Patent Publication Number: US-6908367-B2

Title: Apparatus for processing a lens

Description:
FIELD OF THE INVENTION 
   The present invention relates to an apparatus for processing a lens, used for processing the peripheral portion of a lens, such as a spectacle lens, to provide a prescribed shape so that the lens can be fitted into a lens frame of a spectacle frame. 
   BACKGROUND OF THE INVENTION 
   In the art of making lenses, when a lens, such as a spectacle lens, is processed so that the lens may be fitted into a lens frame of a spectacle frame, the peripheral face of an uncut lens is ground by a grinder, or cut by a cutter. In this manner, peripheral portion of the uncut lens is formed into a prescribed shape in accordance with data corresponding to the shape of the lens frame of the spectacle frame. 
   Prior art examples of the known processing apparatus for this purpose include, as disclosed in Japanese Patent Application Laid-Open No. 2001-18154, apparatuses in which, after the peripheral portion of a lens is processed by the flat grinding or the beveled grinding using a rotating tool (a grinder), which is freely rotated to grind the peripheral portion of a lens. The prior art apparatuses also conduct chamfering and grooving as steps in the finishing of the peripheral portion of the lens by using a grinder for chamfering and a grinder for grooving, which are coaxially disposed. 
   In Japanese Patent Application Laid-Open No. 2001-87922, an apparatus for chamfering and grooving the peripheral portion of a lens using a single ball end mill is disclosed. 
   However, as shown in  FIG. 15 , since conventional apparatuses, such as those described above, are equipped with a grinder for chamfering the concave face of the lens and a grinder for chamfering the convex face of the lens, wherein these grinders are formed integrally with a grinder for grooving that is disposed between these two grinders for chamfering, it occasionally occurs that, as shown in the portion A of  FIG. 15 , the grinder for grooving protrudes radially beyond the outside of the periphery of both grinders for chamfering, and one of the grinders for chamfering protrudes laterally at a peripheral portion so as to contact the lens-holding shaft and interfere with lens processing. When this problematical arrangement takes place, in particular, such as in the case of a lens having a small diameter, chamfering cannot be properly conducted. In the example of the conventional apparatus of  FIG. 15 , when changing the chamfering angle, the desired chamfering angle is achieved by inclination of the shaft upon which the grinder for chamfering is mounted. This method for changing the chamfering angle is problematical in that, in order to conduct chamfering while the shaft is inclined at various desired angles, the apparatus required includes complicated driving mechanisms and supporting mechanisms for the tool, and the size of the apparatus increases. 
   In the example described in  FIG. 15 , the grooving is conducted by using the tip of a ball end mill and the chamfering is conducted by using a side face of the same single ball end mill. Since the outer diameter of the ball end mill is determined by the width of the groove formed at the outer peripheral face of the lens, it becomes necessary to perform a plurality of processing steps, each step is conducted at a different position on the face of the lens, or the processing must be conducted while the tool is moved when the chamfering area is great (or the curvature of chamfering is great). Therefore, problems arise in that the processing time increases and the control operation for the apparatus becomes complex and difficult. 
   The present invention has been made to overcome the above problems with the prior art lens processing apparatuses. One object of the present invention is to provide an apparatus for processing a lens that can achieve chamfering and grooving of a lens, in particular a lens having a small diameter, by using a simple mechanism that can achieve a desired chamfering in a short time. 
   SUMMARY OF THE INVENTION 
   The present invention provides an apparatus for processing a lens which comprises a finishing unit for chamfering and grooving a peripheral portion of a spectacle lens, the apparatus comprising: a holding shaft supporting the lens, a lens-holding unit that rotates the holding shaft and displaces the lens towards the finishing unit based on data describing a shape of a lens frame and a rotation angle of the holding shaft, and a means for positioning in an axial direction that displaces the lens in an axial direction of the holding shaft; wherein the finishing unit comprises a rotating tool for chamfering and a rotating tool for grooving that are disposed at positions separated by a prescribed distance along the holding shaft, and a single means for driving which is connected with the rotating tool for chamfering and the rotating tool for grooving, one of the rotating tool for chamfering and the rotating tool for grooving is selected in accordance with a displacement in the axial direction of the means for positioning in an axial direction, a prescribed position for processing or a prescribed processing amount is set in accordance with the displacement in the axial direction, and the finishing of the peripheral portion of the lens is conducted by using the rotating tool for grooving and the rotating tool for chamfering successively. 
   The present invention also provides an apparatus for processing a lens which comprises a rotating tool for chamfering used for chamfering a peripheral portion of a spectacle lens, the apparatus comprising: a holding shaft supporting the lens, a lens-holding unit which rotates the holding shaft and displaces the lens towards the finishing unit based on data describing a shape of a lens frame and a rotation angle of the holding shaft, and a means for positioning in an axial direction that displaces the lens in an axial direction of the holding shaft; wherein the rotating tool for chamfering includes a rotating tool having a hemispherical shape, a chamfering angle or a chamfering amount is set in accordance with a displacement in the axial direction of the means for positioning in an axial direction and a displacement of the lens-holding unit, and the chamfering angle or the chamfering amount can be changed in accordance with the relative position between the rotating tool having the hemispherical shape and the peripheral portion of the lens. 
