JPS5971736A - Length measuring apparatus for endoscope - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a length measuring device for an endoscope, and more particularly, to a device for measuring the size of a subject such as a lesion in a body cavity under an endoscope. .

BACKGROUND OF THE INVENTION Conventionally, as a device for measuring the size of a subject in a body cavity or an industrial cavity using an endoscope, there is a device disclosed in West German Patent Publication No. 2847561. This device has an optical system in which a scale member is arranged between the output end face of the light guide buoy bar and an imaging lens with a shallow depth of focus, and is fixed to the outer peripheral surface of the insertion section of the endoscope along its longitudinal direction. When light is incident on the light guide fiber input end face, a scale member can be projected by the imaging lens onto an observation surface where an object to be examined is present, such as an inner wall surface of a body cavity having a lesion. 1. When observing and focusing the scale projected on this observation surface with an endoscope, the distance between the scale member and the imaging lens, the size of the projected scale, and the observation surface and the imaging lens By utilizing the fact that there is a constant distance between the two scales, the length of one scale of the projected scale can be determined, and the size of the object to be examined can be measured. However, when used in combination with an endoscope, the effective diameter of the imaging lens is on the order of a few millimeters at most, so it is impossible to realize an imaging lens with the shallow depth of focus required for the above-mentioned device. there were. In the case of an imaging lens with a deep depth of focus, the projected scale will be in focus regardless of the distance to the observation surface, so by focusing the projected scale, the constant It is impossible to accurately determine the distance between the observation plane and the imaging lens based on the relationship. Therefore, as a matter of course, it is impossible to accurately measure the size of the object on the observation surface. Even when an imaging lens with a deep depth of focus is used in the above device, if the distance between the observation surface and the imaging lens can be measured, based on the above-mentioned constant relationship, the length of one scale of the two-staged observation surface C can be determined. This makes it possible to know the size of the object to be tested. However, when the endoscope is located inside a body cavity, it is difficult to accurately know the distance between the imaging lens and an observation surface such as the inner wall surface of the body cavity.

As described above, since it was impossible to accurately measure the size of the object to be examined inside the body cavity, etc. with the conventional device, we used an imaging lens with a deep focal depth that makes this possible, as well as an observation method. There has been a demand for the development of a length measuring device for endoscopes that does not require measuring the distance between a surface and an imaging lens.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to quickly, conveniently and accurately measure the size of a lesion in a body cavity etc. using a simple operation. It is an object of the present invention to provide a length measuring device for an endoscope that can be supplied at low cost.

The present invention is characterized by a length measurement light guide formed to be inserted into a forceps channel of an endoscope, a scale projection light guide fiber disposed within the length measurement light guide, and a scale member having a scale portion. , and an imaging lens having an effective diameter of 5 cylinders or less and whose rear (output side) focal point is very close to the rear (output side) end surface of the lens; a light guide fiber for index light disposed around the imaging optical system;
'fi consists of two light sources for introducing light into each of the light guide fibers, and a light guide fiber for projecting the scale of the imaging optical system and an index onto the lesion, which is the object to be examined in the body cavity, etc. A scale image and an index image of the scale section are projected from the optical light guide fiber respectively, and adjusted so that the reference scale image and index image intersect,
At this time, the size of the lesion, etc. is measured by reading the scale on the scale as if a ruler were placed on the lesion, etc., based on the reference scale bone length calculated in advance. .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 1 to 9 of the accompanying drawings.

FIG. 1 shows the present device used in an endoscope, and the length measurement light guide 1 is configured to have a thickness and length that can be inserted into a forceps channel 3 of an endoscope 2.

