JPH046513A - Lighting optical system for endoscope - Google Patents

Abstract

PURPOSE:To obtain light distribution characteristics which are uniform from the center to the periphery of a visual field range to be observed by composing a coupling optical system of a lens system which has positive refracting power and a coupling light guide which is different in area between its light incidence end surface and projection end surface. CONSTITUTION:Light projected from a light-source side light guide 6 is uniformly distributed by passing through the lens system 16 and when the light passes through the coupling light guide 15, the light distribution angle of light which is made incident on the incidence end surface S3 of the endoscope-side light guide 4 is set, so that light is projected from the projection end surface Sd of the endoscope-side light guide 4 at a wide or narrow light distribution angle corresponding to the visual field angle of an observation optical system. Consequently, the wide-angle light distribution which exceeds 90 deg. can be obtained and the light distribution characteristics which are uniform from the center to the periphery of the visual field range to be observed can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an illumination optical system for an endoscope such as a rigid scope, a fiberscope, or a videoscope, in which a light guide for transmitting illumination light is of a dual type. This invention relates to an illumination optical system for an endoscope.

[Conventional technology]

There are two types of endoscope illumination optical systems: one is an integrated type that uses a long light guide to transmit light from the light source for illumination, and the other is a lens that separates the light guide into two parts, the light source side and the endoscope side, and combines them. A two-body structure connected via a system is known.

Among them, endoscopes that use an integrated light guide require the long light guide to be removed from the light source and replaced together when, for example, several types of endoscopes are to be replaced during surgery. It is extremely inconvenient to operate.

On the other hand, a two-piece light guide is convenient because it is easy to replace.

The illumination optical system of an endoscope using a dual-noise light guide is the second
It is as shown in Figure 1. In other words, an observation optical system consisting of an objective lens I, a relay lens 2, and an eyepiece lens 3,
A rigid scope 5 equipped with an illumination optical system consisting of an endoscope side light guide (fiber bundle) 4, a light guide cord 8 equipped with a light source side light guide (fiber bundle) 6 and a coupling lens system 7, and a rear The light source device 13 includes a light source lamp 1) having a reflecting mirror 10 and a condensing lens 12. Then, connect the light guide cord 8 to the light source device 13.
The light guide cord 8 is connected to the rigid scope 5 and the light from the light source is received by the light guide 6 on the light source side, and the light guide cord 8 is connected to the rigid scope 5 and the above light is transmitted to the endoscope side within the rigid scope 5 via the coupling lens system 7. The light is transmitted to the light guide 4.

By the way, as a conventional example of the combined lens system 7 used in the illumination optical system of the endoscope shown in FIG.
The one described in Publication No. 401 is known. As shown in FIG. 22, this combined lens system 7 consists of two positive lenses with their convex surfaces facing each other, and the exit end surface of the light source side light guide 6 is located near the front focal point, and the rear focal point is located near the front focal position. The entrance end faces of the endoscope-side light guides 4 are located near the respective positions.

When such an arrangement is adopted, the coupling lens system 7
The focal length of is f, and the angle that the light emitted from each fiber of the light source side light guide 6 makes with the optical axis is θ', and the angle that the light ray makes with the optical axis when it enters the endoscope side light guide 4 is θ' , if the distances from the center of the light guide at a certain point on the end face of each light guide 6°4 are r and r', respectively, then when the coupling lens system 7 satisfies the sine condition, the following equation holds. To establish.

fsinθ' = r' ・---(
1) r = f sinθ' −・−
・(2) Such a coupling lens system 7 has the effect of uniformizing the light distribution characteristics (angular distribution) of illumination light that deteriorates when passing through the inside of the light guide, so it can be used for internal viewing that requires a large angle of view. This is relatively preferable as an illumination optical system for a mirror. However, this configuration cannot be said to provide a sufficient level of improvement in light distribution characteristics around the visual field, and an illumination optical system with better light distribution characteristics has been desired.

As a device that can meet this demand, JP-A-2-50107
There is something described in the publication. The coupling lens system used in this illumination optical system is expressed as ftFLnθ' = r' −−−− instead of the above equation (1), +21.
(3) r = f tanθ' --
--(41) is satisfied.

In any case, in these conventional illumination optical systems having a combined lens system, the NA (numerical aperture) of the light incident on the endoscope-side light guide 4, that is, the light distribution angle 2θ' is determined by the field of view to be attached. It is set to match the endoscope with a wider viewing angle among multiple endoscopes with different angles, and in the case of a rigid endoscope, the maximum viewing angle is around 90°, so θ' is also 45°.
It is often set to around 30°.

