Abstract:
A scanning endoscope comprising a light transmitter, an actuator, and a force transmitter, is provided. The light transmitter emits a beam of the light exiting the first emission end. The light transmitter is flexible. A longitudinal direction of the light transmitter is a first direction. The actuator is mounted near the first emission end. The actuator bends the light transmitter in a second direction by pushing a side of the light transmitter in the second direction. The second direction is perpendicular to the first direction. A force transmitter is oriented lengthwise in the first direction. The force transmitter is elastic. The force transmitter is positioned between the light transmitter and the actuator. The force transmitter exerts a pushing force supplied by the actuator on the side of the light transmitter while the force transmitter is deformed elastically toward the first direction.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to simplifying a manufacturing method and improving the accuracy of manufacturing an actuator that moves a fiber of a scanning endoscope. 
     2. Description of the Related Art 
     U.S. Pat. No. 6,294,775 discloses a scanning endoscope, which photographs and/or films an optical image of an observation area by scanning the observation area with light shined on a minute point in the area and successively capturing reflected light at the illuminated points. In a general scanning endoscope, light for illumination is transmitted through an optical fiber from a stationary incident end to a movable emission end and a scanning operation is carried out by successively moving the emission end of the optical fiber. 
     The structure of the emission end of an optical fiber in a general scanning endoscope is explained using  FIG. 26 . As shown in  FIG. 26 , the actuator  54 ′ is mounted near an emission end of an illumination fiber  53 ′. The fiber actuator  54 ′ comprises a bending block  54 ′ b  and a support block  54 ′ s.    
     The bending block  54 ′ b  is shaped cylindrically. The illumination fiber  53 ′ is inserted through the cylindrical bending block  54 ′ b . The illumination fiber  53 ′ is supported at the forward end of the bending block  54 ′ b  by the supporting block  54 &#39;s. 
     The supporting block  54 ′ s  is shaped as a right circular cone so that the angle between a generatrix line and the base is 45 degrees. By shaping the supporting block  54 ′ s  in this manner, the illumination fiber  53 ′ can be repeatedly bent without breaking by a bending motion of the bending block  54 ′ b  that is transmitted through the supporting block  54 ′ s.    
     In order to form the supporting block  54 ′ s  in the above-mentioned shape, when the illumination fiber  53 ′ is inserted through the bending block  54 ′ b , an adhesive is applied to the forward end of the bending block  54 ′ b , and before it solidifies an operator transforms the adhesive to a right circular cone by vibrating the illumination fiber  53 ′ along the axial direction of the bending block  54 ′ b . The supporting block  54 ′ s  is formed by the transformed adhesive solidifying as such a shape. 
     In the above manufacturing method it is difficult to adjust the length of the illumination fiber  53 ′ that protrudes from the bending block  54 ′ b . It is also difficult to accurately shape the supporting block  54 ′ s  in the form of a right circular cone by the above-manufacturing method. As a result, increasing the yield of manufactured parts within required tolerance levels is difficult. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to improve a manufacturing yield by making a bending block to support the illumination fiber so that the illumination fiber can sufficiently withstand the movements required of it during scanning. 
     According to the present invention, a scanning endoscope, comprising a light transmitter, an actuator, and a force transmitter, is provided. The light transmitter transmits light received at a first incident end to a first emission end. The light transmitter emits a beam of the light exiting the first emission end. The light transmitter is flexible. A longitudinal direction of the light transmitter is a first direction. The actuator is mounted near the first emission end. The actuator bends the light transmitter in a second direction by pushing a side of the light transmitter in the second direction. The second direction is perpendicular to the first direction. A force transmitter is oriented lengthwise in the first direction. The force transmitter is elastic. The force transmitter is positioned between the light transmitter and the actuator. The force transmitter exerts a pushing force supplied by the actuator on the side of the light transmitter while the force transmitter is deformed elastically toward the first direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and advantages of the present invention will be better understood from the following description, with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic illustration of a scanning endoscope apparatus comprising a scanning endoscope of the first to seventh embodiments of the present invention; 
         FIG. 2  is a block diagram schematically showing the internal structure of the scanning endoscope processor; 
         FIG. 3  is a block diagram schematically showing the internal structure of the scanning endoscope of the first embodiment; 
         FIG. 4  is a cross-sectional view along the axial direction of the hollow tube schematically showing the structure of the fiber actuator of the first embodiment; 
         FIG. 5  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of the fiber actuator of the first embodiment; 
