JP2000275547A - Endoscope and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the endoscope which holds small the difference in the lighting beam density of an observed area over a wide range from a short distance to a long distance from an observed position. SOLUTION: A lighting optical system is constituted by fixing a light guide 21, a plano-convex lens 22, and a plano-convex lens 23 to a tip cap 25 constituting a main body atop of the endoscope. An optical fiber bundle is used as a light guide bundle 21. The light emitted by an external light source is made incident on one end side of the optical fiber bundle and projected from the other end side. The plano-convex lens 22 and plano-convex lens 23 as optical elements are arranged closely to the other end side of the light guide 21. A dimming filter 24 as a dimming member which reduces the transmissivity of the optical element is formed at the center part of the convex surface of the plano-convex lens 22. This dimming filter 24 is a translucent film which is formed of metal such as Inconel, chromium, and nickel or their alloy and insensitive to wavelength and its transmissivity is set to about 50%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endoscope incorporating an illumination optical system for illuminating a region to be observed with light at a wide angle.

[0002]

2. Description of the Related Art A general endoscope is provided with a light guide for guiding and illuminating external light to a site to be observed, and a light source of the illumination system for directly or indirectly directing an object to be observed. It consists of an observation optical system for observation,
If necessary, an operating system such as forceps for excision of an affected part, collection of secretions, etc. is added, and these are housed in parallel in one tube.

[0003] Of these, the illumination system is configured to have a very small diameter, yet secure a wider illumination range with respect to the part to be observed and obtain a higher and more stable illuminance. Is required.

In a conventional illumination optical system for an endoscope, in order to realize this, a plano-convex lens as an optical element, a plano-convex lens, Convex lenses are provided, and these are housed and held by a predetermined means in a distal end cap 24 constituting the distal end portion of the endoscope.

The light beam density of such an endoscope illumination optical system has an emission angle dependency, and the ratio of the light beam density on the optical axis to that on the periphery is very large. There were problems such as halation and dark surroundings making observation difficult.

[0006]

As described above, the observation was difficult due to the large angle dependence of the light beam density of the illumination light beam.
It is conceivable to reduce the light beam density on the optical axis to reduce the difference in light beam density from the periphery. However, this method has a problem that the light density on the optical axis in a distant view becomes extremely small. For example, Japanese Patent Publication No. 3-63724 discloses that a dark substance is inserted at a central portion of a light guide to extremely reduce the light density on the optical axis in a distant view. In this case, a so-called shadow occurs in which the image of the dark matter appears on the surface to be observed, and it is difficult to observe the shadow portion. Further, in the process of manufacturing the endoscope, the step of embedding a dark substance in the light guide requires an adjustment step for maintaining uniformity of the light quantity distribution of the light guide, and has a problem that the manufacturing becomes difficult. ing.

As described above, conventionally, there has been a problem that it has been difficult to provide an endoscope which keeps a small difference in illumination light beam density in an observation region from a state where a part to be observed is close to a state where it is far away.

[0008]

According to the present invention, there is provided a light guide for guiding light emitted from a light source, and at least one optical element for distributing light emitted from the light guide at a wide angle. And an observation optical system for observing a portion illuminated by the illumination optical system, wherein a neutral density filter is provided in a partial area of the optical element. An endoscope characterized by the following.

An illumination optical system having a light guide for guiding light emitted from a light source and an optical element group for distributing the light emitted from the light guide at a wide angle, and a portion illuminated by the illumination optical system. An observation optical system for observing,
An endoscope comprising: a neutral density filter provided in a partial area of at least one optical element constituting the optical element group.

Further, an illumination optical system having a light guide for guiding light emitted from a light source and at least one optical element for distributing the light emitted from the light guide at a wide angle, and illuminated by the illumination optical system. An endoscope comprising an observation optical system for observing a part, wherein the endoscope is provided with a dimming member in a partial area of the optical element.

