Patent Publication Number: US-2010121146-A1

Title: Scanning endoscope, scanning endoscope processor, and scanning endoscope apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to reducing distortion appearing around the center of a spiral scanning course when using a scanning endoscope that scans a subject with illumination light along the spiral scanning course. 
     2. Description of the Related Art 
     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, is known. 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. 
     For the purpose of quick and stable scanning, Japanese Patent No. 3943927 discloses that the emission end of the optical fiber is moved along a spiral course. It is possible to reproduce an image with little distortion by spirally moving the emission end so that the distance from the center of the spiral course to the position of the emission end of the optical fiber increases in proportion to the amount of elapsed time since the emission end began moving away from the center on its spiral course. 
     It is possible to move the emission end along the spiral course in a stable manner when the emission end is a sufficient distance away from the center of the spiral course. However, it is difficult to circulate the emission end and increase the radius of the circulation when the emission end is near the center of the spiral course. Accordingly, distortion appears near the point corresponding to the center of the spiral course. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide a scanning endoscope that scans an observation area with light along a spiral scanning course while reducing the amount of distortion that appears in a reproduced image near the point corresponding to the center of the spiral course. 
     According to the present invention, a scanning endoscope, comprising a first transmitter, an actuator, a first mirror, and a second mirror, is provided. The first transmitter emits a beam of radiant light from an emission end. The beam of radiant light is shined on an observation area. The actuator moves the emission end along a spiral course from a predetermined standard point. The first mirror is arranged from the emission end toward a first direction when the emission end is on the standard point. The radiant light is emitted in the first direction from the emission end when the emission end is on the standard point. The first mirror comprises a first reflection surface around the first direction. The distance between a first position on a first line to any second position on the first reflection surface increases as the first position is moved in the first direction. The standard point is on the first line. The first line is parallel to the first direction. The first reflection surface reflects the radiant light emitted from the first transmitter. A line connecting the first and second positions is perpendicular to the first line. The second mirror is arranged around the first reflection surface. The second mirror comprises a second reflection surface. The second reflection surface reflects the radiant light reflected by the first mirror in a direction that includes the first direction as a positive vector toward any points on the first line. 
     According to the present invention, a scanning endoscope processor, comprising a light source, a light receiver, an image processor, and a first controller, is provided. The light source supplies the radiant light to the first transmitter of the scanning endoscope. The light receiver detects and receives various amounts of reflected light at the observation area illuminated with the radiant light. The image processor produces an image corresponding to the observation area on the basis of the amounts of the reflected light detected by the light receiver. The first controller suspends the production of an image at the image processor when the emission end is within a first area of which its center is the standard point and of which its radius is a first length. The first controller orders the image processor to produce the image when the emission end is outside of the first area. 
     According to the present invention, a scanning endoscope apparatus, comprising the scanning endoscope and the scanning endoscope processor, is provided. 
    
    
     
       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  illustrates the schematic appearance of a scanning endoscope apparatus comprising a scanning endoscope and a scanning endoscope processor of the first and second embodiments of the present invention; 
         FIG. 2  is a block diagram schematically showing the internal structure of the scanning endoscope processor of the first embodiment; 
         FIG. 3  is a block diagram schematically showing the internal structure of the light-source unit of the first embodiment; 
         FIG. 4  is a block diagram schematically showing the internal structure of the scanning endoscope of the first embodiment; 
         FIG. 5  is a sectional view of the hollow tube and the optical unit along the axis direction of the illumination fiber for illustration of the arrangements of the optical unit and the illumination fiber in the first embodiment; 
         FIG. 6  is a sectional view of the fiber actuator along the axis direction of the illumination fiber for illustration of the structure of the fiber actuator in the first and second embodiments; 
         FIG. 7  is a front view of the fiber actuator in the first and second embodiments as seen from the emission end of the illumination fiber; 
         FIG. 8  is a perspective view of the fiber actuator in the first and second embodiments; 
         FIG. 9  is a graph illustrating the changing position of the emission end moving from the standard point along the first and second bending directions in the first and second embodiments; 
         FIG. 10  illustrates a spiral course along which the emission end of the illumination fiber is moved by the fiber actuator; 
         FIG. 11  is a perspective view of the second mirror in the first embodiment; 
         FIG. 12  is a perspective view of the first mirror in the first and second embodiments; 
         FIG. 13  illustrates the point on the first mirror illuminated with the white laser beam when the emission end of the illumination fiber is moved along the first circumference; 
         FIG. 14  illustrates the locus of the white laser beam emitted from the illumination fiber for explaining the conditions regarding the shapes of the first and second mirrors; 
         FIG. 15  illustrates the white laser beam emitted from the condenser lens; 
         FIG. 16  is a block diagram schematically showing the internal structure of the scanning endoscope processor of the second embodiment; 
         FIG. 17  is a block diagram schematically showing the internal structure of the light-source unit of the second embodiment; 
         FIG. 18  is a block diagram schematically showing the internal structure of the scanning endoscope of the second embodiment; 
         FIG. 19  is a perspective view of the second mirror unit in the second embodiment; 
         FIG. 20  is a perspective view of the second mirror in the second embodiment; and 
         FIG. 21  is a block diagram schematically showing the internal structure of the position estimation unit of the second embodiment. 
