JP2006215006A - Optical tomographic imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically prevent the fluctuations in a measuring range caused by the length irregularities of respective probes, even when a plurality of the probes are replaced to be used. <P>SOLUTION: In this optical tomographic imaging system 1, interference light is detected by an interference light detecting means 70, by moving the mirror 54 of a first light path altering means 50 in a state with a second light path altering means 60 being set at an initializing position. The detecting position CP of the first interference signal, in the interference light detected by the interference light detecting means 70, is detected by a drive control means 100, and the position CP is compared with a set detecting position CPref. When the detecting position CP is shifted from the detecting position CPref, the optical path length of the reference light L2 is altered in the second optical path altering means 60 by the drive control means 100. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical tomographic imaging apparatus that acquires an optical tomographic image by OCT (Optical Coherence Tomography) measurement.

  Conventionally, as an endoscope apparatus for observing the inside of a body cavity of a living body, an electronic endoscope apparatus that captures an image of a living body using reflected light reflected from a living body irradiated with illumination light and displays the image on a monitor or the like is widely used. It is used in various fields. Many endoscopes are provided with forceps ports, and biopsy and treatment of tissues in the body cavities can be performed with probes inserted into the body cavities from the forceps ports via the forceps channels.

  As the above-described endoscope apparatus, an ultrasonic tomographic image acquisition apparatus using ultrasonic waves is known, but it is also conceivable to use an optical tomographic image acquisition apparatus using optical interference by low coherent light, for example. Yes. (For example, refer to Patent Document 1.) In the optical tomographic imaging apparatus of Patent Document 1, after the low-coherent light emitted from the light source is divided into the measurement light and the reference light, the measurement light is irradiated to the measurement object and measured. Reflected light from the object is guided to the multiplexing means. On the other hand, the reference light is guided to the multiplexing means after the optical path length is changed in order to change the measurement depth in the measurement object. Then, the reflected light and the reference light are combined by the combining means, and the interference light resulting from the combination is measured by heterodyne detection or the like to obtain an optical tomographic image.

Here, a probe is used that is inserted into a body cavity from a forceps port of an endoscope through a forceps channel when irradiating a measurement object with measurement light. Then, measurement light is irradiated from the probe to the measurement object in the body cavity, and reflected light from the measurement object is guided again to the multiplexing means through the probe.
JP 2002-200037 A

  The above-described OCT measurement is a measurement method that utilizes the fact that interference light is detected when the optical path lengths of the measurement light, reflected light, and reference light coincide with each other, and is measured by changing the optical path length of the reference light. The measurement position (measurement depth) with respect to the object is changed.

  By the way, when performing OCT measurement by inserting a probe into a body cavity as shown in Patent Document 1, it is necessary to disinfect and clean the probe after use, so the probe can be attached to and detached from the main body of the optical tomographic imaging apparatus. Is provided. That is, a plurality of probes used in the optical tomographic imaging apparatus are prepared, and the probes can be changed for each measurement.

  However, since the lengths of the plurality of probes described above, particularly the length of the optical fiber, vary due to manufacturing errors, the optical path length of the measurement light is shifted for each probe, but the change width of the reference light is constant. Is limited to a range of As a result, there is a problem that the measurement region is shifted for each probe, and an optical tomographic image is acquired in a state where the measurement region is shifted each time the probe is replaced.

  Accordingly, the present invention provides an optical tomographic imaging apparatus capable of automatically preventing fluctuations in the measurement range due to variations in the length of each probe even when a plurality of probes are replaced and used. With the goal.

  An optical tomographic imaging apparatus according to the present invention is an optical tomographic imaging apparatus in which a probe that guides measurement light to a measurement target is detachably attached to a main body that acquires an optical tomographic image of the measurement target. A light source that emits coherence light, a light splitting unit that splits low-coherence light emitted from the light source into measurement light and reference light, and an optical path length change unit that changes the optical path length of the reference light split by the light splitting unit Drive control means for controlling the change amount of the optical path length in the optical path length changing means, reflected light from the measurement object when the measurement light is irradiated from the probe, and the optical path length is changed by the optical path length changing means. And a interference means for detecting interference light between the reflected light combined by the multiplexing means and the reference light, and the probe is provided by the light splitting means. Measure the split measurement light An optical fiber that guides to an elephant, and a reflecting member that is provided on the optical axis of the measurement light emitted from the optical fiber and reflects part or all of the measurement light, In order to correct an error in the length of the probe attached to the main body and the first optical path length changing means for changing the optical path length of the reference light in order to change the measurement position in the measurement object in the depth direction. The second optical path length change for changing the optical path length of the reference light so that the area where the measurement is possible by the change in the optical path length by the first optical path length changing means when the probe is attached becomes the preset measurement area. A detection position when the interference light between the reflected light reflected by the reflecting member and the reference light is detected in the interference light detected by the interference light detection means. It will be the setting detection position To, and is characterized in that it controls the change in optical path length in the second optical path length changing means.

