Patent Publication Number: US-2022212313-A1

Title: End face polishing device for optical fiber ferrule

Description:
TECHNICAL FIELD 
     The present invention relates to an end face polishing device for an optical fiber ferrule for polishing an end face of an optical fiber ferrule. 
     BACKGROUND ART 
     In order to transmit signals while reducing optical connection loss at the connection portion between optical fibers, it is necessary to polish the end face of the optical fibers. In general, at a tip part of both optical fibers to be connected, the optical fiber made of a glass is covered with a ferrule made of a ceramic or a resin. Thus, the end face of the optical fiber and the end face of the ferrule are simultaneously polished. Consequently, when the connection portions are abutted against each other, the optical fibers are in contact with each other without a gap and the signals can be transmitted while reducing the optical connection loss. 
     As for the device for polishing the end face of the optical fiber ferrule, the device described in Patent Document 1 is known. An end face polishing device for an optical fiber ferrule of Patent Document 1 includes a plate-shaped polishing holder to which an optical fiber ferrule can be detachably attached, a holding unit for holding and releasing the polishing holder in an approximately horizontal state, a turntable arranged below the polishing holder held by the holding unit so that turntable faces the end face of the optical fiber ferrule, a polishing plate replaceably installed on the turntable, and a rotation unit for rotating and revolving the turntable for polishing the end face of the optical fiber ferrule by the polishing plate. 
     In the end face polishing device for the optical fiber ferrule of Patent Document 1, when the turntable is rotated and revolved, the polishing plate installed on the turntable performs a composite circular motion formed by combining the rotation and the revolution and the end face of the optical fiber ferrule attached to the polishing holder is appropriately and precisely polished by the polishing plate performing the composite circular motion. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-122424 
     Patent Document 2: Japanese Unexamined Patent Application Publication No. 2008-62376 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     When the end face of the optical fiber ferrule is polished, the polishing plate on the turntable is gradually replaced from a coarse one to a fine one to perform the polishing stepwisely (e.g., coarse polishing, semi-finish polishing and finish polishing). In order to replace the polishing plate, it is necessary to detach the already used polishing plate from the turntable and attach a new polishing plate to the turntable. As a part of automation of the process of polishing the end face of the optical fiber ferrule, there is a desire to automate the process of replacing the polishing plate. 
     Here, the turntable on which the polishing plate is installed is rotated and further revolved. Thus, the turntable is not always stopped at the same revolution position when the turntable is stopped. Accordingly, in order to automatically replace the polishing plate on the turntable, it is necessary to move a hand of a multi-axis robot or the like in accordance with the revolution position of the stopped turntable. For example, it is possible to perform the above described operation using a multi-axis robot with a camera by detecting the revolution position with the camera when the turntable is stopped, moving the hand of the multi-axis robot to the detected position and picking up the polishing plate on the turntable to replace it (shown in Patent Document 2). 
     However, the system of controlling the position of the hand by using the multi-axis robot with the camera is expensive. Thus, the manufacturing cost increases. In addition, in order to detect the revolution position of the turntable by the camera, it is necessary to photograph the turntable from the above of the turntable by the camera. However, immediately after the polishing is finished, the upper part of the turntable is covered with the polishing holder to which the optical fiber ferrule is installed. Therefore, the revolution position of the turntable can be detected by the camera only after the polishing holder is detached. Thus, the tact time for replacing the polishing plate is increased. 
     Considering the above described situation, the present invention aims for providing an end face polishing device for an optical fiber ferrule capable of easily replacing the polishing plate at low cost in a short time when the polishing of the end face of the optical fiber ferrule is automated. 
     Means for Solving the Problem 
     For achieving the above described purpose, the present invention provides an end face polishing device for an optical fiber ferrule including: a holding unit configured to hold and release a polishing holder to which an optical fiber ferrule can be detachably attached; a turntable arranged below the polishing holder held by the holding unit, a polishing plate being replaceably installed on the turntable; a moving unit configured to elevate and lower the turntable so that the polishing plate installed on the turntable is contacted with or separated from an end face of the optical fiber ferrule attached to the polishing holder held by the holding unit; a rotation unit having a revolution mechanism configured to revolve the turntable and a rotation mechanism configured to rotate the turntable separated from a revolution movement of the turntable revolved by the revolution mechanism, the turntable being revolved and rotated for polishing the end face of the optical fiber ferrule attached to the polishing holder by the polishing plate installed on the turntable, and a controller having functions of revolving the turntable by the revolution mechanism to move the turntable to a predetermined revolution position and rotating the turntable by the rotation mechanism to move the turntable to a predetermined rotation position after the end face of the optical fiber ferrule and the polishing plate are separated from each other by the moving unit, wherein the controller has a function of rotating the turntable by the rotation mechanism while the turntable is kept in the predetermined revolution position. 
     In the end face polishing device for the optical fiber ferrule of the present invention, the turntable may have a plurality of depressed portions separated from each other with an interval in a circumferential direction of the polishing plate installed on the turntable for picking up the polishing plate from the turntable. 
     In the end face polishing device for the optical fiber ferrule of the present invention, the rotation unit may include a revolution position reference portion for determining the predetermined revolution position of the turntable and a rotation position reference portion for determining the predetermined rotation position the turntable, and the controller may include a revolution sensor for detecting the revolution position reference portion and a rotation sensor for detecting the rotation position reference portion. 
     In the end face polishing device for the optical fiber ferrule of the present invention, the revolution position reference portion may be a first protrusion or a first recess, the revolution sensor may be a non-contact proximity sensor for detecting a gap between the revolution sensor and the first protrusion or the first recess forming the revolution position reference portion, the rotation position reference portion may be a second protrusion or a second recess, the rotation sensor may be a non-contact proximity sensor for detecting a gap between the rotation sensor and the second protrusion or the second recess forming the rotation position reference portion. 
