JP2008089349A - Optical tomographic imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically adjust the light path length difference between measuring light and reference light in a desired timing in optical coherence tomography measurement for acquiring a tomographic image by performing the frequency analysis of the interference light of the measuring light and the reference light. <P>SOLUTION: Auxiliary light Lb is emitted from a light source unit 210 at each time when the irradiation position of a measuring target S with the measuring light L1 is minutely moved to be split into auxiliary measuring light Lb1 and auxiliary reference light Lb2 by a light splitting means 3, and the auxiliary reflected light Lb3 from a reflecting film 19 and the auxiliary reference light Lb2 are synthesized by a wave synthesizing means 4. The light intensity of auxiliary interference light Lb4 is detected by a photodetector 247. A real time light path length adjusting part 253 is constituted so as to move the reflecting mirror 22 of a light path length alteration means 220 on the basis of the light intensity of the auxiliary interference light Lb4 so as to allow the light path length of the measuring light L1 + reflected light L3 to coincide with the light path length of reference light L2 at the window incident point 16a of an optical probe 230 being a reference point to adjust the light path length of reference light L. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Conventionally, an ultrasonic tomographic image acquisition device using ultrasonic waves is known as a device for acquiring a tomographic image in a body cavity, but in addition, an optical tomographic image acquisition device using optical interference by low coherence light is used. Has been proposed (see, for example, Patent Document 1). In Patent Document 1, a tomographic image is acquired by time domain measurement, and measurement light is guided into a body cavity by inserting a probe into a body cavity from a forceps port of an endoscope through a forceps channel. It has become so.

  Specifically, after the low-coherence light emitted from the light source is divided into the measurement light and the reference light, the measurement light is irradiated onto the measurement object, and the reflected light from the measurement object is guided to the multiplexing means. . On the other hand, the reference light is guided to the multiplexing means after the optical path length is changed. Then, the reflected light and the reference light are combined by the combining means, and the interference light resulting from the combination is measured by heterodyne detection or the like. Here, time domain measurement is a measurement method that utilizes the fact that interference light is detected when the optical path lengths of the measurement light and the reference light match, and by changing the optical path length of the reference light, The measurement position (measurement depth) is changed.

  By the way, in recent years, frequency domain OCT measurement has been proposed in which an optical tomographic image is acquired at high speed without sweeping the optical path length of the reference light by spatially or temporally separating the interference light (for example, Patent Document 2). 3 or non-patent document 1). As this frequency domain OCT measurement, SD-OCT (Source Domain OCT) measurement that obtains an optical tomographic image by spatially separating the interference light, and optical tomographic image acquisition by temporally separating the interference light. SS-OCT (Swept source OCT) measurement is known.

  In SD-OCT (Source Domain OCT) measurement, the frequency of the light emitted from the light source is spatially dispersed to detect the interference light collectively in time, and usually uses a Michelson interferometer. After emitting broadband low-coherence light from the light source and dividing it into measurement light and reference light, the interference light between the reflected light and reference light when the measurement light is irradiated on the measurement target is decomposed into each frequency component By performing Fourier analysis on the channeled spectrum signal, an optical tomographic image is acquired without scanning in the depth direction.

  SS-OCT (Swept source OCT) measurement divides the coherence light emitted from the light source into measurement light and reference light, and then combines the reflected light and reference light when the measurement light is irradiated onto the measurement object. The optical tomographic image is acquired based on the intensity of the interference light between the reflected light and the reference light. In this SS-OCT measurement, interference light is detected while temporally changing the frequency of light emitted from the light source. For example, laser light emitted from the light source using a Michelson interferometer is used. The interference between the reflected light and the reference light is performed while changing the frequency of. Then, the reflection intensity at the depth position of the predetermined measurement target is detected from the interferogram in the optical frequency domain, and a tomographic image is generated using this.

Thus, in the frequency domain OCT apparatus, the reflectance in each depth direction, that is, the tomographic information can be acquired by performing frequency analysis.
JP 2003-172690 A US Pat. No. 5,565,986 JP-A-11-82817 Optical Technology Contact, 2003, Vol41, No7, p426-p432 “Optical Frequency Scanning Spectrum Interference Microscope” by Mitsuo Takeda

  In the frequency domain OCT apparatus, since the relative position from the reference point can be obtained using the point where the optical path difference is zero as a reference point, in principle, it is necessary to match the optical path lengths of the measurement light and the reference light. Absent. However, in practice, in the region where the optical path length difference is large, the spatial frequency of the interference signal expands, so the optical path length difference that can acquire tomographic information by the spatial resolution or temporal resolution of the photodetector that detects the interference light. The maximum value of is determined. That is, in the SD-OCT apparatus, for example, when a photodiode array is used as a photodetector, the spatial resolution that is the interval of the photodiodes, and in the SS-OCT apparatus, the sampling interval by the photodetector. The optical path length difference range in which tomographic information can be acquired is determined by the time resolution.

  For this reason, at least before acquiring optical tomographic information, it is necessary to adjust the optical path length so that the measurement target is included in the optical path length difference range in which optical tomographic information can be acquired. An optical path length adjusting means for adjusting the optical path length is provided in the optical path of the measurement light or the reference light. Usually, before acquiring the target optical tomographic image, the user sets an appropriate optical path length, acquires the optical tomographic image, and displays the optical tomographic image on the display device. The user visually observes the optical tomographic image and adjusts the optical path length adjusting means by a manual operation so that the measurement target is included in the optical tomographic image. Thereafter, a target optical tomographic image is acquired.

  However, the optical path length of the measurement light or reference light may change due to temperature fluctuations. Further, when a waveguide, such as an optical fiber, is used for guiding measurement light or reference light, the optical path length may change due to bending of the fiber. For this reason, the optical path length changes while the target optical tomographic image is being acquired, and as a result, the acquisition site (depth) of the optical tomographic image is shifted, and the optically symmetric optical tomographic image is acquired well. There are cases where it is not possible.

  Therefore, the present invention detects the interference light of the measurement light and the reference light, and in the optical tomographic imaging apparatus that acquires the optical tomographic information of the measurement object by analyzing the frequency of the detected interference light, at a desired timing, An object of the present invention is to provide an optical tomographic imaging apparatus capable of automatically adjusting the optical path length.

An optical tomographic imaging apparatus of the present invention includes a light source unit that emits light,
Light splitting means for splitting the light emitted from the light source unit into measurement light and reference light;
Multiplexing means for multiplexing the reflected light from the measurement object and the reference light when the measurement light divided by the light dividing means is irradiated on the measurement object;
First interference light detection means for detecting first interference light that is interference light between the reflected light and the reference light combined by the multiplexing means;
In an optical tomographic imaging apparatus, comprising: tomographic information acquisition means for acquiring tomographic information of the measurement object by performing frequency analysis on the first interference light detected by the interference light detection means,
An auxiliary light source unit for emitting auxiliary light;
The light splitting means guides the auxiliary light emitted from the auxiliary light source unit to an optical path in which an optical path length difference between the auxiliary measurement light and the optical path of the reference light is divided into the same optical path as the measurement light. Split into auxiliary reference light to be emitted,
The multiplexing means combines auxiliary reflected light that is reflected light of the auxiliary measurement light divided by the light dividing means and auxiliary reference light,
Second interference light detection means for detecting second interference light that is interference light between the auxiliary reflected light and the auxiliary reference light combined by the multiplexing means;
An optical path length adjusting unit that adjusts an optical path length of the measurement light, the reflected light, or the reference light based on a detection result of the second interference light detecting unit is provided.

