JP2002148185A - Oct apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the fetch time for optical tomographic information in an OCT apparatus for obtaining an optical tomographic image using interference of low coherent light. SOLUTION: Signal light L3 which is low coherent light is transmitted through a fiber 192 provided in an OCT probe 13 inserted in a forceps port 91 of an endoscope. The signal light L3 is separated into signal light L3a to L3e of different wavelength bands by a fiber Bragg grating 193, and applied to a body cavity wall 2. Resultant light L4 of signal light L3a7 to L3e' which is reflected light of the signal light L3a to L3e and reference light L2 is transmitted to a photo detecting part 150 by a fiber 124, and separated into resultant light L4a to L4e of different wavelength band by a fiber Bragg grating 151 to detect the intensity of an interference signal. According to the signal intensity, an optical tomographic image is obtained. Since optical tomographic information from five portions scanned by the signal light L3a to L3e can be simultaneously fetched, the fetch time for the optical tomographic information can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an OCT apparatus for acquiring an optical tomographic image, and more particularly to an OCT apparatus that scans an observation unit with signal light that is low coherence light and reflects reflected light of the signal light.
OCT for acquiring an optical tomographic image of an observation unit based on the intensity of an interference signal between a signal light and a reference light having a slight frequency difference
Related to the device.

[0002]

2. Description of the Related Art Conventionally, OCT using low coherence light
(Optical Coherence Tomography) Apparatus for obtaining an optical tomographic image of a scanning area by measuring the intensity of an interference signal of low coherence light by heterodyne detection.
A CT apparatus is used for acquiring an optical tomographic image of a fine structure below the retina of the fundus. The details of the OCT apparatus are described in "O Plus E Vol. 21, No. 7 P. 802-804" (written by Masamitsu Haruna).

[0003] This OCT apparatus uses a laser or SLD.
(Super Luminescent Diode) The low coherence light emitted from the light source is divided into signal light and reference light, and the frequency of the reference light or signal light is slightly shifted by a piezo element or the like, and the signal light enters the scanning area. Then, the reflected light reflected at a predetermined depth of the scanning area and the reference light are multiplexed, the intensity of the interference signal included in the multiplexed light is measured by heterodyne detection, and tomographic information is acquired. Obtain information at the depth of the scanning area where the optical path length of the reference light and the optical path length of the signal light match by moving the movable mirror, etc., arranged on the optical path of the light slightly, and changing the optical path length of the reference light. Can be. Further, by repeating the measurement while slightly shifting the incident point of the signal light, that is, by scanning with the signal light, an optical tomographic image of a predetermined area can be obtained.

[0004] The use of such an OCT apparatus enables early diagnosis of invasion depth of cancer, etc., so that signal light and reflected light of the signal light are reflected by an OCT probe which can be inserted into a forceps port of an endoscope apparatus. Development of a method of guiding light to obtain an optical tomographic image of a body cavity has been advanced. For example, "OPTICS LETTE
R Vol.24, No19 P1358〜P1360 ”(by Andrew M Rollins
and Rujchai Ung-arunyawee) have an optical fiber that guides the signal light, and an OCT probe that is provided at the tip of this optical fiber and has a mirror that reflects the signal light at right angles. There is described an OCT apparatus that performs a radial scan by rotating a mirror at the distal end by inserting the mirror into a body cavity through the body and displaying a radial optical tomographic image that is an optical tomographic image of a sliced state of the body cavity wall.

[0005] Further, an OCT apparatus for generating and displaying a three-dimensional optical tomographic image from a large number of optical tomographic images has been filed by the present applicant as Japanese Patent Application No. 2000-332360.