     Effects of the Invention 
     The following effects can be obtained by the end face polishing device for the optical fiber ferrule of the present invention. 
     (1) After the polishing is finished, the turntable is moved to the predetermined (preliminarily determined) revolution position by the controller. Thus, the revolution position of the polishing plate on the turntable is uniquely determined. 
     Accordingly, the operation of replacing the polishing plate can be performed by using a uniaxial robot or the like having a hand capable of moving to a fixed position. It is not necessary to use an expensive multi-axis robot with a camera. Thus, the polishing plate can be replaced easily at low cost. 
     (2) After the polishing is finished, the operation of moving the turntable to the predetermined revolution position is performed by actuating the rotation unit. Thus, the operation can be also performed even when the upper part of the turntable is covered with the polishing holder to which the optical fiber ferrule is attached. 
     Accordingly, the operation of replacing the polishing plate can be performed in a shorter time compared to the case of using the multi-axis robot or the like with a camera where the revolution position of the turntable should be checked after removing the polishing holder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a state that a polishing holder is held on an end face polishing device for an optical fiber ferrule concerning an embodiment of the present invention. 
         FIG. 2  is a perspective view showing a state that the polishing holder is detached from the end face polishing device of  FIG. 1 . 
         FIG. 3  is a vertical cross-sectional view of the end face polishing device of  FIG. 1 . 
         FIG. 4  is a perspective cross-sectional view showing a revolution mechanism, a rotation mechanism, a revolution position reference portion, a revolution sensor, a rotation position reference portion and a rotation sensor which serve as a rotation unit for rotating and revolving the turntable. 
         FIG. 5A  is a partial side cross-sectional view showing a state that the polishing plate installed on the turntable is lowered and separated from the end face of the optical fiber ferrule attached to the polishing holder.  FIG. 5B  is a partial side cross-sectional view showing a state that the polishing plate installed on the turntable is elevated and contacted with the end face of the optical fiber ferrule attached to the polishing holder. 
         FIG. 6A  is an explanatory drawing showing a rotation of the turntable.  FIG. 6B  is an explanatory drawing showing a revolution of the turntable.  FIG. 6C  is an explanatory drawing showing a composite circular motion formed by combining the rotation and the revolution. 
         FIGS. 7A to 7C  are explanatory drawings showing the polishing plate and the turntable of a first modified example.  FIG. 7A  is a side cross-sectional view of the polishing plate.  FIG. 7B  is a side cross-sectional view where the polishing plate is installed on the turntable.  FIG. 7C  is a side cross-sectional view where the polishing plate and the turntable are exploded. 
         FIG. 8A  is a side cross-sectional view showing the polishing plate of a second modified example.  FIG. 8B  is a side cross-sectional view showing the polishing plate of a third modified example. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     Hereafter, preferred embodiments of the present invention will be explained in detail with reference to the attached drawings. The dimensions, materials and other specific values shown in the embodiments merely show examples for facilitating the understanding of the invention. Unless particularly mentioned, these values do not limit the present invention. Note that the same reference numeral is assigned to the element having the same function and configuration in the specification and the drawings. Thus, a repeated explanation is omitted. In addition, the drawing of the element not directly related to the present invention is omitted. 
     Outline of End Face Polishing Device for Optical Fiber Ferrule 
     As shown in  FIG. 1 , an end face polishing device  1  for an optical fiber ferrule (hereafter, also referred to as an end face polishing device) concerning an embodiment of the present invention includes a holding unit (holding means)  4  configured to hold and release a polishing holder  3  to which optical fiber ferrules can be detachably attached. The polishing holder  3  held on the holding unit  4  is provided with optical fiber ferrule fixing jigs  2   a  for fixing and releasing the optical fiber ferrules. As shown in  FIG. 2 , the end face polishing device  1  includes a turntable  5  arranged below the polishing holder  3  held by the holding unit  4 . A polishing plate  6  can be replaceably installed on the upper surface of the turntable  5 . 
     As shown in  FIG. 3 , the end face polishing device  1  includes a rotation unit  7  arranged below the turntable  5  for rotating and revolving the turntable  5 . When the rotation unit  5  is rotated and revolved by the rotation unit  7 , the polishing plate  6  installed on the turntable  5  polishes an end face of optical fiber ferrules  2  attached to the polishing holder  3 . As shown in  FIG. 4 , the end face polishing device  1  includes a controller  8  for operating the rotation unit  7  to at least move the turntable  5  to a predetermined revolution position after the polishing using the rotation unit  7  is finished. 
     Furthermore, as shown in  FIG. 3 ,  FIG. 5A  and  FIG. 5B , the end face polishing device  1  includes a moving unit  9  for relatively moving the turntable  5  with respect to the polishing holder  3  held by the holding unit  4  so that the turntable  5  approaches to and separates from the polishing holder  3 . The moving unit  9  is configured to elevate and lower the turntable  5  so that the polishing plate  6  installed on the turntable  5  is contacted with or separated from the end face (lower surface) of the optical fiber ferrules  2  fixed to the polishing holder  3  by the fixing jigs  2   a.  As shown in  FIG. 5B , the controller  8  operates the rotation unit  7  in a state that the polishing plate  6  is contacted with the end face of the optical fiber ferrule  2 . Consequently, the end face of the optical fiber ferrules  2  is polished. After the polishing is finished by the polishing plate  6 , the turntable  5  is lowered by the moving unit  9  shown in  FIG. 3 . As a result, as shown in  FIG. 5A , the polishing plate  6  is separated from the end face of the optical fiber ferrules  2 . In that state, the controller  8  operates the rotation unit  7  to move the turntable  5  to the predetermined revolution position. 
     Hereafter, each component of the end face polishing device  1  will be explained. 
