JP2010014457A - Calibrating jig - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a calibrating jig having simplicity and reproducibility and capable of calibrating a probe type optical tomographic imaging apparatus equipped with an optical probe, having a mounting part on which the optical probe is mounted, emitting light to split it into reference light and measuring light, emitting measuring light from the emitting part of the mounting part, irradiating a measuring target from the optical probe, guiding the reflected light from the measuring target by the optical probe to combine it with the reference light and detecting the coherent light when combination as a coherent signal to obtain the tomographic image of the measuring target. <P>SOLUTION: The calibrating jig 1 is equipped with the holding member 2 capable of being mounted on the mounting part 101 of the optical tomographic imaging apparatus 100 in a freely detachable manner and the reflecting surface 3a held to the holding member 2 and reflecting the measuring light L1 emitted from an emitting part 101a to make the reflected light thereof enter the emitting part 101a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a calibration jig for an optical tomographic imaging apparatus. In particular, the present invention relates to a calibration jig that is mounted on a mounting portion of a probe-type optical tomographic imaging apparatus to which an optical probe is mounted and calibrates the optical tomographic imaging apparatus.

  Conventionally, when a tomographic image is acquired in a body cavity, an optical tomographic imaging apparatus using OCT measurement is sometimes used. The optical tomographic imaging apparatus divides broadband light emitted from a light source into measurement light and reference light by an optical interferometer, and then irradiates the measurement target with the measurement light through an optical axis scanning unit. The measurement light is scanned in one or two-dimensional directions perpendicular to the optical axis at, the reflected light from the measurement object is returned to the interferometer, and the reflected light is combined with the reference light. The reflected light and the reference light The optical tomographic image of the measurement object is acquired based on the interference light intensity. There are two main types of optical axis scanning means: a spatial scanning system that performs linear scanning using a galvano mirror or a polygon mirror by propagating light in a spatial manner, and rotating the output end of the optical fiber by propagating the light through the optical fiber. There is a probe method that performs radial scanning. The fundus OCT device for observing the fundus is representative of the spatial scanning method, and the probe method is a blood vessel OCT device for observing the blood vessel wall through an optical fiber through a blood vessel catheter, or the gastrointestinal wall in combination with an endoscope. There are endoscopic OCT devices. In addition to radial scanning, probe-type optical scanning methods include a method of linearly scanning the probe tip and a method of linear scanning by providing a fine scanning mechanism in the probe.

  There are two types of OCT measurement: TD (Time Domain) -OCT measurement and FD (Fourier Domain) -OCT measurement. In recent years, FD-OCT measurement has attracted attention as a technique that enables high-speed measurement. Two typical types of optical tomographic imaging apparatuses that perform FD-OCT measurement are 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 corresponding to each frequency component with an array-type photodetector or the like. The reflectance in the depth direction, that is, the tomographic information is acquired by performing Fourier transform analysis on the interference intensity signal with a computer.

  The SS-OCT apparatus uses a laser or the like that causes the light source to sweep the frequency temporally, measures the time characteristic waveform of the interference light intensity corresponding to the temporal change in the frequency of the interference light, and uses the computer to calculate the interference intensity signal using a Fourier transform. By converting, the reflectance in the depth direction, that is, tomographic information is acquired.

  Here, in the Fourier domain optical tomographic imaging apparatus, in order to obtain a tomographic image, that is, position information in the depth direction, Fourier transform is performed on the interference intensity signal acquired at equal intervals with respect to the wave number k of the measurement light. However, the data actually acquired by the apparatus is acquired at equal intervals with respect to the time with respect to the spatial displacement of the dispersed wavelength in SD-OCT, and with respect to the time in SS-OCT. This is because the wave number k and the spatial displacement or time are in a non-linear relationship due to the characteristics of the light source, the influence of the constituent devices, etc., and thus the signal after Fourier transform is obtained as a distorted waveform. Therefore, when the space displacement axis or the time axis is correctly converted to the wavenumber axis, it is necessary to correct the distortion and correct the distortion. This creation work of the conversion table for calibration is called calibration.

