JP4907279B2 - Optical tomographic imaging system - Google Patents

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 TD-OCT (Time Domain OCT) measurement, and measurement light is generated by inserting a probe into a body cavity from a forceps port of an endoscope through a forceps channel. It is guided in the body cavity.

  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, TD-OCT 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 substantially coincide with each other, and the measurement is performed by changing the optical path length of the reference light. The measurement position (measurement depth) with respect to the object is changed.

  When performing OCT measurement by inserting a probe into a body cavity, it is necessary to disinfect and clean the probe after use, so that the probe is detachable from the main body of the optical tomographic imaging apparatus. That is, a plurality of probes used in the optical tomographic imaging apparatus are prepared, and the probes can be replaced for each measurement. At this time, each probe has an individual difference due to a manufacturing error or the like in the length of the optical fiber, and there is a problem that the optical path length on the measurement light side changes every time the probe is changed. Therefore, in Patent Document 1, the optical path length of the measurement light and the reference light is reduced by adjusting the optical path length of the reference light using the reflected light from the inner wall surface of the tube (sheath) covering the optical fiber in the probe. It is supposed to match.

By the way, as a method for acquiring a tomographic image at a high speed without changing the optical path length of the reference light as described above, the interference light is detected while changing the frequency of the light emitted from the light source with time. An OCT (Swept source OCT) apparatus has been proposed. The SS-OCT apparatus uses a Michelson interferometer to sweep the frequency of the light emitted from the light source without changing the optical path length to cause interference between the reflected light and the reference light, and to generate an interferogram interference intensity signal. obtain. A tomographic image is generated by Fourier transforming the interferogram signal in the optical frequency domain.
JP 2003-172690 A US Pat. No. 5,565,986

  As described above, in SS-OCT measurement, reflection information in each depth direction can be obtained by performing frequency analysis, and therefore it is not necessary to substantially match the optical path lengths of the measurement light and the reference light. However, in practice, if the optical path length difference increases, the spatial frequency of the interference signal increases, so that the interference signal detected by the detection time of a photodiode such as a CCD that detects the interference light is limited. There is a problem that S / N deteriorates. Therefore, also in SS-OCT measurement, the optical path length is adjusted so that the optical path lengths of the measurement light and the reference light substantially match, and the measurement start position is set so that the measurement target is included in the measurable region. There is a need.

  Here, the measurable range (measurement depth) in which tomographic images can be acquired by SS-OCT measurement is inversely proportional to the wavelength fluctuation width per unit time of the light source, and the resolution in the optical axis direction when acquiring tomographic images is the wavelength. The higher the fluctuation range, the higher. For this reason, when a high-resolution tomographic image is acquired within a predetermined time, the measurable range (measurement depth) is narrow. Therefore, in an SS-OCT apparatus that acquires a high-resolution tomographic image, when acquiring a tomographic image in order to adjust the measurement start position, the measurable range (measurement depth) is narrow, and the optical path length difference between the measurement light and the reference light is calculated. There is a problem that it takes time and effort to drive into the measurement range. Similarly, for example, when it is desired to observe a layer configuration such as a stomach wall, there is a problem that a tomographic image cannot be acquired within a desired measurable range (measurement depth).

  Therefore, the present invention provides an optical tomographic imaging apparatus that obtains optical tomographic information by irradiating a measurement target with measurement light while sweeping the wavelength at a constant period and performing frequency analysis of interference light at that time. It is an object of the present invention to provide an optical tomographic imaging apparatus capable of switching the measurable range (measurement depth) according to the above and having improved convenience.

An optical tomographic imaging apparatus of the present invention includes a light source unit that emits light while sweeping a wavelength at a constant period;
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 and the reference light from the measurement object when the measurement light divided by the light dividing means is irradiated on the measurement object;
Interference light detection means for detecting interference light between the reflected light and the reference light multiplexed by the multiplexing means;
In an optical tomographic imaging apparatus having tomographic information acquisition means for acquiring tomographic information of the measurement object by performing frequency analysis on the interference light detected by the interference light detection means,
Switching between a first detection mode for detecting the interference light with a first wavelength resolution and a second detection mode for detecting the interference light with a second wavelength resolution higher than the first wavelength resolution. It has a detection mode control means.

