JPH10337272A - In vivo distance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in vivo distance measuring device which can measure the distance to a part in vivo without making contact with that part and which has a fine and easy-to-use measuring part. SOLUTION: An in vivo distance measuring device includes an optical fiber 15 whose front end is placed within a measuring element main body 8 introduced into a living body 13 and whose rear end is placed outside the measuring element main body 8; a measuring beam application system which comprises a light source 22 and the like, causing a measuring beam L2 to impinge on the optical fiber 15 from the rear end and emit from the front end to illuminate a part 45 inside the living body; an interference optical system 100 placed outside the measuring element main body 8, whereby the measuring beam L2 emitted from the rear end after being reflected by the part 45 and returned into the optical fiber 15 is made to interfere with a reference beam L3; and a photodetector 43 detecting the measuring beam L2 and the reference beam L3 which have interfered with each other. An interferometer with a computing means 44 computing the distance from the end of the measuring element main body 8 to the part 45 according to outputs of the photodetector 43 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a distance to a predetermined portion in a living body, for example, being incorporated in an endoscope for observing the inside of the living body.

[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 also known a method in which a distance is optically measured in a non-contact manner with an observation site by using two measurement light beams. I have.

[0005]

However, in an endoscope for measuring the distance by extending the tracing stylus as described above, there is a danger that the tracing stylus may damage an observation site in a living body.

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.

[0007] The present invention has been made in view of the above circumstances, and can measure the distance to a site in a living body without contacting the site. It is an object of the present invention to provide an in-vivo distance measuring device that is easy to use.

[0008]

According to the present invention, there is provided an in-vivo distance measuring apparatus comprising: a probe main body which can be inserted into a living body; a distal end disposed inside the probe main body; An optical fiber disposed outside the main body, a measurement light irradiation system that causes measurement light to enter the optical fiber from the rear end and emit from the front end, and irradiates a part inside a living body; and the optical fiber reflected at the part. And an interference optical system disposed outside the tracing stylus main body for causing the measurement light emitted from the rear end to interfere with the reference light, and a light for detecting the measurement light and the reference light that interfered with the interference optical system. And a calculating means for calculating a distance from the tip of the tracing stylus main body to the site based on an output of the photodetector.

It is desirable that a heterodyne interference optical system be used as the above-mentioned interference optical system.

It is desirable that the measurement light irradiation system be one that emits near-infrared light as measurement light.

Further, it is desirable that the in-vivo distance measuring device is provided with a means for issuing an alarm when the distance calculated by the calculating means is smaller than a predetermined distance.

[0012]

The in-vivo distance measuring apparatus according to the present invention is configured to measure the distance by an interferometer in which an optical fiber is incorporated in a main body of a measuring element introduced into a living body. The distance from the child main body to the observation site can be measured without contacting the observation site.

The in-vivo distance measuring apparatus having the above-described configuration can be inserted into a forceps hole of an introduction tube of an endoscope and integrated with the introduction tube. Can be used in combination with

In addition, as an optical fiber that is incorporated in the main body of the probe and propagates the measuring light, a sufficiently thin one can be used. Therefore, this in-vivo distance measuring apparatus has a thin measuring section and is easy to use. Also, a minute distance in a small hole of a living body or the like can be measured.

In general, it is necessary to dispose an optical system for condensing measurement light at the tip side of the optical fiber. Such an optical system can be basically constituted by one lens. Therefore, even if this optical system is provided, the diameter of the tracing stylus main body does not become particularly large.

If near-infrared light, which has relatively little absorption in a living body, is used as the measurement light, a large amount of measurement light returning to the interference optical system is ensured, and the measurement light and the interference caused by the interference optical system are secured. The beat component detection signal of the reference light has a high S / N.

Further, in this in-vivo distance measuring apparatus, if a means for issuing an alarm is provided when the distance calculated by the calculating means is smaller than the predetermined distance, the measuring element may damage an observation site in the living body. Is prevented beforehand.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an endoscope equipped with an in-vivo distance measuring device according to a first embodiment of the present invention.

This endoscope is provided with an illumination light source 10 for emitting illumination light L1 which is white light, a condenser lens 11 for condensing the illumination light L1, and an arrangement so that the collected illumination light L1 enters. And a light guide 12 made of an optical fiber. The light guide 12 is housed in a flexible introduction tube 14 introduced into the living body 13.

An imaging lens 16 is provided at the tip of the introduction tube 14, and a prism 19 is provided at a position facing the imaging lens 16 from the inside of the introduction tube 14. At a position where the light reflected by the prism 19 is received, a solid-state imaging device 20 such as a CCD imaging device is provided. This solid-state imaging device 20 is connected to image display means 21.

