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WO2007083375A1 - Tomographe à cohérence optique dans le domaine de fourier utilisé pour la mesure dentaire - Google Patents

Tomographe à cohérence optique dans le domaine de fourier utilisé pour la mesure dentaire Download PDF

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Publication number
WO2007083375A1
WO2007083375A1 PCT/JP2006/300714 JP2006300714W WO2007083375A1 WO 2007083375 A1 WO2007083375 A1 WO 2007083375A1 JP 2006300714 W JP2006300714 W JP 2006300714W WO 2007083375 A1 WO2007083375 A1 WO 2007083375A1
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Prior art keywords
light
measurement
measured
sample
interference
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Ceased
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PCT/JP2006/300714
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English (en)
Japanese (ja)
Inventor
Toyohiko Yatagai
Yoshiaki Yasuno
Masami Tamura
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Shofu Inc
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Shofu Inc
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Priority to PCT/JP2006/300714 priority Critical patent/WO2007083375A1/fr
Publication of WO2007083375A1 publication Critical patent/WO2007083375A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/4795—Scattering, i.e. diffuse reflection spatially resolved investigating of object in scattering medium
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02041—Interferometers characterised by particular imaging or detection techniques
    • G01B9/02044—Imaging in the frequency domain, e.g. by using a spectrometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/0209—Low-coherence interferometers
    • G01B9/02091—Tomographic interferometers, e.g. based on optical coherence
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
    • A61B5/0062—Arrangements for scanning
    • A61B5/0066—Optical coherence imaging
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
    • A61B5/0082—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence adapted for particular medical purposes
    • A61B5/0088—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence adapted for particular medical purposes for oral or dental tissue

Definitions

  • the present invention relates to an optical coherence tomography (tomographic measurement using low coherence light as a probe), which is one of nondestructive tomographic techniques.
  • An image obtained by an X-ray imaging apparatus is merely a transmission image, and information on the X-ray traveling direction of a subject is detected by being superimposed. For this reason, it is impossible to know the internal structure of the subject in three dimensions. Also, because X-rays are harmful to the human body, the annual exposure dose is determined, so that only qualified operators can handle the device, and only in rooms surrounded by shielding materials such as lead glass. I can not use it.
  • an optical coherence tomography device (hereinafter referred to as an OCT device) is harmless to the human body and can obtain 3D information of a subject with high resolution. (For example, see Patent Documents 1 to 4).
  • FIG. 11 is a diagram showing the configuration of a conventional OCT apparatus.
  • the light emitted from the light source 2 is collimated by the lens 3 and then divided into reference light 6 and measurement light 5 by the beam splitter 4.
  • the measurement light 5 passes through the galvanometer mirror 8 and is collected by the objective lens 9 on the sample 10 to be measured. After being scattered and reflected, the measurement light 5 passes through the objective lens 9, the galvano mirror 8, and the peep splitter 4 again. The light is condensed on the detector 14.
  • the reference light 6 passes through the objective lens 12 and is reflected by the reference mirror 13. After passing through the beam splitter 4, it enters the condenser lens 7 in parallel with the measurement light 5 and is condensed on the photodetector 14.
  • the light source 2 is a temporally low coherence light source. Lights emitted at different times from light sources with low temporal coherence are extremely unlikely to interfere. Therefore, the interference signal force S appears only when the distance of the optical path through which the measurement light 5 passes and the distance of the optical path through which the reference light 6 passes are substantially equal.
  • the intensity of the interference signal is measured by the photodetector 14 while changing the optical path length difference between the measurement light 5 and the reference light 6 by driving the reference mirror 13 in the optical axis direction of the reference light 6, the sample to be measured A reflectance distribution in the depth direction (z-axis direction) of 10 can be obtained. In other words, the structure in the depth direction of the sample 10 to be measured is obtained by optical path length difference scanning.
  • Patent Document 1 Japanese Patent Laid-Open No. 2003-329577
  • Patent Document 2 JP 2002-310897
  • Patent Document 3 Japanese Patent Laid-Open No. 11-325849
  • Patent Document 4 JP 2001-059714 A
  • Non-patent document 1 Laser research October 2003 issue: Technology development of optical coherence tomography centered on medical treatment
  • Non-Patent Document 2 Journal of Biomedical Optics, October 2002, Vol.7 No.4: Imaging cari es lesions and lesion progression with polarization sensitive optical coherence tomog raphy
  • Non-Patent Document 3 APPLIED OPTICS, Vol.37, No.16, 1 June 1998: Imaging of hard- and soft-tissue structure In the oral cavity by optical coherence tomography
  • Non-Patent Document 4 OPTICS EXPRESS, Vol.3, No.6,14 September 1998: Dental OCT
  • Non-Patent Document 5 OPTICS EXPRESS, Vol.3, No.6,14 September 1998: In vivo OCT Ima ging of hard and soft tissue of the oral cavity
  • OCT devices are not used in actual dental practice. There is no OCT device for dental measurement that is not practical at present at the present time. This is because the OCT device requires two-dimensional mechanical scanning including the depth direction to obtain a single tomographic image, so it takes time to image, and the device is complicated, expensive, and durable. It is because it is inferior. In other words, there is a problem that it is difficult to apply the OCT device to actual dental measurements.
  • an object of the present invention is to provide an optical coherence tomography apparatus that has a simple structure, can be imaged at high speed, and can be applied to dental measurements.