  Since the wavelength is the reciprocal of the frequency, “the first detection mode that detects the interference light with the first wavelength resolution and the second wavelength resolution that is higher than the first wavelength resolution” The “second detection mode for detecting the interference light” means “the first detection mode for detecting the interference light with the first frequency resolution and the second wavelength resolution that is higher in frequency resolution than the first frequency resolution”. In other words, the second detection mode in which the interference light is detected. Similarly, the light source unit can be rephrased as a light source unit that emits light while sweeping the frequency at a constant period.

  Further, “reflected light from the measurement object when the measurement light is irradiated onto the measurement object” means light reflected from the measurement object or scattered light from the measurement object.

  The detection mode control means controls the light source unit so that the wavelength fluctuation width per unit time of the light when the wavelength is swept is smaller in the second detection mode than in the first detection mode. Thus, the wavelength resolution may be increased. The light source unit can use various wavelength variable laser devices, for example, as long as the light source unit emits light while sweeping the wavelength (frequency) at a constant period.

  On the other hand, the detection mode control means controls the interference light detection means so that the sampling frequency when detecting the interference light is higher in the second detection mode than in the first detection mode, thereby increasing the wavelength resolution. You may do.

  The first detection mode is an image acquisition mode for acquiring a tomographic image of the measurement object, and the second detection mode is a measurement start position adjustment for adjusting a position for obtaining a tomographic image signal in the depth direction of the measurement object It may be a mode.

  You may provide the optical path length adjustment means which adjusts the optical path length of the said measurement light or the said reference light.

  A light source unit that emits light while sweeping the wavelength at a constant period; a light dividing unit that divides the light emitted from the light source unit into measurement light and reference light; and the light divided by the light dividing unit Multiplexing means for multiplexing the reflected light from the measurement object and the reference light when the measurement light is irradiated to the measurement object, and the reflected light and the reference light combined by the multiplexing means Optical tomographic image having interference light detecting means for detecting interference light with the tomographic information, and tomographic information acquiring means for acquiring tomographic information of the measurement object by performing frequency analysis on the interference light detected by the interference light detecting means In the measurement apparatus, the measurable range (measurement depth) is large when the wavelength resolution when detecting the interference light is high, and is small when the wavelength resolution is low. Detection mode And a second detection mode in which the interference light is detected with a second wavelength resolution that is higher than the first wavelength resolution, so that the user can change the mode according to the purpose of use. The measurable range (measurement depth) can be switched, and the convenience of the optical tomographic imaging apparatus is improved.

  Further, the light source unit is controlled so that the wavelength fluctuation width per unit time of the light when the wavelength is swept is smaller in the second detection mode than in the first detection mode, and the second detection mode is controlled. If the wavelength resolution at the time is increased, the measurable range (measurement depth) can be easily switched.

  The interference light detection means is controlled to increase the wavelength resolution in the second detection mode so that the sampling frequency for detecting the interference light is higher in the second detection mode than in the first detection mode. Then, the measurable range (measurement depth) can be switched without increasing the acquisition time for acquiring the tomographic image.

  The first detection mode is an image acquisition mode for acquiring a tomographic image of the measurement target, and the second detection mode is a measurement start position adjustment mode for adjusting a position at which a tomographic image signal is obtained in the depth direction of the measurement target. If this is the case, the measurement target is acquired as a tomographic image in the measurement start position adjustment mode because the wavelength resolution can be increased in the measurement start position adjustment mode to increase the measurable range (measurement depth) and make it easier to find the measurement target. The measurement start position can be adjusted efficiently.