  Here, as long as the reflecting member reflects part or all of the measurement light, the configuration thereof is not limited. For example, the reflecting member may be composed of an inner wall surface of a tube covering the optical fiber, A reflective film formed on the inner wall surface of the tube may be used.

  The first optical path length changing means will be described later in detail regardless of its configuration as long as it changes the optical path length of the reference light in order to change the measurement position in the depth direction of the measurement target. For example, it may be an optical delay means including a scanning mirror and a Fourier transform lens that gives a group delay or a phase delay after dispersing the reference light.

  Further, the second optical path length changing means is not limited in its configuration as long as it changes the optical path length of the reference light in order to change the measurable region by the first optical path length changing means. In order to change the measurement position in the vertical direction, the reference light can be changed by moving the mirror that reflects the reference light in the optical axis direction of the reference light, regardless of the configuration, as long as the optical path length of the reference light is changed. The optical path length may be changed.

  According to the optical tomographic imaging apparatus of the present invention, the optical path length changing means changes the optical path length of the reference light in order to change the measurement position in the measurement object in the depth direction, and the main body. In order to correct an error in the length of the probe attached to the probe, a region where measurement is possible due to a change in the optical path length in the first optical path length changing means when the probe is attached becomes a preset set measurement region. As described above, by using the second optical path length changing means for changing the optical path length of the reference light, when a plurality of probes are replaced and used in the optical tomographic imaging apparatus, measurement based on variations in length of each probe is performed. Even when variations occur in the optical path lengths of the light and reflected light, the second optical path length changing means can automatically adjust the length of the optical path length of the reference light in accordance with the variations. Probe length It is possible to prevent variation of the measurement range due to the variation.

  Furthermore, the detection position when the drive control unit detects the interference light between the reflected light reflected by the reflecting member and the reference light in the interference light detected by the interference light detection unit is set in advance. Thus, by controlling the change of the optical path length in the second optical path length changing means, it is possible to automatically prevent the variation of the measurement range due to the variation in the length of each probe. Can be achieved.

  If the probe has a tube covering the optical fiber and the reflecting member is made of the inner wall surface of the tube, it is not necessary to attach a new reflecting member to the probe. However, it is possible to efficiently prevent fluctuations in the measurement range due to variations in the length of each probe.

  Further, if the first optical path length changing means is an optical delay means having a scanning mirror and a Fourier transform lens that gives a group delay or a phase delay after dispersing the reference light, an optical path due to a frequency shift due to the phase delay and a group delay. The length change can be controlled independently, and the speed of the optical path length can be increased.

  In addition, if the second optical path length changing unit changes the optical path length of the reference light by moving the mirror that reflects the reference light in the optical axis direction of the reference light, the optical path length of the reference light with a simple configuration. Changes can be made.

  Embodiments of an optical tomographic imaging apparatus according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic external view showing a preferred embodiment of the optical tomographic imaging apparatus of the present invention. The optical tomographic imaging apparatus 1 includes a main body 1A that acquires a tomographic image of a measurement target by optical coherence tomography measurement, and a probe 10 that is detachably attached to the main body and guides measurement light to the measurement target. . A plurality of probes 10 used for the main body 1A are prepared, and the probe 10 can be removed for cleaning and disinfection.

  FIG. 2 is a block diagram showing a preferred embodiment of the optical tomographic imaging apparatus of the present invention. The main body 1A of the optical tomographic imaging apparatus 1 includes a light source 2 that emits low-coherent light L, light splitting means 3 that splits the low-coherent light L emitted from the light source 2 into measurement light L1 and reference light L2, From the probe 10 for guiding the measuring light L1 divided by the light dividing means 3 to the measuring object S, the optical path length changing means 40 for changing the optical path length of the reference light L2 divided by the light dividing means 3, and the probe 10 A multiplexing means 7 for multiplexing the reflected light L3 from the measurement object when the measurement light L1 is applied to the measurement object S and the reference light L2a whose optical path length has been changed by the optical path length changing means 40; Interference light detecting means 70 for detecting the interference light between the reflected light L3 combined by the means 7 and the reference light L2 is provided.