     
    
    
     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 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 (first 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 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 scanner driver  22 , an image processing circuit  23 , a timing controller  24 , a system controller  25 , and other components. 
     As described later, the light-source unit  30  provides the illumination fiber  53  with white light (radiant light) to illuminate an observation area. The scanning driver  22  controls the fiber actuator  54  to move the emission end of the illumination fiber  53 . The reflected light at the illuminated point is transmitted to the scanning endoscope processor  20  by 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 reflected 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 image processing circuit  23 , the scanning driver  22 , 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. 
     As shown in  FIG. 3 , the light-source unit  30  comprises a red laser  31   r,  a green laser  31   g,  a blue laser  31   b,  first to third filters  32   a,    32   b,  and  32   c,  a condenser lens  33 , a laser driver  34 , and other components. 
     The red, green, and blue lasers  31   r,    31   g,  and  31   b  emit red, green, and blue laser beams, respectively. 
     The first filter  32   a  reflects the band of blue light that the blue laser  31   b  emits, and transmits the other bands. The second filter  32   b  reflects the band of green light that the green laser  31   g  emits, and transmits the other bands. The third filter  32   c  reflects the band of red light that the red laser  31   r  emits, and transmits the other bands. 
     The condenser lens  33 , the first filter  32   a,  the second filter  32   b,  the third filter  32   c  are arranged in the incident direction of the incident end of the illumination fiber  53 , which is connected to the light-source unit  30 . The first to third filters  32   a,    32   b  and  32   c  are fixed so that the surfaces of the filters are inclined by 45 degrees against the axis direction of the illumination fiber  53 . 
     The blue laser  31   b  is mounted so that the blue laser beam emitted by the blue laser  31   b  is reflected by the first filter  32   a  and made incident on the incident end of the illumination fiber  53 . 
     The green laser  31   g  is mounted so that the green laser beam emitted by the green laser  31   g  is reflected by the second filter  32   b,  transmitted by the first filter  32   a,  and made incident on the incident end of the illumination fiber  53 . 
     The red laser  31   r  is mounted so that the red laser beam emitted by the red laser  31   r  is reflected by the third filter  32   c,  transmitted by the first and second filters  32   a  and  32   b,  and made incident on the incident end of the illumination fiber  53 . 
     The blue, green, and red laser beams are condensed by the condenser lens  33 , and made incident on the incident end of the illumination fiber  53 . 
     Upon observing a real-time image in the peripheral area of the insertion tube  51 , the red, green, and blue laser beams are mixed into a white laser beam, which is supplied to the illumination fiber  53 . 
     The laser driver  34  drives the red, green, and blue lasers  31   r,    31   g,  and  31   b.  In addition, on the basis of the control of the timing controller  24 , the laser driver  34  controls the light-on and -off timing for the lasers  31   r,    31   g,  and  31   b.    