     Holding Unit  4   
     As shown in  FIG. 1  and  FIG. 2 , the holding unit  4  for holding and releasing the polishing holder  3  is provided on the upper surface of a base plate  10  which is a part of a frame of the end face polishing device  1 . The polishing holder  3  held by the holding unit  4  is formed of a plate body. As shown in  FIG. 3 , a plurality of optical fiber ferrules  2  is detachably attached to the polishing holder  3  by the fixing jigs  2   a  in a state that the end face to be polished is directed downward. As shown in  FIG. 1 , the optical fiber ferrules  2  are arranged in a circular shape with an interval in a circumferential direction by the fixing jigs  2   a  in the present embodiment. However, the arrangement of the optical fiber ferrules  2  is not limited to the circular shape. 
     As shown in  FIG. 1  to  FIG. 3 , the holding unit  4  includes: four columnar bodies  4   a  vertically disposed on four corners of the upper surface of the base plate  10  of the end face polishing device  1 ; mounting stands  4   b  provided on the columnar bodies  4   a  to place the four corners of the polishing holder  3  on the mounting stands  4   b;  and levers  4   c  for pressing the polishing holder  3  placed on the mounting stands  4   b  from the above. The levers  4   c  are pivoted upward and downward by air pressure or the like. When the levers  4   c  are pivoted downward, the levers  4   c  presses the polishing holder  3  toward the mounting stands  4   b  to hold the polishing holder  3  (shown in  FIG. 1 ). When the levers  4   c  are pivoted upward, the polishing holder  3  is released (shown in  FIG. 2 ). The released polishing holder  3  can be detached upward. 
     Turntable  5   
     As shown in  FIG. 3 , the turntable  5  is arranged below the polishing holder  3  held by the holding unit  4  so that the turntable  5  faces the end face of the optical fiber ferrules  2  attached to the polishing holder  3  by the fixing jigs  2   a.  As shown in  FIG. 2 , the turntable  5  is formed in an approximately circular plate shape. As shown in  FIG. 3 , the turntable  5  is approximately horizontally placed on a thrust ring  11  arranged on the upper surface of the base plate  10  of the end face polishing device  1 . 
     As shown in  FIG. 3 , the thrust ring  11  supports the lower surface of the turntable  5  by a ring-shaped plane. The thrust ring  11  is configured to be elevated and lowered by the moving unit  9 . The thrust ring  11  can be slid with respect to the lower surface of the turntable  5  when the turntable  5  is rotated and revolved by the rotation unit  7  shown in  FIG. 3  in a state that the thrust ring  11  is elevated by the moving unit  9  and the polishing plate  6  is pressed to the end face of the optical fiber ferrules  2  as shown in  FIG. 5B . By using the above described thrust ring  11 , the pressing force from the polishing plate  6  to the end face of the optical fiber ferrules  2  can be maintained while allowing the turntable  5  to rotate and revolve. 
     As shown in  FIG. 3 , a recess  5   a  having a circular shape is formed on the upper surface of the turntable  5  so that the polishing plate  6  is replaceably installed in the recess  5   a.  A wall  5   b  is formed in a ring shape on a periphery of the recess  5   a  for catching water and polishing agent supplied to the polishing plate  6  and preventing them from being scattered to the outward by centrifugal force during the polishing. 
     Polishing Plate  6   
     As shown in  FIG. 5A , the polishing plate  6  is replaceably installed in the recess  5   a  of the turntable  5 . The polishing plate  6  includes a pad  6   a  formed in a thin circular plate shape corresponding to the shape of the recess  5   a  and a polishing film  6   b  attached to the upper surface of the pad  6   a.  The polishing plate  6  is replaceably installed in the recess  5   a  from the above. 
     An elastic material such as a rubber and a resin can be used as the material of the pad  6   a.  Consequently, as shown in  FIG. 5B , when the turntable  5  is elevated by the moving unit  9  (shown in  FIG. 3 ) and the polishing film  6   b  is pressed to an end face  2   a  of the optical fiber ferrules  2 , the pad  6   a  is slightly bent and the polishing film  6   b  is pressed to the end face  2   a  of the optical fiber ferrules  2  by a reaction force of the bent pad  6   a.  Thus, a spherical surface polishing becomes possible. 
     The polishing film  6   b  is a part which substantially polishes the end face of the optical fiber ferrules  2 . Plurality kinds of polishing films  6   b  having coarse particles and fine particles is prepared for the polishing. When the end face of the optical fiber ferrules  2  is polished by alternatively replacing the plurality kinds of polishing films, the end face of the optical fiber ferrules  2  can be stepwisely polished (e.g., coarse polishing, semi-finish polishing and finish polishing). 
     Rotation Unit  7   
     As shown in  FIG. 3 , the rotation unit  7  for rotating and revolving the turntable  5  is arranged below the turntable  5 . The rotation unit  7  includes a revolution mechanism  12  configured to revolve the turntable  5  and a rotation mechanism  13  configured to rotate the turntable  5  separated from a revolution movement of the turntable  5  revolved by the revolution mechanism  12 . 
     Revolution Mechanism  12   
     As shown in  FIG. 3  and  FIG. 4 , the revolution mechanism  12  includes: a revolution motor  12   a  attached to the lower surface of the base plate  10  of the end face polishing device  1 ; a revolution output shaft  12   b  extended upward from the revolution motor  12   a;  a revolution eccentric arm  12   c  horizontally attached to the revolution output shaft  12   b;  and a revolution drive shaft  12   d  extended upward from the revolution eccentric arm  12   c.    
     As shown in  FIG. 3 , the revolution drive shaft  12   d  is inserted into a circular hole  5   c  formed on the lower surface of the turntable  5  so that the revolution drive shaft  12   d  can be freely slid in an axial direction and freely rotated in a circumferential direction. The position of the circular hole  5   c  of the turntable  5  (i.e., the position of the revolution drive shaft  12   d ) is located at (aligned with) a center of the circular turntable  5  when viewed from the above. 
