JP2016164495A - Optical tomographic image acquisition apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical tomographic image acquisition apparatus capable of acquiring accurate optical tomographic images.SOLUTION: An optical probe 40 comprises an optical fiber 41, a GRIN lens 42, a protective material 43, and a sheath 44. A second end 41b of the optical fiber 41, the GRIN lens 42, and the protective material 43 are configured to form a probe movable section 40A with relative positions thereof fixed. The probe movable section 40A is provided with a gap between itself and an inner peripheral surface of the sheath 44, and is configured to be rotatable inside the sheath 44. An optical tomographic image reference position to be used as a reference when acquiring an optical tomographic image is determined based on an image position on one of interfaces in the probe movable section 40A in the optical tomographic image.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical tomographic image acquisition apparatus.

  An optical tomographic image acquisition device based on optical coherent tomography (OCT) technology splits light output from a light source into measurement light and reference light, and when the measurement light is irradiated onto the measurement object One-dimensional optical tomographic images of the measurement object can be acquired by detecting the interference light caused by the backward reflected light and the reference light generated by the detection unit and analyzing the detection result by the detection unit. In addition, the optical tomographic image acquisition apparatus can acquire a two-dimensional or three-dimensional optical tomographic image by scanning the irradiation position of the measurement light onto the measurement object.

  OCT is roughly classified into time domain OCT (Time Domain OCT; TD-OCT) and Fourier domain OCT (Fourier Domain OCT; FD-OCT). The latter FD-OCT is roughly classified into frequency sweep OCT (Swept Source OCT; SS-OCT) and spectral domain OCT (Spectral Domain OCT; SD-OCT).

  In SD-OCT, broadband light is output from a light source, and an optical tomographic image of a measurement object is acquired by analyzing a spectrum detection result by a detection unit. In SS-OCT, the frequency of light output from a light source is swept, and an optical tomographic image of a measurement object is acquired by analyzing detection results at each frequency by a detection unit. In both SD-OCT and SS-OCT, an optical tomographic image is acquired by Fourier transforming the spectrum of the interference light expressed as a function of the wave number.

  In both SD-OCT and SS-OCT, the measurement object is within a range where the difference between the optical path length of the measurement light and the back reflection light from the light source to the detection unit and the optical path length of the reference light is smaller than a predetermined value. The optical tomographic image can be acquired. Therefore, the optical path length of the reference light needs to be appropriately set according to the range of the measurement object for which an optical tomographic image is to be acquired (depth range in the measurement light irradiation direction).

  The invention disclosed in Patent Document 1 measures a tomographic structure by inserting an optical probe including an optical fiber that guides measurement light and backward reflected light into the lumen of a measurement object having a lumen shape such as a blood vessel. It is. In the optical probe, a condensing optical system and a deflection optical system are connected to the tip of an optical fiber, which are covered with a protective material, and are surrounded by a sheath. The optical fiber, the condensing optical system, the deflecting optical system, and the protective material are rotatable inside the sheath.

  Further, the invention disclosed in Patent Document 1 obtains an optical tomographic image reference position as a reference for acquiring an optical tomographic image based on the image positions of the inner peripheral surface and the outer peripheral surface of the sheath in the optical tomographic image. The optical path length of the reference light is adjusted based on the tomographic image standard position.

JP 2010-99465 A

  The present inventor has found that the inventions disclosed in Patent Documents 1 and 2 have the following problems.

  That is, in the invention disclosed in Patent Document 1, the optical tomographic image reference position is obtained based on the image positions of the inner peripheral surface and the outer peripheral surface of the sheath in the optical tomographic image, and the reference light is calculated based on the optical tomographic image reference position. Adjust the optical path length. Also, in the optical probe, the tip of the optical fiber (the end that outputs the measurement light and the back reflection light from the measurement object), the condensing optical system, the deflection optical system, and the protective material are between them. The probe movable part is fixed in relative positional relationship. The probe movable portion is provided with a gap between the inner peripheral surface of the sheath and is rotatable within the sheath.

  Inside the sheath, the probe movable part is not only rotatable, but also its position and orientation may change. Therefore, even if the optical path length of the reference light is adjusted by obtaining the optical tomographic image reference position based on the image positions of the inner peripheral surface and the outer peripheral surface of the sheath in the optical tomographic image measured at a specific position and orientation, At the time of measurement, the position or orientation of the sheath with respect to the probe movable part may be different from that at the time of adjustment. In such a case, an accurate optical tomographic image cannot be acquired.

