 14, the downward direction is + and the upward direction is -), Further, assuming that the length of the observation range 17a of the tube inner surface 17 is Do, consider image formation by specular reflection of the entrance pupil 18. A light beam La emitted from the center of the entrance pupil 18 in the direction of the observation range 17a is reflected on the inner surface of the tube, which is close to a mirror surface.The spread of the reflected light beam L at the pupil position 18 is defined as Di. The respective extensions Di appearing in the orthogonal cross section and the longitudinal cross section of the tube are shown in Figures (A) and (B). Therefore, the exit window of the illumination optical system needs to be placed outside the area of the light flux La and the reflected light flux L. Here, the extent Di in the orthogonal cross-sectional direction (denoted as the S direction) and the extent Di in the longitudinal cross-sectional direction (denoted as the T direction) with respect to the distance x are shown by line segments S and T shown in FIG. In addition, observation range 1
The length Do of 7a is constant regardless of the distance x of the entrance pupil 18.

Therefore, in FIG. 15, the reflected light flux L is
In the S direction, when the entrance pupil 18 is on the central axis O of the tube, that is, when x=0, Di=0, and when x=R/2, Di=Do. Furthermore, in the T direction, since it is a plane reflection, Di=2Do is always true regardless of the value of x. Therefore, when the distance x=±R, the spread Di
is equal in the S direction and the T direction (Di=2Do),
When the distance x is 0, it becomes a straight line. Note that the relationship among Di, Do, x, and R is expressed by the following equation. Di/Do=2|x|/R

Next, a case will be explained in which the entrance pupil 18 is located at a distance x (≧-R/2) upward from the central axis O, that is, in the direction of the observation range 17a. FIG. 16 shows the case where the entrance pupil 18 is located at the position of x=-R/2, and in the orthogonal cross section of the tube inner surface 17 shown in FIG. It becomes a parallel beam of light with the same width as . (In the longitudinal cross-section shown in Figure (B), the spread Di of the reflected light beam L at the pupil position x is 2Do.) Therefore, the width Do of the observation range 17a in the orthogonal cross-section (A) is If it is about 1/3 of the circumference, the ratio of the width of the reflected light beam L to the tube diameter becomes large, so the space for arranging the exit window of the illumination optical system in the endoscope is at its limit. or,
If the length Do is within about 1/10 of the circumference, the spread of the reflected light beam L will be small and the space for the exit window of the illumination optical system will be reduced.
There is plenty of space.

As described above, according to the second principle of the present invention, even if the entrance pupil 18 is not located on the central axis O of the inner surface 17 of the tube, it is within a distance of ±R/2 from the central axis O. If so, it is possible to obtain a side-viewing endoscope that eliminates halation and has good light distribution and illumination efficiency. However, if the width of the observation range 17a of the tube inner surface 17 in the orthogonal cross-sectional direction becomes 1/3 or more of the tube inner circumference, the exit window of the illumination optical system can eliminate halation when the entrance pupil 18 is at the -R/2 position. placement becomes difficult. In such a case, if the entrance pupil 18 is brought closer to the central axis O from the position -R/2, the reflected light beam L will be converged, so the arrangement space of the exit window can be adjusted to eliminate halation. This will become possible as the space expands.

FIG. 17 shows an eighth embodiment based on the second principle of the present invention. In the figure, the entrance pupil 18 is x=+
It is located at a position R/2, and each light beam from the objective optical system and the illumination optical system is bent by the same reflecting mirror 45. Further, the illumination optical system is located on the central axis O of the tube inner surface 17, and the objective optical system is arranged below it. Therefore, the pair of illumination optical systems are arranged on both sides of the objective optical system so that their exit windows are located outside the area e of the light flux La and the reflected light flux L (see Figure (A)). The illumination lens 51 has an inclined exit surface so that the illumination light is directed toward the observation range 17a. In such a configuration, if the width Do of the observation range 17a in the orthogonal cross-sectional direction is within about 1/4 of the circumference, it is possible to arrange the exit window of the illumination optical system to avoid the light flux La and the reflected light flux L. . In particular, if the width Do is within a range of about 1/6 to 1/10 of the tube circumference, it is easy to arrange the exit window without halation.

FIG. 18 shows a ninth embodiment. In the figure, the entrance pupil 18 is located at x=-R/2, and the width Do of the observation range 17a in the orthogonal cross-sectional direction is approximately 1/6 of the tube circumference.
(See figure (A)). Since the reflected light flux L is parallel, the pair of illumination lenses 52, 52 forming the exit window of the illumination optical system are arranged outside the area of the reflected light flux L. Moreover, this illumination lens 52 is formed as a wedge prism, and deflects the illumination light from right beside the entrance pupil 18 toward the observation range 17a. For this reason, light distribution,
Both lighting efficiency is good. Note that the configurations of the objective optical system and the light guide 31 are almost the same as those shown in FIG.