[0006]

As described above, in order to scan the signal light and obtain an optical tomographic image of a predetermined area, it is necessary to take in optical tomographic information from a number of locations in the scanning area. However, in the conventional OCT apparatus, since tomographic information is fetched from each point of the scanning area by one signal light, it is difficult to fetch a large amount of optical tomographic information in a short time. For this reason, for example, while capturing optical tomographic information from a predetermined scanning region in the living body specified by the observer, the scanning region may move due to heartbeat or breathing, and in this case, a desired scanning region may be moved. There is a possibility that an optical tomographic image of the scanning area cannot be obtained.

Further, when generating and displaying a three-dimensional optical tomographic image from the acquired optical tomographic image, it is necessary to capture optical tomographic information from a greater number of locations. When the region has moved, the generated three-dimensional optical tomographic image may be disturbed.

[0008] Even when acquiring an optical tomographic image of an observation unit other than the living body, it is not desirable that the acquisition time of the optical tomographic image is long.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in consideration of the above-mentioned problem.
It is an object to provide a CT apparatus.

[0010]

In an OCT apparatus according to the present invention, a scanning area of an observation section is scanned with a signal light that is low coherence light, and reflected light of the signal light from a predetermined deep portion of the scanning area; In an OCT apparatus for detecting the intensity of an interference signal between a signal light and a reference light having a slight frequency difference and acquiring an optical tomographic image of a scanning region based on the intensity, a plurality of different signals are scanned before scanning the signal light. Signal light separating means for separating into signal light independent of each other in a wavelength band, reflected light from a different portion of a scanning area scanned by the signal light separated by the signal light separating means, and multiplexed light with reference light. Multiplexed light separating means for separating the light into a plurality of different wavelength bands.

Here, the "scanning region" may be of any shape as long as it is a region that can be scanned. For example, there are a line-like region on the observation unit and a region on the surface. When the observation unit observes a body cavity in the depth direction, for example, a ring-shaped area, a cylindrical area, and the like are also included in the “scanning area”.

When "scanning the scanning area", any scanning method may be used. For example, the scanning is performed by rotating a reflection optical element attached to the tip of a light guiding means for guiding signal light. Or a scanning method that can acquire an optical tomographic image by signal light, such as radial scanning for performing scanning and linear scanning for performing scanning by moving the irradiation position of signal light in a line. Note that any scanning method for scanning the signal light may be used.For example, a method of performing scanning by moving the emission end of the signal light, a mirror capable of controlling the reflection direction of the signal light emitted from the emission end, or the like may be used. A method of performing scanning by reflecting light may be used.

[0013] At least one of the signal light separating means and the multiplexed light separating means may be a Bragg grating for setting a stepwise changing grating interval in the optical waveguide, or a light in a different wavelength band. May be composed of a plurality of dichroic prisms for reflecting light, but the present invention is not limited to this. For example, a combination of mirrors having wavelength selection characteristics may be used,
That is, any signal light or multiplexed light can be separated into a plurality of different wavelength bands.

Here, the "Bragg grating" may be formed by any method of forming a grating, for example, a method of forming a grating interval by an etching method for forming periodic irregularities in an optical waveguide, Alternatively, there is a method in which a lattice spacing is formed by a cladding method in which periodic cladding is provided, or a method in which a lattice spacing is formed by periodically providing a high refractive index region.

If the signal light and the multiplexed light are propagated through a fiber, the Bragg grating is preferably a fiber Bragg grating formed at the output end of the fiber.

When the observation section is a living body observation section,
The wavelength of the low coherence light is preferably 600 nm or more and 1700 nm or less.

In the present invention, the light source that emits the low coherence light is not limited to a specific light source.
Any light source may be used.

