JP4677636B2 - Optical coherence tomography apparatus and variable wavelength light generator used therefor - Google Patents

Description

  The present invention relates to an optical coherence tomography (OCT) apparatus and a variable wavelength light generation apparatus used therefor. That is, the present invention relates to an apparatus for measuring tomographic images of various structures such as a living body and a painted surface using a light interference phenomenon and a light source thereof.

(1) Conventional OCT and new OCT by the present inventors
An optical coherence tomography (OCT method) is an optical tomographic method effective for photographing a tomographic image of the retina or the like (Non-patent Document 1). The OCT method has attracted attention for its non-invasiveness to living bodies and high spatial resolution (about 10 μm), and has also been tried to be applied to organs other than eyes (Non-patent Document 1). In OCT that has been put into practical use, in consideration of ease of operation, reliability, and small size and lightness, a semiconductor light emitting element, specifically a near-infrared super luminescent diode (SLD), is used as a light source. Yes. However, since the spatial resolution of OCT is inversely proportional to the spectral width of the light source, it is limited by the spectral width of the SLD and is only about 10 μm. Further, the conventional OCT has a disadvantage that it is not suitable for high-speed measurement because of the mechanical drive portion.
In order to eliminate these disadvantages, the present inventors have developed a new OCT that does not have a driving part and facilitates high-speed measurement (Patent Document 1), and has also made a new invention to further improve the resolution ( Patent Document 2).

(2) Details of the new OCT by the present inventors The new OCT invented by the present inventors constructs a tomographic image from interference signals obtained by using a variable wavelength light source and changing the wavelength of the output light stepwise. To do. The present inventors call this technique the OFDR-OCT method (Optical-frequency-domain-reflectometory-OCT). In the conventional OCT, a tomographic image is constructed by mechanically scanning a reference mirror arranged in the reference optical path. However, since such mechanical scanning is unnecessary in the OFDR-OCT method, extremely high-speed measurement is possible. .

Details of the OFDR-OCT method will be described below.
(A) Apparatus Configuration FIG. 12 is a tomographic imaging apparatus for the anterior segment using the OFDR-OCT method developed by the present inventors.
First, a light exit port of a variable wavelength light generator 111 that is a variable wavelength light generator that can emit light while changing the wavelength, such as a super-periodic structure diffraction grating distributed reflection semiconductor laser light generator (Non-patent Document 1). Is optically connected to the light receiving port of the first coupler 112 including a directional coupler or the like that divides the light into two (for example, 90:10).
The light transmission port on one side (division ratio 90% side) of the first coupler 112 composed of a directional coupler or the like is a main dividing means composed of a directional coupler or the like that divides light into two (for example, 70:30). Is optically connected to the light receiving port of the second coupler 113.

  The light transmission port on one side (the division ratio 70% side) of the second coupler 113 is optically connected to the light receiving port of the traveling direction control means including the optical circulator 115. The light transmission port on the other side (division ratio 30% side) of the second coupler 113 is a third coupler 116 which is a multiplexing means including a directional coupler that divides light into two (for example, 50:50). It is optically connected to the light receiving port. The optical outlet of the optical circulator 115 is optically connected to the optical inlet of the third coupler 116. Further, the light receiving / light sending / out port of the optical circulator 115 is connected to a measuring light irradiation means as shown in FIG. This measurement light irradiating means also functions as a means for capturing signal light in which the measurement light is reflected or backscattered by the eye 200 that is the measurement target. Therefore, it is hereinafter referred to as measurement light irradiation / signal light capturing means.

As shown in FIG. 13, the measurement light irradiation / signal light capturing means 140 has a collimator lens 142 that shapes the measurement light that has passed through the optical fiber into a parallel beam, and a focusing lens 144 that condenses the parallel beam on the anterior segment. And a galvanometer mirror 143 that scans the traveling direction of the measurement light.
The measurement light irradiation / signal light capturing means 140 is attached to a space that is free from the slit light (slit light) irradiation system from the slit lamp microscope 150. By using the alignment function of the slit lamp microscope 150, the measurement light can be guided near a desired position of the subject's eye.
As shown in FIG. 12, the light transmission ports on one side and the other side of the third coupler 116 are optically connected to the light reception port of the first differential amplifier 117 having a light detection function. The Log output unit of the first differential amplifier 117 is electrically connected to the input unit of the second differential amplifier 118 that performs correction calculation of fluctuations in the input signal intensity.

On the other hand, the light transmission port on the other side (the division ratio 10% side) of the first coupler 112 is optically connected to the light reception port of the photodetector 119. The output part of the photodetector 119 is electrically connected to the input part of the Log amplifier 120. The Log output unit of the Log amplifier 120 is electrically connected to the input unit of the second differential amplifier 118.
The output unit of the second differential amplifier 118 is electrically connected to the input unit of the arithmetic control device 121 that synthesizes the coherence interference waveform, that is, the reflection or backscattering intensity distribution, via an analog / digital converter (not shown). is doing. The output unit of the calculation control device 121 is electrically connected to the input unit of the display device 122 such as a monitor or a printer that displays the calculation result. The arithmetic and control unit 121 can control the variable wavelength light generator 111 and the galvanometer mirror 143 based on the input information.

(B) Measurement principle of OFDR-OCT method The signal light generated when the measurement light (laser light divided into 70% by the second coupler 13) is reflected or backscattered by the measurement object, for example, the anterior eye part, The coupler 116 combines and interferes with the reference light (variable wavelength light divided into 30% by the second coupler 113).
The combined light is the sum of the DC component and the interference component, but the first differential amplifier 117 extracts only this interference component. The following equation (1) indicates that the interference component I _d (k _i ) detected by the differential amplifier 117 (differential) when the measurement object has only one reflecting surface 201 as shown in FIG. The difference between two inputs I ₊ (k _i ) _J I ₋ (k _i ) of the amplifier 117 is shown.

2L is the optical path length traveled by the first split light (division ratio 70%) before being split by the second coupler 113 and multiplexed by the third coupler 116 (the travel distance of light multiplied by the refractive index) The same applies hereinafter) and the second split light (split ratio 30%), that is, the difference between the optical path length traveled by the reference light, and k _i is the wave number of the light emitted from the variable wavelength light generator 111 in the i-th position. (= 2π / λ, λ is the wavelength), the intensity of the intensity and the reference light I _s and I _r is reflected or backscattered by the respective measured light (signal light). The first differential amplifier 117 generates an output proportional to the above I _d (k _i ) (more precisely, its logarithm), and the second differential amplifier 118 generates fluctuations in the output of the variable wavelength light generator 111. to correct.

  FIG. 14 shows a case where the reflecting surface exists at a position away from the position where 2L = 0 by the distance D. Since the distance traveled until the light reflected by the reflecting surface 201 returns to the position of 2L = 0 is 2D, 2L = 2D at the position of the reflecting surface. Therefore, the value of L corresponding to the position of the reflecting surface is D.

を算出する。ここで、cos(ｋ_i×ｚ）及びsin(ｋ_i×ｚ）はフーリエ核であり、ｚは位置座標である。Ｎは可変波長光源１１の出射する波数の総数であり、波数間隔をΔｋ、波数走査の起点をｋ₀＋Δｋとすると、ｋ_iは以下の式で表される。尚、ｉ＝１，２，…，Ｎである。

The tomographic image is synthesized by Fourier transforming I _d (k _i ) by the arithmetic and control unit 121. Hereinafter, a process of constructing a tomographic image will be described.
First, Fourier cosine transformation and Fourier sine transformation are performed on I _d (k _i ). That is,

Is calculated. Here, cos (k _i × z) and sin (k _i × z) is the Fourier nucleus, z is the position coordinate. N is the total number of wave numbers emitted from the variable wavelength light source 11. If the wave number interval is Δk and the starting point of wave number scanning is k ₀ + Δk, k _i is expressed by the following equation. Note that i = 1, 2,..., N.

このＹ_t ²（ｚ）又はその平方根を取ったＹ_t（ｚ）が、測定対象の深さ方向に対する反射面（又は散乱面）の反射強度（又は後方散乱強度）の分布を示す。反射面が一つである本例の場合は、以下の式で表される反射分布強度が得られる。

Next, the following Y _t (z) is obtained from the calculated Y _c (z) and Y _s (z).

Y _t ² (z) or Y _t (z) taking the square root thereof indicates the distribution of the reflection intensity (or back scattering intensity) of the reflection surface (or scattering surface) with respect to the depth direction of the measurement object. In the case of this example having one reflecting surface, the reflection distribution intensity represented by the following equation is obtained.

式（６）の第１項で

とおくと、第１項は

となる。この式は、ｘ＝０即ちｚ＝２Ｌで大きな値Ｎ²になりｚ＝２Ｌから離れると急激のゼロに近づく。同様に、第２項はｚ＝−２Ｌで大きな値Ｎ²になりｚ＝−２Ｌから離れると急激のゼロに近づく。即ち、この項は、折り返し像を生成する。 Here, B (z) is expressed by the following equation and forms part of the noise floor.

In the first term of equation (6)

The first term is

It becomes. This equation becomes a large value N ² when x = 0, that is, z = 2L, and approaches abrupt zero when moving away from z = 2L. Similarly, the second term becomes a large value N ² at z = −2L, and approaches a sudden zero when moving away from z = −2L. That is, this term generates a folded image.

Therefore, by plotting x = z / 2 on the horizontal axis and Y _t ² (2x) on the vertical axis y, y = N ^z · I _r · I _s is obtained when x = ± L, and is substantially 0 at other positions. It becomes.
Normally, the optical path length is adjusted so that there is no measurement target when x ≦ 0, and Y _t ² (2x) is plotted only for x ≧ 0. Therefore, even if Y _t ² (2x) is plotted against x, a folded image does not appear, and the distribution of reflection (or backscattering) intensity in the depth direction can be obtained by the plot.