  Here, “reflected light reflected by the measurement target” includes light scattered by the measurement target in addition to the reflected light by the measurement target. Further, “auxiliary reference light guided to an optical path in which a difference in optical path length from the optical path of the reference light is prescribed” means that the optical path length is longer or shorter by a predetermined value than the optical path length of the optical path of the reference light. It means the auxiliary reference light that is guided. Note that the optical path length difference between the optical path of the reference light and the auxiliary reference light may be set to an arbitrary value as long as the value is clear. Naturally, the auxiliary reference light guided to the same optical path as the reference light is also included in the “auxiliary reference light guided to the optical path in which the optical path length difference from the optical path of the reference light is defined”.

  The wavelength band of the auxiliary light may not overlap the wavelength band of the light.

  The optical tomographic imaging apparatus may include an optical path separation unit that separates an optical path of the first interference light and an optical path of the second interference light.

  The auxiliary reference light is split into the same optical path as the reference light by the light splitting means, and substantially transmits the reference light provided in the optical path of the reference light and the auxiliary reference light. Further, it may include a second reflecting unit that reflects at least a part of the auxiliary reference light, and a third reflecting unit that reflects the reference light transmitted through the second reflecting unit.

  The second reflecting means may be arranged so as to be movable in the optical path direction.

  If the second interference light detecting means outputs an integrated signal obtained by integrating the second interference light spatially or temporally as a detection result, the second interference light detecting means includes an optical path length changing means for changing the optical path length. The optical path length adjusting unit compares the integrated signals detected by the second interference light detecting unit before and after the change of the optical path length, and adjusts the optical path length based on the comparison result. Also good.

  The optical path length changing means may be provided separately from the optical path length adjusting means, or may be combined with the optical path length adjusting means.

  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 a light dividing unit that divides the light. A multiplexing means for combining the reflected light from the measurement object and the reference light when the measurement light is irradiated on the measurement object, the reflected light and the reference light combined by the multiplexing means First interference light detecting means for detecting the first interference light, which is the interference light, and frequency analysis of the first interference light detected by the interference light detection means to obtain the tomographic information of the measurement object. An optical tomographic imaging apparatus having tomographic information acquisition means for acquiring, comprising: an auxiliary light source unit that emits auxiliary light, wherein the light splitting means uses the auxiliary light emitted from the auxiliary light source unit as the measurement light. Auxiliary measurement divided into optical paths And the auxiliary reference light guided to the optical path in which the optical path length difference between the reference light and the optical path of the reference light is defined, and the multiplexing means is the auxiliary measurement divided by the light dividing means The auxiliary reflected light, which is reflected light, and the auxiliary reference light are combined, and the second reflected light is the interference light between the auxiliary reflected light and the auxiliary reference light combined by the combining means. Second interference light detection means for detecting interference light, and optical path length adjustment means for adjusting the optical path length of the measurement light, the reflected light or the reference light based on the detection result of the second interference light detection means The optical path length can be automatically adjusted at every desired timing, for example, every acquisition of optical tomographic information, and the convenience of the apparatus can be improved.

  When the wavelength band of the auxiliary light does not overlap the wavelength band of the light, the auxiliary interference light and the interference light can be easily separated.

  In the case where the measuring light and the auxiliary measuring light are provided with a first reflecting means that substantially transmits the measuring light and reflects at least a part of the auxiliary measuring light, the first reflecting means is provided. The optical path length difference can be adjusted as a reference point.

  The auxiliary reference light is split into the same optical path as the reference light by the light splitting means, and substantially transmits the reference light provided in the optical path of the reference light and the auxiliary reference light, at least In the case of including the second reflecting means for reflecting a part of the auxiliary reference light and the third reflecting means for reflecting the reference light transmitted through the second reflecting means, the optical path length of the auxiliary reference light And the optical path length of the reference light can be set individually, and the convenience of the apparatus is improved.

  If the second reflecting means is disposed so as to be movable in the optical path direction, the optical path length of the auxiliary reference light and the optical path length of the reference light can be set to a desired distance.

  The second interference light detection means outputs an integrated signal obtained by integrating the second interference light spatially or temporally as a detection result, and comprises an optical path length changing means for changing the optical path length, If the optical path length adjustment unit compares the integrated signal detected by the second interference light detection unit before and after the change of the optical path length, and adjusts the optical path length based on the comparison result, By using the integrated detection value, it is difficult to be affected by noise, and the optical path length can be adjusted more accurately.

  Hereinafter, an optical tomographic imaging apparatus which is a specific first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of an optical tomographic imaging apparatus according to a first embodiment of the present invention.

  The optical tomographic imaging apparatus 200 acquires a tomographic image of a measurement target such as a living tissue or a cell in a body cavity by the above-described SD-OCT measurement, and includes a low coherence light La or the low coherence light La Includes a light source unit 210 that emits auxiliary light Lb whose wavelength regions do not overlap, a light La emitted from the light source unit 210, divided into measurement light L1 and reference light L2, and the auxiliary light Lb and auxiliary measurement light Lb1 and The light is divided by the light dividing means 3, the light dividing means 3 for dividing the light into the auxiliary reference light Lb 2, the optical path length changing means 220 for adjusting the optical path length of the reference light L 2 divided by the light dividing means 3 and the auxiliary reference light Lb 2, and the light dividing means 3. The optical probe 230 that irradiates the measured light L1 and the auxiliary measurement light Lb1 in the direction of the measurement target S, the reflected light L3 reflected by the measurement target S and the reference light L2, and the auxiliary measurement Light combining means 4 for combining the auxiliary reflected light Lb3 reflected by the window 16 of the optical probe 230 and the auxiliary reference light Lb2, and interference light between the reflected reflected light L3 and the reference light L2 combined. L4 is separated from interference light Lb4 between the combined auxiliary reflected light Lb3 and auxiliary reference light Lb2, and the interference light L4 is spatially spectrally detected, and the light intensity of the auxiliary interference light Lb4 is determined. Interference light detection means 240 to detect, tomographic information acquisition section 250 that acquires tomographic information from the detection result of the interference light detection means 240, and an image that generates a tomographic image from the tomographic information acquired by the tomographic information acquisition section 250 The optical path of the reference light L2 based on the light intensity of the auxiliary interference light Lb4 detected by the generation unit 251, the image display unit 252 that displays the tomographic image generated by the image generation unit 251, and the interference light detection unit 240 Real-time optical path length adjustment unit 253 for adjusting the length in real time The has.