In these endoscopes, it is preferable that a partial region of the optical element substantially includes the optical axis of the optical element. Further, the present invention provides a light guide for guiding light emitted from a light source, at least one optical element for distributing light emitted from the light guide at a wide angle, and a dimming member provided in a partial area of the optical element. And an observation optical system for observing a part illuminated by the illumination optical system, wherein the conjugate position of the dimming member is located inside the illumination optical system. An endoscope characterized by being set.

Further, an illumination optical system having a light guide for guiding light emitted from the light source and at least one optical element for distributing the light emitted from the light guide at a wide angle, and illuminated by the illumination optical system. An observation optical system for observing a part, wherein the optical element is constituted by a set lens composed of two convex lenses, and the convex lens located on the light guide side among the two lenses Is the refractive power of P1, the refractive power of the convex lens located on the other side is P2, the focal length of the two convex lenses is f, the radius of the light guide is r, and the light is determined from the principal point position of the set lens. The distance to the light exit surface of the guide is s
When s> f, (1) f / r <1.
1, (2) 0.4 <(P1 / P2) <0.9, when s ≦ f, (3) f / r <1.3, (4) 0.35 <
(P1 / P2) <2.35, and a dimming member having a radius of 0.1 mm or more and 0.4 mm or less on the optical axis of the surface of the convex lens located on the light guide side that does not face the light guide. An endoscope provided with:

At this time, it is preferable that the light-emitting surface of the convex lens disposed on the other side has a lens surface having an infinite radius of curvature. The distance from the image-side focal position of the set lens to the paraxial imaging position of the illumination lens conjugate to the light exit surface of the light guide is d ', the average filling distance of the optical fiber constituting the light guide is L, The image-side F value of the illumination lens determined by the illumination profile of the guide is F ′, the magnification of the illumination lens in consideration of the distortion of the average object height is m ′, and the distance from the image-side focal position of the illumination lens to the surface to be illuminated is x. It is preferable that x> d ′ + 2F ′ × L × m ′ × (| x / d ′ |) holds.

The present invention also provides an illumination optical system having a light guide for guiding light emitted from a light source and at least one optical element for distributing the light emitted from the light guide at a wide angle. A method for manufacturing an endoscope including an observation optical system for observing an illuminated portion, wherein a step of providing a light reducing member in a partial region of an optical element, A step of forming an illumination optical system by being relatively fixed so as to be able to enter the element, and disposing an observation optical system so that light from the surface to be observed by light emitted from the illumination optical system can be observed. Fixing the endoscope.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a main part of an illumination optical system for an endoscope.
A light guide 21, a plano-convex lens 22, and a plano-convex lens 23 are fixed to a distal end cap 25 constituting a main body of a distal end portion of the endoscope, and an illumination optical system is configured. An optical fiber bundle is used for the light guide bundle 21. Light emitted from an external light source is incident on one end of the optical fiber bundle, and the light is emitted from the other end shown in FIG. This light guide 2
A plano-convex lens 2 as an optical element
2, and a plano-convex lens 23 are arranged. Plano-convex lens 2
A light-reducing filter 24 is formed at the center of the convex surface of the light-receiving member 2 as a light-reducing member for reducing the transmittance of the optical element. The neutral density filter 24 is a translucent film made of a metal such as Inconel, chromium, nickel or the like or an alloy thereof, and has a transmittance of about 50%.

The numerical values of the illumination optical system of this embodiment are as shown in Table 1. Where R1 to R4 are the radii of curvature of the respective surfaces,
d1 to d4 are the intervals between the surfaces, and N1 to N4 are the refractive indexes of the lenses.

[0017]

[Table 1]

The diameter of the neutral density filter is φ0.3 mm, and the transmittance is 0.3 mm.
5 The diameter of the light guide is φ1.6 mm, and the density of light emitted from each fiber depends on the light distribution angle (Fig. 2).
Reference).

FIG. 3 shows the angle dependence of the light beam density in the area illuminated by the illumination optical system. By forming a neutral density filter in a part of the lens, it is possible to reduce the difference between the light density on the optical axis and the light density on the periphery.

