JPH09294708A - Endoscope capable of measuring distance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a distance from an endoscope tip to an observation part in non-contact and without using a forceps channel by detecting measurement light and reference light made to interfere in an interference optical system and computing the distance from the tip of an introduction tube to the part based on the output. SOLUTION: This endoscope is provided with an illumination light source 10, a condensing lens 11 and a light guide 12 composed of an optical fiber. The light guide 12 is housed inside the introduction tube 14 to be introduced inside a living body 13 and the tip part of a polarization plane maintaining fiber 15 is housed inside the introduction tube 14. The rear end of the polarization plane maintaining fiber 15 is put out of the introduction tube 14 and a measurement light irradiation system for making the measurement light L2 be incident from the rear end to the inside of the polarization plane maintaining fiber 15 is provided on the outside of the introduction tube 14. The interference optical system 100 for making the measurement light L2 and the reference light L3 interfere is disposed at the outside of the introduction tube 14. Also, a photodetector 43 for detecting the intensity of the measurement light L2 and the reference light L3 synthesized by a beam splitter 41 is provided and connected to an arithmetic circuit 44.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endoscope for observing the inside of a living body, and more particularly to an endoscope capable of measuring the distance from the endoscope tip to the observation site.

[0002]

2. Description of the Related Art Conventionally, an endoscope has been widely used for observing the inside of a living body or for treating while observing the inside of a living body. When using this endoscope, the distance from the tip of the endoscope to the observation site must be accurately determined for treatment operations and to prevent the endoscope from hitting the observation site in the living body. There is a demand to measure.

As one of the endoscopes capable of measuring this distance, for example, as shown in Japanese Patent Publication No. 61-20488, a probe inserted into a forceps channel of an introduction tube of the endoscope is used as an observation part. To measure the distance based on the amount of extension when the tracing stylus comes into contact with the observation site.

Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 62-49208, there is known a device for optically measuring a distance by contacting an observation site by using two measuring light beams. There is.

[0005]

However, in an endoscope for measuring a distance using a probe as described above, there is a risk that the probe may damage an observation site in a living body. The problem is that the forceps channel becomes unusable.

On the other hand, in a conventional endoscope that measures the distance optically, it is possible to prevent the observation part from being damaged. However, in order to incorporate a large-scale light beam irradiation system and a measurement optical system, the introduction tube of the endoscope is required. The problem that the diameter becomes large and the usability deteriorates is recognized.

The present invention has been made in view of the above circumstances, and it is possible to measure the distance from the distal end of an endoscope to an observation site without contacting the site and without using forceps channels. Moreover, it is an object of the present invention to provide an endoscope in which the diameter of the introduction tube does not become particularly thick for distance measurement.

[0008]

A distance-measurable endoscope according to the present invention incorporates an optical fiber forming a part of an interferometer into an introduction tube introduced into a living body, and the endoscope is used by the interferometer. The distance from the tip to the observation site is measured, and more specifically, as described in claim 1, in the endoscope having the introduction tube as described above, the tip portion is disposed inside the introduction tube. The rear end portion is an optical fiber disposed outside the introduction tube, and a measurement light irradiation system that irradiates the optical fiber with the measurement light from the rear end and emits it from the front end, and irradiates the site inside the living body, An interference optical system arranged outside of the above-mentioned introducing tube that interferes with the reference light by returning the light reflected by the part to the inside of the optical fiber and then emitted from the rear end, and the measurement light and the reference light interfered by this interference optical system. Photo detector to detect And it is characterized in that a calculating means for calculating a distance from the tip of the inlet tube to the site based on the output of the photodetector consists of an interferometer is provided.

As the above-mentioned interference optical system, it is preferable that the optical system according to claim 2
It is desirable to use a heterodyne interferometric optics as described in.

In the endoscope of the present invention, the third aspect of the present invention is provided.
As described in (1), it is desirable to provide a means for capturing an image of a part inside the living body, and an image display means for displaying the image captured by the imaging means and the information indicating the distance calculated by the computing means.

Further, in the endoscope of the present invention, as described in claim 4, it is desirable to provide means for issuing an alarm when the distance calculated by the calculating means is smaller than a predetermined distance.

On the other hand, as the measuring light irradiation system in the endoscope of the present invention, it is desirable to use one that emits near infrared light as the measuring light.