A light guide fiber 4 for index light and a light guide fiber 5 for scale projection are inserted into the length measurement light guide 1 from the direction of the output end, and the input ends of both guide fibers 4 and 5 are connected to the light source box 6. guided within. As shown in FIGS. 2 and 6, the index light light guide fiber 4 is arranged around the inner circumference of the length measurement light guide 1 so that its output end surface coincides with the tip surface of the length measurement light guide 1. They are arranged in a ring along the surface. A scale projection light guide fiber 5 is disposed coaxially with the index light light guide fiber 4 via a tubular support member 7, and the output end face of the scale projection light guide fiber 5 is It is located rearward from the tip end surface of the long light guide 1.The support member 7 includes a scale plate, which is a scale member, having the same diameter, coaxially with the scale projection light guide fiber 5 and spaced apart from each other by a predetermined distance. 8 and an imaging lens 9 are supported, and the imaging lens 9
The output side end face of the length-measuring light guide 1 coincides with the end face of the length-measuring light guide 1. The imaging lens 9, the scale plate 8, and the scale projection light guide fiber 5 constitute an imaging optical system 10. The positional relationship in this imaging optical system 10 is such that the scale plate 8 is located closer to the output end face of the scale projection light guide fiber 5 than the front (incidence side) focal point of the imaging lens 9; Board 8
The distance between the exit end face of the scale projection light guide fiber 5 and the exit end face of the scale projection light guide fiber 5 is set as close as possible within a range where the mesh pattern of the exit end face of the scale projection light guide fiber 5 does not appear on the projected image. The effective diameter of the imaging lens 9 is less than 5 mm, and the rear (output side) focal point is located very close to the rear (output side) end surface of the lens. In addition, the scale plate 8
As shown in FIG. 4, two coordinate axes 11a orthogonal to each other at the center of the scale plate 8,
A scale part 13 is formed, which is made up of a plurality of straight scale marks 12 arranged orthogonally to each other.The scale part 13 is configured such that light can only pass through this U-mark part 13.

Although it is not clear in FIG. 4, each scale 12 of the scale section 13. . . . are not equally spaced scales in consideration of the distortion aberration of the imaging lens 9.

As shown in FIG. 5, the light source box 6 is provided with light sources for index light and scale projection, and optical systems associated therewith. Laser oscillator 14 as a light source for index light
The laser beam emitted from the condenser lens 15 passes through the condenser lens 15 and is converted into a parallel light beam by the collimator lens 16.The laser beam is then converted into a parallel light beam by the collimator lens 16, and the light guide fiber 4 for index light is fixed for a certain length along the circumferential surface of the conical fixing member 17. The beam is configured to be incident on the incident end face of the. As is clear from FIG. 6, the fixing member 17 has an apex angle of 20, and is arranged such that its bottom surface is perpendicular to the laser beam that is made into a parallel beam by the collimator lens 16. There is. Here, θ, which is the half apex angle of the fixed member 17, is
The refractive index of the core in the strand of the light guide fiber 4 for index light is no, and the refractive index of the cladding is n. Then, θ〈
While setting the angle of incidence to a satisfying value and setting the angle of incidence to be smaller than the receiving angle, the laser beam, which has become a parallel beam with the collimator lens 16, is incident on the light guide fiber 4 for index light. By configuring to cover the entire end face, the laser beam emitted from the laser oscillator 14 can be efficiently emitted from the output end of the index light light guide fiber 4.

As is clear from FIGS. 6 and 7, the strands of the index light light guide fiber 4 are arranged in a single layer with the same order on the incident side and the output side. On the other hand, the light emitted from the light source lamp 18, which is a light source for scale projection, is efficiently guided by a reflecting mirror 19 to a condenser lens 20, passes through a collimator lens 21, becomes a parallel beam, and then passes through a color filter 22. It is configured to enter from the entire surface of the input end of the light guide fiber 5 for scale projection. The color filter 22 creates a projected image of the scale portion in a color tone different from the color tone of the test area such as a lesion area, and
It is provided to enable adjustment of the light intensity and to easily distinguish the projected image on the scale.It is made up of multiple layers of electrochromic functional thin film elements that produce different colors such as red and blue. is decolored, and if necessary, any of the elements is selectively colored by a switching mechanism (not shown) to change the color of the projected image of the scale portion to a color tone different from the color tone of the test area. It is something that exists.

Next, the operation of this embodiment will be explained.

The length measurement light guide 1 is inserted into the forceps channel 3 of the endoscope 2 inserted into the body cavity, the laser oscillator 14 is oscillated, and the light source lamp 18 is caused to emit light. Then, the laser beam emitted from the laser oscillator 14 is expanded into a parallel beam of appropriate diameter by the condenser lens 15 and the collimator lens 16, and is incident on all the incident end faces of the strands of the index light light guide fiber 4. It is incident at an angle θ. As mentioned above, θ〈8 stones-1〆no2-no2
Since the incident angle is smaller than the receiving angle, the laser beam is transmitted within the index light light guide fiber 4, and as shown in FIG. , and is emitted as a conical beam at an emission angle O. On the other hand, the light emitted from the light source lamp 18 is turned into a substantially parallel light beam with an appropriate diameter by the continuum lens 20 and the collimator lens 21, and after passing through the color filter 22, the light is sent to the light guide fiber 5 for scale projection. It is incident perpendicularly to the incident end face.