  In the case of the SS-OCT system, conventionally, two methods have been proposed. One is a calibration method for correcting only the frequency sweep characteristic of the light source having the greatest influence. A method in which a part of the measurement light is transmitted through an interference filter or a fiber Bragg grating, and transmitted light or reflected light is measured by a light receiving element. is there. This method has the disadvantages that expensive equipment is required for evaluation, only distortion of the frequency sweep characteristic of the light source can be corrected, and influences such as dispersion generated by interferometers and probes cannot be corrected. . The other is a calibration method using the optical tomographic imaging apparatus itself without using special equipment, as proposed in Patent Document 1. Specifically, the optical tomographic imaging apparatus monitors the frequency sweep type light source, detects the spectral interference signal as a time signal, obtains the time dependency of the sweep frequency from the spectral interference signal, and then uses this frequency sweep type light source. A calibration method has been proposed for calibrating the time-dependent characteristics of

In the case of the SD-OCT method, the wavelength of light is spatially dispersed (decomposed) by a grating and measured by a detector array. The spatial dispersion due to the grating is linear with respect to the wavelength λ, that is, linear with respect to the reciprocal of the wave number k. Therefore, in the case of SD-OCT, the influence of the effect that the spatial dispersion of the grating becomes nonlinear with respect to the wave number k is the largest. Therefore, in order to correct only this effect, a method of theoretically obtaining the wavelength dispersion of the grating and creating a calibration conversion table is performed. Alternatively, a method of creating a calibration conversion table by measuring a wavelength with respect to spatial displacement using a spectroscope can be easily inferred. However, this method has a drawback that the influence of dispersion or the like generated by an interferometer or a probe cannot be corrected. Here, the dispersion means that the optical path length difference varies depending on the wavelength due to the wavelength dependence of the refractive index in the medium. On the other hand, Patent Document 1 discloses that the present invention can be similarly applied to SD-OCT.
JP2007-101365A

  However, Patent Document 1 does not propose any specific means for using the calibration method described above. In a conventional basic OCT experiment apparatus, a measurement apparatus combining a microscope and an optical axis scanning mechanism is installed on an experiment table, and a measurement sample is placed on the experiment table and measured. Then, as a specific means when using the above calibration method, use the device installed on the experiment table as described above without using the optical probe, and install a reflector instead of the measurement sample. Thus, a method using the above-described calibration method can be easily analogized. However, in this method, calibration is incomplete because wavelength distortion characteristics different from the case of using an optical probe are included due to the influence of an optical component such as a lens used in the measuring apparatus. In addition, simplicity is lost due to the size of the device.

  The optical probe used for actual measurement differs from a measuring device that combines a microscope and an optical axis scanning mechanism installed on an experimental table due to the nature of its application, and is thin and long, and protects from a living body. Therefore, it is very difficult to hold, fix, and finely adjust the optical axis because the protective member is completely separated from the optical scanning mechanism and the operator. Therefore, the optical probe used for the actual measurement is mounted on the mounting portion of the optical tomographic imaging apparatus where the optical probe is detachably optically connected, and some reflection member is disposed near the tip of the optical probe. When irradiating the reflecting member with measurement light, it is difficult for the operator to accurately enter the reflected light reflected from the reflecting member into the optical probe, and there is a possibility that the reproducibility of calibration cannot be obtained. . In addition, since optical probes used for actual measurement have manufacturing variations, it is more difficult to obtain calibration reproducibility when optical probes used for each calibration are different.

  In view of the above circumstances, an object of the present invention is to provide a calibration jig for calibrating a probe-type optical tomographic imaging apparatus with ease and reproducibility.

  In order to solve the above-described problems, a calibration jig according to the present invention includes an optical probe, has a mounting portion that allows the optical probe to be detachably optically connected, and emits light. Is divided into reference light and measurement light, and this measurement light is emitted from the emission part of the mounting part, guided to the optical probe and irradiated to the measurement object, and the reflected light from this measurement object is guided to the optical probe. Calibration of an optical tomographic imaging device that detects interference light when the reflected light and reference light are combined as an interference signal and acquires a tomographic image to be measured using this interference signal A holding jig that can be detachably mounted on the mounting portion, and the measurement light that is held by the holding member and is emitted from the emission portion, and reflects the reflected light. And a reflecting surface that is incident on the emitting portion.