Although the case where the wave number changes stepwise with respect to the scanning time has been described above, a light source that continuously changes the wave number with respect to time may be used. Although it is ideal if the sampling time for measuring the interference signal intensity is sufficiently shortened, an approximate result can be obtained if the center wave number k _i of each sampling period is not.

(3) Resolution improvement of OFDR-OCT method The spatial resolution of OCT is inversely proportional to the spectral width of the light source. This is the same in OFDR-OCT (the resolution of OFDR-OCT is determined not by the spectrum width of individual variable wavelength light, but by the width of the spectrum formed by collecting the spectrum of individual variable wavelength lights. That is, the width of the variable wavelength region.) If the spectrum width is to be widened by the conventional OCT using the SLD as a light source, the outputs of a plurality of SLDs having different center wavelengths are combined. However, for example, when the outputs of two SLDs having different center wavelengths are combined, the spectrum shape becomes bimodal, which is significantly different from the original Gaussian shape suitable for OCT. For this reason, the resolution does not decrease in inverse proportion to the spectrum width, and a ghost is generated in the obtained tomographic image (Patent Document 2).

On the other hand, in OFDR-OCT, the shape of the spectrum obtained by scanning the wavelength is originally rectangular. Therefore, even if a plurality of variable wavelength light sources are combined, the spectrum shape remains rectangular, so no problem occurs.
That is, if a plurality of variable wavelength light sources are sequentially wavelength-scanned and their outputs are combined, the spatial resolution of OFDR-OCT can be easily improved.

  FIG. 15 is a conceptual diagram of a high-resolution light source in which a plurality of variable wavelength light sources are combined to improve the spatial resolution of OFDR-OCT. Reference numeral 241 denotes a plurality of variable wavelength light sources for wavelength scanning in different variable wavelength ranges, and reference numeral 244 denotes a control circuit for sequentially scanning each variable wavelength light source. Reference numeral 242 denotes an optical coupler for multiplexing the outputs of the respective variable wavelength light sources.

  FIG. 16 shows an output spectrum of a high-resolution light source composed of two variable wavelength light sources. Regions 1 and 2 in the output spectrum are derived from the spectrum of each variable wavelength light source, and the output spectrum of the light source for high resolution is obtained by connecting the spectrum of each variable wavelength light source. As is clear from this figure, the output spectrum of the high resolution light source is rectangular, and there is no difference in shape from the single variable wavelength light source used in normal OFDR-OCT. Therefore, when a plurality of light sources are combined as in the conventional OCT, the spectrum shape does not change, and there is no adverse effect such as generation of a ghost due to this.

JP 2005-156540 A Japanese Patent Application No. 2004-332964 Japanese Patent Application No. 2005-14650 Yoshikuni Yuzo, Applied Physics, Vol. 71, No. 11 (2002), pp. 1362-1366 Takuji Amano, Hideaki Hiro-Oka, DongHak Choi, Hiroyuki Furukawa, Fumiyoshi Kano, Mituo Takeda, Motoi Nakanishi, Kimiya Shimizu, and Kohji Ohbayashi, APPLIED OPTICS, Vol.44, pp.808-816 (2005). S.H.Yun, G.J.Tearney, J.F.de Boer, and B.E.Bouma, OPTICS EXPRESS, No.23, pp.5614-5624 (2004).

  However, in the high resolution light source of the OFDR-OCT apparatus, the time required to scan the entire enlarged variable wavelength region increases in proportion to the number of combined variable wavelength light sources. That is, the high resolution light source has a problem that the measurement speed decreases when the variable wavelength region is expanded in order to improve the resolution.

An optical coherence tomography apparatus according to a first aspect of the present invention for solving the above problems is provided.
A plurality of variable wavelength light generating means having different wave number scanning ranges;
Control means for simultaneously scanning the wavelength of the plurality of variable wavelength light generating means;
Respective means for dividing each output light of the variable wavelength light generating means into measurement light and reference light;
Means for combining the respective measurement lights into one measurement light;
Means for irradiating the measurement object with the one measurement light, and capturing the signal light reflected or backscattered by the measurement object by the one measurement light;
Means for splitting the signal light;
Respective means for individually combining the split signal light and the respective reference light;
Respective means for measuring the intensity of the individual output lights combined by the respective means for individually multiplexing for each wave number of the plurality of variable wavelength light generating means,
A position where the measurement light is reflected or back-scattered by the measurement object and a reflection or back-scattering intensity from the set of intensity of the individual output lights measured for each wave number by the means for measuring the measurement object. have a means for identifying relative depth direction of,
The means for specifying is a Fourier transform of the set of individual output light intensities with respect to the wave number;
Each measurement light and each signal light traveling from each of the means for dividing to each of the means for combining individually travels, which is obtained in advance as a standard sample of a measuring object consisting of one reflecting surface. Find the difference between the sum of the optical path lengths and the optical path lengths of the respective reference lights combined individually from the respective means for dividing,
And a means for correcting an influence of each of the differences on the construction of a tomographic image based on a difference between the difference selected from one of the differences and the other difference .
The optical coherence tomography device of the second invention is
A plurality of variable wavelength light generating means having different wave number scanning ranges;
Control means for simultaneously scanning the wavelength of the plurality of variable wavelength light generating means;
Respective means for dividing each output light of the variable wavelength light generating means into measurement light and reference light;
Means for combining the respective measurement lights into one measurement light;
Means for irradiating the measurement object with the one measurement light, and capturing the signal light reflected or backscattered by the measurement object by the one measurement light;
Means for splitting the signal light;
Respective means for individually combining the split signal light and the respective reference light;
Respective means for measuring the intensity of the individual output lights combined by the respective means for individually multiplexing for each wave number of the plurality of variable wavelength light generating means,
A position where the measurement light is reflected or back-scattered by the measurement object and a reflection or back-scattering intensity from the set of intensity of the individual output lights measured for each wave number by the means for measuring the measurement object. Means for specifying the depth direction of
The means for specifying is a Fourier transform of the set of individual output light intensities with respect to the wave number;
The position where the one measurement light is reflected or backscattered and the reflected or backscattered intensity obtained by Fourier-transforming the wavenumber for each wavenumber scanning range with respect to the set of intensities of the individual output lights. A cross-correlation function is synthesized from each function specified in the depth direction of the measurement target,
From the cross-correlation function, the sum of the optical path lengths of the measurement light and the signal light traveling from the respective means for dividing to the respective means for multiplexing individually, and the respective means for dividing From the respective optical path lengths of the reference light to the respective means for individually combining, the respective differences are obtained,
And a means for correcting an influence of each of the differences on tomographic image construction based on a difference between each of the differences and the selected one of the differences .

The optical coherence tomography device of the third invention is the optical coherence tomography device of the first or second invention,
The means for making the one measurement light and the means for dividing the signal light are the same means.

An optical coherence tomography apparatus according to a fourth aspect of the present invention is the optical coherence tomography apparatus according to any one of the first to third aspects of the invention ,
Based on the ratio of the amplitudes of the individual output lights obtained in advance as a standard sample to be measured consisting of one reflecting surface,
It has means for correcting the intensity of the individual output light.

An optical coherence tomography apparatus according to a fifth aspect of the present invention is the optical coherence tomography apparatus according to any one of the first to fourth aspects of the invention ,
Means for correcting the influence on the tomographic image construction,
For each wave number scanning range of the plurality of variable wavelength light generating means, the position coordinates of the Fourier nucleus of the Fourier transform are obtained by adding the differences to the position coordinates.

An optical coherence tomography apparatus according to a sixth aspect of the present invention is the optical coherence tomography apparatus according to any one of the first to fifth aspects of the invention ,
Determining the phase change caused to the individual output light by the optical path traveled by the respective measurement light, the respective signal light, the one measurement light, and the respective reference light;
The Fourier transform for each wave number scanning range of the plurality of variable wavelength light generating means is a product of the wave number and position coordinates of the Fourier nucleus, and the phase change is added to the product. .

According to a seventh aspect of the present invention, there is provided a variable wavelength light generator for an optical coherence tomography device according to any one of the first to sixth inventions, wherein the plurality of variable wavelength light generation means in the optical coherence tomography device, It is characterized by comprising control means for wavelength scanning.

A variable wavelength light generator for an optical coherence tomography device according to an eighth aspect of the present invention is the variable wavelength light generator for an optical coherence tomography device according to the seventh aspect of the invention,
The variable wave number range is 0.2 μm- ¹ or more with respect to the wave number.

A variable wavelength light generator for an optical coherence tomography device according to a ninth aspect of the present invention is the variable wavelength light generator for an optical coherence tomography device according to the seventh or eighth aspect of the invention,
A wave number scanning period of the variable wavelength light source is 5 ms or less.

A variable wavelength light generator for an optical coherence tomography device according to a tenth aspect of the present invention is the variable wavelength light generator for an optical coherence tomography device according to any one of the seventh to ninth inventions ,
The variable wavelength light source is capable of discretely switching wave numbers.

A variable wavelength light generator for an optical coherence tomography apparatus according to an eleventh aspect of the present invention is the variable wavelength light generator for an optical coherence tomography apparatus according to any one of the seventh to tenth aspects of the invention .
The variable wavelength light source is a variable wavelength laser.

  According to the present invention, the measurement time does not increase even if the number of variable wavelength light sources is increased in order to increase the spatial resolution. That is, a high-resolution and high-speed OFDR-OCT apparatus can be realized.

Example 1
The present invention relates to an OFDR-OCT light source and an OFDR-OCT apparatus that enable high-resolution and high-speed measurement. The light source and apparatus according to the present invention are referred to as a high-speed / high-resolution OFDR-OCT light source and a high-speed / high-resolution OFDR-OCT apparatus.
First, an embodiment in which two variable wavelength light sources are used will be described.

