WO2015025932A1 - Optical probe and optical measurement method - Google Patents

Abstract

Provided are an optical measurement method whereby it is possible to measure the distribution of lipids in blood vessels with low noise, and an optical probe which is suited to use in such a method. An optical probe (10) comprises: an optical fiber (11) which transmits light between a proximate end (11a) and a distal end (11b); an optical connector (12) which is connected to the optical fiber (11) at the proximate end (11a); a condensing optical assembly (13) and a polarizing optical assembly (14) which are optically connected to the optical fiber (11) at the distal end (11b); a cap (15) which encases the condensing optical assembly (13) and the polarizing optical assembly (14); and a support tube (16) and a jacket tube (17) which envelope the optical fiber (11) and extend along the optical fiber (11).

Description

Optical probe and optical measurement method

The present invention relates to an optical probe used for measurement using an optical coherence tomography (OCT) technique and an optical measurement method using the method.

Optical coherence tomography (OCT) is known as a technique for measuring the tomographic structure of the lumen of a luminal object such as a blood vessel, and is inserted into the lumen of the object for this OCT measurement. An optical probe to be used is also known (see Patent Document 1). For OCT measurement, a graded index optical fiber connected to the tip (distal end) of a single-mode optical fiber is made to function as a lens so that the working distance is longer than 1 mm and the spot size is smaller than 100 μm. Thus, an object having an inner radius larger than 1 mm can be optically measured with a spatial resolution finer than 100 μm.

OCT measurement is used when diagnosing a lesion in a blood vessel and selecting a treatment method. When the lesion is subjected to OCT measurement, a tomographic image of the lesion is obtained. In the tomographic image, a site that strongly scatters light within the lesion is bright, and a site that scatters light only weakly is displayed in a single tone with a dark gradation. Since the pattern of the light / dark distribution of this image varies depending on the lesion, it is known that the type of lesion can be estimated to some extent from the light / dark pattern of the image (see Non-Patent Document 1).

Further, in the OCT apparatus using the conventional optical probe, it is sometimes difficult to identify the type of lesion, for example, it is difficult to distinguish between a lipid-rich plaque and a calcified lesion (fibrocalcificplaque).

As described in Non-Patent Document 1, lipid lesions are characterized by dark gradations and unclear outlines, and calcified lesions are characterized by dark gradations and clear outlines. However, since the gradation of the gradation is relative, it is difficult to make a judgment if there are variations due to individual differences or measurement conditions. Also, regarding the clarity of the outline, since there are various patterns of actual lesions, it is often difficult to judge this.

As a method of solving the above problems, OCT measurement is performed using light having a wavelength of 1.6 μm to 1.8 μm and an optical probe designed to operate at this wavelength, and the spectrum is analyzed to analyze the lipid. A method of acquiring distribution information as image information is known (see Patent Document 3).

US Pat. No. 6,445,939 US Patent Application Publication No. 2002/0151823 Japanese Patent No. 5,120,509

W. M. Suh, Circ CardiovascImaging. 2011; 4: 169-178

However, in the prior art described in Patent Document 3, it is necessary to pay close attention to prevent air from entering when a buffer fluid such as water, dextran aqueous solution, or silicone oil is filled in the jacket tube. When bubbles are mixed, the bubbles scatter light and become noise in OCT measurement.

The present invention has been made to solve the above-mentioned problems, and is an optical measurement method capable of measuring lipid distribution in blood vessels with low noise, and suitable for use in such a method. An object is to provide an optical probe.

