JP2009244207A - Optical tomographic imaging apparatus and tomographic image acquiring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical tomographic imaging apparatus capable of measuring a measuring concerned region with high resolving power without relying on the position (depth) of the measuring concerned region in SS-OCT using a wavelength sweeping light source, and a tomographic image acquiring method. <P>SOLUTION: The optical tomographic imaging apparatus has a light path length adjusting part for setting a first reference position in a measuring depth direction to the inner edge part of a measuring range by adjusting the light path length of reference light and a light path length changing-over part having a light path length, which imparts a second reference position different in measuring depth with respect to the first reference position by predetermined quantity and becomes the outer edge part of the measuring range, preset thereto and altering the light path length of reference light or light path length of reflected light adjusted by the light path length adjusting part to change over the first reference position and the second reference position. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an OCT optical tomographic imaging apparatus and a tomographic image acquisition method using a wavelength swept light source.

As an apparatus for acquiring a cross-sectional image without cutting a measurement target such as a living tissue, there is an optical tomographic imaging apparatus using OCT (Optical Coherence Tomography) measurement.
This OCT measurement is a type of optical interferometry, in which the light emitted from the light source is divided into measurement light and reference light, and the optical path length of the measurement light and reference light is within the coherence length of the light source. This is a measurement method using the fact that optical interference is detected only when they match.

  As an optical tomographic imaging apparatus, a tomographic image is obtained by changing a measurement position (measurement depth) with respect to a measurement object by changing an optical path length of reference light, and by TD-OCT (Time Domain OCT), SD-OCT which obtains a tomographic image in the optical axis direction by Fourier-transforming the spectral interference waveform obtained by measuring the interference light intensity for each optical frequency component instead of changing the optical path length of the reference light (Spectral Domain OCT) and SS-OCT (Swept Source OCT) are known.

  In SS-OCT, the reference position (zero path position) where the optical path length of the signal light reflected from the object (measurement light) and the reference light matches so that the range to be measured falls within the coherence length of the light source, Once the zero-pass position is aligned, it is fixed at that position, the interference signal is detected, the detected interference signal is Fourier transformed, and the absolute value of each characteristic frequency is plotted. I have an image.

In particular, in the SS method and the TD method, the measurement range that can be acquired at a time is limited to the coherence length of the light source. Therefore, for example, in Patent Document 1, since the OCT apparatus used in the fundus examination apparatus has a short coherence length, the OCT lateral image only shows a fragment of the retina, which is compared with a conventional scanning laser ophthalmoscope (SLO). In the OCT using a light source having a very small coherence length in the range of 10 μm to 300 μm, the horizontal OCT image is obtained at different depths by changing the reference optical path stepwise. And an optical mapping apparatus that creates a horizontal image by processing the collected horizontal OCT image by software.
In this technique, an OCT image is acquired over a range that cannot be measured by one measurement by changing the reference optical path stepwise and collecting the OCT image in a plurality of times.

Special table 2003-516531 gazette

In the case of OCT (SS-OCT) using a light source having a sufficiently long coherence length, a measurement target can be captured by a single measurement.
However, even within the range that can be measured by a single measurement, due to the characteristics of low-coherence light, there is a problem that the interference intensity decreases as the distance from the zero-pass position decreases, and the image deteriorates. For example, in the case of a medical diagnostic image, the depth of the measurement region of interest varies depending on the diagnosis target region and its situation, but if the measurement region of interest is far from the zero-pass position, sufficient image quality may not be obtained.

  The object of the present invention is to solve the above-mentioned problems of the prior art and perform measurement regardless of the position (depth) of the region of interest in SS-OCT using a wavelength swept light source, which has a longer coherence length than SD-OCT. An object of the present invention is to provide an optical tomographic imaging apparatus and a tomographic image acquisition method capable of measuring a region of interest with high resolution.

In order to solve the above problems, the present invention provides a wavelength swept light source,
A branching unit for branching light emitted from the wavelength swept light source into measurement light and reference light;
While irradiating the measurement light from the branch part to the measurement object, and a measurement part for acquiring the reflected light from the measurement object, an optical probe including in an outer cylinder,
An optical path length adjustment unit that sets the first reference position in the measurement depth direction at the inner edge of the measurement range by adjusting the optical path length of the reference light;
The optical path length of the reference light adjusted by the optical path length adjustment unit is preset with an optical path length that provides a second reference position that is a predetermined amount different in measurement depth from the first reference position and serves as an outer edge of the measurement range. An optical path length switching unit that switches between the first reference position and the second reference position by changing the length or the optical path length of the reflected light;
A control unit for controlling the optical path length adjusting unit and the optical path length switching unit;
A multiplexing unit that is arranged downstream of the optical path length adjustment unit and the optical path length switching unit, and combines the reflected light acquired by the measurement unit and the reference light to generate interference light;
An interference light detection unit that detects the interference light generated by the multiplexing unit as an interference signal;
An optical tomographic imaging apparatus including a tomographic image acquisition processing unit that acquires a tomographic image from the interference signal detected by the interference light detection unit is provided.

  Here, the control unit switches the optical path length switching unit to the first reference position and the second reference position during measurement by the measurement unit, the tomographic image acquisition processing unit, for the same measurement object, It is preferable to acquire two tomographic images based on both the first reference position and the second reference position switched by the optical path length switching unit.

  In addition, the control unit switches the optical path length switching unit to the first reference position and the second reference position in synchronization with the rotational scanning period or the planar scanning period of the measuring unit during measurement by the measuring unit. The tomographic image acquisition processing unit includes the entire tomographic image based on the first reference position or the portion on the first reference position side, and the entire tomographic image based on the second reference position or on the second reference position side. It is preferable to obtain a composite tomographic image by combining the portions.

The optical path length switching unit preferably has a plurality of optical path lengths as the optical path length giving the second reference position.
Furthermore, it has a parameter memory | storage part which hold | maintains the parameter of the said 2nd reference position preset for every measurement site | part, The said control part is a said 2nd reference | standard from the said parameter memory | storage part according to the input measurement site | part information. It is preferable that the position parameter is read and the optical path length switching unit is switched according to the read parameter.

  Further, the parameter storage unit has a plurality of parameters for one measurement site information, and the control unit reads out the parameter of the second reference position according to the input instruction information, and reads out the parameter It is preferable to switch the optical path length switching unit according to the above.

  The tomographic image acquisition processing unit includes a detection unit that detects a distance between a tip of the optical probe and a measurement target, and the control unit includes a tip of the optical probe detected by the tomographic image acquisition processing unit. When the distance to the measurement target is greater than or equal to a predetermined distance, it is preferable to switch the optical path length switching unit to an optical path corresponding to the first reference position.

  In addition, the control unit, when the distance between the tip of the optical probe detected by the tomographic image acquisition processing unit and the measurement target is a predetermined distance or more, on the surface of the measurement target closest to the inner edge of the measurement range The optical path length switching unit or the optical path length adjusting unit is preferably adjusted so that the first reference position is matched.

  The optical probe includes a driving unit that rotates the measurement unit and an optical fiber that transmits the measurement light to the measurement unit and the reflected light from the measurement unit, and the tomographic image acquisition processing unit Is to obtain a circular two-dimensional tomographic image corresponding to the rotation of the measurement unit, and the adjustment amount of the first reference position, and the first reference position after adjustment and the first before adjustment. It is preferable to correct the tomographic image obtained based on the adjusted first reference position from the distance from the center of the tomographic image obtained for the reference position.

The optical path length switching unit preferably includes a plurality of optical paths having different lengths and switching means for switching the plurality of optical paths.
The optical path length switching unit preferably switches the optical path to a plurality of optical path lengths by moving the optical path length adjusting means of the optical path length adjusting unit.

The present invention also provides a tomographic image acquisition method in the optical tomographic imaging apparatus described above,
When one of the first reference position and the second reference position is selected according to the measurement region of interest, the optical path length switching unit is switched to the selected one of the reference positions,
Provided is a tomographic image acquisition method for acquiring a tomographic image based on the switched reference position.

The present invention also provides a tomographic image acquisition method in the optical tomographic imaging apparatus described above,
During the measurement by the measurement unit, the optical path length switching unit is switched to the first reference position and the second reference position,
Provided is a tomographic image acquisition method for acquiring two tomographic images based on both the first reference position and the second reference position for the same measurement object.

  In the above method, during the measurement by the measurement unit, the optical path length switching unit is switched to the first reference position and the second reference position in synchronization with the rotational scanning period or the planar scanning period of the measurement unit, It is preferable to obtain a combined tomographic image by synthesizing the portion on the first reference position side of the tomographic image based on the first reference position and the portion on the second reference position side of the tomographic image based on the second reference position. .