Furthermore, in general, a light guide with a relatively large NA has a high refractive index of the material and is therefore highly colored, making it unsuitable for transmitting illumination light over a long distance. Therefore, a light guide with less coloration and a relatively small NA is used for the light source side light guide 6, and the NA of the light that enters the endoscope side light guide 4 through the combination lens system 7 is greatly changed, and the endoscope It is connected to the side light guide 4 to obtain an effective illumination angle.

[Problem to be solved by the invention]

Incidentally, rigid endoscopes are often used for diagnosis and treatment of the bladder, joints, etc., and can actually be used in physiological saline. Therefore, even if a rigid mirror has a viewing angle and a light distribution angle 2θ' of about 90° in the air, when actually used in saline, the above angle will be narrowed to about 65° due to refraction. It ends up. Moreover, since the insertion part of a rigid scope cannot be bent freely, the viewing direction cannot be changed during use.

Therefore, as shown in Fig. 23, several types of rigid scopes (for example, 5A, 5B, and 5C) with different viewing directions θ (x = A, B, C) are available. Although these rigid scopes are used by replacing them as appropriate, it is troublesome to replace the rigid scopes each time they are used, and this hinders the smooth progress of medical treatments such as diagnosis and treatment.

Therefore, the viewing angle of the rigid scope is 90° even in physiological saline.
If there is a wide-angle lens with an angle of about 120 degrees, that is, more than 120 degrees in the air, it would be possible to reduce the number of rigid scopes (5D, 5E) that have different viewing directions, as shown in Figure 24, and at the same time It can reduce the hassle of replacing mirrors, which is a big advantage. Also, for the illumination optical system used in such a wide-angle rigid mirror, it is necessary to achieve a light distribution angle θ' of 60 degrees or more in the air, and to obtain uniform light distribution from the center to the periphery of the viewing range. is necessary.

The coupling optical system consisting of the coupling lens system 7 disclosed in Japanese Patent Publication No. 15401/1986 uses a spherical lens, but if the focal length of the lens system is made small so that the light distribution angle θ' exceeds 50', the spherical lens The radius of curvature of the spherical surface that makes up the lens becomes smaller, the amount of aberration increases significantly, and the loss of light with a large light distribution angle increases, resulting in the problem of not being able to obtain uniform light distribution from the center to the periphery of the viewing range. arise.

Also, in the coupling optical system of JP-A-2-50107, if the focal length of the lens system is made small in order to widen the light distribution angle 2θ', the amount of aberrations will increase, and the rays that should pass around the lens will be Similarly, uniform light distribution cannot be obtained within the viewing range due to total internal reflection. Alternatively, if the radius of curvature on the optical axis is made smaller in order to shorten the focal length, the lens thickness becomes thinner or the lens thickness becomes extremely large, resulting in a shape that is impossible to manufacture. Put it away.

Furthermore, with the conventional illumination optical system described above, it is not possible to obtain a light distribution that corresponds to the various viewing ranges of the endoscope, so when a narrow-angle endoscope is used, it is difficult to illuminate areas outside the observation field of view. There is also the problem that the loss of light amount due to this is considerable.

In view of these problems, the present invention provides an illumination optical system for an endoscope that can obtain wide-angle light distribution and uniform light distribution characteristics from the center to the periphery of the visual field to be observed. The purpose is to

[Means to solve the problem]

The illumination optical system for an endoscope according to the present invention includes a light source-side light guide that transmits light from a light source from an entrance end face to an exit end face;
A coupling optical system disposed behind the exit end face of the light source side light guide, and an endoscope side light guide whose input end face is disposed at a position facing the exit end face of the light source side light guide via the coupling optical system. In the illumination optical system of an endoscope, the coupling optical system consists of a lens system (including a hologram lens and Fresnel lens) that is placed on the light source side and has a positive refractive power, and a lens system that is placed behind it and has a positive refractive power. It consists of a combined light guide whose entrance end face and exit end face have different areas, and the exit end face of the light source side light guide is located near the front focal position of the lens system, and the entrance end face of the combined light guide is located near the rear focal position of the lens system. The feature is that they are arranged respectively.

The illumination optical system described above is designed to satisfy the following conditional expressions depending on the viewing angle 2ω of the observation optical system.

(A) When 2ω≧90″ Tss/Tss>1.

(rz /f)
0.7 (B) When 2ω≦60°, T ss/T ss < 1.

(rg /f)

T ss Area r2 of the exit end surface of the combined light guide
, the radius of the exit end face of the light guide on the light source side.

f: Focal length of a lens system with positive refractive power.

NA: NA0 of the light guide on the endoscope side Also, the coupling optical system consists of a hologram lens or Fresnel lens with positive refractive power, and the exit end face of the light kite on the light source side is located near the front focal position of the hologram lens or Fresnel lens. The present invention is characterized in that the entrance end faces of the endoscope-side light guides are arranged near the rear focal position, and the following conditional expression is satisfied.

NA, ≧0.7 However, NA: NA (numerical aperture) of the endoscope side light guide
.