[0013]

EFFECT OF THE INVENTION The distance-measurable endoscope of the present invention is constructed so that the distance can be measured by an interferometer in which an optical fiber is incorporated into an introduction tube introduced into the living body. The distance from the distal end of the endoscope to the observation site can be measured by contacting the observation site.

Further, as the optical fiber for propagating the measuring light, a sufficiently thin one can be used, so that the optical fiber can be arranged in the endoscope introducing tube without using a forceps channel, and this optical fiber is also used. The diameter of the introduction tube does not become particularly large due to the provision of.

Generally, it is necessary to dispose an optical system for condensing the measurement light on the tip side of the optical fiber, but such an optical system can basically be constructed by one lens. Therefore, even if this optical system is provided, the diameter of the introduction tube does not become particularly large.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a side shape of an endoscope according to a first embodiment of the present invention.

This endoscope is provided with an illumination light source 10 which emits illumination light L1 which is white light, a condenser lens 11 which condenses this illumination light L1, and an arrangement in which the condensed illumination light L1 is incident. And a light guide 12 formed of an optical fiber. The light guide 12 is housed in a flexible introduction tube 14 introduced into the living body 13. In addition, the tip of the polarization-maintaining fiber 15 is housed in the introduction tube 14.

An imaging lens 16 is provided at a position facing the tip of the polarization-maintaining fiber 15 (the left end in FIG. 1). In addition, this imaging lens 16 and polarization maintaining fiber 15
A condenser lens 17, a λ / 4 plate 18 and a dichroic mirror 19 are arranged in this order from the polarization preserving fiber 15 side. A solid-state image pickup device 20 such as a CCD image pickup device is provided at a position where the light reflected by the dichroic mirror 19 is received. This solid-state imaging device 20 is connected to image display means 21.

The rear end of the polarization-maintaining fiber 15 is brought out of the introducing tube 14, and a measurement light irradiation system for injecting the measurement light L2 into the polarization-maintaining fiber 15 from the rear end is also introduced. It is provided outside the tube 14.

This measuring light irradiation system uses linearly polarized light L4.
A light source 22 that emits light, a collimator lens 23 that parallelizes the light L4, a beam splitter 24 that splits the parallel light L4 into a measurement light L2 and a reference light L3, and a frequency of the measurement light L2. An AOM (acousto-optic light modulator) 25 as a frequency shifter for shifting a predetermined amount, a mirror 26 for changing the optical path of the measurement light L2 by 90 °, a λ / 2 plate 27, a polarization beam splitter 28, a mirror 29, and a collector. The measurement light L2 is condensed by the condenser lens 30 so as to be converged on the rear end face of the polarization-maintaining fiber 15, and enters the fiber 15.

Outside the introduction tube 14, the measurement light L2 and the reference light L
An interference optical system 100 for interfering with 3 is provided. The interference optical system 100 includes, in addition to the beam splitter 24 and the polarization beam splitter 28, an AOM 31 as a frequency shifter for shifting the frequency of the reference light L3 from the beam splitter 24 by a predetermined amount, and an optical path of the reference light L3 by 90 °. Changing mirror 32, λ / 2 plate 33, and polarization beam splitter
34, a condenser lens 35, a polarization-maintaining fiber 36 arranged so that the reference light L3 condensed by the condenser lens 35 enters, and a reference light emitted from the tip of the polarization-maintaining fiber 36. A condenser lens 37 for collimating L3,
The λ / 4 plate 38, the movable mirror 39 that reflects the reference light L3 that has passed through the λ / 4 plate 38, the mirror moving means 40 that moves the movable mirror 39 in the left-right direction in the drawing, and as will be described later. And a beam splitter 41 that multiplexes the measurement light L2 and the reference light L3 that are incident.

The drive of the mirror moving means 40 is controlled by the drive control circuit 42. The drive control circuit 42 inputs a position signal S3 indicating the position of the movable mirror 39 to the arithmetic circuit 44. Further, a photodetector 43 for detecting the intensity of the measurement light L2 and the reference light L3 combined by the beam splitter 41 is provided, and this photodetector 43 is also connected to the arithmetic circuit.

The operation of the endoscope having the above structure will be described below. When observing the site 45 inside the living body 13, the introduction tube 14 of the endoscope is introduced into the living body 13, and the illumination light L1 is emitted from the light guide 12 to the observation site 45. Imaging lens 16
Forms an image of the observation region 45 by the illumination light L1 on the solid-state image sensor 20 via the dichroic mirror 19. The solid-state image pickup device 20 picks up this image and inputs the image signal S1 indicating it to the image display means 21.