         FIG. 6  is a front view of the fiber actuator in the first embodiment as seen from the emission end of the illumination fiber; 
         FIG. 7  is a perspective view of the fiber actuator in the first embodiment; 
         FIG. 8  is a cross-sectional view along the axial direction of the bending block illustrating the deformation of the supporting block at the moment when bending begins; 
         FIG. 9  is a cross-sectional view of a plane that includes a center line of the illumination fiber to illustrate the restoring force applied to the illumination fiber by the supporting block when the supporting block deforms elastically; 
         FIG. 10  is a cross-sectional view of a plane that includes a center line of the illumination fiber to illustrate the force applied to the illumination fiber by the supporting block that is assumed to be made of a solid material; 
         FIG. 11  is a graph illustrating the changing position of the emission end in the second and third directions; 
         FIG. 12  illustrates a spiral course along which the emission end of the illumination fiber is moved by the fiber actuator; 
         FIG. 13  illustrates the light emitted from the lens; 
         FIG. 14  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of the fiber actuator of the second embodiment; 
         FIG. 15  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of the fiber actuator of the third embodiment; 
         FIG. 16  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of the fiber actuator of the fourth embodiment; 
         FIG. 17  is a conceptual view of the intensities of the dispersed restoring forces applied to the side of the illumination fiber in the first embodiment; 
         FIG. 18  is a conceptual view of the intensities of the dispersed restoring forces applied to the side of the illumination fiber in the fourth embodiment; 
         FIG. 19  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of the fiber actuator of the fifth embodiment; 
         FIG. 20  is a front view of the fiber actuator in the fifth embodiment as seen from the emission end of the illumination fiber; 
         FIG. 21  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of the fiber actuator of the sixth embodiment; 
         FIG. 22  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of the fiber actuator of the seventh embodiment; 
         FIG. 23  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of the fiber actuator with the center of mass shifted in the opposite direction of the second embodiment; 
         FIG. 24  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of the fiber actuator with the center of mass shifted in the opposite direction of the third embodiment; 
         FIG. 25  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of the fiber actuator with the center of mass shifted in the opposite direction of the sixth embodiment; and 
         FIG. 26  is a cross-sectional view along the axial direction of the bending block schematically showing the structure of a fiber actuator in a prior art. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is described below with reference to the embodiment shown in the drawings. 
     In  FIG. 1 , the scanning endoscope apparatus  10  comprises a scanning endoscope processor  20 , a scanning endoscope  50 , and a monitor  11 . The scanning endoscope processor  20  is connected to the scanning endoscope  50  and the monitor  11 . 
     Hereinafter, an emission end of an illumination fiber (not depicted in  FIG. 1 ) and incident ends of image fibers (not depicted in  FIG. 1 ) are ends mounted in the distal end of the insertion tube  51  of the scanning endoscope  50 . In addition, an incident end of the illumination fiber (first incident end) and emission ends of the image fibers are ends mounted in a connector  52  that connects to the scanning endoscope processor  20 . 
     The scanning endoscope processor  20  provides light that is shined on an observation area (see “OA” in  FIG. 1 ). The light emitted from the scanning endoscope processor  20  is transmitted to the distal end of the insertion tube  51  through the illumination fiber (light transmitter), and is directed towards one point in the observation area. Light reflected from the illuminated point is transmitted from the distal end of the insertion tube  51  to the scanning endoscope processor  20 . 
     The direction of the emission end of the illumination fiber (first emission end) is changed by a fiber actuator (not depicted in  FIG. 1 ). By changing the direction, the observation area is scanned with the light emitted from the illumination fiber. The fiber actuator is controlled by the scanning endoscope processor  20 . 
     The scanning endoscope processor  20  receives reflected light that is scattered at the illuminated point, and generates a pixel signal according to the amount of received light. One frame of an image signal is generated by generating pixel signals corresponding to the illuminated points dispersed throughout the observation area. The generated image signal is transmitted to the monitor  11 , where an image corresponding to the received image signal is displayed. 
     As shown in  FIG. 2 , the scanning endoscope processor  20  comprises a light-source unit  30 , a light-capturing unit  21 , a scanning driver  22 , an image-processing circuit  23 , a timing controller  24 , a system controller  25 , and other components. 
     The light-source unit  30  comprises red, green, and blue lasers (not depicted) that emit red, green, and blue laser beams, respectively. The red, green, and blue laser beams are mixed into white light, which is emitted from the light-source unit  30 . 