The present invention also provides a tomographic image acquisition method in the optical tomographic imaging apparatus described above,
Provided is a tomographic image acquisition method for reading the parameter of the second reference position from the parameter storage unit by inputting measurement site information and switching the optical path length switching unit according to the read parameter.

In the above method, the distance between the tip of the optical probe and the measurement object is detected,
When the detected distance between the tip of the optical probe and the measurement target is greater than or equal to a predetermined distance, it is preferable to automatically select the first reference position.

  Further, when the detected distance between the tip of the optical probe and the measurement target is equal to or greater than a predetermined distance, the optical path length is adjusted so that the first reference position is aligned with the surface of the measurement target closest to the inner edge of the measurement range. It is preferable to adjust the adjustment unit.

  Further, when obtaining a circular two-dimensional tomographic image corresponding to the rotation of the measurement unit, the adjustment amount of the first reference position, the adjusted first reference position, and the first reference position before adjustment. An image similar to the tomographic image obtained for the first reference position before adjustment by correcting the tomographic image obtained based on the adjusted first reference position from the distance from the center of the obtained tomographic image. Is preferably produced.

According to the present invention, in SS-OCT using a wavelength-swept light source, the measurement reference position (zero path position) can be switched between the inner side and the outer side of the measurable range. ), The measurement region of interest can be measured with high resolution.
In one embodiment of the present invention, a high-resolution image is obtained for the entire measurable range by synthesizing images obtained by switching and measuring the zero-pass position between the inside and outside of the measurable range. be able to.

  Further, in one aspect of the present invention, a zero-pass position parameter is prepared for each measurement site, and the operator can automatically set the zero-pass position simply by inputting information on the measurement site (measurement site information). Thus, the measurement can be switched immediately and the measurement speed can be increased and the convenience of the apparatus can be improved.

  Furthermore, in one aspect of the present invention, when it is detected that the probe of the measuring device is at a certain distance or more from the measurement target (sample), the zero-pass position is automatically switched to the inside of the measurable range, Since the zero-pass position is aligned with the surface of the measurement object closest to the probe, it is possible to increase the resolution near the surface in the display image so that the overall shape can be easily grasped, and the convenience of measurement can be improved.

  An optical tomographic imaging apparatus and a tomographic image acquisition method according to the present invention will be described below in detail based on preferred embodiments shown in the accompanying drawings.

  First, a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of an optical tomographic imaging apparatus of the present invention that implements a tomographic image acquisition method of the present invention. The optical tomographic imaging apparatus 10 shown in FIG. 1 uses a wavelength swept light source, scans the measurement object with the measurement light, obtains the reflected light, and based on the interference light between the reflected light and the reference light, the optical axis of the measurement light This is a so-called SS-OCT (Swept Source OCT) apparatus for obtaining a tomographic image of a direction.

  The optical tomographic imaging apparatus 10 splits the light emitted from the light source unit 12 that emits light into the measurement light and the reference light, and the reflected light and the reference light from the measurement target of the measurement light. Are coupled to each other to generate interference light, the measurement light is guided to irradiate the measurement object, the reflected light from the measurement object is received, and the optical path length of the reference light. An optical path length adjusting unit 18 that adjusts the optical path length of the reference light, an optical path length switching unit 34 that selectively switches the optical path length to a different optical path length, and an interference light that detects the interference light generated by the branching / combining unit 14 as an interference signal The detection unit 20, the processing unit 22 that processes the interference signal detected by the interference light detection unit 20, and the display unit that displays the optical tomographic image (hereinafter also simply referred to as “tomographic image”) acquired by the processing unit 22. 24, an optical path length adjusting unit 18 and an optical path length switching unit And a control unit 32 for controlling the entire optical tomographic imaging system 10, an operation unit 36 that accepts an instruction input such as changing input and set various conditions from the outside including 4.

  In addition, the optical tomographic imaging apparatus 10 includes a rotation drive unit 26 that rotates a measurement unit of an optical probe for rotational scanning of measurement light, an optical fiber coupler 28 that splits light emitted from the light source unit 12, and a light source. It has a detector 30a that detects light (laser light) light and a detector 30b that detects reflected light. Further, an optical fiber FB is used as a light path between the components, and light source light (laser light) La, measurement light L1, reference light L2, reflected light L3, and interference light L4 are guided to each part by this optical fiber. is doing. Hereinafter, each part will be described in detail.

  The light source unit 12 includes a semiconductor optical amplifier 40, an optical splitter 42, a collimator lens 44, a diffraction grating element 46, an optical system 48, and a rotary polygon mirror 50, and sweeps the frequency at a constant period. Laser beam La is emitted.

  The semiconductor optical amplifier (semiconductor gain medium) 40 emits weak emission light and amplifies incident light when a drive current is applied. In the semiconductor optical amplifier 40, both ends of the optical fiber FB10 are connected to form a loop. That is, one end of the optical fiber FB10 is connected to a portion where light is emitted from the semiconductor optical amplifier 40, and the other end of the optical fiber FB10 is connected to a portion where light is incident on the semiconductor optical amplifier 40. The light emitted from the semiconductor optical amplifier 40 is emitted to the optical fiber FB10 and enters the semiconductor optical amplifier 40 again. Thus, by forming a loop of the optical path with the semiconductor optical amplifier 40 and the optical fiber FB10, the semiconductor optical amplifier 40 and the optical fiber FB10 become an optical resonator, and a drive current is applied to the semiconductor optical amplifier 40. Pulsed laser light is generated.

  The optical splitter 42 is provided on the optical path of the optical fiber FB10 and is also connected to the optical fiber FB11. The optical branching device 42 branches a part of the light guided in the optical fiber FB10 to the optical fiber FB11. The collimator lens 44 is disposed in the vicinity of the other end of the optical fiber FB11, that is, the end not connected to the optical fiber FB10, and collimates the light emitted from the optical fiber FB11. The diffraction grating element 46 is disposed at a predetermined angle on the optical path of the parallel light generated by the collimator lens 44. The diffraction grating element 46 splits the parallel light emitted from the collimator lens 44.

  The optical system 48 is disposed on the optical path of the light split by the diffraction grating element 46. The optical system 48 is composed of a plurality of lenses, refracts the light split by the diffraction grating element 46, and converts the refracted light into parallel light. The rotating polygon mirror 50 is disposed on the optical path of the parallel light generated by the optical system 48 and reflects the parallel light. The rotary polygon mirror 50 is a rotating body that rotates at a constant speed in the R1 direction in FIG. The rotary polygon mirror 50 has a regular octagonal plane perpendicular to the rotation axis, and side surfaces (surfaces forming each side of the octagon) irradiated with parallel light are configured as reflecting surfaces that reflect the irradiated light. ing. The rotating polygon mirror 50 rotates to change the angle of each reflecting surface with respect to the optical axis of the optical system 48.

  The light emitted from the optical fiber FB11 passes through the collimator lens 44, the diffraction grating element 46, and the optical system 48, and is reflected by the rotary polygon mirror 50. The reflected light passes through the optical system 48, the diffraction grating element 46, and the collimator lens 44 and enters the optical fiber FB11.

  As described above, since the angle of the reflecting surface of the rotating polygon mirror 50 changes with respect to the optical axis of the optical system 48, the angle at which the rotating polygon mirror 50 reflects light changes with time. For this reason, only the light in a specific frequency region out of the light dispersed by the diffraction grating element 46 enters the optical fiber FB11 again. Here, since the light in a specific frequency range incident on the optical fiber FB11 is determined by the angle between the optical axis of the optical system 48 and the reflecting surface of the rotary polygon mirror 50, the frequency range of the light incident on the optical fiber FB11 is This is changed by a change in the angle between the optical axis of the optical system 48 and the reflecting surface of the rotary polygon mirror 50.

  The light in a specific frequency range that has entered the optical fiber FB11 is incident on the optical fiber FB10 from the optical splitter 42, and is combined with the light in the optical fiber FB10. Thereby, the pulsed laser light guided to the optical fiber FB10 becomes laser light in a specific frequency range, and the laser light La in the specific frequency range is emitted to the optical fiber FB1. Here, since the rotary polygon mirror 50 is rotating at a constant speed in the direction of the arrow R1, the wavelength λ of the light incident on the optical fiber FB11 again changes with a constant period as time passes. As a result, the frequency of the laser light La emitted to the optical fiber FB1 also changes at a constant period as time passes.

  The light source unit 12 has such a configuration, and emits the laser light La swept in wavelength toward the optical fiber FB1.

