JP2009178200A - Optical probe for oct and optical tomographic imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively and safely realize the reduction of the deterioration of measuring precision caused by the light insertion loss and light reflection loss at the rotary joint between the distal end part and base end part of the probe in the optical probe for OCT inserted in a subject. <P>SOLUTION: An optical fiber 12 is arranged in the internal space of the almost cylindrical sheath 11 inserted in the subject in the longitudinal direction of the sheath 11. The light L1 emitted from the distal end of the optical fiber 12 is deflected to the subject by a leading end optical system 15 and shaken at a predetermined angle around the axial line of the sheath 11 in the longitudinal direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an OCT optical probe and an optical tomographic imaging apparatus. More specifically, the present invention relates to an OCT optical probe having a function of optical scanning in the circumferential direction of the long axis of the OCT optical probe, and the OCT optical probe. The present invention relates to an optical tomographic imaging apparatus that acquires an optical tomographic image to be measured by OCT (Optical Coherence Tomography) measurement.

  Conventionally, as one method for acquiring a tomographic image of a measurement target such as a biological tissue, a method for acquiring a tomographic image by OCT measurement has been proposed. This OCT measurement is a kind of optical interferometer. After the low-coherent light emitted from the light source is divided into measurement light and reference light, the reflected light from the measurement object when the measurement light is irradiated onto the measurement object. Alternatively, the backscattered light and the reference light are combined, and a tomographic image is acquired based on the intensity of the interference light between the reflected light and the reference light. Hereinafter, the reflected light and the backward scattered light from the measurement object are collectively referred to as reflected light.

  The OCT measurement is roughly divided into two types: TD (Time Domain) -OCT measurement and FD (Fourier Domain) -OCT measurement.

  In TD-OCT measurement, a reflected light intensity distribution corresponding to a position in the depth direction of a measurement target (hereinafter referred to as a depth position) is obtained by measuring the interference intensity while changing the optical path length of the reference light. It is.

  On the other hand, in the FD-OCT measurement, the interference light intensity is measured for each spectral component of the light without changing the optical path lengths of the reference light and the signal light, and the spectral interference intensity signal obtained here is Fourier transformed by a computer. This is a method of obtaining a reflected light intensity distribution corresponding to a depth position by performing a representative frequency analysis. In recent years, FD-OCT measurement has attracted attention as a technique that enables high-speed measurement by eliminating the need for mechanical scanning depending on TD-OCT measurement.

  As a typical apparatus for performing FD-OCT measurement, there are two types, an SD (Spectral Domain) -OCT apparatus and an SS (Swept Source) -OCT apparatus.

  The SD-OCT apparatus uses broadband low-coherent light, decomposes the interference light into each optical frequency component by a spectroscopic means, and measures the interference light intensity for each optical frequency component with an array-type photodetector or the like. The spectral interference obtained in (1) is obtained by constructing a tomographic image by subjecting the waveform to Fourier transform analysis by a computer.

  On the other hand, the SS-OCT apparatus uses a laser or the like that temporally sweeps the optical frequency as a light source, measures the time waveform of the signal corresponding to the temporal change of the optical frequency of the interference light, and obtains the spectral interference obtained thereby. A tomographic image is constructed by Fourier transforming the intensity signal with a computer.

  Conventionally, it has been studied to apply the optical tomographic imaging apparatus of each of the above methods to in-vivo measurement in combination with an endoscope, and an OCT optical probe that can be inserted into a forceps channel of an endoscope is known. It has been.

  Such an optical probe for OCT scans light emitted from the distal end portion in at least a one-dimensional direction in order to acquire a tomographic image along the distal end portion inserted into the body cavity and a surface to be measured. It consists of an end.

  In Patent Document 1, a sheath to be inserted into a subject, a flexible shaft that is rotatable around an axis extending in the longitudinal direction inside the sheath, and the flexible shaft is covered. It has an optical fiber and a tip optical system that deflects light emitted from the optical fiber at a substantially right angle in the longitudinal direction, and a flexible shaft is rotated via a gear by a motor disposed at the base end, An OCT optical probe that rotates an optical system about an axis is shown.

In Non-Patent Document 2, a MEMS motor is provided in the vicinity of the tip of the OCT optical probe inside the sheath in accordance with the recent development of MEMS (Micro Electro Mechanical Systems) technology, and the tip optical system is used as the output shaft of the MEMS motor. An optical probe for OCT that fixes and rotates a tip optical system about an axis is shown.
Japanese Patent No. 3104984 Optics Express, Vol. 15, Issue 16, pp. 10390-10396 (2007)

  However, as shown in FIG. 11, the conventional OCT optical probe disclosed in Patent Document 1 has a rotary joint between a distal end portion inserted into a body cavity and a proximal end portion that scans emitted light. ing. The rotary joint has a structure in which the optical fiber on the distal end side and the optical fiber on the proximal end side are optically connected while the optical fiber is rotated. Therefore, the optical insertion loss and the optical reflection loss due to the optical axis misalignment, etc. As a result, the measurement accuracy may be degraded. Specifically, when a commercially available rotary joint is used, the sensitivity deterioration due to this rotary joint is 10 to 20 dB.