  The light source unit 210 has an SLD (Super Luminescent Diode) 211 that emits low-coherent light La having a center wavelength (λc) of 1.1 μm and a spectral full width at half maximum of 90 nm, and the light emitted from the SLD 211 is incident on the optical fiber FB1. An optical system 212, an SLD 213 that emits low-coherence light Lb having a central wavelength of 1.6 μm, an optical system 214 that causes the low-coherence light Lb emitted from the SLD 213 to enter the optical fiber FB5, and an optical fiber FB5. And an optical fiber coupler 215 for introducing the low coherence light Lb propagating through the optical fiber FB5 into the optical fiber FB1.

  The light splitting means 3 is composed of, for example, a 2 × 2 optical fiber coupler, splits the low coherent light La guided from the light source unit 210 through the optical fiber FB1 into the measurement light L1 and the reference light L2, Further, the low coherence light Lb is divided into auxiliary measurement light Lb1 and auxiliary reference light Lb2. The light splitting means 3 is optically connected to the two optical fibers FB2 and FB3, respectively. The measurement light L1 or the auxiliary measurement light Lb1 propagates through the optical fiber FB2, and the reference light L2 or the auxiliary reference light Lb2 Propagates in the optical fiber FB3. The light splitting means 3 in this example also functions as the multiplexing means 4.

  An optical probe 230 is optically connected to the optical fiber FB2, and the measurement light L1 or the auxiliary measurement light Lb1 propagates from the optical fiber FB2 to the optical probe 230. The optical probe 230 is inserted into a body cavity from a forceps opening through a forceps channel, for example, and is detachably attached to the optical fiber FB2 by an optical connector 31.

  The optical probe 230 includes a cylindrical probe outer cylinder 15 having a closed tip, and one optical fiber 13 disposed in an inner space of the probe outer cylinder 15 so as to extend in the axial direction of the outer cylinder 15. And the mirror 17 for deflecting the measurement light L1 emitted from the tip of the optical fiber 13 in the circumferential direction of the probe outer cylinder 15 and the measurement light L1 emitted from the tip of the optical fiber 13 are arranged on the outer circumference of the probe outer cylinder 15. In addition, condensing lenses 18a and 18b for converging light to converge on the measuring object S as the object to be scanned, and a motor 14 for rotating the optical fiber 13 about the axis of the optical fiber 13 as a rotation axis. The optical fiber 13, the condensing lenses 18a and 18b, and the mirror 17 are integrally formed. When the optical fiber 13 rotates, the condensing lenses 18a and 18b and the mirror 17 also rotate. A ring-shaped window 16 that transmits the measurement light L1 is provided at the tip of the probe outer cylinder 15. A reflection film 19 that reflects light having a wavelength of 1.5 μm or more is provided inside the window portion 16.

  On the other hand, optical path length changing means 220 is arranged on the side of the optical fiber FB3 from which the reference light L2 is emitted. The optical path length changing unit 220 changes the optical path length of the reference light L2 in order to adjust the acquisition position of the tomographic image, and reflects the reference light L2 emitted from the optical fiber FB3. It has a first optical lens 21a disposed between the reflection mirror 22 and the optical fiber FB3, and a second optical lens 21b disposed between the first optical lens 21a and the reflection mirror 22.

  The first optical lens 21a has a function of converting the reference light L2 emitted from the core of the optical fiber FB3 into parallel light and condensing the reference light L2 reflected by the reflection mirror 22 onto the core of the optical fiber FB3. ing. The second optical lens 21b condenses the reference light L2 converted into parallel light by the first optical lens 21a on the reflection mirror 22, and also converts the reference light L2 reflected by the reflection mirror 22 into parallel light. have. That is, a confocal optical system is formed by the first optical lens 21a and the second optical lens 21b.

  Accordingly, the reference light L2 emitted from the optical fiber FB3 is converted into parallel light by the first optical lens 21a and is condensed on the reflection mirror 22 by the second optical lens 21b. Thereafter, the reference light L2 reflected by the reflection mirror 22 becomes parallel light by the second optical lens 21b, and is condensed on the core of the optical fiber FB3 by the first optical lens 21a.

  The optical path length changing means 220 further includes a base 23 to which the second optical lens 21b and the reflecting mirror 22 are fixed, and a mirror moving means 24 for moving the base 23 in the optical axis direction of the first optical lens 21a. is doing. When the base 23 moves in the direction of arrow A, the optical path length of the reference light L2 can be changed.

  The multiplexing means 4 is composed of a 2 × 2 optical fiber coupler as described above, and combines the reference light L2 whose optical path length has been changed by the optical path length changing means 220 and the reflected light L3 reflected by the measuring object S. In addition, the light is emitted to the interference light detection means 240 side through the optical fiber FB4.

  On the other hand, the interference light detection means 240 decomposes the reflected light L3 reflected by the multiplexing means 4 and the reflected light L3 of the reference light L2 into spatial components by spatially separating them, A collimator lens 241 that detects a channeled spectrum signal and collimates the interference light L4 emitted from the optical fiber FB4, and a diffraction grating that splits the interference light L4 having a plurality of wavelength bands for each wavelength band 242; a CCD array 244 for detecting the interference light L4 dispersed by the diffraction grating 242 for each wavelength band; and the optical path of the interference light L4 and the auxiliary interference light Lb4 arranged in the optical path of the interference light L4 and the auxiliary interference light Lb4. A dichroic mirror 245 which is an optical path separating means for separating the optical path of the optical path, a condenser lens 246 for condensing the auxiliary interference light Lb4 from which the optical path is separated, and a light intensity of the separated auxiliary interference light Lb4. And a photodetector 247 that. As the dichroic mirror 245, for example, a dichroic mirror that reflects light having a wavelength of 1.5 μm or more and transmits light having a wavelength shorter than 1.5 μm can be used. The output value of the photodetector 247 corresponds to a detection value obtained by spatially integrating the auxiliary interference light Lb4.

  The CCD array 244 is, for example, a CCD array in which photosensors are arranged one-dimensionally or two-dimensionally, and each photosensor detects the interference light L4 dispersed as described above for each wavelength band. It has become.

  The CCD array 244 is connected to a tomographic information acquisition unit 250. The tomographic information acquisition unit 250 is connected to an image generation unit 251. The image generation unit 251 is connected to an image display unit 252 including a CRT or a liquid crystal image display unit. Has been.

  The photodetector 247 is connected to the real-time optical path length adjustment unit 253, and the real-time optical path length adjustment unit 253 is connected to the optical path length adjustment unit 220.

  The tomographic information acquisition unit 250 performs frequency analysis by performing Fourier analysis on the channeled spectrum signal of the interference light L4 detected by the CCD array 244, and acquires tomographic information including reflection information at each depth position. The image generation unit 251 generates a tomographic image based on the acquired tomographic information if the measurement site is slightly shifted. The generated tomographic image is displayed on the image display unit 252.