  Here, the light source 2 includes a laser light source that emits low coherent light such as SLD (Super Luminescent Diode) and ASE (Amplified Spontaneous Emission). The optical tomographic imaging apparatus 1 acquires a tomographic image when the living body in the body cavity is set as the measurement target S. Therefore, attenuation of light due to scattering / absorption when passing through the measurement target S is minimized. For example, it is preferable to use an ultrashort pulse laser light source having a wide spectrum band.

  The light splitting means 3 is composed of, for example, a 2 × 2 optical fiber coupler, and splits the low coherent light L guided from the light source 2 through the optical fiber FB1 into the measurement light L1 and the reference light L2. ing. The light splitting means 3 is optically connected to the two optical fibers FB2 and FB3, respectively, so that the measurement light L1 is guided by the optical fiber FB2 side, and the reference light L2 is guided by the optical fiber FB3 side. It has become.

  The optical fiber FB2 is optically connected to the probe 10, and the measurement light L1 is guided from the optical fiber FB2 to the probe 10. Here, FIG. 3 is a cross-sectional view showing the tip portion 10A of the probe, and the probe 10 will be described with reference to FIGS.

  The probe 10 is inserted into a body cavity from a forceps opening through a forceps channel, for example, and is detachably attached to the rotation drive unit 30 by an optical connector 18. FIG. 3 is a schematic diagram showing an example of the tip portion 10A of the probe 10. As shown in FIG. In FIG. 3, the probe 10 includes a tube 11, an optical fiber FB <b> 10 accommodated in the tube 11, and a prism 17 for emitting the measurement light L <b> 1 guided through the optical fiber FB <b> 10 toward the measurement target S. Yes. The tube 11 is made of a material having flexibility such as resin and having light transmittance, and a cap 12 for sealing the inside of the tube 11 is fixed to a tip portion of the tube 11.

  A flexible shaft 13 is accommodated in the tube 11, and the optical fiber FB <b> 10 is accommodated in the flexible shaft 13. The flexible shaft 13 is composed of, for example, a double contact coil in which a metal wire is wound spirally, and each contact coil is wound so that the winding directions are opposite to each other.

  The distal end of the flexible shaft 13 and the distal end of the optical fiber FB10 are respectively fixed to one end side 14a of the base 14, and a prism 17 is fixed to the other end side 14b of the base 14. Further, a ferrule 15 and a refractive index dispersion lens (Gradient Index Lens) 16 are accommodated in the base 14. Therefore, the reference light L2 emitted from the optical fiber FB10 is guided to the ferrule 15 and the refractive index dispersion lens 16 and enters the prism 17.

  The prism 17 emits the measurement light L1 guided in the optical fiber FB10 to the inner wall surface 11a side of the tube 11, and the measurement light L1 passes through the tube 11 and is irradiated to the measurement object. At the same time, the prism 17 receives the reflected light L3 from the measuring object S by the irradiation of the measuring light L1, and emits it to the optical fiber FB10 side.

  Here, the flexible shaft 13 and the optical fiber FB10 are rotatably provided in the arrow R direction with respect to the tube 11, and the base 14 and the prism 17 are also rotated in the arrow R direction with the rotation of the flexible shaft 13 and the optical fiber FB10. It is supposed to be. Therefore, the measurement light L1 emitted from the prism 17 is irradiated to the measurement object S while rotating in the arrow R direction. Thereby, an optical tomographic image in the rotation direction (radial direction) can be acquired in the body cavity.

  FIG. 4 is a cross-sectional view showing an example of the optical connector 18 of the probe 10. The optical connector 18 detachably attaches the probe 10 to the rotary drive unit 30, and includes a cover 19 fixed to the rotary drive unit 30, a fixed sleeve 20 accommodated in the cover 19, and a fixed sleeve 20. And a connection ring 23 for fixing the rotary cylinder 22 and the rotary connector 32 of the rotary drive unit 30 to each other. The cover 19 is fixed to the casing 31 of the rotation drive unit 30 and is provided so as to slide with respect to the fixed sleeve 20. On the other hand, the fixing sleeve 20 is fixed to the cover 19 by a fixing member 21.

  The rotating cylinder 22 is rotatably held with respect to the fixed sleeve 20 via a bearing 22a. The rotary cylinder 22 is fixed to the flexible shaft 13, and the flexible shaft 13 is rotated by the rotation of the rotary cylinder 22. Further, a connection ring 23 is connected to the rotating cylinder 22, and a thread is formed inside the connection ring 23. The connecting ring 23 is fixed to the rotary connector 32 so that the rotary cylinder 22 rotates in synchronization with the rotary connector 32. A ferrule 24 is accommodated in the rotary cylinder 22, and the optical fiber FB10 and the optical fiber FB2 on the rotation drive unit 30 side are optically connected via the ferrule 24 (not shown). .