  • a Fourier domain optical coherence tomography device for dental measurement includes a light source, reference light for irradiating a reference mirror with light source light emitted from the light source, and a sample to be measured.
  • a light splitting unit that divides the measurement light to be radiated on, an interference unit that causes interference between the measurement light reflected by the measurement sample and the reference light reflected by the reference mirror, and the interference light.
  • a diffractive element that splits the light a light detector that measures the spectrum of the interference light dispersed by the diffractive element, and an inverse Fourier transform of the vector detected by the light detector, whereby the sample to be measured
  • a calculation unit that obtains information on the irradiation direction of the measurement light, and the sample to be measured is a living oral cavity region tissue or an artificial composition of the oral cavity region.
  • a Fourier domain optical coherence tomography device for dental measurement includes a light source, reference light for irradiating a reference mirror with light source light emitted from the light source, and a sample to be measured.
  • a light splitting unit that divides the measurement light to be radiated on, an interference unit that causes interference between the measurement light reflected by the measurement sample and the reference light reflected by the reference mirror, and the interference light.
  • a diffraction element that splits the light
  • a light detection unit that measures the spectrum of the interference light split by the diffraction element, and a scan detected by the light detection unit.
  • An arithmetic unit that obtains information on the measurement light irradiation direction of the sample to be measured by inverse Fourier transform of the vector, and at least one polarization of the light source light, the reference light, the measurement light, or the interference light
  • a polarization operation unit for manipulating the state is provided, and the sample to be measured is a tissue of the jaw and mouth region of a living body or an artificial composition of the jaw and mouth region.
  • an optical coherence tomography device includes a light source, measurement light that irradiates a reference mirror and a sample to be measured with a light source emitted from the light source.
  • a light splitting unit that divides the light into light, an interference unit that causes the measurement light reflected by the sample to be measured and the reference light reflected by the reference mirror to interfere with each other, and light detection that measures the interference light
  • a calculation unit that obtains information of the sample to be measured based on the interference light measured by the light detection unit, and a nonlinear optical element provided on the optical path of the reference light.
  • an optical coherence tomography apparatus that has a simple structure, can be imaged at high speed, and can be applied to dental measurements.
  • FIG. 1 is a diagram illustrating an example of a configuration of a Fourier domain optical coherence tomography apparatus (hereinafter referred to as an FD-OCT apparatus) in the first embodiment.
  • FD-OCT apparatus Fourier domain optical coherence tomography apparatus
  • FIG. 2 is a diagram illustrating an example of a configuration of an FD-OCT apparatus according to a second embodiment.
  • FIG. 3 is a diagram illustrating an example of a configuration of an FD-OCT apparatus according to a third embodiment.
  • FIG. 1 is a schematic diagram showing the configuration of the light source light polarization controller 35.
  • (b) is a schematic diagram showing the configuration of the reference light polarization manipulator 36 or the interference light polarization manipulator 37.
  • FIG. 1 is a schematic diagram showing the configuration of the light source light polarization controller 35.
  • FIG. 5 is a conceptual diagram for explaining an example of a method for driving a lens.
  • FIG. 6 is a diagram showing a configuration of a light source of the OCT apparatus.
  • FIG. 7 is a diagram illustrating an example of a configuration of an FD-OCT apparatus according to a fifth embodiment.
  • FIG. 8 is a diagram showing a configuration near a reference mirror of an OCT apparatus in a sixth embodiment.
  • FIG. 9 is a diagram illustrating an example of a configuration of an FD-OCT apparatus according to a seventh embodiment.
  • FIG. 10 is a diagram illustrating an example of a configuration of an FD-OCT apparatus according to an eighth embodiment.
  • FIG. 11 is a diagram showing a configuration of a conventional OCT apparatus. Explanation of symbols
  • a Fourier-domain optical coherence tomography device for dental measurement includes a light source, reference light that irradiates a reference mirror with light source light emitted from the light source, and measurement light that irradiates a sample to be measured.
  • a splitting light splitting unit an interference unit that causes the measurement light reflected by the sample to be measured and the reference light reflected by the reference mirror to interfere with each other to form interference light, a diffraction element that splits the interference light, and By detecting the spectrum of the interference light spectrally separated by the diffraction element and performing Fourier inverse transform on the spectrum detected by the light detection unit, information on the measurement light irradiation direction of the sample to be measured is obtained.
  • the sample to be measured is a living tissue of the oral cavity region or an artificial composition of the oral region of the oral cavity.
  • the interference light is split by a diffraction element, so that the light detection unit can detect the spectrum of the interference light.
  • the calculation unit obtains information on the irradiation direction of the measurement light of the sample to be measured by performing Fourier inverse transform on the spectrum of the interference light. Therefore, information in the depth direction of the sample to be measured can be obtained without mechanical scanning in the irradiation direction of the measurement light, that is, the depth direction of the sample to be measured.
  • the structure of the device is simplified and high-speed imaging is possible.
  • an OCT device that can be applied to dental diagnosis with a patient placed in a treatment chair generally used in dentistry is obtained.
  • the light splitting unit and the interference unit have both functions by using a beam splitter or a fiber single bra.
  • a Fourier-domain optical coherence modality device for dental measurement according to the present invention irradiates a reference light and a sample to be measured with a light source, and light source light emitted from the light source.
  • a light splitting unit that divides the light into measurement light, and is reflected by the sample to be measured.