     Rotation Mechanism  13   
     As shown in  FIG. 3  and  FIG. 4 , the rotation mechanism  13  includes: a rotation motor (self-rotation motor)  13   a  attached to the lower surface of the base plate  10  at the position neighboring the revolution motor  12   a;  a rotation output shaft (self-rotation output shaft)  13   b  extended upward from the rotation motor  13   a;  a pinion gear  13   c  attached to the upper part of the rotation output shaft  13   b;  and a rotation gear (self-rotation gear)  13   d  engaged with the pinion gear  13   c.  As shown in  FIG. 3 , the rotation gear  13   d  is rotatably attached to a recess  10   a  formed on the base plate  10 . 
     As shown in  FIG. 4 , the rotation gear  13   d  is formed in a ring shape, an externally toothed gear to be engaged with the pinion gear  13   c  is formed on an outer periphery of the ring, the revolution eccentric arm  12   c  attached to the revolution output shaft  12   b  is housed inside the ring so that the revolution output shaft  12   b  can be rotated. As shown in  FIG. 3 , a center of the rotation gear  13   d  is located at (aligned with) a center of the revolution output shaft  12   b.    
     As shown in  FIG. 3  and  FIG. 4 , the rotation mechanism  13  includes: pins  13   e  extended upward from the rotation gear  13   d  and rotatably attached to the rotation gear  13   d;  rotation eccentric arms (self-rotation eccentric arms)  13   f  horizontally attached to the upper part of the pins  13   e;  and a rotation drive shaft (self-rotation drive shaft)  13   g  attached to be extended upward from the rotation eccentric arms  13   f . Three pins  13   e  are provided on the upper surface of the rotation gear  13   d  with an equal interval in the present embodiment. However, the number of the pins  13   e  can be one, two, four or more. 
     As shown in  FIG. 3 , the rotation drive shafts  13   g  are inserted into a circular hole  5   d  formed on the lower surface of the turntable  5  so that the rotation drive shafts  13   g  can be freely slid in an axial direction and freely rotated in a circumferential direction. As shown in  FIG. 4 , the interval between each of the rotation drive shafts  13   g  of the rotation eccentric arms  13   f  and each of the pins  13   e  is equal to the interval between the revolution drive shaft  12   d  of the revolution eccentric arm  12   c  and the revolution output shaft  12   b.    
     Rotation and Revolution of Turntable  5   
     In the rotation mechanism  13  explained by using  FIG. 3  and  FIG. 4 , when the rotation motor  13   a  is driven, the rotation gear  13   d  is rotated (self-rotated) around the revolution output shaft  12   b  by the pinion gear  13   c.  Consequently, the turntable  5  is rotated as shown in  FIG. 6A . The rotation (self-rotation) means the movement that the turntable  5  itself is rotated around a central axis of the turntable  5  while the position of the turntable  5  is not changed. 
     When the revolution motor  12   a  shown in  FIG. 3  and  FIG. 4  is driven, the revolution drive shaft  12   d  is rotated (revolved) around the revolution output shaft  12   b.  Consequently, the turntable  5  is revolved as shown in  FIG. 6B . The revolution means the movement that the entire turntable  5  is rotated (revolved) with a predetermined radius (offset). As shown in  FIG. 4 , the length of the offset is equal to the distance between the rotation drive shafts  13   g  of the rotation eccentric arms  13   f  and the pins  13   e  and also equal to the distance between the revolution drive shaft  12   d  of the revolution eccentric arm  12   c  and the revolution output shaft  12   b.    
     The rotation motor  13   a  and the revolution motor  12   a  are controlled by the controller  8  so that the rotating speed ratio between the rotation and revolution becomes approximately “rotation:revolution=1:100,” for example. Namely, the turntable  5  is revolved approximately 100 times while the turntable  5  is rotated one time. Consequently, as shown in  FIG. 6C , one point on the turntable  5  performs a composite circular motion formed by combining the rotation and the revolution. Although the direction of the rotation shown in  FIG. 6A  is opposite to the direction of the revolution shown in  FIG. 6B , the direction of the rotation can be same as the direction of the revolution. 
     Controller  8   
     As shown in  FIG. 4 , the end face polishing device  1  includes the controller  8  for revolving and rotating the turntable  5  by the revolution mechanism  12  and the rotation mechanism  13  both constituting the rotation unit  7  and at least moves the turntable  5  to a predetermined revolution position after the end face of the optical fiber ferrules  2  is polished. Namely, the revolution mechanism  12  for revolving the turntable  5  includes a revolution position reference portion  12   e  for determining the predetermined revolution position of the turntable  5  and the controller  8  includes a revolution sensor  8   a  for detecting the revolution position reference portion  12   e.    
     As shown in  FIG. 4 , the revolution position reference portion  12   e  is a protrusion (or a recess) formed on a lower surface of the revolution eccentric arm  12   c,  and the revolution sensor  8   a  is a non-contact proximity sensor for detecting a gap between the revolution sensor  8  and the protrusion (or the recess) forming the revolution position reference portion  12   e.  Since the non-contact proximity sensor is used for the revolution sensor  8   a,  the revolution position reference portion  12   e  (protrusion) can be appropriately detected even in a condition where oil and grease are present in the rotation gear  13   d  or the like forming the rotation unit  7 . 
     An induction-type proximity sensor is used for the non-contact proximity sensor as the revolution sensor  8   a  shown in  FIG. 4  since the protrusion (revolution position reference portion  12   e ) of the revolution eccentric arm  12   c  to be detected is a metal. The induction-type proximity sensor detects the variation of impedance due to the eddy current generated in the metal to be detected by generating an AC magnetic field on a detection coil formed on the sensor. The above described revolution sensor  8   a  is located below the revolution eccentric arm  12   c,  attached to the base plate  10 , and connected to a control unit  8   b  (e.g., computer) which forms a main part of the controller  8 . 