を満たす光プローブを用い、光源から発せられた光を光分岐部で２分岐して照明光および参照光として出力し、前記照明光を前記光ファイバの前記近位端に入射させ前記遠位端から出射させて対象物に照射し、その照射に伴い前記対象物で生じた後方反射光を前記光ファイバの前記遠位端に入射させ前記近位端から出射させて光検出器に導くとともに、前記参照光をも前記光検出器に導いて、前記後方反射光と前記参照光とによる干渉光を前記光検出器により検出し、前記干渉光を分析部により分析することを特徴とする。 An optical measurement method according to an aspect of the present invention includes an optical fiber that transmits light between a proximal end and a distal end, an optical connector that is connected to the optical fiber at the proximal end, and A condensing optical system connected to the optical fiber at a distal end and collecting light emitted from the distal end of the optical fiber; and connected to the optical fiber at the distal end; A deflection optical system for deflecting light emitted from the distal end; a cap having a thickness b surrounding the deflection optical system; and extending along the optical fiber so as to surround the optical fiber; A jacket tube that is rotatable with respect to the optical connector, the condensing optical system, the deflection optical system, and the cap, and is filled with a gas inside, and the optical fiber emits light at a one-side angle φ Condensing optics N ₀ the refractive index of the center _is a graded index lens having a refractive index of the peripheral edge has a n _1, a refractive index difference ^{_{Δ = √ (n 0 2 -n}} 1 2), the deflecting optical system is the radius a, deflects light at an angle of 2θ with respect to the propagation axis of the optical fiber, the cap has a thickness b, θ ≧ 39 degrees, and the following formula (1)

The light emitted from the light source is bifurcated at the light branching section and output as illumination light and reference light, and the illumination light is incident on the proximal end of the optical fiber and the distal end And irradiating the object by emitting from the back reflected light generated by the object incident on the distal end of the optical fiber and emitting from the proximal end to guide the photodetector, The reference light is also guided to the photodetector, interference light caused by the backward reflected light and the reference light is detected by the photodetector, and the interference light is analyzed by an analysis unit.

The light source generates light in a wavelength band of 1.6 μm to 1.8 μm, the photodetector detects the interference light in the wavelength band, and the analysis unit analyzes a light attenuation spectrum in the wavelength band. Thus, the analysis result can be obtained as image information.

The optical fiber has a cutoff wavelength shorter than 1.53 μm, and the optical fiber, the condensing optical system, the deflection optical system, and the cap on an optical path coupled to a fundamental mode of the optical fiber And the jacket tube has a light transmittance of −2 dB to 0 dB in a wavelength band of 1.6 μm to 1.8 μm, and each of the optical fiber, the condensing optical system, and the deflecting optical system is made of quartz glass or borosilicate It is made of glass, the cap is made of urethane acrylate or epoxy resin, and the jacket tube is made of polyamide, fluororesin, polyester, or polyolefin.

The analysis unit extracts a spectrum component having an absorption peak in a wavelength range of 1.70 to 1.75 μm from the spectrum of the back reflected light, analyzes lipid distribution information based on the spectrum component, and analyzes the analysis result. Can be obtained as image information.

を満たすことを特徴とする。 An optical probe according to an aspect of the present invention includes an optical fiber that transmits light between a proximal end and a distal end, an optical connector that is connected to the optical fiber at the proximal end, and the distal end A condensing optical system connected to the optical fiber at the end and collecting light emitted from the distal end of the optical fiber; and connected to the optical fiber at the distal end; A deflecting optical system for deflecting light emitted from the distal end, a cap having a thickness b surrounding the deflecting optical system, and extending along the optical fiber so as to surround the optical fiber, the optical fiber, the light A connector, a condensing optical system, the deflecting optical system, and a jacket tube that is rotatable with respect to the cap and filled with a gas therein, and the optical fiber emits light at one side angle φ, Condensing optics Refractive index of the mind n _0, a graded index lens having a refractive index of the peripheral edge has a n _1, a refractive index difference ^{_{Δ = √ (n 0 2 -n}} 1 2), the deflecting optical system radius a And deflects light at an angle of 2θ with respect to the propagation axis of the optical fiber, the cap has a thickness b, θ ≧ 39 degrees, and the following formula (2)

It is characterized by satisfying.

