1. Field of the Invention
The present invention relates to an OCT optical probe and an optical tomography imaging apparatus, and particularly to an OCT optical probe having a function of scanning with light in a circumferential direction with respect to the long axis of the OCT optical probe, and an optical tomography imaging apparatus that acquires an optical tomographic image of a subject to be measured through OCT (Optical Coherence Tomography) measurement using the OCT optical probe.
2. Description of the Related Art
As a method for acquiring a tomographic image of a subject to be measured, such as a body tissue, a method using OCT measurement to acquire a tomographic image has been proposed. An OCT measurement system is one of optical interferometers. In the OCT measurement, low-coherent light emitted from a light source is divided into measurement light and reference light. The measurement light is applied to a subject to be measured, and then reflected light or backscattered light from the subject to be measured is combined with the reference light. Then, a tomographic image is acquired based on intensity of interference light formed between the reflected light and the reference light. Hereinafter, reflected light and backscattered light from the subject to be measured are collectively referred to as reflected light.
OCT measurement techniques are roughly classified into TD (Time Domain)-OCT measurement techniques and FD (Fourier Domain)-OCT measurement techniques.
In the TD-OCT measurement, the interference intensity is measured while the optical path length of the reference light is changed, thereby acquiring an intensity distribution of the reflected light corresponding to depth-wise positions in the subject to be measured.
In the FD-OCT measurement, the optical path lengths of the reference light and the signal light are fixed, and intensity of the interference light is measured for each spectral component of the light. Then, the thus acquired spectral interference intensity signals are subjected to frequency analysis, typically Fourier transformation, on a computer, thereby acquiring an intensity distribution of the reflected light corresponding to the depth-wise positions. Recently, the FD-OCT measurement is attracting attention since it does not require mechanical scanning on which the TD-OCT measurement relies, and therefore allows high speed measurement.
Typical systems that carry out the FD-OCT measurement include an SD (Spectral Domain)-OCT system and an SS (Swept Source)-OCT system.
The SD-OCT system uses wideband low-coherent light, decomposes the interference light into optical frequency components using a spectral means, measures intensity of the interference light for each optical frequency component using an arrayed photodetector, or the like, and applies Fourier transformation analysis to the thus acquired spectral interference waveform on a computer, to form a tomographic image.
The SS-OCT system uses, as a light source, a laser with optical frequency thereof swept with time, to measure temporal waveforms of signals corresponding to temporal changes of the optical frequency of the interference light, and applies Fourier transformation to the thus acquired spectral interference intensity signals on a computer, to form a tomographic image.
Further, it has been considered to combine any of the above-described optical tomography imaging systems with an endoscope for use in in-vivo measurement, and an OCT optical probe that can be inserted into a forceps channel of an endoscope has been known.
Such an OCT optical probe includes a distal end portion to be inserted in a body cavity, and a proximal end portion including a mechanism for moving light emitted from the distal end portion to scan in at least one-dimensional direction to acquire a tomographic image along a certain plane of the subject to be measured.
Japanese Patent No. 3104984 discloses an OCT optical probe that includes: a sheath to be inserted into a subject; a flexible shaft that is rotatable within the sheath about an axis extending in the longitudinal direction; an optical fiber covered with the flexible shaft; a distal optical system that deflects light emitted from the optical fiber at a substantially right angle with respect to the longitudinal direction, wherein the flexible shaft is rotated via a gear by a motor disposed at the proximal end, thereby rotating the distal optical system about the axis.
Jianping Su et al., “In vivo three-dimensional microelectromechanical endoscopic swept source optical coherence tomography”, Optics Express, Vol. 15, Issue 16, pp. 10390-10396, 2007, discloses, along with the development of MEMS (Micro Electro Mechanical Systems) techniques, an OCT optical probe that includes an MEMS motor disposed within the sheath in the vicinity of the distal end of the OCT optical probe, and a distal optical system fixed to the output shaft of the MEMS motor to rotate, so that the distal optical system is rotated about the shaft.