The introduction tube 14 is provided with a forceps hole 9 as in a normal endoscope. A tubular measuring element main body 8 is inserted through the forceps hole 9 so that it can be integrated with the introduction tube 14. A substantially central portion of the probe body 8 is formed to have flexibility, and a thin polarization preserving fiber 15 is disposed in that portion. A converging lens 17 and a λ / 4 plate 18 are arranged inside the tracing stylus main body 8 from the polarization plane preserving fiber 15 side on the tip side (left end side in the figure) of the portion where the polarization plane preserving fiber 15 is disposed. Have been. On the other hand, a condensing lens 30 is arranged in the tracing stylus main body 8 at the rear end side (right end side in the figure) of the portion where the polarization maintaining fiber 15 is arranged.

The rear end of the tracing stylus main body 8 extends out of the introduction tube 14, and a measurement light irradiating system for allowing the measurement light L2 to enter the polarization plane preserving fiber 15 from this rear end is also provided by the introduction tube.
It is provided outside of 14.

The above-mentioned measuring light irradiating system comprises a linearly polarized light L4
, A collimator lens 23 for converting the light L4 into parallel light, a beam splitter 24 for splitting 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 by a predetermined amount, a mirror 26 for changing the optical path of the measurement light L2 by 90 °, a λ / 2 plate 27, a polarizing beam splitter 28, and a mirror 29 Has been
The measurement light L2 is condensed by the condenser lens 30 of the tracing stylus main body 8 so as to converge on the rear end face of the polarization plane preserving fiber 15, and is incident on the fiber 15.

An interference optical system 100 for causing the measurement light L2 and the reference light L3 to interfere with each other is provided outside the tracing stylus body 8. 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 of 90 °. A mirror 32 for changing, a λ / 2 plate 33, a polarizing beam splitter 34, a condenser lens 35, and a polarization preserving fiber 36 arranged so that the reference light L3 condensed by the condenser lens 35 enters. And this polarization preserving fiber 36
, A λ / 4 plate 38, a movable mirror 39 for reflecting the reference light L3 passing through the λ / 4 plate 38, and a movable mirror 39
Are moved in the left-right direction in the figure, and a beam splitter 41 for multiplexing the incident measuring light L2 and reference light L3 as described later.

The driving of the mirror moving means 40 is controlled by a 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 will be described below. When observing the site 45 inside the living body 13, the introduction tube of the endoscope is used.
14 is introduced into the living body 13 and the illumination light L
1 is applied to the observation site 45. The imaging lens 16 forms an image of the observation site 45 by the illumination light L1 on the solid-state imaging device 20 via the prism 19. The solid-state imaging device 20 captures this image, and displays an image signal S1 indicating the image on an image display unit.
Enter 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, a description will be given of how the distance between the distal end of the tracing stylus body 8 and the observation site 45 is measured by the in-vivo distance measuring apparatus according to the present invention. The measurement light L2 obtained by splitting the light L4 by the beam splitter 24 is applied to the λ / 2 plate 27.
As a result, the direction of the linearly polarized light is adjusted, transmitted through the polarization beam splitter 28, condensed by the condenser lens 30, and incident on the polarization plane preserving fiber 15. Polarization-maintaining fiber
The measurement light L2 emitted from the tip of 15 passes through the condenser lens 17, is converted into parallel light, is converted from linearly polarized light into elliptically polarized light by the λ / 4 plate 18, and is focused by the imaging lens 16 for observation. One point on the part 45 is irradiated.

The measurement light L2 reflected by the observation site 45 is condensed by the condenser lens 17, enters the polarization-maintaining fiber 15, propagates through the polarization-maintaining fiber 15, and is guided out of the living body 13. Note that the direction of the elliptically polarized light of the measurement light L2 is inverted by being reflected at the observation site 45, and thereafter, λ / 4
By passing through the plate 18, the direction of the linearly polarized light is 9
Rotate 0 °.

The measurement light L2 emitted from the rear end of the polarization-maintaining fiber 15 is converted into parallel light by the condenser lens 30, and reflected by the polarization beam splitter 28 when 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 a mirror 32, then the direction of linearly polarized light is adjusted by a λ / 2 plate 33, and transmitted through a polarization beam splitter 34. Then, the light is condensed by the condenser lens 35 and enters the polarization 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 the movable mirror 39 moving as described above, returns to the original optical path, and enters the polarization beam splitter 34. The reference light L3 is transmitted to the movable mirror 39.
The direction of the elliptically polarized light is inverted by reflecting the light, and then the light passes through the λ / 4 plate 38, so that the direction of the linearly polarized light is rotated by 90 ° as compared with the case where the light goes from the polarization-maintaining fiber 36 to the movable mirror 39 side. I do. Therefore, the reference light L3 is reflected by the polarization beam splitter 34,
It is incident on 41 and multiplexed with the measurement light L2.

Since the measuring light L2 and the reference light L3 are shifted to different frequencies by the AOM 25 and the AOM 31, respectively, when they are multiplexed, interference (heterodyne interference) causes a difference between the two frequencies. A beat component occurs. 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 tracing stylus main body 8 and the observation site 45 is calculated based on the beat component.