The image display means 21 displays an image based on the image signal S1. Therefore, the operator or assistant observes the displayed image to check the state of the observation site 45,
The positional relationship between the introduction tube 14 and the observation site 45 can be confirmed.

Next, the point of measuring the distance between the observation site 45 and the distal end of the endoscope, that is, the distal end of the introduction tube 14 will be described. The measurement light L2 obtained by splitting the light L4 by the beam splitter 24 has its linear polarization direction adjusted by the λ / 2 plate 27, passes through the polarization beam splitter 28, and is condensed by the condenser lens 30 to be polarized. It is incident on the wavefront preserving fiber 15. The measurement light L2 emitted from the tip of the polarization-maintaining fiber 15 passes through the condenser lens 17 to be parallel light, and is then converted from linearly polarized light to elliptically polarized light by the λ / 4 plate 18 and then by the imaging lens 16. It squeezes and irradiates one point on the observation site 45.

The measuring light L2 reflected by the observation part 45 is transmitted through the dichroic mirror 19, is condensed by the condenser lens 17 and is incident on the polarization-preserving fiber 15, propagates through the polarization-preserving fiber 15, and is transmitted to the living body 13 Guided outside. The measurement light L2 is reflected at the observation site 45, the direction of its elliptically polarized light is inverted, and then passes through the λ / 4 plate 18, so that it travels from the polarization-preserving fiber 15 to the observation site 45 side. The direction of linearly polarized light is rotated by 90 °.

The measurement light L2 emitted from the rear end of the polarization plane preserving fiber 15 is collimated by the condenser lens 30 and reflected by the polarization beam splitter 28 because the direction of the linearly polarized light is rotated by 90 ° as described above. , Beam splitter 41
Incident on.

On the other hand, the reference light L3 obtained by splitting the light L4 by the beam splitter 24 is reflected by the mirror 32, and then the direction of the linearly polarized light is adjusted by the λ / 2 plate 33, and transmitted through the polarization beam splitter 34. Then, the light is condensed by the condenser lens 35 and enters the polarization plane preserving fiber 36. The reference light L3 emitted from the end of the polarization plane preserving fiber 36 passes through the condenser lens 37, is converted into parallel light, is converted from linearly polarized light into elliptically polarized light by the λ / 4 plate 38, and is incident on the movable mirror 39. I do.

The reference light L3 is reflected by this movable mirror 39,
It returns to the original optical path and enters the polarization beam splitter 34.
The reference light L3 is reflected by the movable mirror 39 so that the direction of its elliptically polarized light is inverted, and then passes through the λ / 4 plate 38, so that the reference light L3 travels from the polarization maintaining fiber 36 to the movable mirror 39 side. The direction of linearly polarized light is rotated by 90 °. Therefore, the reference light L3 is reflected by the polarization beam splitter 34, is incident on the beam splitter 41, and enters the measurement light L
Combined with 2.

Since the measurement light L2 and the reference light L3 are shifted to different frequencies by AOM25 and AOM31, respectively, when they are combined, interference (heterodyne interference) causes a difference in frequency between the two frequencies. A beat component is generated. The output signal S2 of the photodetector 43 that detects the combined measurement light L2 and reference light L3 is input to the arithmetic circuit.

The arithmetic circuit 44 outputs the output signal S2 of the photodetector 43.
Is passed through a bandpass filter or the like to extract the beat component, and the distance between the tip of the introduction tube 14 and the observation site 45 is calculated based on the beat component.

That is, the optical path length of the measuring light L2 from the beam splitter 24 to the beam splitter 41 via the observation part 45 and the optical path length of the reference light L3 from the beam splitter 24 to the beam splitter 41 via the movable mirror 39. The phase of the beat component changes in accordance with the difference of, for example, when there is no optical path length difference, the beat component shows a sharp peak. Then, the arithmetic circuit 44 can calculate the optical path length of the measurement light L2 based on the position of the movable mirror 39 when this peak appears (as indicated by the position signal S3),
Consequently, the distance from the tip of the introduction tube 14 to the observation site 45 can be obtained.