  Here, “removably attachable to the attachment part” does not mean that the attachment part is detachably attached by using a member or mechanism for fixing to the attachment part. It also includes arranging in the vicinity of the mounting portion. The above-mentioned “holding on the holding member” does not mean that the holding member is directly held on the holding member, but also includes the case where the holding member holds the other member. The above-mentioned "reflect the measurement light and make the reflected light enter the emission part" does not mean that only the measurement light is reflected and the reflected light is directly incident on the emission part. For example, the reflected light may be incident on the emission unit between the emission unit and the reflection surface via an optical system such as an optical fiber or a collimator lens.

  In the calibration jig according to the present invention, the holding member may also serve as a reflecting surface.

  Moreover, the calibration jig according to the present invention may include an attenuation unit that attenuates reflected light reflected by the reflecting surface. Here, “attenuating the reflected light” is not limited to attenuating the reflected light itself, but attenuating the reflected light by previously attenuating the measurement light irradiated on the reflecting surface. Is also included.

  In the calibration jig according to the present invention, the reflection surface may also serve as an attenuation part.

  In the calibration jig according to the present invention, the attenuation unit may attenuate the reflected light so that the light intensity of the reflected light reflected by the reflecting surface is in the range of 1 nW to 100 nW.

  According to the calibration jig of the present invention, the optical probe is optically connected, the holding member that can be detachably attached to the mounting portion of the optical tomographic imaging apparatus, and the ejection portion of the mounting portion that is held by the holding member And a reflection surface that reflects the measurement light emitted from the light and makes the reflected light incident on the emission part. Therefore, when an operator calibrates the optical tomographic imaging apparatus, the optical probe is optically imaged. The reflective surface held by the holding member is removed from the mounting portion of the mounting portion only by a simple operation of removing from the mounting portion of the control apparatus and mounting the holding member of the calibration jig of the present invention on the mounting portion. Since the emitted measurement light is reflected and the reflected light is incident on the emission part, the operator can accurately reflect the reflected light of the measurement light on the incident part, and the reproducibility of calibration is improved. .

  In addition, according to the calibration jig of the present invention, the holding member also serves as a reflecting surface, thereby simplifying the configuration of the calibration jig, improving the manufacturing accuracy of the calibration jig, and reproducibility of the calibration. Will improve.

  Further, according to the calibration jig of the present invention, the optical tomographic imaging apparatus detects the interference light to be detected according to the reflectance of the reflecting surface by including an attenuation unit that attenuates the reflected light reflected. The reflected light can be attenuated so as to be within the possible light intensity range.

  Hereinafter, the calibration jig of the optical tomographic imaging apparatus of the present invention will be described in detail with reference to the drawings.

  First, an optical tomographic imaging apparatus and an optical probe that are calibrated using the calibration jig of the present invention will be described. FIG. 1 is a schematic configuration diagram of an optical tomographic imaging apparatus and an optical probe. As an example, the optical tomographic imaging apparatus 100 will be described assuming that a tomographic image to be measured is acquired by SS-OCT measurement.

The optical tomographic imaging apparatus 100 includes a light source unit 110 that emits laser light L, an optical fiber coupler 102 that splits the laser light L emitted from the light source unit 110, and light that has been split by the optical fiber coupler 102. Periodic clock generating means 120 that outputs a periodic clock signal T _CLK , light splitting means 103 that splits one light split by the optical fiber coupler 102 into measurement light L1 and reference light L2, and an optical path length of the reference light L2 The optical path length adjusting means 130 for adjusting the light and the measurement light L1 are guided through the optical probe 200 detachably optically connected to the mounting portion 101 of the optical tomographic imaging apparatus 100, and the measurement target Sb is transmitted from the optical probe 200. The reflected light L3 from the measuring object Sb when irradiated on the optical probe 200 is again guided through the optical probe 200 and combined with the reference light L2. 04, an interference light detection means 140 for detecting the interference light L4 of the reflected light L3 and the reference light L2 combined by the multiplexing means 104, and an interference signal IS detected by the interference light detection means 140. It has a tomographic image acquisition means 150 that acquires the tomographic image P of the measurement object Sb by frequency analysis and displays it.