  Note that the interference light L4 detection method and image generation method in the interference light detection means 240, tomographic information acquisition unit 250, and image generation unit 251 are the same as those in the conventional SD-OCT apparatus, and thus detailed description thereof is omitted. To do. The tomographic information acquisition unit 250, the image generation unit 251, and the real-time optical path length adjustment unit 253 are formed as a computer system such as a personal computer, for example. Details of the real-time optical path length adjustment unit 253 will be described later.

  The operation of the optical tomographic imaging apparatus 200 having the above configuration will be described below. In order to simplify the description, first, a method for acquiring tomographic information and generating a tomographic image using the tomographic information will be described, and then the overall operation of the optical tomographic imaging apparatus 200 will be described.

  The low-coherence light La is emitted from the light source unit 210, and the low-coherence light La is split into the measurement light L1 and the reference light L2 by the light splitting means 3. The measurement light L1 is emitted from the optical probe 230 toward the body cavity and irradiated to the measurement object S. At this time, the measurement light L1 emitted from the optical probe 230 operating as described above scans the measurement object S in one dimension. Then, the reflected light L3 reflected by the measuring object S is combined with the reference light L2 reflected by the reflecting mirror 22, and the interference light L4 between the reflected light L3 and the reference light L2 is detected by the interference light detection means 240. In the tomographic information acquisition unit 250, the detected interference signal is subjected to appropriate waveform compensation and noise removal, and then subjected to Fourier transform, and tomographic information that is reflected light intensity distribution information in the depth direction of the measurement target S Is output to the image generation unit 251 and stored in a memory (not shown).

  After obtaining the tomographic information, rotate the optical fiber 13, the rod lens 18 and the prism mirror 17 by a small angle, and repeat the same operation as above at a position slightly away from the position from which the previous tomographic information was obtained to obtain the tomographic information. To do. In this way, by repeating this operation and acquiring the optical tomographic information at each point where the measuring light L1 is irradiated, the tomographic information of the measuring object S is obtained at each part along the rotation direction of the measuring light L1. These tomographic information are sequentially stored in a memory (not shown) of the image generation unit 251. The tomographic information for one round is stored in the memory of the image generation unit 251 by rotating the irradiation angle of the measuring light L1 once, that is, by scanning the measuring object S with the measuring light L1. Thereafter, by synthesizing these pieces of tomographic information, a tomographic image of a circular sliced tomographic plane can be generated. The tomographic image acquired in this way is displayed on the image display unit 252. For example, by moving the optical probe 230 in the left-right direction in FIG. 1 and causing the measuring object S to scan the measuring light L1 in a second direction orthogonal to the scanning direction, this second It is also possible to obtain a tomographic image of a tomographic plane including the direction.

  Next, the operation of the optical tomographic imaging apparatus 200 will be described step by step from the start of the operation. The user inserts the optical probe 230 into the body cavity of the subject before acquiring a tomographic image. First, by manually moving the base 23 of the optical path length changing means 220 in the direction of arrow A, the optical path is roughly set so that the reference point for measurement, for example, the window incident point 16a is located within the measurable region. Set the length. Thereafter, the optical path length is adjusted in real time immediately before obtaining the tomographic information at each point.

  Hereinafter, an operation for adjusting the optical path length in real time will be described based on the operation of the real-time optical path length adjustment unit 253. FIG. 2 is a graph showing the relationship between the light intensity of interference light of low coherence light and the measurement depth. Usually, the detected value of the light intensity of the interference light of the low-coherence light represents the reflectance of the measurement light at a position where the optical path lengths of the measurement light and the reference light match. For this reason, comparing the detection value of the light intensity of the interference light compares the reflectance of the measurement light at a position where the optical path lengths of the measurement light and the reference light match.

  First, the real-time optical path length adjustment unit 253 emits the low coherence light Lb from the SLD 213 of the light source unit 210. The low coherence light Lb is split by the light splitting means 3 into auxiliary measurement light Lb1 and auxiliary reference light Lb2. The auxiliary measurement light Lb1 is reflected by the reflection film 19 of the window portion 16 of the optical probe 230, and becomes auxiliary reflection light Lb3. The auxiliary reflected light Lb3 is combined with the auxiliary reference light Lb2 reflected by the reflection mirror 22 of the optical path changing unit 220, and the auxiliary interference light Lb4 between the reflected light Lb3 and the auxiliary reference light Lb2 propagates in the optical fiber FB4. Then, the light is reflected by the dichroic mirror 245, condensed by the lens 246, and the light intensity is detected by the photodetector 247.

  The real-time optical path length adjusting unit 253 controls the mirror moving unit 24 of the optical path length changing unit 220 while monitoring the detection value of the light intensity output from the light detecting unit 247, and controls the second optical lens 21b and the reflecting mirror 22. Are moved slightly in the direction of the optical axis of the first optical lens 21a. At this time, if the detection value after the base 23 is moved is larger than the detection value before the base 23 is moved, the base 23 is further moved in the same direction. If the detection value after moving the base 23 is smaller than the detection value before moving, the base 23 is moved in the opposite direction. Such a small movement of the base 23 is repeated, and the base 23 is stopped at a position where the detected value becomes small, that is, a position where the detected value becomes maximum, regardless of which direction is finally moved. By such an operation, the optical path length between the auxiliary measurement light Lb1 + auxiliary reflected light Lb3 and auxiliary reference light Lb2 is set at the reference point where the detection value is always maximized, that is, the window incident point 16a having a high reflectance in this embodiment. Can be matched. Since the optical paths of the auxiliary measurement light, auxiliary reflected light, and auxiliary reference light coincide with the optical paths of the measurement light, reflected light, and reference light, the optical path length of the measurement light + reflected light is referred to at the window incident point 16a. The optical path length of the light also matches.

  As is apparent from the above description, the optical tomographic imaging apparatus 200 monitors the detection value of the light intensity of the auxiliary interference light Lb4 as described above every time the position where the measurement light L1 is irradiated is slightly moved. By changing the optical path length of the auxiliary reference light Lb2 and comparing the detected values, the optical path length of the auxiliary measurement light + auxiliary reflected light and the optical path length of the auxiliary reference light coincide with each other at the window incident point 16a. In addition, by adjusting the optical path length of the auxiliary reference light, the optical path length of the measurement light + reflected light and the optical path length of the reference light can be matched, so that the optical path length of the measurement light, reflected light or reference light is Even if there is a change due to temperature fluctuation or bending of the optical fiber, the optical path length of the measurement light + reflected light and the optical path length of the reference light automatically coincide with each other at the window incident point 16a. Can be obtained satisfactorily.

  Further, since the optical path length is adjusted using the light intensity of the auxiliary interference light Lb4, that is, the integrated value obtained by spatially integrating the auxiliary interference light Lb4, the optical path length is adjusted accurately without being easily affected by noise. Is possible.

  Furthermore, when the light detection unit 247 detects the light intensity of the auxiliary interference light Lb4, it may be configured to output the detection value detected by increasing the light reception time to the real-time optical path length adjustment unit 253. By increasing the light reception time, the influence of errors can be suppressed, and the optical path length can be adjusted more accurately.

