Abstract:
Provided are an optical connector and an optical tomographic imaging apparatus, by which no noise occurs and a high quality image without a distortion can be obtained. In the optical connector, optical fibers are inserted into a lumen of a tube from opposite ends thereof; one of the optical fibers is fixed to the tube and the other optical fiber is held so as to be rotatable relative to the tube; an end of one of the optical fibers is separated from an end of the other optical fiber to form a gap therebetween in the lumen; a connecting section which connects the exterior space of the tube and the gap is formed; and a liquid or fluid made of a material which can transmit light is held in the exterior space, the gap, and the connecting section. Consequently, a significant pressure variation in matching liquid does not occur if the distance between the facing optical fibers changes

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an optical connector and an optical tomographic imaging apparatus. 
       BACKGROUND ART 
       [0002]    A method to taking a tomograpic image of human tissue noninvasively by using low coherent interference is known (for example, Patent Literature 1). In the tomograpic imaging, low coherence light emitted from a light source is divided into irradiation light and reference light. The irradiation light is irradiated to human tissues through a light guide. On the other hand, the reference light enters a movable mirror in an optical path length adjusting section. After that, the irradiation light (scattered light) reflected by respective tissues of a human body and the reference light reflected by the movable mirror are combined, and reference light having the same optical path length as the optical path length of the reference light is participate in interference at that place. Accordingly, by analyzing the intensity of interfering light, there can be obtained a tomographic image of tissues corresponding to scattered light having the optical path length which is the same as the optical path length of the reference light. By using the theory of the optical tomography, a tomographic image of tissues which spread in a broad area can be obtained. For example, an optical fiber wherein a rectangular prism is arranged on its leading end is inserted in a blood vessel, and the optical path length of the reference light is changed corresponding to the tomographic imaging position while scanning is carried out with the irradiation light in the circumference direction by rotating the optical fiber on the longitudinal axis. Thereby, a tomographic image of a blood vessel can be obtained. 
         [0003]    As described above, in the optical tomography in which scanning is carried out with the irradiation light in the circumference direction, a light guide tube for guiding the irradiation light which has been separated from the reference light is composed of, for example, an optical fiber (non-rotating optical fiber) which guides the irradiated light which has been separated and a second optical fiber (rotary scanning optical fiber) which receives the irradiated light from the former optical fiber to guide the light to the rectangular prism at the leading end and rotates on the longitudinal axis. In this case, it is required that the first optical fiber and the second optical fiber are optically connected together with the second optical fiber being rotatable with respect to the first optical fiber. 
         [0004]    Patent Literature 2 discloses an optical connector which meets the above demands. The optical connector of Patent Literature 2 employs a structure that plural optical lenses are arranged between the end section of the first optical fiber and the end section of the second optical fiber and light emitted from one of the end section of the optical fibers is converged by the lenses to enter into the other end section of the optical fibers. However, as for the optical connector, it is required that small lenses are mounted in a small area with accuracy. 
         [0005]    Another optical connector which solves the defect of the lens-type connector disclosed in Patent Literature 2, is disclosed, for example, in Patent Literature 3. The optical connector disclosed i n  Patent Literature 3 connects the ends of the first and second optical fibers by closing the ends in a narrow space in a tube shape, whereby the ends are optically connected without using lenses. Refractive-index matching liquid is deposited in the gap between the ends to reduce Fresnel reflection that light is reflected on the end surfaces of the optical fibers. 
         [0006]    However, a rotating optical fiber oscillates in the longitudinal direction corresponding to its rotation, which changes the distance of the opposite surfaces of the two optical fibers. This change in distance is propagated to the matching liquid filling the space between the optical fibers, which causes a change of the liquid in pressure and changes of the liquid in density and refractive index coming from the change in pressure. The change in refractive index brings generation of noise and distortion of the tomographic image, which are problems. 
         [0007]    Further, when negative pressure is applied to the matching liquid, bubbles are generated or flows in the matching liquid and the light propagating efficiency is significantly reduced because the bubbles block an optical path. Concretely, in the case of a single-mode optical fiber, the outer diameter of a clad is about 125 μm and the pressure of the matching liquid considerably changes when the interval of the two optical fibers changes by only  1  mm in the direction of the longitudinal axis, which can make bubbles easily. The generation of bubbles causes the problem that a tomograpic image cannot be formed. 
