JP2001017380A - Exciting light filter for fluorescent endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exciting light filter which is capable of suppressing the transmittance to a wavelength of fluorescence to a lower level by superposing and arranging a plurality of filer plates. SOLUTION: The fluorescent endoscope device consists of an endoscope 10, a light source section 20 and an image pickup section 30. The light source section 20 is provided with a xenon lamp 21, a reflector 22 and a Fresnel condenser lens 23. Illumination light is transmitted by a light guide fiber bundle 23 and illuminates a subject. The exciting light filter 60 which, is high in the transmittance to the wavelength of the exciting light to generate spontaneous fluorescence from the vital tissue among the illumination light and is low in the transmittance to the wavelength of the spontaneous fluorescence, is arranged between the condenser lens 23 and the fiber 17. The exciting light filter 60 is composed of the three flat planar filter plates. The first and third filter plates 61 and 63 are arranged in parallel to each other. The second filter plate 62 is arranged to incline at about 10 deg. with the other two sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excitation light filter used for an illumination system of a fluorescent endoscope.

[0002]

2. Description of the Related Art Biological tissues contain a plurality of endogenous substances that emit fluorescence (autofluorescence) when irradiated with excitation light in a specific wavelength region. Differs between organizations. The fluorescent endoscope irradiates excitation light to a living tissue to be imaged and observes the intensity distribution of the fluorescence emitted from the living tissue, and can determine an abnormality of the living body based on the distribution.

[0003] The fluorescent endoscope is provided with an illumination optical system for irradiating excitation light and a photographing optical system for photographing a fluorescent image. The wavelength range of the excitation light is in a wavelength range shorter than the wavelength range of the fluorescence. Further, since the intensity of the fluorescence emitted from the living tissue is weak, in order to accurately capture only the fluorescence emitted from the living tissue, it is necessary to suppress the light in the wavelength range of the fluorescence included in the illumination light to an extremely low level. .

Therefore, when a white light source is used as the light source of the illumination optical system, an excitation light filter having a high transmittance for the wavelength of the excitation light and a low transmittance for the wavelength of the fluorescent light is provided. As the excitation light filter, a coloring filter in which a dye is mixed in glass can be used. However, in the coloring filter, since the mixed dye emits fluorescent light, this may cause noise and hinder the capturing of a fluorescent image.

Therefore, as the excitation light filter, a vapor deposition filter in which a multilayer dielectric layer is vapor-deposited on a transparent substrate is generally used. Further, in the conventional fluorescence endoscope, it is difficult to sufficiently reduce the transmittance for the wavelength of the fluorescence with one filter plate, and thus a plurality of filter plates are stacked so as to be parallel to each other at a predetermined interval. Have been placed. For example, if two filter plates each having a transmittance of 5% for the wavelength of the fluorescent light are used in an overlapping manner, the transmittance for the wavelength of the fluorescent light can be calculated to be 0.25%.

[0006]

However, in a configuration in which a plurality of filter plates are stacked in parallel like a conventional excitation light filter, there is a problem that the transmittance for the wavelength of the fluorescence to be cut off does not decrease as calculated. is there. It is considered that this is mainly due to multiple reflection due to surface reflection of a plurality of filter plates. For example, FIG.
When the two filter plates f1 and f2 are arranged in parallel as shown in FIG. 3, the light beam A passes through the two filter plates as normal light without being reflected on each surface, whereas the light beams B, C and D Is reflected an even number of times on any surface of the filter plate, and travels in the same direction as the regular light as multiple reflected light. That is, the light beam B is reflected on the exit surface of the first filter plate f1 after being reflected on the incident surface of the second filter plate f2, the light beam C is reflected in the second filter plate f2, The light beam D is reflected by the incident surface of the second filter plate f2 and the incident surface of the first filter plate f1, and travels in the same direction as the normal light.
When such multiple reflected light exists, even when a plurality of filter plates are used in a stacked manner, the transmittance of the fluorescence wavelength cannot be reduced as calculated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. By arranging a plurality of filter plates in an overlapping manner, it is possible to reduce the transmittance for the wavelength of the fluorescent light to a low value. An object of the present invention is to provide an excitation light filter for an endoscope.

[0008]

SUMMARY OF THE INVENTION The present invention provides an excitation light for a fluorescent endoscope which has high transmittance for the wavelength of excitation light for generating autofluorescence from living tissue of illumination light and has low transmittance for the wavelength of autofluorescence. In an optical filter, a plurality of filter plates are arranged one on top of another, and at least one surface of the filter plates is arranged such that reflected light reflected between the surfaces of the filter plates is directed in a direction different from normal light transmitted through the filter plates. ,
It is characterized by being arranged so as to be non-parallel to another surface.