(1) Apparatus Configuration FIG. 1 is a schematic diagram of a high-speed / high-resolution OFDR-OCT apparatus according to Embodiment 1 of the present invention. FIG. 2 shows a change in wavelength of light emitted from the variable wavelength light sources 1 and 2 shown in FIG. 1 with respect to time. The vertical axis represents the wavelength (or wave number) of the light emitted from each variable wavelength light source, and the horizontal axis represents the elapsed time since the first wavelength was emitted.

  As shown in FIG. 1, the high-speed / high-resolution OFDR-OCT apparatus according to the first embodiment includes a plurality of variable wavelength light generators 25 that can simultaneously perform wavelength scanning and have different wave number scanning ranges, and a variable wavelength light generator. Couplers 5 and 7 that divide each of the 25 output lights into measurement light and reference light, a coupler 13 that combines the respective measurement lights into one measurement light, and the one measurement light as a measurement object. Irradiating and measuring light irradiation system / signal light receiving system 23 for capturing the signal light reflected or backscattered by the measurement object, the coupler 13 for splitting the signal light, and the splitting Couplers 6 and 8 for individually combining the signal light thus generated and the respective reference lights, and the intensity of each output light combined by the couplers 6 and 8 is measured for each wave number of the variable wavelength light generator 25. Differential amplifiers 11 and 12 that The position at which the measurement light is reflected or backscattered by the measurement object and the reflected or backscattering intensity from the set of intensity of the individual output lights measured for each wave number by the amplifiers 11 and 12 is the depth of the measurement object. It has the structure which has the calculation control apparatus 22 specified with respect to a direction.

  More specifically, the variable wavelength light sources 1 and 2 constituting the variable wavelength light generator 25 are for performing wavelength scanning (wave number scanning) simultaneously in different wavelength regions. Each of the variable wavelength light sources 1 and 2 performs wavelength scanning (wave number scanning) stepwise as shown in FIG. The wavelength scanning regions of the variable wavelength light sources 1 and 2 are not necessarily in contact with each other, but in this embodiment, the wavelength scanning regions 3 and 4 are in contact with each other as shown in FIG. Further, the wavelength interval is scanned so as to be equal intervals when converted into wave numbers.

In the example of FIG. 2, the wave number interval is 2.6 × 10 ⁻⁴ μm ⁻¹ , and the holding time per wave number is 1 μs. The wavelength scanning ranges of the variable wavelength light sources 1 and 2 are 1.530 to 1.570 μm and 1.570 to 1.610 μm, respectively. The output intensity of the variable wavelength light sources 1 and 2 is a constant value of 10 mW regardless of the wave number.
The variable wavelength light sources 1 and 2 use, for example, a super-periodic structure diffraction grating distributed reflection semiconductor laser (Non-patent Document 1). In addition, a sample, a grating, a distributed reflection type semiconductor laser (SG-DBR laser, US4896325), a modulated grating Y laser (MG-Y laser), and a grating coupler reflector laser (Grating Coupler Sampled Reflector Laser) , GCSR laser) can also be used.

  The variable wavelength light source 1 constitutes a first interferometer together with the couplers 5 and 6 including the directional coupler, the circulator 9 and the differential amplifier 11. Each component is optically connected by an optical fiber. The variable wavelength light source 2 constitutes a second interferometer together with the couplers 7 and 8, which are directional couplers, the circulator 10, and the differential amplifier 12. Then, the light reception / light transmission ports 14 and 15 of the circulator 9 constituting the first interferometer and the circulator 10 constituting the second interferometer are connected to a coupler 13 composed of a directional coupler, and The output is connected to a measuring light irradiation system / signal light receiving system 23 including a collimator lens 27, a galvano mirror 15, and an objective lens 16.

  The differential amplifiers 11 and 12 output a voltage proportional to the difference between the two inputs, and the division ratio of the couplers 5 and 7 is 70:30 (= sample optical path 17 and 18 side: reference optical path 19 and 20 side). ). The division ratio of the couplers 6 and 8 is 50:50. When the output light intensity of the variable wavelength light sources 1 and 2 fluctuates, the outputs of the differential amplifiers 11 and 12 are logarithmic outputs, and the coupler 112 used in the conventional OFDR-OCT (FIG. 12). By using a correction circuit including the photodetector 119, the Log amplifier 120, and the differential amplifier 118, it is possible to correct the intensity fluctuation of the output light of the variable wavelength light sources 1 and 2. When the intensity of the output light from the variable wavelength light sources 1 and 2 is stable, this circuit is unnecessary. In the following description, the output of the variable wavelength light sources 1 and 2 is assumed to be constant regardless of the wavelength, and the case where there is no correction circuit will be described.

  The outputs of the differential amplifiers 11 and 12 are input to an A / D converter 21, and the output is electrically connected to an input unit of an arithmetic control device 22 that synthesizes a coherence interference waveform, that is, a reflection or backscattering intensity distribution. Yes. The arithmetic and control unit 22 is composed of, for example, a computer. The output unit of the calculation control device 22 is electrically connected to an input unit of a display device (not shown) such as a monitor or a printer that displays the calculation result. The arithmetic and control unit 22 can control the variable wavelength light generators 1 and 2 and the galvanometer mirror 15 based on the input information.

  Here, the variable wavelength light generator 25 will be described in detail. As shown in FIG. 3, the variable wavelength light generator 25 includes a plurality of (two in the illustrated example) variable wavelength light sources 1 and 2 having different wave number scanning ranges. And a control circuit 26 as control means for simultaneously scanning the wave numbers of the variable wavelength light sources 1 and 2. That is, the control circuit 26 drives the variable wavelength light sources 1 and 2 simultaneously based on a command from the arithmetic and control unit 22. As a result, the variable wavelength light source 1 outputs the variable wavelength light 1 to the coupler 5, and at the same time, the variable wavelength light source 2 outputs the variable wavelength light 2 to the coupler 7. That is, the variable wavelength light generator 25 is configured to include a plurality (two in the illustrated example) of variable wavelength light generators that can simultaneously perform wavelength scanning and have different wave number scanning ranges. That is, the variable wavelength light sources 1 and 2 are connected to the control circuit 26 and driven, so that wavelength scanning can be performed simultaneously.

  In FIG. 3, the control circuit 26 has a function of driving the variable wavelength light sources 1 and 2, but the present invention is not limited to this, and each of the variable wavelength light sources 1 and 2 is driven as shown in FIG. The control circuits 26A and 26B, and a control circuit for simultaneously driving the variable wavelength light sources 1 and 2 by the control circuits 26A and 26B by giving an operation command to the control circuits 26A and 26B based on a command from the arithmetic and control unit 22. It may be divided into 26C. Furthermore, the arithmetic control device 22 may also serve as the function of the control circuit 26C.

(2) Operation Method Next, an operation method of the high speed / high resolution OFDR-OCT apparatus will be described.
The output (variable wavelength light 1) of the variable wavelength light source 1 of the first interferometer is divided by the coupler 5 and sent to the sample optical path 17 and the reference optical path 19. The reference light divided into the reference optical path 19 is input to one input terminal of the coupler 6. The measurement light divided into the sample optical path 17 is input to the circulator 9, transmitted from the light receiving / light transmitting port 14, and input to the coupler 13. The measurement light input to the coupler 13 is combined with the measurement light of the second interferometer, and is irradiated onto the measurement object 24 via the measurement light irradiation system / signal light receiving system 23. The signal reflected or backscattered in the measurement object 24 is captured by the measurement light irradiation system / signal light reception system 23 and sent back to the coupler 13.
The coupler 13 divides the signal light into two parts, and one of them is sent to the light receiving / light sending port 14 of the circulator 9. The signal light input to the circulator 9 is sent to the other input terminal of the coupler 6. The coupler 6 combines the signal light and the reference light and sends them to the differential amplifier 11 having a light detection function.

  Similarly, in the second interferometer, the output of the variable wavelength light source 2 (variable wavelength light 2) is divided into the sample optical path 18 and the reference optical path 20, and the measurement light in the sample optical path 18 is coupled to the first interferometer by the coupler 13. The measurement light is combined with the measurement light and irradiated onto the measurement object 24 via the measurement light irradiation system / signal light receiving system 23. The signal light reflected or backscattered in the measurement object 24 is captured by the measurement light irradiation system / signal light reception system 23 and then divided into two by the coupler 13, one of which is the light reception / light transmission / reception port 15 of the circulator 10. Is sent out.

  The outputs of the differential amplifiers 11 and 12 are converted into digital signals by the A / D converter 21 and then input to the arithmetic control device 22. The arithmetic and control unit 22 synthesizes the reflection or backscattering intensity distribution based on the signal obtained by digitizing the outputs of the differential amplifiers 11 and 12. By repeating this operation while changing the measurement position little by little in the horizontal direction, a tomographic image of the measurement object 24 is constructed.

The outputs of the differential amplifiers 11 and 12 are proportional to the intensity of the respective interference light generated by the light emitted from the wavelength light sources 1 and 2, respectively, as shown in the section “(3) Principle” below. However, in the first and second interferometers, there are differences in the output intensity of the variable wavelength light sources 1 and 2 and the quantum efficiency and amplification factor of the differential amplifiers 11 and 12, and the sample optical paths 17 and 18 and the reference optical path 19, Usually, the optical path lengths of 20 do not match. Furthermore, different phase changes are given to the signal light returning to the first and second interferometers by the coupler 13. Therefore, in these cases, it is not possible to construct a tomographic image even if the outputs of the differential amplifiers 11 and 12 obtained for each wavelength are analyzed by the same method as that of the conventional OFDR-OCT.
Therefore, according to the present invention, in these cases, an accurate tomographic image is obtained by correcting these differences by the method described in “(4) Correction method” below. It should be noted that these corrections are unnecessary if there is no difference, mismatch or phase change as described above.