         [0008]    Citation List 
       Patent Literature 
       [0009]    Patent document 1: Japanese Translation of PCT International Application Publication No. H06-511312 
         [0010]    Patent document 2: U.S. Pat. No. 6,687,010 
         [0011]    Patent document 3: U.S. Pat. No. 5,949,929 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0012]    In view of the above problems, the present invention is aimed at providing an optical connector and optical tomographic imaging apparatus which do not generate noise and enable to obtain an excellent tomograpic image without distortion. 
       Solution To Problem 
       [0013]    An optical connector described in claim  1  is an optical connector comprising a tube, wherein optical fibers are inserted into a lumen of the tube from both sides of the tube, one of the optical fibers is held in a non-rotating condition relatively to the tube, the other of the optical fibers is held in a rotatable condition relatively to the tube, an end of one of the optical fiber and an end of the other of the optical fiber are separated in the lumen to form a gap between the ends, and one of the optical fibers and the other of the optical fibers are optically connected through the gap. The optical connector is characterized by further comprising a connecting section for connecting an exterior space of the tube and the gap, wherein the exterior space, the gap and the connecting section hold liquid or fluid composed of a material which can transmit light. 
         [0014]    An optical connector described in claim  2  is the optical connector of clam  1 , characterized in that the connecting section is formed in at least one of the tube, the one of the optical fibers and the other of the optical fibers. 
         [0015]    An optical connector described in claim  3  is the optical connector of claim  1  or  2 , characterized by further comprising: a stator stationarily arranged so as not to rotate; and a rotator supported so as to be rotatable on a center axis of the tube relatively to the stator, wherein the exterior space is formed with the stator and the rotator, and an end section of the one of the optical fiber or the other optical fiber is fixed to the rotator. 
         [0016]    An optical connector described in claim  4  is the optical connector of claim  3 , characterized in that the tube is fixed to the rotator. 
         [0017]    An optical connector described in claim  5  is the optical connector of claim  3 , characterized in that the tube is fixed to the stator. 
         [0018]    An optical connector described in claim  6  is the optical connector of claim  1 , characterized in the connecting section is formed in a tube member arranged between at least one of the one of the optical fiber and the other of the optical fiber, and the tube. 
         [0019]    An optical tomographic imaging apparatus described in claim  7  is provided for obtaining a tomographic image of a subject by a way that light emitted from a light source is divided into irradiation light and reference light, the irradiation light is guided with an optical fiber, and interfering light of the irradiation light and the reference light is detected while the subject is irradiated with the irradiation light along a transverse cross section of the subject by rotating the optical fiber on a longitudinal axis thereof under a condition that the optical fiber is inserted to the subject. The optical tomographic imaging apparatus is characterized in that an optical fiber to be inserted to the subject is optically connected with the optical connector of any one of claims  1  to  6 , and the irradiation light is transmitted through the optical connector and the optical fiber to be inserted to the subject 
       Advantageous Effect of the Invention 
       [0020]    According to the present invention, an optical connector and optical tomographic imaging apparatus which do not generate noise and enable to obtain an excellent tomograpic image without distortion can be provided. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0021]      FIG. 1  is a diagram showing a structure of an optical tomograpic imaging apparatus relating to the present embodiment 
           [0022]      FIG. 2  is a sectional view of an optical connector with which an optical tomograpic imaging apparatus relating to the present embodiment is equipped. 
           [0023]      FIG. 3  is a perspective view showing the first modified example of a capillary tube. 
           [0024]      FIG. 4  is a perspective view showing the second modified example of a capillary tube. 
           [0025]      FIG. 5  is a perspective view showing the third modified example of a capillary tube. 
           [0026]      FIG. 6  is a perspective view showing the fourth modified example of a capillary tube. 
           [0027]      FIG. 7  is a perspective view showing the first example that a connecting section is arranged in a fixed optical fiber. 