[For production]

The light emitted from the light source side light guide is uniformly distributed by passing through the lens system, and when it passes through the combined light guide, it is distributed on the endoscope side according to the ratio of the area of the input end surface and the exit end surface. The light distribution angle of the light incident on the incident end face of the light guide is set, and the light is irradiated from the exit end face of the endoscope side light guide at a wide-angle or narrow-angle light distribution angle depending on the viewing angle of the observation light angle thread. Ru.

Further, a similar light distribution angle can be obtained by a coupling optical system consisting only of a hologram lens or a Fresnel lens.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail based on the accompanying drawings, but the same reference numerals will be used for the same parts as in the above-mentioned prior art, and the description thereof will be omitted.

FIG. 1(a) shows the basic configuration of an illumination optical system according to the present invention, and this will be described as a first embodiment (first to third numerical examples).

In the figure, the exit end surface S2 of the light source side light guide 6, which receives light from the light source device 13 at the entrance end surface S1, and the entrance end surface S of the endoscope side ride guide 4, which has the exit end surface S, are arranged so as to face each other. are arranged, and both end faces S2. A coupling optical system 15 is arranged between S and S. This coupling optical system 15 is arranged between a lens system 16 that is disposed on the light source side and has a positive refractive power, and an entrance end surface S of the endoscope-side light guide 4 and this lens system 16. The combined light 17 includes an area T+i of the light incident end surface S and an area T+e of the light exit end surface S6, which are different in size from each other. The lens system 16 includes, for example, two positive lenses 16a, 16 whose convex surfaces face each other as in the conventional example described above.
b, and has the function of making the intensity distribution of light uniform from the center to the periphery of the field of view.

The exit end surface S2 of the light source side light guide 6 is arranged near the front focal point of this lens system 16, and the entrance end surface S of the combined light guide 17 is arranged near the rear focal point.

Moreover, in this embodiment, the viewing angle of the observation optical system of the endoscope is 2ω.
The following conditional expression is satisfied depending on the size of .

That is, (A) When 2ω≧906, Tsi/Tss> 1 (5-1) (
r 2 / f ) X v'TSi/”'T
SI> o, 7... (6-1) NA, ≧0.7...
・(7) Also, (B) When 2ω≦60°, Tss/Tsa<1. ” (5-2)Cr2
/f) XvTss/Tss<0.5... (6-2
) However, r2: radius of the exit end surface S2 of the light guide on the light source side.

f: Focal length of the lens system 16 having positive refractive power.

NA: NA (numerical aperture) of the endoscope side light guide 4 It is.

By the way, in a wide-angle endoscope where the viewing angle 2ω exceeds 90°, the illumination optical system must have a wide light distribution exceeding 90° in order to obtain a sufficiently bright image even in the peripheral part of the field of view. We have already mentioned that this cannot be achieved with the example configuration. Also, since the light source side light kite 4 is longer than the endoscope side light kite 4, in order to increase the amount of transmitted light,
It is preferable that the light distribution angle of the light from the light source device 13 that enters the incident end surface S1 of the light source side light guide 6 is about 60 degrees.

It is necessary to widen this light distribution angle by using the coupling optical system 15 to exceed 90 degrees.

Here, the combined light guide 1 as a means to widen the light distribution
7 will be explained.

As a means for widening the light distribution, a light guide 19, as shown in FIG. 25(a), in which the areas T1 and T2 of the light entrance end surface S7 and the light exit end surface S are different from each other, is conventionally known. This light guide 19 has a feature that the following relationship holds true when αI and α2 are the half values of the light distribution angles of incident light and exit light, respectively.

As can be understood from the second equation, by appropriately changing the area TT2 of the light incident end surface S and the light exit end surface SI of the light guide 19, the light distribution angle 2α2 of the emitted light can be changed to an appropriate value. .

Therefore, as shown in (b) and (c) of the same figure, the light distribution angle 2α2 of the emitted light can be changed with respect to the light distribution angle 2α1 of the incident light. However, it is not possible to make the intensity distribution of light distribution uniform.

In this way, conditional expression (5-1) can be derived from equation (8), but when T s s > 735, it is no longer possible to widen the light distribution angle on the exit side.

Moreover, the above conditional expression (6-1) is based on each area T ssl T of the entrance end surface S5 and the exit end surface S6 of the combined light guide 17.
In addition to sa, the relationship between these, the radius r2 of the exit end surface S2 of the light source side light guide 6, and the focal length f of the lens system 16 having positive refractive power is shown. Now, let θ be the value of half the light distribution angle of the light that enters the combined light guide 17 from the lens system 16, and θ be the value of half the light distribution angle of the light that exits from the combined light guide 17. 1)
From the formula, r2=fsinθS.