However, the conventional OCT optical probe disclosed in Japanese Patent No. 3104984, as shown in
In the OCT optical probe disclosed in Jianping Su et al., “In vivo three-dimensional microelectromechanical endoscopic swept source optical coherence tomography”, Optics Express, Vol. 15, Issue 16, pp. 10390-10396, 2007, as shown in
In view of the above-described circumstances, the present invention is directed to providing an OCT optical probe and an optical tomography imaging apparatus using the OCT optical probe, that can inexpensively and safely eliminate the prior art problem of degradation in measurement accuracy due to optical insertion loss and optical reflection loss caused at optical coupling at a rotary joint disposed between an optical fiber at a distal end portion side and an optical fiber at a proximal end portion.
An OCT optical probe according to the invention includes: a substantially cylindrical sheath to be inserted into a subject, the sheath having an internal space; an optical fiber disposed in the internal space of the sheath along the longitudinal direction of the sheath; a rotatably-supporting portion integrally fixed to the optical fiber in the vicinity of a distal end of the optical fiber; a distal optical system to deflect light emitted from the distal end of the optical fiber toward the subject; a holding portion to hold the distal optical system such that the distal optical system is rotatably supported by the rotatably-supporting portion; and a flexible shaft covering the optical fiber in the internal space of the sheath, wherein the holding portion is fixed to a distal end of the flexible shaft. The term “substantially cylindrical” refers to a shape that may not necessarily be strictly cylindrical about a straight axis from one end to the other end, and the sheath may include a gently curved shape, such as a semispherical shape, at the distal end thereof. Further, the cross-sectional shape of the sheath may not necessarily be a mathematically-strict circle, and may be ellipsoidal, or the like. The “distal end” of the flexible shaft may not necessarily refer to the distal end of the flexible shaft, and may also refer to a position in the vicinity of the distal end.
The rotatably-supporting portion of the OCT optical probe according to the invention may include a bearing portion to rotatably support the holding portion.
Further, a fiber sheath to cover the optical fiber along the longitudinal direction may be provided between the optical fiber and the flexible shaft.
The distal end of the optical fiber of the OCT optical probe according to the invention may have an end face that is inclined by a predetermined angle with respect to a plane perpendicular to an optical axis of the optical fiber.
The OCT optical probe according to the invention may further include a cover glass, the proximal end of the cover glass may closely contact the distal end of the optical fiber, and the distal end of the cover glass may have a flat end face that is perpendicular to the optical axis.
The OCT optical probe according to the invention may further include a cover glass, the proximal end of the cover glass may closely contact the distal end of the optical fiber, and the distal end of the cover glass may have a convex end face that is adapted to collimate the light emitted from the distal end of the cover glass to be parallel to the optical axis.
An optical tomography imaging apparatus according to the invention is formed by an optical tomography imaging apparatus using any of the above-described measuring techniques, which employs the OCT optical probe according to the invention. Namely, the optical tomography imaging apparatus according to the invention includes: a light source unit to emit light; a light dividing unit to divide the light emitted from the light source unit into measurement light and reference light; an irradiation optical system to irradiate a subject to be measured with the measurement light; a combining unit to combine the reference light with reflected light of the measurement light reflected from the subject to be measured when the measurement light is applied to the subject; an interference light detecting unit to detect interference light formed between the combined reflected light and reference light; and a tomographic image processing unit to detect reflection intensity at a plurality of depth-wise positions in the subject to be measured based on frequency and intensity of the detected interference light, and to acquire a tomographic image of the subject to be measured based on the intensity of the reflected light at each of the depth-wise positions, wherein the irradiation optical system comprises the OCT optical probe of the invention.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, outline of an optical tomography imaging apparatus is described.
The optical tomography imaging apparatus includes: an endoscope 50 including the OCT optical probe 1; a light source unit 51, to which the endoscope 50 is connected; a video processor 52; an optical tomography processing unit 53; and a monitor 54 connected to the video processor 52.
The light source unit 51 applies measurement light L1 to a portion of a subject to be measured Sb, from which a tomographic image P is acquired, as described later.
The endoscope 50 includes a flexible and elongated insert portion 55, a manipulation unit 56 joined to the proximal end of the insert portion 55, and a universal code 57 extending from a side of the manipulation unit 56. A light source connector 58 is disposed at the end of the universal code 57, and the light source connector 58 is removably connected to the light source unit 51. A signal cable 59 extends from the light source connector 58, and a signal connector 60, which is removably connected to the video processor 52, is disposed at the end of the signal cable 59.
