JPH11342105A - Endoscope observation device - Google Patents

Abstract

(57) [Summary] First and second positions located on both sides of observation means
The third illuminating means is provided between the illuminating means for improving the illuminance at the center of the observation area when observing at the closest observation distance, minimizing the loss of the illuminating light amount, and providing a clear image. Obtain an observation image. SOLUTION: An observation window 10 is provided on a distal end surface of a distal end hard portion 2c of an insertion portion 2, and a first illumination window 11a and a second illumination window 11b are provided at positions on both sides of the observation window 10 therebetween. A third illumination window 11c is provided. Lighting window 11
Illumination means 13a to 13c including light guides 40a to 40c and illumination lenses 41a to 41c are attached to the light guides a to 11c.
On the distal end side, 0 is branched into first and second light guides 40a and 40b comprising substantially the same number of optical fibers and a third light guide 40c having half the number of optical fibers. Is the observation window 10 at the hard end portion 2c.
Are inclined at a predetermined angle so as to face the center line of the observation visual field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endoscope used for medical purposes and the like, which is provided with an observation means having an objective lens whose observation distance is variable.

[0002]

2. Description of the Related Art An endoscope is inserted into a patient's body or the like.
It is used for observing the inside of a body cavity and the like,
An insertion portion connected to a main body operation portion which is operated by an operator or the like is inserted into a body cavity or the like. Since the inside of the body cavity or the like is a dark place, it is necessary to illuminate to observe the body cavity. Therefore, an illumination unit and an observation unit are provided at a substantially coplanar part at the tip of the insertion unit. The illuminating means uses a light guide in which ultrafine optical fibers are bundled as a light transmitting means, and is provided with an illuminating lens composed of a diverging lens for diverging illuminating light at an emission end of the light guide. The observation means has an objective lens, and an image guide made of an optical fiber bundle faces the image forming position of the objective lens, and a solid-state image pickup device such as a CCD is arranged at the image forming position. In some cases, an optical image of an observation target portion is converted into an electric signal. The former is an optical endoscope, and observation is performed by touching an eyepiece provided in connection with a main body operation unit. In the latter case, an electric signal from the solid-state imaging means is taken into a processor and processed by the processor to generate a video signal, and the video is displayed on a monitor attached to the processor.

[0003] When observing the inside of a body cavity using an endoscope, for example, when observing a position away from the observation means, for example, in the stomach, the body cavity wall is inspected more accurately. May be observed from a close position. Such a configuration including a focus adjustment mechanism for adjusting the focus of the objective lens accurately at the time of observation from a close position is disclosed, for example, in Japanese Patent Publication No. Sho 61-53698. And 1 cm or less from the inner wall of the body cavity,
In particular, there is a configuration in which the focus can be adjusted to an extremely close position, such as 1 mm to 2 mm, so that the inner wall of the body cavity can be inspected with higher accuracy.

By the way, even if the focus of the objective lens constituting the observation means is adjusted so as to be accurately adjusted to the observation target portion, accurate observation cannot always be performed. As already described, since the inside of the body cavity is a dark place, it is illuminated by the illumination means including the light guide and the illumination lens,
It is necessary to illuminate the entire observation target portion so that the illuminance is as uniform as possible. If a dark portion occurs in the observation area by the observation means, it may be difficult to perform the observation or the observation itself may not be possible. In addition, if there is extreme uneven illumination, particularly if there is a very bright portion, the difference in brightness between the entire observation region becomes large, which also hinders observation. In particular, in the case of an electronic endoscope using a solid-state imaging device, if there is a portion that is too bright, the pixel of that portion in the solid-state imaging device becomes saturated, blooming or smear occurs, and illumination If the illuminance of the light is uneven, the dynamic range is reduced even if the pixels are not saturated, so that an image of good quality cannot be obtained.

[0005] In order to suppress illumination unevenness in the observation area of the observation means, for example, as shown in Japanese Patent Application Laid-Open No. 6-169879, a mounting portion of the observation means is provided at a position on both sides of the observation means. 2. Description of the Related Art It has been widely used that two illuminating units are installed at positions separated by an equal distance, and the two illuminating units emit substantially the same amount of illumination light. In this case, in order to concentrate the illumination light as much as possible on the observation area in the observation target portion, the two illumination means are arranged as close as possible to the observation means under the condition that no harmful light enters the observation means. I have to.