By the way, the resolution in the free space of the OFDR-OCT apparatus is given by the following equation (Non-patent Document 2).
2.78 / W _k
Here, W _k is the spectrum width of the measurement light obtained by combining the outputs of the respective variable wavelength light sources into one. Based on this equation, the total wavenumber scanning range 0.20 [mu] m ^-1 (e.g., a wavelength range (1530~1610nm) above, 0.43 .mu.m ^-1 (e.g., a wavelength range 1450～1610Nm) above, 10 [mu] m ^-1 (e.g., a wavelength range (1310 to 1610 nm) and above, the resolution is 10 μm or less, 4.7 μm or less, and 2.2 μm or less in the living body (refractive index 1.38), respectively. According to the present invention, it is possible to improve the resolution.

  In addition, the measurement time of the present invention is determined by the time that each variable wavelength light source scans the entire wave number range. If this time is 5 ms or less, even if the reflection intensity distribution (or backscattering intensity) in the depth direction is measured at 100 points in the horizontal direction, the measurement is completed in 500 ms. Therefore, a clear tomographic image can be measured even for a living body that is difficult to rest. Further, if it is 0.5 ms or less and 0.05 ms or less, a three-dimensional tomographic image or a moving image can be taken.

ここでＥ_r1は、可変波長光源１から参照光路１９へ分割された参照光の電界強度を表す。Ｅ_s1は、可変波長光源１から試料光路１７へ分割され試料２４によって反射（又は後方散乱）された信号光の強度を示す。一方Ｅ_s2は、第二の干渉計を構成する可変波長光源２から試料光路１８へ分割され試料２４によって反射（又は後方散乱）されてカプラ１３によって第一の干渉計の試料光路１７に入力した信号光の電界強度を表す。信号光の電界強度が、Ｅ_s1ではなくＥ_s1＋Ｅ_s2である点が従来のＯＦＤＲ−ＯＣＴと異なる。 (3) Principle Consider the output of the first interferometer. In order to simplify the explanation, the phase change given to the signal light by the coupler 13 is ignored here.
The electric field intensity E ₁ of the interference light obtained by combining the reference light and the signal light is expressed by the following expression.

Here, E _r1 represents the electric field strength of the reference light divided from the variable wavelength light source 1 to the reference optical path 19. E _s1 indicates the intensity of the signal light that is split from the variable wavelength light source 1 into the sample optical path 17 and reflected (or backscattered) by the sample 24. On the other hand, E _s2 is divided into the sample optical path 18 from the variable wavelength light source 2 constituting the second interferometer, reflected (or backscattered) by the sample 24, and input to the sample optical path 17 of the first interferometer by the coupler 13. Represents the electric field strength of signal light. Field strength of the signal light, that it is E _s1 + E _s2 rather than E _s1 is different from the conventional OFDR-OCT.

ここで、「＊」は共役複素数を、「Ｒｅ」は実部をとることを表す。また明示はしないが、式（９）の各項に時間平均したものである（以下、同じ）。 The intensity of the interference light of the first interferometer is as follows.

Here, “*” represents a conjugate complex number, and “Re” represents a real part. Although not explicitly shown, each term in Equation (9) is time averaged (hereinafter the same).

となる。 Since light from different light sources do not interfere with each other, the fifth and sixth terms on the right side are zero. Therefore, equation (9) is

It becomes.

Since the coherent time of the variable wavelength light source is about 10 ns, the fifth term and the sixth term on the right side of Equation (9) can take a finite value within this time, but the differential amplifier 11 is usually several hundred ns or more. A value obtained by averaging the interference signal over a period of time is output. Therefore, the values of the fifth and sixth terms can be considered to be almost zero.
The first differential amplifier 11 cancels the first term, the second term, and the third term on the right side, which are direct current components, and extracts only the interference component of the fourth term. Therefore, the output V ₁ (k ₁ ) of the first differential amplifier 11 is as follows.

と表される。 Here, k ₁ and ω ₁ are the wave number and angular frequency of the wavelength tunable light source 1. l _r1 is the optical path length of the reference optical path 19 from the coupler 5 to the coupler 6, and l _s1 is the optical path length of the sample optical path 17 from the coupler 5 to the coupler 6. t indicates time. 2z ₁ (= l _s1 −l _r1 ) is the optical path length difference between the sample optical path 17 and the reference optical path 19. A _r1 and A _s1 are the electric field amplitudes of the reference light and the signal light, respectively. J is a pure imaginary number.
In the above discussion, the quantum efficiency and amplification factor of the differential amplifier 11 are not considered. When the coefficient α ₁ representing these effects is introduced,

It is expressed.

と表される。ｋ₂は可変波長光線２の出力光の波数であり、２ｚ₂＝（ｌ_s2−ｌ_r2）は第２の干渉計の試料光路１８と参照光路２０の光路長差である。また、Ａ_r2，Ａ_s2は、それぞれ参照光及び信号光の電界振幅である。 Similarly for the output V ₂ (k ₂ ) of the differential amplifier 12 of the second interferometer,

It is expressed. k ₂ is the wave number of the output light of the variable wavelength light beam 2, and 2z ₂ = (l _s2 −l _r2 ) is the optical path length difference between the sample optical path 18 and the reference optical path 20 of the second interferometer. A _r2 and A _s2 are the electric field amplitudes of the reference light and the signal light, respectively.

  That is, the differential amplifiers 11 and 12 output interference signals based on the light emitted from the variable wavelength light sources 1 and 2, respectively. Therefore, in this embodiment, even when the wavelength scanning of the variable wavelength light sources 1 and 2 is performed simultaneously, the interference signal (formula (12)) for the wavelength region of the variable wavelength light source 1 and the interference signal (formula ( 13)) can be measured independently. For this reason, the number of variable wavelength light sources is twice that of the prior art (that is, the variable wavelength range is twice), but the measurement time is not different from the case of one conventional variable wavelength light source.

Comparing the equations (12) and (13), the outputs of the differential amplifiers 11 and 12 are equal to the amplitude (α ₁ A _r1 A _s1 , α _{2 Ar 2} A _s2 ) and the optical path length difference ( It can be seen that z ₁ and z ₂ ) do not match. In the present invention, as described in the following section, the difference in amplitude can be corrected by a correction coefficient obtained from a standard sample. The optical path length difference can also be corrected by modifying the Fourier transform when constructing the tomographic image, as described in the next section.

  In the above example, the phase change that the coupler 13 gives to the signal light is ignored. However, in reality, there are more cases where a phase change is caused by the coupler 13. Even in such a case, this phase change can be corrected by an appropriate means.

ここで、κ_r1 ²：κ_s1 ²及びκ_r2 ²：κ_s2 ²は、それぞれカプラ５及びカプラ７の分割比を表す。 (4) Correction Method (a) Amplitude Correction First, a method for correcting amplitude mismatch will be described.
Assuming that the light reflectance of the measurement object 24 is R and the electric field strengths of the radiated light from the variable wavelength light sources 1 and 2 are S ₁ and S ₂ , respectively, A _r1 , A _s1 , A _r2 , and A _s2 are expressed as follows: Can do.

Here, κ _r1 ² : κ _s1 ² and κ _r2 ² : κ _s2 ² represent division ratios of the coupler 5 and the coupler 7, respectively.

今、測定対象としてミラー（反射率Ｒ´）を選択し差動増幅器１１の出力を走査波数に対してプロットすると、反射面は一枚なので振幅Ｂ₁が

振動数が２ｚ₁の余弦関数になる（図５の上図（ａ））。一方、差動増幅器１２の出力は振幅Ｂ₂が、

振動数が２ｚ₂の余弦関数になる（図５の下図（ｂ））。 Therefore, Expression (12) and Expression (13) can be modified as follows.

Now, when a mirror (reflectance R ′) is selected as a measurement target and the output of the differential amplifier 11 is plotted against the scanning wave number, the amplitude B ₁ is ₁ because the reflection surface is one.

The frequency becomes a cosine function of 2z ₁ (upper figure (a) in FIG. 5). On the other hand, the output of the differential amplifier 12 has an amplitude B ₂ ,

The frequency becomes a cosine function of 2z ₂ (the lower diagram (b) of FIG. 5).

この値は第一の干渉計と第二の干渉計の特性の相違に基づくものであり、測定対象の反射率には依存しない。従ってこの値Ｋ（以下、振幅補正係数と呼ぶ）を用いると、差動増幅器１２の出力Ｖ₂（ｋ₂）は以下のように補正をすることができる。

ここでＣ＝α₁・κ_r1・κ_s1・Ｓ₁ ²である。 Therefore, the ratio K (= B ₁ / B ₂ ) of the output B ₁ of the differential amplifier 11 and the amplitude B ₂ of the output of the differential amplifier 12 is as follows.

This value is based on the difference in characteristics between the first interferometer and the second interferometer, and does not depend on the reflectance of the measurement object. Accordingly, when this value K (hereinafter referred to as an amplitude correction coefficient) is used, the output V ₂ (k ₂ ) of the differential amplifier 12 can be corrected as follows.

Here, C = α ₁ · κ _r1 · κ _s1 · S ₁ ² .

以上の様に補正係数Ｋを予め求めておくことにより、第一及び第二の干渉計の特性の相違によって生じる両干渉計の干渉信号強度の相違は補正することができる。 On the other hand, Expression (18) can also be expressed as follows using the coefficient C.

By obtaining the correction coefficient K in advance as described above, it is possible to correct the difference in interference signal intensity between the two interferometers caused by the difference in the characteristics of the first and second interferometers.

(B) Correction of optical path length Next, a method for correcting the difference in optical path length difference (z ₁ , z ₂ ) will be described.
There are two methods for correcting the optical path length difference.