[0018]

In the OCT apparatus according to the present invention, signal light separating means for separating signal light into a plurality of independent signal lights of a plurality of different wavelength bands before scanning, and signal light separated by the separating means. Since there are provided multiplexed light separating means for separating the multiplexed light of the reflected light from the different portions of the scanned scanning area and the reference light into a plurality of different wavelength bands, the plurality of multiplexed lights separated by the signal light separating means are provided. Reflected light can be simultaneously obtained from a plurality of locations in the scanning area with the signal light, and the interference signal at each of the plurality of locations in the scanning area can be measured separately from the interference signal between the signal light and the reference light included in the combined light. Can be. For this reason, it becomes possible to take in optical tomographic information simultaneously from a plurality of positions in the scanning area, and it is possible to shorten the time to take in optical tomographic information. Further, it is possible to acquire an optical tomographic image which is less affected by the movement of the scanning region and has high reliability.

If at least one of the signal light separating means and the multiplexed light separating means is a Bragg grating for setting a stepwise changing grating interval in the optical waveguide, the signal light or the multiplexed light can be efficiently separated into different wavelength bands. Can be separated.

The signal light and the multiplexed light are propagated through a fiber. If the fiber Bragg grating formed at the end of the fiber is used as the Bragg grating, the fiber as the light guide means and the wavelength separating means are separated. The fiber Bragg grating as the means can be integrally formed, and the loss of light when guiding signal light or multiplexed light can be reduced.

If at least one of the signal light separating means and the multiplexed light separating means is composed of a plurality of dichroic prisms reflecting light in different wavelength bands, the manufacturing cost of the wavelength separating means can be reduced. . Also,
Since the wavelength separation means can be added later, the wavelength separation band can be easily changed or the number of bands can be easily increased.

The wavelength of the low coherence light is 600
When the wavelength is in the range of not less than 1 nm and not more than 1700 nm, the desired light tomographic image can be obtained because the signal light has desirable transmittance and scattering property in the living body observation unit.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an entire embodiment of an OCT apparatus according to the present invention. This OCT apparatus includes an OCT probe 13 inserted into a forceps port 91 provided in an insertion section 11 of an endoscope. To obtain a three-dimensional radial optical tomographic image 3 in the body cavity 1 of the subject,
To display.

The OCT apparatus includes an OCT probe 13 inserted into a forceps port 91 provided in an insertion section 11 of an endoscope inserted into a body cavity 1 of a subject, and a radial optical tomographic image in the body cavity 1. To obtain a three-dimensional radial optical tomographic image 3
A CT unit 12 and a monitor 14 for displaying a three-dimensional radial optical tomographic image 3 are provided. Note that the insertion unit 11 includes an illumination light irradiation unit and an imaging unit (not shown) for imaging.

The OCT unit 12 has a wavelength λs as shown in FIG.
From the light source unit 110 that emits the low coherence light L1 having a substantially flat wavelength band up to the wavelength λm, the low coherence light L1 is divided into the reference light L2 and the signal light L3, and the signal light L3
Fiber-coupled optical system 12 that multiplexes the reflected light and the reference light L2
0, an optical path delay unit 130 arranged on the optical path of the reference light L2 to change the optical path length of the reference light L2, and the reflected light of the signal light L3 reflected at a predetermined deep portion of the scanning region in the body cavity 1 and the reference light. light
A light detection unit 150 for detecting the multiplexed light L4 with L2, and a light detection unit 15
The intensity of the interference signal (beat signal) is detected from the combined light L4 detected at 0, and heterodyne detection for obtaining the intensity of the reflected light of the signal light L3 reflected at a predetermined deep portion of the scanning area from the signal intensity is performed. Signal processing unit 160 that generates an optical tomographic image
During the first radial scan, the body cavity wall 2 and O
A scanning range control unit 170 that determines the positional relationship of the CT probe 13 and controls the radial scanning range based on the positional relationship.
And a three-dimensional optical tomographic image generator 180 for generating a three-dimensional radial optical tomographic image based on the radial optical tomographic image generated by the signal processor 160.