  As shown in FIG. 12, the OCT optical probe shown in Non-Patent Document 1 can deflect and scan light from the tip without using a rotary joint. However, a MEMS motor is expensive. At the same time, it is difficult to reduce the size, and it may be difficult to pass through the forceps channel diameter of the endoscope. In addition, supplying power to the MEMS motor at the tip requires insulation treatment to prevent electric shock to the human body, and the MEMS motor drive cable blocks light from the tip, affecting image acquisition. May also occur.

  In view of the above circumstances, an object of the present invention is to reduce deterioration in measurement accuracy due to light insertion loss and light reflection loss at the optical connection between the optical fiber on the distal end side and the optical fiber on the proximal end side in the rotary joint. An object of the present invention is to provide an optical probe for OCT that can be realized inexpensively and safely, and an optical tomographic imaging apparatus using the same.

  An optical probe for OCT according to the present invention includes a substantially cylindrical sheath inserted into a subject, an optical fiber disposed in the longitudinal direction in the inner space of the sheath, and light emitted from the tip of the optical fiber. And a driving means for swinging the tip optical system within a range of a predetermined angle around an axis in the longitudinal direction. Here, “substantially cylindrical” does not necessarily mean a strict cylinder from the end to the end with a straight axis as the center, but also has a shape with a gentle curve such as a semispherical tip of the sheath. Is included. Further, the cross-sectional shape does not need to be a mathematically exact circle, and includes an ellipse and the like. The “predetermined angle” can be set within a desired range based on the shape of the measurement target. For example, in the case of a measurement object having a cylindrical shape such as a bronchus, the entire circumference is in the range around the longitudinal axis, and in the case of a flat measurement object such as a stomach wall, 180 degrees with respect to the longitudinal axis. However, the present invention is not limited to this.

  Further, the side surface of the sheath of the OCT optical probe according to the present invention has a light shielding property, and a part of the side surface is provided with a transmission region that transmits light from the deflecting means. May be. Here, the “window” may have any form as long as it forms a light transmission region and a light shielding region at the sheath tip, and specifically, a window at the opaque sheath tip. A structure may be provided, or a light shielding tape may be attached to a part of the transparent sheath tip. Furthermore, it is not necessary to have a strict window shape, and a linear light-blocking region extending in a direction crossing the light scanning direction may be provided.

  Further, the driving means of the OCT optical probe according to the present invention can be a resonance driving system.

  Furthermore, it is desirable that the resonance frequency of the resonance drive is equal to the natural frequency of the flexible shaft.

  The optical tomographic imaging apparatus according to the present invention is characterized in that the OCT optical probe according to the present invention is used in the optical tomographic imaging apparatus of each measurement method as described above. That is, an optical tomographic imaging apparatus according to the present invention includes a light source unit that emits light, a light dividing unit that divides the light emitted from the light source unit into measurement light and reference light, and irradiates the measurement object with the measurement light. Irradiating optical system, combining means for combining the reflected light from the measuring object and the reference light when the measuring object is irradiated with the measuring light, and interference light between the combined reflected light and the reference light. Based on the interference light detection means to detect and the frequency and intensity of the detected interference light, the reflection intensity at a plurality of depth positions of the measurement object is detected, and based on the intensity of the reflected light at each depth position. In an optical tomographic imaging apparatus comprising a tomographic image processing means for acquiring a tomographic image to be measured, the irradiation optical system includes the OCT optical probe of the present invention.

  The OCT optical probe of the present invention can be rotated between the distal end portion and the proximal end portion of the OCT optical probe by swinging the distal optical system at a predetermined angle around the longitudinal axis of the OCT optical probe. There is no need to provide a joint, and the light from the light source means is guided through the optical fiber and directly emitted from the tip optical system.

  Thereby, the light insertion loss and the light reflection loss at the rotary joint do not occur. In addition, since there is no driving means such as a MEMS motor near the tip, the OCT optical probe has a larger outer diameter, the necessity of insulation processing inside the OCT optical probe, and image acquisition using the MEMS motor driving cable. No problems such as the influence of

  Therefore, the OCT probe according to the present invention can realize a reduction in measurement accuracy deterioration due to light insertion loss and light reflection loss at the rotary joint at low cost and safely.

  In addition, since the optical tomographic imaging apparatus according to the present invention is applied with the OCT probe according to the present invention as described above, it is possible to reduce deterioration in measurement accuracy due to light insertion loss and light reflection loss at the rotary joint. It can be realized inexpensively and safely.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, an outline of the optical tomographic imaging apparatus will be described. FIG. 1 is an overall perspective view of an optical tomographic imaging apparatus to which an OCT optical probe 1 of the present invention is applied.

  The present optical tomographic imaging apparatus includes an endoscope 50 including the OCT optical probe 1, a light source device 51 to which the endoscope 50 is connected, a video processor 52, an optical tomography processing device 53, and a video processor 52. And a monitor 54 connected to the.