     Next, the structure of the scanning endoscope  50  is explained. As shown in  FIG. 4 , the scanning endoscope  50  comprises the illumination fiber  53 , the fiber actuator  54 , the image fibers  55 , an optical unit  60 , a hood  56  (guide), 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, the white laser beam emitted by the light-source unit  30  is incident on the incident end of the illumination fiber  53 . The incident white laser beam 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. 5 ). The hollow tube  57  is positioned so that the axis directions of the distal end of the insertion tube  51  and the hollow tube  57  are parallel. 
     As shown in  FIG. 5 , 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 axis direction of the hollow tube  57  is parallel to a first direction, which is an axis direction, of the insertion tube  51  that is not moved by the fiber actuator  54 . 
     As shown in  FIG. 6 , the fiber actuator  54  comprises a supporting block  54   s  and a bending block  54   b.  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  nearest the distal end of the insertion tube  51  by the supporting block  54   s.    
     As shown in  FIG. 7 , 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  on the basis of a fiber driving signal transmitted from the scanner 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. 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. 8 , the bending block  54   b  bends along a first bending 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. The piezoelectric elements constituting the first bending element  54   b   1  are arranged along the first bending direction. 
     In addition, the bending block  54   b  bends along a second bending 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 arranged along the second bending direction. 
     The side of illumination fiber  53  is pushed along the first and/or second bending directions by the bending block  54   b  via the supporting block  54   s,  and the illumination fiber  53  bends toward the first and/or second bending directions, which are perpendicular to the axis direction of the illumination fiber  53 . The emission end of the illumination fiber  53  is moved by bending the illumination fiber  53 . 
     As shown in  FIG. 9 , the emission end of the illumination fiber  53  is moved so that the emission end vibrates along the first and second bending directions at amplitudes that are repetitively increased and decreased. The frequencies of the vibration along the first and second bending directions are adjusted to be equal. In addition, the period to increase and to decrease the amplitudes of the vibration along the first and second bending directions are synchronized. Further, phases of the vibration along the first and second bending directions are shifted by 90 degrees. 
     By vibrating the emission end of the illumination fiber  53  along the first and second bending directions as described above, the emission end traces the spiral course shown in  FIG. 10 , 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. As described later, while the emission end is vibrated with increasing amplitude starting from the circulation of the emission end on a predetermined circumference (see “scanning period” in  FIG. 9 ), 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 along the predetermined circumference by vibrating the emission end along the first and second bending directions at decreasing amplitudes during a braking period, as shown in  FIG. 9 . When the emission end is moved along the predetermined circumference, it is the beginning of a scanning operation for generating another image. 
     The optical unit  60  is mounted on the end of the hollow tube  57  in the axis direction, which is in the emission direction of light from the emission end that is positioned on the standard point. The optical unit  60  comprises first and second mirrors  61  and  62 , and a mirror fixing plate  63  (see  FIG. 5 ). 
     As shown in  FIG. 11 , the second mirror  62  has a hollow tube shape so that the inside surface of the hollow tube is a conical surface and the internal diameter of the hollow tube increases along the axis direction of the hollow tube shape. On the inside surface of the second mirror  62  is formed a second reflection surface that reflects the white laser beam emitted from the light-source unit  30 . 
     The mirror fixing plate  63  is attached to the second mirror  62  on the end having the greater internal diameter (see  FIG. 5 ). The mirror fixing plate is made of colorless and transparent material. The mirror fixing plate  63  transmits the white laser beam emitted from the light-source unit  30 . 
     As shown in  FIG. 12 , the first mirror  61  is shaped as a cone. On the outside surface of the first mirror  61  is a first reflection surface  61   r  that reflects the white laser beam emitted from the light-source unit  30 . In addition, near the apex of the cone on the outside surface of the first mirror  61  is also an attenuation surface  61   a  that attenuates the white laser beam. 
     The first mirror  61  is supported by the mirror fixing plate  63  via the connecting member  64  so that a conical axis of the first mirror  61  is perpendicular to the surface of the mirror fixing plate  63 . 
     The optical unit  60  is attached to the hollow tube  57  so that the end having the smaller internal diameter faces the emission end of the illumination fiber  53  (see  FIG. 5 ). In addition, the optical unit  60  is positioned so that the conical axis of the first mirror  61  is aligned with a first straight line (see “L 1 ” in  FIG. 5 ) that passes the standard point and is parallel to the axis direction of the hollow tube  57 . 