  The present invention has been made to solve the above problems, and an object thereof is to provide an optical tomographic image acquisition apparatus that can acquire an accurate optical tomographic image.

  The optical tomographic image acquisition apparatus of the present invention includes (1) a light source that outputs light, (2) a branching unit that branches light output from the light source and outputs it as measurement light and reference light, and (3) the above Measurement light output from the branching unit is input to the first end, is guided and output from the second end, and measurement is output from the second end connected to the second end of the optical fiber. A condensing optical system for condensing light onto a measurement object, a protective material covering the second end of the optical fiber and the condensing optical system, and the optical fiber extending along the optical fiber. And an optical probe including a sheath that surrounds the condensing optical system and the protective material, and the optical fiber, the condensing optical system, and the protective material are rotatable within the sheath; (4) A reference optical system for guiding the reference light output from the branching unit and having a variable optical path length of the reference light; (5) Back-reflected light output from the first end when the measurement light output from the branching unit is input to the first end of the optical fiber, and reference light that has passed through the reference optical system; And (6) a detection unit for detecting the interference light output from the multiplexing unit, and (7) the detection. An optical tomographic image is obtained by frequency analysis of the detection result by the unit, and the interface or reflecting surface of any of the second end of the optical fiber, the condensing optical system, and the protective material in the optical tomographic image is obtained. A control unit that obtains an optical tomographic image standard position serving as a reference for acquiring an optical tomographic image based on the image position, and adjusts an optical path length of the reference light in the reference optical system based on the optical tomographic image standard position; Prepare.

  According to the present invention, an accurate optical tomographic image can be acquired.

It is a figure which shows the structure of the optical tomographic image acquisition apparatus 1 of this embodiment. FIG. 4 is a view showing a cross-sectional structure of a tip portion of the optical probe 40. (A) is a figure which shows the spectrum of the interference light detected by the detection part 52, (b) is a figure which shows the one-dimensional optical tomographic image acquired by the control part 53. FIG. 6 is a diagram illustrating a one-dimensional optical tomographic image acquired by a control unit 53. FIG. It is a figure which shows the change of each image position of the interfaces P1-P7 in the optical tomographic image when 40 A of probe movable parts are rotated. 3 is a diagram illustrating an example of a cross-sectional structure of a tip portion of an optical probe 40. FIG. It is a figure which shows the example of a two-dimensional optical tomographic image.

  The optical tomographic image acquisition apparatus of the present invention includes (1) a light source that outputs light, (2) a branching unit that branches light output from the light source and outputs it as measurement light and reference light, and (3) the above Measurement light output from the branching unit is input to the first end, is guided and output from the second end, and measurement is output from the second end connected to the second end of the optical fiber. A condensing optical system for condensing light onto a measurement object, a protective material covering the second end of the optical fiber and the condensing optical system, and the optical fiber extending along the optical fiber. And an optical probe including a sheath that surrounds the condensing optical system and the protective material, and the optical fiber, the condensing optical system, and the protective material are rotatable within the sheath; (4) A reference optical system for guiding the reference light output from the branching unit and having a variable optical path length of the reference light; (5) Back-reflected light output from the first end when the measurement light output from the branching unit is input to the first end of the optical fiber, and reference light that has passed through the reference optical system; And (6) a detection unit for detecting the interference light output from the multiplexing unit, and (7) the detection. An optical tomographic image is obtained by frequency analysis of the detection result by the unit, and the interface or reflecting surface of any of the second end of the optical fiber, the condensing optical system, and the protective material in the optical tomographic image is obtained. A control unit that obtains an optical tomographic image standard position serving as a reference for acquiring an optical tomographic image based on the image position, and adjusts an optical path length of the reference light in the reference optical system based on the optical tomographic image standard position; Prepare.

  The optical tomographic image is preferably an image obtained by acquiring a plurality of optical tomographic images while rotating the probe movable portion and averaging the plurality of optical tomographic images.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. The present invention is not limited to these exemplifications, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  FIG. 1 is a diagram illustrating a configuration of an optical tomographic image acquisition apparatus 1 according to the present embodiment. The optical tomographic image acquisition apparatus 1 includes a light source 11, a branching unit 12, an optical circulator 21, a mirror 22, a movable stage 23, an optical circulator 31, a rotation motor 32, an optical probe 40, a multiplexing unit 51, a detection unit 52, and a control unit 53. Is provided.

  The light source 11 outputs light and can sweep the frequency of output light. The branching unit 12 is connected to the light source 11 via the optical fiber F1, and inputs light output from the light source 11 and guided by the optical fiber F1. The branching unit 12 branches the input light into measurement light Ls and reference light Lr, outputs the reference light Lr to the optical fiber F2, and outputs the measurement light Ls to the optical fiber F3.