The insert portion 55 is inserted, for example, into a body cavity, and is used for observing the subject to be measured Sb. The distal end portion of the insert portion 55 is bendable, and a manipulation knob 61 for manipulating the distal end portion of the insert portion 55 to bend is provided at the manipulation unit 56. A forceps channel 64, which is a conduit shown by the dashed line in the drawing, is formed in the insert portion 55 along the longitudinal direction thereof, so that the OCT optical probe 1 or a treatment tool such as a forceps can be inserted through the forceps channel 64. One end of the forceps channel 64 is open at the distal end of the insert portion 55 to form a distal end opening 64a. The other end of the forceps channel 64 forms a forceps insertion port 64b, which is located above the manipulation unit 56. The OCT optical probe 1 is inserted through the forceps insertion port 64b and through the forceps channel 64, and the distal end of the OCT optical probe 1 is projected from the distal end opening 64a, so that the measurement light L1 can be applied to the subject to be measured Sb. It should be noted that, although not shown in the drawing, the distal end of the insert portion 55 is provided with an observation window used for observing the subject to be measured Sb, an illumination window through which the illumination light is applied, air and water supply nozzles used for removing dirt, and the like.
The OCT optical probe 1 includes a flexible and long distal end portion 10, a proximal end portion 20 joined to the proximal end of the distal end portion 10, and an optical fiber 12.
The distal end portion 10 is inserted through the forceps channel 64, which is shown by the dashed line in the drawing, to be inserted into a body cavity, as described above. The distal end portion 10 has a length of around 3 m.
One end of the optical fiber 12 is removably connected to the optical tomography processing unit 53 via an optical tomography connector 62, and the other end of the optical fiber 12 is inserted through the proximal end portion 20 and the distal end portion 10 to extend to an area in the vicinity of the distal end of the distal end portion 10.
Now, the OCT optical probe 1 of the invention is described in detail.
The optical fiber 12 is inserted into and fixed to the rotatably-supporting portion 14 with an adhesive. The measurement light L1 emitted from the distal end of the optical fiber 12 enters the distal optical system 15, and reflected light L3 enters the distal end of the optical fiber 12 via the distal optical system 15.
Preventing unnecessary reflected light from the optical fiber 12 and distal optical system 15 can advantageously improve sensitivity to the interference signal. For example, the amount of reflected light at the distal end of the optical fiber 12 can be reduced by cutting the distal end of the optical fiber 12 obliquely. Further, the amount of reflected light re-entering the optical fiber 12 can be reduced by providing a curved light input surface at the distal optical system 15. In addition, a cover glass, which has a refractive index matched with the optical fiber 12 and has a distal end face that is flat and perpendicular to an optical axis LP, may be provided between the distal end of the optical fiber 12 and the light entrance surface of the distal optical system 15, and the proximal end of the cover glass may be closely bonded to the distal end of the optical fiber 12 with an adhesive. That is, according to this method, reflection at the distal end the optical fiber 12 can be reduced by refraction matching and re-entrance of the reflected light at the distal end of the cover glass into the optical fiber 12 can be reduced by spread of the measurement light L1, thereby reducing the amount of the light re-entering into the optical fiber 12. The distal end of the cover glass may be provided with an AR coating. This method is applicable to either of the cases where the distal end of the optical fiber 12 is flat, and the distal end of the optical fiber 12 is obliquely cut. It should be noted that the structure for reducing the amount of the reflected light usable in the invention is not limited to those described above.
The distal optical system 15 has a substantially spherical shape. The distal optical system 15 deflects the measurement light L1 emitted from the optical fiber 12 and collects and directs the measurement light L1 toward the subject to be measured Sb. The distal optical system 15 also deflects the reflected light L3 from the subject to be measured Sb and collects and directs the reflected light L3 toward the optical fiber 12. The focal length (focal position) of the distal optical system 15 is formed, for example, at a distance D=around 3 mm in the radial direction of the sheath 11 from the optical axis LP of the optical fiber 12. The measurement light L1 emitted from the distal optical system 15 is inclined by an angle of about seven degrees from a direction perpendicular to the optical axis LP. The distal optical system 15 is fixed to the holding portion 16 with an adhesive.