           [0028]      FIG. 8  is a sectional view of the fixed optical fiber shown in  FIG. 7 . 
           [0029]      FIG. 9  is a perspective view showing the second example of a fixed optical fiber wherein a connecting section is arranged. 
           [0030]      FIG. 10  is a perspective view showing the first example of a tube member where a fixed optical fiber is arranged. 
           [0031]      FIG. 11  is a sectional view of the tube member shown in  FIG. 10 . 
           [0032]      FIG. 12  is a sectional view of a modified example of an optical connector. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0033]    Hereinafter, embodiments of an optical tomograpic imaging apparatus and an optical connector relating to the present invention will be described referring with appended drawings. 
         [0034]      FIG. 1  is a diagram showing a structure of an optical tomograpic imaging apparatus  10  relating to the present embodiment.  FIG. 2  is a sectional view of an optical connector with which the optical tomograpic imaging apparatus relating to the present embodiment is equipped. 
         [0035]    In  FIG. 1 , light source  11  emits low coherence light  12  in a imaging process. The wavelength of low coherence light  12  is in the range from 0.7 μm to 2.5 μm. As a light source generating low coherence light  12 , a super luminescent diode (SLD) is suitably employed. 
         [0036]    Low coherence light  12  emitted from light source  11  enters coupler  13 . Therefore, light source  11  and coupler  13  are optically connected with an optical fiber, a lens optical system, or a combination of them. 
         [0037]    Coupler  13  divides the emitted low coherence light  12  into two types of light: irradiation light and reference light. The irradiation light which is one of the divided two types of light is guided to probe  17  (see  FIG. 2 ) of irradiation section  16 . As shown in  FIG. 2 , probe  17  houses optical fiber  18  therein. The proximal end of optical fiber  18  (the left-side end in  FIG. 2 ) is connected with optical connector  19  to be rotatable on the longitudinal axis. Optical connector  19  includes a rotator and rotation mechanism  20  (which is not illustrated) for rotating the rotator, to enable to rotate optical fiber  18  on the longitudinal axis based on the drive of rotation mechanism  20 , which will be described later. On the other hand, on the distal end of optical fiber  18 , there is arranged an optical component (for example, a rectangular prism, which will be described later) for deflecting the propagating direction of irradiation light which is transmitted through the optical fiber  18  from its proximal end, to the radial direction of probe  17 . Therefore, irradiation light supplied to probe  17  is transmitted to the distal end of the probe through optical fiber  18 , and is emitted from there to the outside in the radial direction through rectangular prism  65 , and the imaging subject is irradiated with the reference light. The irradiation light moves in the circumference direction corresponding to the rotation of optical fiber  18 . 
         [0038]    The imaging subject is, for example, a blood vessel  21 . In this case, the distal end of optical fiber  18  is inserted into blood vessel  21 , and emits irradiation light through rectangular prism  65  at the distal end to the outside in the radial direction, which is from the inside to the outside of blood vessel  21 . Further, optical fiber  18  rotates on the longitudinal axis. Thereby, the blood vessel and its surrounding tissues are scanned by the irradiation light. Then, light (scattered light) which has been scattered in the inner wall of the blood vessel and inner tissues is taken into rectangular prism  65  on optical fiber  18  and is transmitted to coupler  13 . Herein, the imaging subject is not limited to a blood vessel. 
         [0039]    As shown in  FIG. 1 , the reference light which is the other of two types of light divided by coupler  13  is guided to optical path length adjusting section  23 . Optical path length adjusting section  23  converts, for example, the reference light transmitted from coupler  13  through light guide  24  (for example, an optical fiber) into parallel light by lens optical system  25 . The converted parallel light is reflected by mirror  26  and returns to coupler  13  through optical system  25  and light guide  24 . Mirror  26  is supported by moving mechanism  27  which goes forward and back with respect to lens optical system  25 . By moving mirror  26  based on the drive of moving mechanism  27 , optical path length (optical distance) of the reference light can be changed. 
         [0040]    The scattered light and the reference light which have returned to coupler  13  is combined together, and are sent to interfering light detecting section  28 . In other words, coupler  13  works as a light dividing means and a light combining means. 