  Embodiments of an optical tomographic imaging apparatus according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic view showing a preferred embodiment of the optical tomographic imaging apparatus of the present invention. The optical tomographic imaging apparatus 1 acquires, for example, a tomographic image of a measurement target such as a living tissue or cell in a body cavity by SS-OCT measurement, and includes a light source unit 10 that emits laser light L, and a light source unit 10. A light splitting means 3 for splitting the laser light L emitted from the light into a measurement light L1 and a reference light L2, an optical path length adjusting means 20 for adjusting the optical path length of the reference light L2 split by the light splitting means 3, and a light A probe 30 that guides the measurement light L1 divided by the dividing means 3 to the measurement target S, and reflected light L3 and reference light L2 from the measurement target when the measurement light S1 is irradiated from the probe 30 to the measurement target S. , The interference light detection means 40 for detecting the interference light L4 between the reflected light L3 and the reference light L2, and the interference light detection means 40 detected by the interference light detection means 40. Interfering light L4 And an image obtaining means 50 for obtaining a tomographic image of the detected measurement target S the intensity of the interference light at each depth position of the measurement object by wavenumber analysis.

  The light source unit 10 emits the light L while sweeping the frequency at a constant period, and is composed of, for example, a mode-locked semiconductor laser. Specifically, the light source unit 10 includes a semiconductor optical amplifier (semiconductor gain medium) 11 and an optical fiber FB10, and the optical fiber FB10 is connected to both ends of the semiconductor optical amplifier 11. . The semiconductor optical amplifier 11 has a function of emitting weak emission light to one end side of the optical fiber FB10 by injecting drive current and amplifying light incident from the other end side of the optical fiber FB10. When a driving current is supplied to the semiconductor optical amplifier 11, a pulsed laser beam L is emitted to the optical fiber FB1 by an optical resonator formed by the semiconductor optical amplifier 11 and the optical fiber FB10. .

  Further, an optical branching device 12 is coupled to the optical fiber FB10, and a part of the light guided in the optical fiber FB10 is emitted from the optical branching device 12 to the optical fiber FB11 side. The light emitted from the optical fiber FB11 is reflected by a rotary polygon mirror (polygon mirror) 16 through the collimator lens 13, the diffraction grating element 14, and the optical system 15. Then, the reflected light enters the optical fiber FB11 again through the optical system 15, the diffraction grating element 14, and the collimator lens 13.

  Here, the rotating polygonal mirror 16 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 15. As a result, only the light having a specific frequency region out of the light dispersed in the diffraction grating element 14 is returned to the optical fiber FB11 again. The frequency of light returning to the optical fiber FB11 is determined by the angle between the optical axis of the optical system 15 and the reflecting surface. Then, light having a specific frequency range incident on the optical fiber FB11 is incident on the optical fiber FB10 from the optical splitter 12, and as a result, laser light L having a specific frequency range is emitted to the optical fiber FB1 side. ing. Therefore, when the rotary polygon mirror 16 rotates at a constant speed in the direction of the arrow R1, the wavelength of the light incident on the optical fiber FB11 again is swept at a constant period as shown in FIG. That is, the laser light L having a wavelength swept at a constant period is emitted from the light source unit 10 to the optical fiber FB1 side.

  1 comprises, for example, a 2 × 2 optical fiber coupler, and divides the laser light L guided from the light source unit 10 through the optical fiber FB1 into the measurement light L1 and the reference light L2. It is like that. The light splitting means 3 is optically connected to the two optical fibers FB2 and FB3, respectively. The measurement light L1 is guided by the optical fiber FB2 side, and the reference light L2 is guided by the optical fiber FB3 side. In FIG. 1, the light splitting means 3 also functions as the multiplexing means 4.

  The probe 30 is optically connected to the optical fiber FB2, and the measurement light L1 is guided from the optical fiber FB2 to the probe 30. The probe 30 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 OC.