  As will be described later, the light source device 51 is for irradiating the measurement light L1 to the portion of the measurement target Sb from which the tomographic image P is acquired.

  The endoscope 50 includes an elongated insertion portion 55 having flexibility, an operation portion 56 connected to the proximal end of the insertion portion 55, and a universal cord 57 extending from a side portion of the operation portion 56. And. A light source connector 58 that is detachably connected to the light source device 51 is provided at the end of the universal cord 57. A signal cable 59 extends from the light source connector 58, and a signal connector 60 that is detachably connected to the video processor 52 is provided at an end of the signal cable 59.

  The insertion unit 55 is inserted into a body cavity, for example, and is used for observing the measurement target Sb. The distal end of the insertion portion 55 is formed to be bendable, and the operation portion 56 is provided with an operation knob 61 for bending the distal end of the insertion portion 55. Inside the insertion portion 55, a forceps channel 64, which is a conduit indicated by a broken line in the figure, is provided for inserting a treatment instrument such as the OCT optical probe 1 and forceps along the longitudinal direction thereof. One end of the forceps channel 64 is opened at the distal end of the insertion portion 55 to become a distal end opening portion 64a, and the other end is a forceps insertion port 64b above the operation portion 56. By inserting the OCT optical probe 1 into the forceps insertion port 64b, inserting the forceps channel 64, and projecting the tip of the tip opening 64a, the measurement light L1 can be irradiated onto the measurement target Sb. Note that the distal end of the insertion portion 55 is provided with an observation window (not shown) for observing the measurement target Sb, an illumination window for irradiating illumination light, an air supply for removing dirt, a water supply nozzle, and the like.

  The OCT optical probe 1 includes a long, flexible distal end portion 10, a proximal end portion 20 connected to the proximal end of the distal end portion 10, and an optical fiber 12.

  As described above, the distal end portion 10 is inserted into the body cavity through the forceps channel 64 indicated by a broken line in the figure, and has a length of about 3 m.

  As will be described later, the base end portion 20 incorporates drive means (not shown).

  A control cable 21 extends from the base end portion 20. The end of the control cable 21 is detachably connected to the optical tomography processing device 53 by the control connector 22.

  One end of the optical fiber 12 is detachably connected to the optical tomography processing device 53 by an optical tomographic connector 62, and the other end is inserted through the proximal end portion 20 and the distal end portion 10 and extends to the vicinity of the distal end of the distal end portion 10. ing.

  The OCT optical probe 1 of the present invention will be described in detail.

  FIG. 2 is a view showing the distal end portion 10 of the OCT optical probe 1. FIG. 2A is a schematic diagram showing a cross section of the distal end portion 10 of the OCT optical probe 1, and FIG. 2B is a perspective view of the distal end portion 10 of the OCT optical probe 1.

  The distal end portion 10 of the OCT optical probe 1 has a substantially cylindrical sheath 11, an optical fiber 12 accommodated in the sheath 11 extending in the longitudinal direction, and light emitted from the optical fiber 12 as a subject. And a front-end optical system 15 that condenses the light. The sheath 11 is formed of a cylindrical member having flexibility. In the present embodiment, the distal end of the sheath 11 has a structure closed by a cap 17. The cap 17 is provided with a window 17a through which the measurement light L1 and the reflected light L3 are transmitted.

  On the outer periphery of the optical fiber 12, a flexible shaft 13 made of a close-contact coil in which a metal wire is wound in a closely wound manner is fixed.

  The tip optical system 15 has a substantially spherical shape, deflects the measurement light L1 emitted from the optical fiber 12, condenses the measurement light Sb, and deflects the reflected light L3 from the measurement target Sb. At the same time, the light is condensed and made incident on the optical fiber 12. Here, the focal length of the tip optical system 15 is formed, for example, at a position where the distance D is about 3 mm from the optical axis LP of the optical fiber 12 in the radial direction of the sheath 11. The measurement light L1 emitted from the tip optical system 15 is inclined about 7 degrees from the direction perpendicular to the optical axis LP. The tip optical system 15 is fixed using a fixing member 14 in the vicinity of the light emission position of the optical fiber 12.

  Next, the operation of the OCT optical probe 1 of the present invention will be described.

  As will be described later, the optical fiber 12 and the flexible shaft 13 are mechanically connected to the base end portion 20, and the optical fiber 12 and the flexible shaft 13 have a predetermined angle in the direction of the arrow R1 around the optical axis LP. It swings within the range. As the optical fiber 12 swings, the tip optical system 15 also swings integrally within a predetermined angle range in the direction of the arrow R1 around the optical axis LP. Accordingly, the OCT optical probe 1 scans the measurement target Sb with the measurement light L1 emitted from the tip optical system 15 in the direction of the arrow R1 around the optical axis LP in the range of a predetermined angle in the outer circumferential direction of the sheath 11. Irradiate while. The predetermined angle can be set in a desired range based on the shape of the measuring object Sb. For example, in the case of the measuring object Sb having a cylindrical shape such as a bronchus, the entire circumference is in the range around the longitudinal axis, and in the case of the measuring object Sb having a flat shape such as the stomach wall, the measuring object Sb is around the longitudinal axis. However, the present invention is not limited to this.