Also, from equation (8), sin θe − (r2/ f)xrTT5” “π
...(9) becomes.

Then, the light distribution angle of the light emitted from the coupling optical system 15 is set to 90
To make it more than 9°, θ6〉45°, which is
), the above-mentioned conditional expression (61) is established.

If conditional expression (6-1) is not met and the value of f or Tss becomes large, the coupling optical system 15 will no longer be able to widen the light distribution angle to 90° or more.

In this way, this embodiment uses a coupling optical system 15 that combines a coupling lens system 16 that can make the intensity distribution of light uniform from the center to the periphery of the field of view, and a coupling light id 17 that can change the light distribution angle. , it is possible to obtain uniform light distribution over a wider angular range than with conventional endoscope illumination optical systems.

Also, the light distribution angle of the light emitted from this coupling optical system 15 is set to 90
In order to transmit the light incident from the entrance end surface S3 of the endoscope side light guide 4 to the exit end surface S4 with as little loss as possible, the NA of the endoscope side light guide 4 must be must also be at least 90°. That is, if the NA of the endoscope side light guide 4 is NA, then
It is necessary to satisfy the above-mentioned conditional expression (7): NA, ≧0.7 (7).

When the NA becomes smaller outside this range, light with a large light distribution angle is no longer transmitted, and the peripheral part of the visual field becomes dark.

Next, the illumination optical system when the viewing angle 2ω of the endoscope is a relatively narrow angle of 60° or less will be explained based on FIG. 2 (fourth and fifth numerical examples). Regarding the combined light guide 17, based on the above equation (8), T s5<
It is sufficient to set it to T S6, and the above conditional expression (5-2)
, that is, T si/T ss< 1 (52
) is guided.

Also, in this case, since θ6<30°, according to (9) above, the above (r+/f)xv"Y'-'17]7;<o,
A conditional expression of 5 is derived.

Note that FIGS. 1(b), (c), and (d) schematically show the light distribution of light emitted from the exit end surface S2+ of the light source side light guide 6 and the exit end surface S6 of the lens system 16 coupled light guide 17, respectively. It is something.

Since this embodiment is configured as described above, the viewing angle 2
To explain the case where ω≧90°, the light that is incident on the light source side light guide 6 from the light source device 13 at a light distribution angle of about 60° is transmitted from the exit end surface S2 of the light guide 6 as shown in FIG. 1(b). When the light is emitted with the light distribution angle (θ) and light distribution shown in and passes through the lens system 16 having positive refractive power,
According to the light distribution angle 2θ5 on the incident side, the light has a uniform light distribution as shown in FIG. At this time, the light distribution angle θ5 is determined by r and /f in equation (9).

Then, when the combined light is in the id 17, the light distribution angle is changed from 2θ5 to 2θ6 without changing the uniform distribution of light distribution. At this time, the angle θ6 is T ss/T in equation (9)
Determined by s=. The light loss in the endoscope side light guide 4 is suppressed, and the light distribution angle (
For example, 120° in the air) is injected from the injection end surface S4,
Illuminate the observation area.

Furthermore, when the viewing angle 2ω of the endoscope is an included angle of 60° or less at the end surface, the light emitted from the light source side light guide 6 follows the arrangement shown in FIG. 2(b), as shown in FIG. By passing through the lens system 16 which is obtained with an optical angle 2θ5 and a light distribution and has a positive refractive power, it becomes light with a uniform light distribution as shown in FIG. The light is incident on the end surface S5.

Then, the light distribution angle decreases from 2θ5 to 2θ6 without changing the uniform distribution of light in the combined light guide 17.

Therefore, the light distribution angle becomes narrower, and at the same time, the amount of light that illuminates the viewing range can be increased.

Note that the viewing angle 2ω of the endoscope varies from a high magnification with an included angle of about 30 degrees to a range of 1 to 1 depending on the part and purpose of use of the endoscope.
Various types of illumination systems are becoming necessary, ranging from ultra-high angles of about 20 degrees or more, and the light distribution of the illumination optical system will also need to range from narrow-angle to ultra-wide-angle to match the viewing angle. . Therefore, it is suitable for actual use that the lens system 16 having positive refractive power and the coupling light guide 17, which constitute the coupling optical system in the illumination optical system of the present invention, have the following configuration.

That is, (i) the lens system 16 having positive refractive power is detachable from at least the endoscope-side light guide 4, and when it is fixedly attached to the light source-side light guide 6, the lens system 16 has a positive refractive power. r,/f are set so as to have a light distribution angle 2θ suitable for the most frequently used viewing angle of the mirror (generally about 60° to 80°).

In addition, (ii) the combined light guide 17 is detachable from at least the light source side light guide 6, and when it is set and attached to the endoscope side light guide 4, the combined light guide 17 is attached to the light guide 4 on the endoscope side. Light distribution angle 2θ.