  On the other hand, the optical path length adjusting means 20 is disposed on the side of the optical fiber FB3 where the reference light L2 is emitted. The optical path length adjusting unit 20 changes the optical path length of the reference light L2 in order to adjust the measurement start position with respect to the measurement target S, and includes a collimator lens 21 and a reflection mirror 22. The reference light L2 emitted from the optical fiber FB3 passes through the collimator lens 21, is reflected by the reflection mirror 22, and enters the optical fiber FB3 through the collimator lens 21 again.

  Here, the reflection mirror 22 is disposed on the movable stage 23, and the movable stage 23 is provided so as to be movable in the direction of arrow A by the mirror moving means 24. When the movable stage 23 moves in the direction of arrow A, the optical path length of the reference light L2 is changed.

  The combining means 4 is composed of a 2 × 2 optical fiber coupler, and combines the reference light L2 that has been subjected to frequency shift and optical path length change by the optical path length adjusting means 20 and the reflected light L3 from the measuring object S. The light is emitted to the interference light detection means 40 side through the optical fiber FB4.

  The interference light detection means 40 detects the interference light L4 between the reflected light L3 and the reference light L2 combined by the multiplexing means 4 at a predetermined sampling frequency, and measures the light intensity of the interference light L4. InGaAs-based photodetectors 41a and 41b, and an arithmetic unit 42 that performs balance detection of the detection value of the photodetector 41a and the detection value of the photodetector 41b. The interference light L4 is divided into two by the light dividing means 3 and detected by the photodetectors 41a and 41b.

  The image acquisition means 50 detects the intensity of the reflected light L3 at each depth position of the measurement target S by Fourier transforming the interference light L4 detected by the interference light detection means 40, and obtains a tomographic image of the measurement target S. get. The acquired tomographic image is displayed on the display device 60.

  Here, the detection of the interference light L4 and the generation of the image in the interference light detection means 40 and the image acquisition means 50 will be briefly described. Details are described in “Mitsuo Takeda,“ Optical Frequency Scanning Spectrum Interference Microscope ”, Optical Technology Contact, 2003, Vol41, No7, p426-p432”.

When the measurement light L1 is irradiated onto the measurement object S, interference fringes with respect to each optical path length difference l when the reflected light L3 from the depth of the measurement object S and the reference light L2 interfere with each other with various optical path length differences. S (l) is the light intensity I (k) detected by the interference light detection means 40.
I (k) = ∫ ₀ ^∞ S (l) [1 + cos (kl)] dl (1)
It is represented by Here, k is the wave number, and l is the optical path length difference. Equation (1) can be considered to be given as an interferogram in the optical frequency domain with the wave number k = ω / c as a variable. For this reason, in the image acquisition means 50, the spectral interference fringes detected by the interference light detection means 40 are subjected to frequency analysis by Fourier transform, and S (l) is determined, whereby distance information from the measurement start position of the measurement target S is obtained. And the reflection intensity information are acquired, and a tomographic image is generated. The generated tomographic image is displayed on the display device 60.

  Next, an operation example of the optical tomographic imaging apparatus 1 will be described with reference to FIGS. 1 and 2. First, when the movable stage 23 moves in the direction of arrow A, the optical path length is adjusted so that the measurement target S is positioned within the measurable range (measurement depth). Thereafter, a laser beam L having a wavelength swept at a constant period is emitted from the light source unit 10, and the laser beam L is split by the beam splitting unit 3 into the measuring beam L 1 and the reference beam L 2. The measurement light L1 is guided into the body cavity by the probe 30 and irradiated to the measurement object S. Then, the reflected light L3 from 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 40. The detected signal of the interference light L4 is subjected to frequency analysis in the image acquisition means 50, whereby a tomographic image is acquired. Thus, in the optical tomographic imaging apparatus 1 that acquires a tomographic image by SS-OCT measurement, image information at each depth position is acquired based on the frequency and light intensity of the interference light L4. The movement of the reflection mirror 22 in the direction of arrow A is used to adjust the measurement start position.