  FIG. 5 is a cross-sectional view showing an example of the rotary drive unit 30. The rotation drive unit 30 in FIG. 5 rotates the optical fiber FB10 and the prism 17 in the tube 11 in the direction of arrow R, and a housing 31 having a connector insertion port 31a into which the optical connector 18 is inserted. And a rotary connector 32 protruding from the connector insertion port 31a and connected to the optical connector 18, and a motor 35 for rotating the rotary connector 32. The rotary connector 32 rotates in synchronization with the gear 33, and the gear 33 is connected to a gear 34 fixed to the rotating shaft of the motor 35. When the motor 35 is driven, the rotary connector 32 is rotated through the gears 33 and 34. Further, the rotation drive unit 30 is provided with a stopper 36, and the rotation of the rotary connector 32 can be suppressed by pressing the stopper 36 and contacting the gear 33.

  Here, operation examples of the probe 10 and the rotary drive unit 30 will be described with reference to FIGS. First, when the motor 35 is driven in the rotary drive unit 30, the rotary connector 32 rotates, and the rotary cylinder 22 of the probe 10 connected thereto rotates. Furthermore, when the flexible shaft 13 fixed to the rotating cylinder 22 rotates, the optical fiber FB10 and the prism 17 rotate in the arrow R direction. As a result, the measurement light L1 emitted from the prism 17 is irradiated onto the measurement object S while rotating in the arrow R direction. Here, as described above, since the flexible shaft 13 is composed of two close-contact coils whose winding directions are opposite to each other, the rotational force is applied to the base of the tip regardless of the direction of rotation. 14 can be transmitted (see FIG. 4).

  As will be described later, the optical path length changing unit 40 in FIG. 2 changes the optical path length of the reference light L2 and slightly shifts the reference light L2 in order to change the measurement position in the measurement target S in the depth direction. In addition to the first optical path length changing means 50 to be provided, it has second optical path length changing means 60 for changing the optical path length of the reference light L2. Then, the reference light L2a whose optical path length has been changed and frequency shifted by the optical path length changing means 40 is guided to the multiplexing means 7 through the optical fibers FB4 and FB5.

  The multiplexing means 7 is composed of a 2 × 2 optical fiber coupler, and combines the reference light L2 frequency-shifted and changed in optical path length by the optical path length changing means 40 and the reflected light L3 from the measuring object S. The light is emitted to the interference light detection means 70 side.

  The interference light detection means 70 is composed of, for example, a heterodyne interferometer or the like, and detects the light intensity of the interference light. Specifically, when the sum of the total optical path length of the measurement light L1 and the total optical path length of the reflected light L3 is equal to the total optical path length of the reference light L2, it is strong and weak at the difference frequency between the reference light L2 and the reflected light L3. A beat signal that repeats is generated. As the optical path length is changed by the first optical path length changing means 50, the measurement position (depth) of the measuring object S changes, so that the interference light detection means 70 detects a plurality of beat signals at each measurement position. . The information on the measurement position is output from the drive control means 100 that controls the operation of the optical path length changing means 40. An optical tomographic image is generated on the basis of the beat signal detected by the interference light detection means 70 and the information on the measurement position in the drive control means 100.

  As described above, the probe 10 includes the optical fiber FB10 and is configured to be detachable from the rotation drive unit 30. The length FBL of the optical fiber FB10 is manufactured so that any probe 10 has a specified length. However, the length of the optical fiber FB10 varies due to, for example, a manufacturing error of several mm. . Alternatively, the length of the optical connector 18 may also vary due to a manufacturing error of several millimeters.

  On the other hand, in OCT measurement, measurement is performed in units of several μm, and the manufacturing error of the optical fiber FB10 becomes large for the OCT measurement apparatus. If one probe 10 is used for only one optical tomographic imaging apparatus 1, the optical path length including the manufacturing error of the optical fiber FB10 can be managed when the optical tomographic imaging apparatus 1 is assembled. However, in actuality, since it is necessary to clean the probe 10 at each examination, a plurality of probes 10 are used, and the optical path lengths of the measurement light L1 and the reflected light L3 are changed each time the probe 10 is replaced. It will shift. As a result, every time the probe 10 is replaced, an optical tomographic image with a different measurement region is acquired.

  Specifically, as shown in FIG. 6, when the probe 10 is attached, the setting measurement region MRref that should be able to be measured by the change of the optical path length in the first optical path length changing means 50 is from the probe 10 as shown in FIG. It is assumed that the range is set up to the distance D1. Here, when the length of the optical fiber FB10 of the probe 10 is long by De due to a manufacturing error, the optical path lengths of the measurement light L1 and the reflected light L3 are each long by De. Therefore, the measurable region MR that can detect the interference light between the reflected light L3 and the reference light L2 is shifted from the set measurement region MRref by De, and if measurement is performed in this state, A tomographic image having an error corresponding to the depth direction and De is displayed.