  Next, a second embodiment of the present invention will be described. FIG. 3 is a schematic configuration diagram of an optical tomographic imaging apparatus 300 according to the second embodiment of the present invention. In FIG. 3, the same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted unless particularly necessary.

  The optical tomographic imaging apparatus 300 according to the second embodiment transmits the reference light L2 and reflects the auxiliary reference light Lb2 in the incident direction as compared with the optical tomographic image 200 according to the first embodiment described above. The difference is that the dichroic mirror 321 is provided in the optical path length changing means 320, and the other points are basically configured in the same manner as the optical tomographic imaging apparatus 200 according to the first embodiment. .

  The optical path length changing means 320 includes a reflection mirror 22 that reflects the reference light L2, a dichroic mirror 321 that transmits the reference light L2 and reflects the auxiliary reference light Ls5 in the incident direction, and between the dichroic mirror 321 and the optical fiber FB3. A first optical lens 21a, a second optical lens 21b, a second optical lens 21b, a reflection mirror 22, and a base 322 on which a dichroic mirror 321 is disposed; Mirror moving means 323 for moving in the optical axis direction of 21a. The second optical lens 21b and the reflection mirror 22 are fixed to the base 322. Further, the dichroic mirror 321 is configured to be fixed to the base 322 in a state where the distance from the reflection mirror 22 is arbitrarily set. Then, by moving the base 322 in the direction of arrow A, the optical path length of the auxiliary reference light Lb2 and the optical path length of the reference light L2 can be changed.

  The operation of the optical tomographic imaging apparatus 300 will be described step by step from the start of the operation. The user inserts the optical probe 230 into the body cavity of the subject and performs an initial setting of the optical path length before acquiring a tomographic image. In the initial setting, the base 23 of the optical path length changing means 320 is moved in the direction of arrow A by manual operation so that the reference point for measurement, for example, the window incident point 16a is positioned within the measurable region. Set the optical path length to. Thereafter, the optical path length is adjusted in real time immediately before obtaining the tomographic information at each point.

  Hereinafter, an operation for adjusting the optical path length in real time will be described. First, the user fixes the dichroic mirror 321 to the base 322 in a state where the dichroic mirror 321 is disposed at a predetermined position, for example, 0.5 mm before the reflection mirror 22.

  The real-time optical path length adjustment unit 353 emits the low coherence light Lb from the SLD 213 of the light source unit 210. The low coherence light Lb is split by the light splitting means 3 into auxiliary measurement light Lb1 and auxiliary reference light Lb2. The auxiliary reference light Lb <b> 2 is reflected by the dichroic mirror 321 of the optical path length changing unit 320. On the other hand, the auxiliary measurement light Lb1 is reflected by the reflection film 19 of the window portion 16 of the optical probe 230, and becomes auxiliary reflection light Lb3. The auxiliary reflected light Lb3 is combined with the auxiliary reference light Lb2 reflected by the dichroic mirror 321, and the auxiliary interference light Lb4 between the reflected light Lb3 and the auxiliary reference light Lb2 propagates through the optical fiber FB4, and the dichroic mirror 245. The light intensity is detected by the photodetector 247.

  Thereafter, as in the first embodiment, the real-time optical path length adjustment unit 353 moves the position of the dichroic mirror 321 while monitoring the detected value of the light intensity of the auxiliary interference light Lb4, and the optical path of the auxiliary reference light Lb2. By changing the length and comparing the detected values, the auxiliary reference is made so that the optical path length of the auxiliary measuring light Lb1 + auxiliary reflected light Lb3 and the optical path length of the auxiliary reference light Lb2 coincide at the window incident point 16a. The optical path length of the light Lb2 is adjusted. That is, at the window incident point 16a, the position of the dichroic mirror 321 that reflects the auxiliary reference light Lb2 is adjusted so that the optical path length of the auxiliary measurement light Lb1 + auxiliary reflected light Lb3 matches the optical path length of the auxiliary reference light Lb2. . The optical paths of the measurement light L1 and the reflected light L3 coincide with the optical paths of the auxiliary measurement light Lb2 and the auxiliary reflected light Lb3, and the optical path length of the reference light L2 is 2 × 0.5 mm longer than the optical path length of the auxiliary reference light Lb2. The optical path length of the measurement light L1 + reflected light L3 and the optical path length of the reference light L2 coincide with each other 0.5 mm outside the window incident point 16a.

  As is clear from the above description, in the optical tomographic imaging apparatus 200, the optical path length of the auxiliary measurement light Lb1 + auxiliary reflected light Lb3 and the optical path length of 2 × predetermined distance from the reference light L2 at the window incident point 16a. By adjusting the optical path length of the auxiliary reference light Lb2 so that the optical path length of the short auxiliary reference light Lb2 matches, the optical path length of the measurement light L1 + the reflected light L3 and the optical path length of the auxiliary reference light + 2 × predetermined Since the distance can be matched, even if there is a change in the optical path length of the measurement light, reflected light or reference light due to temperature fluctuation or bending of the optical fiber, it is automatically detected from the window incident point 16a. Outside the predetermined distance, the optical path length of the measurement light + reflected light coincides with the optical path length of the reference light, and an optical tomographic image having the measurement symmetry S can be obtained well. Further, since the distance between the reflection mirror 22 and the dichroic mirror 321 can be set to a desired distance in the optical path length changing unit 320, an optical tomographic image of a desired depth of the measurement target S can be acquired.

  Next, a third embodiment of the present invention will be described. FIG. 4 is a schematic configuration diagram of an optical tomographic imaging apparatus 400 according to the third embodiment of the present invention. In FIG. 4, the same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted unless particularly required.

  Compared with the optical tomographic image 200 of the first embodiment described above, the optical tomographic imaging apparatus 400 of the third embodiment causes the auxiliary interference light Lb4 to be incident on the diffraction grating 242 and from the diffraction grating 242. The difference is that a photodetector 442 that detects the light intensity of the split auxiliary interference light Lb4 is provided, and the other points are basically the same as the optical tomographic imaging apparatus 200 of the first embodiment. It is constituted similarly.

  The interference light detection means 440 includes a collimator lens 241 that collimates the interference light L4 emitted from the optical fiber FB4, and a diffraction grating that splits the interference light L4 and auxiliary interference light Lb4 having a plurality of wavelength bands for each wavelength band. 242, a CCD array 244 for detecting the interference light L 4 split by the diffraction grating 242 for each wavelength band, and a photodetector 442 for detecting the light intensity of the auxiliary interference light Lb 4 split by the diffraction grating 242. ing. The photodetector 442 detects an integrated value obtained by spatially integrating the split auxiliary interference light Lb4, and a photodetector having a sufficiently large light receiving area is used.