     The white light emitted from the light-source unit  30  is supplied to the illumination fiber  53 . The scanning driver  22  controls the fiber actuator  54  so that the movements of the emission end of the illumination fiber  53  follow a predetermined course. 
     The reflected light at the illuminated point within the observation area is transmitted to the scanning endoscope processor  20  by the image fibers  55  mounted in the scanning endoscope  50 . The transmitted light is made incident on the light-capturing unit  21 . 
     The light-capturing unit  21  generates a pixel signal according to the amount of the transmitted light. The pixel signal is transmitted to the image-processing circuit  23 , which stores the received pixel signal in the image memory  26 . Once pixel signals corresponding to the illuminated points dispersed throughout the observation area have been stored, the image-processing circuit  23  carries out predetermined image processing on the pixel signals, and then one frame of the image signal is transmitted to the monitor  11  via the encoder  27 . 
     By connecting the scanning endoscope  50  to the scanning endoscope processor  20 , optical connections are made between the light-source unit  30  and the illumination fiber  53  mounted in the scanning endoscope  50 , and between the light-capturing unit  21  and the image fibers  55 . In addition, by connecting the scanning endoscope  50  to the scanning endoscope processor  20 , the fiber actuator  54  mounted in the scanning endoscope  50  is electrically connected to the scanning driver  22 . 
     The timing for carrying out the operations of the light-source unit  30 , the light-capturing unit  21 , the scanning driver  22 , the image-processing circuit  23 , and the encoder  27  is controlled by the timing controller  24 . In addition, the timing controller  24  and other components of the endoscope apparatus  10  are controlled by the system controller  25 . A user can input some commands to the input block  28 , which comprises a front panel (not depicted) and other mechanisms. 
     Next, the structure of the scanning endoscope  50  is explained. As shown in  FIG. 3 , the scanning endoscope  50  comprises the illumination fiber  53 , the fiber actuator  54 , the image fibers  55 , a lens  56  and other components. 
     The illumination fiber  53  and the image fibers  55  are arranged inside the scanning endoscope  50  from the connector  52  to the distal end of the insertion tube  51 . As described above, a laser beam of the white light emitted by the light-source unit  30  is incident on the incident end of the illumination fiber  53 . The incident white light is transmitted to the emission end of the illumination fiber  53 . 
     A solid hollow tube  57  is mounted at the distal end of the insertion tube  51  (see  FIG. 4 ). The hollow tube  57  is positioned so that the axial direction of the distal end of the insertion tube  51  is parallel to a first direction that is an axial direction of the hollow tube  57 . 
     The illumination fiber  53  is supported inside the hollow tube  57  by the fiber actuator  54 . The illumination fiber  53  is positioned in the hollow tube  57  so that the axial direction of the hollow tube  57  is parallel to a longitudinal direction of the insertion tube  51  that is not moved by the fiber actuator  54 . 
     The fiber actuator  54  comprises a supporting block  54   s  (force transmitter) and a bending block  54   b  (actuator). As shown in  FIG. 5 , the bending block  54   b  is shaped cylindrically. The supporting block  54   s  is a metal coil spring with dimensions so that the outside and inside diameters of the coil spring are substantially equal to the inside diameter of the cylindrical bending block  54   b  and the outside diameter of the illumination fiber  53 , respectively. 
     The illumination fiber  53  is inserted through the hollow interior of the coil-shaped supporting block  54   s . The illumination fiber  53  is supported by the supporting block  54   s  as the emission end of the illumination fiber  53  protrudes from the supporting block  54   s.    
     The supporting block  54   s  is inserted into the cylindrical bending block  54   b . The position of the supporting block  54   s  is fixed in the bending block  54   b  so that the end of the supporting block  54   s  nearest to the emission end of the illumination fiber  53  protrudes from the bending block  54   b . Accordingly, the supporting block  54   s  is positioned between the bending block  54   b  and the illumination fiber  53  in the radial direction. 
     As shown in  FIG. 6 , first and second bending elements  54   b   1  and  54   b   2  are fixed on the bending block  54   b . The first and second bending elements  54   b   1  and  54   b   2  are pairs of two piezoelectric elements. In addition, the first and second bending elements  54   b   1  and  54   b   2  expand and contract along the axis direction of the cylindrical bending block  54   b  (i.e., the first direction) on the basis of a fiber driving signal transmitted from the scanning driver  22 . 