Next, the third principle of the present invention in the case where the entrance pupil 18 is disposed at a position where the distance x≧R/2 will be explained based on FIG. 19. The entrance pupil 18 of the objective optical system is the tube inner surface 17
In other words, when x>0, the reflected luminous flux L converges above the central axis O and within the region of the luminous flux La, with respect to the region of the luminous flux La that goes from the entrance pupil 18 to the observation range 17a, This will form an image of the entrance pupil. That is, in FIG. 19, if the position of the image 18a of the entrance pupil 18 on the tube inner surface 17 is expressed by x' with the central axis O as the origin, the entrance pupil image 18a
The position x' is expressed by the following equation. x'=R/2・(-x)/(R/2+x) To further explain this equation, (1) When the entrance pupil 18 is on the central axis O, the pupil image 18a is They match, and the light flux La and the reflected light flux L overlap. (2) When the entrance pupil 18 is at infinity (x=∞), the above equation becomes x'=-R/2. Moreover, since the luminous flux La becomes a parallel luminous flux with a width Do, the reflected luminous flux L is included within this region.

Therefore, when x>R/2 (0<x≦R/
Regarding the area (2) described above, halation can also be eliminated by arranging the exit window of the illumination optical system outside the area of the light beam La. As for the means for arranging the entrance pupil 18 at the position where x>R/2, a reflecting mirror may be used as in the above embodiment, or an objective optical system may be directly arranged. In this case, since x is large, the former method is easier.

[0037] In addition, to explain the case where the entrance pupil 18 is at a position where x<-R/2, in this case, the observation range 17a
The entrance window of the objective optical system of endoscope 1 is located quite close to It becomes difficult to eliminate the incidence of Therefore,
In order to eliminate halation, the exit window of the illumination optical system must be placed considerably outside, which is undesirable because it causes the same drawbacks as the prior art described above.

FIG. 20 shows a tenth embodiment using the third principle of the present invention. In the figure, the entrance pupil 18 is the tube inner diameter R
It is located at the same distance as the outer diameter of the endoscope, which is approximately approximate to , and the light beam La is bent by the reflecting mirror 45. The illumination optical system uses a pair of cylindrical light emitters (such as fluorescent lamps) 54, which are arranged in the longitudinal direction of the tube and above the central axis O, away from the light beam La. In the case of this embodiment, since the exit window of the illumination optical system is located close to the observation range 17a of the tube inner surface 17, a bright image can be obtained.

FIG. 21 shows an eleventh embodiment. In the figure, the illumination optical system includes a pair of light guides 34, 34 for transmitting illumination light, a circular hole 55a in the center for passing the light beam La, and a half mirror surface 55b arranged inclined toward the incident side. and a total reflection surface 55c on which a metal plate such as aluminum is arranged obliquely on the emission side to cause total reflection. This flat glass 55 is
A light-shielding plate is arranged on the mask except for the circular hole 55a, so that flare caused by leaked light can be prevented. In this embodiment, the exit window of the illumination optical system partially overlaps the reflected light beam L in the longitudinal direction, causing halation.

FIG. 22 shows a twelfth embodiment. In this embodiment, the objective optical system is arranged so that the entrance pupil 18 is located at the position of x=R. In the illumination optical system, light diffusing materials 56, 56 such as acrylic or opal glass are arranged on the exit end surfaces of the light guides 34, 34 above the central axis O outside the area of the light beam La.

FIGS. 23 and 24 show modified examples of illumination means that can be applied to each of the above-described embodiments. FIG. 23 shows a modification of the illumination means of the eleventh embodiment, and in the figure, the luminous flux L
A (or reflected light flux L) is passed through a circular light 57a on a diffuser plate 57 made of acrylic or opal glass.
A pair of light guides 34, 34 from the side (see figure (A)) or two light guides 34, 58 from the side and back (see figure (A)).
(see Figure (B)) provides illumination light. The light is uniformly reflected and bent by the diffusing substance in the diffuser plate 57, and illuminates the observation range on the inner surface of the tube. Further, a light shielding film is attached to the back surface of the diffusion plate 57 except for the circular hole 57a. In this case, since the illumination light illuminates the observation range 17a from within the area of the reflected light beam L in the longitudinal direction, halation occurs.
Since the entire surface of the diffuser plate 57 is uniformly diffused and illuminated, strong halation does not occur, and the adverse effect on observation, measurement, etc. is small.

In FIG. 24, the exit end face of the light guide is used as an exit window, and is shaped differently so as to substantially surround the entrance window of the objective optical system. Figure (A) shows a light guide 59 having a horseshoe-shaped exit end face 59a, Figure (B) shows a light guide 60 having a substantially U-shaped exit end face 60a, and Figure (C) shows a light guide 60 having a substantially U-shaped exit end face 60a. The light guides 61 each have are shown. These exit windows partially overlap the reflected light beam L that spreads in the longitudinal direction, causing halation at this portion, but are effective when the observation distance to the inner surface of the tube is short, that is, for near-point observation.