[0006]

Incidentally, the insertion portion of the endoscope needs to be made as small as possible in view of being inserted into the body cavity. The small-diameter insertion portion is provided not only with an observation means and two sets of illumination means, but also with a treatment tool insertion channel for inserting forceps and other treatment tools as necessary. The means may be provided with a mechanism for ejecting the cleaning fluid. Therefore, the apertures of the two illuminating means are extremely small, and are substantially similar to a point light source. However, since the illuminating light from the light guide is diverged by the diverging lens, if the inner wall of the body cavity, which is the observation target, is separated by a certain distance from the illuminating means, it is almost in the observation area of the inner cavity wall by the observing means. Illumination can be performed with uniform illuminance. However, when the observation distance is short, it is not possible to sufficiently diverge light with a diverging lens, and when illuminating from an extremely close position, such as only a few mm from the observation target part, especially only about 1 to 2 mm apart, In addition, an illuminance distribution is generated in which the illuminance at the center position of the illumination window is extremely high, and the illuminance rapidly decreases as approaching the periphery.

From the above, even if the illumination means is disposed on both sides of the observation means, when the observation distance is less than 1 cm, particularly several mm, the observation area is not sufficient. The illuminance at the center position is the lowest, the illuminance increases toward the periphery of the observation visual field, and the illuminance distribution in which the periphery becomes the brightest occurs. In the prior art, the illuminating means is brought as close as possible to the observing means in order to concentrate the illuminating light on the observing area. However, the illuminance of the peripheral portion becomes extremely high, and the difference between light and dark becomes more remarkable. As a result, especially when photographing with a solid-state imaging device, the illuminance in the peripheral portion is too high, and the pixel at that position may be saturated to cause blooming, smear, and the like, and the dynamic range may be reduced to reduce the S / N. As a result, there is a problem that a clear image cannot be displayed on the monitor screen, and the accuracy of inspection and diagnosis deteriorates.

The present invention has been made in view of the above points, and an object of the present invention is to reduce the loss of illumination light and to reduce the illuminance of the observation area when observing at the closest observation distance. The purpose is to minimize variations.

[0009]

In order to achieve the above-mentioned object, the present invention provides an observing means provided with an objective lens having a variable observing distance on a substantially same plane at the distal end of an insertion portion, and a light guide for illumination. And an illuminating means for irradiating illumination light toward an observation target portion via a diverging lens for an endoscope, wherein the illuminating means is provided at positions on both sides of the observation means. 1st, 2nd lighting means, these 1st,
And a third lighting means provided at a position between the second lighting means.

Here, the third illuminating means suppresses a decrease in illuminance at the center of the observation area, particularly when observing at a close observation distance, and the optical axis of the third illuminating means is observable. It is preferable that the means is disposed so as to be inclined at a predetermined angle in the optical axis direction of the means. The light guide is usually composed of a bundle of optical fibers. The light guide is integrated on the light source side, but can be configured to be branched into three on the distal end side. Then, approximately the same number of optical fibers are distributed to the first and second illuminating means to form first and second light guides, and the third illuminating means provides these first and second illuminating means. It is desirable to configure a third light guide by distributing a smaller number of optical fibers than the means. In this case,
If the portion on the emission end side of the third light guide constituting the third illumination means is extended in an oblique direction, the optical axis of the illumination light diverging lens in the third illumination means does not need to be bent. Can be inclined toward the optical axis direction of the observation means.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, FIG. 1 shows an overall configuration diagram of an endoscope, in which 1 is a main body operation unit,
Reference numeral 2 denotes an insertion portion into a body cavity or the like, and reference numeral 3 denotes a universal cord. The main body operation unit 1 is used by an operator or the like to perform an operation while holding it by hand, and the insertion unit 2 is connected to the main body operation unit 1. The insertion portion 2 is a flexible portion 2a that bends in an arbitrary direction along the insertion path from the portion continuously provided to the main body operation portion 1, and an angle portion 2 is provided at the tip of the flexible portion 2a.
b, and a tip end hard portion 2c is connected to the angle portion 2b. The angle portion 2b is for directing the distal end hard portion 2c in a desired direction.
Is provided with a mechanism for observing the inside of a body cavity.