According to the above arrangement, the surface reflected light between the filter plates arranged in an overlapping manner is directed to an optical path different from the normal transmitted light while being reflected between the non-parallel surfaces, and It is possible to prevent the reflection component from becoming noise.

In order to prevent multiple reflections between the surfaces of the filter plate, it is desirable that the angle between the non-parallel surfaces is 10 degrees or more based on the parallel state. When three filter plates are provided in the form of a flat plate, two of them can be arranged parallel to each other, and one can be arranged non-parallel to the other two.

Further, at least one of the filter plates may have a prism shape in which one surface and the other surface are non-parallel. When three such prismatic filter plates are provided, the following arrangement is conceivable. (1) The outer surfaces of the filter plates at both ends are made parallel to each other, and the surfaces facing the intermediate filter plate and the filter plates at both ends are both made parallel. (2) The outer surfaces of the filter plates at both ends are made parallel to each other, and both the intermediate filter plate and the surfaces facing the filter plates at both ends are made non-parallel. (3) Make all surfaces of the filter plate non-parallel to any other surface.

Further, the filter may be composed of two prismatic filter plates and one flat filter plate disposed therebetween. In this case, the outer surfaces of the filter plates at both ends can be made parallel to each other, and both surfaces facing the intermediate filter plate and the filter plates at both ends can be made non-parallel.

Further, at least one of the filter plates is
A meniscus lens having no power can be formed. In this case, the filter can be constituted by two meniscus lens-shaped filter plates and one flat filter plate arranged between them. The filter plates at both ends can be arranged with the concave surfaces facing each other, and the flat filter plate can be arranged so that its normal is inclined with respect to a straight line connecting the centers of curvature of the curved surfaces.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an excitation light filter for a fluorescent endoscope according to the present invention will be described below. First, FIG.
The overall configuration of the fluorescence endoscope apparatus to which the excitation light filter is applied based on the above will be schematically described. The fluorescent endoscope apparatus includes an endoscope 10, a light source unit 20, and an imaging unit 30, and a monitor 50 includes a video switching device 40 in the imaging unit 30.
Connected through. The endoscope apparatus of FIG. 1 has a configuration in which a normal photographing mode for photographing a subject illuminated by white light as it is and a fluorescent photographing mode for photographing an image by autofluorescence generated by irradiating excitation light can be selected. is there.

The endoscope 10 includes an insertion section 11 inserted into a body cavity, and an operation section 1 having one end connected to a base end of the insertion section 11.
2 and a light guide connection pipe 13 branched from the operation unit 12 and connected to the light source unit 20. An imaging unit 30 is connected to the other end of the operation unit 12.

At the tip of the insertion section 11, an observation window 18 and an objective optical system 15 are arranged. Further, an image guide fiber bundle (hereinafter, referred to as “IGFB”) 14 is provided in the endoscope 10 from the distal end of the insertion section 11 to the other end of the operation section 12. The objective optical system 15 forms a subject image on the incident end face of the IGFB 14 by the light transmitted through the observation window 18, and the subject image is transmitted by the IGFB 14 and guided to the imaging unit 30 via the eyepiece 16.

In the endoscope 10, a light guide fiber bundle (hereinafter referred to as "LGFB") extending from the distal end of the insertion section 11 to the light source section 20 through the light guide connecting pipe 13 is provided.
17) are provided. The light source unit 20 is provided with a xenon lamp 21 as a white light source, a reflector 22, and a Fresnel condenser lens 23. Illumination light emitted from the xenon lamp 21 is condensed by the reflector 22, the condenser lens 23 and is transmitted to the LGFB17. Incident. The illumination light is L
The light is transmitted by the GFB 17, and illuminates the subject via a light distribution lens 19 provided with the observation window 18 at the tip of the insertion section 11.

The light source section 20 includes a condenser lens 23 and an LGF
An excitation light filter having a high transmittance with respect to the wavelength of the excitation light for generating autofluorescence from living tissue and a low transmittance with respect to the wavelength of the autofluorescence among the illumination light emitted from the xenon lamp 21 between the incident end face of B17. 60 are arranged.