  Next, the branching / combining unit 14 is configured by, for example, a 2 × 2 optical fiber coupler, and is optically connected to the optical fiber FB1, the optical fiber FB2, the optical fiber FB3, and the optical fiber FB4, respectively.

  The branching / combining unit 14 divides the light La incident from the light source unit 12 through the optical fiber FB1 into the measurement light L1 and the reference light L2, causes the measurement light L1 to enter the optical fiber FB2, and the reference light L2 The light is incident on the fiber FB3. Further, the branching / combining unit 14 is incident on the optical fiber FB3, returns to the optical fiber FB3 via the optical path length switching unit 34 and the optical path length adjusting unit 18, and the reference light L2 incident on the branching / combining unit 14 again. The reflected light L3 from the measurement object S, which is acquired by the optical probe 16 based on the measurement light L1 incident on the optical fiber FB2 and returns to the branching multiplexing unit 14 after returning from the optical fiber FB2, is multiplexed. Injected into the optical fiber FB4.

  The optical probe 16 is an instrument that is inserted into a subject and measures the measurement target S. The optical probe 16 has a proximal end connected to the optical fiber FB2, guides the measurement light L1 incident from the optical fiber FB2 to the distal end, and irradiates the measurement target S at the measurement portion at the distal end. In addition, the reflected light L3 from the measuring object S is received. Further, the optical probe 16 is rotated at the measuring unit by the rotation driving unit 26 and rotationally scans the measuring light L <b> 1 around the axis of the optical probe 16.

  FIG. 2 shows an enlarged cross-sectional view of the distal end portion of the optical probe 16. As shown in FIG. 2, the optical probe 16 includes a probe outer cylinder (sheath) 52, a cap 54 that closes the tip of the probe outer cylinder 52, an optical fiber 56, a flexible shaft 58, and a fixing member (sleeve) 60. And an optical lens 62.

  The probe outer cylinder 52 is a cylindrical member having flexibility, and at least a portion through which the measurement light L1 and reflected light L3 pass is formed of a material that transmits light (transparent material). Yes.

  The optical fiber 56 is inserted into the probe outer cylinder 52, a base end portion thereof is connected to the optical fiber FB2, and a tip end thereof is connected to an optical lens 62 serving as a measurement portion. The optical fiber 56 guides the measurement light L1 emitted from the optical fiber FB2 to the optical lens 62, and receives the reflected light L3 from the measurement target S with respect to the measurement light L1 acquired by the optical lens 62 to the optical fiber FB2. Waveguide.

  The optical lens 62 is optically connected to the tip of the optical fiber 56. The optical lens 62 is a so-called hemispherical lens, and condenses the measurement light L1 emitted from the optical fiber 56 on the measurement object S. Further, the optical lens 62 collects the reflected light L3 of the measuring light L1 on the measuring object S and makes it incident on the optical fiber 56.

  A connecting portion between the tip of the optical fiber 56 and the optical lens 62 is held by a fixing member 60, and a flexible shaft 58 is attached to the fixing member 60. The flexible shaft 58 accommodates the optical fiber 56 in a hollow portion, and extends to the proximal end portion of the probe outer cylinder 52. A base end portion of the flexible shaft 58 is connected to the rotation drive unit 26. The rotation drive unit 26 rotates the flexible shaft 58 to rotate the optical fiber 56 and the optical lens 62 with respect to the probe outer cylinder 52, for example, in the direction of arrow R2 in FIG.

  The optical fiber 56 is supported so as to be rotatable with respect to the probe outer cylinder 52. The optical fiber 56 and the optical fiber FB2 are connected by a rotary joint or the like, and are optically connected in a state where the rotation of the optical fiber 56 is not transmitted to the optical fiber FB2.

  The rotation drive unit 26 includes a rotary encoder (not shown), detects the irradiation position of the measurement light L1 from the position information (angle information) of the optical lens 62 based on a signal from the rotary encoder, The position information is sent to the processing unit 22.

  The optical probe 16 is basically configured as described above. The optical fiber 56 and the flexible shaft 58 are rotated in the direction of the arrow R2 in FIG. The reflected light L3 is acquired by irradiating the measurement object S with scanning in the direction of arrow R1 (circumferential direction of the probe outer cylinder 52). Thereby, the reflected light L3 reflected from the measuring object S can be acquired over the entire circumference of the probe outer cylinder 52 in the circumferential direction.

  The optical path length adjustment unit 18 is a part that adjusts the optical path length of the reference light L2. The optical path length adjusting unit 18 is connected to the branching / combining unit 14 and is connected to an optical fiber FB3 that is a waveguide of the reference light L2 branched from the laser light La via an optical path length switching unit 32. The optical path length adjusting unit 18 and the optical path length switching unit 32 are connected by an optical fiber FB6.

  The optical path length adjustment unit 18 converts the reference light L2 emitted from the optical fiber FB6 into parallel light, and the second optical lens 66 that condenses the light converted into parallel light by the first optical lens 64. A reflecting mirror 68 that reflects the light collected by the second optical lens 66, a base 70 that fixedly supports the second optical lens 66 and the reflecting mirror 68, and the base 70 parallel to the optical axis direction. And a mirror moving mechanism 72 for moving in a proper direction.

  The optical path length adjustment unit 18 adjusts the optical path length of the reference light L2 by changing the distance between the first optical lens 64 and the second optical lens 66, and determines the reference position of the depth of the measurement target measured by the measurement light L1 ( Hereinafter, this is referred to as a zero path position).

  The first optical lens 64 converts the reference light L2 emitted from the core of the optical fiber FB6 into parallel light, and condenses the reference light L2 reflected by the reflection mirror 68 on the core of the optical fiber FB6. The second optical lens 66 condenses the reference light L2 made parallel by the first optical lens 64 on the reflection mirror 68, and makes the reference light L2 reflected by the reflection mirror 68 parallel. Thus, the first optical lens 64 and the second optical lens 66 form a confocal optical system. The reflection mirror 68 is disposed at the focal point of the light collected by the second optical lens 66 and reflects the reference light L <b> 2 collected by the second optical lens 66.

  The reference light L2 emitted from the optical fiber FB6 becomes parallel light by the first optical lens 64, and is condensed on the reflection mirror 68 by the second optical lens 66. Thereafter, the reference light L2 reflected by the reflection mirror 68 becomes parallel light by the second optical lens 66, and is condensed on the core of the optical fiber FB6 by the first optical lens 64.

  The mirror moving mechanism 72 moves the base 70 in the optical axis direction of the first optical lens 64 (in the direction of arrow A in FIG. 1). The mirror moving mechanism 72 is controlled by the control unit 32 and moves the base 70 in the optical axis direction, thereby changing the distance between the first optical lens 64 and the second optical lens 66, and the optical path of the reference light L2. Adjust the length.

  The optical path length switching unit 34 is a feature of the present invention, and is disposed between the branching / combining unit 14 and the optical path length adjusting unit 18. The branching / combining unit 14 and the optical path length switching unit 34 are connected by an optical fiber FB3, and the optical path length switching unit 34 and the optical path length adjusting unit 18 are connected by an optical fiber FB6.

  The optical path length switching unit 34 has a configuration capable of switching between two preset optical path lengths, and selectively switches the optical path length under the control of the control unit 32. The difference between the two types of optical path lengths is set to be approximately equal to the difference between the maximum value and the minimum value of the depth of the measurable range in the optical tomographic imaging apparatus 10. Therefore, after the zero path position (reference position of the measurement range in the depth direction) is set by the optical path length adjustment unit 18 for one optical path length of the optical path length switching unit 34, the optical path length is switched by the optical path length switching unit 34. Then, the zero-pass position is switched to the opposite edge of the measurable range.

  When the optical path length is switched, the optical path length switching unit 34 sends the selected optical path, that is, information on the optical path length connected to the preceding and succeeding optical fibers FB3 and FB6, to the control unit 32 as zero path information.

  The specific configuration of the optical path length switching unit 34 is not particularly limited as long as it can be switched to a predetermined optical path length. As the optical path length switching unit 34, the following configuration can be exemplified.

  For example, the optical path length switching unit 34 can be configured by a plurality of optical fibers having different lengths and an optical switch that switches the optical fibers. That is, as shown in FIG. 3A, the optical path length switching unit 34 is configured to change the optical path for emitting the two optical fibers FB100 and FB102 having different optical path lengths and the reference light L2 emitted from the optical fiber FB3. The optical switch SW1 that switches to one of the optical fibers FB100 and FB102 and the optical switch SW2 that switches the optical fiber FB100 and the optical fiber FB102 in conjunction with the optical switch SW1 are configured, and the optical switch SW1 and the optical switch SW2 are switched. Thus, the optical path length of the reference light L2 is instantaneously switched.