Further, assuming that the power of the lens is φ and the distances of the two conjugate positions of the lens from the lens are s and s ′, a neutral density filter for the above-described lens set obtained from 1 / s ′ = 1 / s + φ Conjugate position (that is, the position where the image of the neutral density filter forms)
Is located inside the plano-convex lens 23 (at a position of 0.88 mm from the emission end face toward the convex face), and on the observation side from the emission end face,
Does not create an image (shadow) of the neutral density filter.

As described above, by configuring the lens group so that the conjugate position of the neutral density filter can be set inside or near the surface of the lens, the observation region can be changed from a state where the observation region is close to a state where the observation region is far away. It is possible to keep the difference between the illumination light beam densities small, and at this time, there is no difficulty in observing the observation area due to the shadow caused by the neutral density filter.

Further, since the neutral density filter is made of a translucent member instead of a completely light-blocking material, a design for distributing the peripheral luminous flux in a continuous range on the axis of the optical axis becomes unnecessary. It is very easy to set a wide-angle and deep illumination area.

Now, since the illumination light only needs to be divergent light,
An optical element used for the illumination optical system may be an optical element other than a lens. In the endoscope shown in FIG. 4, a plano-convex lens 22 as an optical element and a flat plate 25 made of a volume diffusing material such as opal glass are arranged near the tip of the light guide bundle 21. On the convex surface of the plano-convex lens 22, a neutral density filter is formed. This illumination optical system irradiates with divergent light regardless of the presence or absence of the neutral density filter. However, by forming the neutral density filter on the plano-convex lens 22, the illumination with a small difference in the illumination light beam density is obtained in the observation area. What can be performed is the same as the endoscope of FIG. A planar diffusing material such as ground glass may be used instead of the volume diffusing material.

Although the light-attenuating filter 24 is formed as a light-attenuating member for reducing the sensitivity of the optical element, the amount of light on the optical axis can also be reduced by subjecting the same area to processing such as roughening the lens surface. It is possible. That is, it is sufficient to use an optical element having different transmittances in the vicinity of the optical axis and the other portions. By forming an appropriate neutral density filter in some areas of some lenses,
From the state where the observation part is close to the state where the observation part is far away, the difference in the illumination light density of the observation area is kept small, and the observation can be performed well.

FIG. 5 shows an overview of an endoscope of a general form having the above-mentioned illumination optical system. One end of the universal cord and a detachable connector 2 with a signal processor (not shown)
Are connected to a signal from the observation optical system, an input / output device of a power supply, a light source, and the like. Universal code 1
At the other end, an operation section 3 is provided, from which an insertion tube 4 is connected. Power is supplied from the operation unit 3 to the wire for freely bending the insertion tube 4 through the inside of the insertion tube 4 to the distal end of the insertion tube 4, the light guide 5 connected from the connector 2, and the observation optical system. Cables are inserted. In the insertion tube 4, an observation optical system arranged so that an image obtained when the above-mentioned illumination optical system illuminates the surface to be observed can be observed by a tip cap 25 integrally holding the illumination optical system. It is fixed together with the illumination optical system.

<Second Embodiment> A second embodiment will be described with reference to FIGS. In the sectional view of the main part of the distal end of the endoscope in FIG. 6, an objective optical system (not shown) for observing the inside of the subject, a light source located outside the body, A light guide 5 for guiding illumination light generated by the device to the distal end of the insertion section 4 is incorporated. The light guide 5 is composed of, for example, a plurality of optical fibers. Illumination light emitted from these optical fibers is supplied to an assembled lens 6 (see FIG.
Reference).