(B-1) Method for Adjusting Optical Path Length The correction method based on the simplest principle is to insert a member that enables adjustment of the optical path length into either one or both of the first and second interferometers. The optical path length difference (2z ₁ , 2z ₂ ) is matched. FIG. 6 shows an example of an apparatus in which the optical path length difference is adjusted using the optical delay devices 31 and 32.
The optical path length difference can be matched by actually measuring the optical path length differences 2z ₁ and 2z ₂ using a mirror as a standard sample. That is, the output of the differential amplifiers 11 and 12 obtained by operating the variable wavelength light sources 1 and 2 using a fixed mirror as a standard sample is subjected to data processing based on the equations (2) to (5), respectively, and z _1. , Z ₂ , and the optical delay units 31 and 32 may be adjusted so that z ₂ and z ₁ coincide.

The adjustment of the optical path length difference needs to consider the influence of environmental temperature. Of the components that make up the interferometer, the length of the optical fiber is much larger than that of other components, so that the influence of expansion and contraction due to temperature changes appears remarkably. Therefore, since z ₁ and z ₂ themselves change when the apparatus temperature changes, accurate correction cannot be made even if z ₁ and z ₂ are measured in advance. In particular, if the temperature change is different between the sample optical path and the reference optical path, the error becomes large. Therefore, in an environment where the apparatus temperature is likely to change, it is preferable to measure z ₁ and z ₂ as appropriate and adjust the optical path length frequently.

(B-2) Method of correcting the Fourier transform (i) Principle Even if the optical path length difference cannot be physically matched as in (b-1) above, the difference in the optical path length difference is corrected by data processing. Can do.
When there is one variable wavelength light source as described in the section of the prior art, the reflectance distribution (or backscattering distribution) Y _t ² (z) in the depth direction is the output V (k _i ) of the differential amplifier. Based on this, it can be obtained as follows.

を算出し、得られた値に用いて以下の式に従ってＹ_t ²（ｚ）を計算する。

尚、ｚは深さ方向の位置座標であり、Ｎは可変波長光源の出射する波数の総数である。また、波数間隔をΔｋ、波数走査の起点をｋ₀＋Δｋとした場合、ｋ_iは

と定義される。但し、ｉ＝１，２，…，Ｎである。 First, from the output V (k _i)

And Y _t ² (z) is calculated according to the following formula using the obtained value.

Here, z is the position coordinate in the depth direction, and N is the total number of waves emitted from the variable wavelength light source. Further, when the wave number interval is Δk and the starting point of wave number scanning is k ₀ + Δk, k _i is

Is defined. However, i = 1, 2,..., N.

但し、δ＝２ｚ₂−２ｚ₁である。この値は試料の位置に拠らず一定の値になるので、ミラーを標準試料にして求めることができる。Ｖ₂´（ｋ_i）はＶ₂（ｋ_i）に振幅補正係数Ｋを乗じたものである。δを求めるためには、固定ミラーを試料として第一及び第二の干渉計を動作させて式（２）〜（５）に基づいてｚ₁，ｚ₂を測定しδ＝２ｚ₂−２ｚ₁を算出すればよい。また、Ｍは第１の可変波長光源１の出射する波数の総数であり、ＮはＭと第２の可変波長光源２の出射する波数の総数の和である。 In the correction method by data processing, the following equations are used instead of equations (23) to (25).

However, it is δ = 2z ₂ -2z _1. Since this value is constant regardless of the position of the sample, it can be obtained using the mirror as a standard sample. V ₂ ′ (k _i ) is obtained by multiplying V ₂ (k _i ) by an amplitude correction coefficient K. In order to obtain δ, the first and second interferometers are operated using a fixed mirror as a sample, z ₁ and z ₂ are measured based on the equations (2) to (5), and δ = 2z ₂ -2z _1. May be calculated. M is the total number of wave numbers emitted from the first variable wavelength light source 1, and N is the sum of M and the total number of wave numbers emitted from the second variable wavelength light source 2.

この節の後半で導出するようにＹ_t´²（ｚ）の関数形は、次式で表される。

この式の導出は、この節の後半で行う。 The reflectance distribution (or backscattering distribution) Y _t ′ ² (z) is calculated based on the following equation using Y _c ′ (z) and Y _s ′ (z).

As derived later in this section, the functional form of Y _t ' ² (z) is expressed by the following equation.

We will derive this equation later in this section.

と仮定した。また、横軸は光路長差の倍（２ｚ₁）なので、実距離に直すのに２で割る必要がある点に留意する必要がある。 FIG. 7 is an example of a graph of Y _t ' ² (z). Here, B (z) is a function that is substantially zero for all z.
In the region of z ≧ 0, only one sharp peak due to the reflected light from the sample appears at the position of z = 2z ₁ . On the other hand, in the region where z ≦ 0, _two folded images appear at z = −2z ₂ and z = −2z ₂ −δ. However, the measurement of the tomographic image is usually performed after adjusting the optical path length so that there is no measurement target when z ≦ 0. In this case, the folded image appears only at z <0 as shown in FIG. Therefore, by plotting Y _t ′ ² (z) against z ≧ 0, a distribution in the depth direction of the reflection (or backscattering) intensity can be obtained. In the above discussion, −2z ₂ −δ ≧ 0, that is,

Assumed. In addition, since the horizontal axis is twice the optical path length difference (2z ₁ ), it is necessary to note that it is necessary to divide by 2 in order to restore the actual distance.

次に式（３１）を、オイラーの公式と関係式δ＝２ｚ₂−２ｚ₁を用いて変形する。

この式では

に関する項が、ｉ＝１からｉ＝Ｎまでの総和を取るよう纏められている。
尚、ｋ_i´＝（ｋ₀＋Δｋ・Ｍ）＋Δｋ×ｉである。 (Ii) Derivation of Y _t ′ ² (z) Finally, details of the derivation process of Expression (30) will be described.
First, Equation (21) and Equation (22) are substituted into Equation (27) and transformed using the trigonometric function addition theorem.

Next, equation (31) is transformed using Euler's formula and the relational expression δ = 2z ₂ -2z ₁ .

In this formula

Are summarized so as to take the sum from i = 1 to i = N.
Note that k _i ′ = (k ₀ + Δk · M) + Δk × i.

従って、以下の様になる。

この式を再度オイラーの公式を用いて変形する。

となる。 Further, equation (32) is transformed using the following relational equation (33) and equation (26).

Therefore, it becomes as follows.

This equation is transformed again using Euler's formula.

It becomes.

次に式（３５）及び式（３６）より、Ｙ_c´²（ｚ）とＹ_s´²（ｚ）を求める。

右辺第１項から第３項は、特定のｚで大きな値をとり、そこから変位すると急激に減少し略ゼロとなる。例えば、第１項では、

の部分がｚ＝２ｚ₁でＮ²と大きな値をとり、そこから変位すると急激に０に近づく。

は、周期２π／Δｋの周期関数であり、次の周期までの長い区間に亘り略ゼロに近い値となる。従って、第１項は、ｚ＝２ｚ₁で

と大きな値をとりそこから変位すると急激にゼロに近ずき、そのまま次の周期まで略ゼロに近い値をとる。 Similarly, Y _s ′ (z) is obtained as follows.

Next, Y _c ′ ² (z) and Y _s ′ ² (z) are obtained from the equations (35) and (36).

The first term to the third term on the right side take a large value at a specific z, and when displaced from there, the value rapidly decreases and becomes substantially zero. For example, in the first term:

This part takes a large value as N ² at z = 2z ₁ , and approaches zero when it is displaced from there.

Is a periodic function with a period of 2π / Δk, and is a value close to zero over a long interval up to the next period. Therefore, the first term is z = 2z ₁

When it is displaced from there, it suddenly approaches zero and takes a value close to zero until the next cycle.

の様に、総てのｚに対して略ゼロとなる様な関数を含む項を集めたものである。 On the other hand, the term B ₁ (z) is, for example,

In this way, terms including functions that are substantially zero for all z are collected.

となる。
Ｂ₂（ｚ）はＢ₁（ｚ）と同様、総てのｚに対して略ゼロとなる。
従って、

となる。ここで、Ｂ（ｚ）＝Ｂ₁（ｚ）＋Ｂ₂（ｚ）である。
この式は、式（３０）に一致する。 Similarly,

It becomes.
B ₂ (z) is substantially zero for all z, as is B ₁ (z).
Therefore,

It becomes. Here, B (z) = B ₁ (z) + B ₂ (z).
This equation matches equation (30).

(Iii) Method for determining δ not based on standard mirror δ is greatly influenced by the environmental temperature of the apparatus. Since the length of the optical fiber constituting the interferometer ranges from several meters to several tens of meters, even if the optical fiber expands and contracts due to a slight temperature change, it is a value that cannot be ignored compared with the resolution (several μm) of the tomographic image. Therefore, if the apparatus temperature changes, accurate correction cannot be made even if δ = 2z ₂ -2z ₁ is measured in advance. In particular, when the temperature change is different between the sample optical path and the reference optical path, this problem becomes obvious. Therefore, in an environment where the apparatus temperature is likely to change, it is necessary to remeasure δ = 2z ₂ -2z ₁ as appropriate.

However, measurement of δ = 2z ₂ -2z ₁ using a standard mirror is complicated, and it is difficult to construct a tomographic image in an environment in which the apparatus temperature easily changes. In order to avoid such difficulty, a method for determining δ = 2z ₂ -2z ₁ without using a standard mirror is required. An example is shown below.

Ｚは変数である。ここで、Ｙ_1t ²（ｚ）及びＹ_2t ²（ｚ）はｚについての周期関数であり、上記式（３９−５１）の積分範囲を規定するＬはＹ_1t ²（ｚ）及びＹ_2t ²（ｚ）の周期である。この周期は、可変波長光源１，２の波数間隔によって定まる（非特許文献２）。可変波長光源１，２の波数間隔は同一なので、Ｙ_1t ²（ｚ）及びＹ_2t ²（ｔ）の周期は同じである。 In this method, δ is not measured in advance, and δ is directly calculated from an interference signal obtained from a sample for which a tomographic image is to be taken.
First, the first and second interferometers are operated simultaneously to obtain an interference signal from a sample to be measured. From this measurement result, the reflectance distribution Y _1t ² (z) with respect to the output of the first interferometer and the reflectance distribution Y _2t ² (with respect to the output of the second interferometer are calculated using Expressions (23) to (25). z) is calculated respectively. Next, the following cross-correlation function C (z) for these functions is calculated.

