Abstract:
An adjustment mechanism that adjusts an inclination and a position of an optical axis of an excitation light optical system with respect to an optical axis of a white light optical system is provided. The adjustment mechanism includes a frame plate, a plate-shaped lever, a fixing unit, a first adjuster, and a second adjuster. The frame plate is orthogonally placed with respect to the optical axis of the white light optical system, and perforated with a pair of circular holes, and an elliptical hole. The plate-shaped lever is perforated with a first elliptical hole and a second elliptical hole and a cylindrical projection. The fixing unit fixes the excitation light optical system to the plate-shaped lever. The first adjuster includes a first supporting axle and a first disc-shaped cam to which the first supporting axle is eccentrically fixed, the first disc-shaped cam being rotatably and slidably fitted in the first elliptical hole of the plate-shaped lever. The second adjuster includes a second supporting axle and a second disc-shaped cam to which the second supporting axle is eccentrically fixed, the second disc-shaped cam being rotatably and slidably fitted in the second elliptical hole of the plate-shaped lever.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an adjustment mechanism that adjusts an inclination and a position of an optical axis of an optical system. 
   It is known that a body tissue is excited and emits a fluorescence when irradiated by light of a specific wavelength. An abnormal body tissue having a lesion such as a tumor or a cancer emits a weaker fluorescence than a normal body tissue does. Such reaction is also performed by a body tissue under a body cavity wall. Accordingly, an endoscope system that detects an abnormality in a body tissue under a body cavity wall utilizing such reactive phenomenon has recently been developed. Such an endoscope system is disclosed in, for example, U.S. Patent Application Publication No. 2002175993A1 and U.S. Pat. No. 6,602,186. 
   Functions of such endoscope systems include, in addition to a basic observation mode of simply emitting visible light from a tip of the endoscope to illuminate an internal area of a body cavity, a special observation mode of alternately emitting from the tip of the endoscope a visible light and an excitation light for exciting a body tissue under a body cavity wall. 
   SUMMARY OF THE INVENTION 
     FIG. 10  shows one example of a light source unit configured to be used in the endoscope system having the functions of the basic observation mode and the special observation mode. 
   In the basic observation mode, a light source unit of the endoscope system introduces white light emitted by a white light emitting device to a facet of a light guide fiber bundle extended through inside the endoscope. In the special observation mode, an optical path merging device is disposed in the optical path of the white light, and an excitation light emitting device provided in the light source unit emits excitation light to the optical path merging device, thus to introduce the excitation light to the facet of the light guide fiber bundle inside the endoscope. 
   In such light source unit, an optical fiber bundle is located throughout the path from the excitation light emitting device to an interface of the optical path merging device, for preventing attenuation of the excitation light, as well as for making the light source unit smaller in dimensions. In  FIG. 10 , which is a perspective view showing a main structure of the light source unit provided with such optical fiber bundle, the optical fiber bundle is designated by the numeral  41 . 
   As shown in  FIG. 10 , a base portion of the optical fiber bundle  41  is detachably connected to a casing of the excitation light emitting device via a connector  41   a . An end facet of the optical fiber bundle  41  is detachably connected to a square pillar-shaped lens barrel  42  via a connector  41   b . The lens barrel  42  serves to hold a collimator lens  43  that converts the excitation light emitted from the end facet of the optical fiber bundle  41  into a collimated beam. The lens barrel  42  is fixed to a frame plate  44  such that an optical axis of the collimator lens  43  runs orthogonal to an optical axis of the optical system of the white light. In  FIG. 10 , a dash-dot line Ax designates the optical axis of the optical system that leads the white light from the white light emitting device to the facet of the light guide fiber bundle inside the endoscope. An end portion of the light guide fiber bundle inside the endoscope is, when connected to the light source unit, disposed at a left-hand side behind the frame plate  44  according to the orientation of  FIG. 10 , and a central axis of the end portion is coaxial with the optical axis Ax of the white light optical system. 
   The frame plate  44  is further provided with a stage  45  via a rack and pinion mechanism, and the stage  45  is provided with a dichroic mirror  46  that transmits the white light but reflects the excitation light. The stage  45  is driven in a forward and backward direction (leftward and rightward in  FIG. 10 ) according to the selected observation mode. When the stage  45  is moved upon selecting the special observation mode, the dichroic mirror  46  comes to a position where the optical path of the white light and the optical path of the excitation light intersect each other (the state shown in  FIG. 10 ). The dichroic mirror  46  is set with an inclination of 45 degrees with respect to the optical axis of the collimator lens  43 , as well as with respect to the optical axis Ax of the white light optical system. Accordingly, the white light is transmitted straight through the dichroic mirror  46  thus to reach the facet of the light guide fiber bundle inside the endoscope, while the excitation light is reflected in a right angle by the dichroic mirror  46 , to thereby reach the facet of the light guide fiber bundle inside the endoscope. 