  • an interference unit that causes the measurement light and the reference light reflected by the reference mirror to interfere with each other to form interference light, a diffraction element that splits the interference light, and a spectrum of the interference light that is split by the diffraction element.
  • a light detection unit for measuring the light a calculation unit for obtaining information in the measurement light irradiation direction of the sample to be measured by performing Fourier transform on the spectrum detected by the light detection unit, the light source light,
  • a polarization manipulation unit that manipulates at least one polarization state of the reference light, the measurement light, or the interference light, and the sample to be measured is a living tissue of the jaw-and-mouth region or an artificial composition of the mouth-and-mouth region. is there.
  • the polarization operation unit includes at least one of light irradiated from the light source to the light splitting unit, the reference light, the measurement light, or the interference light. Since one polarization state is manipulated, an image reflecting the polarization characteristic or birefringence characteristic of the sample to be measured can be obtained. As a result, it is possible to observe oral tissues rich in specific polarization characteristics or birefringence characteristics such as initial caries' dentin / enamel / gingiva'alveolar bone.
  • a Fourier domain optical coherence tomography device for dental measurement according to the present invention is a cylindrical lens or It is preferable to further include a cylindrical mirror.
  • a cylindrical lens is a lens that acts as a lens in only one of two directions perpendicular to the optical axis, and only the surface of at least one of the cross sections in the direction acting as a lens is unique to the lens.
  • the cross section in the direction that does not act as a lens is a straight line parallel to both surfaces.
  • a cylindrical mirror is a mirror that acts as a lens in only one of two directions perpendicular to the optical axis. Only the surface of the cross section in the direction acting as a lens is a characteristic curve of the lens. The cross section in the direction not acting as a lens is a straight line.
  • the cylindrical lens or the cylindrical mirror makes the cross section of the measurement light linear along a single axial direction in a plane perpendicular to the irradiation direction of the measurement light. Distributed irradiation is performed in the uniaxial direction. That is, the measurement light is condensed on the line in the uniaxial direction in the measurement sample. Therefore, it is possible to measure the cross section in the uniaxial direction of the sample to be measured without mechanical scanning in the uniaxial direction.
  • the spectrum expanded in the one-axis direction is a light beam spread in two dimensions, that is, the direction of the spectrum and an expanded direction perpendicular to the direction of the spectrum. Furthermore, it is preferable that the two-dimensional light detection unit is a two-dimensional CCD image sensor or a two-dimensional CMOS image sensor.
  • the optical fiber is preferably an optical fiber whose cross section is bundled in a one-dimensional linear or two-dimensional circle.
  • An optical coherence tomography device for dental measurement projects the measurement light or visible light pattern on the surface of the object to be measured, and monitors the surface image of the measurement site with a two-dimensional imaging device, or further It is preferable to adopt a mode in which recording is performed synchronously with the tomographic measurement image.
  • FIG. 1 is a diagram illustrating an example of a configuration of a Fourier domain optical coherence tomography apparatus (hereinafter referred to as an FD-OCT apparatus) in the first embodiment.
  • FD-OCT apparatus Fourier domain optical coherence tomography apparatus
  • the FD-OCT apparatus detects a spectrum obtained by dispersing the interference light between the measurement light reflected by the sample to be measured and the reference light reflected by the reference mirror, and this spectral force is measured by the measurement light of the sample to be measured.
  • This is an OCT device characterized by obtaining information on the irradiation direction using inverse Fourier transform.
  • the FD-OCT apparatus includes an OCT unit 100, a measurement head 201, and a computer 27.
  • the OCT unit 100 is provided with a light source 16, a fiber coupler 19, a reference mirror 24, a diffraction element 25, and a CCD camera 26.
  • the measuring head 201 is provided with a galvanometer mirror 20 and an objective lens 21.
  • the computer 27 is connected so as to be able to communicate with the light source 16, the CCD camera 26, and the galvanometer mirror 20.
  • the computer 27 is, for example, a personal computer, and includes at least a calculation unit such as a CPU and a recording unit such as a hard disk. Note that the configurations of the OCT unit 100, the measurement head 201, and the computer 27 are not limited to the configurations shown in FIG. For example, the function of the calculator 27 can be incorporated in the OCT unit 100.
  • the sample 22 to be measured is a living tissue of the oral cavity region or an artificial composition of the oral region of the jaw.
  • the light source 16 is a temporally low coherent light source. In other words, it is a light source whose wavelength is distributed in a narrow range.
  • the light source 16 is preferably a superluminescent diode, for example.
  • the fiber coupler 19 is an example of an optical interferometer that functions as a light splitting unit and an interference unit.
  • An optical interferometer is an input / output interchangeable optical component that outputs two directions by causing two input lights to interfere with each other. Examples of the optical interferometer include a beam splitter and a half mirror in addition to the fiber coupler 19.
  • the diffraction element 25 is a reflective or transmissive optical member having a diffraction spectroscopic function.
  • the diffraction element 25 is preferably, for example, a grating element, a diffraction grating, a prism, or the like.
  • the diffraction element 25 may be a slice of an optical recording medium. Examples of optical recording media include CD, DVD, and MO.
  • the CCD camera 26 is an example of a light detection unit.
  • a one-dimensional light detector, a two-dimensional light detector, or the like can be used.
  • a linear CCD is preferred for the one-dimensional photodetector, and a CCD imaging device and a CMOS imaging device are preferred for the two-dimensional photodetector.