     As shown in  FIG. 4 , the control unit  8   b  is connected to the revolution motor  12   a.  The control unit  8   b  has a function of controlling the revolution angle of the revolution output shaft  12   b  of the revolution motor  12   a  based on the position of the revolution position reference portion  12   e  detected by the revolution sensor  8   a  to move the turntable  5  to the predetermined revolution position. The revolution motor  12   a  is a brushless motor. Thus, the revolution angle of the revolution output shaft  12   b  can be precisely controlled by counting the pulse during the revolution. Consequently, the turntable  5  can be precisely moved to the predetermined revolution position. 
     In addition, the controller  8  has a function of moving the turntable  5  to a predetermined rotation position after the polishing using the rotation unit  7  (revolution mechanism  12 , rotation mechanism  13 ) is finished. Namely, as shown in  FIG. 4 , the rotation mechanism  13  for rotating the turntable  5  includes a plurality of rotation position reference portions  13   h  (e.g., three parts at 120° interval) for determining the predetermined rotation position of the turntable  5  and the controller  8  includes a rotation sensor  8   c  for detecting the rotation position reference portions  13   h.    
     As shown in  FIG. 4 , the rotation position reference portions  13   h  are recesses (or protrusions) formed on the lower surface of the rotation gear  13   d,  and the rotation sensor  8   c  is a non-contact proximity sensor for detecting a gap between the rotation sensor  8   c  and the recesses (or the protrusions) forming the rotation position reference portions  13   h.  Since the non-contact proximity sensor is used for the rotation sensor  8   c,  the rotation position reference portions  13   h  (recesses) can be appropriately detected even in a condition where oil and grease are present in the rotation gear  13   d  or the like forming the rotation unit  7 . 
     Same as the revolution sensor  8   a,  an induction-type proximity sensor is used for the non-contact proximity sensor as the rotation sensor  8   c  shown in  FIG. 4  since the recesses (rotation position reference portions  13   h ) of the rotation gear  13   d  to be detected are made of a metal. The above described rotation sensor  8   c  is located below the rotation gear  13   d,  attached to the base plate  10 , and connected to the control unit  8   b  (e.g., computer). 
     As shown in  FIG. 4 , the control unit  8   b  is connected to the rotation motor  13   a.  The control unit  8   b  has a function of controlling the rotation angle of the rotation output shaft  13   b  of the rotation motor  13   a  based on the position of the rotation position reference portions  13   h  detected by the rotation sensor  8   a  to move the turntable  5  to the predetermined rotation position. The rotation motor  13   a  is a brushless motor. Thus, the rotation angle of the rotation output shaft  13   b  can be precisely controlled by counting the pulse during the rotation. Consequently, the turntable  5  can be precisely moved to the predetermined rotation position. 
     Moving Unit  9   
     As shown in  FIG. 3 , the end face polishing device  1  includes the moving unit  9  configured to elevate and lower the turntable  5 . The moving unit  9  elevates and lowers the turntable  5  so that the polishing plate  6  installed on the turntable  5  is contacted with or separated from the end face of the optical fiber ferrules  2  attached by the fixing jigs  2   a  to the polishing holder  3  held by the holding unit  4 . 
     As shown in  FIG. 3 , the moving unit  9  includes: a support plate  16  hung from the lower surface of the base plate  10  of the end face polishing device  1  via a rod  15 ; an air cylinder  17  attached to the support plate  16 ; an elevating/lowering plate  20  connected to a piston  18  located in the air cylinder  17  via a connection member  19 ; a shaft  21  attached to be extended upward from the elevating/lowering plate  20 ; and a thrust ring  11  attached to the upper end of the shaft  21 . The shaft  21  is inserted through a hole formed on the base plate  10  via a bush  22  and smoothly guided by the bush  22  in a vertical direction. As described above, the turntable  5  is placed on the upper surface of the thrust ring  11 . 
     As shown in  FIG. 3 , in a state that the air pressure is not supplied to the air cylinder  18 , a lower surface of the thrust ring  11  is seated on the upper surface of the base plate  10  and the polishing plate  6  on the turntable  5  placed on the thrust ring  11  is separated from the end face of the optical fiber ferrules  2  attached by the fixing jigs  2   a  to the polishing holder  3  held by the holding unit  4  (shown in  FIG. 5A ). When a predetermined air pressure is applied to the air cylinder  17 , the piston  18 , the connection member  19 , the elevating/lowering plate  20  and the shaft  21  are elevated, the thrust ring  11  is separated upward from the base plate  10 , and the polishing plate  6  on the turntable  5  placed on the thrust ring  11  is pressed to the end face of the optical fiber ferrules  2  attached to the polishing holder  3  held by the holding unit  4  (shown in  FIG. 5B ). 
     The air is supplied from a not-illustrated air pump to the air cylinder  17  shown in FIG.  3 . The internal pressure is controlled by a variable regulator. When the variable regulator is controlled by the control unit  8   b  to release the internal pressure of the air cylinder, as shown in  FIG. 3 , the thrust ring  11  is seated on the base plate  10  by the action of the gravity and the polishing plate  6  is separated from the end face of the optical fiber ferrules  2 . When the predetermined internal pressure is supplied to the air cylinder  17  from the above described state, the thrust ring  11  is moved upward from the base plate  10  and the polishing plate  6  is pressed to the end face of the optical fiber ferrules  2 . The pressing force of the polishing plate  6  to the end face of the optical fiber ferrules  2  can be adjusted by controlling the internal pressure of the air cylinder  17  by the control unit  8   b.    
     The control unit  8   b  shown in  FIG. 3  has a function of separating the polishing plate  6  from the end face of the optical fiber ferrules  2  as shown in  FIG. 5A  by releasing the internal pressure of the air cylinder  17  and moving the turntable  5  to the predetermined revolution position by the revolution mechanism  12  and moving the turntable  5  to the predetermined rotation position by the rotation mechanism  13  after the turntable  5  is revolved and rotated by the revolution mechanism  12  and the rotation mechanism  13  both constituting the rotation unit  7  to polish the end face of the optical fiber ferrules  2 . The movement of the turntable  5  to the predetermined revolution position made by the revolution mechanism  12  and the movement of the turntable  5  to the predetermined rotation position made by the rotation mechanism  13  can be simultaneously performed. It is also possible to perform one of them first and then perform the other. 