The holding portion 16 is fitted around the rotatably-supporting portion 14 such that a plurality of bearing balls 14b in a groove 14a formed in the outer circumferential surface of the rotatably-supporting portion 14 are respectively positioned in a plurality of holes 16a formed in the inner circumferential surface of the holding portion 16, to form a bearing portion 17. Thus, the holding portion 16 is held rotatably about the optical axis LP relative to the rotatably-supporting portion 14.
The bearing portion 17 is described in detail.
Referring again to
Now, another embodiment of the distal optical system is described.
In this embodiment, the distal optical system is formed by a reflecting member 15 having a concave surface, and is fixed to the holding portion 16. Although the holding member 16 shown in
Further, in the embodiment shown in
As shown in
In the embodiment shown in
Now, a first embodiment of the OCT optical probe 1 of the invention is described.
In the first embodiment, the sheath 11 is fitted in and fixed to a housing 25, and a shaft bearing 22 is disposed in the housing 25. The flexible shaft 13 is fixed to a shaft supporting member 21, and the shaft supporting member 21 is held to be rotatable relative to the housing 25 via the shaft bearing 22. The optical fiber 12 is fixed to the housing 25. A driven gear wheel 23 is fixed to the outer circumference of the shaft supporting member 21, and a driving gear wheel 24 is disposed to mesh with the driven gear wheel 23. The driving gear wheel 24 is fixed to the output shaft of the motor 26, which is disposed in the housing 25. The motor 26 includes an encoder 27 for detecting a rotational angle. A control signal MC fed to the motor 26 and a rotation signal RS fed from the encoder 27 are transmitted via a control cable (not shown). Specifically, the rotation signal RS includes a rotation clock signal RCLK, which is generated for each rotation of the motor 26, and a rotational angle signal Rpos.
Now, operation of the first embodiment is described. As the motor 26 rotates in the direction of arrow R2, the shaft supporting member 21 and the flexible shaft 13 fixed to the shaft supporting member 21 rotate, via the driven gear wheel 23 and the driving gear wheel 24, relative to the housing 25 in the direction of arrow R3. This also makes the distal optical system 15, which is fixed to the holding portion 16 at the distal end of the flexible shaft 13, rotate via the bearing portion 17 relatively to the rotatably-supporting portion 14 about the optical axis LP in the direction of arrow R1. Therefore, the OCT optical probe 1 applies the measurement light L1 emitted from the distal optical system 15 to the subject to be measured Sb with moving the measurement light L1 to scan in the direction of arrow R1 about the optical axis LP, i.e., along the circumferential direction of the sheath 11. Specifically, the rotational frequency is around 10-30 Hz, however, this is not intended to limit the invention. If the processing speed of a tomographic image processing unit 150, which will be described later, is high, a higher rotation speed can be used. The rotational frequency may not necessarily be fixed, and may be changed depending on the speed of movement of or the resolution required for the subject to be measured Sb. Specifically, a higher rotation speed maybe used for a subject to be measured Sb that has a high speed of movement or that does not require a high resolution, and a lower rotation speed may be used for a subject to be measured Sb that has a low speed of movement or that requires a high resolution.
Further, the distal optical system 15 can be pivoted about the optical axis LP within a predetermined range of angle by controlling the direction of rotation of the motor 26 according to the control signal MC based on the rotation signal RS. The range of pivot angle can be set to a desirable range based on the shape of the subject to be measured Sb. For example, for a subject to be measured Sb having a cylindrical shape, such as a bronchial tube, the range of pivot angle may be substantially 360 degrees about the longitudinal axis, and for a subject to be measured Sb having a flat shape, such as stomach wall, the range of pivot angle may be around 180 degrees about the longitudinal axis, however, this is not intended to limit the invention. The frequency of pivot is the same as the above-described frequency of rotation. Further, if the frequency of pivot is equal to the natural frequency of the flexible shaft 13, the flexible shaft 13 is resonantly driven, and therefore a driving force can be reduced.
Now, a second embodiment of the OCT optical probe 1 of the invention is described.
In the second embodiment shown in
Now, operation of the second embodiment is described. When the electric magnet 68 is excited, the electric magnet 68 and the permanent magnet 18 interact with each other to establish a relationship of a stator and a rotor of a brushless motor, and thus the flexible shaft 13 rotates in the direction of arrow R3 about the optical axis LP via the permanent magnet 18.