  • the two-dimensional photodetector includes a two-dimensional imaging device.
  • the measurement head 201 is preferably configured so that the operator can operate it by hand. By transmitting light between the OCT unit 100 and the measurement head 201 by the optical fiber 18, the movable range of the measurement head 201 is widened.
  • the OCT device When the OCT device is applied to dentistry, it is assumed that the OCT device is used on the chair side of the chair where the patient is usually sitting during medical examination. In this case, in order to position the measurement head, the entire OCT unit must be precisely positioned in the patient's oral cavity in the aerial optical system (the optical path to the measurement head is in the air, not the optical fiber). It is also unrealistic for an operator to operate a relatively heavy OCT unit.
  • the measurement head 201 has a configuration that can be operated by an operator by hand, it can be easily used by the operator on the chair side in dental practice. The operator can use the OCT device when the positional relationship between the patient and the measurement head is free.
  • the coordinate system is defined as follows.
  • the optical axis direction of the measurement light 28 that is, the depth direction of the sample 22 to be measured is z
  • the tomographic plane is the zy plane (the galvano mirror 20 scan direction is y).
  • x, y, z are directions corresponding to x, y, z of the sample 22 to be measured.
  • X the optical axis direction of the measurement light 28 that is, the depth direction of the sample 22 to be measured
  • the tomographic plane is the zy plane (the galvano mirror 20 scan direction is y).
  • x, y, z are directions corresponding to x, y, z of the sample 22 to be measured.
  • Optically means that even if the spatial direction changes with a mirror or lens, such as an optical fiber, the light travel direction is z, and the direction scanned with a galvanometer mirror is y, both z and y.
  • the vertical direction is X.
  • the light emitted from the light source 16 is collimated by the lens 17 and then divided into reference light 29 and measurement light 28 by the fiber coupler 19.
  • the measuring light 28 passes through the optical fiber 18 and the galvano mirror 20 and is collected by the objective lens 21 on the sample 22 to be measured, and after being scattered and reflected, the objective light 21, the galvano mirror 20, the optical fiber 18 and the fiber coupler 19 are again passed. Then, the light is guided to the diffraction element 25 by the condenser lens 30.
  • the reference light 29 passes through the optical fiber 18 and the objective lens 23, is reflected by the reference mirror 24, and again passes through the objective lens 23 and is caused to interfere with the measurement light 28 by the fiber coupler 19. Parallel to 28, it enters the condenser lens 30 and is guided to the diffraction element 25.
  • the measurement light 28 and the reference light 29 are simultaneously dispersed by the diffraction element 25 and overlapped in the spectral region, so that spectral interference fringes on the CCD camera 26, that is, the combined power of the measurement light 28 and the reference light 29 A spectrum is formed.
  • a spectral correlation fringe measured by the CCD camera 26 is subjected to inverse Fourier transform in a computer 27, whereby a combined correlation between the measurement light 28 and the reference light 29 is obtained. From this coupling correlation, information on the structure, composition, or optical characteristics can be obtained through the reflectance characteristics of the sample 22 to be measured in the depth direction (z-axis direction).
  • the OCT device is an FD-OCT device.
  • scanning in the y-axis direction is performed by driving a galvano mirror 20.
  • a scanning method in the y-axis direction in addition to a method of driving the calano mirror 20, a method of using a cylindrical lens described later, a method of driving a lens, a method of driving an optical fiber, and a sample 22 to be measured are used.
  • a driving method or a method in which an operator moves the measuring head 201 can be used.
  • FIG. 5 is a conceptual diagram for explaining an example of a method for driving a lens.
  • a linear actuator 31 is connected to one end of the lens 30, and the other end of the lens 30 is fixed to the apparatus.
  • the lens 30 performs an arc-shaped reciprocating motion around the rotation shaft 32.
  • the optical axis of the lens 30 moves in the zy plane, and the sample to be measured is scanned in the y direction.
  • the measurement head 201 can be operated by hand, and a FD-OCT apparatus having a simple structure capable of high-speed imaging can be obtained.
  • Dentistry FD—OCT equipment can be obtained.
  • FIG. 2 is a diagram illustrating an example of the configuration of the FD-OCT apparatus according to the second embodiment.
  • the same parts as those in the FD-OCT apparatus shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.
  • the FD-OCT apparatus shown in FIG. 2 is different from the FD-OCT apparatus shown in FIG. 1 in that a cylindrical lens 33 is provided and a beam splitter 34 is used instead of the fiber coupler 19. And the scanning direction of the galvanometer mirror 20.
  • the force that uses the method of driving the carpano mirror 20 as the scanning method in the y-axis direction instead of scanning in the y-axis direction by the carpano mirror 20, Light expansion in the y-axis direction by the cylindrical lens 33 is adopted.
  • the cylindrical lens 33 is a normal lens having a cross-section in a plane including the optical axis and a direction that functions as a lens, and the cross-sectional shape is the same regardless of a position in a direction that does not function as a lens.
  • the cylindrical lens 33 is arranged so as to have a directional force y direction that functions as a lens. In other words, the light spread in the y direction by the cylindrical lens 33 is distributed and irradiated in the y direction of the sample 22 (the y direction on the cylindrical lens 33 and the y direction of the sample 22 are optically the same). Direction, not necessarily spatially the same direction).
  • the cylindrical lens 33 is the y-direction light expansion means.
  • the cross section of the measurement light is linear along the y-axis direction.