Here, light over a wavelength range of 1.6 μm to 1.8 μm is branched into illumination light and reference light, the object is irradiated with the illumination light, and the object is irradiated with the illumination light. The generated backscattered light and the reference light are caused to interfere with each other and detected by a photodetector, and the spectrum of the light detected by the photodetector is analyzed by an analysis unit to obtain distribution information of the substance inside the object. An optical probe for transmitting the illumination light and the backscattered light during optical measurement acquired as image information, wherein the optical fiber has a cutoff wavelength shorter than 1.53 μm, and An optical optical system, the deflection optical system, and the cap and the jacket tube on the optical path coupled to the fundamental mode of the optical fiber are in a wavelength band of 1.6 μm to 1.8 μm. -2 dB to 0 dB, each of the optical fiber, the condensing optical system and the deflecting optical system is made of quartz glass or borosilicate glass, and the cap is made of urethane acrylate or epoxy resin The jacket tube may be made of polyamide, fluororesin, polyester, or polyolefin.

An optical measurement apparatus according to an aspect of the present invention is configured to irradiate an object with illumination light output from the optical branching unit incident on the proximal end of the optical fiber, exiting from the distal end, and irradiating the object. The back reflected light generated by the object is incident on the distal end of the optical fiber, is emitted from the proximal end, is guided to the photodetector, and the reference light output from the optical branching unit is Is also guided to the light detector, the interference light caused by the back reflected light and the reference light is detected by the light detector, the spectrum of the back reflected light is analyzed by the analysis unit, and the inside of the object is detected. Material distribution information is acquired as image information.

According to the present invention, it is possible to reduce noise when measuring the distribution of lipids in blood vessels.

It is a figure which shows the structure of the OCT apparatus 1 provided with the optical probe 10 of this embodiment. It is a figure which shows the spectrum of the transmittance | permeability of each of a lipid lesion, a normal blood vessel, and lard. It is a figure which shows the structure of the front-end | tip part of the optical probe 10A of the comparative example without the cap 15. FIG. It is a figure which shows the structure of the front-end | tip part of the optical probe 10 of this embodiment with a cap. It is a figure explaining reflection of the light in the front-end | tip part of the optical probe 10 of this embodiment. It is a figure explaining the other form of the reflection of the light in the front-end | tip part of the optical probe 10 of this embodiment.

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 OCT apparatus 1 including an optical probe 10 according to the present embodiment. The OCT apparatus 1 includes an optical probe 10 and a measurement unit 30 and acquires an optical coherence tomographic image of the object 3.

The optical probe 10 includes an optical fiber 11 that transmits light between a proximal end 11a and a distal end 11b, an optical connector 12 that is connected to the optical fiber 11 at the proximal end 11a, and a distal end 11b. A condensing optical system 13 and a deflection optical system 14 that are optically connected to the optical fiber 11, a cap 15 that embeds the condensing optical system 13 and the deflection optical system 14, and an optical fiber that surrounds the optical fiber 11. 11, and a support tube 16 and a jacket tube 17 extending along the line 11. The optical connector 12 is optically connected to an optical probe rotational movement mechanism 38 that is a part of the measurement unit 30. The optical fiber 11 has a cutoff wavelength shorter than 1.53 μm. The optical fiber 11, the condensing optical system 13, the deflecting optical system 14, and the cap 15 and the jacket tube 17 on the optical path coupled to the fundamental mode of the optical fiber 11 are −2 dB in the wavelength band 1.6 μm to 1.8 μm. It has a light transmittance of ˜0 dB.

The optical fiber 11 has a length of 1 to 3 m and is made of quartz glass. The optical fiber 11 has a transmission loss of 2 dB or less, preferably 1 dB or less in the wavelength range of 1.6 μm to 1.8 μm, has a cutoff wavelength of 1.53 μm or less, and operates in a single mode in the above wavelength range. . As such an optical fiber, ITU-TG. 652, G.G. 654, G.G. An optical fiber based on 657 is suitable. In particular, ITU-TG. An optical fiber conforming to 654A or C has a transmission loss as low as 0.22 dB / km or less at a wavelength of 1.55 μm, typically has a pure silica glass core, a low nonlinear optical coefficient, a self-phase modulation, etc. This is particularly preferable because noise due to the nonlinear optical effect can be reduced.