Z is a variable. Here, Y _1t ² (z) and Y _2t ² (z) are periodic functions with respect to z, and L defining the integration range of the above equation (39-51) is Y _1t ² (z) and Y _2t ^2. (Z) period. This period is determined by the wave number interval of the variable wavelength light sources 1 and 2 (Non-Patent Document 2). Since the wave number intervals of the variable wavelength light sources 1 and ₂ are the same, the periods of Y _1t ² (z) and Y _2t ² (t) are the same.

上記相互相関関数が最大値となるときのＺの値をＺ_maxとすると、相互相関関数の性質上δ＝Ｚ_maxである。 Both functions Y _1t ² (2z ₁ ) and Y _2t ² (2z ₂ ) are reflectance distributions for the same measurement object, and Y _1t ² (2z ₁ ) = Y (ignoring the difference in the amplitude of the interference signal) _2t ² (2z ₂ ). That is, Y _1t ² (z) ∝Y _2t ² (z + δ). Substituting this equation into equation (39-51) yields:

When the value of Z at which the cross-correlation function is maximized and Z _max, in nature [delta] = Z _max of the cross-correlation function.

That is, by measuring the interference signal to be measured to calculate the cross-correlation function C (Z) and obtaining Z giving the maximum value, the difference δ in the optical path length at that moment can be obtained. A tomographic image can be constructed by calculating equations (27) to (29) from the interference signal using δ.
In order to construct a two-dimensional tomographic image, the interference signal is measured while slightly changing the irradiation position of the measurement light in the horizontal direction, and the reflectance distribution is obtained at each position. Although δ can be determined for each irradiation position of the measurement light, the horizontal scanning of the measurement light is completed in an extremely short time, and therefore, if δ is determined at one point, it is not affected by temperature changes.

  This method has the disadvantage that it takes extra time to calculate the cross-correlation function C (Z), but for samples that do not provide a clear unimodal reflectance distribution like standard mirrors. Is also applicable. That is, the optical path length difference δ can be obtained even when the difference in the position of the reflectance distribution cannot be clearly obtained due to the nature of the sample or noise. Therefore, the difference δ in the optical path length difference can be obtained from the interference signal of the measurement object itself. Of course, this method can also be applied to the determination of the difference δ of the optical path length difference using a standard mirror.

この３ｄＢカプラを測定光を合波するためのカプラ１３として用いるためには、入力ポート６１，６２を入力口とし、出力ポート６３，６４の何れか一方を出力口とすればよい。 (C) Correction of phase generated by coupler (c-1) Specific example of coupler A directional coupler is often used as a 3 dB coupler, but has a characteristic of multiplexing after adding a phase difference to the input. . FIG. 8 is a schematic diagram of a 3 dB coupler including a directional coupler. If the inputs are A ₀ and B ₀ , the outputs A and B can be expressed as follows.

In order to use this 3 dB coupler as the coupler 13 for multiplexing the measurement light, the input ports 61 and 62 may be used as input ports, and one of the output ports 63 and 64 may be used as an output port.

で除されているのは、出力ポート６４にも入力光は分割されるためである。 Hereinafter, a case where the input ports 61 and 62 are input ports and the output port 63 is an output port will be described as an example. In this case, as apparent from the equation (39-1), the output light A is obtained by combining A ₀ and B ₀ with phase changes of 0 and −π / 2, respectively. In addition, the right side of the formula (39-1) is

This is because the input light is also divided into the output port 64.

となる。この入力はカプラ１３を構成する３ｄＢカプラの出力ポート６３に入力する。ところで、３ｄＢカプラの特性は入出力を逆転しても同じ式で表すことができる。従って、カプラ１３が第一の干渉計に戻す信号光Ｅ_s1は、式（３９−１）において

とすることによって得られる。尚、ここで矢印は代入することを意味するものとする。従って、

となる。
ｅ^j2kiL´は、カプラ１３を出射した光が試料２４によって反射（又は後方散乱）されて戻って来るまでに生じる位相変化を表す。従って式（３９−３）から明らかな様に、３ｄＢカプラは、第一の干渉計からの測定光Ａ₀には位相変化を生じさせないが、第二の干渉計からの測定光Ｂ₀には−π／２の位相変化をもたらす。 (C-2) Phase Change Generated in Signal Light Next, the phase change generated in the signal light by such a coupler will be described.
As described above, when the measurement light from the first interferometer is A ₀ and the measurement light from the second interferometer is B ₀ , the output light of the coupler 13 is expressed by the equation (39-1). Next, when the optical path length from the 3 dB coupler to the sample is L ′ and the reflectance or backscattering rate of the sample is R, the signal light reflected or backscattered by the sample and returning to the coupler 13 is

It becomes. This input is input to the output port 63 of the 3 dB coupler constituting the coupler 13. By the way, the characteristic of the 3 dB coupler can be expressed by the same equation even if the input and output are reversed. Therefore, the signal light E _s1 returned from the coupler 13 to the first interferometer is expressed by the equation (39-1).

Is obtained. It should be noted that the arrow here means substitution. Therefore,

It becomes.
e ^j2kiL ′ represents a phase change that occurs before the light emitted from the coupler 13 is reflected (or backscattered) by the sample 24 and returned. Therefore, as is clear from the equation (39-3), the 3 dB coupler does not cause a phase change in the measurement light A ₀ from the first interferometer, but does not generate a phase change in the measurement light B ₀ from the second interferometer. A phase change of −π / 2 is brought about.

となる。従って、３ｄＢカプラは、第一の干渉計からの測定光Ａ₀には−π／２の位相変化を、第二の干渉計からの測定光Ｂ₀には−πの位相変化をもたらす。 Similarly, the signal light E _s2 re-input to the second interferometer is

It becomes. Accordingly, the 3 dB coupler causes a phase change of −π / 2 in the measurement light A ₀ from the first interferometer and a phase change of −π in the measurement light B ₀ from the second interferometer.

(C-3) Influence on Interference Signal The influence of such a phase change on the interference signal will be described using the apparatus configuration shown in FIG. 1 as an example. The coupler 13 is a 3 dB coupler as shown in FIG. 8, the input ports 61 and 62 are optically connected to the input / output ports 14 and 15 of the circulators 9 and 10, respectively, and the output port 63 is optically connected to the collimator lens 27. Suppose that

が併存する。しかし、「（３）原理」で述べた通り、可変波長光源１の出力光を分割して得られる参照光は、可変波長光源１に起因する成分Ａ₀のみと干渉する。一方、可変波長光源１に起因する成分Ａ₀は、カプラ１３によって位相変化を受けない。従って、第一の干渉計の出力は、以下の様になる。

In such a case, the output of the first interferometer is not affected by the phase change by the coupler 13. The first interferometer causes the signal light represented by Expression (39-3) and the reference light obtained by dividing the output light of the wavelength light source 1 to interfere with each other. In this signal light, a component A ₀ based on the wavelength light source 1 and a component based on the variable wavelength light source 2 are represented by the equation (39-3).

Coexist. However, as described in “(3) Principle”, the reference light obtained by dividing the output light of the variable wavelength light source 1 interferes with only the component A ₀ caused by the variable wavelength light source 1. On the other hand, the component A ₀ resulting from the variable wavelength light source 1 is not subjected to a phase change by the coupler 13. Accordingly, the output of the first interferometer is as follows.

となる。各変数の意味は、式（１３）と同じである。この式から明らかなように、カプラ１３が第二の干渉計に及ぼす影響は、干渉光Ｖ₂（ｋ₂）の強度を１／２にすると伴に位相を−πシフトさせる。 In other words, the influence of the coupler 13 on the first interferometer is only to halve the intensity of the interference light V ₁ (k ₁ ). The meaning of each variable is the same as in equation (11).
On the other hand, in the second interferometer, the component B ₀ caused by the variable wavelength light source 2 is subjected to the phase change −π by the coupler 13 as described above. Therefore, the interference light V ₂ (k ₂ ) is

It becomes. The meaning of each variable is the same as in equation (13). As is apparent from this equation, the influence of the coupler 13 on the second interferometer shifts the phase by −π as the intensity of the interference light V ₂ (k ₂ ) is halved.

(C-4) Effect of reflectance distribution on measured value (i) Generalization of phase change amount Such a phase change causes a reflectance distribution (or backscattering rate distribution) in the depth direction Y _t ′ ² (z ). To generalize the description, let φ be the phase change amount of the signal light derived from the variable wavelength light source 2 that is generated by reciprocating the coupler 13. When a 3 dB coupler including a directional coupler is used as the coupler 13, φ = −π as described in “(c-3) Influence on interference signal”.

但し、

である。
δ＝２ｚ₂−２ｚ₁なる関係を用いて、式（３９−６）を変形する。

(Ii) Y _c 'first derived in (z), Y _c' derives a (z). First, the equation (31) is modified in consideration of the phase change amount φ by the coupler 13.

However,

It is.
Equation (39-6) is transformed using the relationship δ = 2z ₂ -2z ₁ .

まず、この関係式を導く。

ここで、式（３３）を用いる。

従って、式（３９−９）が導けた。この式を用いて、式（３９−８−１）を変形する。

Expression (39-8-1) can be modified using the following relational expression.

First, this relational expression is derived.

Here, Formula (33) is used.

Therefore, Formula (39-9) was derived. Using this equation, equation (39-8-1) is transformed.