  • the optical fiber 18 Since the measurement light is spatially expanded in the y-axis direction, when this light is guided by one optical fiber, the optical fiber 18 has its cross section bundled on a one-dimensional line. An optical fiber or optical fiber with cross sections bundled in a two-dimensional circle is required. [0062]
  • the direction of the grooves of the diffraction element 25 is preferably the y-axis direction.
  • the cross section in the y-axis direction of the sample 22 to be measured can be obtained by CCD without mechanical scanning in the y-axis direction. Can be obtained with a camera 26 one-shot. Therefore, the carpano mirror 20 can obtain a three-dimensional structure of the sample 22 to be measured only by scanning in the X-axis direction.
  • the apparatus becomes simple and inexpensive, and an FD-OCT apparatus that can be applied to dental measurement is obtained.
  • the FD-OCT apparatus that is effective in the present embodiment is not limited to force dental measurement that is preferably used for dental measurement, and can also be used for measurement in other fields.
  • the force described for the FD-OCT apparatus is not necessarily the FD-OCT apparatus but may be a conventional OCT apparatus.
  • the CCD camera 26 may be a photodetector using a simple mirror instead of the diffraction element 25.
  • FIG. 3 is a diagram illustrating an example of a configuration of the FD-OCT apparatus according to the third embodiment.
  • the same parts as those in the FD-OCT apparatus shown in FIG. 3 are identical to the FD-OCT apparatus shown in FIG. 3.
  • the FD-OCT apparatus shown in FIG. 3 is different from the FD-OCT apparatus shown in FIG. 1 in that a light source light polarization controller 35, a reference light polarization controller 36, and an interference light polarization controller 37 are provided. It is a point.
  • FIG. 4 (a) is a schematic diagram showing the configuration of the light source light polarization controller 35.
  • the polarizer 67 is a member that allows only a specific polarization component to pass therethrough
  • the 1Z2 wavelength plate 68 and the 1Z4 wavelength plate 69 are members that shift the wavelength of the transmitted light by 1Z2 wavelength or 1Z4 wavelength, respectively. It is.
  • the polarizer 67 gives basic polarization characteristics to the light source light or the measurement light.
  • the direction of polarization can be manipulated by rotating the 1Z2 wavelength plate 68 and the 1Z4 wavelength plate 69 at an appropriate angle around the optical axis. By using these wave plates 68 and 69, the polarization state of the light source light or measurement light can be set arbitrarily.
  • FIG. 4B is a schematic diagram showing the configuration of the reference light polarization manipulator 36 or the interference light polarization manipulator 37. These are composed of 1Z2 wave plate 70 and 1Z4 wave plate 71. By adjusting the angle, the polarization state of the reflected light can be examined.
  • the polarization state of light can be expressed by a four-component vector (four-dimensional vector) Si.
  • the substance in order to measure the matrix M representing the birefringence characteristics of a substance, the substance is passed through light having a polarization state represented by any four vectors, Detecting the beta component.
  • This Mueller matrix can be measured at each measurement point of the object
  • Biological tissues including oral tissues each have unique polarization characteristics and / or birefringence characteristics. Therefore, according to the present embodiment, birefringence characteristics of tooth buds and periodontal tissues can be detected.
  • Collagen in particular has a large birefringence characteristic, and for example, it becomes possible to discriminate between enamel that does not contain collagen and dentin that contains a large amount of collagen.
  • this embodiment is a case where a polarization controller is provided in the FD-COT device shown in FIG.
  • a polarization controller is provided in the FD-COT device shown in FIG.
  • the present invention is not limited to this.
  • the present invention can also be applied to the FD-OCT apparatus in Embodiment 2 shown in FIG.
  • the OCT apparatus according to the fourth embodiment can apply the OCT apparatus according to the first to third embodiments or the conventional OCT apparatus to the parts other than the parts described below, the description thereof is omitted.
  • FIG. 6 is a diagram showing the configuration of the light source of the OCT apparatus in the present embodiment.
  • the light source 16 of the FD-OCT apparatus shown in FIG. 1 is a single single wavelength light source.
  • two or more light sources 56 a, 56 b, 56 c having different wavelengths are provided instead of the light source 16.
  • the light sources 56a, 56b, 56c are preferably superluminescent diodes in the wavelength range of 300 nm to 3000 nm.
  • the light source used for measurement is switched by driving the rotating mirror 57. That is, the light sources 56a, 56b, and 56c are arranged at positions corresponding to specific angles of the rotating mirror 57.
  • a galvanometer mirror can be used as the rotating mirror 57.
  • the wavelength dependency of the light absorption coefficient, transmission coefficient, and reflection coefficient varies.
  • the reflection coefficient of enamel and dentin, which have a high transmission coefficient of cementum and alveolar bone is relatively large.
  • soft tissues such as gingiva are highly permeable to light having a wavelength of around 1300 nm. Is optimal.
  • carious tissue since carious tissue has different fluorescence characteristics in the visible light region from normal tissue, it is necessary to use a light source that matches the wavelength of the fluorescence. Therefore, it has been difficult to visualize the entire structure of oral tissues using a conventional OCT device that uses a single-wavelength light source.
  • the OCT apparatus includes two or more light sources 56a, 56b, and 56c having different wavelengths. Therefore, by appropriately selecting the wavelength of the light source, for example, oral tissue or oral cavity tissue or the like It is possible to visualize the fine structures of substances with various light absorption coefficients, transmission coefficients, and reflection coefficients.