   When merging the optical path of the white light and that of the excitation light with the dichroic mirror  46  as above, the optical axis of the collimator lens  43  after reflected by the dichroic mirror  46  has to coincide with the optical axis Ax of the white light optical system. 
   However, in the light source unit as shown in  FIG. 10 , once the lens barrel  42  is mounted on the frame plate  44 , it is impossible to adjust an inclination or a position of the collimator lens  43  with respect to the optical axis Ax of the white light optical system. 
   The present invention has been conceived in view of the foregoing situation. The present invention is advantageous in that it provides an adjustment mechanism, to be used in a light source unit provided with an excitation light optical system that converts excitation light emitted by an excitation light emitting device into a collimated beam and emits such beam to an optical path merging device, which allows adjusting an inclination or a position of an optical axis of the excitation light optical system with respect to an optical axis of the white light optical system. 
   According to an aspect of the invention, there is provided an adjustment mechanism that adjusts an inclination and a position of an optical axis of an excitation light optical system with respect to an optical axis of a white light optical system, to be used in a light source unit including the white light optical system that leads white light emitted by a white light emitting device to a facet of a light guide provided inside an endoscope, the excitation light optical system that leads excitation light emitted by an excitation light emitting device, and an optical path merging device disposed on the optical axis of the white light optical system for bending the optical axis of the excitation light optical system substantially at a right angle toward the light guide, so as to supply the facet of the light guide with the white light for illuminating an internal area of a body cavity in which an insertion tube of the endoscope is inserted, and the excitation light for exciting a body tissue under a body cavity wall. 
   The adjustment mechanism includes a frame plate orthogonally placed with respect to the optical axis of the white light optical system, and perforated with a pair of circular holes the respective centers of which are aligned on a straight line perpendicular to a direction of the optical axis of the white light optical system, and an elliptical hole having a major axis coinciding with the straight line and a minor axis whose extension perpendicularly intersects with the optical axis of the white light optical system. The adjustment mechanism further includes a plate-shaped lever perforated with a first elliptical hole and a second elliptical hole, respective major axes of which are perpendicular to each other, and provided with a cylindrical projection located on an extension of a segment connecting the centers of the first elliptical hole and the second elliptical hole and rotatably and slidably fitted in the elliptical hole in the frame plate. The adjustment mechanism further includes a fixing unit that fixes the excitation light optical system to the plate-shaped lever such that the optical axis of the excitation light optical system becomes perpendicular to a direction parallel to the extension of the segment connecting the centers of the first and second elliptical holes. 
   Further, the adjustment mechanism includes a first adjuster including a first supporting axle rotatably held in one of the circular holes in the frame plate, and a first disc-shaped cam to which the first supporting axle is eccentrically fixed, the first disc-shaped cam being rotatably and slidably fitted in the first elliptical hole of the plate-shaped lever, and a second adjuster including a second supporting axle rotatably held in the other circular hole in the frame plate, and a second disc-shaped cam to which the second supporting axle is eccentrically fixed, the second disc-shaped cam being rotatably and slidably fitted in the second elliptical hole of the plate-shaped lever. 
   With this configuration, it is possible to adjust an inclination and a position of an optical axis of the excitation light optical system with respect to an optical axis of the white light optical system, in the light source unit provided with the excitation light optical system that converts the excitation light emitted by the excitation light emitting device into a collimated beam and emits the collimated beam to the optical path merging device. 
   Optionally, the adjustment mechanism may include a stage including a base seat which holds the optical path merging device, the stage having a first side surface to which the base seat is attached, and a second side surface facing the frame plate, a supporting member disposed with a predetermined gap from the frame plate, so as to support a first border portion of the stage, the stage being rotatable around an axis parallel to a segment connecting the centers of the pair of circular holes, and an angle adjuster that moves a second border portion of the stage opposite to the first border portion supported by the supporting member, so as to cause the second border portion to contact with or separate from the frame plate. 
   Still optionally, the first adjuster may have a first knob fixed to the first disc-shaped cam, and the second adjuster may have a second knob fixed to the second disc-shaped cam. 
   Still optionally, the major axis of the first elliptical hole of the plate-shaped lever may be parallel with the extension of the segment connecting the centers of the first and second elliptical holes of the plate-shaped lever so that, by rotating the first disc-shaped cam of the first adjuster manipulating the first knob, the plate-shaped lever is rotated around a center axis of the cylindrical projection. 
   Still optionally, the major axis of the second elliptical hole of the plate-shaped lever may be perpendicular to the extension of the segment connecting the centers of the first and second elliptical holes of the plate-shaped lever so that, by rotating the second disc-shaped cam of the second adjuster manipulating the second knob, the plate-shaped lever moves in parallel with the extension of the segment connecting the centers of the first and second elliptical holes. 