  As described above, the cap 17 has the window 17a. By the window 17a, the cap 17 is divided into a transmission region 17b that transmits light and a light-blocking region 17c that blocks light. Specifically, the window 17a is a transparent medium, and the portion other than the window 17a is an opaque medium or a medium having strong reflection scattering (for example, a metal scattering surface).

  Specifically, the window 17a is opened around the optical axis LP, and the measurement light L1 emitted from the tip optical system 15 is scanned wider than the opening angle of the window 17a. The operation of the window 17a will be described later.

  Here, dividing the distal end portion 10 of the OCT optical probe 1 into the transmission region 17b and the light shielding region 17c is not limited to the provision of the window 17a in the cap 17. The cap 17 made of a transparent medium may be configured by attaching two linear light-shielding tapes. Further, the light-shielding region 17c may be provided on the transparent sheath 11 whose tip is closed without providing the cap 17. As configured, the application of light shielding tape, the application of light shielding paint, and a part of the sheath 11 may be made of materials having different diffusivities.

  FIG. 3 is a view showing the base end portion 20 of the OCT optical probe 1. 3A is a cross-sectional view of the first embodiment of the base end portion 20, FIG. 3B is a view showing the operation of the base end portion 20, and FIG. 3C is a cross-sectional view of the base end portion 20 of the second embodiment. is there.

  As shown in FIG. 3A, the first embodiment of the base end portion 20 includes an inner housing 23, an outer housing 24 outside the inner housing, and driving means 30 built in the inner housing 23. Yes. The inner housing 23 fits and fixes the sheath 11. An optical axis direction adjustment knob 25 is attached to the inner housing 23.

  The driving means 30 is fixed to the flexible shaft 13 and has a shaft support member 31 through which the optical fiber 12 passes, a bearing 32 that allows the shaft support member 31 to rotate relative to the inner housing 23, and a shaft support member. A driven gear 33 fixed to 31; a drive gear 34 disposed so as to mesh with the driven gear 33; a motor 35 provided with the drive gear 34 on the output shaft and disposed in the inner housing 23; It comprises an encoder 36 for detecting the rotation angle of the motor 35.

A control signal MC to the motor 35 and a rotation signal RS from the encoder 36 are transmitted by the control cable 21. Specifically, the rotation signal RS includes a rotation clock signal R _CLK and a rotation angle signal R _pos when the motor 35 makes one rotation. When the encoder 36 is an absolute type, the rotation angle signal R _pos is absolute angle information of the motor 35.

  That is, when the output shaft of the motor 35 is swung within a predetermined angle range in the direction of the arrow R2, the shaft support member 31 and the flexible shaft to which the shaft support member 31 is fixed are fixed via the driven gear 33 and the drive gear 34. The flexible shaft 13 and the optical fiber 12 swing in the direction of arrow R3 with respect to the inner housing 23.

  As a result, as shown in FIG. 2B, at the distal end portion 10 of the OCT optical probe 1, the measurement light L1 passes through the distal optical system 15 within a range of a predetermined angle in the direction of arrow R1 around the optical axis LP. Thus, scanning is performed in the outer peripheral direction of the sheath 11.

  As shown in FIG. 3B, the inner housing 23 rotates relative to the outer housing 24 by rotating the optical axis direction adjustment knob 25 in the direction of the arrow R4. As a result, the distal end portion 10 of the OCT optical probe 1 is also rotated in the direction of the arrow R4, and the direction of the optical axis LP of the emitted measurement light L1 can be adjusted.

  As shown in FIG. 3C, the second embodiment of the base end portion 20 includes a permanent magnet 37 disposed on the outer periphery of the shaft support member 31 instead of the driven gear 33, the drive gear 34, the motor 35, and the encoder 36. And an exciting coil 38 disposed so as to surround the permanent magnet 37. In addition, the site | part which has the structure same as 1st Embodiment of the base end part 20 attaches | subjects the same code | symbol, and abbreviate | omits the description.

  The exciting coil 38 may have a configuration in which a coil is wound around a core, or may be a coreless one. An alternating current having a predetermined frequency is supplied to the exciting coil 38 from the control cable 21. The electromagnetic force between the exciting coil 38 and the permanent magnet 37 according to the predetermined frequency causes the permanent magnet 37 to move at a predetermined angle in the arrow R3 direction. Swing within the range of. That is, when the permanent magnet 37 swings in the direction of the arrow R3 within a predetermined angle range, the shaft support member 31, the flexible shaft 13 to which the shaft support member is fixed, and the optical fiber 12 are moved in the direction of the arrow R3. Rocks. At this time, by determining the frequency of the alternating current to be supplied based on the natural frequency determined from the weight of the flexible shaft 13 and the spring constant, the flexible shaft 13 resonates and swings efficiently. Is possible. The sensor 39 monitors the resonance state of the flexible shaft 13. The effect | action by the rocking | fluctuation of this shaft support member 31 is the same as that of the base end part 20 of FIG. 3A, and abbreviate | omits description.