         [0041]    Interfering light detecting section  28  acquires intensity information of interfering light of the scattered light and reference light which have been combined and transmits the information to image processing section  29 . Image processing section  29  receives the intensity information of the interfering light from interfering light detecting section  28  and acquires control information from control section  30 . 
         [0042]    Control section  30  caries out synchronizing control for the movement of mirror  26  and the rotation of optical fiber  18 . Concretely, control section  30  drives moving mechanism  27  based on the information of an optical path length generated in control section  30  to move movable mirror  26  forward or backward with respect to optical system  25 , which changes the optical path length of the reference light. Further, control section  30  drives rotation mechanism  20  and rotates optical fiber  18 , to scan a blood vessel along its transverse section with the irradiation light. At that time, control section  30  acquires rotation angle (rotation angle information) of optical fiber  18 , where the rotation angle is outputted from rotating mechanism  20 . Then, control section  30  outputs information of the rotation angle of optical fiber  18  and information of the optical path length of the reference light, to image processing section  29 . Image processing section  29  processes the intensity information of the interfering light based on the information of the optical path length and forms a tomographic image of the blood vessel. The formed tomographic image is displayed by image display section  31 . 
         [0043]    In the process forming the tomographic image, by rotating optical fiber  18  under the condition that mirror  26  is located a certain position, annular sectional image of tissues located at a predetermined distance from the rotation center of the optical fiber can be obtained. Further, by rotating optical fiber  18  under the condition that the optical path length is changed by moving mirror  26  from the above condition, annular sectional image of tissues located at the position which moves to be deeper than the predetermined position can be obtained. As described above, when the irradiation light moves along the circumference direction based on the rotation of optical fiber  18 , while the optical path length of the reference light is changed by the movement of the movable mirror  26 , a tomographic image coveting the entire of the transverse section of the blood vessel can be obtained. Further, when probe  17  rotates plural times under the condition that movable mirror  26  is located at a predetermined position, plural images of the same annular cross section can be obtained and an excellent tomographic image can be obtained by averaging the images. 
         [0044]    Further, the detail of the structure of irradiation section  16  will be described referring with  FIG. 2 . As shown in the figure, irradiation section  16  includes light guide tube  32  for guiding the irradiation light emitted from coupler  13  to optical connector  19 , additionally to probe  17  and optical connector  19 . Light guide tube  32  includes optical fiber  33  and jacket  34  covering the outer circumference of the optical fiber  33 , and the two ends of tube  32  are connected to coupler  13  and optical connector  19 , respectively. 
         [0045]    Optical connector  19  includes housing  35 . As shown in the figure, housing  35  of the present example is composed of a container in a boxed shape. Rotary joint  36  is housed inside housing  35 . Rotary joint  36  includes stator (stationary section)  37  and rotator (rotation section)  38 . Stator  37  includes annular tube section  39  and end wall  40  for closing the proximal end (the left side of the figure) of annular tube section  39  which are formed in one body. Stator is fixed on housing  35  under the condition that the center axis of annular tube section  39  agrees with the base axis (rotation axis)  41 . 
         [0046]    Rotator  32  is composed of cylinder  42  and is supported by bearing  43  arranged on housing  35  so as to be rotatable on base axis  41  under the condition that the center axis of cylinder  42  agrees with base axis  41 . Cylinder  42  is connected with motor  44  of rotation mechanism  20  arranged on housing  35  so as to be driven, and is configured to rotate on base axis  41  based on the rotation of motor  44 . As for stator  37  and rotator  38 , the proximal end of rotator  38  (the left side of the figure) is fitted into inner step section  45  formed on the distal end (the right side of the figure) of stationary annular tube section  39 , and a space between stator  37  and rotator  38  is sealed with proper sealing  46 . In the example, seal  46  is fixed on stator  37 . Seal  46  is preferably formed by oil seal. However, seal  46  is not limited to the oil seal and can be other seals such as metal seal. Alternatively, seal  46  is preferably formed of a material with strength and elasticity such as fluororubber. 