The arithmetic circuit 44 inputs the signal S4 indicating the distance thus obtained to the image display means 21 and displays the information indicating the distance. This display is shown in FIG.
An image F of the observation site 45 captured by the aforementioned solid-state imaging device 20;
This is performed by synthesizing the distance information D and the mark M indicating the distance measurement position. Note that the distance measurement position is a position where the polarization-maintaining fiber 15 faces, and this can be associated with the imaging range such that it is the center of the imaging range by the solid-state imaging device 20, so the mark M is It may be displayed at a fixed position according to the correspondence.

Next, an endoscope according to a second embodiment of the present invention will be described with reference to FIG. In addition, in FIG. 3, the same elements as those in FIG.
A duplicate description of them is omitted (the same applies hereinafter).

The endoscope according to the second embodiment also uses the heterodyne interference optical system to measure the distance as in the first embodiment, but the first embodiment uses OCDR (Opti
In contrast to the technique called calCoherence Domain Reflectometry), this second embodiment is OF
This is based on a technique called DR (Optical Frequency Domain Reflectometry).

That is, in this second embodiment,
As the light source 50 that emits the linearly polarized light L4, a semiconductor laser capable of sweeping the oscillation frequency is used. The oscillation frequency of the light source 50 composed of the semiconductor laser is swept by continuously changing the value of the injection current supplied from the laser drive circuit 51, for example. The laser drive circuit 51 inputs a signal S5 indicating the oscillation frequency to the arithmetic circuit 52.

The above-mentioned light L4 enters the polarization-maintaining fiber 15 and exits from the tip thereof, and a part of it is the measurement light L2.
As a result, one point on the observation site 45 is irradiated. This measuring light L2
Is reflected by the observation site 45 and re-enters the polarization-maintaining fiber 15. Further, a part of the light L4 is reflected by, for example, the end face of the dichroic mirror 19 and re-enters the polarization maintaining fiber 15 as the reference light L3.

The measurement light L2 and the reference light L3 are reflected by the polarization beam splitter 28 and enter the photodetector 43. In this case as well, the two lights interfere with each other, and the resulting beat component is incident on the photodetector 43. To be detected. At that time, when the frequency of the light L4 reaches a certain specific frequency according to the optical path length difference between the measurement light L2 and the reference light L3, the beat component shows a sharp peak. Therefore, the arithmetic circuit 52 can calculate the optical path length of the measurement light L2 based on the frequency of the light L4 when the peak appears (as indicated by the signal S5), and eventually from the tip of the introduction tube 14. The distance to the observation site 45 can be obtained. The display of the distance thus obtained may be performed in the same manner as in the first embodiment.

Next, an endoscope according to the third embodiment of the present invention will be described with reference to FIG. The endoscope shown in FIG. 4 is different from the endoscope shown in FIG. 1 only in the portion surrounded by a broken line. That is, the mirror shown in FIG.
A dichroic mirror 60 is provided instead of 29, and the excitation light L in the blue region is directed toward the dichroic mirror 60.
An excitation light source 61 that emits 5 is provided. A λ / 2 plate 62 for polarization plane adjustment and a dichroic mirror 63 are arranged in the optical path of the pumping light L5.

Further, as will be described later, a condenser lens 64 for condensing the fluorescent light L6, an excitation light cut filter 65, a fluorescent light, and a fluorescent light L6 are incident on the dichroic mirror 63 and reflected by the fluorescent light L6. Photodetector 66 for detecting L6
And are arranged.

In this endoscope, the imaging of the observation region 45 and the measurement of the distance from the tip of the introducing tube 14 to the observation region 45 are performed in the same manner as in the first embodiment. Furthermore, in this example, fluorescence diagnosis for tumor identification can be performed. That is, the observation site 45 has previously absorbed a photosensitizer having a tumor affinity and emitting fluorescence when excited by light. Then, the observation part 45 is irradiated with the excitation light L5 propagated through the polarization-maintaining fiber 15. The excitation light L5 is focused by the image forming lens 16 and is observed by the observation site 45.
Irradiate one point above.

At the observation site 45 irradiated with the excitation light L5, fluorescence L6 is emitted from the photosensitizer. The fluorescence L6 is condensed by the imaging lens 16, passes through the dichroic mirror 19, and the polarization plane preserving fiber 15 is transmitted.
Incident on the living body 13 and propagates through the polarization-maintaining fiber 15.
Guided outside.