The group lens 6 shown in FIG. 7 is composed of two convex lenses 7 and 8, and among these convex lenses 7 and 8, the convex lens 7 on which illumination light from the light guide 5 is incident.
Is that the radius of curvature of the lens surface 7a on which the illumination light enters is r1 =
At +2.1 mm, the radius of curvature of the lens surface 8b from which the illumination light exits is r2 = -2.1 mm. The convex lens 7 has a lens thickness d1 = 1.4 mm and a refractive index n = 1.
883, focal length f1 = 1.4094 mm, magnification m1 =
It has lens characteristics of 2.46 and an effective aperture D1 = 1.8 mm.

On the lens surface 7b, a neutral density filter 11 having a radius of 0.2 mm and being coaxial with the lens 7 is provided. The neutral density filter 11 corresponds to a normal ND filter, and has a transmittance T = 0.5.

On the other hand, the convex lens 8 located on the distal end side of the insertion section 4 has a lens surface 8a on which the illumination light emitted from the convex lens 7 enters, a radius of curvature r3 = + 0.97 mm, and a lens surface 8b on which the illumination light exits. Is r4 = ∞ (infinity). The convex lens 8 has a lens thickness d.
2 = 1.3 mm, refractive index n = 1.883, focal length f2
= 1.0986 mm, magnification m2 = 0.6368, and effective aperture D2 = 1.4 mm.

In the endoscope according to the third embodiment of the present invention configured as described above, the focal length of the convex lens 7 is f1 (= 1.4094 mm), and the focal length of the convex lens 8 is f2 (= 1.0986 mm), convex lens 7 and convex lens 8
If the distance between the principal points of is given by Δ, the composite focal length f of the convex lenses 7 and 8 is

[0031]

(Equation 1) It is represented by

The distance Δ between the principal points of the convex lens 7 and the convex lens 8 is d3 (= 0.3 mm) from the lens surface 7b of the convex lens 7 to the lens surface 8a of the convex lens 8, and the lens surface 7b of the convex lens 7 Let d'H1 be the distance from the lens to the illuminated side principal point of the convex lens 7, and dH2 be the distance from the lens surface 8b of the convex lens 8 to the light incident side principal point of the convex lens 8, as follows: Δ = d3-d'H1 + dH2 The distance d′ H1 from the lens surface 7b of the convex lens 7 to the position of the illuminated principal point of the convex lens 7 and the convex lens 8
The distance dH2 from the lens surface 8b to the position of the light incident side principal point of the convex lens 8 is

[0033]

(Equation 2) Therefore, the composite focal length f of the convex lenses 7 and 8 is f
= 0.8761 mm.

On the other hand, the distance from the light emitting end face of the light guide 5 to the lens surface 7a of the convex lens 7 is d4 (= 0.4 m).
m), the distance from the lens surface 7a of the convex lens 7 to the principal point position of the convex lens 7 is dH1, and the distance from the principal point position of the convex lens 7 to the combined focal position of the convex lenses 7 and 8 is dx. Light guide 5 from composite focus position
Is expressed as S = d4 + dH1 + dx.

Here, the distance dH1 from the lens surface 7a of the convex lens 7 to the principal point position of the convex lens 7 and the distance dx from the principal point position of the convex lens 7 to the combined focal position of the convex lenses 7 and 8 are:

[0036]

(Equation 3) Therefore, the distance S from the combined principal point position of the convex lenses 7 and 8 to the light exit surface of the light guide 5 is S = 1.431.
mm, and the combined focal length f of the convex lenses 7 and 8 (= 0.
8761 mm). As a result, the illumination light incident on the convex lens 7 from the light guide 5 becomes diffused light and exits from the convex lens 8 as shown in FIG.
Wide-angle illumination characteristics can be obtained.

In the endoscope according to the second embodiment of the present invention, the diameter of the light guide 5 is set to DLG (= 1.6 m).
m), the opening angle of the light guide 5 is α (= 40 °), the distance from the light exit surface of the light guide 5 to the convex lens surface 7a is d4 (= 0.4 mm), and the effective aperture of the convex lens 7 is D1. The incident efficiency E of the illumination light incident on the convex lens 7 from the light guide 5 is

[0038]

(Equation 4) It is represented by

Here, the effective aperture of the convex lens 7 is given by D1 =
When the distance is 1.8 mm, the illumination light of E = 99.5% is incident on the convex lens 7, so that the illumination light emitted from the light guide 5 can be incident on the convex lens 7 efficiently and efficiently. The observation site in the subject can be brightly illuminated by the illumination light incident on the object.