  Also in the optical tomographic imaging apparatus 400 according to the present embodiment, the position of the measurement light L1 is slightly moved to detect the auxiliary interference light Lb4 detected by the photodetector 442 before acquiring the tomographic information. While monitoring the intensity detection value, the optical path length of the auxiliary reference light Lb2 is changed, and the magnitude of the detection value is compared to thereby compare the optical path length of the auxiliary measurement light + auxiliary reflected light and the auxiliary reference light at the window incident point 16a. By adjusting the optical path length of the auxiliary reference light so that the optical path lengths of the measurement light and reflected light can be matched with the optical path length of the reference light. Or, even if the optical path length of the reference light changes due to temperature fluctuation or bending of the optical fiber, the optical path length of the measurement light + reflected light and the optical path length of the reference light automatically at the window incident point 16a. And the optical tomographic image of measurement symmetry S can be acquired well. You can. Further, a separating unit that separates the interference light L4 and the auxiliary interference light Lb4 is unnecessary. Instead of the optical path length changing means 220, the optical path length changing means 320 shown in FIG.

  In the present embodiment, the light intensity that is an integrated value obtained by spatially integrating the auxiliary interference light Lb4 is detected using the photodetector 442, and the optical path length is adjusted based on the light intensity. For example, instead of the photodetector 442, a CCD array may be used to acquire tomographic information from the output of the CCD array, and the optical path length may be adjusted based on the tomographic information.

  Next, a fourth embodiment of the present invention will be described. FIG. 5 is a schematic configuration diagram of an optical tomographic imaging apparatus 600 according to the fourth embodiment of the present invention. In FIG. 5, the same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted unless particularly necessary.

  The optical tomographic imaging apparatus 600 according to the fourth embodiment acquires a tomographic image to be measured by the above-described SS-OCT measurement as compared with the optical tomographic image 200 according to the first embodiment described above. Certain points are different, and other points are basically configured in the same manner as the optical tomographic imaging apparatus 200 according to the first embodiment.

  The optical tomographic imaging apparatus 600 includes a light source unit 610 that emits light Ls and auxiliary light Lb in which the wavelength regions of the light Ls do not overlap, a light Ls emitted from the light source unit 610, a measurement light Ls1, and a reference light Ls2. And splitting the auxiliary light Lb into auxiliary measurement light Lb1 and auxiliary reference light Lb2, and adjusting the optical path lengths of the reference light Ls2 and auxiliary reference light Ls2 divided by the light dividing means 63 The optical path length adjusting means 220, the optical probe 230 for irradiating the measuring light Ls1 and the auxiliary measuring light Ls2 divided by the light dividing means 63 in the direction of the measuring object S, and the reflected light Ls3 reflected by the measuring object S A light combining means 64 for combining the auxiliary reflected light Lb3 and the auxiliary reference light Lb2 which are combined with the light Ls2 and the auxiliary measuring light Lb1 reflected by the window 16 of the optical probe 230, and the combined reflected light Ls3. And reference light Ls2 The auxiliary reflected light Lb3 combined with the interfering light Ls4 and the auxiliary interference light Lb4 between the auxiliary reference light Lb2 are separated, the interference light Ls4 is temporally spectrally detected, and the auxiliary interference light Lb4 is detected. Interference light detection means 640 for detecting the light intensity of the light, tomographic information acquisition part 650 for acquiring tomographic information from the detection result of the interference light detection means 640, and tomographic image from the tomographic information acquired by the tomographic information acquisition part 650 Based on the light intensity of the auxiliary interference light Lb4 acquired by the interference light detection means 640 and the image display unit 252 that displays the tomographic image generated by the image generation unit 251 A real-time optical path length adjustment unit 253 that adjusts the optical path length of the light Ls2 in real time.

  The light source unit 610 includes a frequency swept laser light source that emits the laser light Ls while sweeping the frequency at a constant period, an SLD 617 that emits a low coherence light Lb whose wavelength band does not overlap with the wavelength band of the laser light Ls, and the SLD 617 An optical system 618 for causing the emitted low coherence light Lb to enter the optical fiber FB61, and an optical fiber coupler 61 for introducing the laser light Ls emitted from the frequency swept laser light source into the optical fiber FB61. ing.

As shown in FIG. 6, the frequency f of the laser light Ls is a center frequency fc and is periodically swept within a predetermined frequency sweep width Δf. Therefore, the frequency f sweeps in a sawtooth shape between the frequency f ₀ (fc−Δf / 2) and the frequency fc + Δf / 2.

  For convenience of explanation, the description is made by paying attention to the change in the frequency f of the laser light Ls. However, since the frequency f = the speed of light c / wavelength λ, the frequency f of the laser light Ls is swept at a constant period. Is synonymous with sweeping the wavelength λ of the laser beam Ls at a constant period, and the center frequency fc of the laser beam Ls in FIG. 6 is the center wavelength λsc when the wavelength λ is swept, and the frequency sweep The width Δf is the wavelength sweep width Δλs. Moreover, although the case where the frequency sweeps in a sawtooth shape is illustrated in FIG. 6, the frequency may be swept in a wave shape.

  The frequency swept light source of the light source unit 610 includes a semiconductor optical amplifier (semiconductor gain medium) 611 and an optical fiber FB70, and the optical fiber FB70 is connected to both ends of the semiconductor optical amplifier 611. The semiconductor optical amplifier 611 has a function of emitting weak emission light to one end side of the optical fiber FB70 by injecting drive current and amplifying light incident from the other end side of the optical fiber FB70. When a drive current is supplied to the semiconductor optical amplifier 611, a sawtooth laser beam Ls is emitted to the optical fiber FB61 by an optical resonator formed by the semiconductor optical amplifier 611 and the optical fiber FB70. .

  Further, an optical branching device 612 is coupled to the optical fiber FB70, and a part of the light guided in the optical fiber FB70 is emitted from the optical branching device 612 to the optical fiber FB71 side. Light emitted from the optical fiber FB71 is reflected by a rotary polygon mirror (polygon mirror) 616 via a collimator lens 613, a diffraction grating 614, and an optical system 615. The reflected light is incident on the optical fiber FB71 again via the optical system 615, the diffraction grating 614, and the collimator lens 613.

  Here, the rotating polygonal mirror 616 rotates 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 615. As a result, only the light in a specific frequency region out of the light split by the diffraction grating 614 returns to the optical fiber FB71 again. The frequency of light returning to the optical fiber FB71 is determined by the angle between the optical axis of the optical system 615 and the reflecting surface. Then, light in a specific frequency range incident on the optical fiber FB71 is incident on the optical fiber FB70 from the optical splitter 612, and as a result, laser light Ls in a specific frequency range is emitted to the optical fiber FB61 side. .

  Therefore, when the rotary polygon mirror 616 rotates at a constant speed in the direction of the arrow R1, the wavelength λ of the light incident on the optical fiber FB71 again changes with a constant period as time passes. In this way, the wavelength-swept laser beam Ls is emitted from the light source unit 610 to the optical fiber FB61 side.

  The light splitting means 63 is composed of, for example, a 2 × 2 optical fiber coupler, and splits the light Ls guided from the light source unit 610 through the optical fiber FB61 into the measurement light Ls1 and the reference light Ls2. The light splitting means 63 is optically connected to the two optical fibers FB62 and FB63, respectively. The measurement light Ls1 is guided through the optical fiber FB62, and the reference light Ls2 is guided through the optical fiber FB63. The light splitting means 63 in this example also functions as the multiplexing means 64.