   Still optionally, the adjustment mechanism may include a first flanged screw capable of being screwed into the first supporting axle of the first adjuster so as to make the first adjuster press the plate-shaped lever against the frame plate, and a second flanged screw capable of being screwed into the second supporting axle of the second adjuster so as to make the second adjuster press the plate-shaped lever against the frame plate. 
   Still optionally, the adjustment mechanism may include a third flanged screw capable of being screwed into the cylindrical projection of the plate-shaped lever so that the plate-shaped lever is supported by the frame plate. 

   
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
       FIG. 1  is an illustration showing an appearance of an endoscope system to which the present invention is applied; 
       FIG. 2  is a block diagram showing a configuration of a light source unit of the endoscope system; 
       FIG. 3  is a perspective view showing a main structure of the light source unit including an adjustment mechanism according to an embodiment of the present invention; 
       FIG. 4  is a perspective view showing the main structure of the light source unit including the adjustment mechanism; 
       FIG. 5  is a side view showing the light source unit viewed from the right according to orientation of  FIG. 3 ; 
       FIG. 6  is an exploded perspective view showing a part of the light source unit including the adjustment mechanism; 
       FIG. 7  is a rear view showing the light source unit including the adjustment mechanism; 
       FIG. 8  is a fragmentary perspective view for explaining a movement of an optical axis of a collimator lens caused by manipulation of a first adjuster; 
       FIG. 9  is a fragmentary perspective view for explaining a movement of the optical axis of the collimator lens caused by manipulation of a second adjuster; and 
       FIG. 10  is a perspective view showing a main structure of a conventional light source unit. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Referring to the accompanying drawings, embodiments of the present invention will be described hereunder. In should be noted that the embodiment described below can be used with a light source unit provided in a generally available endoscope system. 
     FIG. 1  is an illustration showing an appearance of an endoscope system to which the present invention is applied. As shown therein, the endoscope system includes an endoscope  10 , an image processing unit  20 , and a light source unit  30 . 
   The endoscope  10  includes an insertion tube  10   a  of a slim and lengthy shape so as to be inserted into a body cavity, a manipulating unit  10   b  having an angle knob for remote manipulation of the insertion tube  10   a , an imaging unit  10   c  for capturing an image of an object confronting a tip portion of the insertion tube  10   a , a first cable  10   d  connecting the imaging unit  10   c  and the image processing unit  20 , and a second cable  10   e  connecting the manipulating unit  10   b  and the light source unit  30 . 
   The insertion tube  10   a  includes therein an objective optical system, which creates an image of an object confronting the tip portion of the insertion tube  10   a . Such image is transmitted through an image guide fiber bundle extended through inside the insertion tube  10   a , to a base portion thereof. The imaging unit  10   c  converts the object image transmitted to the base portion of the insertion tube  10   a  into image data, and outputs the image data to the image processing unit  20  via the first cable  10   d . The image processing unit  20  executes a predetermined processing on the image data received, and has the object image displayed on a monitor screen based on the processed image data. 
   The endoscope  10  further includes a light guide fiber bundle. The light guide fiber bundle is extended throughout a section from the tip portion of the insertion tube  10   a  to the end portion of the second cable  10   e , through inside the insertion tube  10   a , manipulating unit  10   b  and the second cable  10   e . The end portion of the second cable  10   e  is detachably connected to the light source unit  30 , such that an end facet of the light guide fiber bundle is inserted into inside the light source unit  30 . The light source unit  30  serves to introduce light to the end facet of the light guide fiber bundle. The light guide fiber bundle inside the endoscope  10  conducts the light emitted from the light source unit  30  to the tip portion of the insertion tube  10   a , thus to emit the light therefrom. 
     FIG. 2  is a block diagram showing a configuration of the light source unit. As shown therein, the light source unit  30  includes a white light emitting device  31  that emits a white collimated beam, an afocal optical system  32  that reduces the optical bundle diameter of the white light emitted by the white light emitting device  31 , and a condenser lens  33  that converges the white light onto the end facet of the light guide fiber bundle inside the endoscope  10 . 
   The light source unit  30  also includes an excitation light emitting device  34  that emits excitation light for exciting a body tissue under a body cavity wall, a collimator lens  35  that converts the excitation light emitted by the excitation light emitting device  34  into a collimated beam, and a dichroic mirror  36  that reflects the excitation light but transmits the white light. The excitation light emitting device  34  is provided with an optical fiber bundle  34   a  that conducts the excitation light to a focal point of the collimator lens  35 . A central axis of the end facet of the optical fiber bundle  34   a  is coaxial with the optical axis of the collimator lens  35 , and orthogonal to the optical axis of the afocal optical system  32  and the condenser lens  33 . The dichroic mirror  36  is located on the stage  37 , to serve as an optical path merging device. 