         [0047]    At the center of rotator  38  composed of cylinder  42 , through hole  47  is formed along base axis  41 , and capillary tube  48  is fixed therein. As it is illustrated, capillary tube  48  has the almost same outer diameter as the inner diameter of through hole  47 . The distal end of the capillary tube at the right hand side of the figure is inserted into the proximal end of through hole  47  to be fixed, and the proximal end of the capillary tube at the left hand side of the figure protrudes into chamber  49  which is an interior space of stationary annular tube section  39 . 
         [0048]    Capillary tube  48  includes cavity (lumen)  50  with a small diameter penetrating capillary tube  48  along base axis  41 . The inner diameter of cavity  50  is almost same as the outer diameters of the dads of the optical fibers to be used in the present example. Capillary tube  48  further includes connecting section  51  with a small diameter which connects cavity  50  and chamber  49  of stationary annular tube section  39 . In the example, connecting section  51  is formed as a hole with small diameter. 
         [0049]    The size of capillary tube  48  is 2 mm in outer diameter and 20 mm in length. The size of cavity  50  depends on conditions for use. Concretely, optical fibers are separately inserted into the both sides of cavity  50  of capillary tube  48 , which will be described below, and these optical fibers are optically connected at their opposing end sections. Therefore, the inner diameter of cavity  50  is set to be the same as or slightly lager than the outer diameters of the clads of the optical fibers to be used. For example, when the diameter (which is the value including tolerance) of the dads of the optical fibers is 125 to 126 μm, the inner diameter of cavity  50  is set to be 126 μm. Accordingly, when the tolerance of the outer diameters of the dads is zero, the opposing two optical fibers can shift by at most  1  pm in cavity  50 . However, the diameter of the cores of the optical fibers are about 10 μm generally, and the shift amount of the axes is as small as about 10% of the core diameter. Therefore, two optical fibers can be connected in an excellent condition. 
         [0050]    Capillary tube  48  is desired to have the feature that optical fibers can be easily inserted into cavity  50 , to enable to be processed with high accuracy (to enable to ensure a desired straightness for the cavity and to obtain the desired concentricity between the cavity and the outer circumference surface), and to have a desired toughness, an excellent anti-impact property, and coefficient of thermal expansion which is close to that of the optical fibers (in order to prevent the relative movement of the capillary tube and the optical fiber). Therefore, capillary tube  48  is preferably formed of sintered ceramic. In order to minimize the insertion resistance of the optical fibers, the capillary tube is preferably formed of glass. 
         [0051]    Optical fiber  33  of light guide tube  32  is connected with the capillary tube  48 . Concretely, the distal end of light guide tube  32  disposed at the side of the proximal end penetrates wall  52  of housing  35  along base axis  41 , and is fixed on wall  52  with an unillustrated fixing means (for example, adhesive). Inside housing  35 , a coat of light guide tube  32  is removed and optical fiber  33  is exposed. This optical fiber  33  penetrates end wall  40  of stator  37 , and enters cavity  50  of capillary tube  48  through chamber  49 . The distal end of optical fiber  33  is positioned at the side of the proximal end of connecting section  51 . 
         [0052]    The proximal end of optical fiber  53  is inserted in cavity (lumen)  50  of capillary tube  48 , from the distal end of the cavity. The proximal end of optical fiber  53  is located at the side of the distal end of the connecting section  51 . Therefore, the distal end of optical fiber  33  and the proximal end of optical fiber  53  face across connecting section  51 , and gap  54  is formed between them. For example, the length of gap  54  in the direction of the rotation axis is adjusted within about 0.1 mm. Thereby, optical fibers  33  and  53  are concentrically arranged along base axis  41  and are optically connected with each other. The distal end of optical fiber  53  is connected with adapter  55  which is fixed to the opening section at the distal end of through hole  47  through connector  56 . Then, optical fiber  53  is fixed to capillary tube  48  with adhesive arranged on the distal end of capillary tube  48 . At the same time, capillary tube  48  is fixed to rotator  38  with the adhesive  57 . 