  Thus, the optical path length of the reference light L2 is changed between the first optical path that passes through the optical fiber FB100 by the optical switches SW1 and SW2 and the second optical path that switches the optical switches SW1 and SW2 and passes through the optical fiber FB102. It is changed by the amount of the optical path difference between the optical fiber FB100 and the optical fiber FB102.

  As another example, the optical path length switching unit 34 can be configured using an optical switch capable of selecting a plurality of spatial distances. For example, as shown in FIG. 3 (B), the optical path length switching unit 34 includes optical switches SW1 and SW2 that switch between the spaces L1 and L2 and the spaces L1 and L2 in which the positions of the reflection mirrors MR1 and MR2 are different and the optical path lengths are different. It is good also as a structure which has.

  Further, the optical path length switching unit 34 may be configured to switch the space length in a non-contact manner. That is, as shown in FIG. 3C, by using the swing angle control of the fixed mirror MR3 and the MEMS mirror or galvanometer mirror MR4, the MEMS mirror or galvanometer mirror MR3 is swung to a preset angle R3, and the space L3 By switching L4 and switching the space length, the optical path length can be switched without contact.

  Alternatively, the optical path length switching unit 34 may be configured to switch the optical path length by high-speed driving of the reflection mirror. For example, the optical path length switching unit 34 is also used as the optical path length adjusting unit 18, or a delay device using the mirror moving mechanism 72 is provided by separately providing the same configuration as the optical path length adjusting unit 18 as the optical path length switching unit 34. The optical path length can be switched by operating at high speed.

  The interference light detection unit 20 detects the interference light L4 generated by combining the reference light L2 and the reflected light L3 in the branching multiplexing unit 14 as an interference signal. The interference light detection unit 20 is connected to the branching / combining unit 14 by an optical fiber FB4. At the entrance side of the interference light detection unit 20, a detector 30 a that detects the light intensity of the laser light La branched from the optical fiber FB 1 to the optical fiber FB 5 by the optical fiber coupler 28, and the interference light L 4 from the branching multiplexing unit 14. The detector 30b that detects the light intensity of the detector 30b is connected, and the detection results of the detector 30a and the detector 30b are sent to the interference light detector 20. The interference light detection unit 20 adjusts the balance of the light intensity of the interference light L4 based on the detection results of the detectors 30a and 30b.

  The processing unit 22 acquires a tomographic image from the interference signal detected by the interference light detection unit 20. FIG. 4 shows a schematic configuration of the processing unit 22. As illustrated in FIG. 4, the processing unit 22 includes an interference signal acquisition unit 80, an A / D conversion unit 82, a tomographic information generation unit 86, and an image correction unit 88.

  The interference signal acquisition unit 80 acquires the interference signal detected by the interference light detection unit 20, and further, the position information of the measurement position detected by the rotation drive mechanism 26, specifically, the optical lens 62 in the rotation direction. Information on the irradiation position of the measurement light L1 detected from the position information is acquired, and the interference signal is associated with the position information on the measurement position.

The correlation between the interference signal and the position information of the measurement position can be performed as follows.
First, the number of measurements per rotation of the optical lens 62 is determined from the rotation speed of the optical lens 62 and the cycle for sweeping the frequency of the measurement light L1. Assuming that the rotation of the optical lens 62 and the number of acquisitions of interference signals, that is, the cycle of the measurement light L1 are constant, the measurement position by the measurement light L1 moves by a predetermined angle around the rotation axis of the optical lens 62. Go.

  Since the position where the interference signal is acquired moves by a predetermined angle, the line number n can be associated with the measurement position of each interference signal. For example, assuming that the interference signal is acquired 1024 times during one rotation of the optical lens 62, line numbers of n = 1 to 1024 can be assigned as interference signal acquisition positions (measurement positions). Since the optical lens 62 is rotating, the measurement position n = 1024 and the measurement position n = 1 are adjacent to each other. The interference signal associated with the position information of the measurement position is sent to the A / D conversion means 82.

  The A / D conversion unit 82 converts the interference signal output as an analog signal associated with the position information of the measurement position by the interference signal acquisition unit 80 into a digital signal. The digitally converted interference signal is sent to the tomographic information generation means 86.

  The tomographic information generation unit 86 performs FFT (Fast Fourier Transform) processing on the interference signal converted into a digital signal by the A / D conversion unit 82, acquires information on the relationship between the frequency component and the intensity, and acquires the acquired information. To obtain a tomographic image in the depth direction.

  Here, the tomographic information generation means 86 uses the interference signal and the zero path position information sent from the control unit 32 so that the set zero path position is closer to the measurement range than the optical probe 16 (measurement depth). Whether it is the shallower side or the inner side) or the deeper side (the deeper measurement depth side or the outer side), and a tomographic image in the depth direction is generated according to the determination result. If the zero-pass position is on the near side, the result in the direction toward the far side after FFT processing is used. If the zero-pass position is on the far side, the optical probe 16 on the near side from the zero-pass position on the far side after FFT processing is used. By using the result of the direction toward the center, a tomographic image can be generated from an appropriate interference signal acquired within the measurement range.

  The generation of an image in the tomographic information generation means 86 can be performed using a technique described in “Mitsuo Takeda,“ Optical Frequency Scanning Spectrum Interference Microscope ”, Optical Technology Contact, 2003, Vol41, No7, p426-p432”. The following is a brief description.

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. Is S (l), the light intensity I (k) of the interference signal detected by the interference light detector 20 is
I (k) = ∫ ₀ ^∞ S (l) [1 + cos (kl)] dl
It is represented by Here, k is the wave number, and l is the optical path length difference. It can be considered that the above equation is given as an interferogram in the optical frequency domain with the wave number k = ω / c as a variable. For this reason, the tomographic information generation means 86 performs the fast Fourier transform on the spectral interference fringes detected by the interference light detection unit 20, and determines the light intensity S (l) of the interference light L4, thereby starting the measurement of the measurement object S. The distance information from the position and the reflection intensity information can be acquired and a tomographic image can be generated.

  The image correcting unit 88 performs logarithmic transformation and radial transformation on the tomographic image generated by the tomographic image generating unit 86, arranges them in the order of line numbers, and forms a circular image centered on the rotation center of the optical lens. Further, the image correcting unit 88 corrects the image quality by performing a sharpening process, a smoothing process, or the like on the tomographic image. The image correcting unit 88 transmits the tomographic image subjected to the image quality correction to the display unit 24.

  The transmission timing of the tomographic image from the image correction unit 88 to the display unit 24 is not particularly limited, and is transmitted to the display unit 24 every time one line processing is completed, and the display unit 24 rewrites and displays each line. Alternatively, the processing of all lines, that is, the processing of all images acquired by rotating the optical lens 62 once, is completed, and it may be transmitted to the display unit 24 when one circular tomographic image is formed. Good.

  The display unit 24 is a display device such as a CRT or LCD, and displays the tomographic image transmitted from the image correction unit 88. The operation unit 36 includes normal input means such as a keyboard and a mouse. Further, an operation screen may be displayed on the display unit 24 so as to function as the operation unit 36.

  The control unit 32 controls each unit of the optical tomographic imaging apparatus 10 including the optical path length adjusting unit 18 and the optical path length switching unit 34. A processing unit 22, a display unit 24, and an operation unit 36 are connected to the control unit 32. For example, the control unit 32 controls operations of the optical path length switching unit 34 and the optical path length adjusting unit 18 based on an operator instruction input from the input unit of the operation unit 36. The control unit 32 also inputs processing conditions in the processing unit 22, changes display settings on the display unit 24, and the like.

  Further, the control unit 32 receives the zero-path position information sent from the optical path length switching unit 34 and supplies the zero-path position information to the tomographic information generation means 86 of the processing unit 22.

Next, the operation of the optical tomographic imaging apparatus 10 will be described.
In the optical tomographic imaging apparatus 10, first, the zero pass position is initially set prior to measurement. The setting of the zero path position is performed by the control unit 32 controlling the optical path length adjustment unit 18. The control unit 32 drives the mirror moving mechanism 72 to move the base 70 in the direction of arrow A, so that the measurement target S is located in the measurable region and the zero path position is the front side of the measurement target S. The zero path position is set by adjusting the optical path length to be (inside).

  At the initial setting of the zero path, the optical path length switching unit 34 keeps the shorter optical path length (referred to as the first optical path length) selected. This first optical path length corresponds to a zero path position (referred to as a first zero path position) set on the near side of the measuring object S. The optical path length switching unit 34 sends information indicating that the first optical path length is selected, that is, that the first zero path position on the near side is set, to the control unit 32 as zero path position information.