     Two piezoelectric elements that constitute the first bending element  54   b   1  are fixed on the outside surface of the cylindrical bending block  54   b  so that the axis of the cylindrical bending block  54   b  is between the piezoelectric elements and so that the piezoelectric elements are linearly arranged in a second direction that is perpendicular to the first direction. In addition, two piezoelectric elements that constitute the second bending element  54   b   2  are fixed on the outside surface of the cylindrical bending block  54   b  at a location that is 90 degrees circumferentially from the first bending element  54   b   1  around the axis of the cylindrical bending block  54   b.    
     As shown in  FIG. 7 , the bending block  54   b  bends along the second direction by expanding one of the piezoelectric elements that constitute the first bending element  54   b   1  and contracting the other at the same time. 
     In addition, the bending block  54   b  bends along a third direction by expanding one of the piezoelectric elements that constitute the second bending element  54   b   2  and contracting the other at the same time. The piezoelectric elements constituting the second bending element  54   b   2  are linearly arranged in the third direction. 
     The illumination fiber  53  is flexible. The side of illumination fiber  53  is pushed along the second and/or third directions by the bending block  54   b  via the supporting block  54   s  (force transmitter), and the illumination fiber  53  bends toward the second and/or third directions, which are perpendicular to the longitudinal direction of the illumination fiber  53 . The emission end of the illumination fiber  53  is moved by bending the illumination fiber  53 . 
     The actions of the bending block  54   b  pushing the side of the illumination fiber  53  is explained below. As shown in  FIG. 8 , when the bending block  54   b  bends in the second direction, a recessed section  54   s   1  of the supporting block  54   s  that is positioned entirely within (does not protrude from) the bending block  54   b  is pushed in the second direction. 
     The protruding section  54   s   2  of the supporting block  54   s  does not bend in the second direction because the pushing force exerted by the bending block  54   b  is not applied directly to the protruding section  54   s   2  of the supporting block  54   s . Accordingly, the protruding section  54   s   2  deforms elastically and bends in the opposite direction of the second direction. Afterward, a restoring force is applied to return the protruding section  54   s   2  toward the second direction. 
     The outside of the illumination fiber  53  is pushed by the restoring force applied to the protruding section  54   s   2 , which causes the illumination fiber  53  to bend along the second direction. The restoring force (see “e” in  FIG. 9 ) is distributed across the entire protruding section  54   s   2  and exerted on the illumination fiber  53 . 
     If the supporting block  54 ′ s  is made of solid material, as shown in  FIG. 10 , a large force (see “E” in  FIG. 10 ) is exerted on the end of the supporting block  54 ′ s  where the supporting block  54 ′ s  makes contact with the illumination fiber  53 . The large force applied to a narrow section of the illumination fiber  53  may cause damage to the illumination fiber  53 . On the other hand, in this embodiment damage of the illumination fiber  53  can be decreased by applying the restoring force distributed across the entire protruding section  54   s   2 . 
     As shown in  FIG. 11 , the emission end of the illumination fiber  53  is moved so that the emission end vibrates along the second and third directions at amplitudes that are repetitively increased and decreased. The frequencies of the vibration along the second and third directions are adjusted to be equal. In addition, the period to increase and to decrease the amplitudes of the vibration along the second and third directions are synchronized. Further, phases of the vibration along the second and third directions are shifted by 90 degrees. 
     By vibrating the emission end of the illumination fiber  53  along the second and third directions as described above, the emission end traces the spiral course shown in  FIG. 12 , and the observation area is scanned with the white laser beam. 
     The position of the emission end of the illumination fiber  53  when the illumination fiber  53  is not bent is defined as a standard point. While the emission end is vibrated with increasing amplitude starting from the standard point (see “scanning period” in  FIG. 11 ), illumination of the observation area with the white laser beam and generation of pixel signals are carried out. 
     In addition, when the amplitude reaches a maximum among the predetermined range, one scanning operation for producing one image terminates. After termination of a scanning operation, the emission end of the illumination fiber  53  is returned to the standard point by vibrating the emission end with progressively decreasing amplitudes (see “braking period” in  FIG. 11 ). When the emission end is returned to the standard point, it is the beginning of a scanning operation for generating another image. 
     The lens  56  is mounted in the emission direction in which light is emitted from the emission end that is positioned at the standard point (see  FIG. 4 ). The lens  56  is fixed in the scanning endoscope  50  so that an optical axis of the lens  56  is parallel to the emission direction in which light is emitted from the emission end that is positioned at the standard point. 