     The white laser beam emitted from the illumination fiber  53  is reflected by the first reflection surface  61   r  of the first mirror  61  and reaches the second reflection surface of the second mirror  62 . The white laser beam reaching the second reflection surface is reflected toward the mirror fixing plate  63  by the second reflection surface. The white laser beam reflected by the second reflection surface passes through the mirror fixing plate  63  and is shined on the observation area. 
     As described above, it is difficult to circulate or spirally move the emission end of the illumination fiber  53  in a stable manner within a circular area having a certain radius and the standard point as its center. A minimum radius that enables the emission end of the illumination fiber  53  to circulate in a stable manner is measured and defined as a first radius (first length). 
     As shown in  FIG. 13 , the white laser beam emitted from the emission end that is moved along a first circumference (see “c 1 ”) of a circular pattern with the standard point (see “sp”) at its center and the first radius (see “r 1 ”) as its radius reaches a second circumference (see “c 2 ”) on the first mirror  61 . The second circumference is a locus defined by moving a point on the conical surface of the first mirror  61  so that the distance from the moved point to the apex remains constant. 
     The attenuation surface  61   a  (see shaded area) is formed on the conical surface bounded by the apex and the second circumference. In addition, the first reflection surface  61   r  is formed on the partial conical surface bounded by the second circumference and a circumference at the base of the conical first mirror  61 . 
     In addition, the first and second mirrors  61  and  62  are formed so that the following formulas (1) and (2) are satisfied: 
         f 1(θ1, θ2, θ3)=2×θ1−θ2−θ3&lt;π/2   (1) 
         f 2(θ1, θ2, θ3)=2×(θ1−θ2)−θ3&gt;0   (2) 
     θ 1  is an angle (first angle) between the first line (see “L 1 ” in  FIG. 14 ) and the generatrix line of the conical first mirror  61  in the above formulas. θ 2  is an angle (second angle) between the first line and the generatrix line of the conical surface of the inside of the second mirror  62  in the above formulas. θ 3  is an angle (third angle) between the first line and the emission direction of the white laser beam emitted from the emission end that is moved along the first circumference in the above formulas. 
     As shown in  FIG. 14 , f 1  (θ 1 , θ 2 , θ 3 ) is an angle between the forward direction of the white laser beam reflected by the second mirror  62  and the generatrix line of the conical surface on the inside of the second mirror  62  when the white laser beam is emitted from the emission end that is moved along the first circumference. Accordingly, by satisfying the formula (1), the white laser beam reaching the second mirror  62  from the first mirror  61  can be reflected towards the mirror fixing plate  63  (i.e., the direction including the first direction as a vector of a positive direction. 
     In addition, f 2  (θ 1 , θ 2 , θ 3 ) is an angle between the forward direction of the white laser beam reflected by the second mirror  62  and the first line when the white laser beam is emitted from the emission end that is moved along the first circumference. Accordingly, by satisfying the formula (2), the white laser beam reaching the second mirror  62  from the first mirror  61  can be reflected towards a first point (see “P 1 ” in  FIG. 14 ) on the first line when the white laser beam is emitted from the emission end that is moved along the first circumference. Consequently, the white laser beam can be shined on the entire area that is behind the first mirror  61  and on the other side from the illumination fiber  53 . 
     However, the entire observation area is only observable if the observation area is a certain distance from a second point p 2 . The second point p 2  is the point of intersection between the first line and the emission direction of the white laser beam from the emission end that is moved along the first circumference c 1 . The certain distance is the distance between the first point p 1  and the second point p 2 . 
     The hood  56  is shaped as a cylindrical tube and holds the distal end of the insertion tube  51 . The length of the hood  56  is determined so that the location of the observation area is in accordance with the first point p 1 . Using the hood  56  having the length determined according to the manner described here, an image can be reproduced with good quality by scanning the observation area with the white laser beam as the hood  56  is pressed to the observation area. 