  In the first and second embodiments of the base end portion 20, the shaft support member 31 is swung in the direction of the arrow R3 at the predetermined angle described above. Specifically, the frequency is about 10 Hz to 30 Hz. It is not limited to this. When the processing speed of the tomographic image processing means 150 described later is high, it can be further increased. Further, the frequency is not limited to a fixed value, and can be changed according to the operation speed and resolution of the measurement object Sb. Specifically, the measurement target Sb that operates quickly or the measurement target Sb that does not require high resolution is increased in speed, and the measurement target Sb that operates slowly or the measurement target Sb that requires high resolution may be decreased in speed. Is possible.

  As shown in FIG. 4, the oscillating angle θ of the measurement light L1 emitted from the distal end portion 10 is set to a transmission region 17b of the distal end portion 10 in a region where the measurement light L1 changes at a substantially equal angular velocity, and the other is a light shielding region 17c. It is desirable to scan.

  Next, an optical tomographic imaging apparatus to which the OCT optical probe 1 according to the present invention is applied will be described. FIG. 5 is a diagram showing a schematic configuration of an optical tomographic imaging apparatus 100 to which the OCT optical probe of the present invention is applied.

The optical tomographic imaging apparatus 100 is an optical tomographic imaging apparatus based on SS-OCT measurement, and includes a light source means 110 that emits laser light L, and an optical fiber coupler 2 that splits the laser light L emitted from the light source means. The periodic clock generating means 120 for outputting the periodic clock signal T _CLK from the light divided by the optical fiber coupler 2 and one light divided by the optical fiber coupler 2 are divided into the measurement light L1 and the reference light L2. The light splitting means 3, the optical path length adjusting means 130 for adjusting the optical path length of the reference light L2 split by the light splitting means 3, and the measurement light L1 split by the light splitting means 3 is guided to the measuring object Sb. The OCT optical probe 1 is combined with the reference light L2 and the reflected light L3 from the measurement target Sb when the measurement light L1 from the OCT optical probe 1 is irradiated onto the measurement target Sb. A wave combining unit 4, an interference light detecting unit 140 for detecting the interference light L 4 between the reflected light L 3 combined by the combining unit 4 and the reference light L 2, and the interference light detecting unit 140 A tomographic image processing unit 150 that acquires the tomographic image P of the measurement target Sb by performing frequency analysis of the interference light L4 and a display unit 160 that displays the tomographic image P are provided.

Light source means 110 of the present device is to emit laser light L while sweeping the wavelength at a constant period T _0. Specifically, the light source means 110 includes a semiconductor optical amplifier (semiconductor gain medium) 111 and an optical fiber FB 10, and has a structure in which the optical five FB 10 is connected to both ends of the semiconductor optical amplifier 111. The semiconductor optical amplifier 111 has a function of emitting weak emission light to one end side of the optical fiber FB10 by injecting drive current and amplifying light incident from the other end side of the optical fiber FB10. When a drive current is supplied to the semiconductor optical amplifier 111, a pulsed laser beam L is emitted to the optical fiber FB0 by the optical resonator formed by the semiconductor optical amplifier 111 and the optical fiber FB10.

  Further, a circulator 112 is coupled to the optical fiber FB10, and a part of the light guided in the optical fiber FB10 is emitted from the circulator 112 to the optical fiber FB11 side. The light emitted from the optical fiber FB11 is reflected by a rotary polygon mirror (polygon mirror) 116 via a collimator lens 113, a diffractive optical element 114, and an optical system 115. The reflected light enters the optical fiber FB11 again via the optical system 115, the diffractive optical element 114, and the collimator lens 113.

  Here, the rotating polygonal mirror 116 rotates at a high speed of about 30,000 rpm in the direction of the arrow R1, and the angle of each reflecting surface changes with respect to the optical axis of the optical system 115. Thereby, only the light having a specific wavelength region out of the light dispersed by the diffractive optical element 114 returns to the optical fiber FB11 again. The wavelength of the light returning to the optical fiber FB11 is determined by the angle between the optical axis of the optical system 115 and the reflecting surface. Then, light having a specific wavelength range incident on the optical fiber FB11 is incident on the optical fiber FB10 from the circulator 112, and as a result, laser light L having a specific wavelength range is emitted to the optical fiber FB0 side.

Therefore, when the rotating polygonal mirror 116 rotates at a constant speed in the direction of the arrow R1, the wavelength λ of light incident on the optical fiber FB11 again changes with a constant period as time passes. As shown in FIG. 6, the light source means 110 emits a laser beam L swept from the minimum sweep wavelength λmin to the maximum sweep wavelength λmax at a constant period T ₀ (for example, about 50 μsec).

  The wavelength-swept laser light L is emitted to the optical fiber FB0 side, and the laser light L is further branched by the optical fiber coupler 2 and is incident on the optical fibers FB1 and FB5, respectively. The light emitted to the optical fiber FB5 is guided to the periodic clock generation means 120.