  The light source unit 110 emits the laser light L while sweeping the wavelength λ at a constant period. The light source unit 110 includes a semiconductor optical amplifier 111 and an optical fiber FB10, and the optical fiber FB10 is connected to both ends of the semiconductor optical amplifier 111. The semiconductor optical amplifier 111 has a function of emitting weak laser light to one end side of the optical fiber FB10 by supplying a drive current and amplifying laser light incident from the other end side of the optical fiber FB10. When a drive current is supplied to the semiconductor optical amplifier 111, the laser light L is emitted to the optical fiber FB0 by the optical resonator formed by the semiconductor optical amplifier 111 and the optical fiber FB10.

  A circulator 112 is coupled to the optical fiber FB10, and light guided into the optical fiber FB10 is emitted from the circulator 112 to the optical fiber FB11. The light emitted from the optical fiber FB11 is reflected by the rotary polygon mirror 116 via the collimator lens 113, the diffractive optical element 114, and the optical system 115. The reflected light is incident on the optical fiber FB11 again via the optical system 115, the diffractive optical element 114, and the collimator lens 113.

  The rotating polygonal mirror 116 rotates at a high speed of, for example, 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. As a result, only the laser light L having a specific wavelength λ determined by the momentary angle between the optical axis of the optical system 115 and the reflecting surface out of the light dispersed by the diffractive optical element 114 returns to the optical fiber FB11 again. It becomes like this. The light of the specific wavelength λ that has returned to the optical fiber FB11 enters the optical fiber FB10 from the circulator 112, and as a result, the laser light L having a specific wavelength region is emitted to the optical fiber FB0. 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.

An optical fiber coupler 102 is connected to the optical fiber FB0, the light is branched into the optical fiber FB1 and the optical fiber FB5, the light emitted to the FB1 is guided to the light dividing means 103, and the light emitted to the FB5 is The light enters the periodic clock generation means 120 that generates a periodic clock _TCLK having a sweep period.

The periodic clock generation unit 120 outputs one periodic clock signal T _CLK to the tomographic image acquisition unit 150 every time the wavelength λ of the laser light L emitted from the light source unit 110 is swept by one period.

  The light splitting means 103 is composed of, for example, a 2 × 2 optical fiber coupler, and the laser light L guided from the light source unit 110 through the optical fiber FB1 is 99: 1 into the measurement light L1 and the reference light L2. Divide by percentage. Specifically, in the present embodiment, as an example, the light amount of the measurement light L1 is divided into 9.9 mW and the light amount of the reference light L2 is divided into 100 μW, but is not limited thereto. The light splitting means 103 is optically connected to each of the two optical fibers FB2 and FB3. The measurement light L1 is guided by the optical fiber FB2 and emitted to the optical probe 200, and the reference light L2 is the optical fiber FB3. And is emitted to the optical path length adjusting means 130. In the present embodiment, the light splitting means 103 also functions as the multiplexing means 104.

  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 acquisition of the tomographic image P is started, and reflects the reference light L2 emitted from the optical fiber FB3. It has a mirror 132, and a first optical lens 131a and a second optical lens 131b arranged between the reflection mirror 132 and the optical fiber FB3.

  The optical path length adjusting unit 130 includes a base 133 on which the second optical lens 131b and the reflection mirror 132 are fixed, and a mirror driving unit 134 that moves the base 133 in the optical axis direction of the first optical lens 131a. Yes. Then, when the base 133 moves in the direction of arrow A, the optical path length of the reference light L2 is changed.

  The multiplexing means 104 is composed of a 2 × 2 optical fiber coupler as described above, and multiplexes the reference light L2 whose optical path length is adjusted by the optical path length adjusting means 120 and the reflected light L3 from the measurement target Sb. . The interference light L4 resulting from this multiplexing is guided through the optical fiber FB4 and enters the interference light detection means 140.

  The interference light detection means 140 detects the interference light L4 between the reflected light L3 combined by the multiplexing means 104 and the reference light L2, and outputs a time characteristic waveform of the light intensity of the interference light L4 as the interference signal IS. Is. In the present embodiment, as an example, the interference light L4 is divided by the multiplexing means 104 at a ratio of 50:50, and is incident on the photodetectors 140a and 140b to have a balance detection. This interference signal IS is A / D converted and output to the tomographic image acquisition means 150.