   The stage  37  is movable only in one direction orthogonal to the optical path of the white light, by a moving mechanism constituted of for example a rack and pinion engagement. On the stage  37 , the dichroic mirror  36  is placed with an inclination of 45 degrees with respect to the optical axis of the collimator lens  35 , as well as with respect to the optical axis of the afocal optical system  32  and the condenser lens  33 . 
   When the stage  37  is driven in a forward and backward direction, the dichroic mirror  36  is either set to interfere with the optical path of the white light between the afocal optical system  32  and the condenser lens  33 , or is removed from such optical path. When the dichroic mirror  36  is set to interfere with the optical path of the white light, the white light passes straight through the dichroic mirror  36  thus to reach the condenser lens  33 , while the excitation light is reflected at a right angle by the dichroic mirror  36 , to thereafter reach the condenser lens  33 . Accordingly, both of the excitation light and the white light are converged by the condenser lens  33  onto the end facet of the light guide fiber bundle inside the endoscope. On the other hand, when the dichroic mirror  36  is removed from the optical path of the white light, only the white light can reach the condenser lens  33 , to be thereby converged onto the end facet of the light guide fiber bundle inside the endoscope. 
   The light source unit  30  further includes a disc-shaped rotary shutter  38 . The rotary shutter  38  is perforated with a generally sector-shaped through hole, and an apex of the generally sector shape coincides with the center of the disc (see  FIG. 4 ). Also, a tip portion of a driving shaft of a motor is fixed to a central portion of the rotary shutter  38 , such that the rotary shutter  38  is mounted on the stage  37 . When the stage  37  moves so as to set the dichroic mirror  36  to interfere with the optical path of the white light, the rotary shutter  38  is also set to perpendicularly interfere with the optical path of the white light between the dichroic mirror  36  and the afocal optical system  32 . Likewise, when the stage  37  moves so as to remove the dichroic mirror  36  from the optical path of the white light, the rotary shutter  38  is also removed from the optical path. 
   The stage  37  is thus driven by switching the observation mode. The observation modes include a basic observation mode of illuminating an object with the white light to perform ordinary observation, and a special observation mode of alternately irradiating the white light and the excitation light to the object, thus to perform special observation. Selection of such observation modes can be executed by a switch provided on the manipulating unit  10   b  of the endoscope  10 , or on an operation panel of the light source unit  30 . Such switch is connected to a control unit  39  that controls an entirety of the light source unit  30 . 
   The control unit  39  drives the stage  37  so as to remove the dichroic mirror  36  and the rotary shutter  38  from the optical path of the white light when the basic observation mode is selected. Accordingly in the basic observation mode, only the white light is introduced to the end facet of the light guide fiber bundle inside the endoscope  10 . In this case, an internal area of the body cavity, where the insertion tube  10   a  of the endoscope  10  is inserted, is illuminated exclusively by the white light emitted from the tip portion of the insertion tube  10   a.    
   By contrast, when the special observation mode is selected, the control unit  39  drives the stage  37  so as to set the dichroic mirror  36  and the rotary shutter  38  to interfere with the optical path of the white light. The control unit  39  also rotates the rotary shutter  38  so as to introduce the white light to the end facet of the light guide fiber bundle inside the endoscope  10  at a predetermined time interval, and controls the excitation light emitting device  34  to blink so as to emit the excitation light at a moment that the white light is not introduced to the light guide fiber bundle. Employing for example a laser diode to constitute the excitation light emitting device  34  allows performing such blink control. Thus in the special observation mode, the white light and the excitation light are alternately introduced to the end facet of the light guide fiber bundle inside the endoscope  10 . Consequently, in the body cavity where the insertion tube  10   a  of the endoscope is inserted, reflection of the white light at a surface of the body cavity wall and emission of fluorescence by the body tissue under the body cavity wall are alternately repeated. 
     FIGS. 3 and 4  are perspective views showing a main structure of the light source unit  30  including an adjustment mechanism according to the present invention. In  FIG. 3 , the rotary shutter  38  and the motor therefor are omitted. Also,  FIG. 5  is a side view of the light source unit  30 , viewed from the right according to the orientation of  FIG. 3 . 