  By the way, in the SS-OCT measurement described above, if the difference between the optical path lengths of the measurement light L1 and the reference light L2 becomes large, the image quality may be deteriorated due to the expansion of the spatial frequency, the relationship between the sampling periods, and the like. For this reason, it is necessary to adjust the optical path length so that the optical path lengths of the measurement light and the reference light substantially coincide. Here, the measurable range (measurement depth) is inversely proportional to the wavelength variation width ΔΛ of the laser light L, and the resolution when acquiring a tomographic image increases as the wavelength variation width ΔΛ increases (see FIG. 2). That is, when acquiring a high-resolution tomographic image, the measurable range is narrow. Therefore, in an SS-OCT apparatus that acquires a high-resolution tomographic image, when acquiring a tomographic image in order to adjust the measurement start position, the measurable range (measurement depth) is narrow, and the optical path length difference between the measurement light and the reference light is calculated. There is a problem that it takes time and effort to drive into the measurement range.

  Therefore, the optical tomographic imaging apparatus 1 in FIG. 1 switches between a measurement start position adjustment mode for adjusting the measurement start position in the depth direction of the measurement target S and an image acquisition mode for acquiring a tomographic image of the measurement target S. A control means 70 is provided, and the control means 70 controls the light source unit 10 or the interference light detection means 40 so that the wavelength resolution in the measurement start position adjustment mode is higher than the wavelength resolution in the image acquisition mode. .

  That is, as a method for improving the wavelength resolution when detecting interference in the measurement start position adjustment mode, the wavelength fluctuation width per unit time of the light when the wavelength is swept is an image in the measurement start position adjustment mode. The method of controlling the light source unit 10 to increase the wavelength resolution so as to be smaller than that in the acquisition mode, and the sampling frequency when detecting the interference light in the measurement start position adjustment mode than in the image acquisition mode There is a method of increasing the wavelength resolution by controlling the interference light detection means so as to increase the wavelength. This will be described in detail below.

When the optical path length difference between the optical path length ls of the measuring light L1 and the optical path length lr of the reference light L2 is Δl (= | lr−ls |), the interference detected by the interference light detecting means 40 as shown in FIG. The period Γ of the light L4 is
Γ = λ ₀ ² / Δl · τ / ΔΛ (2)
It is represented by Λ ₀ is the center wavelength of the spectrum, τ is the fluctuation period when the wavelength is swept, and ΔΛ is the wavelength fluctuation width (see FIG. 2). Here, FIG. 3A shows a waveform of Δl = 100 μm at a sampling frequency of 500 / τ, FIG. 3B shows a waveform of Δl = 500 μm, and FIG. 3C shows a waveform of Δl = 1000 μm. . 3A to 3C and the above formula (2), the period Γ of the interference light L4 becomes shorter as the optical path length difference Δl becomes larger.

In order to obtain a signal with sufficient resolution, it is necessary to sample four times or more per cycle. This can be expressed in mathematical formulas.
Sampling interval Δt <interfering light Γ / 4 (3)
It becomes. When the expression (3) is not satisfied, the period Γ of the interference light L4 exceeds the resolution of the interference light detection means 40 as shown in FIG. 3C, and the S / N is deteriorated to cause deterioration of the image quality.

The depth Δl _lim of the measuring object S that can be finally measured is calculated from the equations (2) and (3).
Δl _lim = ¼ · (τ / ΔΛ) · λ ₀ ² · (1 / Δt) ·· (4)
It becomes. In Expression (4), the depth Δl _lim of the measurement target S that can measure the tomographic image, that is, the measurable range (measurement depth) is proportional to the reciprocal of the wavelength fluctuation width (ΔΛ / τ) per unit time. It can also be seen that it is proportional to the reciprocal of the sampling interval Δt, that is, the sampling frequency.