  In the tomographic image acquisition unit 150, the tomographic image processing unit 151 executes a tomographic image creation program, creates the tomographic information of the measurement target Sb using the A / D converted interference signal IS, and displays the tomographic image on the display unit 152. The image P is displayed. In the present embodiment, the tomographic image acquisition unit 150 is described as being processed and displayed by an externally connected computer as an example, but is processed and displayed inside the optical tomographic imaging apparatus 100. It may be. The processing of the interference signal IS subjected to A / D conversion by the tomographic image processing unit 151 will be described later.

  The housing of the optical tomographic imaging apparatus 100 is provided with a mounting portion 101 that optically connects the optical probe 200 to the optical fiber FB2. The mounting portion 101 has an emission portion 101a that emits the measurement light L1 from the optical fiber FB2. In the present embodiment, as an example, the mounting portion is described as being configured by the optical connector 101 provided in the housing of the optical tomographic imaging apparatus 100, and the emission portion is configured by the central portion 101a of the optical connector 101. It is not limited.

  By attaching the optical probe 200 to the optical connector 101, the optical probe 200 is detachably optically connected to the optical fiber FB2. Thereby, the measurement light L1 emitted from the optical fiber FB2 is emitted to the optical probe 200.

  The optical probe 200 includes a distal end portion 210 that is inserted into a body cavity from a forceps channel or the like of an endoscope, and a drive portion 220. The optical probe 200 incorporates an optical fiber 201 over substantially the entire length and is attached to the optical connector 101, whereby the optical fiber 201 is optically connected to the optical fiber FB2 at the central portion 101a. The optical fiber 201 is divided between the tip portion 210 and the drive portion 220, and the optical fiber 201 on the tip portion 210 side is rotatable with respect to the optical fiber 201 on the drive portion 220 side by an optical rotary joint (not shown). It is connected to become. It is also possible to attach the calibration jig 1 by removing the tip portion 210 and using the rotary joint portion (not shown) as the mounting portion described above.

  A tip optical system 202 is disposed at the tip of the optical fiber 201 to irradiate the measuring object Sb with the measuring light L1 and to make the reflected light L3 from the measuring object Sb enter the optical fiber 201. Here, it is assumed that the measurement target Sb realizes a single reflection point having a delta function shape with respect to the optical axis. The optical fiber 201 on the tip portion 210 side is rotated around the longitudinal axis of the optical fiber 201 (R direction in the figure) by a drive motor (not shown) built in the drive unit 220. Thereby, the measurement light L1 emitted from the tip optical system 202 is scanned around the longitudinal axis of the optical fiber 201 (R direction in the drawing).

The tomographic image processing unit 151 acquires the interference signal IS for one cycle of the sweep cycle detected by the interference light detection unit 140 based on the cycle clock T _CLK from the cycle clock generation unit 120. FIG. 2 shows an interference signal IS input to the tomographic image processing unit 151 when the measurement target Sb is a single reflection point. As described above, the interference signal IS is a time characteristic waveform of the light intensity of the interference light L4. In FIG. 2, the horizontal axis represents time t, and the vertical axis represents the light intensity I of the interference light L4.

  When the measurement object Sb is a single reflection point, the interference signal IS should be a sine wave having a single frequency with respect to the wave number k. However, the wave number k is not linear with respect to the time axis due to the influence of the characteristics of the light source unit 110, components, etc., and the interference signal IS is a sine wave with a single frequency with respect to the time axis as shown in FIG. Don't be. However, as described above, the tomographic image processing unit 151 uses the interference signal IS with respect to the wave number k (= 2π / λ) as shown in FIG. 3 in order to obtain an accurate tomographic image P of the measurement target Sb. Therefore, it is necessary to rearrange so that it becomes a single frequency. For this reason, the tomographic image processing unit 151 has a calibration conversion table or function of time t-wave number k obtained by calibrating the optical tomographic imaging apparatus 100, and for calibration of this time t-wave number k. Using the conversion table or the conversion function for calibration, the interference signal IS is rearranged so as to be equally spaced with respect to the wavenumber axis k, that is, at a single frequency. Accordingly, when the tomographic image processing unit 151 calculates tomographic information from the interference signal IS, the interference signal IS is equally spaced with respect to the wave number k in a frequency space such as a Fourier transform process and a process using the maximum entropy method. High-accuracy tomographic information can be obtained by a spectral analysis method based on the premise that there is a certain one. Details of this conversion method are disclosed in US Pat. No. 5,956,355.