   In the present invention, one of the rotating tool for chamfering and the rotating tool for grooving is selected by displacement of the lens-holding unit in the axial direction of the holding shaft and the lens-holding unit and the means for positioning in the axial direction are displaced towards the selected tool based on the data describing the shape of the lens frame. Therefore, the prescribed chamfering and the prescribed grooving of the peripheral portion of the lens can be conducted independently. Since the rotating tool for chamfering and the rotating tool for grooving are disposed independently at positions separated by a prescribed distance, interference of the rotating tool for grooving with the lens-holding shaft during the chamfering is prevented and the chamfering and the grooving can be reliably achieved even when the lens has a small diameter. 
   In the present invention, the rotating tool having the hemispherical shape and the lens are relatively displaced in the radial direction and in the axial direction by using the lens-holding unit and the means for positioning in the axial direction so that lens processing can be conducted at both a desired chamfering angle and a desired chamfering amount using a single tool. Therefore, by using the apparatus for lens processing in accordance with the present invention, the time required for lens processing can be decreased while the chamfering is conducted for various shapes. 
   In accordance with yet another embodiment, there is provided an apparatus for processing a lens. The apparatus comprises a finishing unit for chamfering and grooving a peripheral portion of a spectacle lens. A holding shaft is arranged to support the lens. A lens-holding unit is connected to rotate the holding shaft and displace the lens towards the finishing unit based on data describing a shape of a lens frame and a rotation angle of the holding shaft. A positioning device is connected to displace the lens in an axial direction of the holding shaft. The finishing unit further comprises a rotating tool for chamfering and a rotating tool for grooving, both tools being disposed at positions separated by a prescribed distance along the holding shaft, and a drive connected to drive the rotating tool for chamfering and the rotating tool for grooving, wherein one of the rotating tool for chamfering and the rotating tool for grooving is selected for finish processing in accordance with a displacement in the axial direction of the positioning device in an axial direction, and a prescribed position for processing, or a prescribed processing amount, set in accordance with displacement in the axial direction. 
   In a still further embodiment, the lens-holding unit is displaced freely in a vertical direction, the finishing unit is disposed at a position vertically above the holding shaft, and the positioning device is connected to position the lens relative to the rotating tool for chamfering and the rotating tool for grooving based on a first position in the axial direction determined in accordance with a rotating angle measured in advance based on data describing a shape of a lens frame. 
   In yet another embodiment, a first distance from the holding shaft to the rotating tool for grooving is set to be longer than a second distance from the holding shaft to the rotating tool for chamfering. 
   In another embodiment, the rotating tool for chamfering and the rotating tool for grooving are each disposed on a respective shaft standing in a direction perpendicular to the holding shaft. 
   In a still further embodiment, the rotating tool for chamfering includes a rotating tool having a hemispherical shape. 
   In another embodiment, the finishing unit is displacable between a first position for processing where the rotating tool for chamfering and the rotating tool for grooving face towards the holding shaft and a prescribed waiting position that is separated from the first position where the rotating tool for chamfering and the rotating tool for grooving face towards the holding shaft. 
   In yet another embodiment there is provided an apparatus for processing a lens comprising a rotating tool for chamfering a peripheral portion of a spectacle lens. In this embodiment, a holding shaft disposed to support the lens. A lens-holding unit is disposed to rotate the holding shaft and displace the lens towards the finishing unit based on data describing a shape of a lens frame and a rotation angle of the holding shaft. A positioning device is connected to displace the lens in an axial direction of the holding shaft. The rotating tool for chamfering includes a rotating tool having a hemispherical shape, wherein a chamfering angle, or a chamfering amount, is set in accordance with a displacement in the axial direction of positioning device in an axial direction and a displacement of the lens-holding unit. 
   In another embodiment, the rotating tool for chamfering is disposed in a direction perpendicular to the holding shaft and is fixed at a prescribed position during lens processing. 
   In yet another embodiment, the rotating tool for chamfering is displaced between a first position for processing where the rotating tool for chamfering faces towards the holding shaft and a prescribed waiting position that is separated from the first position where the rotating tool for chamfering faces towards the holding shaft. 
   In a still further embodiment, the drive includes a single motor, and the rotating tool for chamfering and the rotating tool for grooving are simultaneously driven by the single motor, and a transmission is provided connected to the single motor so that the single motor drives both the rotating tool for chamfering and the rotating tool for grooving. 
   Further objects, features and advantages of the present invention will become apparent from the Detailed Description of Illustrative Embodiments, which follows, when considered together with the attached Figures. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a perspective view of the lens processing apparatus according to an embodiment of the present invention. 
       FIG. 2  is a perspective view exhibiting the main portions of the inner construction of the apparatus in FIG.  1 . 
       FIG. 3  is a perspective view exhibiting a base unit, an elevating and lowering unit and a lens unit in the inner construction shown in FIG.  2 . 
       FIG. 4  is a sectional view of the elevating and lowering unit and the lens unit in the vertical direction when the processing is started. 
       FIG. 5  is a sectional view of the elevating and lowering unit and the lens unit in the vertical direction at the moment in time when the processing is completed. 
       FIG. 6  is a sectional view of the elevating and lowering unit and the lens unit in the horizontal direction in the condition that the lens is held by the lens-holding shafts (this is the “lens holding condition”). 