     The white laser beam emitted from the illumination fiber  53  passes through the lens  56  before reaching an individual point within the observation area (see  FIG. 13 ). The reflected light is scattered at that point. The scattered and reflected light is incident on the incident ends of the image fibers  55 . 
     A plurality of the image fibers  55  are mounted in the scanning endoscope  50 . The incident ends of the image fibers  55  are arranged around the lens  56  (see  FIG. 13 ). The light that is scattered and reflected from the point in the observation area is incident on all the image fibers  55 . 
     The reflected light incident on the incident ends of the image fibers  55  is transmitted to the emission ends of the image fibers  55 . As described above, the emission ends of the image fibers  55  are optically connected to the light-capturing unit  21 . The reflected light transmitted to the emission ends is incident on the light-capturing unit  21 . 
     The light-capturing unit  21  detects the amounts of red, green, and blue light components in the reflected light, and generates pixel signals according to the amounts of the light components. The pixel signals are transmitted to the image-processing circuit  23 . 
     The image-processing circuit  23  estimates the points where the white laser beam is shined on the basis of signals used to control the scanning driver  22 . In addition, the image-processing circuit  23  stores the received pixel signals at the address of the image memory  26  that corresponds to the estimated points. 
     As described above, the observation area is scanned with the white laser beam, pixel signals are generated on the basis of the reflected light at the respective points illuminated with the white laser beam, and the generated pixel signals are stored at the addresses corresponding to the points. The image signal corresponding to the observation area comprises the pixel signals corresponding to the points from the scan-start point to the scan-end point. As described above, the image-processing circuit  23  carries out predetermined image processing on the image signal. After undergoing predetermined image processing, the image signal is transmitted to the monitor  11 . 
     In the above first embodiment, it is easy to accurately manufacture a scanning endoscope with illumination fiber  53  that can sufficiently withstand the pushing force exerted by the bending block  54   b.    
     In addition, in the above first embodiment, even if the fiber actuator  54  is exposed to a high ambient temperature, the fiber actuator  54  can still carry out a stable scanning operation, as explained below. 
     Although most of the light emitted from the emission end of the illumination fiber  53  passes through the lens  56 , a portion of the light is reflected by the lens  56  onto the supporting block  54   s . The supporting block  54   s  will generate heat due to the reflected light striking it. Accordingly, unless the supporting block  54   s  can maintain its shape without deformation when exposed to high ambient temperatures, the supporting block  54   s  will become distorted and carrying out a stable scanning operation will not be possible. However, in the above first embodiment, the supporting block  54   s  is made of metal, which provides sufficient protection against deformation caused by high ambient temperatures. Accordingly, even if the fiber actuator  54  is exposed to high ambient temperatures, the fiber actuator  54  can stably move the emission end of the illumination fiber  53  and a stable scanning operation can be carried out. 
     Next, a scanning endoscope of the second embodiment is explained. The primary difference between the second embodiment and the first embodiment is the shape of the supporting block. The second embodiment is explained mainly with reference to the structures that differ from those of the first embodiment. Here, the same index numbers are used for the structures that correspond to those of the first embodiment. 
     As shown in  FIG. 14 , the supporting block  540   s  is a metal coil spring configured so that the outside and inside diameters of the coil spring are substantially equal to the inside diameter of the cylindrical bending block  54   b  and the outside diameter of the illumination fiber  53 , respectively, as in the first embodiment. However, the coil pitch of the protruding section  540   s   2  is not constant, unlike the first embodiment, and is relatively longer at the end nearest to the emission end of the illumination fiber  53  compared to the other end. 
     Owing to the above shape of the supporting block  540   s , the mass per a predetermined length along the axial direction of the coil is lower at the section with the longer respective coil pitch (see “L 1 ” in  FIG. 14 ) than the mass of the section with the shorter coil pitch (see “L 2 ” in  FIG. 14 ). Accordingly, the center of mass for the combination of the illumination fiber  53  and the protruding section  540   s   2  is relatively closer to the bending block  54   b . Owing to the shift in the center of mass, the resonant frequency of the section of the illumination fiber  53  that vibrates with the protruding section  540   s   2  is increased with the adjustment. 
     In the above second embodiment, the same effect can be achieved as in the first embodiment. 