Further, the direction of rotation of the optical fiber 12 may be inverted to make the distal optical system 15 pivot about the optical axis LP within a predetermined range of angle by controlling the order of excitation of the electric magnet 68 according to the control signal MC based on the rotation signal RS.
It should be noted that, in the second embodiment of the invention, the electric magnet 68 may be disposed at the outer circumference of the flexible shaft 13, and the permanent magnet 18 may be disposed at the outer circumference of the forceps channel 64. In this case, the distal end portion 10 is insulated so that the excitation of the electric magnet 68 at the outer circumference of flexible shaft 13 may not exert adverse effect, such as electrical shock, on the human body.
The operation effected by the rotation of the flexible shaft 13 is the same as that in the first embodiment, and explanation thereof is omitted. Further, the pivot angle and the frequency of rotation and pivot are the same as those in the first embodiment, and explanations thereof are omitted.
Now, the optical tomography imaging apparatus, to which the OCT optical probe 1 according to the invention is applied, is described.
The optical tomography imaging apparatus 100 is an optical tomography imaging apparatus using SS-OCT measurement. The optical tomography imaging apparatus 100 includes: a light source unit 110 for emitting laser light L; an optical fiber coupler 2 for dividing the laser light L emitted from the light source unit 110; a period clock generating unit 120 for outputting a period clock signal TCLK from the light divided by the optical fiber coupler 2; a light dividing means 3 for dividing one of light beams divided by the optical fiber coupler 2 into the measurement light L1 and the reference light L2; an optical path length adjusting unit 130 for adjusting the optical path length of the reference light L2 divided by the light dividing means 3; the OCT optical probe 1 for guiding the measurement light L1 divided by the light dividing means 3 to the subject to be measured Sb; a combining means 4 for combining the reference light L2 with the reflected light L3 from the subject to be measured Sb when the measurement light L1 emitted from the OCT optical probe 1 is applied to the subject Sb; an interference light detecting unit 140 for detecting interference light L4 formed between the reflected light L3 and the reference light L2 combined by the combining means 4; a tomographic image processing unit 150 for acquiring a tomographic image P of the subject to be measured Sb by applying frequency analysis to the interference light L4 detected by the interference light detecting unit 140; and a displaying means 160 for displaying the tomographic image P.
The light source unit 110 in this apparatus emits the laser light L with the wavelengths thereof swept in a constant period T0. Specifically, the light source unit 110 includes a semiconductor optical amplifier (semiconductor gain medium) 111 and an optical fiber FB10. The optical fiber FB10 is connected to opposite ends of the semiconductor optical amplifier 111. When a driving current is injected, the semiconductor optical amplifier 111 emits weak light to one end of the optical fiber FB10, and amplifies the light inputted from the other end of the optical fiber FB10. As the driving current is supplied to the semiconductor optical amplifier 111, pulsed laser light L generated by an optical resonator formed by the semiconductor optical amplifier 111 and the optical fiber FB10 is emitted to the optical fiber FB0.
Further, a circulator 112 is coupled to the optical fiber FB10, so that a portion of light guided through the optical fiber FB10 is emitted from the circulator 112 to an optical fiber FB11. The light emitted from the optical fiber FB11 travels through a collimator lens 113, a diffraction optical element 114 and an optical system 115, and is reflected by a rotating polygon mirror 116. The reflected light travels back through the optical system 115, the diffraction optical element 114 and the collimator lens 113, and re-enters the optical fiber FB11.
The rotating polygon mirror 116 rotates at a high speed, such as around 30,000 rpm, in the direction of arrow R1, and the angle of each reflection facet with respect to the optical axis of the optical system 115 varies. Therefore, among the spectral components of the light split by the diffraction optical element 114, only the component of a particular wavelength range returns to the optical fiber FB11. The wavelength of the light returning to the optical fiber FB11 is determined by an angle between the optical axis of the optical system 115 and the reflection facet. Then, the light of the particular wavelength range entering the optical fiber FB11 is inputted from the circulator 112 to the optical fiber FB10. As a result, the laser light L of the particular wavelength range is emitted to the optical fiber FB0.