In the endoscope according to the third embodiment of the present invention, the composite focal length of the convex lenses 7 and 8 is set to f (= 0.876).
1 mm) and the distance S (= 1.431 mm) from the combined principal point position of the convex lenses 7 and 8 to the light exit surface of the light guide 5, the distance from the image side focal position of the illumination lens 6 to the light exit surface of the light guide 5 The distance d ′ from the conjugate illumination lens 6 to the paraxial imaging position on the illuminated side is

[0041]

(Equation 5) It is represented by

Here, the composite magnification of the convex lenses 7 and 8 considering the distortion of the object height is m ′ (= 1.578), and the image-side composite F value of the convex lenses 7 and 8 determined by the illumination profile of the light guide 5 is F ′ (= 2.167), and the average filling distance of the optical fiber constituting the light guide 5 is L (= 0.023)
mm), when the distance x from the image-side focal position of the illumination lens to the surface to be illuminated is x> d ′ + 2F ′ × L × m ′ × (| x / d ′ |), the light emission of the light guide 5 is performed. The surface does not form an image on the irradiated surface, and does not hinder observation.

The average filling distance L of the optical fibers constituting the light guide 5 (a value representative of the distance between the optical fibers constituting the light guide) L is DLG (= 1.6 mm). If the number of optical fibers constituting the light guide 5 is n (= 4500),

[0044]

(Equation 6) Is required.

In the endoscope according to the third embodiment of the present invention, the ratio of the focal length f of the illumination lens 6 composed of the convex lenses 7 and 8 to the radius r of the light guide 5 is f / r <. 1.
Assuming that the ratio to 1 is 0.4 <(P2 / P1) <0.9,
As shown in FIGS. 8 and 9, the illumination half-width of the illumination light emitted from the illumination lens 6 is 100 ° or more, so that a wide-angle illumination characteristic can be obtained.

The neutral density filter 11 is provided on the lens surface 7b.
Is formed, the ray density on the optical axis does not protrude in the ray density distribution of the illumination light. In the endoscope according to the second embodiment of the present invention, when the profile of the light guide 5 is set to 40 ° as shown in FIG.
As shown in FIG. 1, the light distribution characteristic of the illumination lens 6 is 100 to 12
Since it is 0 ° and there is no projection of the light beam density on the optical axis, it is easy to visually recognize a wide angle.

<Third Embodiment> A fourth embodiment will be described with reference to FIGS. In FIG.
A light guide 5 that guides illumination light generated by the light source device to the distal end of the insertion section 4 is incorporated in the insertion section 4. The light guide 5 includes, for example, a plurality of optical fibers. Illumination light emitted from these optical fibers is incident on an illumination lens 6 (see FIG. 13) provided at a distal end of the insertion section 4. It has become.

The illumination lens 6 has two convex lenses 9, 1
The convex lens 9 located on the base end side of the insertion section 4 among the convex lenses 9 and 10 has a curvature r1 = + 1.6 mm of a lens surface 9a on which the illumination light enters, and the illumination light The radius of curvature of the exit lens surface 9b is r2 = −6.
0 mm. The convex lens 9 has a lens thickness d1 = 0.75 mm, a refractive index n = 1.883, a focal length f1 = 1.499 mm, a magnification m1 = 1.0622,
It has a lens characteristic of an effective aperture D1 = 1.8 mm.