Set TS, /T, so that it has .

In addition, when 0.8<θ, /θ6<1.2, the effect of expanding (or reducing) the light distribution angle by the combined light guide 17 becomes weak, so as a combined light guide, θ5
/θ, ≦0.8, or 1.2≦θ5/θ6 is preferably used.

As described above, according to this embodiment, the light distribution angle of the light emitted from the exit end surface S4 of the endoscope side light guide 4 can be achieved in the air at 120° or more in accordance with the wide viewing angle of 90° or more. At the same time, uniform light distribution characteristics can be obtained from the center to the periphery of the viewing range.

Moreover, without reducing the radius of curvature of the lens system 16 (
This can be achieved. It is possible to obtain light distribution that corresponds to various viewing angles, and when the viewing angle is a narrow angle, it is possible to obtain a light distribution angle that corresponds to this and increase the amount of light, and by illuminating areas outside the observation field of view. Loss of light amount can be prevented.

FIG. 3 shows a second embodiment of the present invention.
As shown in a), the lens system 16 having positive refractive power is
Consists of a single convex lens. Figure (b),
(c) and cd) are the exit end surface S0. 3 schematically shows the light distribution of light emitted from the exit end surface S6 of the lens system 16 and the coupled light beam F17, respectively. In this example, a lens system 16 that satisfies the above-mentioned equations (3) and (4) is used.

Next, FIG. 4 shows a third embodiment of the present invention,
As the coupling optical system 15, a Fresnel lens 21 having a positive refractive power is arranged, for example, as shown in a sixth numerical example to be described later.

Therefore, in order to obtain a wide light distribution exceeding 90 degrees,
Even if the light distribution angle from the Fresnel lens 21 to the incident end surface S of the endoscope side light guide 4 exceeds 90° and the radius of curvature of the lens 21 becomes small, the wall thickness of the lens will not become small. Coupling optical system that can be processed and mounted without any problems 1
5 can be achieved.

Therefore, when using the Fresnel lens 21, it is easy to obtain a desired wide light distribution angle without using the combined light guide 17, but even when using the combined light guide 17 in combination, Since the lens thickness becomes thinner, the connecting part of each light guide (combining optical system 1
5) is advantageous for downsizing.

Although the lens surface 21a of the Fresnel lens 21 forms a discontinuous surface as shown in FIG. 4, this does not pose a functional problem since it is used as an illumination optical system.

Incidentally, FIG. 5 shows a fourth embodiment, in which a hologram lens 23 having a positive refractive power is arranged in place of the Fresnel lens 21 of the third embodiment.

Regarding hologram lenses, rAppliedO
ptics 15 (1976), in an article written by Bennet, the manufacturing method will be briefly explained based on FIG. 6.

That is, a coherent light flux R1° that is once focused on point 0 and then diverges, and a coherent light flux R1 that is focused on point By irradiating and developing the objects that interfere with each other on the surface of the photographic flower material 25, the photographic flower material 25 comes to have the effect of a hologram lens.At this time, the focal length of the hologram lens is set as fh. Then, the following relationship holds.However, S is the distance from the photographic aperture material surface 25 to the object position O, d and n are the thickness and refractive index of the transparent substrate 24, respectively, and b is the distance between the photographic aperture material surface 25 of the transparent substrate 24 and When the distance from the opposite surface to the imaging position I, μ is λ, the reproduction wavelength, and λ2 is the wavelength when creating the hologram lens, μ=
It is a numerical value defined by λ0/λ2.

As can be seen from this formula (101), a hologram lens can be created with an arbitrary focal length f, including positive and negative, by changing the conditions for irradiating two coherent lights onto the photographic aperture material surface 25 at the time of creation. In addition, the focal length of the hologram lens changes by changing the reproduction wavelength λ, but when used as a lens for an illumination system as in this example, the hologram lens can also be used alone. There is no problem above.

Also in the third and fourth embodiments, the NA of the endoscope-side light guide 4 needs to satisfy the above-mentioned conditional expression (7).

As shown in FIG. 7 or 8, the Fresnel lens 21 or the hologram lens 23 described above is used as the lens system 16 of the first embodiment, and the Fresnel lens 21 or the hologram lens 23 and the endoscope side light guide 4 are used as the lens system 16 of the first embodiment. The incident end surface S of
, the coupling light may place the id 17 between.

FIG. 9 shows the fifth embodiment, and FIG. 9(a) shows the lens system 16 in the first embodiment with the light source side light guide
The connecting light is arranged on the support body 27 of the endoscope, and the connected light is arranged on the endoscope main body 28 that supports the endoscope side light guide 4. Further, in FIG. 1B, both the lens system 16 and the combined light guide 17 are arranged in the endoscope body 28.