The excitation light filter 60 of the first embodiment is
In order to sufficiently reduce the transmittance with respect to the wavelength of the fluorescent light, the first, second, and third filter plates 61, 62, and 63 are configured by arranging three flat filter plates one over the other at a predetermined interval. I have. The excitation light filter 60 is provided so as to be freely inserted into and removed from the optical path by a solenoid (not shown). In the normal imaging mode, the excitation light filter 60 is separated from the optical path as shown by a solid line in FIG. It is located in the optical path as shown. Therefore, the subject is illuminated with white light in the normal imaging mode, and is illuminated with only excitation light in the fluorescence imaging mode.

A switching mirror 32 for switching the direction of light emitted from the eyepiece 16 is arranged in the image pickup section 30.
In each optical path switched by the switching mirror 32, an imaging optical system 30a for normal photographing and a CCD camera 31,
An imaging optical system 33a for fluorescence imaging and a CCD camera 41 are provided. In the normal photographing mode, the switching mirror 32 retreats from the optical path as shown by a solid line in the figure, and the light from the eyepiece 16 forms an object image on the CCD camera 31 via the normal photographing optical system 30a. I do. On the other hand, in the fluorescent imaging mode, the switching mirror 32 is disposed so as to make an angle of about 45 degrees with respect to the optical path as shown by the broken line in the figure, and the light from the eyepiece 16 is changed by the switching mirror 32 and the fixed mirror 33. Reflected image forming optical system 33 for fluorescence imaging
A fluorescent image is formed on the CCD camera 41 via a.

A fluorescent filter 35 having a high transmittance at the wavelength of fluorescence and a low transmittance at the wavelength of excitation light is provided between the switching mirror 32 and the fixed mirror 33. Further, an imaging optical system 33a for fluorescence imaging and a CCD
In the optical path between the camera 41 and the camera 41, an image intensifier 34 for greatly amplifying the brightness of the image is provided.

CCD camera 31 and CCD camera 41
Are connected to the video switching device 40, respectively. The video switching device 40 displays a subject image in white light on the monitor 50 based on the image signal from the CCD camera 31 in the normal shooting mode, and displays the fluorescent image on the monitor 50 based on the image signal from the CCD camera 41 in the fluorescent shooting mode. Display the image.

Next, the configuration of the excitation light filter 60 according to the present embodiment will be described. FIG. 2 is an enlarged view of the excitation light filter 60 shown in FIG. Excitation light filter 60
Is formed by arranging first, second, and third filter plates 61, 62, and 63 in the order from the incident light side. Each of the filter plates 61, 62, and 63 has a transmittance of about 80 to 250 nm to 370 nm, which is the wavelength range of the excitation light, alone.
% And a transmittance of about 5% or less for light having a wavelength longer than 400 nm, which is the wavelength range of fluorescence, and is a deposition filter having three transmittances in order to lower the transmittance in the wavelength range of fluorescence. Are located.

First and third filter plates 61 and 63 at both ends
Are arranged perpendicular to the central axis of the incident light, that is, parallel to each other, and the second filter plate 62 at the center is
They are arranged at an angle of about 10 degrees with respect to a state parallel to the sheets. That is, in this example, the surface of the second filter plate 62 is set non-parallel to the surfaces of the first and third filter plates 61 and 63. According to such a configuration, the surface reflected light between the filter plates arranged in an overlapping manner is directed to an optical path different from the transmitted light while being reflected between the non-parallel surfaces, and the surface reflected component is noise. Can be prevented, and the transmittance for light having a wavelength longer than 400 nm can be suppressed to 0.1% or less while the transmittance for light having a wavelength of 250 nm to 370 nm is set to about 50% or more as a whole.

FIG. 3 is a graph showing the correlation between the transmittance and the wavelength, showing a comparison between the transmission characteristic (dashed line) of one filter plate and the transmission characteristic (solid line) of three filter plates arranged in parallel with each other. It is. In the scale of FIG. 3, the difference between the non-parallel arrangement and the parallel arrangement for the transmittance on the wavelength side longer than 400 nm cannot be distinguished from the parallel arrangement, and thus the case of the parallel arrangement having a higher transmittance in this region is shown. ing. From FIG. 3, it can be understood that even in the parallel arrangement, the transmittance of the three filter plates in the wavelength region of the fluorescence can be suppressed lower than that of one filter plate.

FIG. 4 shows a transmission characteristic (dashed line) of a single filter plate, taking out only the shorter wavelength side than the wavelength of 400 nm in FIG.
And transmission characteristics when three of them are arranged parallel to each other
(Solid line) and the transmittance characteristic (dashed-dotted line) of the excitation light filter 60 of the embodiment in which the three filters are arranged non-parallel are shown. In this wavelength range, the difference in transmission characteristics due to the difference between the parallel and non-parallel arrangements is small.