  After setting the first zero-pass position, the optical probe 16 is inserted into the subject and measurement is started. First, the laser light La is emitted from the light source unit 12. The emitted laser light La is split into measurement light L1 and reference light L2 by the branching / combining unit 14. The measurement light L1 is guided to the optical probe 16 and irradiated to the measurement object S. Light obtained by reflecting the measurement light L1 at each depth position of the measurement object S enters the optical probe 16 as reflected light L3. The reflected light L3 is sent to the branching / combining unit 14.

  On the other hand, the reference light L <b> 2 enters the optical path length adjusting unit 18 via the optical path length switching unit 34. Then, the reference light L <b> 2 whose optical path length is adjusted by the optical path length adjusting unit 18 is incident on the branching / multiplexing unit 14 again via the optical path length switching unit 34. In the branching / combining unit 14, the reflected light L3 from the measurement target S and the reference light L2 whose optical path length is adjusted by the optical path length adjusting unit 18 are combined, and interference light between the reflected light L3 and the reference light L2 L4 is generated. The interference light is sent to the interference light detection unit 20 and detected as an interference signal.

  The interference signal detected by the interference light detection unit 20 is sent to the processing unit 22, and the processing unit 22 performs a process for creating a tomographic image. The processing unit 22 first acquires an interference signal of line number n (n is an arbitrary number) by the interference signal acquisition unit 80, and the analog signal acquired by the interference signal acquisition unit 80 by the A / D conversion unit 82. Convert interference signals into digital signals. Next, the tomographic information generation means 86 performs FFT processing on the A / D converted interference signal, and acquires a tomographic image of line number n from the result of the FFT processing.

  At this time, zero path position information is sent from the control unit 32 to the tomographic information generation means 86, and the result after the FFT processing inside or outside the zero path position is used according to the zero path position information. Here, since the zero-pass position is set inside the measuring object S, the result of the direction toward the outside after the FFT processing is used. Thereby, the range of a fixed distance from the zero path position to the outside becomes the measurable range.

  The tomographic image acquired in this way is sent to the image quality correction means 88 and subjected to image processing for display such as radial processing and sharpening processing. Then, it is sent to the display unit 24 and displayed.

  A schematic diagram of the tomographic image acquired in this way is shown in FIG. In FIG. 5A, the optical probe 16 is projected at the center of the image. A circle indicated by reference numeral 112 is the inner surface of the probe outer cylinder (sheath) 52 of the optical probe 16, and a circle indicated by reference numeral 114 is the outer surface of the probe outer cylinder 52. Also, the zero path 110 is set at a position that substantially matches the inner surface 112 of the probe outer cylinder 52. Therefore, the zero path 110 is set on the near side (inside) of the measuring object S.

  In the SS-OCT apparatus using the wavelength swept light source, for example, the measurable range is from zero path to 10 mm. However, according to the knowledge of the present inventor, even within this measurable range, a uniform high resolution image is not obtained in the entire range, and the closer to the zero path position, the higher the resolution image. Thus, the farther from the zero-pass position, the lower the resolution of the image. This was considered due to the characteristic of low coherence light that the closer to the zero-path position, the stronger the interference signal (the higher the interference intensity), and the farther from the zero-path position, the weaker the interference signal (the interference intensity becomes smaller).

  In the example of FIG. 5A, since the zero path 110 is set near the inner surface 112 of the probe outer cylinder 52, the object 116 located on the near side (inside) of the measurement range, that is, in a region near the distance from the zero path 110. For, a high-resolution tomographic image can be acquired. On the other hand, the object 118 in the back side (outside) region of the measurement range is far from the zero path 110, so that the interference signal becomes weak and a low-resolution tomographic image is obtained.

  Therefore, when the region of the object 116 on the near side of the measurement range is a region of interest, FIG. 5A obtained by setting the zero path 110 to the inner edge of the measurement range is an effective image. . On the other hand, when the region of the target 118 on the far side of the measurement range is a region of interest, the optical path length switching unit 34 is switched to obtain a zero path position in order to obtain a high resolution image for the region of interest. Switch outside the measuring range.

  The optical path length switching unit 34 can be switched during measurement. When the operator observes the tomographic image displayed on the display unit 24 and determines that a sufficient tomographic image is not obtained because the region of interest is far from the zero-pass position, the operator switches the zero-pass position from the operation unit 36. Enter instructions.

  The instruction input from the operation unit 36 is sent to the control unit 32, and the control unit 32 controls to switch the optical path length switching unit 34. Thereby, the optical path length switching unit 34 switches the connection to a different optical path length, here, the longer optical path length (referred to as a second optical path length). This second optical path length corresponds to the edge on the far side of the measurable range that is a predetermined distance away from the first zero-pass position set on the near side in the initial setting, and the optical path length switching unit 34 has the second optical path length. Is switched to the second zero-pass position at the edge on the far side of the measurable range.

  In addition, the control unit 32 switches the optical path length switching unit 34 and also indicates information indicating that the optical path length switching unit 34 has been switched to the second optical path length, that is, information indicating that the back side second zero path position is set. Information is sent to the tomographic information generation means 86 of the processing unit 22.

  After switching the optical path length switching unit 34, a tomographic image is acquired by the same method as described above. At this time, the tomographic information generation means 86 of the processing unit 22 performs post-FFT processing in the direction from the zero path position to the inside in accordance with the zero path position information from the control unit 32, that is, the information that the zero path is set to the outside. The result of is used. As a result, a tomographic image within a certain distance inward from the zero-pass position is acquired.

  A schematic diagram of the tomographic image acquired in this way is shown in FIG. In FIG. 5B, since the zero path 110 is set near the edge on the back side (outer side) of the measurement range, the area outside the center of the measurement range is closer to the distance from the zero path 110 and has a higher resolution. An image tomographic image can be acquired. Therefore, the object 118 in the area outside the measurement range is displayed with high resolution.

  Here, when the zero path 110 is set outside the measurement range, the interference light needs to reach a depth of the measurement target and the interference light attenuates, but the S / N ratio increases because the distance from the zero path position is short, A high-resolution tomographic image can be acquired.

  On the other hand, in the region on the front side (inside) of the center of the measurement range, the interference signal is weak because the distance from the zero path 110 is long, resulting in a low-resolution tomographic image. Therefore, the object 116 in the area inside the measurement range is displayed with a low resolution.

  Thus, according to the optical tomographic imaging apparatus 10 of the present invention, even during measurement, the zero-pass position is switched between the front side (inside) and the back side (outside) of the measurement range. Among them, the region in the depth direction where a high-resolution tomographic image can be acquired can be easily switched, and the region of interest can be acquired as a high-resolution image.

  In the above, the initial position of the zero-pass position is set to the front side (inside) of the measurement range and arbitrarily switched to a position on the back side of the measurement range. However, the initial position of the zero-pass position is set to the back side of the measurement range. (Outside) may be set.

  Next, a second embodiment of the present invention will be described. FIG. 6 is a block diagram schematically showing a schematic configuration of the second embodiment of the optical tomographic imaging apparatus of the present invention. The optical tomographic imaging apparatus 100 shown in FIG. 6 is obtained by adding a parameter storage unit 38 to the optical tomographic imaging apparatus 10 of FIG. 1 and other configurations are basically the same as those of the optical tomographic imaging apparatus 10. Therefore, the same code | symbol is attached | subjected to the same component and the detailed description is abbreviate | omitted. Hereinafter, the difference between the optical tomographic imaging apparatus 100 and the optical tomographic imaging apparatus 10 will be mainly described.

  The optical tomographic imaging apparatus 100 is provided with a parameter storage unit 38 connected to the control unit 32. The parameter storage unit 38 stores a zero-pass position parameter corresponding to the measurement site and the region of interest.

  When the optical tomographic imaging apparatus 100 is a medical apparatus, when the part (measurement target S) measured by the optical probe 16 is different, such as whether it is the esophagus or the stomach, the surface of the main region of interest The depth from is different. Even in the same measurement site, the depth of the region of interest varies depending on the purpose and symptoms.

  As described above, in an OCT apparatus that acquires tomographic image information using coherence light, a higher resolution image can be obtained as the position is closer to the zero-pass position, and the image is degraded as the distance from the zero-pass position is increased. Therefore, the preferred value of the zero-pass position for obtaining a high-resolution image for the region of interest will differ depending on the respective measurement site and region of interest.