The incident light is transmitted within the scale projection light guide fiber 5, illuminates the scale plate 8, and illuminates the scale portion 13.
The scale portion 13 is imaged on the inner wall surface of the body cavity by the imaging lens 9. At this time, since the effective diameter of the imaging lens 9 is small and the irradiation light from the scale plate 8 enters the scale projection light guide fiber 5 as a substantially parallel light beam, the angular depth of field of the image is very large. It is deep, and is in focus almost regardless of the distance from the exit end surface of the imaging lens 9 to the inner wall surface of the body cavity. In addition, in FIG. 8, AA' is the front principal plane of the imaging lens 9, and BB' is the rear principal plane of the imaging lens 9, and the rear focal point is the imaging lens 9. Since it is located very close to the output end face, the distance 1 to the inner wall surface of the body cavity and the size of the image are approximately proportional to each other.

Here, the principle of length measurement will be explained. In FIG. 8, light is emitted from the output end face of the light guide fiber 5 for scale projection to reach the second scale on the scale portion 13 of the scale plate 8 (A in FIG. 4).
The light that has passed through point ) has a small spread solid angle, so if it is approximated by a single ray, it travels parallel to the central axis C of the imaging lens 9, and paraxially it travels parallel to the central axis C in the BB' plane. ψ for C
The light beam is bent at an angle of 1 m and passes through the rear focal point of the imaging lens 9. However, let θ〈ψ. Among the laser beams emitted from the output end face of the index light light guide fiber 4, the laser beam that intersects with the light beam 11 is designated as J.
c, and the distance from the intersection p to the central axis C is h. Further, let Q be the foot of a perpendicular drawn from the point p to the central axis C, and let the distance from the exit end surface of the imaging lens 9 to the point Q be 1. If the inner wall surface of the body cavity is located at the intersection p of the light 1h and the laser beam 1o, the distance 1 is the distance from the tip surface of the length-measuring light guide 1 to the inner wall surface of the body cavity. Therefore, in this case, the distance corresponds to the length from the base point 0 to the 2nd scale on the scale section 13, and by determining the value of the distance, the length on the inner wall surface of the body cavity can be calculated using this value as a reference. This makes it possible to obtain the following.

By the way, as is clear from FIG. 8, h=i-ψ.

)1=2tano+γ (where γ is the distance from the central axis of the imaging lens 9 to the output end of the index light light guide fiber 4), so if 1 is deleted from both equations,
''-k. Here, since the values of γ and θ are known, and the value of ψ can be obtained by calculation or actual measurement, the value of h can be calculated from the above equation.

In this way, the value of h is calculated in advance, and when using this device under an endoscope, as shown in FIG. Then, the endoscope 2 may be operated so that the second graduation of the scale face projection image 24 and the index image 25 formed by the laser beam intersect. That is, it is sufficient to adjust the distance between the length measuring light guide 1 and the inner wall surface of the body cavity. Then, the length of two scales corresponds to h, and the length of one scale corresponds to -, so it is the same as placing a ruler on the lesion 23, and the length of the lesion 23 You can easily know the size of Then, the color tone of the lesion area 23 is adjusted to the scale face projection image 2.
4, and if it is difficult to clearly identify the scale face projected image 24, select an appropriate electrochromic functional thin film element from the color filter 22 and perform a switching operation. By coloring this, the color tone of the scale face projection image 24 can be changed and it can be clearly identified.

In the above explanation, the second scale of the scale section 13 was used as the reference, but any scale may be used as the reference. It's a good thing to have. However, ψ1〉θ
Furthermore, in order to reduce reading errors, it is desirable that the difference between ψn and θ be large.

Next, another embodiment of the present invention will be described based on FIGS. 10 to 13 of the accompanying drawings.