A graded index (GRIN) lens as a condensing optical system 13 is fused and connected to the distal end 11 b of the optical fiber 11. Furthermore, a tilted end surface is formed at the tip of the GRIN lens, and this tilted end surface functions as a deflection optical system 14 (mirror) by reflecting light. As light passes through the condensing optical system 13 and the deflecting optical system 14, the light exits while converging in the radial direction.

The GRIN lens (the condensing optical system 13 and the deflecting optical system 14) is made of quartz glass or borosilicate glass, and has a transmission loss of 2 dB or less in the wavelength range of 1.6 μm to 1.8 μm. The mirror has a structure in which a flat reflecting surface inclined by 35 to 44 degrees with respect to the axis of the GRIN lens is formed on a cylindrical glass. Although this flat reflecting surface can reflect light as it is, it is preferable to increase the reflectance at a wavelength of 1.6 to 1.8 μm by further depositing aluminum or gold on the reflecting surface.

The cap 15 is made of urethane acrylate resin or epoxy resin, and has a transmission loss of 2 dB or less in a wavelength range of 1.6 μm to 1.8 μm. As will be described later, the cap 15 has a refractive index substantially equal to that of the condensing optical system 13, and reduces reflection on the light exit surface of the GRIN lens by being in close contact with the condensing optical system 13, thereby reducing noise in OCT measurement. It has the function to do. The cap 15 mechanically protects the condensing optical system 13 and the deflecting optical system 14 and also has a function of confining air so as to be in contact with the mirror interface of the deflecting optical system 14 and realizing a mirror by total reflection. Have.

The optical fiber 11 is accommodated in the lumen of the support tube 16. The support tube 16 is fixed to the tip of the optical fiber 11 and the optical connector 12. As a result, when the optical connector 12 is rotated, the support tube 16 is also rotated together with the optical connector 12, and the rotational torque is transmitted to the optical fiber 11, and the optical fiber 11, the condensing optical system 13, the deflecting optical system 14, the cap 15 and the support. The tube 16 rotates as a unit. Thereby, compared with the case where only the optical fiber 11 is rotated, the torque loaded on the optical fiber 11 is reduced, and the breakage of the optical fiber 11 due to the torque can be prevented.

It is desirable that the support tube 16 has a thickness of 0.15 mm or more and a Young's modulus of 100 to 300 GPa, which is equivalent to stainless steel. The support tube 16 does not necessarily have to be connected in the circumferential direction, and may have a structure in which about 5 to 20 wires are twisted to adjust flexibility. Such a support tube is disclosed in Patent Document 2.

The optical fiber 11, the condensing optical system 13, the deflecting optical system 14, the cap 15 and the support tube 16 are accommodated in the inner cavity of the jacket tube 17, and can be rotated therein. Thereby, it is prevented that the rotating part contacts the target object 3 and the target object 3 is damaged. The illumination light is emitted from the deflection optical system 14, passes through the cap 15 and the jacket tube 17, and is irradiated onto the object 3.

The jacket tube 17 is made of polyamide (nylon, polyether block amide), fluororesin (FEP, PFA, PTFE), polyester (PET), polyolefin (polyethylene, polypropylene), and has a thickness of 30 to 100 μm. The transparency is such that the transmission loss at a wavelength of 1.6 to 1.8 μm is 2 dB or less. In the OCT measurement, the spatial resolution is usually 30 μm or less, and the reflection of the inner surface and the outer surface of the jacket tube 17 is detected and used for calibration such as dispersion compensation. Therefore, the thickness of the jacket tube 17 is OCT. Thicker than the spatial resolution of the measurement is desirable.

The inner cavity of the jacket tube 17 is filled with gas. As the gas, air, nitrogen, carbon dioxide and the like are preferable because they are inert and easily available.