On the other hand, the convex lens 10 located on the distal end side of the insertion portion 4 has a lens surface 10a on which the illumination light enters, a curvature r3 = + 1.6 mm, and a lens surface 1 on which the illumination light exits.
The radius of curvature of 0b is r4 = ∞ (infinity). The convex lens 10 has a lens thickness d2 = 1.3 mm, a refractive index n = 1.883, a focal length f2 = 1.812 mm,
It has lens characteristics of a magnification m2 = 1.4058 and an effective aperture D2 = 1.4 mm. Also, on the lens surface 9b,
A dimming filter 11 coaxial with the lens 9 and having a radius of 0.2 mm is provided. The neutral density filter 11 corresponds to a normal ND filter, and has a transmittance T = 0.5.

Although not shown, an objective lens for observing the inside of the subject is provided at the distal end of the insertion section 4. In the endoscope according to the second embodiment of the present invention configured as described above, the focal length of the convex lens 9 is set to f1 (=
1.4999 mm) and the focal length of the convex lens 10 is f2
(= 1.812 mm), assuming that the distance between the principal points of the convex lenses 9 and 10 is Δ, the composite focal length f of the convex lenses 9 and 10 is

[0051]

(Equation 7) It is represented by

Here, the distance Δ between the principal points of the convex lens 9 and the convex lens 10 is determined by the distance between the lens surface 9 b of the convex lens 9 and the convex lens 1.
0 to the lens surface 10a is d3 (= 0.1 m
m), the distance from the lens surface 9b of the convex lens 9 to the principal point position on the illuminated side of the convex lens 9 is d'H1, and the distance from the lens surface 10b of the convex lens 10 to the principal point position on the light incident side of the convex lens 10 is dH2. Δ = d3−d′H1 + dH2, the distance d′ H1 from the lens surface 9b of the convex lens 9 to the position of the principal point on the illuminated side of the convex lens 9 and the convex lens 1
The distance dH2 from the zero lens surface 10b to the light incident side principal point of the convex lens 10 is

[0053]

(Equation 8) Therefore, the composite focal length f of the convex lenses 9 and 10 is f = 0.943 mm.

On the other hand, the distance from the light exit surface of the light guide 5 to the lens surface 9a of the convex lens 9 is d4 (= 0.0 m).
m), the distance dH1 from the lens surface 9a of the convex lens 9 to the principal point position of the convex lens 9 and the distance dx from the principal point position of the convex lens 9 to the combined focal position of the convex lenses 9, 10 are:

[0055]

(Equation 9) Therefore, the distance S from the combined principal point position of the convex lenses 9 and 10 to the light exit surface of the light guide 5f is S = 0.3
11 mm, and the composite focal length f of the convex lenses 9 and 10
(= 0.943 mm). As a result, the illumination light that has entered the convex lens 7 from the light guide 5
As indicated by reference numeral 3, since the light is emitted from the convex lens 8 as diffused light, a wide-angle illumination characteristic can be obtained.

In the endoscope according to the fourth embodiment of the present invention, the diameter of the light guide 5 is set to DLG (= 1.6 m).
m), the opening angle of the light guide 5 is α (= 40 °), and the lens surface 9a of the convex lens 9 from the light exit end face of the light guide 5
Assuming that the distance to the lens is d4 (= 0.0 mm) and the effective aperture of the convex lens 9 is D1, the incident efficiency E of the illumination light entering the convex lens 9 from the light guide 5 is:

[0057]

(Equation 10) It is represented by

Here, the effective aperture of the convex lens 9 is given by D1 =
When the distance is 1.8 mm, the illumination light of E = 100% is incident on the convex lens 9, so that the illumination light emitted from the light guide 5 can be efficiently incident on the convex lens 9 and incident on the convex lens 9. The observation site in the subject can be brightly illuminated by the illumination light thus obtained. In the endoscope according to the fourth embodiment of the present invention, if the combined focal length of the convex lenses 9 and 10 is f (= 0.943 mm), the light distribution angle θ of the illumination light emitted from the convex lens 10 is:

[0059]

[Equation 11] Therefore, the observation site in the subject can be illuminated in a wide range.