  The tomographic image processing unit 151 uses the converted interference signal IS as an example to obtain tomographic information for one cycle of the sweep cycle of the measurement target Sb by spectral analysis methods such as Fourier transform, maximum entropy method, and Yule-Walker method. get.

  The tomographic image processing unit 151 acquires tomographic information at each irradiation position of the measurement target Sb by scanning the measurement light L1 emitted from the tip of the optical probe 200 around the axis of the optical fiber 201, and obtains the optical probe. Based on a signal from an encoder or the like included in the driving unit 220 of 200, tomographic information of the entire circumference of the measurement target Sb is generated and displayed on the display unit 151 as a tomographic image P.

  Next, a first embodiment of the calibration jig 1 of the present invention will be described. As shown in FIG. 1, the calibration jig 1 is detachably attached to an optical connector 101 that is an example of a mounting portion of the optical tomographic imaging apparatus 100. 4A to 4C are views showing a first embodiment of the calibration jig 1. FIG. The calibration jig 1 is mainly composed of a holding member 2 that can be attached to the optical connector 101 and a reflecting member 3 that reflects the measuring light L1.

  The holding member 2 will be described as being configured to be detachable from the optical connector 101 by having the optical connector 2a that can be fitted to the optical connector 101 in this embodiment. Note that making the holding member 2 detachable from the optical connector 101 is not limited to the holding member 2 having the optical connector 2 a, and the holding member 2 is attached to the housing of the optical tomographic imaging apparatus 100 with screws or the like. The holding member 2 is supported by another supporting member and disposed in the vicinity of the optical connector 101.

  The holding member 2 holds the reflecting member 3 that reflects the measurement light L1 emitted from the central portion 101a of the optical connector 101 that is an example of the emitting portion. The reflection member 3 may be directly held by the holding member 2, but may be held by the holding member 2 indirectly via an adapter.

  The holding member 2 guides the measuring light L1 emitted from the central portion 101a to the reflecting member 3. In the present embodiment, the measurement light L1 is described as being indirectly guided to the reflecting member 3 via the optical fiber 2b connected to the optical connector 2a. However, the present invention is not limited to this. It may be guided through the optical system 2c instead of the fiber 2b, or may be guided through both the optical fiber 2b and the optical system 2c as shown in FIG. 4B. Further, the measurement light L1 may be guided directly to the reflecting member 3.

  As described above, the reflecting member 3 is directly or indirectly held by the holding member 2 and has the reflecting surface 3a that reflects the measurement light L1 emitted from the central portion 101a. The reflecting surface 3a reflects reflected light having a predetermined intensity by polishing or coating. The reflecting member 3 is not particularly limited, and the optical fiber 2b in the calibration jig 1 may also serve as the reflecting member 3 as shown in FIG. 4C. That is, when the optical fiber 2b also serves as the reflecting member 3, the fiber end of the optical fiber 2b becomes the reflecting surface 3a.

  A second embodiment of the calibration jig 1 will be described. As shown in FIGS. 5A to 5D, the reflecting member 3 may have the reflecting surface 3 a by forming the reflecting surface 3 a on a part or all of the holding member 2. 5A shows a case where the reflecting surface 3a is formed on the inner surface 2d of the holding member 2. FIG. 5B shows that the reflecting surface 3a is formed on the outer surface 2e of the holding member 2 by using a part or all of the holding member 2 as a light transmitting material. Is shown. Further, as shown in FIGS. 5C and 5D, an optical system can be disposed at the tip of the optical fiber 2b to polarize the measurement light L1. Other configurations are the same as those of the first embodiment, and the description thereof is omitted.