       FIG. 7  is a sectional view of the elevating and lowering unit and the lens unit in the horizontal direction in the condition that the lens is released from the lens-holding shaft (this is the “lens releasing condition”). 
       FIG. 8  is a perspective view of the finishing unit at the waiting position (also called the “retired position”). 
       FIG. 9  is a perspective view of the finishing unit at the processing position (also called the “advanced position”). 
       FIG. 10  shows diagrams exhibiting the grooving, in which (a) shows a perspective view of the finishing unit and (b) shows a sectional view of a lens during the grooving processing. 
       FIG. 11  is a sectional view exhibiting the chamfering of the convex face of a lens. 
       FIG. 12  is a sectional view exhibiting the chamfering of the concave face of a lens. 
       FIG. 13  is a diagram describing the relative positions of the lens and the rotating tool having a hemispherical shape, in which (a) shows the coordinates of the tool and the position of the lens and (b) shows the relation between the apices of the lens and the chamfered portion of face portion  1   e.    
       FIG. 14  is a block diagram exhibiting the control portion. 
       FIG. 15  is a side view exhibiting the relation between a lens-holding shaft and a grinder for finishing in a conventional apparatus (prior art). 
   

   DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS OF THE INVENTION 
   An embodiment of the present invention will be described in the following with reference to the Figures, wherein like parts are represented by like character references. 
     FIG. 1  is a perspective view of an apparatus  10  for processing a lens.  FIGS. 2 and 3  show perspective views exhibiting the inner construction of the lens processing apparatus  10 . 
   In  FIG. 1 , at the right side of the front of the lens processing apparatus  10 , contained in a case  11  having the shape of a rectangular parallelepiped  11 , is disposed an operation portion  13  for selecting or inputting the conditions for lens processing for the lens and a display portion  12  for displaying information on the processing, such as the data describing the shape of the lens frame and the processing data used for the processing. The operation portion  13  includes touch panels, touch switches, keys, other manual controls, or the like. The display portion  12  includes LCD, CRT, other display assemblies, and the like. 
   At the front center of the lens processing apparatus  10 , a door  14  is disposed, which can be opened or closed as desired, and is used for inserting or taking out a lens. 
   After the interior construction of the lens processing apparatus  10  is generally described, various members and portions will be described in detail. 
   General Outline of the Interior Construction of the Lens Processing Apparatus 
   In  FIGS. 2 and 3 , a base unit  2 , which is equipped with a main rotating tool  50  (also referred to as “a main means for processing”) that can be displaced in the direction parallel to a main shaft  51  (i.e., the direction of the X-axis in FIGS.  2  and  3 ), is disposed inside of the case  11 . The base unit  2  supports a lens unit  4  (also called a “a lens-holding unit”), which can be displaced in the vertical direction (i.e., in the direction of the Z-axis in the Figures). 
   The direction from the right to the left in  FIG. 2  (i.e., the transverse direction of the apparatus for processing a lens  10 ) is assigned to the X-axis, the vertical direction (i.e., the direction of the height of the apparatus) is assigned to the Z-axis, and the direction from the left to the right in  FIG. 4  (i.e., the direction towards the inside of the apparatus) is assigned to the Y-axis. It is assumed that these axes orthogonally intersect each other to provide a conventional Cartesian coordinate system. 
   The lens unit  4  includes a lens-holding shaft  41 , which is divided into two portions  41 R,  41 L and selectively holds the center of the lens  1  between the two portions. The lens holding shaft  41  is disposed in a manner so that the lens-holding shaft can be rotated freely. The lens-holding shaft  41  is placed on the vertical line of the main rotating tool  50 , which is a grinder or a cutter that is supported by a shaft on a base plate  15 . The lens-holding shaft  41  and the main shaft  51  of the main rotating tool  50  are arranged parallel to each other along the X-axis. The lens  1  is held by the lens-holding shaft  41  in a manner so that the face of the lens  1  is placed along a plane perpendicular to the axial line of the lens holding shaft  41 . 
   A measuring unit  6 , comprising styluses  60  and  61  for measuring positions on the concave face  1   b  and the convex face  1   a , respectively, of the lens  1 , is fixed on the vertical line of the lens-holding shaft  41 . 
   The styluses  60  and  61  can be displaced in a direction parallel to the lens-holding shaft  41 . To measure the position of the lens  1  after processing is complete, the styluses  60  and  61  are brought into contact with both faces of the lens  1  when the lens unit  4  is in an elevated condition. The lens unit  4  is elevated or lowered in accordance with the data describing the shape of the lens frame while the lens-holding shaft  41  is rotated. 
   For processing the lens  1 , starting from the condition shown in  FIG. 2 , the lens unit  4  is lowered after the main rotating tool  50  is rotated and the peripheral portion (i.e., the outer peripheral portion) of the lens  1  is ground into the prescribed shape by elevating or lowering the lens unit  4  in accordance with data describing the shape of the lens frame while the lens-holding shaft  41  is rotated. 