The light source unit 110 of the OCT unit 12 is a mode-locked titanium sapphire laser that emits low coherence light L1.
And a lens 112 for condensing the low coherence light L1 emitted from the mode-locked titanium sapphire laser 111.
And

The fiber coupling optical system 120 converts the low coherence light L1 emitted from the light source 110 into a signal light L3 and a reference light L2.
And a fiber coupler 12 that combines the reflected light of the signal light L3 from the scanning area 3 and the reference light L2 to obtain a combined light L4.
1, a frequency shifter 122 using a piezo element that causes a slight frequency shift in the signal light L3, and a fiber coupler 12
Fiber connecting the light source unit 110 and the optical path delay unit 130 via 1
And an OCT probe 13 via a fiber coupler 121.
And a fiber 124 connecting the photodetector 150. The fibers 123 and 124 are optical fibers.

The optical path delay unit 130 condenses the reference light L2 emitted from the fiber 123 and irradiates the same to the mirror 132. The optical path delay unit 130 condenses the reference light L2 reflected by the mirror 132 and condenses the reference light L2.
And a mirror 132 for changing the optical path length of the reference light L2 by moving in the horizontal direction in FIG.
And a drive unit 133 for moving the mirror 132 in the horizontal direction.

The light detection section 150 is provided at the output end of the fiber 124 and converts the combined light L4 into combined lights L4a to L4e of different wavelength bands.
A fiber Bragg grating 151 as multiplexed light separating means for splitting the light into two components, and photodetectors 152a to 152e for detecting the multiplexed lights L4a to L4e. The configuration of the fiber Bragg grating 151 will be described later in detail.

The signal processing unit 160 detects the intensity of the interference signal (beat signal) from each of the multiplexed lights L4a to L4e detected by the light detection unit 150, and is reflected at a predetermined depth of the scanning area from the signal intensity. Heterodyne detection for obtaining the intensity of the signal light is performed, a radial optical tomographic image is generated for each of the combined lights L4a to L4e, and output to the three-dimensional optical tomographic image generation unit 180. In addition, at the time of the first radial scanning, the detection result is output to the scanning range control unit 170.

The three-dimensional optical tomographic image generating unit 180 has a storage unit (not shown) for storing a plurality of radial optical tomographic images output from the signal processing unit 160, and stores a plurality of radial optical tomographic images stored in the storage unit. Based on the radial optical tomographic image, a three-dimensional radial optical tomographic image 3 is generated and output to the monitor 14.

The OCT probe 13 includes a cladding tube 191 that can be inserted into the forceps port 91 of the insertion section 11 of the endoscope, and a fiber 192 that passes through the cladding tube 191. At the tip of the fiber 192, the signal light L3 guided by the fiber 192 is converted into signal lights L3a to L3e of five frequency bands (center wavelengths λa to λe).
And irradiates the body cavity wall 2 with the signal lights L3a to L3e.
A fiber Bragg grating 193 is provided as signal light separating means for returning the reflected light from the scanning area 3 to the fiber 192. Details of the configuration of the fiber Bragg grating 193 will be described later. Fiber 192 and fiber Bragg grating 193
Is fixedly incorporated in the cladding tube 191. Also, the rear end of fiber 192, that is, fiber 12
The signal light L3 emitted from the fiber 124 is introduced into the fiber 192 at the connection between the fiber 4 and the fiber 192.
191 is reflected light of the signal light L3, ie, the signal L3
A lens 194 for returning a ′ to L3e ′ to the fiber 124 is provided. A scanning mechanism 195 that rotates and slides the cladding tube 191 is attached to a root portion of the cladding tube 191. The scanning mechanism 195 is connected to a controller (not shown), and slides and rotates the cladding tube 191 to perform radial scanning of a predetermined scanning area by the signal lights L3a to L3e. The tip of the cladding tube 191 is
The signal light L3a to L3e that can protect the fiber Bragg grating 193 and the signal light that is the reflected light
It is formed of a transparent material that transmits L3a ′ to L3e ′.