  Therefore, in order to correct an error in the length of the probe 10 attached to the main body 1A in addition to the first optical path length changing unit 50 that changes the optical path length of the reference light L2, the optical path length changing unit 40 The second optical path length changing means for changing the optical path length of the reference light L2 so that the measurable area MR due to the change of the optical path length in the first optical path length changing means 50 becomes the preset set measurement area MRref at the time of attachment. 60 is provided.

  Here, FIG. 7 is a schematic view showing an example of the first optical path length changing means 50, and FIG. 8 is a schematic view showing an example of the second optical path length changing means 60. The first optical path length changing means 60 will be described with reference to FIGS. The 1 optical path length changing means 50 and the 2nd optical path length changing means 60 are each demonstrated.

  First, the first optical path length changing means 50 will be described with reference to FIG. The first optical path length changing means 50 is an optical delay means called “RSOD: Rapid Scanning Optical Delay line”. The detailed principle of this RSOD is described in “Andrew M. Rollins, Manish D. Kulkarni”. , Siavash Yazdanfar, Rujchai Ung-arunyawee and Joseph A. Izatt, “IN vivo video rate optical coherence tomography” Opt. Express 6,219-229 (1998) ”and JP-T-2001-527659.

  The first optical path length changing unit 50 disperses the reference light L2 incident from the optical fiber FB40 via the collimator lens 51 using the dispersive element 52 made of a diffraction grating, and then performs Fourier transform that gives a group delay or a phase delay. The optical delay unit includes a lens 53 and a scanning mirror 54.

  The reference light L2 is incident on the dispersive element 52 at a certain angle. Thereafter, the reference light L <b> 2 passes through the Fourier transform lens 53, is reflected by the scanning mirror 54, passes through the Fourier transform lens 53 again, and enters the dispersive element 52. Then, the reference light L2 is reflected by the reflector 55 by the dispersive element 52, and again enters the optical fiber FB40 through the dispersive element 52, the scanning mirror 54, the Fourier transform lens 53, and the dispersive element 52.

  Here, the scanning mirror 54 is disposed at a position separated by the focal length f of the Fourier transform lens 53, and swings at a high speed in the direction of the arrow σ with the position off the optical axis LL of the Fourier transform lens 53 as the rotation center. It is supposed to be. By changing the amount of tilt of the scanning mirror 54, an optical delay occurs in the reference light L2 transmitted through the Fourier transform lens 53, and the optical path length changes. Note that the optical path length changed by the first optical path length changing unit 50 is, for example, about 2 mm (= D1), and the range in which the optical path length changes is an area where measurement is possible in the depth direction of the measuring object S. .

  Further, the amount of frequency shift can be adjusted by changing the phase delay amount by changing the rotation center of the scanning mirror 54. Therefore, the frequency-shifted reference light L2a is incident on the second optical path length changing unit 60 again through the optical fiber FB40.

  By using such first optical path length changing means 50, it is possible to independently control the frequency shift due to the phase delay and the optical path length change due to the group delay, and to increase the speed of the optical path length change. Can do.

  Next, the second optical path length changing means 60 will be described with reference to FIG. The second optical path length changing means 60 includes a collimator lens 61 that converts the reference light L2 guided by the optical fiber FB4 into parallel light, a corner cube 62 that reflects the reference light L2 converted into parallel light by the collimator lens 61, and After the reference light L2 reflected by the corner cube 62 is converted into parallel light, the collimator lens 63 is emitted to the optical fiber FB40 side. The corner cube 62 is provided so as to be movable in the direction of arrow A, and this movement is controlled by the first drive control means 100. As the corner cube 62 moves in the direction of arrow A, the optical path length of the reference light L2 changes.

  Therefore, the reference light L2 incident on the optical path length changing unit 40 is first incident on the second optical path length changing unit 60 and then incident on the first optical path length changing unit 50 via the optical fiber FB40. After the frequency shift and the optical path length change in the first optical path length changing means 50, the frequency-shifted reference light L2a is incident again on the second optical path length changing means 60 through the optical fiber FB40, and the optical fiber FB4. Is incident on the multiplexing means 7 (see FIG. 2).