     In addition, the resonant frequency of the section of the illumination fiber  53  that vibrates with the protruding section  540   s   2  can be adjusted to exceed the resonant frequency of the protruding section that has a constant coil pitch, unlike the first embodiment. In general, the illumination fiber  53  is oscillated at a frequency near the resonant frequency in order to achieve stable vibration. Accordingly, by adjusting the supporting block so that the resonant frequency increases, the illumination fiber  53  can be vibrated at a higher speed compared to the first embodiment. 
     In the prior art, the resonant frequency was adjusted by selecting a different material for the illumination fiber  53 , and/or changing the length of the section of the illumination fiber  53  protruding from the fiber actuator  54 . However, in the above second embodiment, the resonant frequency can be adjusted by changing the pitch of the coil and/or the position where the pitch of the coil changes, in addition to the above prior adjustment method. 
     Next, a scanning endoscope of the third embodiment is explained. The primary difference between the third embodiment and the first embodiment is the shape of the supporting block. The third embodiment is explained mainly with reference to the structures that differ from those of the first embodiment. Here, the same index numbers are used for the structures that correspond to those of the first embodiment. 
     As shown in  FIG. 15 , the supporting block  541   s  is a metal coil spring configured so that the outside and inside diameters of section of the coil spring are substantially equal to the inside diameter of the cylindrical bending block  54   b  and the outside diameter of the illumination fiber  53 , respectively, as in the first embodiment. The supporting block  541   s  is configured so that the diameter of the strand of the coil is not constant, with the protruding section  541   s   2  formed with a strand having a smaller diameter at the end nearest to the emission end of the illumination fiber  53  than at the other end, unlike the first embodiment. 
     Owing to the above shape of the supporting block  541   s , the mass per a predetermined length along the axial direction of the spring coil is lower at the section where the strand is thinner (see “L 3 ” in  FIG. 15 ) than compared to the section where the strand is thicker (see “L 4 ” in  FIG. 15 ). Accordingly, the center of mass for the combination of the illumination fiber  53  and the protruding section  541   s   2  is relatively closer to the bending block  54   b . Owing to the shift in the center of mass, the resonant frequency of the section of the illumination fiber  53  that vibrates with the protruding section  541   s   2  is increased with the adjustment. 
     In the above third embodiment, the same effect can be achieved as in the first embodiment. In addition, the resonant frequency of the section of the illumination fiber  53  that vibrates with the protruding section  541   s   2  can be adjusted to be greater than that of the protruding section where the diameter of the strand is constant, as in the second embodiment. 
     Next, a scanning endoscope of the fourth embodiment is explained. The primary difference between the fourth embodiment and the first embodiment is the shape of the supporting block. The fourth embodiment is explained mainly with reference to the structures that differ from those of the first embodiment. Here, the same index numbers are used for the structures that correspond to those of the first embodiment. 
     As shown in  FIG. 16 , the supporting block  542   s  is a metal coil spring that comprises a recessed section  542   s   1  and a protruding section  542   s   2 . 
     The protruding section  542   s   2  is configured so that the outside and inside diameter of the coil spring increases as the position along the axial direction is closer to the emission end of the illumination fiber  53 . In addition, the protruding section  542   s   2  is configured so that the distance between the centerline of the coil strand and the axial line of the supporting block increase gradually with positive convexity. 
     In addition, the recessed section  542   s   1  is configured so that the outside and inside diameter of the coil spring are substantially equal to the inside diameter of the cylindrical bending block  54   b  and the outside diameter of the illumination fiber  53 , respectively. 
     Owing to the above shape of the supporting block  542   s , the durability of the illumination fiber  53  can be improved relative to the first embodiment. As described above, owing to the configuration of the supporting block  54   s  as a coil spring, a restoring force is distributed across the entire side of the protruding section  54   s   2 . 
     However, even if the restoring force is broadly distributed, the distributed restoring forces are not equal for each point where the illumination fiber  53  and the supporting block  54   s  make contact, and the restoring forces become greater the closer they are to the end of the supporting block  54   s  that is closest to the emission end of the illumination fiber  53  (see in  FIG. 17 ). Accordingly, the greatest force among the distributed restoring forces is exerted on the illumination fiber  53  at the end of the supporting block  54   s . On the other hand, in the above fourth embodiment, the illumination fiber  53  is bent along the inside surface of the protruding section  542   s   2 , where the inside diameter gradually spreads from the recessed section  542   s   1  to the end, and the restoring force exerted on the illumination fiber  53  is distributed more equally than in the first embodiment (see  FIG. 18 ). 
     In the above fourth embodiment, the same effect can be achieved as in the first embodiment. In addition, the durability of the illumination fiber  53  can be improved with respect to the first embodiment. 