  An optical probe 230 is optically connected to the optical fiber FB62, and the measurement light Ls1 is guided from the optical fiber FB62 to the optical probe 230.

  On the other hand, optical path length adjusting means 220 is disposed on the side of the optical fiber FB63 where the reference light Ls2 is emitted.

  Further, the multiplexing means 64 is composed of a 2 × 2 optical fiber coupler as described above, and the reference light Ls2 that has been subjected to frequency shift and change of the optical path length by the optical path length adjusting means 220 and the reflected light Ls3 from the measurement object S. Are combined and emitted to the interference light detection means 640 side via the optical fiber FB64.

  The interference light detecting means 640 detects the interference light Ls4 between the reflected light Ls3 and the reference light Ls2 multiplexed by the multiplexing means 64 by temporally spectroscopically detecting the light intensity of the interference light Ls4. InGaAs-based photodetectors 642a and 642b that detect at a predetermined sampling frequency, and an arithmetic unit 641 that performs balance detection by adjusting the input balance between the detection value of the photodetector 642a and the detection value of the photodetector 642b. ing. The interference light Ls4 is divided into two by the light splitting means 63 and detected by the photodetectors 642a and 642b. Further, between the photodetector 642b and the FB 64, the interference light Ls4 and the auxiliary interference light Lb4 are separated, that is, the interference light Ls4 is transmitted and the auxiliary interference light Lb4 is reflected, and the dichroic mirror. A photodetector 644 for detecting the light intensity of the auxiliary interference light Lb4 reflected by 643 is provided.

  The calculation unit 641 is connected to the tomographic information acquisition unit 650, and the tomographic information acquisition unit 650 is connected to the image generation unit 251 and the real-time optical path length adjustment unit 253. The image generation unit 251 is connected to an image display unit 252 including a CRT, a liquid crystal image display unit, and the like. The photodetector 645 is connected to the real-time optical path length adjustment unit 253, and the real-time optical path length adjustment unit 253 is connected to the optical path length adjustment unit 220.

  The tomographic information acquisition unit 650 Fourier transforms the interferogram (interference waveform) in the optical frequency domain that is the output of the calculation unit 641, calculates the reflection intensity at each depth position of the predetermined measurement target, and uses this Generate fault information. Further, the tomographic information acquisition unit 650, the image generation unit 251 and the real-time optical path length adjustment unit 253 are formed as a computer system such as a personal computer, for example.

  The details of detection of interference light Ls4 and image generation in the interference light detection means 640, the tomographic information acquisition unit 650, and the image generation unit 251 are the same as those of the conventional SS-OCT apparatus. Omitted.

  Hereinafter, the operation of the optical tomographic imaging apparatus 600 having the above configuration will be described. First, an operation when acquiring a tomographic image will be described. First, by moving the base 23 in the direction of arrow A, the optical path length is adjusted so that the measuring object S is positioned within the measurable region. Thereafter, the light Ls is emitted from the light source unit 610, and the light Ls is split by the light splitting unit 63 into the measurement light Ls1 and the reference light Ls2. The measurement light Ls1 is emitted from the optical probe 230 toward the body cavity and irradiated to the measurement object S. At this time, the measurement light Ls1 emitted from the optical probe 230 operating as described above scans the measurement object S one-dimensionally. Then, the reflected light Ls3 from the measuring object S is combined with the reference light Ls2 reflected by the reflecting mirror 523, and the interference light Ls4 between the reflected light Ls3 and the reference light Ls2 is detected by the interference light detection means 640. In the tomographic information acquisition unit 650, the interferogram (interference waveform) of the interference light Ls4 detected by the interference light detection means 640 is subjected to Fourier transform after appropriate waveform compensation and noise removal, and each measurement object S is subjected to Fourier transform. Tomographic information that is reflected light intensity distribution information in the depth direction is acquired.

  Then, if the measurement light Ls1 is scanned on the measurement target S by rotating the optical fiber 13 by the motor 14 of the optical probe 230, the tomographic information of the measurement target S is obtained at each portion along the scanning direction. Therefore, it is possible to generate a tomographic image for a tomographic plane including this scanning direction. The tomographic image acquired in this way is displayed on the image display unit 252.

  Next, the operation of the optical tomographic imaging apparatus 600 will be described in order from the start of the operation. The user inserts the optical probe 230 into the body cavity of the subject before acquiring a tomographic image. First, by manually moving the base 23 of the optical path length changing means 220 in the direction of arrow A, the optical path is roughly set so that the reference point for measurement, for example, the window incident point 16a is located within the measurable region. Adjust the length. After that, immediately before obtaining the tomographic information at each point, the detected value of the light intensity of the auxiliary interference light Lb4 is monitored and the auxiliary reference light Lb2 is monitored as in the optical tomographic imaging apparatus 200 according to the first embodiment. By changing the optical path length and comparing the magnitude of the detected value, the auxiliary reference light so that the optical path length of the auxiliary measurement light + auxiliary reflected light matches the optical path length of the auxiliary reference light at the window incident point 16a. By adjusting the optical path length, the optical path length of the measurement light + reflected light is matched with the optical path length of the reference light. For this reason, even if the optical path length of the measurement light, reflected light or reference light changes due to temperature fluctuations or bending of the optical fiber, the measurement light + reflected light automatically changes at the window incident point 16a. The optical path length matches the optical path length of the reference light, and an optical tomographic image of measurement symmetry S can be acquired satisfactorily.

  Next, a fifth embodiment of the present invention will be described. FIG. 7 is a schematic configuration diagram of an optical tomographic imaging apparatus 700 according to the fifth embodiment of the present invention. In FIG. 5, the same elements as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted unless particularly necessary.

  The optical tomographic imaging apparatus 600 according to the fifth embodiment acquires a tomographic image to be measured by the above-described SS-OCT measurement as compared with the optical tomographic image 300 according to the second embodiment described above. Certain points are different, and other points are basically configured in the same manner as the optical tomographic imaging apparatus 300 according to the second embodiment.

  Also in the optical tomographic imaging apparatus 700, at the window incident point 16a, the optical path length of the auxiliary measurement light Lb1 + auxiliary reflected light 3 and the optical path length of the auxiliary reference light Lb2 that is 2 × shorter than the reference light L2 by a predetermined distance. By adjusting the optical path length of the auxiliary reference light Lb2 so as to match, the optical path length of the measurement light L1 + the reflected light L3 and the optical path length of the reference light−2 × predetermined distance can be matched. Even if there is a change in the optical path length of the measurement light, reflected light or reference light due to temperature fluctuation or bending of the optical fiber, the measurement light + reflection is automatically reflected outside the window incident point 16a by a predetermined distance. The optical path length of the light coincides with the optical path length of the reference light, and an optical tomographic image of measurement symmetry S can be obtained satisfactorily. Further, since the distance between the reflection mirror 22 and the dichroic mirror 321 can be set to a desired distance in the optical path length changing unit 320, an optical tomographic image of a desired depth of the measurement target S can be acquired.