Therefore, when the rotating polygon mirror 116 rotates at a constant speed in the direction of arrow R1, the wavelength λ of the light re-entering the optical fiber FB11 varies with time in a constant period. As shown in
The wavelength-swept laser light L is emitted to the optical fiber FB0, and the laser light L is further inputted to branched optical fibers FB1 and FB5 by the optical fiber coupler 2. The light emitted to the optical fiber FB5 is guided to the period clock generating unit 120.
The period clock generating unit 120 outputs the period clock signal TCLK each time the wavelength of the laser light L emitted from the light source unit 110 is swept for one period. The period clock generating unit 120 includes optical lenses 121 and 123, an optical filter 122 and a photodetector unit 124. The laser light L emitted from the optical fiber FB5 enters the optical filter 122 via the optical lens 121. The laser light L transmitted through the optical filter 122 is then detected by the photodetector unit 124 via the optical lens 123, and the period clock signal TCLK is outputted to the tomographic image processing unit 150.
As shown in
As shown in
The light dividing means 3 is formed, for example, by a 2×2 optical fiber coupler, and divides the laser light L guided from the light source unit 110 via the optical fiber FB1 into the measurement light L1 and the reference light L2. Two optical fibers FB2 and FB3 are optically connected to the light dividing means 3, so that the measurement light L1 is guided through the optical fiber FB2 and the reference light L2 is guided through the optical fiber FB3. It should be noted that the light dividing means 3 in this embodiment also serves as the combining means 4.
The optical fiber FB2 is optically connected to the OCT optical probe 1, so that the measurement light L1 is guided to the OCT optical probe 1. The OCT optical probe 1 applies the measurement light L1 emitted from the distal end portion 10 to the subject to be measured Sb, and the reflected light L3 is guided by the optical fiber FB2 through the OCT optical probe 1.
The optical path length adjusting unit 130 is disposed at the side of the optical fiber FB3 from which the reference light L2 is emitted. The optical path length adjusting unit 130 changes the optical path length of the reference light L2 to adjust the position at which acquisition of the tomographic image is started. The optical path length adjusting unit 130 includes: a reflection mirror 132 for reflecting the reference light L2 emitted from the optical fiber FB3; a first optical lens 131a disposed between the reflection mirror 132 and the optical fiber FB3; and a second optical lens 131b disposed between the first optical lens 131a and the reflection mirror 132.
The first optical lens 131a serves to collimate the reference light L2 emitted from the optical fiber FB3 and to collect the reference light L2 reflected from the reflection mirror 132 onto the optical fiber FB3.
The second optical lens 131b serves to collect the reference light L2 collimated by the first optical lens 131a onto the reflection mirror 132 and to collimate the reference light L2 reflected from the reflection mirror 132.
That is, the reference light L2 emitted from the optical fiber FB3 is collimated by the first optical lens 131a, and then is collected by the second optical lens 131b onto the reflection mirror 132. Thereafter, the reference light L2 reflected from the reflection mirror 132 is collimated by the second optical lens 131b, and then is collected by the first optical lens 131a onto the optical fiber FB3.
The optical path length adjusting unit 130 further includes: a base 133 on which the second optical lens 131b and the reflection mirror 132 are fixed; and a mirror moving means 134 for moving the base 133 along the optical axis of the first optical lens 131a. The optical path length of the reference light L2 can be changed by moving the base 133 in the direction of arrow A.
The combining means 4 is formed by a 2×2 optical fiber coupler, as described above. The combining means 4 is adapted to combine the reference light L2 having the optical path length adjusted by the optical path length adjusting unit 130 with the reflected light L3 from the subject to be measured Sb, and emit the combined light to the interference light detecting unit 140 via the optical fiber FB4.
The interference light detecting unit 140 detects the interference light L4 between the reflected light L3 and the reference light L2 combined by the combining means 4, and outputs the interference signal IS. It should be noted that, in this apparatus, the interference light L4 is divided into two parts by the light dividing means 3 and these parts are guided to the photodetectors 140a and 140b to be calculated, so that balanced detection is carried out. The interference signal IS is outputted to the tomographic image processing unit 150.