As shown in FIG. 2, an observation window 10 and three first to third illumination windows 1 are provided on the distal end surface of the distal end hard portion 2c.
1a, 11b and 11c are provided. The observation window 10 and the three illumination windows 11a, 11b, 11c are all arranged on the same plane. First illumination window 11a
And the second illumination window 11b are disposed at positions on both sides of the observation window 10 and substantially symmetrical with respect to the center line L of the distal end hard portion 2c, and the third illumination window 11c is It is disposed at a position between the first illumination window 11a and the second illumination window 11b, and in the illustrated example, is provided near the first illumination window 11a. Note that the third illumination window 11c needs to be arranged at a position between the first and second illumination windows 11a and 11b, but it is not always necessary to arrange the third illumination window 11c at the illustrated position. , The center line L.

As shown in FIGS. 3 and 4, the observation means 10 is mounted on the observation window 10, and the first to third illumination windows 11a, 11b, 11c are shown in FIGS. As shown, the first to third lighting means 13a, 13a
b, 13c are mounted. Further, in addition to these, a treatment tool outlet 14 for leading out a forceps or other treatment tool is formed on the distal end surface of the distal end hard portion 2c, and a nozzle 15 for supplying a cleaning fluid to the observation window 10 is provided. Is also provided. Note that the above configuration is a direct-viewing type endoscope in which the observation field is directed in the axial direction of the insertion section 2, and when configured as a side-viewing type endoscope, a flat surface is formed on the side surface of the distal end hard portion. hand,
The above-mentioned parts are formed on this flat surface.

The observation means 12 mounted on the observation window 10 comprises an objective optical system 20 and an image pickup unit 21. The objective optical system 20 includes an objective lens group 23 provided in a lens barrel 22a mounted on the main body block 22, and a main body block 2 for bending the optical axis of the objective lens group 23 by 90 °.
2 and a prism 24 fixed by means such as bonding. The imaging unit 21 has a solid-state imaging device 26 such as a CCD mounted on a substrate 25. The solid-state imaging device 26 is bonded and fixed to a prism 24, and its light receiving surface is located at an image forming position of the objective optical system 20. Be placed. A large number of wires are connected to the substrate 25, and the wires are bundled in the middle to form a single cable 27. This cable 27 is inserted into the universal cord 3 from the inside of the insertion section 2 via the main body operation section 1. It is extended and is detachably connected to a processor via a connector (not shown) provided on the universal cord 3.

The rear lens group constituting the objective lens group 23 is a movable lens 23a movable in the optical axis direction.
Thereby, when the observation window 10 is brought close to the observation target portion,
By moving the movable lens 23a in the optical axis direction, the focus can be adjusted so that the observation target portion is accurately focused. The movable lens 23a is attached to a lens frame 28 independent of the lens barrel 22a, and the lens frame 28 moves in the optical axis direction along a guide portion 22b provided on the main body block 22. . The lens frame 28 is connected to the guide portion 22 of the main body block 22.
b and extends into the drive chamber 22c;
In the drive chamber 22c, it is screwed to a screw shaft 29 composed of, for example, a helicoid screw. The screw shaft 29 is supported by a support member 30 connected to the main body block 22.
It is supported rotatably. A stopper 29a is provided on the screw shaft 29, and a connecting member 31 is provided at an end of the screw shaft 29, and the stopper 29a and the connecting member 3 are provided.
By sandwiching the support member 30 with the screw shaft 2,
9 will be held so as not to move in the axial direction. Further, a nut 32 having a stopper function is attached to the tip of the screw shaft 29, so that the lens frame 28 can reciprocate between the nut 32 and the stopper 29a.

The connecting member 3 connected to the proximal end of the screw shaft 29
1 is connected to a flexible shaft 33. The flexible shaft 33 is formed of, for example, a contact coil and rotates in both directions, so that it is constituted of a double contact coil. The flexible shaft 33 is
The control cable is inserted into a flexible tube 34 provided to be connected to the support member 30, and the flexible shaft 33 and the flexible tube 34 constitute a control cable. Then, this control cable is
The flexible tube 34 is fixedly held at its proximal end, and a forward / reverse rotating motor (not shown) as a rotation driving means is provided at the proximal end of the flexible shaft 33. By operating the motor, the flexible shaft 33 is rotated around the axis in the flexible tube 34, and the screw shaft 29 is rotated to rotate the lens frame 28 provided with the movable lens 23 a. It will move in the optical axis direction. Note that the flexible shaft 33 may be configured to be rotated manually.