   By elevating or lowering the lens unit  4 , based on the data describing the shape of the lens frame that is used to determine corresponding rotation angles for the lens-holding shaft  41 , the grinding to the processing depth, in accordance with the rotation angle of the lens  1 , is conducted in a continuous manner. During processing, the force pressing the lens  1  against the main rotating tool  50  is called the “processing pressure” and is provided by the weight of the lens unit  4  itself. Adjustment of the processing pressure is required depending upon the material of the lens, and such adjustment is conducted by supporting a portion of the weight of the lens unit  4  by a unit  8  for controlling the processing pressure that is disposed at a position above the lens unit  4 . 
   The position of contact between the lens  1  and the main rotating tool  50  is changed by displacing the base unit  2  in the direction of the X-axis as evident from FIG.  2 . By displacing base unit  2  in the direction of the X-axis, a selection between the flat grinding and the beveled grinding can be made depending upon whether one of grinders  50   a ,  50   b  or one of grinders  50   c ,  50   d  is in contact with lens  1 . Likewise, switching between the rough grinding and the finishing grinding can also be made depending upon whether one of grinders  50   a ,  50   c  or one of grinders  50   b ,  50   d  is in contact with the lens  1 . 
   A finishing unit  7  (also referred to as “a means for finishing”) comprises a rotating tool  70  for chamfering and a rotating tool  71  for grooving. Finishing unit  7  can be displaced in the direction of the Y-axis (i.e., in the inner direction of the apparatus) and is disposed at a position above the lens unit  4 . When the finishing unit  7  is at the advanced position as shown in  FIG. 9 , the rotating tool  70  for chamfering and the rotating tool  71  for grooving are placed at a position directly above the lens-holding shaft  41 . The selection between the rotating tools  70  and  71  is made depending upon whether chamfering or grooving is required, and the position of the processing is set by elevating the lens unit  4  in the direction of the Z-axis and driving the base unit  2  in the direction of the X-axis. Finishing is then conducted with the apparatus  10  in this condition. 
   Various portions of the inner construction of the lens processing apparatus  10  will be described in more detail as follows. 
   The Main Shaft Unit 
   In  FIGS. 2 ,  3  and  4 , the main shaft  51 , upon which the rotating tool  50  (a grinder or a cutter having diamond or the like) is disposed, and a motor  55  for driving the main shaft  51  are fixed to the base plate  15  inside of the case  11 . The main shaft unit includes main shaft  51 , rotating tool  50 , and motor  55  as the main components. 
   The main shaft  51 , as shown in  FIG. 2 , is supported by a shaft mounted on the base plate  15  along the X-axis in a manner that allows the main shaft  51  to be rotated freely around the support shaft. Main shaft  51  is disposed to be parallel with the lens-holding shaft  41 . 
   At the end portion of the main shaft  51 , a main rotating tool  50  for mechanically processing the lens  1  is attached. The main rotating tool  50  is placed at the central portion of the apparatus  10  in the direction of the X-axis as shown in FIG.  2  and at the front side of the apparatus  10  (i.e., at the lower left side in FIG.  4 ). The base end portion of the main shaft  51  (located at the right side in  FIG. 2 ) is driven by a motor  55  via a belt  57  and pulleys. 
   As shown in  FIG. 2 , the main rotating tool  50 , which mechanically processes the lens  1 , includes a rough grinder  50   a  for flat grinding, a finishing grinder  50   b  for flat grinding, a rough grinder  50   c  for beveled grinding and a finishing grinder  50   d  for beveled grinding, each disposed successively from the side of the tip of the main shaft  51  (i.e., from the left side in FIG.  2 ). In the alternative, grinding may also be conducted by using cutters as the rotating tool in place of the grinders without departing from the scope of the present invention. 
   The Base Unit 
   A base unit  2  for driving the lens unit  4  in the direction of the X-axis is disposed at a position posterior to the main shaft  51  in  FIG. 2  (i.e., in the direction of the Y-axis, at the right side in the Figure). 
   As shown in  FIG. 3 , the base unit  2  includes a base  20 , which can be displaced in the direction of the X-axis, and a servomotor  25  (hereinafter, referred to as the “X-axis motor”), which controls the positioning by driving the base  20  by driving the base  20  in the direction of the X-axis. 
   The base  20  is disposed on guide members  21  and  22 , which are fixed on the base plate  15  and oriented along the direction of the X-axis in a manner such that the base  20  can be freely displaced along the X-axis. Therefore, the base  20  can be freely displaced in the direction of the X-axis. 
   As shown in  FIG. 3 , an inner screw  23  is disposed at a position below the base  20  and between the guide members  21  and  22  in a manner such that the inner screw  23  can be rotated freely about its own axis. An outer screw  24  fixed at the lower face of the base  20  is engaged with the inner screw  23  and the base  20  is driven in the direction of the X-axis by rotation of the screw  23 . Screw  23  is driven to rotate by the X-axis motor  25 . 
   One end of the inner screw  23  and the X-axis motor  25  are connected to each other via a gear and a cogged belt  26 , and the base  20  is positioned in the direction of the X-axis in accordance with the rotation angle of the X-axis motor  25 . 
   The Elevating and Lowering Unit 
   As shown in  FIG. 3 , four poles  401 ,  402 ,  403 , and  404  stand on the base  20 . Among the four poles, the two poles  401  and  402  penetrate a frame  40  of the lens unit  4  so as to guide the lens unit  4  in the vertical direction (i.e., the direction of the Z-axis) in a manner such that the lens unit  4  can be displaced freely in the vertical direction. 