  The optical circulator 21 is connected to the branching unit 12 through the optical fiber F2, receives the reference light Lr output from the branching unit 12 and guided by the optical fiber F2, and receives the input reference light Lr as light. Output to fiber F4. The optical circulator 21 receives the reference light Lr that has been guided by the optical fiber F4 and outputs the reference light Lr to the optical fiber F5.

  The mirror 22 reflects the reference light Lr output from the optical circulator 21, guided by the optical fiber F4, and output from the end face of the optical fiber F4, and inputs the reflected reference light Lr to the end face of the optical fiber F4. . The movable stage 23 moves the mirror 22 in a direction perpendicular to the reflection surface of the mirror 22. In the reference optical system between the optical circulator 21 and the mirror 22, the optical path length of the reference light is variable.

  The optical circulator 31 is connected to the branching unit 12 via the optical fiber F3. The optical circulator 31 receives the measurement light Ls output from the branching unit 12 and guided by the optical fiber F3. Output to fiber F6. Further, the optical circulator 31 receives the measurement light Ls that has been guided by the optical fiber F6 and outputs the measurement light Ls that has been input to the optical fiber F7.

  The optical probe 40 includes an optical fiber 41 and a graded index (GRIN) lens 42. The optical fiber 41 is optically coupled to the optical fiber F6, and the measurement light Ls output from the optical circulator 31, guided by the optical fiber F6, and output from the end face of the optical fiber F6 is input to the first end 41a. The measurement light Ls is output from the second end 41b. The GRIN lens 42 connected to the second end 41b of the optical fiber collects the measurement light Ls and irradiates the measurement object 2 while changing the traveling direction on the reflection surface. Further, the optical fiber 41 outputs the backward reflected light generated by the measurement object 2 and the like from the first end 41a and inputs it to the end face of the optical fiber F6. The rotation motor 32 rotates the optical fiber 41 and thereby scans the irradiation direction of the measurement light Ls from the GRIN lens 42.

  The multiplexing unit 51 inputs the reference light that is output from the optical circulator 21 and guided by the optical fiber F5, and receives the back reflected light that is output from the optical circulator 31 and guided by the optical fiber F7. Then, the reference light and the back reflected light are combined to output interference light. The detection unit 52 is connected to the multiplexing unit 51 via the optical fiber F8, and receives the interference light output from the multiplexing unit 51 and guided by the optical fiber F8, and detects the interference light. . The control unit 53 performs frequency analysis on the detection result of the detection unit 52 and acquires an optical tomographic image. The control unit 53 adjusts the optical path length of the reference optical system by moving the movable stage 23.

  FIG. 2 is a view showing a cross-sectional structure of the tip portion of the optical probe 40. The figure shows a cross section including the central axis of the optical fiber 41. The optical probe 40 includes an optical fiber 41, a GRIN lens 42, a protective material 43 and a sheath 44. The optical fiber 41 guides light (measurement light or backward reflected light) input to one of the first end 41a and the second end 41b and outputs it from the other. The GRIN lens 42 is connected to the second end 41b of the optical fiber 41, and has a reflective surface that is inclined with respect to a plane perpendicular to the optical axis. The GRIN lens 42 functions as a condensing optical system that condenses the measurement light output from the second end 41b of the optical fiber 41, and as an optical system that changes the traveling direction by totally reflecting the measurement light on the reflection surface. Also works.

  The protective material 43 covers the second end 41 b of the optical fiber 41 and the GRIN lens 42. The protective material 43 is in close contact with the side surfaces of the optical fiber 41 and the GRIN lens 42. A gap is provided between the protective material 43 and the reflection surface of the GRIN lens 42. The sheath 44 extends along the optical fiber 41 and surrounds the optical fiber 41, the GRIN lens 42, and the protective material 43. The second end 41b of the optical fiber 41, the GRIN lens 42, and the protective material 43 serve as a probe movable portion 40A in which the relative positional relationship among them is fixed. The probe movable portion 40 </ b> A is provided with a space between the inner peripheral surface of the sheath 44 and is rotatable within the sheath 44.

  The measurement light input to the first end 41a of the optical fiber 41 is guided to the optical fiber 41, and then the interface P1 (second end 41b of the optical fiber 41) between the optical fiber 41 and the GRIN lens 42, the GRIN lens. The irradiation position on the measuring object 2 through the reflecting surface P2 of 42, the interface P3 between the GRIN lens 42 and the protective material 43, the outer peripheral surface P4 of the protective material 43, the inner peripheral surface P5 of the sheath 44 and the outer peripheral surface P6 of the sheath 44. P7 is reached.