On the other hand, the illuminating means 13a to 13c provided in each of the illuminating windows 11a to 11c comprises a light guide and an illuminating lens comprising a diverging lens. The light guide transmits illumination light from a light source, and has a structure that can be bent in an arbitrary direction, for example, because the light guide is drawn around the entire length of the endoscope including the insertion portion 2 that has become a flexible structure. Has become. In FIG. 5, reference numeral 40 denotes a light guide,
The light guide 40 is formed by bundling a large number of ultrafine optical fibers, and the base end side, that is, the side connected to the light source is unified.
The first, second, and third light guides 40a, 40b are branched into three near the connecting portion to the angle portion 2b.
b, 40c. The first light guide 40a constitutes the first illuminating means 13a, and the second and third light guides 40b, 40c similarly constitute the second and third illuminating means 13b, 13c, respectively. Each lighting window 11
a to 11c include illumination lenses 41a and 41b, respectively.
And 41c are mounted, and the emission ends of the first, second, and third light guides 40a, 40b, and 40c are arranged at positions facing these illumination lenses 41a, 41b, and 41c. Therefore, the first light guide 40
The illumination light from the third to fourth light guides 40a, 40b, and 40c is the first, second, and third illumination lenses 41, respectively.
a, 41b, and 41c.

First and second light guides 40a, 40b
Are composed of substantially the same number of optical fibers, and as shown in FIG. 6, insertion holes 4a and 4b provided in the distal end hard portion 2c.
, And face the first and second illumination lenses 41a and 41b, respectively. On the other hand, the third light guide 40c includes the first and second light guides 40c.
a, 40b, the number of which is smaller than the number of optical fibers, for example, approximately half of the number of optical fibers. At the distal end hard portion 2c, as shown in FIG. Is inserted into the insertion hole 4c inclined at a predetermined angle so as to face the optical axis direction. However, the third illumination lens 41c is arranged so as to be in a direction parallel to the other illumination lenses 41a and 41b and the optical axis of the objective lens group 23. Therefore, the first
The second lighting means 13a and 13b are main lighting means, and the third lighting means 13c functions as auxiliary lighting means for these.

In this endoscope, by moving the movable lens 23a of the objective lens group 23 constituting the objective optical system 20 provided in the observation window 10 in the direction of the optical axis, several m
It is also possible to take a picture at a close distance of about m, for example, 1 to 2 mm. Therefore, the relationship between the observation field of the objective optical system 20 in the observation window 10 and the illumination range of each of the illumination means 13a to 13c when observing at the closest observation distance will be described. First, the observation field of view in the observation window 10 and the first and second illumination windows 11a and 11a provided with the first and second illumination means 13a and 13b constituting the main illumination means.
FIG. 8 shows the relationship with the illumination range according to 11b.

When the closest observation distance is d and the object S to be observed separated by the closest observation distance d is imaged by the solid-state image sensor 26 of the observation means 12, an image taken by the solid-state image sensor 26 is taken. Is a display area where F is displayed on the monitor screen, and C is a center position of the display area F. The display area F is different from the visual field range of the objective optical system 20, and is an area actually displayed on the monitor screen. The image displayed on the monitor screen is a limited range including the center position of the field of view of the objective optical system 20. In displaying an image observed by an endoscope on a monitor screen, it is common to mask a portion around the screen and limit a display area of the entire monitor screen. Therefore, in this case, the display area F is an area actually displayed on the screen, that is, a part inside the mask area. In addition,
If no masking is performed, the entire monitor screen naturally becomes the display area F.

Illumination windows 11a, 11 at the same distance from each other on the left and right sides of the observation window 10 provided with the objective optical system 20.
Illumination light from the illumination lenses 41a and 41b provided in b is emitted toward the observation target portion S while diverging. In the illumination light from the illumination windows 11a and 11b, the light having the angle θ1 reaches the center C of the display area F, and the light having the angle θ2 reaches the end of the display area F. And the lighting window 11
When the illumination light from a and 11b is applied to the observation target portion S, the position of the optical axis center A has the highest illuminance, and the illuminance decreases continuously toward the periphery. Lighting lens 4
The closer the positions of 1a and 41b are to the observation target portion S, the smaller the divergence of light is. Therefore, the illuminance distribution shows a steeper change, and the nearest observation distance d is several mm.
Then, the illuminance distribution of the illumination light with respect to the observation target portion S undergoes a very steep change as shown in FIG. Light from the two illumination windows 11a and 11b is irradiated to the center C of the display area F in the observation target portion S and the vicinity thereof. As a result, the illumination in the observation target portion S including the display area F has an illuminance distribution as indicated by a two-dot chain line in FIG.