Next, the fiber Bragg grating 193
Will be described. Fiber Bragg grating 19
Reference numeral 3 denotes a reflective grating that irradiates ultraviolet rays to provide a periodic high refractive index region in the fiber, forms a Bragg diffraction grating, and reflects light having a wavelength corresponding to the grating interval. FIG. 3A is a schematic view of the fiber Bragg grating 193. As shown in this figure, in the longitudinal direction of the fiber 192, grating groups Ba to Be in which the grating interval is changed stepwise are provided at an angle of 45 degrees. Actually, each of the grating groups Ba to Be is located at a distance of 72 from each other with the longitudinal direction of the fiber Bragg grating 193 as an axis.
It is arranged in a positional relationship rotated by degrees. Therefore, the signal lights L3a to L3e reflected by the respective grating groups Ba to Be are emitted in directions shifted by 72 degrees as shown in FIG. 3B. In FIG. 1 which is a schematic configuration diagram, the signal light L3a
Although the emission directions of L3e to L3e are schematically described, the actual signal lights L3a to L3e are emitted after being rotated by 72 ° with respect to each other as described above.

Each of the grating groups Ba to Be separates the wavelength bands λs to λm of the signal light L3 into five independent wavelength bands. As shown in FIG. 4, the wavelength band λ of the signal light L3
Assuming that the wavelengths obtained by dividing s to .lambda.m into approximately five equal parts are .lambda.1, .lambda.2, .lambda.3 and .lambda.4, the grating group Ba reflects light having a wavelength equal to or less than .lambda.1 and transmits light having a wavelength longer than .lambda.1. Similarly, the grating group Bb reflects light having a wavelength of λ2 or less and transmits light having a wavelength longer than λ2. The grating group Bc reflects light having a wavelength less than λ3 and transmits light longer than λ3, and the grating group Bd reflects light having a wavelength less than λ4 and transmits light longer than λ4. The grating group Be reflects light having a wavelength of less than λm and transmits light having a wavelength longer than λm. Therefore, the fiber 192
The signal light L3 guided by λa has a center wavelength λa as shown in FIG.
Λe to the signal light L3a to L3e.
Are emitted in a direction perpendicular to the longitudinal direction of

Λa = (λs + λ1) / 2, λb = (λ1
+ Λ2) / 2, λc = (λ2 + λ3) / 2, λd = (λ3 + λ
4) / 2, λe = (λ4 + λm) / 2.

The fiber Bragg grating 151 provided in the photodetector 150 shown in FIG. 1 also has the same configuration as the fiber Bragg grating 193, and the multiplexed light L4 is a multiplexed light having a center wavelength of λa to λe. L4a 〜
Separate into L4e.

Next, the operation of the OCT apparatus according to the embodiment of the present invention when displaying a three-dimensional radial optical tomographic image will be described. The observer inserts the insertion section 11 of the endoscope apparatus into the body cavity 1 of the subject, and then inserts the OCT probe 13 into the forceps port 91 of the insertion section 11.

First, low coherence light L1 for acquiring an optical tomographic image is emitted from a mode-locked titanium sapphire laser 111, and this low coherence light L1 is condensed by a lens 112 and introduced into a fiber 123.

Low coherence light transmitted through the fiber 123
L1 is divided by a fiber coupler 121 into a reference light L2 traveling in the direction of the optical path delay unit 130 in the fiber 123 and a signal light L3 traveling in the direction of the OCT probe 13 in the fiber 124.

The signal light L3 is modulated by the frequency shifter 122 provided on the optical path, and a slight frequency difference Δf occurs between the reference light L2 and the signal light L3.