The measuring unit 30 detects a light source 31 that generates light, a light branching unit 32 that bifurcates the light emitted from the light source 31 and outputs it as illumination light and reference light, and light that has arrived from the light branching unit 32. Detected by the photodetector 33, the optical terminal 34 that outputs the reference light that has arrived from the optical branching unit 32, the reflecting mirror 35 that reflects the reference light output from the optical terminal 34 to the optical terminal 34, and the photodetector 33 The analyzing unit 36 that analyzes the spectrum of the emitted light, the output port 37 that outputs the result of the analysis by the analyzing unit 36, and the optical probe rotational movement mechanism 38 that couples the illumination light that has arrived from the optical branching unit 32 to the optical probe 10. And comprising.

The light output from the light source 31 in the measuring unit 30 is branched into two by the light branching unit 32 and output as illumination light and reference light. The illumination light output from the optical branching unit 32 is incident on the proximal end 11a of the optical fiber 11 through the optical probe rotational movement mechanism 38 and the optical connector 12, guided by the optical fiber 11, and emitted from the distal end 11b. Then, the object 3 is irradiated through the condensing optical system 13, the deflection optical system 14, and the cap 15. Backscattered light generated in response to irradiation of the illumination light to the object 3 is incident on the distal end 11b of the optical fiber 11 through the cap 15, the deflection optical system 14, and the condensing optical system 13, and the optical fiber 11 , Is emitted from the proximal end 11a, and is coupled to the photodetector 33 via the optical connector 12, the optical probe rotating / moving mechanism 38, and the optical branching section 32.

The reference light output from the optical branching unit 32 is emitted from the optical terminal 34, reflected by the reflecting mirror 35, and coupled to the photodetector 33 through the optical terminal 34 and the optical branching unit 32. The back-reflected light from the object 3 and the reference light interfere with each other at the photodetector 33, and the interference light is detected by the photodetector 33. The spectrum of the interference light is input to the analysis unit 36. In the analysis unit 36, the spectrum of the interference light is analyzed, and the distribution of the backscattering efficiency at each point inside the object 3 is calculated. A tomographic image of the object 3 is calculated based on the calculation result (distribution information), and is output from the output port 37 as an image signal. That is, the analysis unit 36 analyzes the spectrum and acquires the analysis result as image information.

In the optical measurement method of the present embodiment, in the measurement unit 30, the light source 31 generates broadband light whose spectrum continuously spreads over a wavelength range of 1.6 μm to 1.8 μm. In this wavelength range, as shown in FIG. 2, the lipid lesion has an absorption peak at a wavelength of 1.70 to 1.75 μm, which is different from normal blood vessels in this respect. Since lard, which is a pure lipid, also has a similar absorption peak, it can be said that this absorption peak is due to lipid. Therefore, by extracting a spectral component having an absorption peak at 1.70 to 1.75 μm, lipid distribution information can be analyzed based on the spectral component. Further, when the object 3 containing lipid is measured, the spectrum of the interference light is affected by absorption by the lipid, and shows a large attenuation at wavelengths of 1.70 to 1.75 μm compared to the adjacent wavelength band. That is, the spectrum of the interference light is a light attenuation spectrum.

Furthermore, since the spectrum of the interference light also has information on the tomographic structure of the object 3, the tomographic analysis of the object 3 is performed by selecting a wavelength band that is less affected by substance absorption and performing Fourier analysis of the spectrum. Structural information is obtained. By analyzing the tomographic structure information and the lipid absorption information together, it is possible to calculate a tomographic image displaying lipid distribution.

In this calculation, since both the absorption of the lipid itself and the lipid distribution affect the spectrum, there can be a plurality of lipid distributions corresponding to one spectrum. However, as described in Non-Patent Document 1, it is known that lipids have a characteristic that the scattering intensity is lower than that of normal blood vessels. Therefore, a solution that best matches this known information is selected. Thus, the lipid distribution can be determined.

Since the optical fiber 11, the condensing optical system 13, the deflecting optical system 14, the cap 15, the jacket tube 17, and the gas filled in the lumen are not all the same material, the refractive indexes are not necessarily equal, Light is reflected and scattered at the interface between the two. It is desirable that such reflected light and scattered light generated at the interface of the optical probe 10 be reflected light having a strength that does not saturate the photodetector 33. Since the reflectance in the range of −100 to −50 dB can be typically measured in the OCT measurement, the reflectance of −50 dB or more can saturate the photodetector 33.