As shown in FIGS. 10 and 11, the index light light guide fiber 4' is a length measuring light that extends only to a part of the periphery of the scale projection light guide fiber 5, the scale plate 8, and the imaging lens 9. The laser beam emitted from the laser oscillator 14 in the light source box 6 is arranged in an arc shape along the inner peripheral surface of the guide 1, and the incident end face of the index light light guide fiber 4' has a direct incidence angle. θ
It is fixed to a suitable fixing member (not shown) so that the light is incident at a certain angle. Further, the scale projection light guide fiber 5, the scale plate 8, and the imaging lens 9 are located coaxially with each other, and the index light light guide fiber 4 is located on the inner peripheral surface of the length measurement light guide 1. It is fixedly disposed at a portion opposite to ' by a support member (not shown).

The other configurations are the same as those of the above-described embodiment, so the explanation will be omitted.

As is clear from FIG. 12, the value of h can be calculated in this example based on the same principle as the above-mentioned example, and thereby the lesion 23 on the inner wall surface of the patient's body cavity (see (see). Here, the difference between this embodiment and the previously described embodiment is that the light guide fiber 4' for the index light is arranged in an arc shape, so that the index image 25' is also arranged in an arc shape, as shown in FIG. This is the point projected onto the lesion 23 on the inner wall surface of the body cavity.

Therefore, if the endoscope 2 (see FIG. 1) is operated so that the arc-shaped index image 25' and the reference scale of the scale face projection image 24, for example, the second scale, intersect on the lesion 23,
The size of the lesion 23 can be easily determined in the same manner as in the previous embodiment.

Note that the index light light guide fiber 4' in this embodiment may be arranged not only in an arc shape but also in a straight line shape.

Furthermore, since the index light light guide fiber 4' is not disposed all around the imaging optical system 10,
There is no need to align the order of the strands of the index-use light guide fiber 4' on the incident side and the output side.

This embodiment has the advantage that the number of strands of the index light light guide fiber 4' can be reduced.

In the two embodiments described above, only the scale part 13 of the scale plate 8 is configured to allow light to pass therethrough, but on the contrary, only the scale part 13 may be configured to not allow light to pass therethrough. In addition, the shape of the scale portion 13 includes a plurality of straight scales 12 that are orthogonal to two coordinate axes 11a and 11b that are orthogonal to each other.
..., but as shown in FIG. 14, each scale 12' is a circle, and these are arranged on the scale plate 8'.
The scale portion 13' can also be formed by arranging the scales concentrically around the center of the scale. Even in this case, although it is not clear from FIG. 14, the intervals between the circles constituting each scale 12' are not necessarily equal, taking into account the distortion aberration of the imaging lens 9. Of course, even on this scale plate 8', only the scale part 13' can transmit light, or on the contrary,
Only the scale portion 13' can be disabled. moreover,
We have explained the case where a laser beam is used as the index light and a lamp light is used as the projection light, but if this relationship is reversed or the color tone is different to enable identification, both can be used. It is also possible to use a laser beam or lamp light. Of course, it is preferable to use a laser beam that oscillates in the visible range; in the case of an invisible laser beam, the area to be examined, such as a lesion, should be coated with a substance that will color when irradiated with the laser beam. Such measures must be taken.

As is clear from the above explanation, the following effects can be achieved according to the present invention.

First, since the length can be measured without contacting the test part existing in a body cavity or the like, it is most suitable for cases where the test part is not desirable to be stimulated, such as a diseased part.

Second, it is extremely accurate because the length is measured in the same condition as placing a ruler on the area to be examined. Sixthly, since there is no need to measure the distance from the imaging lens to the subject, it is ideal as an endoscope device, but from both equations for calculating h mentioned above, 1-112--- Since ψ−10 can be derived, the distance can also be calculated. Fourth, since the structure is simple, there are fewer failures and it can be supplied at low cost.

Fifth, there is no need for focusing, and the operation is extremely easy.

[Brief explanation of the drawing]