     When the white laser beam is emitted from the illumination fiber  53  toward an individual point (see  FIG. 15 ) within the observation area, the reflected light is scattered at the point. The scattered and reflected light is incident on the head end 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 optical unit  60 . 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 scanner 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 addition to the points where the white laser beam has been shined, the position of the emission end of the illumination fiber  53  is also estimated by the image processing circuit  23  on the basis of signals used to control the scanner driver  22 . While the emission end of the illumination fiber  53  is moved along the first circumference, the emission of the white laser beam from the light-source unit  30 , the generation of the pixel signals at the light-capturing unit  21 , and the production of an image at the image processing circuit  23  are suspended. 
     In the above first embodiment, an image of the entire observation area can be produced without using the white laser beam emitted from the emission end that is moved near the center of the spiral course. By avoiding using the white laser beam emitted from the emission end that is moved near the center of the spiral course, distortion in the produced image will be reduced. 
     Next, a scanning endoscope and a scanning endoscope processor of the second embodiment are explained. The primary difference between the second embodiment and the first embodiment is the structure of the second mirror. In addition, in the second embodiment the position of the emission end of the illumination fiber is estimated on the basis of optical information gained from the scanning endoscope, unlike in the first embodiment. 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. 16 , the scanning endoscope processor  200  comprises a light-source unit  300 , a light-capturing unit  21 , a scanner driver  22 , an image processing circuit  23 , a timing controller  24 , a system controller  25 , and other components, as in the first embodiment. Further, the scanning endoscope processor  200  comprises a position estimation unit  40 , unlike the first embodiment. 
     The light-source unit  300  provides the illumination fiber  53  with white light to illuminate an observation area, as in the first embodiment. In addition, the light-source unit  300  provides the illumination fiber  53  with ultraviolet light that is used for estimating the position of the emission end of the illumination fiber  53 . 
     As described later, the ultraviolet light is emitted from the emission end of the illumination fiber  53 , and transmitted to the position estimation unit  40  by a position detection fiber  58 . The position estimation unit  40  estimates the position of the emission end of the illumination fiber  53 . A position signal corresponding to the estimated position is then transmitted from the position estimation unit  40  to the scanner driver  22 . 
     The scanner driver  22  controls the fiber actuator  54  to move the illumination fiber  53  on the basis of the position signal and a control signal transmitted from the position estimation unit  40  and the timing controller  24 , respectively. 
     The reflected light at the point illuminated by the white laser beam emitted from the illumination fiber  53  is transmitted to the scanning endoscope processor  200  by the scanning endoscope (not depicted in  FIG. 16 ), as in the first embodiment The transmitted light is made incident on the light-capturing unit  21 . 
     The light-capturing unit  21  generates the image signal and stores it in the image memory  26 , as in the first embodiment. The stored image signal is transmitted to the monitor  11  via the encoder  27 , as in the first embodiment. 
     By connecting the scanning endoscope to the scanning endoscope processor  200 , two optical connections are made: one between the light-source unit  300  and the illumination fiber  53 , and the other between the light-capturing unit  21  and the image fibers  55 , as in the first embodiment. In addition, by connecting the scanning endoscope to the scanning endoscope processor  200 , the fiber actuator  54  is electrically connected with the scanning driver  22 , as in the first embodiment. In addition, by connecting the scanning endoscope to the scanning endoscope processor  200 , the position estimation unit  40  is optically connected with the position detection fibers  58  arranged in the scanning endoscope. 
     As shown in  FIG. 17 , the light-source unit  300  comprises a red laser  31   r,  a green laser  31   g,  a blue laser  31   b,  first to third filters  32   a,    32   b,  and  32   c,  a condenser lens  33  and a laser driver  34 , as in the first embodiment. In addition, the light-source unit  300  also comprises an ultraviolet laser  31   uv  and a fourth filter  32   d,  unlike the first embodiment. 
     The structures and functions of the red laser  31   r,  the green laser  31   g,  the blue laser  31   b,  the first to third filters  32   a  to  32   c,  the condenser lens  33 , and the laser driver  34  are the same as those in the first embodiment. 
     The ultraviolet laser  31   uv  emits an ultraviolet laser beam with a wavelength that falls within the range of a first band. The first band is broad and different from the band of visible light. The fourth filter  32   d  reflects the ultraviolet light of the first band, and transmits the other bands. The fourth filter  32   d  is arranged between the condenser lens  33  and the first filter  32   a.    