  When the probe 10 has become longer due to manufacturing errors (see FIG. 6), the corner cube 62 of the second optical path length changing means 60 moves in the direction of the arrow A2, thereby shortening the optical path length of the reference light L2. In the second optical path length changing means 60 of FIG. 8, when the distance between the collimator lenses 61 and 63 and the corner cube 62 changes by ΔA, the reference light L2 is changed to 2ΔA when entering the first optical path length changing means 50. And is delayed by 2ΔA when guided from the first optical path length changing means 50 to the multiplexing means 7 via the second optical path length changing means 60. As a result, the optical path length of the reference light L2 is only 4ΔA. Change. Therefore, the measurable area MR and the set measurement area MRref can be matched with a small amount of movement by the corner cube 62 moving in the arrow A2 direction based on the relationship of De = 2ΔA. In addition, although the case where the length of the optical fiber FB2 of the probe 10 is longer than the predetermined length is illustrated, the corner cube 62 may be similarly moved in the direction of the arrow A1 even when the length is short.

  The change of the optical path length by the second optical path length changing means 60 described above is automatically performed by the drive control means 100 of FIG. Specifically, in the interference light detected by the interference light detection means 70, the drive control means 100 detects the interference light between the reflected light L3X reflected by the reflecting member (tube inner wall surface) 11a and the reference light L2a. The change of the optical path length in the second optical path length changing means 60 is controlled so that the detection position at this time becomes a preset detection position.

  That is, when the first optical path length changing unit 50 is operated, the measurement is performed in the radial direction (measurement depth direction) of the tube 11 with the optical axis CL of the probe 10 as the measurement start position. Then, the interference light detecting means 70 detects a plurality of interference signals as shown in FIG. Here, since the reflected light L3 is not generated in the space from the optical axis CL to the inner wall surface 11a of the tube 11 (see FIG. 3), the interference light detection means 70 does not detect the interference light. When the reflected light L3X is generated on the inner wall surface 11a of the tube 11, the interference light detection means 70 detects the interference light for the first time.

  Therefore, the drive control means 100 detects the interference light between the reflected light L3 reflected by the inner wall surface 11a of the tube 11 and the reference light L2a at the detection position CP first detected by the interference light detection means 70. Judge. Then, the drive control unit 100 sets the detection position CP when the interference light between the reflected light L3X reflected by the reflecting member (inner wall surface of the tube) 11a and the reference light L2a is detected to a preset detection position CPref. Judge whether there is.

  Here, the set detection position CPref is a position where the interference light between the reflected light L3X and the reference light L2a when the length and diameter of the probe 10 have a prescribed length and diameter should be detected. means. That is, the setting detection position CPref is set to a position where the interference light between the reflected light L3X and the reference light L2a when the reference probe whose distance of the inner wall surface 11a of the tube 11 is known in advance is detected. When the probe 10 having a different length of the optical fiber FB10 is exchanged and used, the detection position CP is adjusted to the set detection position CPref during calibration. Thereby, even when the probe 10 having a different length of the optical fiber is replaced and used, the same measurement range as that when the reference probe is used can be obtained.

  For example, as shown in FIG. 10, when there is a detection position CP after the set detection position CPref, the drive control means 100 controls the second optical path length changing means 60 so that the optical path length of the reference light L2 is shortened. In this way, the product variation in length in the optical fiber FB10 can be automatically corrected using the detection position of the reflected light L3X reflected from the inner wall surface 11a of the tube 11.

  FIG. 11 is a flowchart showing an operation example of the tomographic imaging apparatus 1 according to the present invention. The operation example of the tomographic imaging apparatus 1 will be described with reference to FIGS. 1 to 11. First, in the state where the position of the second optical path length changing means 60 is positioned at the initial setting position, the interference light detecting means 70 detects the interference light when the scanning mirror 54 of the first optical path length changing means 50 is swung. (Step ST1). Then, the detection position CP of the first interference signal among the interference lights detected by the interference light detection means 70 is detected by the drive control means 100 (step ST2), and the detection position CP is compared with the set detection position CPref (step ST2). Step ST3). When the detection position CP and the set detection position CPref are deviated, the corner cube 62 is moved in the direction of arrow A by the drive control means 100 (see FIG. 8), and the optical path length of the reference light L2 is changed. Then, the corner cube 62 is positioned so that the detection position CP coincides with the set detection position CPref by repeating the steps ST1 to ST3 after the change. Thereafter, an optical tomographic image of the living body in the body cavity is acquired.

  According to the above embodiment, the optical path length changing unit 40 changes the optical path length of the reference light L2 in order to change the measurement position in the depth direction of the measuring object S, and the first optical path length changing unit 50 Optical tomographic imaging is provided by including second optical path length changing means 60 that changes the optical path length of the reference light L2 so that the measurable area MR by the optical path length changing means 50 becomes a preset measurement area MRref. When a plurality of probes 10 are used in the apparatus 1, the second optical path length is changed even when the optical path lengths of the measurement light L1 and the reflected light L3 vary due to the length variation of each probe 10. Since the length of the optical path length of the reference light L2 can be adjusted according to the variation by the means 60, the length of each probe 10 can be changed even when a plurality of probes 10 are used. It is possible to prevent variation in the measurement range by month.