The fluorescence L6 emitted from the polarization-preserving fiber 41 is reflected by the dichroic mirror 63, and the condenser lens 64 is used.
The light is collected by and is received by the photodetector 66. The excitation light L5 reflected by the observation site 45 and directed to the photodetector 66 is cut by the excitation light cut filter 65. The photodetector 66 outputs a fluorescence detection signal S6 indicating the intensity of the fluorescence L6, and this fluorescence detection signal S6 is, for example, the image display means 21.
Is input to

Here, since the photosensitizer has a tumor affinity, it can be considered that the fluorescence L6 basically originates from the tumor portion when the fluorescence detection signal S6 exceeds a predetermined level. Since the detection location of the fluorescence L6 in the observation region 45 and the normal image capturing range of the solid-state image sensor 20 can correspond to each other, for example, the center point of the normal image capturing range is the fluorescence L
6, and the center point of the normal image pickup range is aligned with the center of the screen of the image display means 21, and a mark is displayed at the center of the screen when the fluorescence detection signal S6 exceeds a predetermined level. By doing so, it is possible to determine that the part of the normal image that overlaps the mark is the tumorous part.

Further, regardless of such display, an alarm sound is emitted when the fluorescence detection signal S6 exceeds a predetermined level, and when the alarm sound is emitted, the image display means.
It is also possible to determine that the location of the normal image in the center of the screen of 21 is the tumorous part.

As the measuring light L2, it is desirable to use near-infrared light which is relatively little absorbed in the living body. By doing so, a high light amount of the measurement light L2 returning to the interference optical system is secured, and the beat component detection signal has a high S / N.

[Brief description of drawings]

FIG. 1 is a schematic side view showing an endoscope which is a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a distance display state in the endoscope of FIG. 1;

FIG. 3 is a schematic side view showing an endoscope which is a second embodiment of the present invention.

FIG. 4 is a schematic side view showing an endoscope which is a third embodiment of the present invention.

[Explanation of symbols]

 10 Illumination light source 11 Condenser lens 12 Light guide 13 Living body 14 Endoscope introduction tube 15 Polarization preserving fiber 16 Imaging lens 17 Condenser lens 18 λ / 4 plate 19 Dichroic mirror 20 Solid-state image sensor 21 Image display means 22 Interference Light source of the meter 23 Collimator lens 24 Beam splitter 25 AOM (frequency shifter) 27 λ / 2 plate 28 Polarization beam splitter 30 Condensing lens 31 AOM (frequency shifter) 33 λ / 2 plate 34 Polarizing beam splitter 35 Condenser lens 36 Polarization Wavefront preserving fiber 37 Condenser lens 38 λ / 4 plate 39 Movable mirror 40 Mirror moving means 41 Beam splitter 42 Drive control circuit 43 Photodetector 44 Arithmetic circuit 50 Interferometer light source 51 Laser drive circuit 52 Arithmetic circuit 60 Dichroic mirror 61 Excitation Light source 62 λ / 2 plate 63 Dichroic mirror 64 Condenser lens 65 Excitation light cut filter 66 Photodetector 100 Interferometric optics L2 measurement light L3 reference light

Claims (5)

[Claims] 1. An endoscope having an introduction tube to be introduced into a living body, wherein an optical fiber having a tip portion arranged inside the introduction tube and a rear end portion arranged outside the introduction tube, A measurement light irradiation system that causes measurement light to be incident on the optical fiber from the rear end and emitted from the front end, and irradiates a site inside the living body, and measurement light emitted from the rear end that is reflected at the site and returned to the optical fiber. An interference optical system arranged outside the introducing tube, a photodetector for detecting the measurement light and the reference light interfered by the interference optical system, and an interference optical system based on the output of the photodetector. An endoscope capable of measuring a distance, characterized in that an interferometer comprising a calculation means for calculating a distance from the tip of the introduction tube to the part is provided. 2. The distance-measurable fluorescence endoscope according to claim 1, wherein a heterodyne interference optical system is used as the interference optical system. 3. A means for picking up an image of a part inside the living body, and an image display means for displaying the image picked up by the image pick-up means and the information indicating the distance calculated by the calculation means. The endoscope capable of measuring distance according to claim 1 or 2. 4. The distance-measurable endoscope according to claim 1, further comprising means for issuing an alarm when the distance calculated by the calculation means is smaller than a predetermined distance. mirror. 5. The measuring light irradiation system emits near infrared light as the measuring light.
4. An endoscope capable of measuring a distance according to any one of 4 to 4.