Note that the above-mentioned Fresnel lens 21 or hologram lens 23 may be arranged in place of the lens system 16 or the lens system 16 and combined light guide 17.

Furthermore, in the illumination optical system, in addition to the above-mentioned coupling optical system 15, the light distribution is expanded at the exit end surface S4 of the endoscope side light guide 4 in order to further improve the light distribution in the peripheral part of the field of view. That is valid.

Portions of the exit end surface S4 of the endoscope-side light guide 4 that have been designed in this manner will be described below as sixth to thirteenth embodiments.

FIG. 10 shows a sixth embodiment, in which an endoscope-side light guide 4 is arranged so as to surround an objective lens 30 of an observation optical system.
The fiber bundle 4a is arranged in a ring shape, and its exit end surface S4 is cut to be conically inclined outward.

This embodiment relates to an illumination optical system for a wide-angle endoscope whose viewing direction is the longitudinal direction of the endoscope.
The light emitted from the beam is spread out.

FIG. 1) shows a seventh embodiment, and relates to a wide-angle endoscope in which the viewing direction is inclined by about 30 degrees with respect to the longitudinal direction of the endoscope. In the figure, the exit end surface S of the endoscope-side light guide 4 is divided into a plurality of parts in the middle, thereby widening the light distribution angle.

In the figure, the tip of the observation optical system includes a field-of-view changing prism 32 for changing the observation optical path, and this prism 32.
The correction prism 33 is arranged with a slight space between the
A glass plate 34 and a negative lens 35 supported by the glass plate 34 to widen the field of view are sequentially arranged.
Further, a cover glass 36 is bonded to the front surface thereof.

In the eighth embodiment shown in FIG. 12, a plurality of endoscope-side light guides 4 themselves are arranged, and each exit end surface S4 is oriented in a different direction.

The ninth embodiment shown in FIG. 13 relates to a wide-angle endoscope in which the viewing direction is tilted about 70" with respect to the longitudinal direction of the endoscope, and like the seventh embodiment, the endoscope side light is Guide 4
The injection end surface S4 is divided into a plurality of parts.

In the observation optical system, the visual field conversion prism 32' constitutes a positive lens, and a positive lens 37 is also provided behind it.
A correction prism 33 is arranged to support a negative lens 35.
A shielding member 38 is arranged in parallel.

It should be noted that the invention is not limited to the above-described embodiments, as long as the plurality of exit end surfaces S of the endoscope-side light guide 4 face different directions.

Moreover, as another means, an illumination lens for light diffusion having the same shape as this may be provided on the exit end surface S4 of the endoscope side light guide 4.

That is, in the strategist embodiment shown in FIG. 14, a ring-shaped optical member 40 on which a plurality of concave surfaces 40a as shown in FIG. It's spread out. Alternatively, a ring-shaped optical member 41 in which a negative toric surface 41a is formed in an annular shape as shown in FIG.
is used (the cross section appears the same as the optical member 40 in Figure (a)).

Further, in the thirteenth embodiment shown in FIG. 15, a hologram lens 42 with negative or positive power shown in FIG. May be used.

In the thirteenth embodiment shown in FIG. 16, the exit end surface S of the endoscope side light guide 4 is formed, for example, in a crescent shape, and a plurality of concave surfaces 43a shown in FIG.
A crescent-shaped optical member 43 on which a negative toric surface 44a is formed, or a similar optical member 44 on which a negative toric surface 44a is formed is used. In this case, the optical axes of the optical members 43 and 44 are
It is configured not to be perpendicular to the outer plane of the optical members 43 and 44 (see Figure (a)).

Alternatively, as shown in FIG. 17 as a thirteenth embodiment, a crescent-shaped hologram lens 45 with positive or negative power or a Fresnel lens may be used.

Next, in the thirteenth embodiment shown in FIG. 18, a liquid light guide 47 is used as the light guide 6 on the light source side. In this case, since the liquid light guide 47 has a backing fraction (ratio of the area through which light passes to the cross-sectional area of the light guide 47) of 1, the loss of light emitted from the light source can be minimized.

In addition, in the illumination optical system of the present invention, in order to increase the amount of light emitted from the exit end surface S4 of the endoscope side light guide 4, in the coupled light kite 17, a core that contributes to light transmission with respect to each fiber is It is possible to increase the area ratio.

This will be explained with reference to FIG. 19 as the thirteenth embodiment.
At the incident end surface S5 of the coupled light guide 17 shown in FIG. The shape is shown in the figure (
As shown in b), it is formed into a regular hexagon.

In a fiber, the thickness of the rad necessary for transmitting light is determined regardless of the fiber spacing, and is usually 2 to 3 microns. On the other hand, the combined light guide 17
The length may be about 1 am, and it does not need to be flexible. Therefore, there is no functional problem even if the core spacing of each fiber 17a on the incident end surface S5 of the coupled light guide 17 is set as thick as described above.