  FIG. 3A is a diagram illustrating a spectrum of interference light detected by the detection unit 52. FIG. 6B is a diagram showing a one-dimensional optical tomographic image acquired by the control unit 53. The control unit 53 can acquire an optical tomographic image (FIG. 5B) by performing Fourier transform on the spectrum of the interference light expressed as a function of the wave number (FIG. 4A). When the control unit 53 changes the optical path length of the reference light, the acquired optical tomographic image moves to the left and right in FIG. Therefore, the optical path length of the reference light needs to be appropriately set according to the range of the measurement object 2 for which an optical tomographic image is to be acquired (depth range in the measurement light irradiation direction).

  FIG. 4 is a diagram illustrating a one-dimensional optical tomographic image acquired by the control unit 53. FIG. 5 is a diagram illustrating changes in the image positions of the interfaces P1 to P7 in the optical tomographic image when the probe movable unit 40A is rotated. In the acquired optical tomographic image, in addition to the image of the back reflected light generated at the measurement object 2, the image of the back reflected light generated at each of the interfaces P1 to P6 also appears.

  In the comparative example, the optical tomographic image reference position is obtained based on the image positions of the inner peripheral surface P5 and the outer peripheral surface P6 of the sheath 44 in the optical tomographic image, and the optical path length of the reference light is adjusted based on the optical tomographic image reference position. . In this case, when the probe movable portion 40A rotates inside the sheath 44, the position and orientation of the probe movable portion 40A may change. As a result, the positions and sizes of the images of the interfaces P5 and P6 in the optical tomographic image. It also fluctuates. Therefore, it may not be easy to accurately obtain the image positions of the interfaces P5 and P6 in the optical tomographic image. Further, even if the optical tomographic image standard position is obtained based on the image positions of the interfaces P5 and P6 in the optical tomographic image and the optical path length of the reference light is adjusted, the probe is movable within the sheath 44 in the subsequent measurement. The position or orientation of the portion 40A may be different from that at the time of adjustment. In the comparative example, an accurate optical tomographic image cannot be acquired.

  On the other hand, in the present embodiment, the control unit 53 obtains an optical tomographic image by frequency analysis of the detection result by the detection unit 52, and the interface 53 of any one of the interfaces P1 to P4 in the optical tomographic image. Based on the image position, an optical tomographic image reference position serving as a reference for acquiring the optical tomographic image is obtained. And the control part 53 adjusts the optical path length of the reference light in a reference optical system by moving the movable stage 23 based on this optical tomographic image standard position.

  In the optical tomographic image, the positions and sizes of the images of the interfaces P5 to P7 vary, whereas the positions and sizes of the images of the interfaces P1 to P4 do not vary (or the variation is small). Therefore, in the present embodiment, it is easy to accurately obtain the image positions of the interfaces P1 to P4 in the optical tomographic image. In addition, the position of the probe movable portion 40A inside the sheath 44 during measurement after obtaining the optical tomographic image standard position based on the image positions of the interfaces P1 to P4 in the optical tomographic image and adjusting the optical path length of the reference light. Or even if the orientation may be different from that at the time of adjustment, the image positions of the interfaces P1 to P4 in the optical tomographic image do not change. Therefore, in this embodiment, an accurate optical tomographic image can be acquired.

  In the present embodiment, the image position of any one of the interfaces P1 to P4 is obtained in the optical tomographic image. Since the relative positional relationship between these is fixed and known, the image positions of the interfaces P1 to P4 can be easily obtained based on this relative positional relationship. Since the relative positional relationship between the rotation center of the probe movable portion 40A and the interfaces P1 to P4 is fixed with respect to the rotation of the probe movable portion 40A, a plurality of one-dimensional optical tomographic images measured by rotation are averaged. By doing so, the images of the interfaces P1 to P4 can be emphasized, and the images of the interfaces P5 to P6 whose positions fluctuate with respect to measurement noise and rotation can be reduced. In the optical tomographic image, the image positions of the interfaces P2 to P6 are close to each other, but the image positions of the interfaces P1 and P1 are separated from each other. Therefore, the image positions of the interface P1 are distinguished from the image positions of the interfaces P2 to P6. Can be easily obtained. Further, by searching the image positions of the interfaces P1 to P4 in the optical tomographic image while moving the movable stage 23 and changing the optical path length of the reference light, the image positions of the interfaces P1 to P4 can be easily obtained.