     The fourth filter  32   d  is fixed so that the surface of the filter is inclined by 45 degrees against the axis direction of the illumination fiber  53 . The ultraviolet laser  31   uv  is mounted so that the ultraviolet laser beam emitted by the ultraviolet laser  31   uv  is reflected by the fourth filter  32   d  and made incident on the incident end of the illumination fiber  53 . In addition, the ultraviolet laser is condensed by the condenser lens  33 , and made incident on the incident end of the illumination fiber  53 . 
     Upon observing a real-time image in the peripheral area of the insertion tube  51 , the red, green, and blue laser beams are mixed into a white laser beam, which is supplied to the illumination fiber  53 , as in the first embodiment. In addition, the ultraviolet light of the first band is supplied to the illumination fiber  53 . 
     The laser driver  34  drives the red, green, and blue lasers  31   r,    31   g,  and  31   b,  as in the first embodiment. In addition, the laser driver  34  drives the ultraviolet laser  31   uv.    
     As shown in  FIG. 18 , the scanning endoscope  500  comprises the illumination fiber  53 , the fiber actuator  54 , the image fibers  55 , an optical unit  600  and a hood  56 , as in the first embodiment. In addition, the scanning endoscope  500  also comprises the position detection fiber  58 . 
     The illumination fiber  53  and the image fibers  55  are arranged inside the scanning endoscope  500  from the connector  52  to the distal end of the insertion tube  51 , as in the first embodiment. In addition, the position detection fiber  58  is arranged inside the scanning endoscope  500  from the connector  52  to the distal end of the insertion tube  51 . 
     As described above, the white laser beam and the ultraviolet laser beam emitted by the light-source unit  300  is incident on the incident end of the illumination fiber  53 . The incident white and ultraviolet laser beams are 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 , as in the first embodiment (see  FIG. 5 ). The illumination fiber  53  is supported inside of the hollow tube  57  by the fiber actuator  54 . The posture of the hollow tube  57  for the insertion tube  51  and the posture of the illumination fiber for the hollow tube  57  are the same as those in the first embodiment. 
     The structure and the function of the fiber actuator  54  are the same as those in the first embodiment. The emission end of the illumination fiber  53  is moved along the spiral course on the basis of a fiber driving signal transmitted from the scanner driver  22 , as in the first embodiment. 
     The optical unit  600  is mounted in the emission direction of light from the emission end that is positioned on the standard point, as in the first embodiment. The optical unit  600  comprises a first mirror  61 , a second mirror  620  (see  FIG. 19 ), and a mirror fixing plate  63 , as in the first embodiment. 
     As shown in  FIG. 19 , a plurality of the second mirrors  620  forms a second mirror unit  62   u,  unlike the first embodiment. The shape of the second mirror unit  62   u  is the same as that of the second mirror  62  in the first embodiment. Accordingly, the second mirror unit  62   u  has a hollow tube shape so that the inside surface of the hollow tube is a conical surface, and the internal diameter of the hollow tube increases along the axis direction of the hollow tube shape. The inside conical surface of the second mirror unit  62   u  has a second reflection surface that reflects the white laser beam, which is visible light, and transmits the ultraviolet light of the first band. 
     The second mirror  620  is shaped by dividing the second mirror unit  62   u  equally by planes that contain the axis (see “ax” in  FIG. 20 ) of the hollow-tube-shaped second mirror unit  62   u.    
     The second mirror  620  is connected to the position detection fiber  58 . The ultraviolet light that reaches the inside of the second mirror  620  is incident on the position detection fiber  58  and is transmitted to the position estimation unit  40 . 
     The surfaces of the second mirror  620  other than the second reflection surface reflect light of all bands. Accordingly, the ultraviolet light that reaches the second mirror  620  is repeatedly reflected by the surfaces except for the second reflection surface, and is incident on the position detection fiber  58 . In addition, a plurality of position detection fibers  58  are individually connected, respectively, to each one of the plurality of second mirrors  620 . 