     Operations and Effects 
     The following effects can be obtained from the end face polishing device  1  for the optical fiber ferrules  2  concerning the present embodiment having the above described configurations. 
     After the end face of the optical fiber ferrules  2  is polished by rotating and revolving the turntable  5  by the rotation unit  7  (revolution mechanism  12 , rotation mechanism  13 ) shown in  FIG. 3  and  FIG. 4 , the turntable  5  is moved to the predetermined revolution position and rotation position by the controller  8 . Thus, the revolution position and the rotation position of the polishing plate  6  on the turntable  5  are uniquely determined after the polishing. Accordingly, the operation of replacing the polishing plate  6  can be performed from the above by using a uniaxial robot or the like having a hand capable of moving to a fixed position. It is not necessary to use an expensive multi-axis robot with a camera. Thus, the polishing plate  6  can be replaced easily at low cost. 
     For more details, in the present embodiment, three depressed portions  5   e  are formed on the turntable  5  at 120° interval as shown in  FIG. 2  so that the tip of the hand of the uniaxial robot or the like can be inserted into the depressed portions  5   e.  Three hands inserted into each of the depressed portions  5   e  pinch the outer periphery of the polishing plate  6  to hold a lower surface of the polishing plate  6  by nails located at the tip of each hand. Thus, the polishing plate  6  is picked up from the turntable  5  and replaced with another one. Note that two depressed portions  5   e  can be formed at 180° interval or four depressed portions  5   e  can be formed at 90° interval. In such a case, the number of the hands can be two or four in accordance with the number of the depressed portions  5   e.  When the number of the depressed portions  5   e  is increased, the polishing plate  6  can be held a circumferential direction with good balance. However, considering a balance with the cost, the number of the depressed portions  5   e  is preferably three. In addition, it is not necessary to match the number of the depressed portions  5   e  with the number of the hands. For example, the number of the depressed portions  5   e  can be a multiple of the number of the hands. When the above described configuration is adopted, it is enough if any of the positions of the depressed portions  5   e  are matched with the positions of the hands. Thus, for example, a merit of reducing the rotation angle can be obtained when the turntable  5  is rotated to the predetermined rotation position. 
     The operation of moving the turntable  5  to the predetermined revolution position and rotation position is controlled as follows. As shown in  FIG. 4 , the control unit  8   b  controls the revolution phase of the revolution output shaft  12   b  of the revolution motor  12   a  based on the output of the revolution sensor  8   a  detecting the revolution position reference portion (protrusion)  12   e.  In addition, the control unit  8   b  controls the rotation phase of the rotation output shaft  13   b  of the rotation motor  13   a  based on the output of the rotation sensor  8   c  detecting the rotation position reference portions (recesses)  13   h.  Thus, the turntable  5  can be moved even when the upper part of the turntable  5  is covered with the polishing holder  3  to which the optical fiber ferrules  2  are attached as shown in  FIG. 3 . Accordingly, the operation of replacing the polishing plate can be performed in a shorter time compared to the case of using the multi-axis robot or the like with a camera where the revolution position of the turntable  5  should be checked from the above after removing the polishing holder  3 . 
     Namely, when the conventional multi-axis robot or the like with a camera is used, after the polishing is finished it is necessary to detach the polishing holder  3  shown in  FIG. 3  and photograph the turntable  5  from the above with the camera. Only after the above described processes are finished, the hands of the multi-axis robot or the like can be moved to align with the revolution position and rotation position of the turntable  5  stopped at an arbitrary position after the polishing is finished. Thus, after the polishing holder  3  is detached and after the time of photographing with the camera and the time of performing a feedback control of the position of the hand based on it, the operation of replacing the polishing plate  6  is started by the hands of the multi-axis robot or the like. On the other hand, in the present embodiment, the turntable  5  can be moved to the predetermined revolution position and rotation position by operating the rotation unit  7  by the controller  8  after the polishing is finished even in a state that the upper part of the turntable  5  is covered with the polishing holder  3 . Thus, immediately after the polishing holder  3  is detached, the polishing plate  6  on the turntable  5  can be picked up and replaced with another one by moving the hands of the uniaxial robot or the like to the predetermined position. Accordingly, the operation of replacing the polishing plate  6  can be performed in a shorter time compared to the case of using the conventional multi-axis robot or the like with a camera. 
     As shown in  FIG. 5B , in a state that the polishing plate  6  on the turntable  5  is pressed to the end face of the optical fiber ferrules  2  attached to the polishing holder  3  held by the holding unit  4 , the turntable  5  is revolved and rotated by the rotation unit  7  (revolution mechanism  12 , rotation mechanism  13 ) and the end face of the optical fiber ferrules  2  is polished. After that, the turntable  5  is lowered by the moving unit  9  shown in  FIG. 3 , and the turntable  5  is moved to the predetermined revolution position and rotation position by the controller  8  in a state that the polishing plate  6  on the turntable  5  is separated downward from the end face of the optical fiber ferrules  2  as shown in  FIG. 5A . 
     As described above, after the polishing is finished, the turntable  5  is moved to the predetermined revolution position and rotation position in a state that the polishing plate  6  is separated from the end face of the optical fiber ferrules  2 . Therefore, the end face of the optical fiber ferrules  2  is prevented from being polished by the polishing plate  6  during the above described movement. Accordingly, unintentional polishing, which is not an ordinary polishing, can be avoided. Note that the moving unit  9  shown in  FIG. 3  can be modified to move the end face of the optical fiber ferrules  2  upward with respect to the turntable  5  contrary to the present embodiment where the turntable  5  is moved downward with respect to the end face of the optical fiber ferrules  2 . For example, it is possible to eliminate the mechanism of elevating and lowering the turntable  5  from the moving unit  9  and to vertically move the columnar bodies  4   a  with respect to the base plate  10  instead so that the polishing holder  3  held on the columnar bodies  4   a  by the levers  4   c  is elevated and lowered with respect to the turntable  5 . 