   As shown in  FIGS. 3 and 4 , the lens unit  4  is driven in the vertical direction and positioned in the vertical direction by the elevating and lowering unit  3 , which is displaced in the direction of the Z-axis. On the other hand, the lens unit  4  is positioned in the direction of the X-axis by the base unit  2  as discussed above. 
   The elevating and lowering unit  3 , as shown in  FIGS. 3 ,  4  and  6 , includes the following: a screw  31 , which is supported by a shaft on the base  20  between the poles  401  and  402  and penetrates the frame  40  of the lens unit  4  in the vertical direction; a positioning member  34 , which is engaged with the screw  31  at the inner peripheral portion of the positioning member and which can support the lens unit  4  by contacting the frame  40  of the lens unit  4  at the upper end of the positioning member; and a servomotor  33  (hereinafter, referred to as a “Z-axis motor”), which is connected to the lower end of the screw  31  via a cogged belt  32  and a gear. The elevating and lowering unit  3  is disposed on the base  20 . 
   In the elevating and lowering unit  3 , the screw  31  is rotated by driving the Z-axis motor  33  so that the positioning member  34 , having an outer screw  35  engaged with the screw  31 , is driven in the direction of the Z-axis. The outer screw  35  is displaced in the direction of the Z-axis because the rotating movement in the circumferential direction is restricted by a mechanism at the lens unit  4 , as is discussed later. 
   As shown in  FIG. 4 , the positioning member  34  contacts the inner periphery of a hole portion  40 A formed in the frame  40  of the lens unit  4 . The contact between the positioning member  34  and the inner periphery of the hole portion  40 A occurs in the vertical direction in a manner so that the positioning member  34  can slide and make a relative displacement in the vertical direction within the hole portion  40 A. 
   At the upper end of the hole portion  40 A, a ceiling portion  400  connected to the frame  40  is disposed. As shown in  FIGS. 3 and 6 , along side of the outer screw  35  of the positioning member  34 , a stopper  36  standing in the direction of the Z-axis is disposed at a position so that the stopper  36  can contact the lower face of the ceiling portion  400 . 
   In  FIG. 3 , the stopper  36  is shown protruding from the upper portion of the positioning member  34  and contacts the lower face of the ceiling portion  400  so that the weight of the lens unit  4  applied by the ceiling portion  400  is supported by the positioning member  34 , which includes both the stopper  36  and the outer screw  35 . The outer screw  35  and the stopper  36  are connected to each other at each base portion through a base  340  of the positioning member  34 . 
   As evident from  FIG. 6 , the hole portion  40 A of the frame  40  has a sectional shape such that the positioning member  34  and the stopper  36  fix each other around the Z-axis (i.e., in the direction perpendicular to the plane of  FIG. 6 ) so that idle rotation of the outer screw  35  by the rotation of the screw  31  is prevented. In other words, the stopper  36  is fixed at the side of the outer screw  35  and connected to the outer screw  35  by base  340 . Stopper  36  is arrested by the hole portion  40 A so the rotation of the positioning member  34  is also prevented. Thus, the outer screw  35  is elevated or lowered by the rotation of the screw  31  and the positioning member  34  is displaced in the direction of the Z-axis due to this movement of the outer screw member  35 . 
   When the stopper  36  does not contact the ceiling portion  400 , the lens  1  supported by the lens unit  4  is brought into contact with the main rotating tool  50 , as shown in  FIG. 5 , and the weight of the lens unit  4  itself is applied as the processing pressure. The upper end face  34 A of the positioning member  34  and the lower face of the ceiling portion  400  do not contact each other under these circumstances. Consequently, a prescribed gap is formed between the upper end face  34   a  of the positioning member  34  and the lower face of the ceiling portion  400 . 
   At a position below the ceiling portion  400  and facing the gap, a hole portion  421  is provided in frame  40 . A sensor arm  300  for detecting completion of the processing on the lens unit  4 , in the vertical direction, is also provided. The sensor arm  300  may be referred to as the “means for amplifying a relative displacement.” An end of the sensor arm  300  is inserted into the hole portion  421  and is disposed along the Y-axis, as shown in  FIG. 4 , in a manner such that the hole portion  421  penetrates the frame  40  across the hole portion  40 A. In other words, hole portion  421  and hole portion  40 A are contiguous. 
   The sensor arm  300 , as shown in  FIGS. 4 and 5 , is an integrally formed arm having the shape of an inverse L, which is composed of an arm  301  extending to the left side in the Figures (in the direction of the Y-axis) and that inserts into the hole portion  421 , and an arm  302  extending in the lower direction in the Figure (in the direction of the Z-axis, to the side of the base  20 ). The arm  301  and the arm  302  are disposed approximately perpendicularly to each other. The length of the arm  302  in the vertical direction is set longer than that of the arm  301  in the horizontal direction. 
   A bending portion  303 , located at the middle of the sensor arm  300  having the shape of an inverse L, is supported by a shaft  420  disposed by the ceiling portion  400  of the lens unit  4  in a manner so that the bending portion  303  can freely swing around the shaft  420 . Therefore, the sensor arm  300  can swing around the X-axis. 