On the other hand, the reflectance generated at the interface with the gas in the optical probe 10 can usually reach -50 dB or more. Therefore, if the mirror of the deflecting optical system 14 is tilted by 45 degrees with respect to the axis of the optical fiber, it is deflected. The light enters perpendicularly to the interface between the cap 15 and the jacket tube 17, and the light reflected backward at the interface can reach the photodetector 33 and cause saturation. In order to prevent this, the inclination of the mirror of the deflection optical system 14 is set to 44 degrees or less. Further, when the tilt of the mirror of the deflection optical system 14 is less than 35 degrees, the reflectance at the interface increases, the OCT illumination light attenuates and the image quality deteriorates, so the mirror angle of the deflection optical system 14 is 35. Set to ~ 44 degrees.

Note that the angle of the mirror is defined as the angle formed with respect to the propagation axis of the optical fiber. If the mirror angle is θ, the deflection angle by the deflection optical system is 2θ.

In addition, when observing the deep part of a luminal object such as a blood vessel, the light is incident in a direction perpendicular to the surface of the object, so that the light propagation distance is shortened and the light from the object is irradiated. The attenuation becomes smaller and the deeper part can be observed. Since the attenuation coefficient of light in a living tissue such as a blood vessel is about 10 [1 / mm] and the observation depth is about 1 mm, if the propagation distance is increased by 2.3%, an increase in light attenuation that cannot be ignored is 1 dB. Arise. Therefore, it is desirable to suppress the increase in distance based on the propagation distance in the case of normal incidence within 2.3%, and for this purpose, the mirror angle is desirably 39 degrees or more.

The cap 15 also has a function of preventing saturation due to reflected light. As shown in FIG. 3, in the case of the comparative example without the cap 15, since the side surface of the GRIN lens which is the deflection optical system 14 is in contact with the gas, strong reflected light is generated on the side surface. The reflected light returns to the GRIN lens again, is reflected by the mirror, is coupled to the optical fiber 11, reaches the photodetector 33, and saturates the photodetector. On the other hand, as shown in FIG. 4, in the present embodiment having the cap 15, reflection at the side surface of the GRIN lens that is the deflection optical system 14 (the interface between the GRIN lens and the cap 15) is suppressed to a low level. The light reflected at the interface with the gas propagates in the cap 15 but does not return to the GRIN lens, so that the photodetector 33 is not saturated.

More specifically, in the configuration diagram shown in FIG. 5, in order that the light reflected at the interface of the cap 15 does not return to the GRIN lens, the radius a of the GRIN lens, the wall thickness b on one side of the cap 15, the inclined end surface of the GRIN lens. It is particularly preferable that the inclination [theta] of the (mirror) satisfies the following expression (3). As such a configuration, for example, the lens radius a = 65 μm, the cap thickness b = 235 μm (a / b = 0.28), and the inclination θ from the central axis of the inclined end surface of the GRIN lens is 41 degrees (cos 2θ = 0.28).
a / b <2 cos (2θ) (3)

Another preferred form is shown in FIG. As shown in FIG. 6, it is assumed that the optical fiber 11 is a single mode fiber and has a one-sided angle φ of the emission angle spread. The GRIN lens has a refractive index distribution in which the refractive index n at a position where the distance from the central axis is x is given by the following equations (4) and (5).

Here, n ₀ is the refractive index on the central axis of the GRIN lens, n ₁ is the refractive index at the outer edge (periphery) of the GRIN lens, and a is the radius of the GRIN lens. The length L of the GRIN lens is substantially equal to the following formula (6).

At this time, the outgoing beam from the core of the optical fiber 11 is substantially parallel light, and the spatial resolution defined by the beam diameter is substantially constant regardless of the observation distance. However, when the optical probe is used for an application limited to use in a specific observation distance range, it is more preferable to finely adjust the lens length so that the beam is most condensed in the observation distance range. In the following discussion, the effect is negligible and can be ignored.