  In each embodiment, when the optical path length is adjusted in real time, if the optical path length is expected to fluctuate significantly, the range of change of the optical path length of the auxiliary reference light Lb2 is expanded, and FIG. The measurement result of the detected value as shown may be acquired, the reference point with the largest detected value may be detected, and the base 23 may be placed at the position where the reference point is obtained.

 In each embodiment of the present invention, each light such as measurement light, reference light, and interference light propagates through the optical fiber, but the present invention is not limited to this. May be propagated.

  Further, when the optical path length of the auxiliary reference light is changed, the optical path length is changed using the optical path length changing means 220 or 230, but the present invention is not limited to this, and the optical path lengths of the auxiliary reference light and the reference light are changed. Any change means may be used as long as it can be changed equally. For example, an optical path length changing element such as a piezo element may be provided in the optical paths of the auxiliary reference light and the reference light, and the optical path length may be changed by the optical path length changing element. Alternatively, as shown in FIG. 8, instead of the optical path length changing means 220 or 320, an optical path length changing means 420 that can divide the optical paths of the reference light and auxiliary reference light and set the optical path lengths individually can be used. Good. In the optical path length changing means 420, the reference light L2 and auxiliary reference light Lb2 propagated through FB3 are introduced into FB42 and FB43 by a WDM (Wavelength Division Multiplexing) coupler 421. The reference light emitted from the FB 42 is reflected by the reflection mirror 423 via the optical lenses 422a and 422b, and enters the FB 42 again. The auxiliary reference light emitted from the FB 43 is reflected by the reflection mirror 425 via the optical lenses 424a and 424b, and is incident on the FB 43 again. The reference lights L2 and Lb2 reflected by the reflecting mirrors are multiplexed by the WDM coupler 421 and propagated through FB3. The mirror driving means 426 moves the optical lens 422b and the reflecting mirror 423 in conjunction with the optical lens 424b and the reflecting mirror 425 in the optical axis direction under the control from the real-time optical path length adjusting means, thereby moving the reference light. The optical path length of L2 can be adjusted.

  In each embodiment, the optical path length is adjusted by changing the optical path length of the reference light. However, the optical path length may be adjusted by changing the optical path length of the measurement light or the reflected light.

  Further, although the optical path length is adjusted using low-coherence light as auxiliary light, laser light whose wavelength is periodically swept can be used instead of low-coherence light. This is the same as the case of changing to use the SS-OCT apparatus instead of the SD-OCT apparatus. The auxiliary interference light Lb4 is sampled and detected, the tomographic information is acquired, and the optical path is based on the tomographic information. The length may be adjusted, or the integrated value obtained by integrating the auxiliary interference light Lb4 with respect to time, that is, the light intensity for one sweep period may be detected, and the optical path length may be adjusted based on the light intensity.

  Furthermore, in each embodiment, the Michelson interferometer is used. However, the present invention is not limited to this, and other types of interferometers such as a Mach-Zehnder interferometer may be used.

1 is a schematic configuration diagram of an optical tomographic imaging apparatus according to a first embodiment of the present invention. The figure which shows the relationship between the light intensity of interference light and the depth of the measuring object Schematic configuration diagram of an optical tomographic imaging apparatus according to a second embodiment of the present invention Schematic configuration diagram of an optical tomographic imaging apparatus according to a third embodiment of the present invention Schematic configuration diagram of an optical tomographic imaging apparatus according to a fourth embodiment of the present invention Explanatory drawing of frequency sweep state in frequency swept laser light Schematic configuration diagram of an optical tomographic imaging apparatus according to a fifth embodiment of the present invention Schematic configuration diagram of a modification of the optical path length changing means

Explanation of symbols

200,300,400,600,700,800 Optical tomographic imaging device 3,63 Optical splitting means 4,64 Multiplexing means
210,610 Light source unit
220,320,420 Optical path length change means
230 Optical probe
240,440,640 Interference light detection means
253,353 Real-time optical path length adjustment unit La Low coherence light Ls Laser light Lb Auxiliary light L1, Ls1 Measurement light L2, Ls2 Reference light L3, Ls3 Reflected light L4, Ls4 Interference light Lb1 Measurement light Lb2 Reference light Lb3 Reflected light Lb4 Interference light S Measurement Target

Claims (7)

A light source unit that emits light;
Light splitting means for splitting the light emitted from the light source unit into measurement light and reference light;
Multiplexing means for multiplexing the reflected light from the measurement object and the reference light when the measurement light divided by the light dividing means is irradiated on the measurement object;
First interference light detection means for detecting first interference light that is interference light between the reflected light and the reference light combined by the multiplexing means;
In an optical tomographic imaging apparatus, comprising: tomographic information acquisition means for acquiring tomographic information of the measurement object by performing frequency analysis on the first interference light detected by the interference light detection means,
An auxiliary light source unit for emitting auxiliary light;
An optical path in which an optical path length difference between the auxiliary measurement light that the light splitting means splits the auxiliary light emitted from the auxiliary light source unit into the same optical path as the measurement light and the optical path of the reference light is defined And is divided into auxiliary reference light guided to
The multiplexing means combines auxiliary reflected light that is reflected light of the auxiliary measurement light divided by the light dividing means and auxiliary reference light,
Second interference light detection means for detecting second interference light that is interference light between the auxiliary reflected light and the auxiliary reference light combined by the multiplexing means;
An optical tomographic imaging apparatus comprising: an optical path length adjustment unit that adjusts an optical path length of the measurement light, the reflected light, or the reference light based on a detection result of the second interference light detection unit. The optical tomographic imaging apparatus according to claim 1, wherein the wavelength band of the auxiliary light does not overlap the wavelength band of the light. The optical tomographic imaging apparatus according to claim 2, further comprising: an optical path separation unit that separates an optical path of the first interference light and an optical path of the second interference light. 2. A first reflecting means provided in an optical path of the measurement light and the auxiliary measurement light, which substantially transmits the measurement light and reflects at least a part of the auxiliary measurement light. 4. The optical tomographic imaging apparatus according to claim 1. The auxiliary reference light is split into the same optical path as the reference light by the light splitting means, and substantially transmits the reference light provided in the optical path of the reference light and the auxiliary reference light, at least 5. The apparatus according to claim 1, further comprising: a second reflecting unit that reflects part of the auxiliary reference light; and a third reflecting unit that reflects the reference light transmitted through the second reflecting unit. The optical tomography imaging apparatus of any one of Claims. 6. The optical tomographic imaging apparatus according to claim 5, wherein the second reflecting means is disposed so as to be movable in the optical path direction. The second interference light detection means outputs an integrated signal obtained by integrating the second interference light spatially or temporally as a detection result;
An optical path length changing means for changing the optical path length;
The optical path length adjusting means compares the integrated signals detected by the second interference light detecting means before and after the change of the optical path length, and based on the comparison result, the measurement light, the reflected light, or the reference light 7. The optical tomographic imaging apparatus according to claim 1, wherein the optical path length of the optical tomographic image is adjusted.

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