  Normally, the zero-pass position (first zero-pass position) on the front side of the measurement range is a highly reliable position set as the initial position of the inner surface of the probe outer cylinder 52 of the optical probe 16, so that it is determined for each measurement site. The zero-pass position to be switched to is preferably the second zero-pass position on the back side (outside) of the measurement range.

  As described above, in the optical tomographic imaging apparatus 100, the position parameter of the second zero-pass position is set in advance and stored in the parameter storage unit 38 corresponding to each measurement site. Further, preferably, for each measurement site, a zero path position parameter corresponding to the depth range of the region of interest is stored in the parameter storage unit 38.

  Further, the optical path length switching unit 34 prepares a plurality of optical paths having optical path lengths corresponding to the zero path position parameter, and enables switching according to the parameters. Alternatively, the optical path length switching unit 34 is configured to be able to arbitrarily switch the optical path length according to the zero path position parameter.

  When the optical path length switching unit 34 can arbitrarily change the optical path length, the parameters stored in the parameter storage unit 38 may be freely set by the operator. In addition, the switching position of the second zero-pass position is simply prepared in stages, and the parameter corresponding to each position is stored in the parameter storage unit 38, and the operator selects the depth range of the region of interest, The second zero pass position may be switched.

  With reference to FIG. 7, a method of setting the second zero-pass position in the optical tomographic imaging apparatus 100 will be described. When an instruction is input from the operation unit 36 by the operator at the start of measurement or during measurement, the control unit 32 acquires the input measurement site information or the depth information of the region of interest (step S11), and acquires the acquired measurement. Based on the part information, a parameter corresponding to the measurement part information is selected and read from the parameter storage unit 38 (step S12).

  Next, the control part 32 switches the optical path length switching part 34 according to the parameter read from the parameter memory | storage part 38, and switches the optical path length of the reference light L2 (step S13). The zero path position is switched by switching the optical path length of the reference light L2.

  In addition, the control unit 32 switches the optical path length switching unit 34 in step S <b> 13 and supplies the zero path position information corresponding to the parameter read from the parameter storage unit 38 to the processing unit 22. The processing unit generates the tomographic information of an appropriate region by processing the interference signal corresponding to the zero-path position information supplied from the processing unit 22 in the generation of the tomographic image by the tomographic information generation unit 86.

  In this way, by holding parameters according to the measurement site and the region of interest, the zero-pass position can be easily switched according to the measurement site and the region of interest. Further, even when the measurement site and the region of interest are changed during measurement, the zero-pass position can be easily switched, the measurement can be speeded up, and the convenience of the optical tomographic imaging apparatus is further improved. be able to.

Next, a third embodiment of the present invention will be described.
In the first embodiment and the second embodiment described above, the tomographic image acquired by setting the zero path position on the near side (inside) and the zero path position on the back side (outside) are acquired according to the region of interest. Obtained tomographic images. Then, as described with reference to FIGS. 5 (A) and 5 (B), the image thus obtained has high resolution in the region close to the zero-pass position, and more than that in the region far from the zero-pass position. The image was low resolution.

  On the other hand, in the present embodiment, the tomographic image acquired by setting the zero path position on the near side (inside) and the tomographic image acquired by setting the zero path position on the back side (outside) are combined, and as a whole Acquire high-resolution tomographic images.

  FIG. 8 is a block diagram showing a schematic configuration of the processing unit 22A in the optical tomographic imaging apparatus of the present embodiment. The processing unit 22A shown in FIG. 8 is different from the processing unit 22 (see FIG. 4) in the above-described example in that an image composition unit 87 is provided between the tomographic information generation unit 86 and the image quality correction unit 88. ing. In this embodiment, the configuration other than the processing unit 22A is the same as that of the optical tomographic imaging apparatus 10 of the first embodiment or the optical tomographic imaging apparatus 100 of the second embodiment. Hereinafter, the present embodiment will be described with reference to the optical tomographic imaging apparatus 10 of FIG.

  In the present embodiment, in the optical tomographic imaging apparatus 10, first, the zero path position is initially set by the optical path length adjustment unit 18 in a state where the optical path length switching unit 34 is switched to the first optical path length. Thereby, as an initial set value, the first zero-pass position is set on the inner surface of the probe outer cylinder 52 of the optical probe 16, and this position is the innermost side of the measurement range. Next, in response to an instruction input from the operation unit 36, the control unit 32 switches the optical path length switching unit 34 to the second optical path length and switches to the second zero path position.

  The control unit 32 rotates the optical lens 62 (see FIG. 2) of the optical probe 16 by the rotation drive mechanism 26, and synchronizes with the rotation scanning period, and sets the zero path position to the inside of the measurement range by the optical path length switching unit 34. The measurement object S is measured while switching to the outside. For example, every time the optical lens 62 rotates, a first zero-pass position inside the measurement range and a second zero-pass position outside are switched.

  When the optical tomographic imaging apparatus 10 is an apparatus that performs planar scanning with the measurement light L1, the measurement may be performed by switching the zero-pass position in synchronization with the planar scanning period of the optical lens.

  The processing unit 22A receives the interference signal detected from the interference light L4 based on the reflected light L3 obtained by the optical probe 16, and associates the interference signal with the position information of the measurement position in the interference signal acquisition unit 80. The interference signal associated with the position information of the measurement position is converted into a digital signal by the A / D converter 82 and sent to the tomographic information generator 86.

  The tomographic information generation means 86 separates the interference signal acquired at the first zero path position and the interference signal acquired at the second zero path position based on the information at the time of switching the zero path in the optical path length switching unit 34, respectively. The interference signal selected based on the corresponding zero path position information is subjected to FFT processing to obtain two tomographic images. That is, for the interference signal acquired at the first zero-pass position, tomographic image information is generated using the result in the direction toward the far side after the FFT processing, and for the interference signal acquired at the second zero-pass position, The tomographic image information is generated using the result in the direction toward the front side after processing. As a result, for the same measurement object S, two images are acquired: a tomographic image with a high resolution on the front side (inside) of the measurement range and a tomographic image with a high resolution on the back side (outside) of the measurement range. be able to.

  Next, the image synthesizing unit 87 synthesizes the two tomographic images obtained by the tomographic information generating unit 86 to generate one synthesized image. Since the two tomographic images have slightly different acquisition times, it is considered that there is some variation between the two images. For this reason, it is preferable to perform image composition by correcting the variation and the like by matching the scales of both images. Both images are, for example, an image at the first zero-pass position and an image at the second zero-pass position, respectively, and the distance between the outer surface of the probe outer cylinder 52 and the same position on the surface of the measuring object S is calculated, The scale can be matched by making it correspond.

  For example, as shown in FIG. 9, the image composition method by the image composition means 87 is a high-resolution image from the zero-pass position to half of the measurement range, that is, the inner half of the image, of the images obtained at the first zero-pass position. The image tomographic image 122 and the high-resolution tomographic image 124 of the image obtained at the second zero-pass position from the zero-pass position to half of the measurement range, that is, the outer half of the image, A method for obtaining a tomographic image having a high resolution as a whole by combining them at 117 is mentioned.

  It is preferable that the width of the image adoption area in each image can be arbitrarily changed between the zero-pass position of the image and the edge on the opposite side of the measurement range. For example, the width of the adoption area of each image may be set and changed by input from the operation unit 36. Thereby, the image adoption area can be set to an arbitrary ratio such as 50% (half) in the radial direction, 70% inside, 30% outside, or the like.

  The boundary area of the image adoption area may have a width, and both images in the boundary area may be weighted and connected. Further, for one or both of the two images, the entire measurement range may be used as an image adoption area, that is, the entire acquired image may be used for weighting and synthesis. These conditions may be set arbitrarily or selectively from the operation unit 36.

  The tomographic image synthesized by the image synthesizing unit 87 is subjected to image correction by the image quality correcting unit 88 and displayed on the display unit 24.

  According to the third embodiment, the zero-pass position is switched between the front side (inside) and the back side (outside) to acquire two tomographic images, and the high-resolution part of each tomographic image is synthesized. Thus, since one tomographic image having a high resolution as a whole can be acquired and displayed on the display unit 24, both the object 116 and the object 118, which are regions of interest having different depths, are directly subjected to high resolution on the spot. A tomographic image can be confirmed.

Next, a fourth embodiment of the present invention will be described.
In the present embodiment, in the optical tomographic imaging apparatus of the present invention capable of switching the zero path position to the inside and the outside of the measurement region, when the optical probe 16 is away from the measurement target S, the first first zero path on the inside automatically. Switch to the position so that the vicinity of the surface of the measuring object S can be seen well.