  FIG. 6 is a diagram illustrating an example of a cross-sectional structure of the distal end portion of the optical probe 40. The figure shows a cross section including the vertical axis of the GRIN lens 42. The reflection position of the measurement light on the reflection surface of the GRIN lens 42 is the center of the image in FIG. The distance a from the center of the image to the interface of the probe movable unit 40A is a constant value of 0.20 regardless of the direction. On the other hand, if the central axis of the GRIN lens 42 and the central axis of the sheath 44 do not coincide with each other, the distance b from the image center to the inner peripheral surface or outer peripheral surface of the sheath 44 varies depending on the direction. The value is in the range of .25 to 0.75.

  FIG. 7 is a diagram illustrating an example of a two-dimensional optical tomographic image. FIG. 4A shows an optical tomographic image when the optical tomographic image reference position is an appropriate position. FIG. 5B shows an optical tomographic image when the optical tomographic image reference position is far from the appropriate position (the mirror 22 is farther from the optical fiber F4 than the appropriate position). FIG. 6C shows an optical tomographic image when the optical tomographic image reference position is closer to the appropriate position (the mirror 22 is closer to the optical fiber F4 than the appropriate position). This figure shows a two-dimensional optical tomographic image obtained by rotating the probe movable portion 40A within the sheath 44 in the cross-sectional arrangement shown in FIG. 6 and scanning the measurement light irradiation direction.

  In the comparative example, since the optical tomographic image reference position is obtained based on the image positions in the optical tomographic images of the inner and outer peripheral surfaces of the sheath 44 whose positions differ depending on the direction in FIG. 6, the reference position is determined according to the direction of the determined image position. The optical tomographic image shown in FIG. 7 (b) or FIG. 7 (c) may be acquired, and further adjustment is required to obtain the optical tomographic image shown in FIG. 7 (a). In contrast, in this embodiment, the optical tomographic image reference position is obtained based on the image position in the optical tomographic image of any interface of the probe movable unit 40A whose position does not change depending on the direction in FIG. The optical tomographic image shown in FIG. 7A is acquired regardless of the determined image position direction. In the present embodiment, an accurate optical tomographic image can be easily acquired.

  DESCRIPTION OF SYMBOLS 1 ... Optical tomographic image acquisition apparatus, 2 ... Measuring object, 11 ... Light source, 12 ... Branch part, 21 ... Optical circulator, 22 ... Mirror, 23 ... Movable stage, 31 ... Optical circulator, 32 ... Rotary motor, 40 ... Light Probe, 40A ... probe movable part, 41 ... optical fiber, 42 ... GRIN lens, 43 ... protective material, 44 ... sheath, 51 ... multiplexing part, 52 ... detection part, 53 ... control part, F1-F8 ... optical fiber, Lr: reference light, Ls: measurement light.

Claims (2)

A light source that outputs light;
A branching unit for branching the light output from the light source and outputting it as measurement light and reference light;
The measurement light output from the branching unit is input to the first end, is guided, is output from the second end, and is connected to the second end of the optical fiber and is output from the second end. A condensing optical system for condensing measurement light on the measurement object, a protective material covering the second end of the optical fiber and the condensing optical system, and the light extending along the optical fiber and the light An optical probe including a fiber, a condensing optical system, and a sheath surrounding the protective material, and the optical fiber, the condensing optical system, and the protective material are rotatable inside the sheath;
A reference optical system that guides the reference light output from the branching unit and has a variable optical path length of the reference light;
The back-reflected light output from the first end when the measurement light output from the branching unit is input to the first end of the optical fiber and the reference light that has passed through the reference optical system are combined. Then, a multiplexing unit that outputs interference light by the back reflected light and the reference light,
A detection unit for detecting the interference light output from the multiplexing unit;
An optical tomographic image is obtained by frequency analysis of the detection result by the detection unit, and an interface or reflection of any of the second end of the optical fiber, the condensing optical system, and the protective material in the optical tomographic image. A control unit that obtains an optical tomographic image reference position serving as a reference for acquiring an optical tomographic image based on the image position of the surface, and adjusts an optical path length of the reference light in the reference optical system based on the optical tomographic image reference position; ,
An optical tomographic image acquisition apparatus.   The optical tomographic image acquisition apparatus according to claim 1, wherein the optical tomographic image is an image obtained by acquiring a plurality of optical tomographic images while rotating the probe movable unit and averaging the plurality of optical tomographic images. .

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