     Next, a scanning endoscope of the fifth embodiment is explained. The primary difference between the fifth embodiment and the first embodiment is the shape of the supporting block. The fifth embodiment is explained mainly with reference to the structures that differ from those of the first embodiment. Here, the same index numbers are used for the structures that correspond to those of the first embodiment. 
     As shown in  FIGS. 19 and 20 , the supporting block  543   s  comprises a plurality of metal rods bundled together to form a cylinder around the illumination fiber  53 . The metal rods have adequate elasticity. Accordingly, the metal rods can work the same as the coil spring in the first embodiment when the bending block  54   b  bends the illumination fiber  53 . The illumination fiber  53  is positioned inside of the cylindrical supporting block  543   s . The illumination fiber  53  is supported by the supporting block  543   s  as the emission end of the illumination fiber  53  protrudes from the supporting block  543   s , as in the first embodiment. 
     In addition, a portion of the supporting block  543   s  is fixed inside of the cylindrical bending block  54   b , as in the first embodiment. Accordingly, the supporting block  543   s  is positioned between the bending block  54   b  and the illumination fiber  53 , as in the first embodiment. 
     In the above fifth embodiment, the same effect can be achieved as in the first embodiment. 
     Next, a scanning endoscope of the sixth embodiment is explained. The primary difference between the sixth embodiment and the fifth embodiment is the shape of the supporting block. The sixth embodiment is explained mainly with reference to the structures that differ from those of the fifth embodiment. Here, the same index numbers are used for the structures that correspond to those of the first embodiment. 
     As shown in  FIG. 21 , the supporting block  544   s  comprises a plurality of metal rods bundled together to form a cylinder around the illumination fiber  53 , as in the fifth embodiment. The rods that constitute the supporting block  544   s  are configured so that their thickness in the protruding section  544   s   2  tapers off and their diameter decreases toward the end corresponding to the emission end of the illumination fiber  53 , unlike in the fifth embodiment. Accordingly, a cross-sectional area of the protruding section  544   s   2  perpendicular to the longitudinal direction of the protruding section  544   s   2  varies according to a position of the protruding section  544   s   2  along the first direction. 
     Owing to the above shape of the supporting block  544   s , the mass per a predetermined length along the axial direction of the tapered section of the supporting block  544   s  (see “L 5 ” in  FIG. 21 ) is lower than that of the non-tapered, constant thickness section (see “L 6 ” in  FIG. 21 ). Accordingly, the center of mass for the combination of the illumination fiber  53  and the protruding section  544   s   2  is relatively closer to the bending block  54   b . Owing to the shift in the center of mass, the resonant frequency of the section of the illumination fiber  53  vibrating with the protruding section  544   s   2  is increased with the adjustment. 
     In the above sixth embodiment, the same effect can be achieved as in the fifth embodiment. In addition, in the above sixth embodiment, the resonant frequency of the section of the illumination fiber  53  that vibrates with the protruding section  544   s   2  can be adjusted to be greater than that of the non-tapered, constant thickness rods constituting the supporting block, as in the second and third embodiments. 
     Next, a scanning endoscope of the seventh embodiment is explained. The primary difference between the seventh embodiment and the fifth embodiment is the shape of the supporting block. The seventh embodiment is explained mainly with reference to the structures that differ from those of the fifth embodiment. Here, the same index numbers are used for the structures that correspond to those of the first embodiment. 
     As shown in  FIG. 22 , the supporting block  545   s  comprises a plurality of metal rods bundled together to form a cylinder around the illumination fiber  53 . The metal rods are configured to have the recessed section  545   s   1  and the protruding section  545   s   2  as one body. The recessed section  545   s   1  is formed to be straight. The protruding section  545   s   2  is funnel-shaped with a curved surface. In addition, the narrowest end of the protruding section  545   s   2  is connected to the recessed section  545   s   1  to form one body. In addition, the protruding section  545   s   2  is formed so that the distance between the inside surface and the axial line of the supporting block  545   s  increases with positive convexity as the point on the axial line moves further from the recessed section  545   s   1 . One end of the supporting block  545   s  is positioned inside the bending block  54   b.    
     In the above seventh embodiment, the same effect can be achieved as in the fifth embodiment. In addition, in the above seventh embodiment, as in the fourth embodiment, the durability of the illumination fiber  53  can be improved with respect to the fifth embodiment. 