Further, in the endoscope according to the fourth embodiment of the present invention, the composite focal length of the convex lenses 9 and 10 is set to f (= 0.
943 mm), and the distance d ′ from the combined focal position of the convex lenses 9 and 10 to the paraxial imaging position on the illuminated surface side of the illumination lens 6 conjugate to the light exit surface of the light guide 5 is d ′ = (f−1− S-1) -1-f.

Here, the composite magnification of the convex lenses 9 and 10 in consideration of the distortion of the object height is m ′ (= 1.492), and the convex lenses 9 and 10 that can be determined by the illumination profile of the light guide 5.
The image-side synthesized F value of F ′ (= 2.05)
Is defined as L (= 0.02).
If the distance x from the image-side focal position of the illumination lens 6 to the surface to be illuminated is x> d ′ + 2F ′ × L × m ′ × (| x / d ′ |) There is no image of the exit surface on the illuminated surface, and there is no hindrance to observation.

In the endoscope according to the fourth embodiment of the present invention, the ratio of the focal length f of the illumination lens 6 composed of the convex lenses 9 and 10 to the radius r of the light guide 5 is f / r <f.
1.1, assuming that the ratio of the refractive power P1 of the convex lens 9 to the refractive power P2 of the convex lens 10 is 0.35 <(P1 / P2) <2.35, as shown in FIGS. Since the illumination half-width of the illumination light emitted from the light source is not less than 100 °, a wide-angle illumination characteristic can be obtained.

The neutral density filter 11 is provided on the lens surface 9b.
Is formed, the ray density on the optical axis does not protrude in the ray density distribution of the illumination light. In the endoscope according to the third embodiment of the present invention, when the profile of the light guide 5 is set to 60 ° to 70 ° as shown in FIG. 16, the light distribution of the illumination lens 6 as shown in FIG. 10 characteristics
Since it is 0 to 120 ° and there is no projection of the light beam density on the optical axis, it is easy to visually recognize a wide angle.

[0064]

According to the endoscope of the present invention described above,
The observation is facilitated by keeping the difference of the illumination light beam density of the observation region small from the state where the observed part is close to the state far away. Further, according to the method for manufacturing an endoscope of the present invention, it is possible to easily provide an endoscope that is easy to observe.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of an illumination optical system according to a first embodiment.

FIG. 2 is a graph showing emission characteristics of the light guide according to the first embodiment.

FIG. 3 is a graph showing illumination characteristics of the illumination optical system according to the first embodiment.

FIG. 4 is a schematic sectional view showing a modification of the illumination optical system according to the first embodiment.

FIG. 5 is a schematic diagram showing a general view of an endoscope.

FIG. 6 is a schematic cross-sectional view illustrating a configuration of an illumination optical system according to a second embodiment.

FIG. 7 is a schematic sectional view showing the operation of the illumination optical system according to the second embodiment.

FIG. 8 is a graph showing illumination characteristics of the illumination optical system according to the second embodiment.

FIG. 9 is a graph showing illumination characteristics of the illumination optical system according to the second embodiment.

FIG. 10 is a graph showing emission characteristics of the light guide according to the second embodiment.

FIG. 11 is a graph showing a configuration of an illumination optical system according to a second embodiment.

FIG. 12 is a schematic cross-sectional view illustrating a configuration of an illumination optical system according to a third embodiment.

FIG. 13 is a schematic sectional view showing the operation of the illumination optical system according to the third embodiment.

FIG. 14 is a graph showing illumination characteristics of the illumination optical system according to the third embodiment.

FIG. 15 is a graph showing illumination characteristics of the illumination optical system according to the third embodiment.

FIG. 16 is a graph showing emission characteristics of the light guide according to the third example.

FIG. 17 is a graph showing illumination characteristics of the illumination optical system according to the third embodiment.