     The mirror fixing plate  63  is attached to the second mirror unit  62   u  at the end having the greater internal diameter, as in the first embodiment. The structures, functions and arrangements of the mirror fixing plate  63  and the first mirror  61  are the same as those in the first embodiment. The optical unit  600  is attached to the hollow tube  57  so that the end having the smaller internal diameter faces the emission end of the illumination fiber  53 , as in the first embodiment. 
     An angle (second angle) between the first line and the generatrix line of the conical surface inside the second mirror unit  62   u  is defined as θ 2 . The definitions of θ 1  and θ 3  are the same as those in the first embodiment. With such a definition, the first mirror  61  and the second mirror unit  62   u  are arranged so that the above formulas (1) and (2) are relevant, as in the first embodiment. 
     The structures and the functions of the hood  56  and the image fibers  55  are the same as those in the first embodiment. Accordingly, the reflected light of a fine point illuminated by the white laser beam is incident on the incident ends of the image fibers  55 , and transmitted to the emission ends of the image fibers  55 . 
     As described above, the ultraviolet light that reaches the second mirror  620  is transmitted to the position estimation unit  40  by the position detection fiber  58 . In addition, the reflected light of the white laser beam illuminating the observation area is transmitted to the light-capturing unit  21  by the image fibers  54 . 
     As shown in  FIG. 21 , the position estimation unit  40  comprises a plurality of ultraviolet light detectors  41  and a brake controller  42 . Each of the ultraviolet light detectors  41  is optically connected to each of the position detection fibers  58 . When detecting the capture of the ultraviolet light, the ultraviolet light detector  41  transmits a detection signal to the image processing circuit  23  and the brake controller  42 . 
     The ultraviolet light emitted from the illumination fiber  53  is made incident on one of the plurality of second mirrors  620  that constitutes the second mirror unit  62   u.  Accordingly, the ultraviolet light is detected by only one of the many ultraviolet light detectors  41 . Consequently, the inclined direction of the illumination fiber  53  is determinable on the basis of the ultraviolet light detector  41  that outputs the detection signal. 
     The brake controller  42  generates a braking signal in the braking period on the basis of the ultraviolet light detector  41  that outputs the detection signal, and transmits the braking signal to the scanner driver  22 . The braking signal helps the emission end of the illumination fiber  53  to return along the first circumference. The scanner driver  22  generates the fiber driving signal on the basis of the braking signal, and transmits the fiber driving signal to the first and second bending elements  54   b   1  and  54   b   2 . 
     The light-capturing unit  21  generates the pixel signals according to the amounts of reflected light, as in the first embodiment. 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 the detection signal and the signals used to control the scanner driver  22 . The image processing circuit  23  stores the received pixel signals at the address of the image memory  26  corresponding to the estimated points, as in the first embodiment. 
     The observation area is scanned with the white laser beam, pixel signals are generated on the basis of the light reflected from the respective points illuminated with the white laser beam, and the generated pixel signals are stored at the address corresponding to the points, as in the first embodiment. 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. The image signal is transmitted to the monitor  11  after the image processing circuit  23  carries out predetermined image processing on the image signal, as in the first embodiment. 
     While the emission end of the illumination fiber  53  is moved within the first circumference, the emission of the white laser beam from the light-source unit  30 , the generation of the pixel signals at the light-capturing unit  21 , and the production of an image at the image processing circuit  23  are all suspended, as in the first embodiment. 
     In the above second embodiment, an image of the entire observation area can be produced without using the white laser beam emitted from the emission end that is moved near the center of the spiral course. By avoiding using the white laser beam, distortion in the produced image will be reduced. 
     In addition, in the above second embodiment, it is possible to detect the direction in which the emission end of the illumination fiber  53  inclines. Accordingly, the time required to return the emission end of the illumination fiber  53  to the first circumference, from the start of the braking period, can be shortened. 
     In addition, the accuracy of the estimation of the points where the white laser beam is shined is improved because the point is estimated using the direction in which the emission end of the illumination fiber  53  inclines. It is possible to reduce the influence of the distortion appearing in the displayed image by improving the accuracy of the estimation. 