The periodic clock generation means 120 outputs one periodic clock signal _TCLK each time the wavelength of the laser light L emitted from the light source means 110 is swept for one period. The periodic clock generation unit 120 includes optical lenses 121 and 123, an optical filter 122, and a light detection unit 124. Then, the laser light L emitted from the optical fiber FB5 enters the optical filter 122 via the optical lens 121. The laser light L that has passed through the optical filter 122 is detected by the light detection unit 124 via the optical lens 123, and the periodic clock signal T _CLK is output to the tomographic image processing means 150.

  As shown in FIG. 7A, the optical filter 122 has a function of transmitting only the laser beam L having the set wavelength λref and blocking light in other wavelength bands. The optical filter 122 has a plurality of transmission wavelengths. The optical filter 122 has a light transmission period FSR (free spectrum range) in which one transmission wavelength is set in the wavelength band λmin to λmax among the plurality of transmission wavelengths. Therefore, only the laser beam L having the set wavelength λref set in the wavelength band λmin to λmax in which the wavelength of the laser beam L emitted from the light source unit 110 is swept is transmitted, and the laser beam L having the other wavelength band is transmitted. It will be shielded from light.

As shown in FIG. 7B, when the laser light L whose wavelength is periodically swept is emitted from the light source means 110 and the wavelength of the laser light L becomes the set wavelength λref, the periodic clock signal T _CLK is output. Will be. Thus, by generating and outputting the periodic clock signal T _CLK using the laser light L actually emitted from the light source means 110, the laser light L emitted from the light source means 110 has a predetermined wavelength from the start of wavelength sweeping. Even in the case where the time until the light intensity is changed for each period, the interference signal IS in the wavelength band of the constant period T (see FIG. 6) can be acquired from the set wavelength λref. Therefore, the periodic clock signal _TCLK can be output at the timing of acquiring the interference signal IS in the wavelength band assumed in the tomographic image processing means 150, and degradation of resolution can be suppressed.

  The light splitting means 3 is composed of, for example, a 2 × 2 optical fiber coupler, and splits the laser light L guided from the light source means 110 through the optical fiber FB1 into the measurement light L1 and the reference light L2. The light splitting means 3 is optically connected to the two optical fibers FB2 and FB3, respectively, the measuring light L1 is guided by the optical fiber FB2, and the reference light L2 is guided by the optical fiber FB3. The light dividing means 3 in this embodiment also functions as the multiplexing means 4.

  The OCT optical probe 1 is optically connected to the optical fiber FB2, and the measurement light L1 is guided to the OCT optical probe 1. The OCT optical probe 1 irradiates the measuring object Sb from the distal end portion 10 with the measuring light L1, and the reflected light L3 is guided again through the OCT optical probe 1 by the optical fiber FB2.

Further, a rotation signal RS is output from the base end portion 20 to the tomographic image processing means 150.

  The optical path length adjusting means 130 is disposed on the side of the optical fiber FB3 where the reference light L2 is emitted. The optical path length adjusting unit 130 changes the optical path length of the reference light L2 in order to adjust the position where the tomographic image acquisition is started, and reflects the reference light L2 emitted from the optical fiber FB3. A mirror 132; a first optical lens 131a disposed between the reflecting mirror 132 and the optical fiber FB3; and a second optical lens 131b disposed between the first optical lens 131a and the reflecting mirror 132. is doing.

  The first optical lens 131a has a function of converting the reference light L2 emitted from the optical fiber FB3 into parallel light and condensing the reference light L2 reflected by the reflection mirror 132 onto the optical fiber FB3.

  The second optical lens 131b has a function of condensing the reference light L2 converted into parallel light by the first optical lens 131a onto the reflection mirror 132 and making the reference light L2 reflected by the reflection mirror 132 into parallel light. ing.

  Therefore, the reference light L2 emitted from the optical fiber FB3 is converted into parallel light by the first optical lens 131a, and is condensed on the reflection mirror 132 by the second optical lens 131b. Thereafter, the reference light L2 reflected by the reflecting mirror 132 becomes parallel light by the second optical lens 131b, and is condensed on the optical fiber FB3 by the first optical lens 131a.

  Further, the optical path length adjusting means 130 has a base 133 to which the second optical lens 131b and the reflecting mirror 132 are fixed, and a mirror moving means 134 for moving the base 133 in the optical axis direction of the first optical lens 131a. is doing. Then, when the base 133 moves in the direction of arrow A, the optical path length of the reference light L2 is changed.

  As described above, the multiplexing unit 4 is composed of a 2 × 2 optical fiber coupler, and combines the reference light L2 whose optical path length is adjusted by the optical path length adjusting unit 130 and the reflected light L3 from the measurement target Sb. In addition, the light is emitted to the interference light detection means 140 through the optical fiber FB4.

  The interference light detection unit 140 detects the interference light L4 between the reflected light L3 and the reference light L2 combined by the multiplexing unit 4, and outputs an interference signal IS. In this apparatus, the interference light L4 is divided into two by the light splitting means 3, guided to the photodetectors 140a and 140b, and calculated to have a mechanism for performing balance detection. The interference signal IS is output to the tomographic image processing means 150.