  In particular, by using the two optical path length changing means 50 and 60, it is possible to accurately prevent the measurement range from being fluctuated due to variations in the length of each probe 10. That is, as in a normal OCT apparatus, there is only one optical path length changing means, and the length variation of each probe 10 is changed by changing the distance between this optical path length changing means and the light splitting means / multiplexing means. It is also conceivable to prevent fluctuations in the measurement range due to. However, in this case, the entire optical path length changing means must be moved. Since OCT measurement is performed in units of μm, this moving amount also requires accuracy in units of μm, and it is difficult to suppress variation by moving the entire optical path length changing unit. On the other hand, by using the two optical path length changing means 50 and 60, the corner cube 62 can be moved with high accuracy in units of μm. Therefore, the measurement range due to the variation in the length of each probe 10 can be accurately measured. Variations can be prevented.

  Further, a detection position when the interference light between the reflected light L3X reflected by the reflecting member and the reference light L2 in the interference light detected by the interference light detection means 70 is detected by the drive control means 100 is set in advance. By controlling the change of the optical path length in the second optical path length changing means 60 so as to be the set detection position CPref, it is possible to automatically prevent the variation of the measurement range due to the length variation of each probe 10. Therefore, the efficiency of the variation adjustment work can be improved.

  Further, since the inner wall surface 11a of the tube 11 is used as a reflecting member, it is not necessary to attach a separate reflecting member to the probe 10, so that any probe 10 has a measurement range due to variations in the length of each probe. Fluctuations can be prevented.

  Further, as shown in FIG. 7, if the first optical path length changing means 50 is an optical delay means provided with a Fourier transform lens 53 and a scanning mirror 54 for providing a group delay or a phase delay after dispersing the reference light L2. In addition, the frequency shift and the change of the optical path length can be controlled independently, and the speed of the change of the optical path length can be increased.

  Further, as shown in FIG. 8, the second optical path length changing means 60 changes the optical path length of the reference light L2 by the corner cube 62 that reflects the reference light L2 moving in the optical axis direction of the reference light L2. If so, the optical path length of the reference light L2 can be changed with a simple configuration.

  The embodiment of the present invention is not limited to the above embodiment. For example, in FIG. 2, light is transmitted using optical fibers FB1 to FB6, but it may be guided in the air.

  Moreover, in the said embodiment, although the case where the reflection of the tube 11 is measured only in one place and the amount of deviation | shift is detected is illustrated, measuring the tube reflection of several places and calculating the average value etc. The amount of deviation may be calculated by

  Moreover, in the said embodiment, although the inner wall surface 11a of the tube 11 is used as a reflecting member, you may make it form a reflecting film in the inner wall surface 11a of the tube 11. FIG.

  Further, the first optical path length changing unit 50 is exemplified for the configuration in which the optical path length is changed by using the dispersive element 52 and the Fourier transform lens 53. It may be a thing. Specifically, as shown in FIG. 11, the first optical path length changing means 50 includes a rotatable rotating reflector 151 having a plurality of reflectors and a fixed mirror 152, and the second optical path length changing is performed. The reference light L2 guided from the means 60 via the optical fiber FB40 is reflected by the rotary reflector 151 and the fixed mirror 152, whereby the frequency shift and the optical path length are changed.

  Moreover, in the said embodiment, although the 2nd optical path length change means 60 of FIG. 8 illustrates the case where the optical path length is changed by moving the corner cube 62 in the optical axis direction of the reference light L2, the optical path is illustrated. As long as the length is changed, a known technique may be used. For example, the second optical path length changing means 160 in FIG. 12 has two mirrors 161 and 162, and the reference light L2 is repeatedly reflected between the two mirrors 161 and 162. The optical path length is changed by moving the mirror 161 in the arrow α direction.

  In the second optical path length changing means 260 of FIG. 13, a refractive index variable element 261 is provided between the collimator lenses 61 and 63 and the corner cube 62, and the refractive index is adjusted by applying a voltage to the refractive index variable element 261. By changing it, the optical path length of the reference light L2 guided in the variable refractive index element 261 may be changed.