  In the image acquisition mode, it is necessary to acquire a tomographic image with good image quality. For this purpose, as described above, it is preferable to increase the measurement resolution by increasing the wavelength fluctuation range ΔΛ. Further, it is necessary to acquire a tomographic image within a predetermined time, and it is preferable that the wavelength sweeping period τ is small. If the sampling frequency is further increased, the sampling time for each sampling is reduced, and if the amount of interference light detected by the interference light detection means 40 is small, a sufficient amount of detected light cannot be secured, and the S of the tomographic image is not obtained. / N may be deteriorated. For this reason, it is not preferable to increase the sampling frequency too much. Considering these conditions, the wavelength fluctuation width ΔΛ, the wavelength sweep period τ, the sampling frequency, etc. in the image acquisition mode are determined. For this reason, usually, the measurable range (measurement depth) from which a tomographic image can be acquired is not very large. Therefore, for example, when the measurable range is several tens of μm and the distance from the probe 30 to the measurement target is several hundred μm away, the position of the measurement target S cannot be recognized even if a tomographic image is acquired.

In the present embodiment, for example, the control unit 70 sets the rotation speed of the rotary polygon mirror 16 in the measurement start position adjustment mode to ½ of the rotation speed of the rotary polygon mirror 16 in the image acquisition mode. Then, the wavelength sweeping period τ is doubled, and as shown in FIG. 5, the light source unit 10 emits the laser light L with the wavelength variation width ΔΛ / τ per unit time halved. As described above, when the wavelength variation width ΔΛ / τ per unit time is decreased (τ / ΔΛ is increased), the wavelength variation width for each sampling in the interference light detection unit 40 is decreased. That is, the apparent wavelength resolution in the interference light detection means 40 is increased. In the present embodiment, the obtainable range Δl _lim shown in Expression (4) is doubled. As a result, a tomographic image in which the measurable range (measurement depth) is doubled can be acquired, and the measurement object S can be easily projected in the tomographic image. The user can adjust the measurement start position quickly and easily while observing the tomographic image.

  In this way, the light source unit 10 is controlled to control the wavelength so that the wavelength fluctuation width per unit time when the wavelength is swept is smaller in the measurement start position adjustment mode than in the image acquisition mode. When the resolution is increased, the acquisition time for acquiring one tomographic image increases. However, since only the measurement start position adjustment is performed, there is no problem in the normal operation for acquiring the tomographic image.

  In addition, even when a wide measurable range (measurement depth) is required, such as when observing a layer structure such as the stomach wall, the measurable range can be obtained by reducing the wavelength fluctuation width per unit time in this way. An optical tomographic image having a large (measurement depth) can be acquired.

Alternatively, the control unit 70 controls the interference light detection unit 40 so that the sampling interval Δt is smaller than that in the image acquisition mode, that is, the sampling frequency (1 / Δt) is larger in the measurement start position adjustment mode. May be. By increasing the sampling frequency of the interference light detection means 40, that is, by increasing the wavelength resolution in the interference light detection means 40, the measurable range Δl _lim increases (see equation (4)), and the measurable range ( A tomographic image having a large measurement depth can be acquired. For this reason, the measurement object S is easily projected in the tomographic image, and the user can adjust the measurement start position quickly and easily while observing the tomographic image. If the sampling frequency is increased, the interference light detection unit 40 cannot obtain a sufficient amount of light and may cause deterioration in image quality. However, in the adjustment operation of the measurement start position, the image quality of the tomographic image is It is sufficient that the existence of the measuring object S is known, and it is not necessary to have high image quality. Further, when the sampling frequency (1 / Δt) is increased, the acquisition time for acquiring one tomographic image does not increase, and the measurement start position can be adjusted quickly.

  The embodiment of the present invention is not limited to the above embodiment. For example, although the case where the wavelength period τ is increased in FIG. 5 is illustrated, the wavelength variation width ΔΛ may be decreased. At this time, the light source unit 10 has two rotating polygon mirrors having different diameters, and a large rotating polygon mirror is used in the image acquisition mode, and a small rotating polygon mirror is used in the measurement start position adjustment mode. Good. Further, the two rotational speeds may be different depending on each mode as described above.