         [0053]    Chamber  49  which is tightly sealed by combining stator  37  and rotator  38 , is filled with matching material  58 . Matching material  58  is preferably a material which can transmit irradiation light and scattered light without attenuating them as much as possible. For matching material  58 , liquid or fluid (gel material) with a refractive index being almost the same as those of the cores of the optical fibers  33  and  53  is used. Thereby, Fresnel reflection on the core ends of optical fibers  33  and  53  is reduced and attenuation of propagating light is controlled. The filling process of matching material  58  can be carried out through a filling hole (which is not illustrated) arranged on annular tube section  39  or end wall  40  of stator  37 . Matching material  58  which has filled up chamber  49  enters gap  54  from connecting section  51  and exists between opposing optical fibers  33  and  53 . 
         [0054]    Accordingly, transparent matching material  58  is stored in chamber  49  which is an exterior space of capillary tube  48 , gap  49 , and connecting section  51 . 
         [0055]    Rotation mechanism  20  for rotating rotator  38  includes motor  44 . As described above, motor  44  is electrically connected with control section  30  and rotates based on the rotation control signal outputted from control section  30 . Therefore, gear  60  is fixed to rotation shaft  59  of motor  44 . Gear  60  meshes with another gear  61 . Gear  61  further meshes with gear  62  formed on the outer circumference surface of cylinder  42  as a rotator. Accordingly, rotator  38  rotates corresponding to a drive operation of motor  44 . The means to transmit the rotation of motor  44  to rotator  38  is not limited to a gear mechanism, and may be a structure that a belt and pulley are combined. Further, the type of motor  44  is not limited, but a stepping motor is preferably used for motor  44  in order to synchronize the rotation of rotator  38  and the movement of mirror  26  as described above. 
         [0056]    Probe  17  to be connected with rotary joint  36  which is structured as above, includes optical fiber  18  as described above. Connector  63  is connected with the proximal end of optical fiber  18 . Connector  63  can be connected with adaptor  55  of rotary joint  36  such that the connector can be attached to or detached from the adapter  55  freely, and optically connects optical fiber  18  and optical fiber  53  under the condition that the connector is connected with adaptor  55 . Therefore, for connectors  56  and  63  and adapter  55 , a FC connector and FC adapter, or a SC connector and SC adapter which are suitable to connection of optical fibers are preferably used. 
         [0057]    On the distal end of optical fiber  18 , distributed (gradient) index lens (hereinafter, referred as “lens”)  64  and rectangular prism  65  for deflecting a propagating direction of the irradiation light emitted from lens  64  to the radial direction of probe  17  are fixed. A mirror section formed of a metal film for reflecting the irradiation light is formed on the sloped surface of the rectangular prism  65 . Optical fiber  18  is externally wrapped with torque transmitting sleeve  66  for transmitting the rotation of rotator  38  to lens  64  at the distal end. Sleeve  66  has a flexibility which is required to ensure a free movement of the optical fibers. Therefore, sleeve  66  is preferably formed of a torque wire or a spring wire each in a tube shape formed by spirally winding thin wires. 
         [0058]    Almost all of the optical fiber  18  protruding from housing  35  is covered with sheath  67 . Sheath  67  is formed of a transparent flexible material (for example, polytetrafluoroethylene). The distal end of the sheath extends past rectangular prism  65  and an opening of the distal end is sealed with cap  68 . Further, sealing member  69  formed of a rubber ring is arranged between a portion of sleeve  66  where sleeve  66  is connected with lens  64  or an exposed outer circumference surface of sleeve  66 , and a sheath section facing it. Space  70  formed between cap  68  and sealing member  69  is filled with matching material  71  having a refractive index being almost the same as or close to the refractive index of rectangular prism  65 . Thereby, Fresnel reflection is reduced on the outgoing surface and incident surface of prism  65 , and attenuation of the propagating light is controlled. The proximal end of sheath  67  is located at a position closer to the distal end side than the proximal end of optical fiber  18 , and ring-shaped clamp  72  is fixed thereon. 
         [0059]    Probe  17  formed as above is inserted into the through hole formed on wall  52  of housing  3  as it is illustrated. Connector  63  is connected to adaptor  55 , and clamp  72  is fixed around through hole  47 , and the probe is connected to optical connector  19 . In order to carry out this operation easily, a part of housing  53  is formed as flap  73  which can be opened and closed, and the above connecting operation is carried out with flap  73  being opened. It is naturally understood that probe  17  can be detached and be replaced with another component by separating connector  63  from adaptor  55  and bringing clamp  72  from housing  35 . 