That is, the optical path length of the measurement light L2 from the beam splitter 24 to the beam splitter 41 via the observation region 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 between the two components. For example, when there is no difference in the optical path length, 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 tracing stylus body 8 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 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. Distance measurement position is polarization-maintaining fiber 15
Are opposed to each other, and this is, for example, the solid-state imaging device 20.
Can be associated with the imaging range so as to be at the center of the imaging range, and the mark M may be displayed at a fixed position according to this correspondence.

The measurement light L2 can be reflected not only on the surface of the observation site 45 of the living body 13 but also inside a depth of about several mm from this surface. Therefore, the hardness of the observation site 45 is estimated by observing the ratio or attenuation between the detection signal intensity of the measurement light L2 reflected from the surface and the detection signal intensity of the measurement light L2 reflected inside the living body 13. Is also possible.

If a means for issuing an alarm is provided when the distance calculated by the arithmetic circuit 44 is smaller than a predetermined distance, it is possible to prevent the inside of the living body 13 from being damaged by the tracing stylus body 8 and the introducing tube 14. Is prevented.

Next, an in-vivo distance measuring apparatus according to a second embodiment of the present invention will be described with reference to FIG. Note that, in FIG. 3, the same elements as those in FIG. 1 are denoted by the same reference numerals, and redundant description thereof will be omitted.

The in-vivo distance measuring apparatus according to the second embodiment also measures a distance using a heterodyne interference optical system as in the first embodiment.
In contrast to a technique called a CDR (Optical Coherence Domain Reflectometry), the second embodiment is based on an OFDR (Optical Frequency Domain Reflector).
geometry).

That is, in the 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 light L4 enters the polarization plane preserving fiber 15 of the tracing stylus body 8 and exits from the tip thereof, and a part of the light L4 irradiates a point on the observation site 45 as the measuring light L2.
The measurement light L2 is reflected by the observation site 45 and reenters the polarization-maintaining fiber 15. Part of this light L4 is
For example, the light is reflected by the prism 19 and the like, and reenters 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, both lights interfere with each other, and the resulting beat component is transmitted to the photodetector 43. Is detected. At this time, when the optical path length difference between the measurement light L2 and the reference light L3 becomes an integral multiple of the wavelength of the light L4, the beat component shows a sharp peak. So the arithmetic circuit
52 can calculate the optical path length of the measuring light L2 based on the frequency of the light L4 when the peak appears (indicated by the signal S5), and thus can calculate the length from the tip of the measuring element main body 8 to the observation site 45. The distance can be determined. The display of the distance thus obtained may be performed in the same manner as in the first embodiment.

As the measurement light L2, it is desirable to use near-infrared light which has relatively little absorption in a 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 the drawings]

FIG. 1 is a schematic side view showing an endoscope provided with an in-vivo distance measuring device according to 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 provided with an in-vivo distance measuring device according to a second embodiment of the present invention.

[Explanation of symbols]

 8 Measuring element body 9 Forceps hole 10 Illuminating light source 11 Condensing lens 12 Light guide 13 Living body 14 Endoscope introduction tube 15 Polarization preserving fiber 16 Imaging lens 17 Condensing lens 18 λ / 4 plate 19 Prism 20 Solid-state image sensor 21 Image display means 22 Light source of interferometer 23 Collimator lens 24 Beam splitter 25 AOM (frequency shifter) 27 λ / 2 plate 28 Polarizing beam splitter 30 Condensing lens 31 AOM (frequency shifter) 33 λ / 2 plate 34 Polarizing beam splitter 35 Condensing lens 36 Polarization preserving fiber 37 Condensing 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 Condensing lens 65 Excitation light cut filter 66 Photodetector 10 0 Interference optical system L2 Measurement light L3 Reference light

Claims (4)

[Claims] A measuring element main body which can be inserted into a living body; an optical fiber having a tip disposed inside the measuring element main body and a rear end disposed outside the measuring element main body; A measurement light irradiation system that causes measurement light to enter from the rear end and emits from the front end, and irradiates a part inside the living body, and the measurement light reflected from the part and returned to the optical fiber, and emitted from the rear end to the reference light. An interference optical system arranged outside the tracing stylus main body, a photodetector for detecting the measurement light and the reference light interfered by the interference optical system, and based on an output of the photodetector. An in-vivo distance measuring device comprising: a calculating means for calculating a distance from the tip of the tracing stylus body to the site. 2. The in-vivo distance measuring apparatus according to claim 1, wherein a heterodyne interference optical system is used as the interference optical system. 3. The measurement light irradiation system according to claim 1, wherein the measurement light irradiation system emits near-infrared light as the measurement light.
Or the in vivo distance measuring apparatus according to 2. 4. The in-vivo distance measuring apparatus according to claim 1, further comprising means for issuing an alarm when the distance calculated by said calculating means is smaller than a predetermined distance.