  Further, as shown in FIG. 14, the second optical path length changing unit 360 may include a collimator lens 361 and a mirror 362 that reflects the reference light L <b> 2 that has been collimated by the collimator lens 361. At this time, the reference light L2 reflected by the mirror 362 is guided to the first optical path length changing unit 50 by the optical coupler 270, and the reference light L2a subjected to frequency shift and optical path length change by the first optical path length changing unit 50. Is guided to the optical fiber FB4 (on the multiplexing means 7 side) through the optical coupler 270. As shown in FIG. 15, a beam splitter 280 is used in place of the optical coupler 270 so that the reference light L2 from the first optical path length changing unit 50 enters the optical fiber FB40 via the collimator lens 290. May be.

1 is an external view showing a preferred embodiment of an optical tomographic imaging apparatus according to the present invention. 1 is a block diagram showing a preferred embodiment of an optical tomographic imaging apparatus of the present invention. Sectional drawing which shows an example of the front-end | tip part of the probe in the optical tomographic imaging apparatus of FIG. Sectional drawing which shows an example of the connector of the probe in the optical tomographic imaging apparatus of FIG. Sectional drawing which shows an example of the rotational drive unit in the optical tomographic imaging apparatus of FIG. Schematic diagram showing how the measurable area changes due to variations in probe length Schematic diagram showing an example of the first optical path length changing means of FIG. Schematic diagram showing an example of the second optical path length changing means of FIG. A graph showing an example of a signal detected by the interference light detection means of FIG. The flowchart which shows the operation example of the optical tomographic imaging apparatus of FIG. The schematic diagram which shows another embodiment of the 1st optical path length change means of FIG. The schematic diagram which shows another embodiment of the 2nd optical path length change means of FIG. The schematic diagram which shows another embodiment of the 2nd optical path length change means of FIG. The schematic diagram which shows another embodiment of the 2nd optical path length change means of FIG. The schematic diagram which shows another embodiment of the 2nd optical path length change means of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical tomographic imaging apparatus 1A Main body 2 Light source 3 Light splitting means 6 Optical path length changing means 7 Multiplexing means 10 Probe 11 Tube 11a Inner wall surface 40 Optical path length changing means 50, 150 First optical path length changing means 52 Dispersive element 53 Fourier Conversion lens 54 Scanning mirror 60, 160, 260, 360 Second optical path length changing means 62 Corner cube (mirror)
70 Interference light detection means 100 Drive control means CP Detection position CPref Setting detection position FB10 Optical fiber L Low coherent light L1 Measurement light L2 Reference light L2a Reference light L3, L3X Reflected light MR Measurable area MRref Setting measurement area

Claims (4)

An optical tomographic imaging apparatus for performing measurement by detachably attaching a probe that guides measurement light to a measurement target on a main body that acquires an optical tomographic image of the measurement target,
The body is
A light source that emits low coherence light;
A light splitting means for splitting the low coherence light emitted from the light source into measurement light and reference light;
An optical path length changing means for changing an optical path length of the reference light divided by the light dividing means;
Drive control means for controlling the change amount of the optical path length in the optical path length changing means;
Multiplexing means for multiplexing the reflected light from the measurement object when the measurement light is irradiated from the probe to the measurement object and the reference light whose optical path length has been changed by the optical path length changing means;
Interference light detection means for detecting interference light between the reflected light and the reference light combined by the multiplexing means,
An optical fiber for guiding the measurement light divided by the light dividing means to the measurement object; and an optical fiber provided on the optical axis of the measurement light emitted from the optical fiber. And a reflective member that reflects part or all of the
The optical path length changing means is
First optical path length changing means for changing the optical path length of the reference light in order to change the measurement position in the measurement object in the depth direction;
In order to correct an error in the length of the probe attached to the main body, a region where measurement can be performed by changing the optical path length in the first optical path length changing unit when the probe is attached is set in advance. A second optical path length changing means for changing the optical path length of the reference light so as to be a set measurement region,
A detection position when the interference light between the reflected light reflected by the reflecting member and the reference light in the interference light detected by the interference light detection means is detected by the drive control means is preset. 2. The optical tomographic imaging apparatus according to claim 1, wherein the optical path length change in the second optical path length changing means is controlled so that the set detection position is reached. 2. The optical tomographic imaging apparatus according to claim 1, wherein the probe includes a tube that covers the optical fiber, and the reflecting member includes an inner wall surface of the tube. 3. The optical delay unit according to claim 1, wherein the first optical path length changing unit is an optical delay unit including a scanning mirror and a Fourier transform lens that gives a group delay or a phase delay after dispersing the reference light. Optical tomographic imaging device. 2. The optical path length of the reference light is changed by the mirror that reflects the reference light moving in the optical axis direction of the reference light. 4. The optical tomographic imaging apparatus according to any one of 3 above.

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