  A third embodiment of the calibration jig 1 will be described. The calibration jig 1 can also include an attenuation member 4 as shown in FIGS. 6A and 6B. As described above, the light amount of the measurement light L1 is 9.9 mW as an example, but in actual measurement, the reflected light L3 is sufficiently attenuated with respect to the measurement light L1. Specifically, the interference light detection means 140 has the light quantity of the reflected light L3 in the range of 1 nW to 100 nW just before the multiplexing means 104 as an example when the measurement light L1 having the above light quantity is irradiated onto the measurement object Sb. As an example, a light amount detection range is set. Therefore, when the reflectance of the reflection surface 3a is high, the calibration jig 1 includes the attenuation member 4, so that the amount of the reflected light L3 from the reflection surface 3a is attenuated to the light amount detection range of the interference light detection means 140. It becomes possible to make it. In this embodiment, as shown in FIGS. 6A and 6B, the ND filter 4 is described as being inserted between the central portion 101a and the reflecting surface 3a as an attenuation member, but the present invention is not limited to this. When the end face of the optical fiber is the reflecting face 3a, the return of the reflected light L3 can be attenuated to about 4% by cutting the end face obliquely. It is also possible to form the attenuation member 4 by forming irregularities on the surface of the reflective surface 3a and reducing the reflectance of the reflective surface 3a. That is, the reflecting surface 3 a can also serve as the attenuation member 4. In addition, the other structure of 3rd Embodiment is the same as 1st Embodiment, The description is abbreviate | omitted.

  Next, calibration when the first embodiment of the calibration jig 1 shown in FIG. 4A is used will be described. The operator removes the optical probe 200 attached to the optical connector 101 of the optical tomographic imaging apparatus 100 and fits the optical connector 2a of the calibration jig 1 to the optical connector 101, whereby the optical fiber FB2 and the optical fiber are fitted. 2b is optically connected.

  The measurement light L1 emitted from the central portion 101a enters the optical fiber 2b, is guided to the optical fiber 2b, and is applied to the reflecting member 3. The reflected light L3 reflected by the reflecting surface 3a of the reflecting member 3 enters the optical fiber 2b, is guided to the optical fiber 2b and the optical fiber FB2, and enters the multiplexing means 104. Interference between the reference light L2 and the reflected light L3 occurs by the multiplexing means 104, and interference light L4 is generated. This interference light L4 is divided into the multiplexing means 104 and enters the interference light detection means 140, and the interference signal IS Is detected.

  Therefore, the measurement light L1 is reflected only on the reflection surface 3a of the reflection member 3. That is, the calibration jig 1 has a single reflecting surface for the measurement light L1. If the wave number k of the measurement light L1 changes linearly, the interference signal IS becomes a single-frequency time characteristic waveform. Actually, however, due to the influence of the characteristics of the light source unit 110 as shown in FIG. The time characteristic waveform is distorted more than the time characteristic waveform of a single frequency.

Here, when the wave number k of the measuring light L1 changes linearly with respect to a single reflecting surface, the zero point of the interference signal IS (a point having an intermediate intensity between the maximum intensity I _max and the minimum intensity I _min of the interference signal) is , Which are equally spaced with respect to wave number k. Using this property, a calibration conversion table is created in which the time characteristic waveform of the interference signal IS is equally spaced with respect to the wave number k.

Hereinafter, a method of creating a calibration conversion table from the interference signal IS obtained by mounting the calibration jig 1 will be specifically described with reference to FIG. First, as shown in FIG. 7, the wave number k at each zero point of the interference signal IS is k ₀ , k ₁ ,..., K _n-1 (n is the number of zero points in the sweep cycle), and the wave number k _0, k _1, ···, time corresponding to the _{k n-1 t 0, t} 1, ···, be with t _n-1 and symbols. As a method for obtaining the times t ₀ , t ₁ ,..., T _n−1 , for example, there is a method of estimating the zero point by linearly approximating between the two nearest points that cross the zero point. In this case, the interference signal IS is subjected to Fourier transform processing, zero-padded on the high frequency side of the obtained data, and then subjected to inverse Fourier transform to increase the number of data of the interference signal IS. It is also possible to estimate the zero point with high accuracy by performing linear approximation between the two points. Further, the method for obtaining the times t ₀ , t ₁ ,..., T _n-1 is not limited to linear approximation, and can be estimated by approximation with a spline.

Thus, based on the zero point which is estimated, each of the _{(t m, k m) (} m = n-1, ···, n-1), the horizontal axis t, and the vertical axis is the k, FIG. as shown in 8A, k _m is plotted as equal intervals. That is, with the position of k _{n-1 on} the vertical axis being 1, the points k ₀ to k _n-2 are plotted so as to equally divide between 0 and 1. Then, thus obtained the _{(t m, k m) (} m = 0,1, ···, n-1) between, for example, by interpolating the cubic spline interpolation, shown in FIG. 8B Such a calibration conversion table is obtained. The interpolation method is not particularly limited.