  • FIG. 7 is a diagram illustrating an example of the configuration of the FD-OCT apparatus according to the fifth embodiment.
  • the same parts as those in the FD-OCT apparatus shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. Note that this embodiment can be applied to the FD-OCT apparatus according to Embodiments 1 to 3 shown in FIG. 2 or the conventional OCT apparatus.
  • the difference between the FD-OCT apparatus shown in FIG. 7 and the FD-OCT apparatus shown in FIG. 2 is that a noro light source 59 and half mirrors 58 and 60 are provided.
  • the pilot light source 59 is provided for irradiating pilot light projected onto the sample 22 to be measured.
  • the no-lot light is light that is irradiated on the imaging range so that an operator who performs measurement using the OCT apparatus can check the imaging site and imaging range during or before and after imaging.
  • the pilot light emitted from the nolot light source 59 is preferably visible light.
  • the pilot light emitted from the pilot light source 59 is guided on the same optical axis as the light source light emitted from the light source 16 by the half mirror 58.
  • the nano light is projected onto the sample 22 to be measured together with the light source light and the measurement light. This projection can be observed visually, and the same place as the measurement light is irradiated, so the operator can recognize the measurement range.
  • the cross-section of the pilot light may be point-like or linear. In the case of pilot light having a point-like cross section, it is preferable that the pilot light is arranged on the central optical axis of the measurement light. If the cross section is linear pilot light, the cross section of the pilot light is preferably arranged along the y direction of the measurement light. Since the OCT apparatus shown in FIG. 7 employs a cylindrical lens 33, the pilot light passes through the cylindrical lens 33 and is irradiated onto the sample 22 to be measured in a cross-sectional line shape.
  • the pilot light reflected from the sample 22 to be measured passes through the beam splitter 34 together with the measurement light, and is irradiated onto the diffraction element 25 together with the interference light.
  • a half mirror 60 that reflects at least visible light and transmits at least infrared light is provided in front of the diffractive element 25, so that interference light passes through the diffractive element 25 and pilot light is reflected by the half mirror 60. Detected by CCD camera 26.
  • the CCD camera 26 is a 2D-CCD camera as a 2D-photodetector used for FD-OCT, which uses a 2D-CCD power lens with a visible light sensitivity band and a cylindrical lens as a 2D imaging device. It is preferable to use both. This allows the CCD camera 26 to Visible light image of tooth is obtained together with interference spectral image by OCT.
  • a 2D-CCD camera that has a sensitivity band for visible light is provided separately from the CCD camera 26, and the force on the measurement optical axis is also a sensitivity band for visible light using a half mirror 60 or the like.
  • a visible light image of the sample to be measured 22 can also be obtained by directing pilot light to a 2D-CCD camera with area.
  • a 2D CCD camera having a sensitivity band in visible light can use a two-dimensional imaging device having a sensitivity band in the range of 300 nm to 3000 nm.
  • a liquid crystal shutter may be interposed between the half mirror 60 and the diffractive element 25 so that only a visible light image is captured except during imaging by OCT.
  • the half mirror 60 may be driven by a rotating or linear drive mechanism so that the pilot light is separated from the optical system during OCT imaging.
  • the optical fiber 18 is preferably composed of an image fiber capable of transmitting an image.
  • the computer 27 can monitor an image of a measurement site using pilot light. Furthermore, it is possible to record a visible light image of the measurement site by pilot light in synchronization with the tomographic image.
  • the FD-OCT apparatus according to the first to third embodiments or the conventional OCT apparatus can be applied to the parts other than the parts described below, and the description thereof is omitted.
  • FIG. 8 is a diagram showing a configuration in the vicinity of the reference mirror of the OCT apparatus in the present embodiment.
  • the phase of the reference light is changed by inserting a phase modulation element on the reference optical path or moving the reference mirror in the optical axis direction.
  • FIG. 8 (a) is a diagram showing a configuration example of an apparatus when a phase modulation element is inserted on the reference optical path.
  • a phase modulation element 62 is inserted in front of the reference mirror 24.
  • the phase modulation element 62 is driven by an electrical drive signal.
  • a rapid scanning optical delay line (RSOD) an acousto-optic element, an electro-optic element, or the like is preferably used.
  • Fig. 8 (b) shows the phase of the reference light changed by moving the reference mirror in the optical axis direction. It is a figure which shows the structural example of the apparatus in the case of making it do.
  • the reference mirror 24 is provided with a piezoelectric element 63.
  • the piezoelectric element 63 is driven by an electrical drive signal.
  • the piezoelectric element 63 vibrates in the optical axis direction of the reference light
  • the reference mirror 24 is vibrated in the same direction as the optical axis direction of the reference light.
  • the phase of the reference light is changed.
  • the phase of the reference light can be changed by the phase modulation element 62 or the piezoelectric element 63, and therefore, the five sets of diffractions in which the phase of the reference light is shifted by 90 degrees, for example.
  • a spectral interference light intensity distribution can be obtained. If the shape of the sample to be measured in the depth direction (z-axis direction) is measured using this diffraction spectral interference light intensity distribution, the measurement range in the depth direction can be doubled. The principle will be described in detail below.
  • the measurement range of FD-OCT is principally determined by the resolution of the diffraction element, the objective lens, and the CCD camera, and as a result, the measurement range in the depth direction is determined.