   According to  FIGS. 3 to 5 , the base portion of the optical fiber bundle  34   a  is connected to a generally parallelepiped-shaped casing of the excitation light emitting device  34 , via a connector C 1 . The end facet of the optical fiber bundle  34   a  is detachably connected to a square pillar-shaped lens barrel  35   a  via a connector C 2 . The lens barrel  35   a  serves to hold the collimator lens  35  for the excitation light, and is fixed to the frame plate  30   a , which is vertically erected, via an adjustment mechanism  350  according to the embodiment of the present invention, to be subsequently described. Here, the white light emitting device  31  is located at a closer right-hand side according to the orientation of  FIG. 3 , while the tip portion of the second cable  10   e  of endoscope  10  is located at a farther left-hand side in  FIG. 3 . The central axis of the light guide fiber bundle inside the second cable  10   e  is coaxial with the optical axis Ax 1 , which runs orthogonal to the frame plate  30   a . The lens barrel  35   a  fixed to the frame plate  30   a  is oriented such that the optical axis Ax 2  of the collimator lens  35  runs orthogonal to the optical axis Ax 1 , as well as vertical. 
   The frame plate  30   a  also sustains end portions of a horizontal bar  30   c  disposed with a predetermined gap therefrom, via a pair of supporting blocks  30   b ,  30   b  protruding from the wall thereof toward the lens barrel  35   a . The horizontal bar  30   c  is torsionally oriented with respect to the optical axis Ax 1 . The horizontal bar  30   c  is also engaged with the stage  37 . The stage  37  is formed such that base seats for a motor that rotates the rotary shutter  38  and for the dichroic mirror  36  protrude from one side of a base plate. The stage  37  is perforated with a through hole along a border portion thereof. The through hole is oriented parallel to the border portion, and has an inner diameter substantially the same as the diameter of the horizontal bar  30   c  (more precisely, slightly larger). The stage  37  is hung from the horizontal bar  30   c  penetrating the through hole, with a plane side wall thereof opposite to the base seats facing the wall of the frame plate  30   a . In this state, a border portion of the stage  37  opposite to the through hole, i.e. the lower border portion, is in contact with the frame plate  30   a . Further, on an entirety of the upper border portion of the stage  37 , inside which the horizontal bar  30   c  is located, a rack gear  37   a  is provided, which is engaged with a pinion gear  30   e  attached to the driving shaft of a motor  30   d  mounted on the frame plate  30   a.    
   When the motor  30   d  rotates in a forward and backward direction, the stage  37  is moved forward and backward (left and right according to  FIG. 3 , perpendicularly back and forth with respect to  FIG. 5 ) along the horizontal bar  30   c . When the stage  37  is moved upon selecting the special observation mode, the dichroic mirror  36  comes to a position where the optical path of the excitation light and that of the white light intersect each other (the state shown in  FIGS. 3 and 4 ). The dichroic mirror  36  is set with an inclination of 45 degrees with respect to the optical axis of the collimator lens  43 , as well as with respect to the optical axis Ax of the white light optical system, as stated earlier. Accordingly, the white light emitted from the afocal optical system  32  is transmitted straight through the dichroic mirror  36  thus to reach the condenser lens  33 , while the excitation light emitted from the collimator lens  35  is reflected at a right angle by the dichroic mirror  36 , to thereby reach the condenser lens  33 . Accordingly, both the white light and the excitation light can be introduced to the end facet of the light guide fiber bundle inside the endoscope  10 . 
   The stage  37  is provided with a screw hole perpendicularly oriented thereto near a lower lateral edge thereof, into which a screw  37   b  is inserted toward the frame plate  30   a , as shown in  FIGS. 3 and 5 . As the screw  37   b  is screwed deeper into the screw hole, a tip portion of the screw  37   b  projects from the flat plate of the stage  37  facing the frame plate  30   a , until finally contacting with the frame plate  30   a . The projecting length of the tip portion of the screw  37   b  can be adjusted according to a screwing depth thereof. Adjusting thus the projecting length of the tip portion of the screw  37   b  causes the stage  37  to rotate around the central axis of the horizontal bar  30   c , thereby varying a distance between the lower edge of the stage  37  and the frame plate  30   a . This causes a variation in inclination of the dichroic mirror  36  with respect to the optical axis Ax 1  of the afocal optical system  32  and the condenser lens  33 . In a word, the screw  37   b  serves as an adjustment mechanism of an inclination of the dichroic mirror  36 . 
     FIG. 6  is an exploded perspective view showing only the respective optical systems and the adjustment mechanism  350  according to the embodiment of the present invention, out of the components of the light source unit  30 .  FIG. 7  is a rear view of the frame plate  30   a , viewed from the side where the connection box of the second cable  10   e  is located. 
   The adjustment mechanism  350  includes a first adjuster  351 , a second adjuster  352 , a supporting member  353 , and a lever plate  354 . The first adjuster  351 , the second adjuster  352 , and the supporting member  353  are intended for pressing the lever plate  354  against the frame plate  30   a . The supporting member  353  also serves as the fixture for the lens barrel  35   a  accommodating the collimator lens  35  for the excitation light, with respect to the frame plate  30   a . The adjustment mechanism  350  will be described in further details hereunder. 