As is apparent from FIG. 9, when the display area F is assumed to be constant, if the distance between the optical axis center A of the illumination windows 11a and 11b and the center of the display area F is increased,
Although the change in the illuminance of the illumination light in the display area F decreases, the illuminance itself decreases. That is, both illumination windows 11a, 11
The farther b is from the observation window 10, the more the change in illuminance is suppressed. Therefore, it is desirable to minimize the distance between the illumination windows 11a and 11b with respect to the observation window 10.
Then, the illuminance of the entire display area F including the center position C is increased. However, light of a portion of the illuminance distribution showing a steep change is taken into the display area F. And the difference in illuminance becomes extremely large.

When a solid-state image sensor 26 is used as the observation means 12, in order to obtain a clear image, it is necessary to minimize the difference in illuminance between the center and the end of the display area F as much as possible. If the illuminance at the darkest part, that is, at the position of the center C of the display area F, is about twice as bright as the brightest part, that is, at the end of the display area F, the solid-state imaging device 26 is required. An image having a good S / N ratio can be obtained with a certain degree of dynamic range. When the illuminance is twice or more, the image quality of the image displayed on the monitor screen is reduced even if the sensitivity is corrected by the processor.

Third illumination means 13c as auxiliary illumination means
Is provided to increase the amount of illumination with respect to the center C of the display area F so as to balance the illuminance in the display area F at the closest observation distance d and to achieve uniform illuminance as a whole. is there. The third lighting means 13c includes first and second
Is provided between the illumination means 13a and 13b, and the third light guide 40c faces the direction of the observation means 10, so that the illumination light from the third illumination means 13c is You will head to C. As a result, as shown by the one-dot chain line in FIG.
Since the illumination light by 3c is applied to the display area F,
The illuminance distribution as a whole is as shown by a dotted line in the figure, and the illuminance of the center C of the display area F where the illuminance is the lowest and the vicinity thereof is improved.

However, the illumination by the third illumination means 13c is merely an auxiliary illumination means for increasing the illuminance at the center C of the display area F, and is provided by the first and second illumination means 13a, 13a.
If the same amount of illumination as in b is applied, the illuminance at the center C becomes too high, and an annular dark fringe is generated between the center C and the peripheral portion. Is not always preferred. Therefore, in the third lighting means 13c, the first and second lighting means 1 are used.
The light amount is made smaller than 3a and 13b. In order to have this change in the amount of light, the number of optical fibers constituting the light guide 40 is reduced. As a result, it is possible to adjust the third illumination means 13c so that the illuminance can be easily and reliably illuminated with the target light amount. For example, if the number of optical fibers of the third light guide 40c is approximately half of the number of optical fibers of the first and second light guides 40a and 40b, if the illuminance at the center C of the display area F is extremely high, In addition, the difference in illuminance in the entire display area F can be suppressed to twice or less.

On the other hand, when the distal end hard portion 2c of the insertion section 2 is moved away from the inner wall of the body cavity and observation is performed at a position farther than the closest observation distance d, the light diverging function by the illumination lenses 41a to 41c is exhibited. I will be. Therefore, it is possible to illuminate with sufficiently uniform illuminance only by the first and second illuminating means 13a and 13b which are the main illuminating means. However, since the third illuminating means 13c which constitutes the auxiliary illuminating means irradiates the illumination light toward the center C of the display area F, the illuminance at the part of the center C becomes considerably high. The third light guide 40c is illuminated with illumination light via the illumination lens 41c, and the light emitted from the third light guide 40c is diffused by the illumination lens 41c. The illuminance at the center C does not become extremely high. In addition,
In order to prevent the third illumination means 13c from irradiating the illumination light when observing at a position farther from the closest observation distance d, the exit end face of the third light guide 40c and the illumination lens 41c are required. What is necessary is just to comprise so that a shutter may be provided between them.