[0043]

Effects of the Invention As described above, according to the side-viewing endoscope for intraduct observation according to the present invention, the light flux area of the image formed by the tube inner surface of the entrance pupil of the objective optical system overlaps with the exit window of the illumination optical system. Since the objective optical system and the illumination optical system are arranged so as not to cause any interference, it is possible to eliminate halation caused by specular reflection on the inner surface of the tube, and improve light distribution characteristics and illumination efficiency, making it possible to observe and measure the inner surface of the tube. etc. can be performed well.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the main parts of the distal end of an endoscope, showing the first principle of the present invention.

FIG. 2(A) is an orthogonal sectional view showing a light beam forming an image of the entrance pupil on the inner surface of the tube, and FIG. 2(B) is a longitudinal sectional view.

FIG. 3 shows a first embodiment of the present invention, (A)
FIG. 5 is an orthogonal cross-sectional view, FIG. 3B is a longitudinal cross-sectional view, and FIG. 3C is a diagram showing the positional relationship between the illumination lens and the objective lens.

FIG. 4 is a diagram similar to FIG. 3 showing a modification of the first embodiment.

FIG. 5 is a diagram similar to FIG. 3 for a second embodiment;

FIG. 6 shows a third embodiment, in which (A) is a side surface;
(B) is a plan view, and (C) is a main part configuration diagram seen from the front.

FIG. 7 shows the fourth embodiment, (A), (B), (
C) is a view similar to FIG. 3, and (D) is a side view of a single fiber.

FIG. 8 is a diagram showing a modification of the single fiber in FIG. 7;

FIG. 9 is a diagram showing a modification of the objective optical system.

FIG. 10 is a diagram showing another modification of the objective optical system.

FIG. 11 shows a fifth embodiment, in which (A) is a front view, (B) is a configuration diagram of the main parts seen from the side, and (C) is a perspective view of the main parts of the optical system.

FIG. 12 is a side view showing the objective optical system of the sixth embodiment.

FIG. 13 is a diagram similar to FIG. 3 showing a seventh embodiment.

FIG. 14 is an explanatory diagram of the second principle of the present invention, (A)
(B) is an orthogonal sectional view of the tube, and (B) is a longitudinal sectional view.

FIG. 15 is a diagram showing the relationship between the position of the entrance pupil and the spread of the luminous flux.

[Figure 16] Figure 14 when the entrance pupil is above the central axis O
This is a similar diagram.

FIG. 17 shows an eighth embodiment, in which (A) is a front view and (B) is a side view of the main part configuration.

FIG. 18 shows a ninth embodiment, in which (A) is a front view and (B) is a main part configuration diagram seen from a plane.

FIG. 19 is an orthogonal sectional view of the inner surface of the tube for explaining the third principle of the present invention.

FIG. 20 shows a tenth embodiment, in which (A) is a front view and (B) is a side view of the main part configuration.

FIG. 21 shows an eleventh embodiment, in which (A) is a front view, (B) is a side view, (C) is a main part configuration diagram seen from a plane, and (D) is a side view of a flat glass. .

FIG. 22 shows a twelfth embodiment, in which (A) is a front view and (B) is a side view of the configuration of the main parts.

[Figure 23]
(A) and (B) are modified examples of the illumination means of the illumination optical system.

FIGS. 24A, 24B, and 24C are views showing modified examples of the light guide exit end surface, respectively.

FIG. 25 is a partial cross-sectional view showing a conventional rotating device for the distal end of an endoscope.

FIG. 26 is a longitudinal cross-sectional view showing an endoscope having an outer diameter that is approximately the same as the inner diameter of the tube.

FIG. 27 is an orthogonal cross-sectional view of an endoscope equipped with a centering device.

FIG. 28 is a longitudinal cross-sectional view of the endoscope of FIG. 27;

FIG. 29 is a configuration diagram of main parts of a conventional endoscope.

FIG. 30 shows a conventional endoscope, in which (A) is a side view and (B) is a front view of the main parts viewed from the direction of arrow P.

[Figure 31] (A) is a configuration diagram of the main parts of a conventional endoscope, (B)
is an orthogonal sectional view.

FIG. 32 is a configuration diagram of main parts of a conventional endoscope.

[Explanation of symbols]

1 Endoscope 17 Tube inner surface 17a Observation range 18 Entrance pupil 21 Solid-state image sensor 22, 49
Objective lens 23, 29 Brightness diaphragm 24, 34 Light guide 25, 48 Illumination lens

Claims (2)

[Claims] 1. A tube having a substantially circular cross section is an object to be observed, and a centering device is attached to the endoscope, or the outer circumference of the endoscope is made to be approximately equal to the inner diameter of the tube due to the outer shape of the endoscope itself. The side-viewing endoscope for observing inside the tube is used to observe the inner surface of the tube, and the distal end thereof is provided with an entrance window for an objective optical system and an exit window for an illumination optical system. An objective optical system and an illumination optical system are arranged so that a light flux area of an image formed by the inner surface of the tube in the entrance pupil does not overlap with an exit window of the illumination optical system. Visual endoscope. 2. The side-viewing endoscope for intraductal observation according to claim 1, wherein the entrance pupil of the objective optical system is located near the central axis of the tube.