   The first adjuster  351  includes a column-shaped knob  351   a  constituting the main portion thereof. The knob  351   a  is provided with a disc-shaped cam plate  351   b  having a smaller diameter than the knob  351   a , integrally formed so as to project from a bottom face thereof. Further, the cam plate  351   b  is provided with a cylindrical projection  351   c  having a still smaller diameter, integrally formed so as to project therefrom. In a word, the first adjuster  351  is a circular column with two levels of stepped projections on a bottom face thereof, as a whole. Here, the central axis of the knob  351   a  and that of the cylindrical projection  351   c  are mutually coaxial, while the cam plate  351   b  is eccentrically formed with respect to these central axes. The cylindrical projection  351   c  has a projecting length that is slightly shorter than the thickness of the frame plate  30   a , and is provided with a female-threaded bore, so as to serve as a screw hole. 
   The second adjuster  352  is formed in the same shape and dimensions as those of the first adjuster  351 . Specifically, the second adjuster  352  includes a column-shaped knob  352   a  as the main body, a cam plate  352   b  eccentrically formed with respect thereto, a cylindrical projection  352   c  coaxial with the knob  352   a . The cylindrical projection  352   c  has a projecting length that is slightly shorter than the thickness of the frame plate  30   a , and is provided with a female-threaded bore. 
   The supporting member  353  is also of a column shape. The supporting member  353  is provided with a coaxial cylindrical projection  353   a  having a smaller diameter, integrally formed on a bottom face thereof. The cylindrical projection  353   a  has a projecting length that is slightly shorter than the thickness of the frame plate  30   a , and is provided with a female-threaded bore, so as to serve as a screw hole. 
   The lever plate  354  is an elliptical plate, having a thickness equal to the height of the cam plate  351   b ,  352   b  of the first adjuster  351  and the second adjuster  352 . The lever plate  354  is perforated with a pair of elliptical holes  354   a ,  354   b  and a through hole  354   c , such that the respective centers of the elliptical holes  354   a ,  354   b  and of the through hole  354   c  are aligned along the major axis of the lever plate  354 . 
   As used herein, the term “elliptical” hole, plate or etc. includes an oblong shape made by elongating a circular shape as well as an ellipse. Similarly to an ellipse, the major axis of the oblong (circular) shape is defined as an axis extending in an elongated direction and including a center thereof, and the minor axis of the oblong (circular) shape is defined as an axis extending in a direction perpendicular to the elongated direction and including the center thereof. 
   The minor axis of the first elliptical hole  354   a  is orthogonal to the major axis of the lever plate  354 . The length of the minor axis of the first elliptical hole  354   a  is substantially the same as the diameter of the cam plate  351   b  on the first adjuster  351  (more precisely, slightly larger). Accordingly, upon fitting the cam plate  351   b  of the first adjuster  351  into the first elliptical hole  354   a , the cam plate  351   b  can be made to rotate within the first elliptical hole  354   a , as well as to slide along the major axis of the first elliptical hole  354   a.    
   The second elliptical hole  354   b  is formed in the same shape and dimensions as those of the first elliptical hole  354   a . Accordingly, upon fitting the cam plate  352   b  of the second adjuster  352  into the second elliptical hole  354   b , the cam plate  352   b  can be made to rotate within the second elliptical hole  354   b , as well as to slide along the major axis of the second elliptical hole  354   b . Here, the minor axis of the second elliptical hole  354   b  coincides with the major axis of the lever plate  354 , and hence the direction of the major axis of the second elliptical hole  354   b  is perpendicular to the direction of the major axis of the first elliptical hole  354   a.    
   The through hole  354   c  is of a circular shape, with a diameter that is substantially the same as that of the cylindrical projection  353   a  of the supporting member  353  (more precisely, slightly larger). The through hole  354   c  is located opposite to the first elliptical hole  354   a , across the second elliptical hole  354   b.    
   The supporting member  353  is fixed to the lever plate  354 , with the cylindrical projection  353   a  inserted into the through hole  354   c  of the lever plate  354 . Here, the supporting member  353  is unmovably fixed to the lever plate  354  (i.e. unable to rotate with respect to the lever plate  354 ), for example via a mortise and tenon joint or bonding with an adhesive. Also, the supporting member  353  is fixed to the lens barrel  35   a , with the other bottom face thereof, i.e. opposite to the face where the cylindrical projection  353   a  is provided, butted to a side wall of the lens barrel  35   a  accommodating the collimator lens  35  for the excitation light. In this state, the optical axis Ax 2  of the collimator lens  35  is perpendicular to the direction of the major axis of the lever plate  354 , and is torsionally oriented with respect to the same major axis. 