  FIG. 8 is a diagram showing a schematic configuration of the tomographic image processing means 150. The tomographic image processing means 150 is realized by executing a tomographic image program read into the auxiliary storage device on a computer (for example, a personal computer). The tomographic image processing unit 150 includes an interference signal acquisition unit 151, an interference signal conversion unit 152, an interference signal analysis unit 153, a tomographic information generation unit 154, an image correction unit 155, and a rotation control unit 156.

The interference signal acquisition unit 151 acquires the interference signal IS for one cycle detected by the interference light detection unit 140 based on the periodic clock signal _TCLK output from the periodic clock generation unit 120. The interference signal acquisition unit 151 acquires the interference signal IS in the wavelength band DT (see FIG. 7B) before and after the output timing of the periodic clock signal _TCLK . Note that the interference signal obtaining means 15 is not critical as long as it acquires the interference signal IS for one period of the output timing of the periodic clock signal T _CLK as a reference, the output timing of the periodic clock signal T _CLK, the wavelength is swept If it is within the band, it may be set immediately after the start of the wavelength sweep or immediately before the end of the wavelength sweep.

  The interference signal conversion means 152 rearranges the interference signals IS obtained by the interference signal acquisition means 151 so as to be equally spaced on the wavenumber k (= 2π / λ) axis. FIG. 9A is a diagram illustrating the interference signal IS input to the interference signal acquisition unit 151. FIG. 9B shows the rearranged interference signal IS. Specifically, the interference signal converting means 152 has a time-wavelength sweep characteristic data table or function of the light source means 110 in advance, and the time-wavelength sweep characteristic data table or the like is used at equal intervals on the wavenumber k axis. The interference signal IS is rearranged so that As a result, when calculating tomographic information from the interference signal IS, high-accuracy tomographic information is obtained by a spectrum analysis method that assumes equal intervals in a frequency space such as Fourier transform processing and processing by the maximum entropy method. Obtainable. The details of this signal conversion method are disclosed in US Pat. No. 5,956,355.

  The distal end portion 10 of the OCT optical probe 1 of the present invention has the window 17a as described above. The measurement light L1 emitted from the tip optical system 15 is scanned wider than the window 17a. If the light shielding region 17c is a medium having strong reflection scattering (for example, a metal scattering surface), the amplitude of the interference signal IS in the light shielding region 17c increases as shown in FIG. 9C. Therefore, when the amplitude of the interference signal IS exceeds the predetermined threshold value ref, it is possible to determine that the measurement light L1 emitted from the tip optical system 15 is in the light shielding region 17c.

  The interference signal analysis unit 153 converts the interference signal IS converted by the interference signal conversion unit 152 into the tomographic information r (z) by a known spectrum analysis technique such as Fourier transform processing, maximum entropy method, Yule-Walker method, and the like. To get.

  Here, when the light shielding region 17c is made of an opaque medium, reflection on the outer peripheral surface of the sheath 11 is reduced. Therefore, when the frequency component corresponding to the outer peripheral surface of the sheath 11 of the interference signal IS after Fourier transform does not exceed the predetermined threshold value, it is determined that the measurement light L1 emitted from the tip optical system 15 is in the light shielding region 17c. It is possible. The same applies to the case where a coating material (for example, carbon made of an infrared light absorbing material) is applied to the outer peripheral surface of the sheath 11 in the light shielding region 17c. Further, when the light shielding region 17c is configured by the inner surface of the sheath having a different diffusivity, the reflection intensity of the inner surface of the sheath 11 changes, so whether the frequency component corresponding to the inner peripheral surface of the sheath 11 exceeds a predetermined threshold value. No, it can be determined that the measurement light L1 emitted from the tip optical system 15 is in the light shielding region 17c.

The rotation control means 156 outputs the control signal MC to the motor 35 and the rotation signal RS from the encoder 36. As described above, the rotation position signal RS includes the rotation clock signal R _CLK and the rotation angle signal R _pos when the motor 35 makes one rotation.

  The tomographic information generating means 154 scans the tomographic information r (z) for one period (one line) acquired by the interference signal analyzing means 153 in the radial direction of the distal end portion 10 of the OCT optical probe 1 (R1 in the figure). Direction), and a tomographic image P as shown in FIG. 10 is generated. The tomographic information generating unit 154 stores the tomographic information r (z) for one line acquired sequentially in the tomographic information accumulating unit 154a.

Here, the tomographic information generating means 154 obtains the tomographic information r (z) from the tomographic information accumulating means 154a for n lines of tomographic information r (z) based on the rotation clock signal _RCLK input to the rotation control means 156. Tomographic image P is generated.

The tomographic information generation means 154 can also read the tomographic information r (z) sequentially from the tomographic information storage means 154a and generate the tomographic image P based on the rotation angle signal R _pos input to the rotation control means 156. .