The signal light L 3 is supplied to the lens 194 of the OCT probe 13.
The signal light L3a to the signal light L3e is separated by the fiber Bragg grating 193 through the fiber 192, and is irradiated to the scanning area of the body cavity wall 2 in the body cavity 1. For example, the signal light L3a is applied to one point in the scanning area 4 indicated by a broken line in FIG. Among the signal lights L3a to L3e incident on the scanning area, the signal lights L3a 'to L3 reflected at a predetermined depth of the scanning area.
e ′ is returned to the fiber 192 via the fiber Bragg grating 193. The signal lights L3a 'to L3e' returned to the fiber 192 are incident on the fiber 124 by the lens 194, and are multiplexed in the fiber coupler 121 with the reference light L2 returned to the fiber 123 described later.

On the other hand, the reference light L2 passes through the fiber 123, enters the mirror 132 via the lens 131 of the optical path delay unit 130, is reflected by the mirror 132, passes through the lens 131 again, and returns to the fiber 123. Can be The reference light L2 returned to the fiber 123 is multiplexed by the fiber coupler 121 with the above-described signal lights L3a 'to L3e'.

The signal light L3 multiplexed by the fiber coupler 121
a ′ to L3e ′ and the reference light L2 are again coaxially overlapped, and become a combined light L4. Further, the signal lights L3a 'to L3e' and the reference light L2 interfere with each other to generate a beat signal (interference signal).

That is, the reference light L2 and the signal lights L3a to L3
e is a low coherence light with a short coherence distance,
After the low coherence light L1 is split into the signal light L3 and the reference light L2, the signal lights L3a to L3e (L3a 'to L3e') are converted to fiber couplers.
When the optical path length before reaching the reference light L2 is approximately equal to the optical path length before reaching the fiber coupler 121, the two lights interfere with each other, and the difference in frequency between the interfering lights (Δf) reduces the intensity. Repeated interference signals (beat signals) are generated.

The multiplexed light L4 propagates through the fiber 124 and is separated by the fiber Bragg grating 151.
a to L4e, which are detected by the photodetectors 152a to 152d.

In the signal processing section 160, first, each photodetector 15
From the combined lights L4a to L4e detected by 2a to 152d, the intensity of the interference signal (beat signal) is detected, and the intensity of the signal light L3a 'to L3e' reflected on a predetermined surface at each position in the scanning area is obtained. Perform heterodyne detection.

In the above operation, the detection is first performed in a state where the position of the mirror 132 is controlled by the driving unit 133 to the left side in the figure. For each detection, the position of the mirror 132 is moved horizontally in the direction of the optical axis (rightward in the figure). Therefore, the optical path length until the reference light L2 reaches the fiber coupler 121 changes, and the optical path length of the signal light L3 (L3a 'to L3e') that interferes with the reference light L2 also changes. Change. The movement of the mirror 132 causes the fiber Bragg grating 193 to scan in the radial direction, and captures tomographic information from the surface of the body cavity wall 2 in the body cavity 1 to a desired depth.

In the above-described radial scanning, the first scanning is performed from the vicinity of the fiber Bragg grating 193.
Scanning is performed to the extent that scanning is possible, but the range in which an interference signal (beat signal) is actually detected is limited. For example, as shown in FIG.
Is located at a position deviated from the center in the body cavity 1, even if the fiber Bragg grating 193
The scanning from the surface of the fiber cavity to the nearest body cavity wall 2 (the distance Se in the arrangement shown in FIG. 6) is meaningless, and the body cavity wall 2 furthest from the surface of the fiber Bragg grating 193 (the arrangement shown in FIG. In this case, it is unnecessary to perform scanning beyond the range obtained by adding the detectable body cavity wall thickness to the distance Sb).

In order to eliminate the unnecessary radial scanning as described above, the result of the first radial scanning is output from the signal processing unit 160 to the scanning range control unit 170. The scanning range control unit 170 determines the distance S1 from the surface of the fiber Bragg grating 193 to the nearest body cavity wall based on the detection result of the first radial scan, and the fiber Bragg grating 193.
Find the distance S2 from the surface of the body to the furthest body cavity wall,
132 is limited to a range from S1−α1 to S2 + α2. Note that α1 and α2 are determined in consideration of an error, unevenness of a body cavity wall, a detectable body cavity wall thickness, and the like.