  • the light intensity distribution (one-dimensional or two-dimensional) on the ⁇ axis of the diffraction element obtained by the CCD is Fourier-transformed by a computer and converted into a distribution on the time t axis (that is, the depth of the sample to be measured) converted to a reflection characteristic distribution on the z-axis).
  • the result of inverse Fourier transform is based on the distribution of the complex conjugate signal of the autocorrelation of the reference light and the cross-correlation of the reference light and the z-direction object reflection light in the depth z-axis direction. It is superimposed as an image (artifact) caused by a device defect regardless of the subject. For this reason, it is assumed that the measurement of the diffraction spectral interference image on the diffractive element can measure not only the light intensity distribution but also the phase distribution of the light. The measurement range is halved.
  • Direct measurement of the phase of the diffracted spectral interference light is a fast phenomenon that can be detected because the phenomenon is too fast (a phenomenon that is less than a few femtoseconds when the wavelength of light is divided by the speed of light). There is no detector. Therefore, the phase of the diffracted spectral interference light is indirectly measured by modulating the spatial phase instead of the temporal phase phenomenon. That is, the phase modulation element 62 or the piezoelectric element 63 can obtain five sets of diffraction / spectral interference light intensity distributions in which the phase of the reference light is shifted by 90 degrees, for example.
  • This diffraction spectrum interference light intensity distribution is subjected to inverse complex Fourier transform in the computer 27, so that the autocorrelation of the reference light and the cross-correlation of the reference light and the reflected sample light in the z direction (measurement light) Outside Artifa
  • the FD—OCT original measurement range in the depth direction is realized.
  • FIG. 9 is a diagram illustrating an example of the configuration of the FD-OCT apparatus according to the seventh embodiment.
  • the same parts as those in the FD-OCT apparatus shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. Note that this embodiment can be applied to the FD-OCT apparatus according to Embodiments 1 to 3 shown in Fig. 1 or the conventional OCT apparatus.
  • the computer 27 sends a light amount modulation signal together with the ONZOFF signal to the electrical modulator 64.
  • the electrical modulator 64 sends a light amount control signal based on the light amount modulation signal to the light source 16.
  • the output light amount of the light source 16 is controlled by a light amount control signal output from the electrical modulator 64.
  • the data detected by the CCD camera 26 is demodulated by the computer 27 in accordance with the light intensity modulation signal. This modulation / demodulation improves the SZN ratio of the detected data.
  • the modulation and demodulation schemes may be AM modulation and FM modulation, for example.
  • an optical modulator may be provided on the optical path of the light emitted from the light source 16 instead of the electrical modulator 64.
  • an optical modulator may be provided on the optical path of the measurement light (object reflected light) 28 or the optical path of the reference light 29. It is also possible to provide a modulator that performs modulation in synchronization with the position of the sample 22 to be measured and the reference mirror 24.
  • the measurement range of an OCT apparatus is principally determined by the resolution of the objective lens, but in reality the range is narrowed by the effect of noise. That is, since the measurement light attenuates as it enters the sample 22 to be measured, the z-direction object reflected light becomes buried in noise as the depth of the sample to be measured increases. This narrows the measurement range in the depth direction.
  • the light source light, the measurement light, or the reference light is modulated and the detection signal is detected, so that the SZN ratio is improved and the measurable range is expanded.
  • FIG. 10 is a diagram illustrating an example of the configuration of the FD-OCT apparatus according to the eighth embodiment.
  • the same parts as those in the FD-OCT apparatus shown in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
  • this embodiment can be applied to the FD-OCT apparatus according to the first to third embodiments or the conventional OCT apparatus, which is not limited to the FD-OCT apparatus shown in FIG.
  • the FD-OCT apparatus shown in FIG. 10 is different from the FD-OCT apparatus shown in FIG. 1 in that a nonlinear optical element 65 is provided on the optical path of the reference light 29 and a filter 66 is provided. It is a point.
  • the nonlinear optical element 65 is an optical element that generates a harmonic in the vibration waveform of light, and is preferably, for example, a beta barium baudate.
  • a filter 66 that cuts the wavelength component of the light source light on the optical path of the interference light after passing through the fiber coupler 19 and passes the wavelength component of the half wavelength of the light source light is provided.
  • harmonics are generated in the vibration waveform of the reference light 29 by providing the nonlinear optical element 65 on the reference light.
  • the second harmonic component in this reference harmonic and the second harmonic component of the measurement light 28 are caused to interfere by the fiber coupler 19.
  • the fluorescence characteristic of the sample 22 to be measured can be detected more clearly.
  • the tomographic image discrimination of lesions such as caries is improved.
  • the living body exhibits remarkable second-harmonic fluorescence characteristics due to two-photon absorption. This is because when electrons bound to biological constituent atoms receive energy equivalent to two photons of the measurement light and jump to a high potential energy level, they return to the original level. This is the fluorescence that emits light.
  • the potential energy level of second-order harmonic fluorescence has levels in almost all wavelength bands close to a continuous band. Furthermore, what is characteristic of this second-order harmonic fluorescence is that it generates fluorescence that is synchronized with the incident measurement light, that is, the coherency of the OCT device is maintained.
  • This second harmonic fluorescence Light is emitted from inside the sample 22 to be measured, and part of it is returned as reflected light (measurement light 28).
  • the nonlinear optical element 65 is provided on the path of the reference light 29, a harmonic is generated in the vibration waveform of the reference light 29.