FIG. 5 is a graph obtained by extracting only the long wavelength side from the wavelength of 400 nm in FIG. 3 and enlarging the scale of the vertical axis. The transmission characteristics (solid line) when three filter plates are arranged in parallel with each other are shown. 5 shows transmittance characteristics (dashed-dotted line) of the excitation light filter 60 of the embodiment in which three filters are arranged non-parallel.
In the parallel arrangement, the transmittance exceeds 0.9%, whereas in the non-parallel arrangement, the transmittance is 0.1% over the entire region.
It is kept below.

In order to prevent multiple reflections between the surfaces of the filter plate, it is desirable that the angle between the non-parallel surfaces is 10 degrees or more based on the parallel state. If the angle is smaller than 10 degrees, it is difficult to effectively prevent multiple reflection. On the other hand, if the angle is too large, the arrangement space becomes large, and the degree of change in the transmission characteristics due to the inclination of the filter plate increases, which is not desirable.

Next, second to sixth embodiments which can be used in place of the excitation light filter 60 of the above-described first embodiment will be described. In any configuration, the surface reflected light between the filter plates is directed to a different optical path from the transmitted light while being reflected between the non-parallel surfaces, thereby preventing the surface reflected component from becoming noise. .

FIG. 6 shows a second embodiment of the excitation light filter. This excitation light filter 70 is composed of three prism-like filter plates 71, 72, 73. The filter plates 71 and 73 at both ends have the same shape, and the middle filter plate 72 has a vertex angle twice that of the filter plates at both ends.
The outer surfaces of the filter plates 71 and 73 at both ends are perpendicular to the central axis of the incident light and are parallel to each other, and both surfaces of the intermediate filter plate 72 and the filter plates 71 and 73 at both ends are opposite to each other. Parallel.

That is, in this example, the first filter plate 7
1 surface on the exit side of the first filter plate 71, both surfaces of the second filter plate 72, and the third filter plate 7
3 is set to be non-parallel, and the first filter plate 7
With respect to the first emission-side surface, the emission-side surface of the second filter plate 72 and both surfaces of the third filter plate 73 are set to be non-parallel.

FIG. 7 shows a third embodiment of the excitation light filter. This excitation light filter 80 is composed of three prism-like filter plates 81, 82, 83. The filter plates 81 and 83 at both ends have the same shape, and the middle filter plate 82 has a vertex angle slightly smaller than twice that of the filter plates at both ends. The outer surfaces of the filter plates 81 and 83 at both ends are perpendicular to the central axis of the incident light and parallel to each other, and the intermediate filter plate 82 and the filter plates 81 and 8 at both ends are perpendicular to each other.
3 are all non-parallel.

That is, in this example, the first filter plate 8
1, the surface on the exit side of the first filter plate 81, both surfaces of the second filter plate 82, and the third filter plate 8
3 is set to be non-parallel, and the first filter plate 8
The two surfaces of the second filter plate 82 and the both surfaces of the third filter plate 83 are set to be non-parallel to the surface on the emission side of No. 1.

FIG. 8 shows a fourth embodiment of the excitation light filter. This excitation light filter 90 is composed of three prism-shaped filter plates 91, 92, 93. These filter plates are of different shapes with different apex angles, and all surfaces of the filter plate are non-parallel to any other surface.

FIG. 9 shows a fifth embodiment of the excitation light filter. The excitation light filter 100 is composed of two prismatic filter plates 101 and 103 and a flat filter plate 102 disposed between them.
The filter plates 101 and 103 at both ends have the same shape, and their outer surfaces are arranged so as to be perpendicular to the central axis of the incident light and parallel to each other. Intermediate filter plate 1
Numeral 02 is arranged to be inclined with respect to the central axis of the incident light, and the intermediate filter plate 102 and the filter plates 10 at both ends are arranged.
Both surfaces facing 1 and 103 are non-parallel.

FIG. 10 shows a sixth embodiment of the excitation light filter. This excitation light filter 110 is composed of two meniscus lens-shaped filter plates 111 and 1 having no power.
13 and a flat filter plate 1 disposed between them.
12. Filter plates 111 at both ends,
Reference numerals 113 have the same shape and are arranged with the concave surfaces facing each other. The intermediate filter plate 112 is arranged so that its normal is inclined with respect to a straight line (coincident with the central axis of the incident light) connecting the centers of curvature of the curved surfaces.