The figures show preferred embodiments of the present invention, with Fig. 1 being a schematic diagram showing the state in which it is used in an endoscope, and Fig. 2 showing the arrangement of the observation optical system and index light light guide fiber in the length measurement light guide. A schematic cross-sectional view showing the state, FIG. 3 is a schematic diagram of the tip surface of the length measurement light guide, FIG. 4 is a front view of the scale plate, and FIG. 5 is a schematic diagram of the entire device showing the inside of the light source box. Figure 6 is a schematic side view showing the fixed state of the light guide fiber for index light at the input end and the incident state of the laser beam, Figure 7 is a schematic diagram showing the input end of the light guide fiber for index light, and Figure 8 9 is an explanatory diagram showing the principle of length measurement, FIG. 9 is a schematic diagram showing a projection state from the lesion area, and FIG. 10 is a schematic diagram of the entire device in another embodiment of the arrangement state of the light guide fiber for the index light. , FIG. 11 is a schematic diagram of the tip surface of the length measurement light guide, FIG. 12 is an explanatory diagram showing the principle of length measurement, FIG. 13 is a schematic diagram showing the state of projection onto a lesion, and FIG. FIG. 7 is a front view of a scale plate showing another example of the scale portion. 1... Length measurement light guide 2... Endoscope 3...
Forceps channel 4, 4'...Light guide fiber for index light 5...Light guide fiber for scale projection 6...Light source box 8, 8'...
- Scale plate 9...Imaging lens 1o...Imaging optical system 11a, li, . . . Coordinate axes 12.12'-, . Scale 13.13'...Scale part 14...
Laser oscillator 18...Light source lamp 23...Lession area 24/Self scale projection image 25, 25'...
Index image Figure 2 Figure 3 Figure 1. A l't Procedural amendment (voluntary) Director of the Patent Office Kazuo Wakasugi1, Indication of the case, Patent Application No. 133295 of 1982, Name of the invention, Length measuring device for endoscope3, Person making the amendment Relationship to the incident Patent applicant address 2-43-2 Hatagaya, Shibuya-ku, Tokyo Name (0
37) Olympus Optical Industry Co., Ltd. Representative Shigeru Kitamura 4, Agent 103 Address 3-6 Honseki-cho, Nihonbashi, Chuo-ku, Tokyo (3) Brief description of drawings in the specification (4) Drawing 6, Contents of the amendment (1) As shown in the attached sheet, (2) In the specification: (a) On page 13, line 18, the phrase "angular depth of field of the image" is corrected to "depth of field of the image." (b) On page 14, from line 16 to line 17, the phrase ``out of the laser beam, . Among them, the ray that intersects with the ray 1m above (
lc', toshi,'' he corrected. (c) On page 15, line 1, "laser beam Ic J" is corrected to "intersecting ray 1c j.") On page 16, line 1, "index image 25 by laser beam" is changed to " The outer edge of the index image 25 is corrected. (e) From page 17, line 3 to page 19, line 5, delete the statement ``Next, there is an advantage.'' (v) On page 19, line 6, the phrase "the two embodiments described above" is corrected to "the embodiment described above." (g) On page 19, line 12, correct "Figure 14" to "Figure 10." V → On page 19, from line 15 to line 16, "Figure 14" is corrected to "Figure 10." (3) In the specification, (a) Delete from page 21, line 20 to page 22, line 5. (b) On page 22, line 5, "Figure 14" is corrected to "Figure 10." (c) On page 22, line 8, correct "r4, 4'..." to "4...". ) On page 22, line 17, "25.25'..." is corrected to "25...". (4) In the drawings, (a) Figure 9 is corrected as shown in the attached sheet. 00) Delete FIGS. 10, 11, 12, and 13. (c) Correct the 10th same pressure in Figure 14 as shown in the attached sheet. Above 2, Claim 1: A length measurement light guide formed to be inserted into a forceps channel of an endoscope, a light guide fiber for projecting a scale, and a scale portion, the scale portion or a portion other than the scale portion. It consists of a scale member through which light passes through only one of the two, and an imaging lens having an effective diameter of 5πm or less and a rear focal point located very close to the rear end surface of the lens, and arranged coaxially within the length measurement light guide. On the other hand, the input end of the scale projection light guide fiber is connected to an imaging optical system located outside the length measurement light guide, and the input end of the scale projection light guide fiber of this imaging optical system. a light source for supplying an index light, and a light guide for index light disposed within the length measurement light guide so as to be located around the imaging optical system, while an input end is located outside the length measurement light guide. A length measuring device for an endoscope, comprising a fiber and a light source for supplying light to the input end of the index light light guide fiber. 2. The length measuring device for an endoscope according to claim 1, wherein the light guide fiber for the index light is disposed coaxially so as to cover the entire periphery of the imaging optical system. The scale part of the main scale member is composed of two coordinate axes orthogonal to each other at the center of the scale member, and a plurality of straight scale marks arranged perpendicularly to these coordinate axes, and the intervals between the scales are fixed. 2. The length measuring device for an endoscope according to claim 1, wherein the length measuring device is arranged at unequal intervals in consideration of distortion aberration of the image lens. 4. The length measuring device for an endoscope according to claim 1, wherein the scale portion of the scale member is formed of a circle centered on the center of the scale member. L The endoscope according to claim 1, characterized in that the scale portion is composed of a plurality of concentric circles, and the intervals between each day of the scale are unequal intervals in consideration of distortion aberration of the imaging lens. Length measuring device. 1. The length measuring device for an endoscope according to claim 1, wherein the scale member is configured such that light passes through only the scale portion. L. The length measuring device for an endoscope according to claim 1, wherein the scale member is configured such that light passes through only a portion outside the scale member. 1. The length measuring device for an endoscope according to claim 1, wherein the light from the light source is passed through a color filter and then supplied to the input end of a light guide fiber for projecting a scale. Main Claim 1, characterized in that the color filter is composed of an electrochromic functional thin film element.
Endoscope length measuring device described in Section 2. The endoscope according to claim 1, characterized in that electrochromic functional thin film elements that develop different colors are stacked in multiple layers, and these electrochromic functional thin film elements are selectively colored. Length measuring device. 9 4 11 (enter 2 ge mo 8' Procedural amendment form C) November 10, 1980 Kazuo Wakasugi, Commissioner of the Patent Office 1, Indication of the case 1982 Patent Application No. 163295 2, Invention Name Endoscope Length Measuring Device 3 Person making the correction Relationship with 1 case Patent applicant 4 Agent 103 8 Contents of the amendment Figures 10 and 11 will be deleted as shown in the attached sheet. 183-