         [0060]    The movement of irradiation section  16  structured as described above will be described. In the above tomographic imaging process, motor  44  is driven based on the signal outputted from control section  30  and rotates rotator  38 . Due to the rotation, optical fiber  53  which is fixed inside rotator  38  and optical fiber  18  which is connected to capillary tube  48  and rotator  38  and is located inside probe  17  rotate on base axis  41 . The irradiation light which is divided with coupler  13  passes optical fiber  33  covered with light guide tube  32 , optical fiber  53  fixed inside rotator  38 , and optical fiber  18  housed in probe  17 , and is transmitted to lens  64  and rectangular prism  65 . Then, the light is reflected by a metal-film mirror formed on the sloped surface of rectangular prism  65  and is emitted outside in the radial direction of probe  17  and is projected outside in the radial direction through matching material  71  and transparent sheath  67 . The irradiation light which has been projected is moved in the circumference direction with the rotation of optical fiber  18 . 
         [0061]    For example, in the case of the above-described tomographic imaging of a blood vessel, the projected irradiation light is scattered on the inner wall and inner tissues of blood vessel  21 . A part of the scattered light enters an incident surface of rectangular prism  65  through sheath  67  and matching material  71 , passes through lens  64 , rotating optical fibers  18  and  53  and fixed optical fiber  33 , and returns to coupler  13 . 
         [0062]    Under the rotation of rotator  38 , the distance of fixed optical fiber  38  and rotating optical fiber  53  changes because of vibration caused by the rotation. Even when the change amount of the distance is very small (for example, 1 mm), the inner diameter of cavity  50  is very small (125 to 126 μm) and a change in pressure inside gap  54  becomes extremely large under the condition that the matching material is stored only in gap  54 . However, as described above, gap  54  is connected with exterior chamber  49  through connecting section  51 , which allows that matching material  58  in chamber  49  goes in and out gap  54  corresponding to the pressure change in gap  54  and the pressure in gap  54  is maintained to be almost constant. 
         [0063]    In other words, by providing a structure wherein transparent matching material  58  is stored in chamber  49  as an exterior space of capillary tube  48 , gap  54  and connecting section  51 , large pressure change is not caused in the matching liquid in the gap  54  even when the gap of opposing optical fibers  33  and  53  changes because of the rotation. It solves the problem that negative pressure is applied to the matching material  58  filling gap  54  and changes in density and refractive index and generation of bubbles are caused in the matching material  58  which fills gap  54 . Further, it enables to provide an optical connector and optical tomographic imaging apparatus which generates less noise and enables to obtain an excellent tomographic image without distortion. 
         [0064]    The above-described optical tomographic imaging apparatus and optical connector are not limited to the above embodiment and can be modified in various embodiments. 
         [0065]    For example, in the above embodiment, connecting section  51  is formed as a hole extending from cavity  50  toward the outside in the radial direction in a one-way manner. However, it may be formed as plural holes  73  extending in two or more directions (for example, in opposite directions) toward the outside in the radial direction, as shown in  FIG. 3 . 
         [0066]    Connecting section  51  is not needed to be a hole, and can be groove  74  which extends across cavity  50  as shown in  FIG. 4 . 
         [0067]    Connecting section  51  is not needed to be a hole and groove extending in the radial direction, and can be connecting groove  75  forming a straight line or a spiral along the inner surface of cavity  50  as shown in  FIG. 5 . 
         [0068]    In order to eliminate the process to form a hole or groove on capillary tube  48 , for example, capillary tube  48  may be formed by mesh tube  76  which looks like a stent as a medical device, as shown in  FIG. 6 . In this case, a matching material freely goes in and out gap  54  of fixed optical fiber  33  and rotation optical fiber  53  through mesh openings  77 , to avoid a change in properties of the matching material and generation of bubbles. 