[0037]

As described above, according to the present invention, by arranging at least one surface of a plurality of arranged filter plates non-parallel to another surface, a space between the filter plate surfaces can be reduced. Can be directed out of the optical path, and the transmittance of the fluorescence in the wavelength region can be suppressed to an extremely low value. Therefore, by using the excitation light filter of the present invention in the light source section of the fluorescence endoscope, light in the wavelength range of the fluorescence contained in the illumination light can be suppressed to an extremely low level, and the weak light emitted from the living tissue at the time of fluorescence imaging is obtained. This makes it possible to accurately capture fluorescent light.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of a fluorescent endoscope apparatus according to an embodiment.

FIG. 2 is an enlarged view of an excitation light filter according to the first embodiment used in the apparatus of FIG. 1;

FIG. 3 is a graph showing transmittance characteristics of a filter plate.

FIG. 4 is a graph showing a wavelength shorter than 400 nm in FIG. 3;

FIG. 5 is a graph showing a longer wavelength side than the wavelength of 400 nm in FIG. 3;

FIG. 6 is an enlarged view of an excitation light filter according to a second embodiment.

FIG. 7 is an enlarged view of an excitation light filter according to a third embodiment.

FIG. 8 is an enlarged view of an excitation light filter according to a fourth embodiment.

FIG. 9 is an enlarged view of an excitation light filter according to a fifth embodiment.

FIG. 10 is an enlarged view of an excitation light filter according to a sixth embodiment.

FIG. 11 is an explanatory diagram of multiple reflection between filter plates arranged in parallel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Endoscope 11 Insertion part 12 Operation part 13 Light guide connection pipe 14 Image guide fiber bundle 15 Objective optical system 16 Eyepiece 17 Light guide fiber bundle 20 Light source part 21 Xenon lamp 22 Reflector 23 Fresnel condenser lens 30 Imaging part 40 Video Switching device 50 Monitor 60 Excitation light filter 61, 62, 63 Filter plate

Claims (10)

[Claims] 1. An excitation light filter for a fluorescence endoscope having a high transmittance with respect to a wavelength of excitation light for generating auto-fluorescence from living tissue in illumination light and a low transmittance with respect to a wavelength of the auto-fluorescence. At least one surface of the filter plate is disposed on another surface such that the plates are arranged one on top of the other and the reflected light reflected between the surfaces of the filter plate is directed in a direction different from the normal light transmitted through the filter plate. An excitation light filter for a fluorescence endoscope, which is arranged non-parallel to the filter. 2. The excitation light filter according to claim 1, wherein an angle between the non-parallel surfaces is 10 degrees or more based on a parallel state. 3. The filter plate is provided with three flat plates, two of which are arranged in parallel with each other, and
2. The excitation light filter for a fluorescence endoscope according to claim 1, wherein the sheet is arranged non-parallel to the other two sheets. 4. The excitation light filter for a fluorescence endoscope according to claim 1, wherein at least one of the filter plates has a prism shape in which one surface and the other surface are non-parallel. 5. The three prism-shaped filter plates are provided, the outer surfaces of the filter plates at both ends are parallel to each other, and the surfaces of the intermediate filter plate and the filter plates at both ends are all opposite. The excitation light filter for a fluorescence endoscope according to claim 4, wherein the excitation light filter is parallel. 6. The three prism-shaped filter plates are provided, the outer surfaces of the filter plates at both ends are parallel to each other, and the surfaces of the intermediate filter plate and the filter plates at both ends are all opposite. The excitation light filter for a fluorescent endoscope according to claim 4, wherein the excitation light filter is non-parallel. 7. The apparatus according to claim 4, wherein three prism-shaped filter plates are provided, and all surfaces of the filter plate are non-parallel to any other surfaces. Excitation light filter for fluorescent endoscope. 8. The method according to claim 1, wherein the prism-shaped filter plates are two sheets,
The outer surfaces of the filter plates at both ends are parallel to each other, and the surfaces of the intermediate filter plate and the filter plates at both ends are opposed to each other. 5. The excitation light filter for a fluorescence endoscope according to claim 4, wherein both are non-parallel. 9. The excitation light filter for a fluorescent endoscope according to claim 1, wherein at least one of said filter plates is in the form of a meniscus lens having no power. 10. A filter plate comprising: two meniscus lens-shaped filter plates; and one flat plate-shaped filter plate disposed therebetween. The filter plates at both ends are arranged with their concave surfaces facing each other. 10. The excitation light filter for a fluorescent endoscope according to claim 9, wherein the filter plate is arranged so that its normal is inclined with respect to a straight line connecting the centers of curvature of the curved surfaces.