     The supporting blocks  54   s ,  540   s ,  541   s ,  542   s ,  543   s ,  544   s , and  545   s  comprise either a coil spring or elastic metal rods in the above first-seventh embodiments. However, other springs or elastic materials can constitute the supporting block. The same effect can be achieved as that in the first-seventh embodiments as long as the supporting block can deform elastically and transmit the restoring force to the side of the illumination fiber  53 . 
     The fiber actuator  54   b  bends the illumination fiber  53  in four directions, which are the positive and negative components of the second and third directions, in the above first-seventh embodiments. However, the fiber actuator  54   b  may bend the illumination fiber  53  in any, but at least one, direction. 
     The supporting blocks  54   s ,  540   s ,  541   s ,  542   s ,  543   s ,  544   s , and  545   s  are made of metal material in the above first-seventh embodiments. However, the supporting block can be made of another material that provides sufficient protection against deformation caused by high ambient temperatures. Or, the supporting block does not have to be made of such kind of material. Even if the supporting block does not provide sufficient protection against deformation at high ambient temperatures, a scanning endoscope can still be accurately manufactured with an illumination fiber  53  that can sufficiently withstand the pushing force exerted by the bending block  54   b  as in the first-seventh embodiments. 
     The supporting blocks  54   s ,  540   s ,  541   s ,  542   s ,  543   s ,  544   s , and  545   s  protrude from the bending block  54   b  in the first-seventh embodiments. However, the supporting block may not be protruding. Even if the supporting block is not protruding, the same effect can be achieved as in the first-seventh embodiments as long as the supporting block deforms elastically and transmits the restoring force to the side of the illumination fiber  53 . 
     The metal rods that constitute the supporting block  543   s ,  544   s , and  545   s  are bundled together to forma complete circle around the illumination fiber  53 , in the fifth-seventh embodiments. However, a minimum number of metal rods may be mounted in the direction for bending the illumination fiber  53 . In the fifth-seventh embodiments, the illumination fiber  53  is bent in every combination of positive and negative second and third direction. If the illumination fiber  53  is bent in only one specific direction, the same effect can be achieved as in the fifth-seventh embodiments as long as the metal rod is mounted in the specific direction from the illumination fiber  53 . 
     The center of mass for the combination of the illumination fiber  53  and the protruding section  540   s   2 ,  541   s   2 , and  542   s   2  is adjusted toward the bending block  54   b  in the above second, third, and sixth embodiments. However, the position of the center of mass can be adjusted toward the emission end of the illumination fiber  53 . 
     As shown in  FIG. 23 , the center of mass can be shifted toward the emission end of the illumination fiber  53  by forming the supporting block so that the coil pitch of the protruding section  546   s   2  is longer in the section nearest to the bending block  54   b  than the section corresponding to the side nearest to the emission end of the illumination fiber  53 . By shifting the center of mass toward the emission end, the resonant frequency of the section of the illumination fiber  53  that vibrates with the protruding section can be reduced so that the illumination fiber  53  vibrates at a lower speed. 
     In addition, as shown in  FIG. 24 , the center of mass can be shifted toward the emission end of the illumination fiber  53  by configuring the supporting block so that the diameter of the strand of the protruding section  547   s   2  tapers off and is smallest at the end nearest to the bending block  54   b.    
     In addition, as shown in  FIG. 25 , the center of mass can be shifted toward the emission end of the illumination fiber  53  by configuring the supporting block so that the thickness of the rods that constitute the supporting block in the protruding section  548   s   2  tapers off and the rods become thinner toward the bending block  54   b.    
     As described above, the center of mass is adjustable by changing the mass per a predetermined length along a longitudinal direction of the supporting block. 
     The supporting blocks  543   s ,  544   s , and  545   s  comprise a plurality of metal rods in the fifth-seventh embodiments. However, the supporting block can comprise a plurality of flat springs. 
     The fiber actuator  54  moves the illumination fiber  53  so that the emission end of the illumination fiber  53  traces the predetermined spiral course, in the above first-seventh embodiments. However, the course to be traced is not limited to a spiral course. The illumination fiber  53  can be moved so that the emission end traces other predetermined courses. 
     Although the embodiments of the present invention have been described herein with reference to the accompanying drawings, obviously many modifications and changes may be made by those skilled in this art without departing from the scope of the invention. 
     The present disclosure relates to subject matter contained in Japanese Patent Application No. 2009-005109 (filed on Jan. 13, 2009), which is expressly incorporated herein, by reference, in its entirety.