         [0069]    In place of the above method, as shown in  FIGS. 7 ,  8  and  9 , groove  78  or notch  79  may be formed in the longitudinal axis direction on the outer circumference surface of the clad of optical fiber  33  located in chamber  49  housing matching material  58 , to connecting chamber  49  and gap  49  through groove  78  or notch  79 . 
         [0070]    In place of forming the groove and notch, there can be provided a astructure as shown in  FIGS. 10 and 11 . In the structure, tube member  80  is arranged at at least an area between the outer circumference of optical fiber  33  located in chamber  49  and capillary tube  48 . Groove  81  or a notch (which is not illustrated) is formed on tube member  80  along the longitudinal direction to connect chamber  49  and gap  54 . In the embodiment, tube member  80  may be fixed on optical fiber  33  or is arranged so as to freely rotate with respect to optical fiber  33 . 
         [0071]    Further, in the above embodiment, the capillary tube is fixed on rotator  38 , but may be fixed on housing (stationary section) as shown in  FIG. 12 . In this case, as shown in the figure, optical fiber  53  arranged between optical fiber  33  at the proximal end and optical fiber  18  at the distal end is fixed on rotator  38  and its proximal end is inserted into the distal end of cavity  50 . Then, gap  54  formed between optical fibers  33  and  53  is connected with chamber  49  through connecting section  51 , and matching material  58  goes in and out gap  54  corresponding to the pressure change of gap  54 , to maintain the pressure in the gap to be constant. 
         [0072]    In the above, plural modified examples are described separately. These plural modified examples can be arbitrarily combined with the other and the present invention includes such the modified examples. 
         [0073]    The above-described optical tomograhphic imaging apparatus relating to the above embodiments is categorized in a so-called time-domain OCT, but the above various embodiments can be applied to another methods (spectrum-domain OCT, swept-domain OCT and Fourier-domain OCT) of optical tomographic imaging apparatuses. 
       REFERENCE SIGNS LIST 
       [0074]      10  Optical tomographic imaging apparatus 
         [0075]      11  Light source 
         [0076]      13  Coupler (Optical splitter, Optical combiner) 
         [0077]      16  Irradiation section 
         [0078]      17  Probe 
         [0079]      18 ,  33 ,  53  Optical fiber 
         [0080]      19  Optical connector 
         [0081]      21  Blood vessel (Imaging subject) 
         [0082]      23  Optical path length adjusting section 
         [0083]      24  Light guide 
         [0084]      25  Lens optical system 
         [0085]      26  Mirror 
         [0086]      28  Interfering light detecting section 
         [0087]      29  Image processing section 
         [0088]      30  Control section 
         [0089]      31  Image display section 
         [0090]      32  Light guide tube 
         [0091]      34  Jacket 
         [0092]      35  Housing 
         [0093]      36  Rotary joint 
         [0094]      37  Stator 
         [0095]      38  Rotator 
         [0096]      39  Annular tube section 
         [0097]      41  Base axis 
         [0098]      42  Cylinder 
         [0099]      44  Motor 
         [0100]      45  Step section 
         [0101]      46  Seal 
         [0102]      47  Through hole 
         [0103]      48  Capillary tube 
         [0104]      49  Chamber 
         [0105]      50  Cavity (Lumen) 
         [0106]      51  Connecting section 
         [0107]      52  Wall 
         [0108]      54  Gap 
         [0109]      55  Adopter 
         [0110]      56  Connector 
         [0111]      57  Adhesive 
         [0112]      58 ,  71  Matching material 
         [0113]      59  Motor rotating shaft 
         [0114]      63  Connector 
         [0115]      64  Distributed (Gradient) index lens 
         [0116]      65  Rectangular prism 
         [0117]      66  Sleeve 
         [0118]      67  Sheath 
         [0119]      68  Cap 
         [0120]      69  Sealing member 
         [0121]      70  Space 
         [0122]      72  Clamp 
         [0123]      73  Hole 
         [0124]      74 ,  78 ,  81  Grooves 
         [0125]      75  Connecting groove 
         [0126]      76  Mesh tube 
         [0127]      77  Mesh opening 
         [0128]      79  Notch 
         [0129]      80  Tube member