By the way, what is irradiated on the observation target portion S is direct illumination from the illumination windows 11a to 11c.
As shown in FIG.
With the configuration of mounting 0, the difference in illuminance of the illumination light can be further reduced. The hood 50 is provided for stabilizing the distal end portion of the insertion section 2 when the hood 50 is brought into contact with the inner wall of the body cavity to perform observation near the closest observation distance. Therefore, the hood 5 is placed on the inner wall of the body cavity.
When illumination light is emitted from the illumination windows 11a to 11c in a state where the leading end of the zero is in contact, the illumination light is reflected from the observation target portion S and further reflected on the inner surface of the hood 50. As a result, the observation target portion S is also indirectly illuminated by the reflected light, and the indirect illumination is applied substantially uniformly over substantially the entire observation target portion. Therefore, in order to further increase the reflection efficiency by suppressing the inner surface of the hood 50 to a white or other reflective surface and to suppress the variation in the amount of light of indirect illumination, it is preferable that the reflective surface is roughened so as to diffusely reflect. .

Here, if the length of the hood 50 protruding from the insertion portion 2 is shortened to be equal to or less than the closest observation distance d, the observation distance becomes shortest when the tip of the hood 50 contacts the inner wall of the body cavity. It becomes less than the observation distance d. However, the projecting length of the hood 50 hinders the observation field of view by the objective lens group 23 provided in the observation window 10. Therefore, the projecting length of the hood 50 is the same as the closest observation distance d or a length that does not hinder the observation field of view.

[0029]

As described above, according to the present invention, the first and second illumination means are provided at both sides of the observation means, and the third illumination means is provided at a position between the first and second illumination means. By providing the illumination means, when observing at the closest observation distance, the illuminance at the center of the observation area is improved, the loss of the illumination light amount is minimized, and the entire observation area is observed. Variations in illuminance are suppressed to a minimum, and a clear observation image is obtained.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an endoscope.

FIG. 2 is an external view of a distal end portion of an insertion section.

FIG. 3 is a cross-sectional view of a distal end portion of an insertion portion at a position XX in FIG. 2;

FIG. 4 is a diagram illustrating a configuration of an observation unit.

FIG. 5 is a diagram illustrating a configuration of a lighting unit.

FIG. 6 is a cross-sectional view of the distal end portion of the insertion section at the position YY in FIG. 2;

FIG. 7 is a cross-sectional view of the distal end portion of the insertion section at the ZZ position in FIG. 2;

FIG. 8 is an explanatory diagram showing a relationship between an observation field of view of an observation window and an illumination range from an illumination window when observing at a closest observation distance.

FIG. 9 is a diagram showing an illuminance distribution of illumination light by an illumination unit at a closest observation distance.

FIG. 10 is a sectional view similar to FIG. 2 with a hood attached.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Main body operation part 2 Insertion part 2c Hard tip part 10 Observation window 11a-11c Illumination window 12 Observation means 13a-13c Illumination means 20 Objective optical system 21 Imaging unit 23 Objective lens group 23a Movable lens 26 Solid-state image sensor 29 Screw axis 33 Flexible Shaft 34 Flexible tube 40, 40a-
40c Light guide 41a-41c Lighting lens 50 Hood

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Naotake Mimori 1-324 Uetake-cho, Omiya-shi, Saitama Fuji Photo Optical Machine Co., Ltd.

Claims (4)

[Claims] 1. An observation unit having an objective lens with a variable observation distance is provided on substantially the same plane at the distal end of an insertion section, and illumination light is emitted from a light guide to an observation target section via a diverging lens for illumination. In an endoscope observation apparatus provided with illumination means, the illumination means includes first and second illumination means provided at positions on both sides of the observation means, and the first and second illumination means are provided.
And a third illumination means provided at a position between the illumination means. 2. An endoscope observation apparatus according to claim 1, wherein an optical axis of said third illumination means is inclined at a predetermined angle toward an optical axis direction of said observation means. 3. The light guide is formed by bundling optical fibers. The light guide has a single connection side to a light source, and a front end side is branched into three to form the first and second light guides. By distributing approximately the same number of optical fibers to the illuminating means, the first and second light guides are formed.
2. An endoscope observation apparatus according to claim 1, wherein the third light guide is constituted by distributing a smaller number of optical fibers than the first and second lighting means to the first lighting means. . 4. A structure in which a portion of the third light guide constituting the third illumination means on an emission end side extends obliquely toward a mounting direction of the observation means. 4. The observation device for an endoscope according to 3.