[Explanation of symbols]

1 ... Universal cord, 2 ... Connector, 3 ... Operation unit,
4 insertion tube, 5 light guide, 6 assembled lens, 7,
8, 9, 10, 22, 23: convex lens, 21: light guide, 24: neutral density filter, 25: tip cap, 26
… Diffusion plate,

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Hiroshi Fujita 1385-1 Shimoishigami, Otawara City, Tochigi Prefecture F-term in the Toshiba Nasu Plant (reference) 2H040 BA02 BA13 CA12 DA12 4C061 AA00 BB02 CC00 DD00 FF40 FF46 FF47 JJ06 NN01 QQ09 RR30

Claims (9)

[Claims] An illumination optical system comprising: a light guide for guiding light emitted from a light source; and at least one optical element for distributing light emitted from the light guide at a wide angle.
An endoscope comprising: an observation optical system for observing a part illuminated by the illumination optical system, wherein a neutral density filter is provided in a partial area of the optical element. 2. An illumination optical system having a light guide for guiding light emitted from a light source and an optical element group for distributing light emitted from the light guide at a wide angle, and a portion illuminated by the illumination optical system. An endoscope comprising: an observation optical system for observing; an endoscope provided with a neutral density filter in a partial area of at least one optical element constituting the optical element group. 3. An illumination optical system having a light guide for guiding light emitted from a light source and at least one optical element for distributing light emitted from the light guide at a wide angle.
An endoscope comprising: an observation optical system for observing a part illuminated by the illumination optical system, wherein a light reducing member is provided in a partial area of the optical element. 4. The endoscope according to claim 1, wherein a part of the optical element substantially includes an optical axis of the optical element. 5. A light guide for guiding light emitted from a light source, at least one optical element for distributing the light emitted from the light guide at a wide angle, and a dimming member provided in a partial area of the optical element. And an observation optical system for observing a site illuminated by the illumination optical system, wherein the conjugate position of the light reducing member is inside the illumination optical system. An endoscope characterized by being set. 6. An illumination optical system having a light guide for guiding light emitted from a light source and at least one optical element for distributing light emitted from the light guide at a wide angle,
And an observation optical system for observing a portion illuminated by the illumination optical system, wherein the optical element is constituted by a group of lenses composed of two convex lenses, and among these two lenses The refractive power of the convex lens located on the light guide side is P1, the refractive power of the convex lens located on the other side is P2, the focal length of the two convex lenses is f, the radius of the light guide is r, When the distance from the principal point of the lens to the light exit surface of the light guide is s, when s> f, (1) f / r <1.1 (2) 0.4 <(P1 / P2) When <0.9 s ≦ f, (3) f / r <1.3 (4) 0.35 <(P1 / P2) <2.35, and the convex lens positioned on the light guide side is:
On the optical axis of the surface not facing the light guide, a radius of 0.
An endoscope comprising a dimming member of 1 mm or more and 0.4 mm or less. 7. The endoscope according to claim 6, wherein a surface of the convex lens disposed on the other side from which light exits has a lens surface having an infinite radius of curvature. 8. The distance d 'from the image-side focal position of the set lens to the paraxial imaging position of the illumination lens conjugate to the light exit surface of the light guide, and the average filling distance of the optical fiber constituting the light guide is d'. L, the image-side F value of the illumination lens determined by the illumination profile of the light guide is F ′, the magnification of the illumination lens in consideration of the distortion of the average object height is m ′, and the distance from the image-side focal position of the illumination lens to the surface to be illuminated The endoscope according to claim 6, wherein, when the distance is x, x> d '+ 2F' * L * m '* (| x / d' |). 9. An illumination optical system having a light guide for guiding light emitted from a light source and at least one optical element for distributing the light emitted from the light guide at a wide angle.
An observation optical system for observing a portion illuminated by the illumination optical system, comprising: providing a light reducing member in a partial region of an optical element; and emitting light from a light guide. A step of forming an illumination optical system by relatively fixing a light beam so as to be incident on the optical element, and disposing an observation optical system so as to observe light from a surface to be observed by light emitted from the illumination optical system. And fixing the endoscope relative to each other.