  Further, in FIG. 1, as an example of the light source unit 10 that emits the laser light L while sweeping the wavelength, a configuration using the rotary polygon mirror 16 is illustrated, but a known wavelength tunable laser device can be used. At this time, the control means 70 controls the drive unit of the wavelength tunable laser device so that ΔΛ / τ is smaller than that in the image acquisition mode in the position adjustment mode.

  Furthermore, although the case where the light source unit 10 is controlled and the case where the interference light detection means 40 is controlled is illustrated in the above embodiment, both the light source unit 10 and the interference light detection means 40 may be controlled. good. That is, the sampling frequency in the interference light detection means 40 is increased while reducing the wavelength fluctuation width per unit time in the light source unit 10.

Schematic diagram showing a preferred embodiment of the optical tomographic imaging apparatus of the present invention The figure which shows an example of the wavelength fluctuation of the laser beam at the time of the image acquisition mode which the light source unit of FIG. 1 outputs The figure which shows an example of the interference light detected in the interference light detection means of FIG. The figure which shows an example of the interference light detected in the interference light detection means of FIG. The figure which shows an example of the wavelength fluctuation of the laser beam at the time of the measurement start position adjustment mode which the light source unit of FIG. 1 outputs

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical tomographic imaging apparatus 3 Light splitting means 4 Combined means 10 Light source unit 20 Optical path length adjusting means 30 Probe 40 Interference light detection means 50 Image acquisition means 70 Control means L Light l Each optical path length difference L1 Measuring light L2 Reference light L3 Reflected light L4 Interference light S Measuring object Δl Optical path length difference ΔΛ Wavelength fluctuation range

Claims (4)

A light source unit that emits light while sweeping the wavelength at a constant period;
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 to the measurement object;
Interference light detection means for detecting interference light between the reflected light and the reference light multiplexed by the multiplexing means;
In an optical tomographic imaging apparatus having tomographic information acquisition means for acquiring tomographic information of the measurement object by performing frequency analysis on the interference light detected by the interference light detection means,
Switching between a first detection mode for detecting the interference light with a first wavelength resolution and a second detection mode for detecting the interference light with a second wavelength resolution higher than the first wavelength resolution. A detection mode control means ;
The light source unit is a light source capable of switching a wavelength fluctuation width per unit time when the wavelength is swept,
The detection mode control means controls the light source unit so that the wavelength fluctuation width per unit time when the wavelength is swept is smaller in the second detection mode than in the first detection mode. optical tomographic imaging apparatus, characterized in that it. A light source unit that emits light while sweeping the wavelength at a constant period;
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 to the measurement object;
Interference light detection means for detecting interference light between the reflected light and the reference light multiplexed by the multiplexing means;
In an optical tomographic imaging apparatus having tomographic information acquisition means for acquiring tomographic information of the measurement object by performing frequency analysis on the interference light detected by the interference light detection means,
Switching between a first detection mode for detecting the interference light with a first wavelength resolution and a second detection mode for detecting the interference light with a second wavelength resolution higher than the first wavelength resolution. A detection mode control means ;
The interference light detection means detects the interference light by sampling the interference light at a predetermined sampling frequency,
The detection mode control means controls the interference light detection means so that the sampling frequency when detecting the interference light is higher in the second detection mode than in the first detection mode. optical tomographic imaging apparatus, characterized in that there. The first detection mode is an image acquisition mode for acquiring a tomographic image of the measurement target, and the second detection mode is a measurement start position adjustment mode for adjusting a position at which a tomographic image signal is obtained in the depth direction of the measurement target. optical tomography system according to claim 1 or 2, wherein the at. The optical tomographic imaging apparatus according to any one of claims 1 to 3, further comprising an optical path length adjusting unit that adjusts an optical path length of the measurement light or the reference light.

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