  Further, the tomographic information generating means 154, based on the amplitude of the interference signal IS as described above, when a phase shift occurs in the swing angle between the distal end portion 10 and the proximal end portion 20 of the OCT optical probe 1. Then, the transmission start position and transmission end position of the distal end portion 10 of the OCT optical probe 1 can be specified, and the tomographic image P can be generated from the tomographic information r (z) accumulated in the tomographic information accumulating means 154a. The same applies to the case where the transmission start position and transmission end position of the distal end portion 10 of the OCT optical probe 1 are specified based on the frequency component corresponding to the outer peripheral surface or inner peripheral surface of the sheath.

  The OCT probe 1 of the present invention is one in which the measurement light L1 from the tip 10 swings and scans within a range of a predetermined angle, and in order to scan the entire circumference of the measurement object Sb, as described above, The optical axis direction adjustment knob 25 of the base end portion 20 is rotated to adjust the direction of the optical axis LP.

  The image quality correction unit 155 performs a sharpening process, a smoothing process, and the like on the tomographic image P generated by the tomographic information generation unit 154.

  The display unit 160 displays the tomographic image P that has been sharpened, smoothed, etc. by the image quality correcting unit 155.

  Therefore, the OCT optical probe 1 and the optical tomographic imaging apparatus 100 using the OCT optical probe 1 of the present invention allow the measurement light L1 emitted from the distal end portion 10 to fall within a predetermined angle around the optical axis LP. Since the rotary scanning is performed, there is no need to provide a rotary joint, and the reduction in measurement accuracy due to light insertion loss and light reflection loss at the rotary joint can be realized inexpensively and safely.

  In addition, since the optical tomographic imaging apparatus 100 according to the present invention is applied with the OCT probe 1 according to the present invention as described above, the measurement accuracy deteriorates due to the light insertion loss and the light reflection loss at the rotary joint. Reduction can be realized inexpensively and safely.

  In the above description, the SS-OCT apparatus has been described as an example of the optical tomographic imaging apparatus to which the OCT optical probe 10 of the present invention is applied. However, the optical tomography apparatus is applied to an SD-OCT apparatus and a TD-OCT apparatus. It is also possible to do.

1 is an overall perspective view of an optical tomographic imaging apparatus to which an OCT optical probe 1 of the present invention is applied. The figure which shows the front-end | tip part 10 of the optical probe 1 for OCT of this invention. Sectional drawing of 1st Embodiment of the base end part 20 of the optical probe 1 for OCT of this invention The figure which shows operation of the base end part 20 of the optical probe 1 for OCT of this invention Sectional drawing of 2nd Embodiment of the base end part 20 of the optical probe 1 for OCT of this invention The figure which shows rocking | fluctuation of the base end part 20 of the optical probe 1 for OCT of this invention. Schematic configuration diagram of an optical tomographic imaging apparatus 100 to which the OCT optical probe 1 of the present invention is applied. The figure which shows the sweep of the wavelength of the light inject | emitted from the light source means 110 The figure which shows the periodic clock signal produced | generated by the periodic clock generation means 120 Schematic configuration diagram of tomographic image processing means 150 The figure which shows the interference signal IS input / output to the interference signal conversion means 152 The figure which shows the tomographic image P produced | generated by the tomographic information production | generation means 154 Schematic diagram showing a conventional OCT optical probe Schematic showing an optical probe for OCT using a MEMS motor

Explanation of symbols

L1 measurement light L2 reference light L3 reflected light L4 interference light P tomographic image Sb measurement object 1 OCT optical probe 3 light splitting means 4 multiplexing means 11 sheath 12 optical fiber 15 tip optical system 17a window 17b transmission area 17c light shielding area 30 drive Means 100 Optical tomographic imaging apparatus 110 Light source means 140 Interference light detection means 150 Tomographic image processing means

Claims (5)

A substantially cylindrical sheath inserted into the subject;
An optical fiber disposed in the longitudinal direction in the internal space of the sheath;
A tip optical system for deflecting light emitted from the tip of the optical fiber toward the subject;
An OCT optical probe comprising: drive means for swinging the tip optical system within a range of a predetermined angle around the longitudinal axis.   2. The optical probe for OCT according to claim 1, wherein a window for dividing light from the deflecting unit into a transmission region for transmitting light and a light shielding region for shielding light is provided on a side surface of the sheath.   3. The OCT optical probe according to claim 1, wherein the driving means is a resonance driving system.   4. The OCT optical probe according to claim 3, wherein a resonance frequency of the resonance drive is equal to a natural frequency of the flexible shaft. Light source means for emitting light;
A light splitting means for splitting light emitted from the light source into measurement light and reference light;
An irradiation optical system for irradiating the measurement object with the measurement light;
A multiplexing means for multiplexing the reflected light from the measurement object and the reference light when the measurement object is irradiated with the measurement light;
Interference light detection means for detecting interference light between the reflected light and the reference light combined;
Based on the frequency and intensity of the detected interference light, the reflection intensity at a plurality of depth positions of the measurement object is detected, and the tomographic image of the measurement object is obtained based on the intensity of the reflected light at each depth position. In an optical tomographic imaging apparatus comprising a tomographic image processing means for acquiring,
An optical tomographic imaging apparatus, wherein the irradiation optical system includes the OCT optical probe according to any one of claims 1 to 4.

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