  • the fluorescence characteristics inside the sample 22 to be measured can be detected. Therefore, for example, it is effective for diagnosis of lesions such as caries accompanied by changes in fluorescence characteristics.
  • the FD-OCT apparatus or the conventional OCT apparatus according to the first to third embodiments can be applied to the parts other than the parts described below, and the description thereof is omitted.
  • an image obtained by measurement is displayed on, for example, a monitor provided in the computer 27.
  • a monitor provided in the computer 27.
  • the OCT tomographic image of the OCT is displayed as it is, it will be an image with some discomfort.
  • the OCT apparatus according to the present embodiment provides an easy-to-see image by performing the following display.
  • the one-shot measurement range in the OCT device is smaller than the tooth size.
  • the distance in the depth direction (z-axis direction) of the sample to be measured in the OCT image is an optical distance, not an actual distance. Therefore, it is preferable to display the optical distance corrected to the spatial distance.
  • the depth direction corrected for shading based on the optical distance or the integrated amount of reflection.
  • the measurement resolution is displayed as a rough point display, dot density display, or rough gradation display. For this reason, it is preferable to display a display in which the grayscale display based on the point density is corrected to a solid display.
  • the image obtained by measurement is a tomographic image of the object, it is difficult to grasp the spatial position and direction. Therefore, it is preferable to display the tomographic image in a three-dimensional manner on the pilot monitor image. In addition, it is preferable to provide a user interface that allows the observer to arbitrarily select a display section.
  • the captured image may include noise. Therefore, it is preferable to display a plurality of tomographic images or an image obtained by integrating and averaging the plurality of images to remove temporal noise and improve the spatial resolution. Alternatively, an image obtained by integrating and averaging a plurality of slice images obtained by scanning in the vertical direction (X direction) and removing spatial noise in the X direction may be displayed. Furthermore, it is also possible to display an image obtained by integrating and averaging multiple tomographic images and removing noise in the X and Z or y directions.
  • the present invention can be used particularly in the field of dentistry as an optical coherence tomography apparatus that can perform high-speed measurement and has a simple structure and is inexpensive.

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Abstract

L'invention concerne un tomographe à cohérence optique dans le domaine de Fourier utilisé pour la mesure dentaire, comprenant une source de lumière (16), un élément de séparation de lumière (19) destiné à séparer la lumière émise par la source lumineuse (16) en une lumière de référence (29) dirigée vers un miroir de référence (24) et une lumière de mesure (28) dirigée vers un échantillon-objet de mesure (22), un élément d'interférence (19) destiné à provoquer une interférence entre la lumière de mesure (28) et la lumière de référence (29) afin de générer une lumière d'interférence, un élément de diffraction (25) destiné à disperser la lumière d'interférence, un capteur optique (26) destiné à mesurer le spectre produit par la dispersion par l'élément de diffraction (25), ainsi qu'un élément de calcul (27) destiné à exécuter une transformée de Fourier inverse du spectre et ainsi à collecter des informations relatives à la lumière de mesure de l'échantillon-objet de mesure dans le sens d'application de la lumière. L'échantillon-objet de mesure (22) est une région stomatognathique d'un organisme ou une composition artificielle dans la région stomatognathique. Le tomographe à cohérence optique peut être adapté pour la mesure dentaire.
PCT/JP2006/300714 2006-01-19 2006-01-19 Tomographe à cohérence optique dans le domaine de fourier utilisé pour la mesure dentaire Ceased WO2007083375A1 (fr)

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JP2010256294A (ja) * 2009-04-28 2010-11-11 Topcon Corp 光画像計測装置
WO2011102118A1 (fr) * 2010-02-16 2011-08-25 財団法人ヒューマンサイエンス振興財団 Procédé de fabrication d'un élément de revêtement dentaire et appareil de conception assistée par ordinateur (cad)/fabrication assistée par ordinateur (cam) dentaire
JP2013019884A (ja) * 2011-07-08 2013-01-31 Chung Yuan Christian Univ 光断層撮影システム
CN114631779A (zh) * 2020-12-15 2022-06-17 株式会社湖碧驰 断层摄影融合式口腔扫描仪
JP2023155486A (ja) * 2016-04-06 2023-10-20 ケアストリーム デンタル エルエルシー 圧縮センシングによる口腔内ｏｃｔ

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Publication number Priority date Publication date Assignee Title
JP2010256294A (ja) * 2009-04-28 2010-11-11 Topcon Corp 光画像計測装置
WO2011102118A1 (fr) * 2010-02-16 2011-08-25 財団法人ヒューマンサイエンス振興財団 Procédé de fabrication d'un élément de revêtement dentaire et appareil de conception assistée par ordinateur (cad)/fabrication assistée par ordinateur (cam) dentaire
JP2013019884A (ja) * 2011-07-08 2013-01-31 Chung Yuan Christian Univ 光断層撮影システム
JP2023155486A (ja) * 2016-04-06 2023-10-20 ケアストリーム デンタル エルエルシー 圧縮センシングによる口腔内ｏｃｔ
JP7629963B2 (ja) 2016-04-06 2025-02-14 デンタル・イメージング・テクノロジーズ・コーポレーション 圧縮センシングによる口腔内ｏｃｔ
CN114631779A (zh) * 2020-12-15 2022-06-17 株式会社湖碧驰 断层摄影融合式口腔扫描仪

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