Moreover, it is better to form the end face shape of the core 17b in a regular hexagonal shape (Figure (b)) than to form the core 17b circularly as shown in Figure (C), as shown in Figure (C). The cladding 17C can be shared between the core 17b (conduit shape) and the core 17b in the area Ts5 of the entrance end surface Ss.
The area C5 occupied can be increased. Further, in such a conduit fiber, it is preferable that the following conditional expression be satisfied in order to increase the amount of emitted light.

Cs/T s5≧0.6 ---
-100 Next, FIG. 20 shows a thirteenth embodiment, in which the lens system 16 in the first embodiment is constructed by single fiber lenses 47a and 47b. As a result, the light traveling toward the outer peripheral portion of the lens is totally reflected, and loss of illumination light from this portion can be prevented.

Next, numerical examples of the lens system 16 and the like applied to each embodiment of the present invention will be shown.

1) Figure 1(a) is a diagram showing the configuration of this embodiment, and its first data is shown below.

R=■ d,=1.3 R2=■ d 2 =2 n 1= 1.883
v 1=40.78R3=-5,302 d3=0.2 R,=5.302 d,=2.0 R5=■ ds=1.88 R6:(X) r2=1.75 θ5-35° f=3.
053 7S5=9.17T,,=4.59 θ
a”54.2°NA, =0.8775, =3.06 θ, =83.5°NAt =1.00 Second numerical example The second data in Figure 1 (a) is shown below. .

R=■ d, =3.32 R+ = beauty d r =2.5 n 1=1.883
5 = 40.78 R3 = -9,304 d8 = 0.22 R, = 9.304 d, = 2.5 n+ = 1.883 1/
2 =40.78R, =o.

d s −3,47 R,=■ r2=2.25 θ5=25° f =5.324
In the case of Ts,=22.9Tss”7.63 θ,=
47.1°NA, =0.87 Third Numerical Example The third data of FIG. 1(a) is shown below.

R, = ■ d, = 1.7 R2:CX1) d 2 = 2.5 n 1 = 1.883 v
1=40.78Rh = -6,812 d+=0.26 R,=6.812 d4 =2゜5 n= =1.883
ν+ =40.78R5-■ d, =2.2 R,=mir2 =2.25 θ5 =35° f =3.92
3TS,=15.14T5. When =7.57 θ
g=54.2°NA, =0.87 Fourth Numerical Example FIG. 2(a) is a diagram showing the configuration of this example, and the first data thereof is shown below.

R, = ■ d, = 0.9 R2 = ω d2 = 1.8 n, = 1.883 v, = 4
0.78R, = -4,295 a, = 0.16 R, = 4.295 d * ” 1.8 12 = 1.883 ν2
=40.78R5=■ a5=1.43 Re=■ r:=1.75 θ5 =45° f =2.47
3 When 7s5=6.0373,=12.06 θ
6-30° NA, =o, a6T s+-24,12 θ, =20.7°NA, =0.56 Fifth Numerical Example The second data of FIG. 2(a) is shown below.

R, = 17.277 d2 = 2.03 n, = 1.883 v, =
40.78R,=-4 d+=0.15 R,=4゜d, =2.03 n2=1.883 v, =
40.78R5=-17,277 r2=1.75 θ,=57.3Of=2.08
When Tsi=4.37s==8.60 θ, =3
6.5°NA, =0.66T5. = 17.2
θ, =24.9°NA, =0.56 Sixth Numerical Example FIG. 4 shows the configuration of this example, and the formula and data showing the configuration of the Fresnel lens 21 are shown below.

R=f.(n-1) tan φ=h/R n=1.492 f=2 However, n: the refractive index of the glass used for the Fresnel lens 21.

h: Distance from the optical axis of any point on the Fresnel surface.

φ: An angle between the Fresnel surface and a plane perpendicular to the optical axis.

In addition, in the above-mentioned first to fifth numerical examples, RR2...
is the radius of curvature of the end surface or lens surface of each light guide, d,
, d2... is the distance between the end surface of each light guide and the lens surface, n l ! nt is the refractive index of each lens;
C2 is the Atsube number of each lens.

〔Effect of the invention〕

As described above, according to the illumination optical system for an endoscope according to the present invention, the coupling optical system is composed of a lens system having a positive refractive power and a coupling light guide whose light entrance end face and light exit end face have different areas. Therefore, it is possible to obtain a wide-angle light distribution exceeding 90°, and it is also possible to obtain a uniform light distribution characteristic from the center to the periphery of the viewing range to be observed.

Further, when the viewing range is a narrow angle, it is possible to obtain light distribution at a narrow angle, and the amount of illumination light in the viewing range can be increased accordingly.