Claims (1)

[Scope of Claims] 1. A length measurement light guide formed so as to be inserted into a forceps channel of an endoscope, a light guide eyeper for projecting a scale, and a scale portion, including the scale portion or a portion other than the scale portion. One of them consists of a scale member through which light passes through only one, and an imaging lens with an effective diameter of 5 mm or less and a rear focal point located very close to the rear end surface of the lens, and in this order, the length measuring light is coaxially connected to the imaging lens. The input end of the scale projection light guide fiber is disposed within the guide, and the input end of the scale projection light guide fiber is connected to an imaging optical system located outside the length measurement light guide, and of the scale projection light guide fiber of this imaging optical system. a light source for supplying light to an input end; and an indicator disposed within the length measurement light guide so as to be located around the imaging optical system, while the input end is located outside the length measurement light guide. A length measuring device for an endoscope, comprising a light guide fiber for light and a light source for supplying light to an input end of the light guide fiber for index light. 2. The length measuring device for an endoscope according to claim 1, wherein the light guide fiber for the index light is disposed coaxially so as to cover the entire periphery of the imaging optical system. 6. The length measuring device for an endoscope according to claim 1, wherein the light guide fiber for the index light is arranged so as to extend only to a part of the periphery of the imaging optical system. 4. The scale part of the scale member is composed of two coordinate axes orthogonal to each other at the center of the scale member, and a plurality of straight scale marks arranged perpendicularly to these coordinate axes, and the intervals between the scales are 2. The length measuring device for an endoscope according to claim 1, wherein the length measuring device is arranged at unequal intervals in consideration of distortion aberration of the imaging lens. 5. The length measuring device for an endoscope according to claim 1, wherein the scale portion of the scale member is formed of a circle centered on the center of the scale member. 6. The endoscope according to claim 5, characterized in that the scale portion is constituted by a plurality of concentric circles, and the scales are irregularly spaced in consideration of distortion aberration of the imaging lens. Mirror length measuring device. The length measuring device for an endoscope according to claim 1, wherein the scale member is configured such that light passes through only the scale portion. 8. The length measuring device for an endoscope according to claim 1, wherein the scale member is configured such that light passes through only the portion other than the scale portion. 9. The length measuring device for an endoscope according to claim 1, wherein the light from the light source is passed through a filter and then supplied to the input end of a light guide fiber for projecting a scale. 1Q The length measuring device for an endoscope according to claim 9, wherein the color filter is constituted by an electrochromic functional thin film element. 11. An endoscope according to claim 10, characterized in that electrochromic functional thin film elements that develop different colors are stacked in multiple layers, and these electrochromic functional thin film elements are optionally selected to develop colors. Length measuring device.