の場合、Ｙ_c´（ｚ）は、ｚ＞０の領域ではｚ＝２ｚ₁を除いては略ゼロとなる。従って、この様な場合には式（３９−１２）はｚ＞０では以下の様に表すことができる。

ここでＡ（ｚ）は、式（３９−１２）においてｚ＞０において略ゼロとなる項を集めたものである。 The reflectance distribution Y _c ′ (z) represented by the equation (39-12) takes a large value at z = −2z ₁ , 2z ₁ , −δ−2z ₂ and suddenly approaches zero when it is away from it. On the other hand, in the measurement of OFDR-OCT, the measurement object is arranged so that z ₁ > 0 and z ₂ > 0 so that a folded image does not occur. Therefore δ + 2z ₂ > 0,

In this case, Y _c ′ (z) is substantially zero in the region where z> 0, except for z = 2z ₁ . Therefore, in such a case, the equation (39-12) can be expressed as follows when z> 0.

Here, A (z) is a collection of terms that are substantially zero when z> 0 in Formula (39-12).

Formula (39-13) can be further modified as follows.

This equation can be further modified as follows.

This equation can be further modified as follows.

但し、

である。
δ＝２ｚ₂−２ｚ₁なる関係を用いて、式（３９−６）を変形する。

(Iii) Y _s 'derivation of (z) Next, Y _s' to derive the (z).

However,

It is.
Equation (39-6) is transformed using the relationship δ = 2z ₂ -2z ₁ .

まず、この関係式を導く。

ここで、式（３３）を用いる。

従って、式（３９−１８）が導けた。この式を用いて、式（３９−８−１７）を変形する。

By the way, (39-17) can be modified using the following relational expression.

First, this relational expression is derived.

Here, Formula (33) is used.

Therefore, Formula (39-18) was derived. Using this equation, equation (39-8-17) is transformed.

であれば、ｚ＞０の領域にはｚ＝２ｚ₁以外の位置では略ゼロとなる。従って、この様な場合には、式（３９−２１）はｚ＞０では以下の様に表すことができる。

ここでＣ（ｚ）は、式（３９−２１）においてｚ＞０において略ゼロとなる項を集めたものである。 The reflectance distribution Y _s ′ (z) represented by the equation (39-21) takes large values at z = 2z ₁ , −2z ₁ , and −δ−2z ₂ , and suddenly approaches zero when separated from it. On the other hand, in the measurement of OFDR-OCT, the measurement object is arranged so that z ₁ > 0 and z ₂ > 0 so that a folded image does not occur. Therefore, δ + 2z ₂ > 0, ie

Then, in the region of z> 0, it is substantially zero at positions other than z = 2z ₁ . Therefore, in such a case, the equation (39-21) can be expressed as follows when z> 0.

Here, C (z) is a collection of terms that are substantially zero when z> 0 in Formula (39-21).

Formula (39-22) can be further modified as follows.

This equation can be further modified as follows.

This equation can be further modified as follows.

ここでＤ（ｚ）は、ｚ＞０において略ゼロとなる項を集めたものである。
即ち、

となる。 (Iv) 'to derive the last _{^{2 (z) Y t' Y}} t to derive the ² (z). Here, Formula (39-13-1) and Formula (39-23) are used.

Here, D (z) is a collection of terms that are substantially zero when z> 0.
That is,

It becomes.

The first term on the right side of Equation (39-24) is the same as the reflectance distribution function when there is no phase change due to the coupler 13. The second term on the right side is a term representing the influence of the phase change. When φ = 0, ± 2π..., the second term is zero, and the reflectance distribution function is not affected, so that an accurate reflectance distribution can be obtained. When φ ≠ 0, ± 2π, the reflectance distribution function is deformed. However, the second term faults without the so becomes substantially zero in the non-similar z = 2z ₁ and paragraph 1, z = second term in 2z ₁ phase correction if not too large compared to the first term Image construction is possible.

However, when φ = π, ± 3π,... And N = 2M, the second term becomes equal to the first term at z = 2z ₁ , and Y _t ′ ² (2z ₁ ) = 0. Therefore, it is preferable to perform the following phase correction.

(C-5) Phase correction 1
In order to correct the phase change φ due to the coupler 13, the calculation formulas of Y _c ′ (z) and Y _s ′ (z) may be corrected as follows.

但し、δ＝２ｚ₂−２ｚ₁，ｋ_i＝ｋ₀＋Δｋ×ｉ，ｋ_i´＝（ｋ₀＋Δｋ×Ｍ）＋Δｋ×ｉであり、

とする。Ｅ（ｚ）は、ｚ＞０で略ゼロとなる関数である。 The reason why correction is possible with the above formula will be described below. First, equation (39-25) is modified.
Even when the phase change φ is caused by an optical member other than the coupler 13, the same correction can be made. In the case where a plurality of optical members cause a phase change, the phase change φ is the difference between the phase changes generated in the signal light and the reference light by these optical members, that is, the phase change generated in the interfering light after combining. That's fine.

Where δ = 2z ₂ −2z ₁ , k _i = k ₀ + Δk × i, k _i ′ = (k ₀ + Δk × M) + Δk × i,

And E (z) is a function that becomes substantially zero when z> 0.

但し、δ＝２ｚ₂−２ｚ₁，ｋ_i＝ｋ₀＋Δｋ×ｉ，ｋ_i´＝（ｋ₀＋Δｋ×Ｍ）＋Δｋ×ｉであり、

とする。Ｆ（ｚ）は、ｚ＞０で略ゼロとなる関数である。 Next, the equation (39-26) is modified.

Where δ = 2z ₂ −2z ₁ , k _i = k ₀ + Δk × i, k _i ′ = (k ₀ + Δk × M) + Δk × i,

And F (z) is a function that becomes substantially zero when z> 0.

但し、

とし、Ｇ（ｚ）はｚ＞０で略ゼロとなる関数である。
このＧ（ｚ）は、ｚ−２ｚ₁で大きな値をとりそれ以外では略ゼロとなる。即ち、式（３３−３５）、式（３３−３６）を用いてカプラ１３による位相変化を補正することができる。 Finally, Y _t ″ ² (z) = Y _c ″ ² (z) + Y _s ″ ² (z) is obtained. From the equations (39-27) and (39-28),

However,

G (z) is a function that becomes substantially zero when z> 0.
This G (z) takes a large value at z-2z ₁ and is substantially zero otherwise. That is, the phase change due to the coupler 13 can be corrected using the equations (33-35) and (33-36).

(C-6) Phase correction 2
The phase change by the coupler 13 can be corrected by the numerical processing as described above, but can also be corrected by using the phase compensation circuit 71 in the difference reference optical paths 19 and 20 as shown in FIG. By providing the phase compensation circuit 71, the reference optical path has a configuration similar to that of the measurement light irradiation system, and is different in that a reflection mirror 72 is disposed instead of the sample 24. The phase compensation circuit 71 includes circulators 9A and 10A, a coupler 13A, a collimator lens 14A, a galvano mirror 15A, an objective lens 16A, and a reflection mirror 72 provided on the reference light optical paths 19 and 20 side. However, the same phase change as that of the signal light occurs.

従って、差動増幅器１２の出力は以下の様になる。

The signal light E _s2 and the reference light E _r2 of the second interferometer 73 in the circuit of FIG. 9 can be expressed as follows.

Therefore, the output of the differential amplifier 12 is as follows.

  This equation indicates that the phase change given to the signal light by the coupler 13 is canceled out by the phase change given to the reference light by the phase compensation circuit 71. That is, the output of the second interferometer 73 is compensated by the phase compensation circuit 71. Similarly, the output of the first interferometer 74 cancels out the phase change caused by the coupler 13, so if the optical path length difference of each interferometer is corrected, the reflectance distribution in the depth direction (without special data processing) ( Or a backscatter distribution).

  When a coupler that does not give a phase change to the signal light of the first interferometer, such as a 3 dB coupler composed of a directional coupler, is used, the reference optical path of the first interferometer is not necessarily the phase compensation optical path. There is no need to connect.

(Example 2)
Next, an example in which three or more wavelength variable light sources having different wavelength scanning ranges are used will be described. In order to generalize the description, the number of variable wavelength light sources is K (an integer of 3 or more).

(1) Apparatus Configuration FIG. 10 shows a schematic diagram of an apparatus used in this embodiment. The configuration of the apparatus is basically the same as that of the first embodiment, and is composed of K interferometers and that there are K input ports of the coupler 42 that bundles the measurement lights of the respective interferometers. Is different.
Such a coupler is hereinafter referred to as a K: 1 coupler, but can be easily configured using a multimode waveguide. Further, a plurality of 2: 1 couplers 51 can be formed by combining a plurality of them as shown in FIG. 11A (FIG. 11A is an example of a 4: 1 coupler). Furthermore, as shown in FIG. 11B, the collimator lens 52 and the optical fiber 53 can be combined. In the vicinity of the focal point of the lens, that is, the position where the lens collects parallel rays, the light becomes a narrow and substantially parallel beam due to the interference effect. By arranging the end faces of the plurality of optical fiber outputs so as to be aligned with this portion (waist 54), the light emitted from any of the optical fibers is collimated into parallel light by the collimating lens. That is, a coupler is configured, and if the number of fibers arranged on the waist is N, an N: 1 coupler can be configured.

(2) Operation method / correction method The operation method is basically the same as that of the first embodiment, and is different in that the number of measurement lights simultaneously irradiated on the sample is three or more. However, each interferometer operates independently. The number has simply increased.
Further, the correction for compensating for the optical path difference and the phase change of the third and subsequent interferometers may be performed in the same manner as the correction for the second interferometer in the first embodiment.

(3) Principle In order to construct a tomographic image by the operation and correction as described above, it is assumed that each interferometer outputs only an interference signal based on the wavelength scanning of each variable wavelength light source. In the first embodiment, the case where the number of interferometers is two has been described. However, here, the case of K units will be generalized and described.
In order to generalize the description, the output of the sth interferometer 41 will be examined (s is an integer of 1 or more and K or less).