Furthermore, the lens system employed in the coupling optical system does not have a thin lens recursion or an extremely thick lens.

Further, since the coupling optical system is constituted by a Fresnel lens or a hologram lens having positive refractive power, a uniform light distribution over a wide angle can be obtained.

[Brief explanation of drawings]

FIG. 1 shows a first embodiment of the illumination optical system for an endoscope according to the present invention, in which (a) is a sectional view of the main part, and (b) is a light distribution characteristic of light emitted from the light guide on the light source side. A diagram showing (
c) is a diagram showing the light distribution characteristics of light emitted from a lens system with positive refractive power, (d) is a diagram showing the light distribution characteristics of light emitted from a coupled light guide, and Fig. 2 (a) is a diagram showing the light distribution characteristics of light emitted from a lens system with positive refractive power. Cross-sectional views of main parts of an illumination optical system equipped with a combined light guide for obtaining a angular light distribution angle, (b), (c), and (d) are shown in Fig. 1 (b),
Figures similar to (c) and (d), respectively, and Figures 3 (a) and (b).
, (c), (d) show the second embodiment.
Figures similar to b), (c), and (d), respectively; Figures 4 and 5 are diagrams showing the third and fourth embodiments of the coupling optical system; Figure 6 explains the method for manufacturing a hologram lens. Figures 7 and 8 are diagrams showing modifications of Figures 4 and 5, respectively.
FIGS. 9(a) and 9(b) are sectional views of main parts showing the fifth embodiment,
FIG. 10 is a sectional view of the main part of the tip of the endoscope side light guide showing the sixth embodiment, FIG. 1), FIG. 12, FIG. 13,
Figures 14, 15, and 16. Figure 17 shows numbers 7, 8, 9, 10, 10-, and 13, respectively. 18 is a schematic sectional view of the illumination optical system showing the strategist 4 embodiment, and FIG. 19 is a diagram showing a combined light guide illustrating the strategist 5 embodiment. hand(
a) is a side cross-sectional view, (b). (c) is a view of the entrance end surface, FIG. 20 is a schematic sectional view of the illumination optical system showing the Takushi Roku embodiment, FIG. 21 is a sectional view of the main part showing a conventional endoscope, and FIG. 22 is the combined lens system. cross-sectional view, second
Figure 3 is an explanatory diagram showing the viewing direction of a conventional illumination optical system.
Figure 4 is a diagram similar to Figure 23 of the desired illumination optical system;
FIG. 5 is an explanatory diagram of the combined light guide. 4... Endoscope side light guide, 6... Light source side light guide, 15... Combined optical system, 16... Lens system, 17... Combined light guide, 21... ...
Fresnel lens, 23... Hologram lens. Figure 1

Claims (3)

[Claims] (1) A light source side light guide that transmits light from the light source from the incident end face to the exit end face, a coupling optical system arranged behind the exit end face of the light source side light guide, and a light source side In an endoscope illumination optical system including an endoscope-side light guide in which an input end face is disposed at a position facing an exit end face of the light guide, the coupling optical system is disposed on the light source side and has a positive refraction. It consists of a lens system having a high power, and a coupled light guide placed behind the lens system and having a light incident end face and a light exit end face each having a different area, and the light source side light guide is located near the front focal point of the lens system. An illumination optical system for an endoscope, characterized in that an exit end face and an entrance end face of the combined light guide are located near a rear focal position. (2) The endoscope according to claim (1), wherein the following conditional expressions are satisfied depending on the viewing angle 2ω of the illumination optical system of the endoscope. Mirror illumination optics. (A) When 2ω≧90°, T_s_5/T_s_6>1, (r_2/f)×√[T_s_5/T_s_6]>0.
7, NA_4≧0.7, (B) When 2ω≦60°, T_s_5/T_s_6<1, (r_2/f)×√[T_s_5/T_s_6]<0.
5. However, T_s_5: Area of the incident end face of the combined light guide, T_s_6: Area of the exit end face of the combined light guide, r_2: Radius of the exit end face of the light source side light guide, f: Focal point of the lens system with positive refractive power. Distance, NA_4: NA of the endoscope side light guide. (3) A light source side light guide that transmits light from the light source from the incident end face to the exit end face, a coupling optical system arranged behind the exit end face of the light source side light guide, and a light source side light guide via the coupling optical system. In an endoscope illumination optical system including an endoscope-side light guide whose entrance end face is disposed at a position facing the exit end face of the light guide, the coupling optical system may include a hologram lens or Fresnel lens having a positive refractive power. The light guide is composed of a lens, and the exit end face of the light source side light guide is arranged near the front focal position, and the entrance end face of the endoscope side light guide is arranged near the rear focal position, and the following conditional expression is satisfied. An illumination optical system for an endoscope, characterized by: NA_4≧0.7 However, NA_4: NA of the endoscope side light guide.