  FIG. 10 is a block diagram showing a schematic configuration of the processing unit 22B in the optical tomographic imaging apparatus of the present embodiment. The processing unit 22B shown in FIG. 10 has a contact information acquisition unit 84 downstream of the A / D conversion unit 82, and the processing unit 22 in the first and second embodiments described above (FIG. 4). See). In this embodiment, the configuration other than the processing unit 22B is the same as that of the optical tomographic imaging apparatus 10 of the first embodiment or the optical tomographic imaging apparatus 100 of the second embodiment.

  The contact information acquisition unit 84 detects the positional relationship between the optical probe 16 and the measurement target S, that is, their distance, and acquires information (contact information) as to whether or not the optical probe 16 is in contact with the measurement target S. The contact information is output to the control unit 32.

  When receiving the contact information from the contact information acquisition unit 84, the control unit 32 controls the optical path length switching unit 34 according to the information. That is, when the optical probe 16 is away from the measurement target S, the control unit 32 sets the optical path length switching unit 34 to automatically switch the zero path position to the first zero path position at the inner edge of the measurement range. Control. As described above, the first zero-pass position is set on the inner surface of the probe outer cylinder 52 of the optical probe 16.

  Thus, when the optical probe 16 is separated from the measurement target S by a certain distance or more, the resolution of the surface of the measurement target S can be increased by switching the zero-pass position to the first zero-pass position. Thereby, it becomes easy to grasp the overall shape of the measuring object S, and the convenience of measurement can be improved.

Below, the contact information acquisition method in the contact information acquisition means 84 is demonstrated.
The contact information acquisition means 84 uses the interference signal converted into a digital signal by the A / D conversion means 82, and the position of the outer surface of the probe outer cylinder 52 at the position where the measurement light L1 of the optical probe 16 is transmitted, and the probe The position of the surface of the measuring object S closest to the outer cylinder 52 is detected, and the contact state between the probe outer cylinder 52 and the measuring object S is detected from these distances.

The position of the outer surface of the probe outer cylinder 52 is detected as follows.
First, in the information on the relationship between the frequency component and the interference intensity obtained by performing the FFT process on the interference signal for an arbitrary line, the frequency component is replaced with information in the depth direction (the direction away from the rotation center). Thus, information on the relationship between the depth direction and the strength is acquired.

  FIG. 12 is a graph showing an example of a calculation result (relationship between position in the depth direction and interference intensity) obtained by performing FFT processing on an interference signal. In FIG. 12, the horizontal axis represents the depth direction, and the vertical axis represents the strength. In FIG. 12, the depth at which the intensity peak is detected indicates the position where the physical properties have changed.

  In the optical tomographic imaging apparatus 10, the first reflected position of the measurement light L1 emitted from the optical lens 62 of the optical probe 16 is the probe outer cylinder 52. Therefore, the first peak position P1 in FIG. The position of the outer surface of the probe outer cylinder 52 is indicated. Here, in the optical probe 16, the optical lens 62 and the probe outer cylinder 52 are arranged coaxially. Accordingly, since the distance between the optical axis of the optical lens 62 and the outer peripheral surface of the probe outer cylinder 52 is constant regardless of the measurement position, the position of the outer peripheral surface of the probe outer cylinder 52 detected by one line is fully measured. Can be used for position.

  FIG. 12 shows the result of the interference signal when the measurement target S is measured. Usually, the measurement of the position of the outer surface of the probe outer cylinder 52 uses the interference signal when the measurement target S is not measured. Use. In that case, in FIG. 12, a peak at a position deeper than the peak P1 does not appear.

Next, detection of the contact state between the probe outer cylinder 52 and the measuring object S will be described.
First, similarly to the detection of the position of the outer peripheral surface of the probe outer cylinder 52 described above, FFT processing is performed on the interference signal for one line, and information on the depth direction and the interference intensity is acquired. Thereby, a graph as shown in FIG. 12 is obtained.

  In FIG. 12, a plurality of peaks are detected in the depth direction. Among the plurality of peaks, the first peak P1 indicates the outer peripheral surface of the probe outer cylinder 52, and the peak P2 next to the peak P1 indicates the surface of the measurement target S.

  Based on this result, the contact information acquisition means 84 detects the distance between the outer surface of the probe outer cylinder 52 and the surface of the measuring object S, and determines the contact state between the probe outer cylinder 52 and the measuring object S from the detected distance. To detect. That is, when the distance between the probe outer cylinder 52 and the measurement target S is equal to or smaller than the threshold value, the contact information acquisition unit 84 determines that the probe outer cylinder 52 and the measurement target S are in a contact state, and the detected distance is the threshold value. When larger, it determines with the probe outer cylinder 52 and the measuring object S being a non-contact state.

  The contact state between the probe outer cylinder 52 and the measuring object S is similarly determined for the adjacent line. Such determination is performed for each line on the entire measurement region, that is, the entire circumference of the probe outer cylinder 52. Next, the contact information acquisition unit 84 detects the presence / absence of a contact region between the probe outer cylinder 52 and the measurement target S based on the determination result of the contact state between the measurement target S and the outer periphery of the probe. The result is output to the control unit 32 as contact information.

Next, another example of the fourth embodiment of the present invention will be described.
In the above example, the zero-pass position is switched to the near side (inside), but the control unit 32 sets the zero-pass position to the surface of the closest measurement target S based on the contact information from the contact information acquisition unit 84. The optical path length switching unit 34 may be adjusted to match. In this case, as the contact information, in addition to the information on the presence / absence of the contact region between the probe outer cylinder 52 and the measurement target S, the information on the position (depth) of the measurement target S is also sent from the contact information acquisition means 84 to the control unit 32. Output. Further, the optical path length switching unit 34 is configured to be able to set the first zero path position to an arbitrary position.

  When it is detected that the probe outer cylinder 52 and the measuring object S are in a non-contact state, the zero path position is adjusted to the position of the peak P2 of the line where the distance between the probe outer cylinder 52 and the measuring object S is the closest, The vicinity of the surface of the measuring object S can be measured with higher resolution.

  In this case, the contact information acquisition means 84 of the processing unit 22 measures the measurement target at the line number where the distance between the probe outer cylinder 52 and the measurement target S is the closest in the entire measurement region (the entire circumference of the optical probe 16). Information on the position of the surface of S, that is, the position of the peak P2, is output to the control unit 32 as contact information.

  The control unit 32 calculates the movement amount of the zero path position from the current zero path position (first zero path position) set on the inner peripheral surface of the probe outer cylinder 52 based on the received position information of the peak P2. Based on the result, the optical path length of the optical path length switching unit 34 is switched. In this way, after setting the zero-pass position as the surface of the measuring object S, the optical probe 16 is rotationally scanned to acquire an interference signal.

  Here, the processing unit 22 generates a tomographic image from the acquired interference signal, but moves the near-side (inner side) zero-pass position from the position set as the initial position. An image cannot be generated. That is, the tomographic information generation means 86 adds the distance from the center of the probe outer cylinder 52 to the inner surface as an offset to each line, assuming that the first zero-pass position is coincident with the inner surface of the probe outer cylinder 52. 5 or a circular image centered on the axis of the probe outer cylinder 52 as shown in FIG. However, the first zero-pass position after the movement moves on an equal distance, which is further moved by a predetermined amount from the center of the probe outer cylinder 52. In other words, the first zero-pass position after the movement moves on the original first zero-pass position, that is, an equal distance moved by a predetermined amount from the inner surface of the probe outer cylinder 52. Therefore, the image based on the interference signal after moving the first zero-pass position shows a state where the actual positional relationship between the probe outer cylinder 52 and the measurement target S is different from the original processing setting.

  Therefore, when the tomographic information generating means 86 of the processing unit 22 generates a tomographic image, the movement amount of the zero path position and the distance between the centers of the original images are calculated, and a circle centering on the actual probe outer cylinder 52 is calculated. Calculate and display to be displayed. That is, the image is offset in the depth direction (or the optical axis direction) by the amount of movement of the zero path position.

  In this way, when the measurement target S and the probe outer periphery are in a non-contact state, the vicinity of the surface of the measurement target S can be measured with higher resolution by setting the zero-pass position on the surface of the measurement target S. it can.

  In the above example, the movement of the first zero path position is performed by adjusting the optical path length of the optical path length switching unit 34, but the first zero path position is moved by adjusting the optical path length adjusting unit 18. It may be.

  In the above description, the optical tomographic imaging apparatus that rotationally scans the measurement light has been described. However, the optical tomographic imaging apparatus of the present invention is also an apparatus that generates an optical tomographic image of a measurement target by performing planar scanning of the measurement light. Applicable.