   Under the foregoing structure of lever plate  354  and the lens barrel  35   a  with respect to the supporting member  353 , the cylindrical projection  353   a  of the supporting member  353  constitutes a cylindrical projection protruding from the surface of the lever plate  354 . The cylindrical projection  353   a  protruding from the lever plate  354  is inserted into the elliptical hole  303  provided in the frame plate  30   a , as shown in  FIG. 7 . The direction of the major axis of the elliptical hole  303  is parallel to the horizontal bar  30   c , and an extension of the minor axis thereof perpendicularly intersects with the optical axis Ax 1 . Also, the length of the minor axis the elliptical hole  303  is substantially the same as the diameter of the cylindrical projection  353   a  of the supporting member  353  (more precisely, slightly longer). Accordingly, upon inserting the portion of the cylindrical projection  353   a  protruding from the lever plate  354  into the elliptical hole  303 , the cylindrical projection  353   a  can be made to rotate within the elliptical hole  303 , as well as to slide along the major axis of the elliptical hole  303 , i.e. in a horizontal direction. Fastening the cylindrical projection  353   a  inserted into the elliptical hole  303  with a third flanged screw  358 , the lever plate  354  and the lens barrel  35   a  attached to the supporting member  353  are supported by the frame plate  30   a.    
   Referring further to  FIG. 7 , the frame plate  30   a  is perforated with a pair of circular holes  301 ,  302  in addition to the elliptical hole  303 . The diameter of these circular holes  301 ,  302  is substantially the same as that of the cylindrical projection  351   c  of the first adjuster  351 , i.e. substantially the same as that of the cylindrical projection  352   c  of the second adjuster  352  (more precisely, slightly larger). In addition, the respective centers of the circular holes  301 ,  302  are aligned in a direction parallel to the horizontal bar  30   c , together with the center of the elliptical hole  303 . 
   The first circular hole  301  receives the cylindrical projection  351   c  of the first adjuster  351 , which has its cam plate  351   b  inserted to the first elliptical hole  354   a  of the lever plate  354 . Then, a first flanged screw  356  is screwed into the cylindrical projection  351   c  inserted to the first circular hole  301 , thus to make the first adjuster  351  press the lever plate  354  against the frame plate  30   a.    
   Likewise the circular hole  302 , located between the first circular hole  301  and the elliptical hole  303 , receives the cylindrical projection  352   c  of the second adjuster  352 , which has its cam plate  352   b  inserted to the second elliptical hole  354   b  of the lever plate  354 . Then, a second flanged screw  357  is screwed into the cylindrical projection  352   c  inserted to the second circular hole  302 , thus to make the second adjuster  352  press the lever plate  354  against the frame plate  30   a.    
   The adjustment mechanism  350  thus constructed operates as described below. Here,  FIGS. 8 and 9  are perspective views of the adjustment mechanism  350  and the respective optical systems, viewed from different angles from  FIG. 6 . 
   In the event that, upon completing the assembly of the light source unit  30  or receipt of a repair request therefor, the optical axis Ax 2  of the collimator lens  35  serving as the optical system for the excitation light has proved to be not coaxial with the optical axis Ax 1  of the afocal optical system  32  and the condenser lens  33  in the section beyond the dichroic mirror  36 , an operator can utilize the adjustment mechanism  350  to adjust a position and orientation of the optical axis Ax 2 . Specifically, the operator can slightly loosen the flanged screws  356  to  358 , and manipulate the knob  351   a  of the first adjuster  351  and the knob  352   a  of the second adjuster  352 , so as to adjust a position and orientation of the optical axis Ax 2 . 
     FIG. 8  is a fragmentary perspective view for explaining a movement of the optical axis Ax 2  caused by manipulation of the first adjuster  351 . When the operator holds and rotates the knob  351   a  of the first adjuster  351 , the cam plate  351   b  of the first adjuster  351  performs an eccentric rotation inside the first elliptical hole  354   a  of the lever plate  354 , so as to push the first elliptical hole  354   a  upward or downward parallel to the frame plate  30   a . At this stage, since the cam plate  352   b  of the second adjuster  352  is rotatable and slidable within the second elliptical hole  354   b , the lever plate  354  is caused to rotate around the central axis of the supporting member  353 . Accordingly, the optical axis Ax 2  of the collimator lens  35 , which is fixed to the lever plate  354  via the supporting member  353  and the lens barrel  35   a , also rotates around the central axis of the supporting member  353 , thus to vary an inclination of the optical axis Ax 2  with respect to the vertical. Since the optical axis Ax 2  corresponds to the section bent by the dichroic mirror  36 , such variation in inclination with respect to the vertical is equivalent to a variation in inclination with respect to the optical axis Ax 1 . In this way, the operator can adjust an inclination of the optical axis Ax 2  with respect to the optical axis Ax 1 , by manipulating the first adjuster  351 . 