     The first mirror  61  is shaped as a cone in the first and second embodiments. However, the shape of the first mirror  61  is not limited to a cone. Other shapes can be adopted as long as the distance from the first position on the first straight line to any second position on the first reflection surface increases with the distance between the first position and the illumination fiber  53 . The line connecting the first and second positions is perpendicular to the first straight line. In other words, other shape can be adopted as long as the distance from the first position to any second position increases as the first position is moved toward the first direction. For example, bowl and bell shapes can be adopted. 
     The inside of the hollow tube of the second mirror  62  and  620  is shaped conically, in the first and second embodiments. However, the inside shape of the second mirrors is not limited to a conical shape. The same effect as the above embodiments can be achieved as long as the second mirror is shaped so that the light reflected by the first mirror  61  is in the direction that includes the first direction as a positive vector, and is toward any point on the first line. 
     The emission end of the illumination fiber  53  is moved by inclining the illumination fiber  53 , in the first and second embodiments. However, the emission end can be moved without inclining the illumination fiber  53 . If the emission end is moved without inclining the illumination fiber  53 , the direction in which the white laser beam is emitted from the emission end is parallel to the first direction. In such a case, the same effect as the above embodiments can be achieved by shaping the first mirror  61  and the second mirror  62  and  620  so that the first angle is greater than the second angle. 
     The second mirror  62  and  620  entirely surrounds the first reflection surface of the first mirror  61 , in the first and second embodiments. However, the first reflection surface may not be surrounded entirely. Even if the first reflection surface is not surrounded, the observation area can be scanned with the white laser beam. 
     The distal end of the insertion tube  51  is held by the hood  56 , in the first and second embodiments. However, the observation area can be observed without the hood  56 . Without the hood  56 , it is possible for a user to produce an accurate image by adjusting the distance from the distal end of the insertion tube  51  to the observation area. 
     The first mirror  61  has the attenuation surface  61   a,  in the first and second embodiments. However, the first mirror  61  may not have the attenuation surface  61   a.  Unless the first mirror  61  has the attenuation surface  61   a,  the observation area is scanned with the white laser beam emitted from the emission end, which moves along the first circumference in an unstable manner. However, it is still possible to produce an accurate image because the production of the image is suspended while the emission end is moved along the first circumference. Because of the attenuation surface  61   a  in the above embodiments, the white laser beam, which is unnecessary for illumination, is prevented from being shined on the observation area. 
     The emission of the white laser beam from the light-source unit  30  and  300  is suspended when the emission end of the illumination fiber  53  is moved along the first circumference, in the first and second embodiments. However, the emission may not be suspended. As described above, it is possible to produce an accurate image even if the emission is not suspended, because the production of the image is suspended while the emission end is moved along the first circumference. Owing to the suspension of the emission as in the above embodiments, the power consumption can be reduced. 
     The generation of the pixel signals by the light-capturing unit  21  is suspended when the emission end of the illumination fiber  53  is moved along the first circumference, in the first and second embodiments. However, the generation may not be suspended. As described above, even if the pixel signals are generated when the emission end is moved along the first circumference, the pixel signals are not used for the production of the image signal because the production of the image is suspended while the emission end is moved along the first circumference. Accordingly, it is possible to produce an accurate image even if the generation is not suspended. Owing to the suspension of the generation of the pixel signals as in the above embodiments, the power consumption can be reduced. 
     The first band pertains to a range of wavelengths for ultraviolet light, in the second embodiment. However, the first band may be a range of wavelengths of infrared light. Or, the first band can be a range for any light with a wavelength that is different from those of the red, green and blue lights emitted by the red, green, and blue lasers  31   r,    31   g,  and  31   b,  respectively, and which passes through the second mirror  620 . 
     The detection signal output by the ultraviolet light detector  41  is used for the estimation of the points where the white laser beam is shined, in the second embodiment. However, the detection signal may not be used for the estimation. 
     Lasers are used as light sources to emit red, green, and blue light, in the first and second embodiments. However, other kinds of light sources may be used. But, a laser is preferable for the light source in the above embodiments because it is preferable to shine the illumination light on a minute point within an observation area of the scanning endoscope, and a laser can emit light having strong directivity. 
     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. 2008-289209 (filed on Nov. 11, 2008), which is expressly incorporated herein, by reference, in its entirety.