  In the above description, the preferred embodiment has been described in which the zero path position is switched by switching the optical path length of the reference light L2. However, it is also possible to switch the zero path position by switching the optical path length of the measurement light L1. It is.

  The optical tomographic imaging apparatus and tomographic image acquisition method of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various improvements can be made without departing from the gist of the present invention. And changes may be made.

1 is a block diagram showing a schematic configuration of an embodiment of an optical tomographic imaging apparatus according to the present invention. It is a fragmentary sectional view which expands and shows the front-end | tip part of an optical probe. (A)-(C) are schematic diagrams which show the example of schematic structure of an optical path length switching part. It is a block diagram which shows schematic structure of an example of a process part. (A) And (B) is explanatory drawing of the example of a tomographic image acquired by the optical tomographic imaging apparatus shown in FIG. It is a block diagram which shows schematic structure of other embodiment of the optical tomographic imaging apparatus which concerns on this invention. It is a flowchart which shows an example of the switching method of a zero path position. It is a block diagram which shows schematic structure of the other example of a process part. It is explanatory drawing of the example of a tomographic image synthesize | combined by the image synthetic | combination means. It is a block diagram which shows schematic structure of the other example of a process part. It is explanatory drawing which shows the example of a display of a tomographic image. It is a typical graph which shows an example of the calculation result acquired by performing an FFT process to an interference signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 100 Optical tomographic imaging apparatus 12 Light source unit 14 Branching / multiplexing part 16 Optical probe 18 Optical path length adjustment part 20 Interference light detection part 22, 22A, 22B Processing part 24 Display part 26 Rotation drive part 28 Optical fiber coupler 30a, 30b Detection unit 32 Control unit 34 Optical path length switching unit 36 Operation unit 38 Parameter storage unit 40 Semiconductor optical amplifier 42 Optical splitter 44 Collimator lens 46 Diffraction grating element 48 Optical system 50 Rotating polygon mirror (polygon mirror)
52 Probe outer tube (sheath)
54 Cap 56 Optical fiber 58 Flexible shaft 60 Fixed member (sleeve)
62 optical lens 64 first optical lens 66 second optical lens 68 reflecting mirror 70 base 72 mirror drive mechanism 80 interference signal acquisition means 82 A / D conversion means 84 contact state detection means 86 tomographic information generation means 87 image composition means 87 image Correction means S Measurement object

Claims (18)

A wavelength swept light source;
A branching unit for branching light emitted from the wavelength swept light source into measurement light and reference light;
While irradiating the measurement light from the branch part to the measurement object, and a measurement part for acquiring the reflected light from the measurement object, an optical probe including in an outer cylinder,
An optical path length adjustment unit that sets the first reference position in the measurement depth direction at the inner edge of the measurement range by adjusting the optical path length of the reference light;
The optical path length of the reference light adjusted by the optical path length adjustment unit is preset with an optical path length that provides a second reference position that is a predetermined amount different in measurement depth from the first reference position and serves as an outer edge of the measurement range. An optical path length switching unit that switches between the first reference position and the second reference position by changing the length or the optical path length of the reflected light;
A control unit for controlling the optical path length adjusting unit and the optical path length switching unit;
A multiplexing unit that is arranged downstream of the optical path length adjustment unit and the optical path length switching unit, and combines the reflected light acquired by the measurement unit and the reference light to generate interference light;
An interference light detection unit that detects the interference light generated by the multiplexing unit as an interference signal;
An optical tomographic imaging apparatus comprising: a tomographic image acquisition processing unit that acquires a tomographic image from the interference signal detected by the interference light detection unit. The control unit switches the optical path length switching unit to the first reference position and the second reference position during measurement by the measurement unit,
The tomographic image acquisition processing unit acquires two tomographic images based on both the first reference position and the second reference position switched by the optical path length switching unit for the same measurement target. Optical tomographic imaging device. The control unit switches the optical path length switching unit to the first reference position and the second reference position in synchronization with a rotational scanning period or a plane scanning period of the measuring unit during measurement by the measuring unit,
The tomographic image acquisition processing unit includes the entire tomographic image based on the first reference position or a part on the first reference position side, and the entire tomographic image based on the second reference position or a part on the second reference position side. The optical tomographic imaging apparatus according to claim 2, wherein a combined tomographic image is acquired by combining the two.   The optical tomographic imaging apparatus according to claim 1, wherein the optical path length switching unit has a plurality of optical path lengths as optical path lengths for providing the second reference position. Furthermore, it has a parameter storage unit that holds parameters of the second reference position set in advance for each measurement site,
The said control part reads the parameter of the said 2nd reference position from the said parameter memory | storage part according to the input measurement site | part information, and switches the said optical path length switching part according to the read said parameter. Optical tomographic imaging device. The parameter storage unit has a plurality of the parameters for one measurement site information,
The optical tomography apparatus according to claim 5, wherein the control unit reads a parameter of the second reference position in accordance with input instruction information, and switches the optical path length switching unit in accordance with the read parameter. . The tomographic image acquisition processing unit includes a detection unit that detects a distance between a tip of the optical probe and a measurement target;
The control unit switches the optical path length switching unit to an optical path corresponding to the first reference position when the distance between the tip of the optical probe detected by the tomographic image acquisition processing unit and the measurement target is equal to or greater than a predetermined distance. The optical tomographic imaging apparatus according to claim 1.   When the distance between the tip of the optical probe detected by the tomographic image acquisition processing unit and the measurement target is equal to or greater than a predetermined distance, the control unit is arranged on the surface of the measurement target closest to the inner edge of the measurement range. The optical tomographic imaging apparatus according to claim 7, wherein the optical path length switching unit or the optical path length adjusting unit is adjusted so as to match a reference position. The optical probe includes a drive unit that rotates the measurement unit and an optical fiber that transmits the measurement light to the measurement unit and the reflected light from the measurement unit;
The tomographic image acquisition processing unit obtains a circular two-dimensional tomographic image corresponding to the rotation of the measuring unit, and the adjustment amount of the first reference position and the adjusted first reference position The optical tomographic imaging according to claim 8, wherein the tomographic image obtained based on the first reference position after the adjustment is corrected from a distance from the center of the tomographic image obtained for the first reference position before the adjustment. apparatus.   The optical tomographic imaging apparatus according to claim 1, wherein the optical path length switching unit includes a plurality of optical paths having different lengths and a switching unit that switches the plurality of optical paths.   The optical tomographic imaging apparatus according to claim 1, wherein the optical path length switching unit moves an optical path length adjusting unit of the optical path length adjusting unit to switch the optical path to a plurality of optical path lengths. A tomographic image acquisition method in the optical tomographic imaging apparatus according to claim 1,
When one of the first reference position and the second reference position is selected according to the measurement region of interest, the optical path length switching unit is switched to the selected one of the reference positions,
A tomographic image acquisition method for acquiring a tomographic image based on the switched reference position. A tomographic image acquisition method in the optical tomographic imaging apparatus according to claim 1,
During the measurement by the measurement unit, the optical path length switching unit is switched to the first reference position and the second reference position,
A tomographic image acquisition method for acquiring two tomographic images based on both the first reference position and the second reference position for the same measurement object. During the measurement by the measuring unit, the optical path length switching unit is switched to the first reference position and the second reference position in synchronization with the rotational scanning period or the planar scanning period of the measuring unit,
A combined tomographic image is obtained by synthesizing a portion on the first reference position side of a tomographic image based on the first reference position and a portion on the second reference position side of a tomographic image based on the second reference position. Item 14. The tomographic image acquisition method according to Item 13. A tomographic image acquisition method in the optical tomographic imaging apparatus according to claim 5,
A tomographic image acquisition method for reading a parameter of the second reference position from the parameter storage unit and switching the optical path length switching unit according to the read parameter when measurement site information is input. Detecting the distance between the tip of the optical probe and the measurement object,
The tomographic image acquisition method according to claim 12, wherein the first reference position is automatically selected when the detected distance between the tip of the optical probe and the measurement target is a predetermined distance or more.   When the detected distance between the tip of the optical probe and the measurement target is equal to or greater than a predetermined distance, the optical path length adjustment unit adjusts the first reference position to the surface of the measurement target closest to the inner edge of the measurement range. The tomographic image acquisition method according to claim 16, wherein adjustment is performed.   When obtaining a circular two-dimensional tomographic image corresponding to the rotation of the measurement unit, the adjustment amount of the first reference position, and the adjusted first reference position and the first reference position before adjustment are obtained. From the distance from the center of the tomographic image, the tomographic image obtained based on the first reference position after the adjustment is corrected, and an image similar to the tomographic image obtained for the first reference position before the adjustment is generated. The tomographic image acquisition method according to claim 17.

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