When the initial radial scanning is completed, the scanning mechanism 176 slightly rotates the cladding tube 193, that is, the fiber Bragg grating 193, and at a point slightly deviated from the initial radial scanning point, the scanning mechanism 176 also performs a predetermined operation. Captures fault information up to a depth of. Scanning at 360 degrees is performed by repeating such minute rotation, that is, by radial scanning.

In the signal processing unit 160, based on the information obtained by the radial scanning and the radial scanning, the combined light L4
A radial optical tomographic image is generated for each of a to L4e and output to the three-dimensional optical tomographic image generating unit 180.

When a radial optical tomographic image is acquired by the above-described operation, the scanning mechanism 195 slides the cladding tube 193 slightly, and similarly in a scanning region shifted so as not to overlap the previous scanning range. Obtain a radial optical tomographic image. Acquisition of such radial optical tomographic images,
By repeating the sliding movement of the cladding tube 193, a radial optical tomographic image of a predetermined range is accumulated in the three-dimensional optical tomographic image generating unit 180. The three-dimensional optical tomographic image generator 180 generates a three-dimensional radial optical tomographic image based on these radial optical tomographic images and outputs the generated image to the monitor 14.

In the monitor 14, a three-dimensional optical tomographic image generator 18
The three-dimensional radial optical tomographic image output from 0 is displayed. With such an operation, a three-dimensional radial optical tomographic image of the body cavity 1 can be displayed.

As described above, the OCT of this embodiment
In the device, the signal light L3 is converted to the signal light L3 having a different wavelength band.
a ′ to L3e ′, perform scanning, and separate the multiplexed light L4 into multiplexed lights L4a ′ to L4e ′ having different wavelength bands to detect the signal intensity of the interference signal. It is possible to capture optical tomographic information from a plurality of locations at the same time, and it is possible to shorten the capturing time of optical tomographic information. In addition, it is possible to prevent the body cavity wall 2 from moving during capturing of an optical tomographic image and to prevent the optical tomographic image of a desired scanning region from being acquired, and to acquire an optical tomographic image having high reliability.

Since the signal light L3 and the multiplexed light L4 are guided by a fiber and separated by a fiber Bragg grating formed at the output end of the fiber, the fiber as the light guiding means and the fiber Bragg grating as the wavelength separating means are separated. Can be integrally formed, and the signal light L3
Further, loss of light when propagating the combined light L4 can be reduced.

Further, the wavelength of the low coherence light is 80
Since it is 0 nm, the signal light L4 has desirable transmittance and scattering properties in the body cavity wall 2, so that a desired optical tomographic image can be obtained.

Since the separated signal lights L3a to L3e are emitted in different directions, the positional relationship between the body cavity 1 and the fiber Bragg grating 193 should be detected at the time of the first radial scanning. Based on this positional relationship, unnecessary scanning in the radial direction for capturing optical tomographic information can be omitted, so that the time for capturing optical tomographic information can be further reduced.

In addition, when the cladding tube 193 is slid, it is sufficient that the cladding tube 193 is slid at one time by the length in the longitudinal direction of the fiber Bragg grating 193, and a precise moving mechanism required when moving the minute amount is unnecessary. And the scanning mechanism 195
Mechanism can be simplified.

As a modified example of the above embodiment, a dichroic prism set 201 as shown in FIG. 7A may be used instead of the fiber Bragg grating 193 of the OCT probe 13. The dichroic prism set 201 has wavelengths λa to λe, respectively.
The dichroic prisms Da to De that reflect only light in a predetermined wavelength range in the perpendicular direction around the center and transmit light of other wavelengths are connected in the longitudinal direction of the fiber 192, and the signal light L3 uses these dichroic prisms Da-De.
As a result, the light is separated into signal lights L3a to L3e.