  Moreover, in this embodiment, although the calibration using 1st Embodiment of the jig | tool 1 for calibration shown by FIG. 4A was demonstrated, between a light emission part 101a and the reflective surface 3a, a light transmissive member etc. If the interference signal IS has a plurality of reflection surfaces, the interference signal IS is Fourier-transformed, and the peak portion corresponding to the reflection on the reflection surface 3a of the Fourier-transformed interference signal IS is cut out and reversed. The above-described calibration may be performed based on the interference signal IS obtained by Fourier transform. Furthermore, the calibration using the calibration jig 1 of the present invention is not limited to the above-described method for estimating the zero point, and the calibration method described in JP-A-2007-101365 can also be used. is there.

  In the present embodiment, the optical tomographic imaging apparatus 100 has been described as an SS-OCT apparatus, but the present invention is not limited to this. The calibration jig 1 is applied to an SD-OCT apparatus, and a calibration conversion table is created in which the wavelength characteristic waveform of the light intensity of the interference light L4 obtained by the SD-OCT apparatus is equidistant from the wave number. It is also possible.

  Therefore, the calibration jig 1 of the present invention reflects the measurement light L1 emitted from the emission unit 101a simply by the operator mounting the calibration jig 1 on the installation unit 101 of the optical tomographic imaging apparatus 100. The surface 3a can be reflected by the emitting portion 101a, and the optical tomographic imaging apparatus 100 can be calibrated while being simple and reproducible.

Schematic configuration diagram of optical tomographic imaging device and optical probe The figure which shows the interference signal IS input into a tomographic image process part Diagram showing the rearranged interference signal IS The figure which shows 1st Embodiment of the jig | tool for calibration The figure which shows 1st Embodiment of the jig | tool for calibration The figure which shows 1st Embodiment of the jig | tool for calibration The figure which shows 2nd Embodiment of the jig | tool for calibration. The figure which shows 2nd Embodiment of the jig | tool for calibration. The figure which shows 2nd Embodiment of the jig | tool for calibration. The figure which shows 2nd Embodiment of the jig | tool for calibration. The figure which shows 3rd Embodiment of the jig | tool for calibration The figure which shows 3rd Embodiment of the jig | tool for calibration The figure which shows the interference signal at the time of mounting | wearing with the jig | tool 1 for calibration. The figure which shows the conversion table for calibration The figure which shows the conversion table for calibration

Explanation of symbols

IS interference signal L laser beam L1 measurement beam L2 reference beam L3 reflected beam L4 interference beam P tomographic image Sb measurement object 1 calibration jig 2 holding member 3 reflecting member 3a reflecting surface 4 attenuation unit, ND filter 100 optical tomographic imaging apparatus 101 mounting part, optical connector 101a emitting part, central part 200 optical probe

Claims (5)

An optical probe, and a mounting portion for optically connecting the optical probe in a detachable manner, emitting light, dividing the emitted light into reference light and measurement light, and supplying the measurement light to the mounting portion The light is emitted from the emission part, guided to the optical probe and irradiated to the measurement object, and the reflected light from the measurement object is guided to the optical probe and combined with the reference light, and the reflected light and the A calibration jig used to calibrate an optical tomographic imaging apparatus that detects interference light when combined with reference light as an interference signal and acquires a tomographic image of the measurement object using the interference signal. And
A holding member that can be detachably mounted on the mounting portion;
A calibration jig, comprising: a reflection surface that is held by the holding member and reflects the measurement light emitted from the emission unit and causes the reflected light to enter the emission unit.   The calibration jig according to claim 1, wherein the holding member also serves as the reflecting surface.   The calibration jig according to claim 1, further comprising an attenuation unit that attenuates reflected light reflected by the reflection surface.   The calibration jig according to claim 3, wherein the reflection surface also serves as the attenuation portion.   The said attenuation part attenuates the said reflected light so that the light intensity of the reflected light reflected by the said reflective surface may become the range of 1nW-100nW, The Claim 3 or 4 characterized by the above-mentioned. Calibration jig.

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