     As shown in  FIG. 4 , the rotation unit  7  includes the revolution mechanism  12  configured to revolve the turntable  5  and the rotation mechanism  13  configured to rotate the turntable  5  separated from a revolution movement of the turntable  5  revolved by the revolution mechanism  12 , and the controller  8  has functions of revolving the turntable  5  by the revolution mechanism  12  to move the turntable  5  to a predetermined revolution position and rotating the turntable  5  by the rotation mechanism  13  to move the turntable  5  to a predetermined rotation position after the polishing using the rotation unit  7  is finished. Thus, the turntable  5  can be moved to the predetermined revolution position and rotation position in a shorter time compared to the case where the revolution and the rotation of the turntable  5  are mechanically interlocked by a gear or the like. Consequently, the tact time for replacing the polishing plate  6  can be reduced. 
     For more details, since the rotating speed ratio between the rotation of the turntable  5  shown in  FIG. 6A  and the revolution of the turntable  5  shown in  FIG. 6B  is approximately “rotation:revolution=1:100,” when the revolution and the rotation of the turntable  5  are mechanically interlocked by a gear or the like, the turntable  5  should be revolved approximately 100 times to move the turntable  5  to the predetermined rotation position. Thus, it takes a lot of time. On the other hand, in the present embodiment, since the revolution mechanism  12  configured to revolve the turntable  5  and the rotation mechanism  13  configured to rotate the turntable  5  separated from a revolution movement of the turntable  5  revolved by the revolution mechanism  12  are provided, the turntable  5  can be moved to the predetermined revolution position by rotating the turntable  5  approximately one time (one revolution) by the revolution mechanism  12  and moved to the predetermined rotation position by rotating the turntable  5  approximately one time (one rotation) by the rotation mechanism  13 . As a result, the time of moving the turntable  5  to the predetermined revolution position and rotation position can be reduced. Consequently, the tact time for replacing the polishing plate  6  can be reduced. 
     As shown in  FIG. 3  and  FIG. 4 , since the rotation unit  7  includes the rotation mechanism  13  configured to rotate the turntable  5  separated from a revolution movement of the turntable  5  revolved by the revolution mechanism  12 , after the polishing plate  6  on the turntable  5  moved to the predetermined revolution position is replaced with the polishing plate  6  used in the subsequent process by using the hands of the uniaxial robot or the like, water, polishing agent and the like used for the polishing can be supplied on an arbitrary position (except for the center) of the polishing plate  6  on the turntable  5  by using an automatic supply device controlled by the control unit  8   b  while the turntable  5  is rotated by the rotation mechanism  13  keeping the revolution position. Because of this, the water, the polishing agent and the like can be applied on the upper surface of the polishing plate  6  and the polishing can be performed well in the subsequent process. 
     As shown in  FIG. 4 , since a plurality of the recesses (three parts at 120° interval in the present embodiment) is formed on a lower part of the rotation gear  13   d  as the rotation position reference portions  13   h  with an interval in a circumferential direction of the rotation gear  13   d , the rotation angle to rotate the turntable  5  to the predetermined rotation position after the polishing is finished can be smaller compared to the case where one rotation position reference portion is formed. Thus, the turntable  5  can be moved to the predetermined rotation position in a shorter time. 
     First Modified Example 
       FIGS. 7A to 7C  are explanatory drawings showing the first modified example of a polishing plate  6  and a turntable  5   x.    FIG. 7A  is a side cross-sectional view of the polishing plate  6   x.    FIG. 7B  is a side cross-sectional view where the polishing plate  6   x  is installed on the turntable  5   x.    FIG. 7C  is a side cross-sectional view where the polishing plate  6   x  and the turntable  5   x  are exploded. The end face polishing device  1  of the optical fiber ferrules  2  including the polishing plate  6   x  and the turntable  5   x  has the same configurations as the above described embodiment except for the configurations of the polishing plate  6   x  and the turntable  5   x.    
     Namely, as shown in  FIG. 7C , the revolution eccentric arm  12   c  is horizontally attached to the revolution output shaft  12   b  extended upward from the revolution motor  12   a,  and the revolution drive shaft  12   d  is attached to be extended upward from the revolution eccentric arm  12   c.  An upper part of the revolution drive shaft  12   d  is inserted into a circular hole  51   x  formed on a center of the lower surface of the turntable  5   x  so that the revolution drive shaft  12   d  can be freely slid in an axial direction and freely rotated in a circumferential direction. In addition, the rotation drive shafts  13   g  shown in  FIG. 3  are inserted into a not illustrated circular hole formed on the lower surface of the turntable  5   x  so that the drive shafts  13   g  can be freely slid in an axial direction and freely rotated in a circumferential direction. 
     As shown in  FIG. 7C , the polishing plate  6   x  is replaceably installed on the turntable  5   x . The polishing plate  6   x  includes: a pad holding tray  61   x;  a pad  62   x;  and a polishing film  63   x . The pad holding tray  61   x  is replaceably installed on the turntable  5   x.  Recesses  64   x,    65   x  are formed on a lower surface of the pad holding tray  61   x  so that the recesses  64   x,    65   x  are detachably fitted in the plurality of protrusions  52   x,    53   x  formed on the upper surface of the turntable  5   x  from the above. When the recesses  64   x,    65   x  are fitted in the protrusions  52   x,    53   x , the pad holding tray  61   x  is integrally rotated and revolved with the turntable  5   x.    