The dichroic prisms Da to De are arranged in a positional relationship rotated by 90 degrees with respect to the longitudinal direction of the fiber 192 as an axis.
The signal lights L3a to L3d reflected in the directions shown in FIG. 7B are emitted in directions shifted by 90 degrees each other, as shown in FIG.
Is emitted in the same direction as the signal light L3a. Further, a dichroic prism set 201 can be used instead of the fiber Bragg grating 151 of the light detecting section 150. When the dichroic prism set 201 is used, the manufacturing cost of the wavelength separating means can be reduced. Further, since the dichroic prism set 201 can be added to the fiber 192, the wavelength separation band can be easily changed or increased.

In this embodiment, a three-dimensional radial optical tomographic image is obtained. However, the present invention is not limited to this.
For example, when acquiring a linear tomographic image, a CT apparatus may be used to slide the cladding tube 191 without performing a radial scan, so that a vertical optical tomographic image in the body cavity 1 can be obtained in a short time. Can be obtained. In addition, even when the three-dimensional optical tomographic image is acquired by performing the scanning at a desired angle without performing the 360-degree radial scanning, the acquisition time of the optical tomographic image can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an OCT apparatus according to a first embodiment of the present invention;

FIG. 2 is an explanatory diagram of a wavelength band of signal light.

FIG. 3 is an explanatory diagram of a fiber Bragg grating

FIG. 4 is an explanatory diagram of the reflectance of a fiber Bragg grating

FIG. 5 is an explanatory diagram of a wavelength band of the separated signal light.

FIG. 6 is an explanatory diagram of a positional relationship between a body cavity and a fiber Bragg grating.

FIG. 7 is an explanatory diagram of a dichroic prism set.

[Explanation of symbols]

 Reference Signs List 1 body cavity 2 body cavity wall 11 insertion section 12 OCT section 13 OCT probe 14 monitor 91 forceps port 110 low coherence light source section 120 fiber coupling optical system 123,124,192 fiber 130 optical path delay section 150 light detection section 151,193 fiber Bragg grating 152a-152d photodetector 160 Signal processing unit 170 Scanning range control unit 180 Three-dimensional optical tomographic image generation unit 191 Cladding tube 201 Dichro prism set Ba, Bb, Bc, Bd, Be Lattice group Da, Db, Dc, De, De Dichro prism L1 Low coherence light L2 Reference light L3, L3a ~ L3e, L3 ', L3a' ~ L3e 'Signal light L4 Combined light

Claims (5)

[Claims] 1. A scanning area of an observation section is scanned with a signal light that is a low coherence light, and a reflected light of the signal light from a predetermined deep portion of the scanning area and a reference having a slight frequency difference from the signal light. In an OCT apparatus for detecting the intensity of an interference signal with light and acquiring an optical tomographic image of the scanning region based on the intensity, the signal light is subjected to independent signals of a plurality of different wavelength bands before the scanning. Signal light separating means for separating the light into light, reflected light from a different portion of the scanning region scanned by the signal light separated by the signal light separating means, and multiplexed light with the reference light, OC comprising multiplexed light separating means for separating each wavelength band.
T device. 2. An OCT according to claim 1, wherein at least one of said signal light separating means and said multiplexed light separating means is a Bragg grating for setting a stepwise changing grating interval in an optical waveguide. apparatus. 3. The OCT according to claim 2, wherein the signal light and the multiplexed light are propagated by a fiber, and the Bragg grating is a fiber Bragg grating formed at an emission end of the fiber. apparatus. 4. The apparatus according to claim 1, wherein at least one of said signal light separating means and said multiplexed light separating means comprises a plurality of dichroic prisms for reflecting light in different wavelength bands. The OCT apparatus according to claim 1. 5. The observation section is a living body observation section, and the wavelength of the low coherence light is 600 nm or more and 1700
The OCT apparatus according to any one of claims 1 to 4, wherein the OCT is equal to or less than nm.