   Between the arm  302  extending in the direction of the Z-axis and the ceiling portion  400 , a spring  310  is disposed, which pushes or biases the arm  301  that extends in the direction of the Y-axis to rotate towards the lower direction in  FIGS. 4 and 5  (i.e., to rotate in the counter-clockwise direction about shaft  420  shown in the Figures). 
   Since the arm  301  inserted into the hole portion  421  and crosses the hole portion  40 A in the direction of the Y-axis, arm  301  is constructed to include a penetrating portion through which the screw  31  inserts. Furthermore, arm  301  is connected so that the lower face of the arm  301  faces towards the inner periphery of the hole portion  40 A so that the lower face of the arm  301  can be brought into contact with, or separated, from the upper end face  34 A of the positioning member  34 . 
   Since the sensor arm  300  is pushed in the counter-clockwise direction, as evident in  FIG. 4 , by the spring  310 , the tip  301 A of the arm  301  is brought into contact with the lower side of the hole portion  421  and stops there when the upper end face  34 A of the positioning member  34  and the arm  301  are separated from each other (this is the condition whenever the stopper  36  is separated from the ceiling  400 ). 
   On the other hand, as shown in  FIG. 5 , when the stopper  36  of the positioning member  34  contacts the ceiling portion  400  of the lens unit  4 , the positioning member  34  supports the lens unit  4 , and the upper end face  34 A of the positioning member  34  pushes the arm  301  in the upper direction (i.e., clockwise). In other words, when stopper  36  contacts ceiling portion  400 , the positioning member  34  contacts the arm  301  and pushes the arm in the clockwise direction about shaft  420  in a pivotal manner. When this occurs, the sensor arm  300  rotates and the arm  302  extending in the direction of the Z-axis is placed at the prescribed position (for example, a position in the vertical direction as shown in FIG.  5 ). 
   A bracket  422  protruding along the lower portion (i.e., arm  302 ) of the sensor arm  300  is disposed at the frame  40 . At a prescribed position of the bracket  422 , which can face to the lower end of the arm  302  that swings around the X-axis, a sensor  320  is disposed at a position located approximately below the shaft  420 . Sensor  320  is for detecting completion of the processing (also referred to as a “means for detection”) by detecting the approach of the free end portion of the arm  302  swinging around the X-axis. The “free end portion” of sensor  320  is defined to be the end portion of the sensor arm  300  that is detected by the sensor  320  for detecting completion of the processing. In the present embodiment, the “free end portion” corresponds to the end portion of the arm  302 . 
   The sensor  320  for detecting completion of the processing is, for example, constructed to include a photosensor, such as a photointerruptor. As shown in  FIG. 5 , when the swinging arm  302  comes to the prescribed position (i.e., the position in the vertical direction where the lens unit  4  and the positioning member  34  are brought into contact with each other) and the light of the photointerruptor of the sensor  320  for detecting completion of the processing is interrupted, the sensor  320  is switched to ON so as to detect that processing has been completed. The prescribed position wherein the sensor  320  detects the presence of the free end portion of the sensor arm  300  is referred to as the “position of detecting the arm” or the “position detecting the completion of processing.” 
   The elevating and lowering unit  3  supports the lens unit  4  in the elevating direction. After the lens unit  4  starts the processing of the lens  1 , the processing depth, (also called the processing amount), is decided in accordance with the position of the elevating and lowering unit  3  in the direction of the Z-axis. In other words, movement of the lens unit  4  by the elevating and lowering unit  3  is the manner in which apparatus  10  directs the processing depth, whereas movement of the lens unit  4  from an initial lens processing position shown in  FIG. 4  (i.e., the upper face  34 A of positioning member  34  is separated from the inner periphery of the hole portion  40 A) to a completed lens processing position shown in  FIG. 5  (i.e., the upper face  34 A of positioning member  34  is in contact with the inner periphery of the hole portion  40 A) occurs during actual lens grinding or cutting. When the prescribed processing depth is achieved, the sensor for detecting completion of the processing  320  is switched to ON. The progress of processing can be detected at every rotation angle of the lens  1  by following this procedure so that when the output of the sensor  320  for detecting completion of the processing shows ON at the entire peripheral portion of the lens  1 , the apparatus  10  decides that the processing has been completed on the entire peripheral portion of the lens  1 . 
   The Lens Unit 
   The lens unit  4  that is displaced by the elevating and lowering unit  3  in the direction of the Z-axis, as shown in  FIG. 3 , is guided by the two poles  401  and  402  standing on the base  20  in the vertical direction (i.e., in the direction of the Z-axis) in a manner such that the lens unit  4  can be freely displaced. Lens unit  4  is constructed to include the lens-holding shaft  41 , which is divided into two portions  41 R and  41 L, a motor  45  for driving the lens that rotates the lens-holding shaft  41 , and a motor  46  for the lens chuck that changes the holding pressure of the lens-holding shaft  41  that holds the lens  1 . 
   As shown in  FIG. 4 , the lens-holding shaft  41  that holds and rotates the lens  1  is placed at a position directly above the main rotating tool  50 . The vertical direction connects the axial line of the lens-holding shaft  41  and the axial line of the main shaft  51  as shown in FIG.  4 . 