このビームは偏向光学系のミラーで反射され、肉厚ｂのキャップを通って出射するが、キャップの側面（キャップが無い場合はGRINレンズの側面）における気体との界面において強い反射光が生じる。ミラーの角度が４５度に近い場合、この反射光がGRINレンズに戻って上記の半径ｗの範囲に入ると光ファイバ１１のコアに再結合して光検出器３３まで到達し、光検出器の飽和やＯＣＴ測定における雑音を生じさせる。 The light emitted from the core of the optical fiber 11 propagates through the GRIN lens to become substantially parallel light, and forms a beam with a radius w at the tip of the GRIN lens (condensing optical system 13 out of them). The radius w of the beam satisfies the following formula (7).

This beam is reflected by the mirror of the deflecting optical system and exits through the cap having a thickness b, but strong reflected light is generated at the interface with the gas on the side surface of the cap (or the side surface of the GRIN lens when there is no cap). When the angle of the mirror is close to 45 degrees, when this reflected light returns to the GRIN lens and enters the range of the radius w, it recombines with the core of the optical fiber 11 and reaches the photodetector 33, This causes noise in saturation and OCT measurement.

When the angle of the mirror is θ, the light emitted from the central axis of the GRIN lens and reflected by the side surface of the cap (or the side surface of the GRIN lens when there is no cap) is the distance w ′ from the central axis at the tip of the GRIN lens. Will return. The distance w ′ is derived by the following formula (8).

Therefore, by selecting the cap thickness b and the end face angle θ so that w ′ ≧ w, saturation of the photodetector due to reflected light and noise in OCT measurement can be suppressed. Specifically, it is preferable to satisfy the following formula (9).

Typically, since the emission angle of the optical fiber 11 is φ = 0.1 rad and the refractive index difference of the GRIN lens is Δ = 0.21, the end face angle θ is θ = 43 degrees, a = 65 μm, and b is It is preferable to make it thicker than 139 μm.

More preferably, a lubricant such as silicone oil is applied to the side surface of the support tube 16, the side surface of the cap 15, and the inner surface of the jacket tube 17. Thereby, the friction when the support tube 16 and the cap 15 rotate is reduced, the fluctuation of the rotation speed is suppressed low, and an OCT image without distortion is obtained.

DESCRIPTION OF SYMBOLS 1 ... OCT apparatus, 3 ... Object, 10 ... Optical probe, 11 ... Optical fiber, 11a ... Proximal end, 11b ... Distal end, 12 ... Optical connector, 13 ... Condensing optical system, 14 ... Deflection optical system, DESCRIPTION OF SYMBOLS 15 ... Cap, 16 ... Support tube, 17 ... Jacket tube, 30 ... Measuring part, 31 ... Light source, 32 ... Light branching part, 33 ... Optical detector, 34 ... Optical terminal, 35 ... Reflector, 36 ... Analyzing part, 37: Output port, 38: Optical probe rotation movement mechanism.

Claims (6)

An optical fiber that transmits light between a proximal end and a distal end;
An optical connector connected to the optical fiber at the proximal end;
A condensing optical system that is connected to the optical fiber at the distal end and collects light emitted from the distal end of the optical fiber;
A deflection optical system connected to the optical fiber at the distal end and deflecting light emitted from the distal end of the optical fiber;
A cap of wall thickness b surrounding the deflection optical system;
The optical fiber surrounds the optical fiber, extends along the optical fiber, is rotatable with respect to the optical fiber, the optical connector, the condensing optical system, the deflection optical system, and the cap, and is filled with gas. A jacket tube, and
The optical fiber emits light at one side angle φ,
Condensing optical system is a refractive index of the center n _0, a graded index lens having a refractive index of the peripheral edge has a n _1, a refractive index difference ^{_{Δ = √ (n 0 2 -n}} 1 2), the deflection The optical system has a radius a, deflects light at an angle of 2θ with respect to the propagation axis of the optical fiber,
The cap has a thickness b, θ ≧ 39 degrees, and the following mathematical formula (1)