ここで、ｌ番目の参照光がカプラ４５に到達した時の電界をｅ_rlとすると、カプラ４５によって合波されて生じる干渉光は以下の様になる。

ここで

は、ｉ＝ｌの項を除きｉ＝ｌからｉ＝Ｋまでの項の和をとることを意味する。式（４１）の最後の式は三つの部分からなる。第一の部分

は波数に拠らない一定の成分であり、差動増幅器４６の働きによりゼロとなる成分である。第二の部分２Ｒｅ（ｅ_rl ^*ｅ_sl ^*）は、波長走査に伴なって振動する干渉成分である。第三の成分

は異なった可変波長光源からの放射光の干渉を表す成分であるが、実施例１で述べたように異なる光源からの光を合波しても干渉はしないのでこの項はゼロとなる。 The variable wavelength light incident on the sample optical path of the l-th interferometer 41 is combined with the measurement light from the other interferometer by the K: 1 coupler 42 and irradiated on the sample 43. The signal light reflected or backscattered by the sample 43 is incident again on the K: 1 coupler 42 and divided and coupled to the reference light by the coupler 45 via the circulator 44.
The measurement light generated by the i-th interferometer is reflected (or back-scattered) by the sample, and the resulting signal light enters the l-th interferometer and reaches the coupler 45 as an electric field e _si. And The electric field E _sl of the signal light incident on the coupler 45 is the sum of e _si and can be expressed as follows.

Here, _assuming that the electric field when the l-th reference light reaches the coupler 45 is e _rl , the interference light generated by being combined by the coupler 45 is as follows.

here

Means taking the sum of the terms from i = 1 to i = K except for the term i = 1. The last equation of equation (41) consists of three parts. First part

Is a constant component that does not depend on the wave number, and is a component that becomes zero by the action of the differential amplifier 46. The second portion 2Re (e _rl ^* e _sl ^* ) is an interference component that vibrates with the wavelength scanning. Third ingredient

Is a component representing interference of radiated light from different variable wavelength light sources, but this term becomes zero because there is no interference even if light from different light sources are combined as described in the first embodiment.

Therefore, the output of the differential amplifier 46 is only an interference signal due to the light emitted from the variable wavelength light source 47.
That is, even if the measurement lights of three or more interferometers are combined by a K: 1 coupler, the output of each interferometer is only an interference signal based on the wavelength scanning of each variable wavelength light source.
The present invention has been described above based on the new OCT proposed by the present inventors (Patent Document 1). However, the present invention is also applicable to other OCTs that use a variable wavelength light source. For example, the present invention can also be applied to OCT (Non-Patent Document 3) that continuously scans the wavelength as a light source, and OCT (Patent Document 3) that has not been filed by the present inventors.

1 is a schematic diagram of a high-speed and high-resolution OFDR-OCT apparatus according to Embodiment 1 of the present invention. It is the figure which represented the wavelength change of the light which a variable wavelength light source radiate | emits with respect to time. It is a block diagram of a variable wavelength light generator. It is another block diagram of a variable wavelength light generator. It is the figure which plotted the output of the differential amplifier with respect to the scanning wave number. It is the schematic of the high-speed and high-resolution OFDR-OCT apparatus which adjusted the optical path length difference using the optical delay device. Y _t ^'2 a (z) is a diagram showing an example graphed. It is the schematic of 3 dB coupler which consists of a directional coupler. It is the schematic of the high-speed and high-resolution OFDR-OCT apparatus using a phase compensation circuit. It is the schematic of the high-speed and high-resolution OFDR-OCT apparatus which concerns on Example 2 of this invention. It is a figure which shows the structural example of a coupler. It is the schematic of the tomogram imaging device of the anterior ocular segment using OFDR-OCT method which the present inventors developed. It is a block diagram of measurement light irradiation / signal light capturing means. It is a figure which shows the mode of reflection of measurement light in case a measuring object has only one reflective surface. It is a conceptual diagram of the light source for high resolution which combined the some variable wavelength light source in order to improve the spatial resolution of OFDR-OCT. It is a figure which shows the output spectrum of the light source for high resolution which consists of two variable wavelength light sources.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Variable wavelength light source 3, 4 Wavelength scanning area 5, 6, 7, 8 Coupler 9, 10 Circulator 11, 12 Differential amplifier 13 Coupler 14 Collimator lens 15 Galvano mirror 16 Objective lens 9A, 10A Circulator 13A Coupler 14A Collimator lens 15A Galvano mirror 16A Objective lens 17, 18 Sample optical path 19, 20 Reference optical path 21 A / D converter 22 Arithmetic controller 23 Measuring light irradiation system / Signal light receiving system 24 Measurement object (sample)
25 Variable Wavelength Light Generator 26, 26A, 26B, 26C Control Circuit 31, 32 Optical Delay Device 41 Sth Interferometer 42 K: 1 Coupler 43 Measurement Object (Sample)
44 circulator 45 coupler 46 differential amplifier 51 2: 1 coupler 52 collimator lens 53 optical fiber 54 beam waist 61, 62 input port 63, 64 output port 71 phase compensation circuit 72 reflecting mirror 73 second interferometer 74 first interference Total

Claims (11)

A plurality of variable wavelength light generating means having different wave number scanning ranges;
Control means for simultaneously scanning the wavelength of the plurality of variable wavelength light generating means;
Respective means for dividing each output light of the variable wavelength light generating means into measurement light and reference light;
Means for combining the respective measurement lights into one measurement light;
Means for irradiating the measurement object with the one measurement light, and capturing the signal light reflected or backscattered by the measurement object by the one measurement light;
Means for splitting the signal light;
Respective means for individually combining the split signal light and the respective reference light;
Respective means for measuring the intensity of the individual output lights combined by the respective means for individually multiplexing for each wave number of the plurality of variable wavelength light generating means,
A position where the measurement light is reflected or back-scattered by the measurement object and a reflection or back-scattering intensity from the set of intensity of the individual output lights measured for each wave number by the means for measuring the measurement object. Means for specifying the depth direction of
The means for specifying is a Fourier transform of the set of individual output light intensities with respect to the wave number;
Each measurement light and each signal light traveling from each of the means for dividing to each of the means for combining individually travels, which is obtained in advance as a standard sample of a measuring object consisting of one reflecting surface. Find the difference between the sum of the optical path lengths and the optical path lengths of the respective reference lights combined individually from the respective means for dividing,
Based on the difference between the difference between the other of said respective relative one selected from among the difference of the respective characteristics and to Luo Putikaru in that it comprises means for correcting the effect of the difference of each has on the building tomogram -Coherence tomography device. A plurality of variable wavelength light generating means having different wave number scanning ranges;
Control means for simultaneously scanning the wavelength of the plurality of variable wavelength light generating means;
Respective means for dividing each output light of the variable wavelength light generating means into measurement light and reference light;
Means for combining the respective measurement lights into one measurement light;
Means for irradiating the measurement object with the one measurement light, and capturing the signal light reflected or backscattered by the measurement object by the one measurement light;
Means for splitting the signal light;
Respective means for individually combining the split signal light and the respective reference light;
Respective means for measuring the intensity of the individual output lights combined by the respective means for individually multiplexing for each wave number of the plurality of variable wavelength light generating means,
A position where the measurement light is reflected or back-scattered by the measurement object and a reflection or back-scattering intensity from the set of intensity of the individual output lights measured for each wave number by the means for measuring the measurement object. Means for specifying the depth direction of
The means for specifying is a Fourier transform of the set of individual output light intensities with respect to the wave number;
The position where the one measurement light is reflected or backscattered and the reflected or backscattered intensity obtained by Fourier-transforming the wavenumber for each wavenumber scanning range with respect to the set of intensities of the individual output lights. A cross-correlation function is synthesized from each function specified in the depth direction of the measurement target,
From the cross-correlation function, the sum of the optical path lengths of the measurement light and the signal light traveling from the respective means for dividing to the respective means for multiplexing individually, and the respective means for dividing From the respective optical path lengths of the reference light to the respective means for individually combining, the respective differences are obtained,
Based on the difference between the difference between the other of said respective relative a selected one of the difference of the respective characteristics and be Luo Putikaru-in that it comprises means for correcting the effect of the difference of each has on the building tomogram Coherence tomography device. Optical coherence tomography apparatus according to claim 1 or 2, wherein the means for said one of the measuring light, and means for dividing the signal light are the same means. Based on the ratio of the amplitudes of the individual output lights obtained in advance as a standard sample to be measured consisting of one reflecting surface,
The optical coherence tomography apparatus according to any one of claims 1 to 3, further comprising means for correcting the intensity of the individual output light. Means for correcting the influence on the tomographic image construction,
The position coordinate of the Fourier nucleus of the Fourier transform is obtained by adding the difference to the position coordinate for each wave number scanning range of the plurality of variable wavelength light generating means . optical coherence tomography device according to any one of 4. Determining the phase change caused to the individual output light by the optical path traveled by the respective measurement light, the respective signal light, the one measurement light, and the respective reference light;
The Fourier transform for each wave number scanning range of the plurality of variable wavelength light generating means is a product of the wave number and position coordinates of the Fourier nucleus, and the phase change is added to the product. The optical coherence tomography apparatus according to any one of claims 1 to 5 . The optical coherence tomography apparatus according to any one of claims 1 to 6 , comprising the plurality of variable wavelength light generating means and the wavelength scanning control means. Variable wavelength light generator for tomography equipment. 8. The variable wavelength light generator for an optical coherence tomography device according to claim 7 , wherein the variable wave number range is 0.2 μm− ¹ or more with respect to the wave number. 9. The variable wavelength light generator for an optical coherence tomography device according to claim 7 or 8, wherein a wave number scanning period of the variable wavelength light source is 5 ms or less. The variable wavelength light generator for an optical coherence tomography device according to any one of claims 7 to 9 , wherein the variable wavelength light source is capable of discretely switching wave numbers. The variable wavelength light generator for an optical coherence tomography device according to any one of claims 7 to 10 , wherein the variable wavelength light source is a variable wavelength laser.

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