     FIG. 9  is a fragmentary perspective view for explaining a movement of the optical axis Ax 2  caused by manipulation of the second adjuster  352 . When the operator holds and rotates the knob  352   a  of the second adjuster  352 , the cam plate  352   b  of the second adjuster  352  performs an eccentric rotation inside the second elliptical hole  354   b  of the lever plate  354 , so as to push the second elliptical hole  354   b  leftward or rightward according to the orientation of  FIG. 9 , parallel to the frame plate  30   a . At this stage, since the cylindrical projection  353   a  of the supporting member  353  is rotatable and slidable within the elliptical hole  303  of the frame plate  30   a , the central axis of the supporting member  353  is parallelly displaced in a horizontal direction. Besides, since the cam plate  351   b  of the first adjuster  351  is rotatable and slidable within the first elliptical hole  354   a , the lever plate  354  is also parallelly displaced in a horizontal direction, while maintaining the current inclination with respect to the horizontal. Accordingly, the optical axis Ax 2  of the collimator lens  35 , which is fixed to the lever plate  354  via the supporting member  353  and the lens barrel  35   a , is also parallelly displaced in a horizontal direction. Since the optical axis Ax 2  corresponds to the section bent by the dichroic mirror  36 , such parallel displacement in a horizontal direction is equivalent to a variation in distance from the optical axis Ax 1 . In this way, the operator can adjust a position of the optical axis Ax 2  with respect to the optical axis Ax 1 , by manipulating the second adjuster  352 . 
   In addition, changing a screwing depth of the screw  37   b  disposed in the lower border portion of the stage  37  causes a variation in inclination of the dichroic mirror  36  with respect to the optical axis Ax 1 , as stated earlier. Accordingly, the operator can adjust an elevation angle or a depression angle of the optical axis Ax 2  with respect to the optical axis Ax 1 , by adjusting a screwing depth of the screw  37   b.    
   In the adjustment mechanism  350  thus constructed, when the cam  351   b  of the first adjuster  351  is rotated, this cam  351   b  pushes the elliptical hole  354   a  of the lever plate  354  upward or downward parallel to the frame plate  30   a , while allowing the cam  352   b  of the second adjuster  352  to rotate and slide inside the elliptical hole  354   b  of the lever plate  354 . This causes the lever plate  354  to rotate around a central axis of the cylindrical projection, which in turn causes the optical axis Ax 2  of an excitation light optical system (i.e. the collimator lens  35 ) to rotate around the central axis thereof. Such rotation creates a change in inclination of the optical axis of the excitation light optical system with respect to the optical axis of the white light optical system, in a section beyond an optical path merging device (i.e. the dichroic mirror  36 ). Accordingly, manipulating the first adjuster  351  enables adjusting an inclination of the optical axis of the excitation light optical system, with respect to the optical axis of the white light optical system. 
   Likewise, when the cam  352   b  of the second adjuster  352  is rotated, the cam  352   b  pushes the elliptical hole  354   b  of the lever plate  354  leftward or rightward parallel to the frame plate  30   a , while allowing the cylindrical projection  353   a  of the lever plate  354  to rotate and slide inside the elliptical hole  303  of the frame plate  30   a , and also the cam  351   b  of the first adjuster  351  to rotate and slide inside the elliptical hole  354   a  of the lever plate  354 . This causes the lever plate  354  to be parallelly displaced along a direction of the major axis of the elliptical hole  354   a  of the frame plate, and hence the central axis of the cylindrical projection  353   a  of the lever plate  354  is also parallelly displaced in the same direction, which in turn causes a parallel displacement of the optical axis Ax 2  of the excitation light optical system, again in the same direction. Such parallel displacement creates a change in distance of the optical axis Ax 2  of the excitation light optical system from the optical axis of the white light optical system, in a section beyond the optical path merging device. Accordingly, manipulating the second adjuster  352  enables adjusting a position of the optical axis of the excitation light optical system with respect to the optical axis of the white light optical system. 
   As described above, the adjustment mechanism  350  according to the embodiment of the present invention allows adjusting an inclination or a position of an optical axis Ax 2  of a collimator lens  35  with respect to an optical axis Ax 1  of a white light optical system, in the light source unit  30  provided with the collimator lens  35  that converts the excitation light emitted by an excitation light emitting device  34  into a collimated beam and emits such beam to a dichroic mirror  36 . 
   Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. 
   For example, the elliptical shape of each of the elliptical holes  303 ,  354   a , and  354   b  may be replaced with various types of oblong shapes made by elongating a square shape or a circular shape. 
   The first adjuster  351  and the second adjuster  352  may be configured to have a groove (slot) or a hole such as a cross recess, a hexagonal or star socket, in which a screwdriver tip can be inserted so that the first and the second adjusters can be rotated by the screwdriver. 
   The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2004-062043, filed on Mar. 5, 2004, which is expressly incorporated herein by reference in its entirety.