Using an optical probe that satisfies
The light emitted from the light source is branched into two at the light branching section and output as illumination light and reference light,
The illumination light is incident on the proximal end of the optical fiber and emitted from the distal end to irradiate the object, and back-reflected light generated by the object with the irradiation is reflected on the distal end of the optical fiber. The light is incident on the end, is emitted from the proximal end, is guided to the photodetector, and the reference light is also guided to the photodetector, and interference light caused by the backward reflected light and the reference light is caused by the photodetector. Detect
An optical measurement method for analyzing the interference light by an analysis unit. The light source generates light in a wavelength band of 1.6 μm to 1.8 μm,
The photodetector detects the interference light in the wavelength band;
The optical measurement method according to claim 1, wherein the analysis unit analyzes a light attenuation spectrum in the wavelength band and acquires the analysis result as image information. The optical fiber has a cutoff wavelength shorter than 1.53 μm;
The optical fiber, the condensing optical system, the deflecting optical system, and the cap and the jacket tube on the optical path coupled to the fundamental mode of the optical fiber are in the wavelength band of 1.6 μm to 1.8 μm from −2 dB to Having a light transmittance of 0 dB,
Each of the optical fiber, the condensing optical system and the deflection optical system is made of quartz glass or borosilicate glass,
The cap is made of urethane acrylate or epoxy resin,
The optical measurement method according to claim 1, wherein the jacket tube is made of polyamide, fluororesin, polyester, or polyolefin. The analysis unit extracts a spectrum component having an absorption peak in a wavelength range of 1.70 to 1.75 μm from the spectrum of the back reflected light, analyzes lipid distribution information based on the spectrum component, and analyzes the analysis result. The optical measurement method according to claim 1, wherein image information is acquired as image information. An optical fiber that transmits light between a proximal end and a distal end;
An optical connector connected to the optical fiber at the proximal end;
A condensing optical system that is connected to the optical fiber at the distal end and collects light emitted from the distal end of the optical fiber;
A deflection optical system connected to the optical fiber at the distal end and deflecting light emitted from the distal end of the optical fiber;
A cap of wall thickness b surrounding the deflection optical system;
The optical fiber surrounds the optical fiber, extends along the optical fiber, is rotatable with respect to the optical fiber, the optical connector, the condensing optical system, the deflection optical system, and the cap, and is filled with gas. Jacket tube,
With
The optical fiber emits light at one side angle φ,
Condensing optical system is a refractive index of the center n _0, a graded index lens having a refractive index of the peripheral edge has a n _1, a refractive index difference ^{_{Δ = √ (n 0 2 -n}} 1 2), the deflection The optical system has a radius a, deflects light at an angle of 2θ with respect to the propagation axis of the optical fiber,
The cap has a thickness b, θ ≧ 39 degrees, and the following mathematical formula (2)

An optical probe characterized by satisfying Backward generated in response to irradiation of the illumination light to the object by bifurcating light over a wavelength range of 1.6 μm to 1.8 μm into illumination light and reference light, irradiating the object with the illumination light The scattered light and the reference light are caused to interfere with each other and detected by a photodetector, the spectrum of the light detected by the photodetector is analyzed by an analysis unit, and the distribution information of the substance inside the object is used as image information. An optical probe for transmitting the illumination light and the backscattered light during an optical measurement to be acquired;
The optical fiber has a cutoff wavelength shorter than 1.53 μm;
The optical fiber, the condensing optical system, the deflecting optical system, and the cap and the jacket tube on the optical path coupled to the fundamental mode of the optical fiber are in the wavelength band of 1.6 μm to 1.8 μm from −2 dB to Having a light transmittance of 0 dB,
Each of the optical fiber, the condensing optical system and the deflection optical system is made of quartz glass or borosilicate glass,
The cap is made of urethane acrylate or epoxy resin,
The optical probe according to claim 5, wherein the jacket tube is made of polyamide, fluororesin, polyester, or polyolefin.

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