   Connected to the frame  40  of the lens unit  4 , as shown in  FIGS. 3 and 6 , are arms  410  and  411  disposed to protrude in the direction towards the front of the apparatus  10  (i.e., to the lower left side of FIG.  3 ). Frame  40  and the arms  410  and  411  form a rectangle having three sides that is open to one side (i.e., “C”-shaped). The arms  410  and  411  support the lens-holding shaft  41 . 
   As shown in  FIGS. 3 and 6 , the lens-holding shaft  41  is divided at its center into two shaft portions  41 R,  41 L, which include a pushing or pressing shaft  41 R supported by the arm  410  and a holding shaft  41 L supported by the arm  411 . The shaft  41 L is supported by the arm  411  at the left side in  FIG. 6  in a manner that allows shaft  41 L to be freely rotated. The shaft  41 R is supported by the arm  410  at the right side in  FIG. 6  in a manner that allows the shaft  41 R to be freely rotated and to be displaced in the axial direction (i.e., in the direction of the X-axis). 
   The shafts  41 L and  41 R are rotated by the motor  45  for driving the lens via cogged belts  47 ,  48  and  49 . The cogged belts  47  and  48  are connected to each other through a rotatable shaft  430  so that the rotation angles of the shafts  41 L and  41 R are synchronized. 
   To achieve this synchronization, a gear  432  is engaged with the cogged belt  47  and is fixed to the shaft  41 L and a gear  431  is engaged with the cogged belt  48  and is fixed to the shaft  41 R. So that the shaft  41 R can be axially displaced, relative to the arm  410 , in the direction of the X-axis, the shaft  41 R is arrested in the direction of rotation by the key  433  disposed between the shaft  41 R and the inner periphery of the gear  431 . Key  433  can be relatively displaced in the direction of the X-axis, and moves along with shaft  41 R when displaced in the X-axis. 
   As shown in  FIG. 6 , a chuck mechanism driven by a motor  46  for the lens chuck is disposed at the end portion (i.e., at the right side in the Figure) of the shaft  41 R. 
   In the chuck mechanism, as shown in  FIG. 7 , an outer screw  442  is formed at the inner periphery of a gear  441  engaged with the cogged belt  440 . The outer screw  442  is engaged with an inner screw portion  443  formed at a driving member  461 , which can be brought into contact with the shaft  41 R in the axial direction. 
   The position of rotation of the shaft  41 R is decided by the motor  45  for driving the lens that is connected to the cogged belt  48 . As for determining the position of the shaft  41 R in the axial direction, as will be described later, gear  441  is rotated by the rotation of the motor  46  for the lens chuck, which causes the inner screw portion  443  of the driving member  461  engaged with the outer screw  442  to be displaced in the axial direction. Due to this axial displacement, the shaft  41 R is pushed in the direction of the X-axis by the driving member  461  and the end portion of the shaft  41 R is brought into contact with the lens  1  as shown in FIG.  6 . The pressure with which the shaft  41 R and the shaft  41 L hold the lens  1  is called the “holding pressure,” and can be set at a desired value by the motor  46  for the lens chuck. In the present embodiment, the holding pressure for the lens  1  is set by the value of the electric current driving the motor  46  for the lens chuck. Therefore, control of the electric current controls the motor  46  thereby setting the value of the holding pressure. 
   In  FIG. 7 , a receiver  141  of the lens holder is fixed at the tip of the left shaft  41 L of the lens-holding shaft  41 . To the receiver  141  of the lens holder, a lens holder  16  attaches. Prior to attaching lens holder  16  to the receiver  141 , a lens  1  to be processed is fixed in advance to the lens holder  16 . The lens holder  16  can be attached or released freely from receiver  141  and from lens  1 . 
   On the other hand, the shaft  41 R, disposed on the same axial line as that of the shaft  41 L, moves in the direction of the X-axis and holds the lens at the tip. In other words, the shaft  41 R moves towards the lens  1  by being driven by the motor  46  for the lens chuck and presses the lens  1  with a lens presser  142  disposed at the tip of shaft  41 R. The lens  1  is pressed towards the lens-holding shaft  41 L and held between the two shafts  41 R,  41 L by the holding pressure generated by motor  46 . The lens presser  142  is made of a resin, such as rubber, having elasticity so as to prevent damage to the lens  1 . 
   At the end face of the lens holder  16 , which is formed into a concave shape, the convex face  1   a  of the lens  1  is coaxially adhered via a double faced adhesive pad  161  and the lens presser  142  presses the concave face  1   b  of the lens  1 . The lens presser  142  is attached to the tip of the shaft  41 R so as to hold the lens  1  in a manner whereby the lens presser can be swung in any desired direction and the concave face  1   b  of the lens  1  is still pressed with excellent balance without any adverse local concentration of pressure on the lens. 