     As shown in  FIG. 7C , a recess  66   x  is formed on the upper surface of the pad holding tray  61   x  so that the pad  62   x  is detachably installed on the recess  66   x  from the above. A groove portion  67   x  is formed in a ring shape on a periphery of the recess  66   x  along a circumferential direction for catching water and polishing agent A spilled during the polishing. An elastic material such as a rubber and a resin is used as the material of the pad  62   x  installed on the recess  66   x.  A polishing film  63   x  is installed on the upper surface of the pad  62   x  for substantially polishes the end face of the optical fiber ferrules  2 . Water and polishing material A are supplied to the polishing film  63   x  before the operation of the polishing. In the present modified example, the pad holding tray  61   x,  the pad  62   x  and the polishing film  63   x  constitute the polishing plate  6   x.    
     As shown in  FIG. 7B , after the end face of the optical fiber ferrules  2  shown in  FIG. 3  is polished in a state that the polishing plate  6   x  is installed on the turntable  5   x,  the pad holding tray  61   x,  the pad  62   x  and the polishing film  63   x  are integrally detached as the polishing plate  6   x  as shown in  FIG. 7A  similar to the above described embodiment, and replaced with the polishing plate  6   x  (pad holding tray  61   x,  pad  62   x  and polishing film  63 ) used in the subsequent process. Since the pad  62   x  is detached from the turntable  5   x  together with the pad holding tray  61   x  without detaching the pad  62   x  from the pad holding tray  61   x,  even when the pad  62   x  is adhered to the pad holding tray  61   x  due to the water and the polishing material A in the recess  66   x,  the pad  62   x  on which the polishing film  63   x  is installed can be easily detached from the turntable  5   x  together with the pad holding tray  61   x  and replaced with another one. 
     Second Modified Example 
       FIG. 8A  shows the polishing plate  6  concerning the second modified example. In the end face polishing device  1  of the optical fiber ferrules  2  using the polishing plate  6  of the second modified example, the rotation position reference portions  13   h  and the rotation sensor  8   c  shown in  FIG. 4  are eliminated, and the turntable  5  is moved only to the predetermined revolution position by the revolution mechanism  12  operated and controlled by the controller  8  after the polishing is finished. In this case, as shown in  FIG. 8A , continuous flanges  6   c  are formed on aside surface of the polishing plate  6  along a circumferential direction. Thus, even when the turntable  5  the rotation position (rotation angle) is not constant after the polishing is finished, if the revolution position of the turntable  5  is uniquely determined, a hand H of the uniaxial robot or the like can be accurately inserted in a lower surface of the flanges  6   c  of the polishing plate  6  on the turntable  5  from the above of the turntable  5  by moving the hand H to a predetermined position. Thus, the polishing plate  6  can be picked up. 
     Third Modified Example 
       FIG. 8B  shows the polishing plate  6  concerning the third modified example. In the end face polishing device  1  of the optical fiber ferrules  2  using the polishing plate  6  of the third modified example, same as the second modified example, the rotation position reference portions  13   h  and the rotation sensor  8   c  shown in  FIG. 4  are eliminated, and the turntable  5  is moved only to the predetermined revolution position by the revolution mechanism  12  operated and controlled by the controller  8  after the polishing is finished. In this case, as shown in  FIG. 8B , a polishing plate mounting stand  5   f  having a smaller diameter than that of the polishing plate  6  is protruded from the recess  5   a  of the turntable  5  and a polishing plate holding jig  6   d  having a stepped ring shape is attached on a peripheral edge of the polishing plate  6  protruded from the polishing plate mounting stand  5   f.  Thus, even when the turntable  5  the rotation position (rotation angle) is not constant after the polishing is finished, if the revolution position of the turntable  5  is uniquely determined, a hand H of the uniaxial robot or the like can be accurately engaged with the polishing plate holding jig  6   d  of the polishing plate  6  on the turntable  5  from the above of the turntable  5  by moving the hand H to a predetermined position. Thus, the polishing plate  6  can be picked up. 
     For more details, the polishing plate holding jig  6   d  is formed in a stepped ring shape in cross-section as shown in  FIG. 8B . The polishing plate holding jig  6   d  includes: a lower ring plate  6   d   1  which is in contact with a lower surface of an outer periphery of the polishing plate  6 ; a center ring cylinder  6   d   2  which is in contact with a side surface of an outer periphery of the polishing plate  6 ; and an upper ring plate  6   d   3  having a lower surface into which the tip of the hand H is inserted. The polishing plate holding jig  6   d  is detachably attached to the polishing plate  6 . The polishing plate holding jig  6   d  is made of resin, metal or the like, for example. When the polishing plate holding jig  6   d  is attached to the polishing plate  6 , the strength is increased as an assembly. Accordingly, even when the pad  6   a  of the polishing plate  6  is made of glass, for example, handling can be safer and easier. 
     In addition, since the polishing plate holding jig  6   d  is detachably attached, a conventional polishing plate  6  shown in  FIG. 5A  or the like can be used. 
     The preferred embodiments of the present invention are explained above with reference to the attached drawings. Of course, the present invention is not limited to the above described embodiments. It goes without saying that various modified examples and corrected examples within the range described in the claims also belong to the technical scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be used for the end face polishing device for the optical fiber ferrule for polishing the end face of the optical fiber ferrule. 
     DESCRIPTION OF THE REFERENCE NUMERALS 
       1 : end face polishing device for optical fiber ferrule, 
       2 : optical fiber ferrule, 
       2   a : optical fiber ferrule fixing jig, 
       3 : polishing holder, 
       4 : holding unit, 
       5 : turntable, 
       6 : polishing plate, 
       7 : rotation unit, 
       8 : controller, 
       8   a : non-contact proximity sensor as revolution sensor, 
       8   c : non-contact proximity sensor as rotation sensor, 
       9 : moving unit, 
       12 : revolution mechanism, 
       12   e : protrusion as revolution position reference portion, 
       13 : rotation mechanism, 
       13   h : recess as rotation position reference portion,