The interference signal acquiring unit 151 acquires the interference signal IS for one period, which is detected by the interference light detecting unit 140, based on the period clock signal TCLK outputted from the period clock generating unit 120. The interference signal acquiring unit 151 acquires the interference signal IS of a wavelength band DT (see
The interference signal converting unit 152 rearranges the interference signal IS acquired by the interference signal acquiring unit 151 in equal intervals along the wavenumber k (=2π/λ) axis.
The interference signal analyzing unit 153 acquires the tomographic information r(z) by applying a known spectral analysis technique, such as the Fourier transformation, the maximum entropy method, or the Yule-Walker method, to the interference signal IS converted by the interference signal converting unit 152.
The rotation control unit 156 outputs the control signal MC to the motor 26 or the electric magnet 68, and receives the rotation signal RS inputted from the encoder 27 or the magnetic sensor. As described above, the rotational position signal RS includes the rotation clock signal RCLK, which is generated for each rotation of the motor 26 or the flexible shaft 13, and the rotational angle signal Rpos.
The tomographic information generating unit 154 acquires the tomographic information r(z), which corresponds to scanning by the distal end portion 10 of the OCT optical probe 1 in the radial direction (in the direction of arrow R1 in the drawing), for one period (one line) acquired by the interference signal analyzing unit 153, and generates a tomographic image P as shown in
The tomographic information generating unit 154 can generate the tomographic image P by reading the tomographic information r(z) for n lines at a time from the tomographic information storing unit 154a based on the rotation clock signal RCLK inputted to the rotation control unit 156.
Alternatively, the tomographic information generating unit 154 can generate the tomographic image P by sequentially reading the tomographic information r(z) from the tomographic information storing unit 154a based on the rotational angle signal Rpos inputted to the rotation control unit 156.
The image quality correction unit 155 applies correction, such as sharpness correction and smoothness correction, to the tomographic image P generated by the tomographic information generating unit 154.
The displaying means 160 displays the tomographic image P, which has been subjected to the correction, such as sharpness correction and smoothness correction, applied by the image quality correction unit 155.
As described above, in the OCT optical probe 1 of the invention and the optical tomography imaging apparatus 100 employing the OCT optical probe 1, no rotary joint is provided, and the light emitted from the distal end of the optical fiber 12 directly enters the distal optical system 15. Therefore, the problem of degradation of measurement accuracy due to the optical insertion loss and optical reflection loss at the rotary joint can be eliminated inexpensively and safely.
Also, in the optical tomography imaging apparatus 100 according to the invention, to which the above-described OCT probe 1 of the invention is applied, the problem of degradation of measurement accuracy due to the optical insertion loss and optical reflection loss at the rotary joint can be eliminated inexpensively and safely.
Although the optical tomography imaging apparatus, to which the OCT optical probe 1 of the invention is applied, has been described as an SS-OCT apparatus in the above embodiment by way of example, the OCT optical probe 1 of the invention is also applicable to SD-OCT and TD-OCT apparatuses.
In the OCT optical probe of the invention, the distal optical system is rotated by the flexible shaft via the holding portion relative to the rotatably-supporting portion that is integrally fixed to the distal end portion of the optical fiber. Therefore, the light emitted from the light source unit is guided through the optical fiber and directly enters the distal optical system from the distal end of optical fiber.
Thus, it is not necessary to provide a rotary joint between the distal end portion and the proximal end portion of the OCT optical probe, and therefore the problem of optical insertion loss and optical reflection loss at the rotary joint can be avoided. Further, since no driving means, such as an MEMS motor, is provided in the vicinity of the distal end, problems such as increase of the outer diameter of the OCT optical probe and an adverse effect exerted on image acquisition by a drive cable for the MEMS motor can be avoided.
Using the OCT probe according to the invention, the problem of degradation of measurement accuracy due to the optical insertion loss and optical reflection loss at the rotary joint can be eliminated inexpensively and safely.
Also, in the optical tomography imaging apparatus according to the invention, to which the above-described OCT probe according to the invention is applied, the problem of degradation of measurement accuracy due to the optical insertion loss and optical reflection loss at the rotary joint can be eliminated inexpensively and safely.
Number | Date | Country | Kind |
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2008-022359 | Feb 2008 | JP | national |
2008-164003 | Jun 2008 | JP | national |