   As evident from  FIG. 7 , which illustrates the starting condition wherein lens  1  is fixed to the lens holder  16  attached to the shaft  41 L, the lens  1  is held by the lens presser  142  in the following manner: (a) the motor  46  for the lens chuck is driven in the prescribed direction (i.e., the positive rotation); (b) the gear  441  is rotated in the positive direction due to this movement of the motor  46 ; and (c) the shaft  41 R is displaced towards the left side in  FIG. 9  by the relative rotation of the outer screw  442  at the inner periphery of the gear  441  and the inner screw portion  443  of the shaft  41 R. A sensor rod  436  is connected to the driving member  461  having the inner screw portion  443 . The sensor rod  436  is placed parallel with the shaft  41 R using a plate  437  disposed at the end portion of the driving member  461 , and protruding to the side of the pushing shaft  41 R. Sensor rod  436  prevents rotation of the inner screw  443  because the sensor rod  436  is arrested in the direction of rotation by the plate  437  disposed at the end portion of the driving member  461  so that the driving member  461  is driven in the axial direction alone. 
   To displace the shaft  41 R in the direction of the X-axis and towards the left side of  FIG. 7  to achieve the lens holding condition, the driving member  461  pushes the shaft  41 R, which is thereby displaced in the direction of the X-axis until it presses the lens presser  142  to the concave face  1   b  of the lens  1 . 
   When the motor  46  for the lens chuck is further rotated, even though the lens presser  142  is in contact with the concave face  1   b  of the lens, the force for pressing (i.e., the lens holding pressure) the lens  1  increases and the electric current consumed by the motor  46  for the lens chuck increases. The pressure of holding the lens (also referred to as the lens holding pressure) is set at a desired value by detecting the electric current consumed by the motor  46 . 
   On the other hand, when the processing is completed, the motor  46  for the lens chuck is rotated in the reverse direction and the shaft  41 R is driven to the right side in  FIG. 6 , which illustrates the lens releasing condition. Under the lens releasing condition, the lens presser  142  is separated from the lens  1  and a prescribed gap is formed between the lens  1  and the lens presser  142  as shown in FIG.  7 . The shaft  41 R is displaced to the waiting position which allows attachment and detachment of the lens  1  and the lens holder  16  from the receiver  141 . When the driving member  461  is displaced in the direction of the right side in the Figure by a snap ring  471 , or the like, disposed at a shaft portion  470  having a small diameter, which protrudes from the right tip of the shaft  41 R to the right side in  FIG. 7 , the shaft portion  470  is pulled by the driving member  461  and displaced to the right side as shown. 
   Because the pushing shaft  41 R of the lens-holding shaft  41  is displaceable in the axial direction of the X-axis, it is necessary to have a mechanism that can determine the position of the shaft  41 R. When the shaft  41 R moves towards the lens  1 , as shown in  FIG. 6 , the position of shaft  41 R is detected by a sensor not shown in the Figure that detects when the lens-holding shaft  41  contacts the lens  1 , and the lens holding pressure is determined by monitoring the electric current consumed by the motor  46  for the lens chuck. However, when the shaft  41 R moves to the right side towards the waiting position shown in  FIG. 7 , the prescribed waiting position is detected by a limit switch  435  disposed close to the arm  410  of the lens unit  4 . Specifically, limit switch  435  detects the detecting portion  437   a  of the sensor rod  436  as it moves along with plate  437  and shaft  41 R to the waiting position shown in FIG.  7 . 
   In  FIG. 7 , the limit switch  435  is shown fixed to the arm  410  at the position supporting the gear  441 . 
   At the right end portion of the shaft  41 R, a sensor rod  436  is disposed via a plate  437  so as to be parallel with the shaft  41 R. Sensor rod  436  protrudes along side of the shaft  41 R. At the end portion of the sensor rod  436 , there is formed a detecting portion  437   a , which can contact the limit switch  435  at the prescribed waiting position. 
   When the shaft  41 R moves to the right side shown in the  FIG. 7 , the sensor rod  436  is fixed to the shaft  41 R and also moves to the right side. As shown in  FIG. 7 , the position where the detecting portion  437   a  contacts the limit switch  435  corresponds to the waiting position of the shaft  41 R, and the limit switch  435  is switched to ON at this position. 
   To determine the processing depth in accordance with the rotation angle of the lens  1 , the shaft  41 L is constructed to penetrate the arm  411  and a slit plate  143  that is fixed at the end portion of the shaft  41 L protrudes from the arm  411 . By detecting the position of rotation of the slit plate  143  using a photosensor  145  (i.e., a lens position sensor; also referred to as a “means for detecting the angle”) fixed to the arm  411 , the position (i.e., the rotation angle) of the lens  1  held by the lens-holding shaft  41 L is detected (i.e., measured). 
   In the lens unit  4  having the construction described above, when the lens  1  is fixed at the receiver  141  of the lens holder, the motor  46  for the lens chuck is driven and the lens-holding shaft  41 R is moved towards the left side of FIG.  7 . The lens  1  is then held, or fixed under pressure, when the lens presser  142  presses against the lens  1 . 
   As evident from  FIG. 3 , the main rotating tool  50  is fixed to the base plate  15  and is not displaced. The lens  1  supported by the lens unit  4  is displaced in the vertical direction relative to the main rotating tool  50  by the displacement of the elevating and lowering unit  3  in the direction of the Z-axis so that the processing can be conducted to the desired processing depth. 
   The position of the lens  1  for processing can be changed by changing the rotation angle of the motor  46  for driving the lens so that the peripheral portion of the lens can be processed to the desired processing depth. 
   The tool used for processing can be changed by changing the position of contact between the lens  1  and the main rotating tool  50  by adjusting the displacement of the base  20  in the direction of the X-axis. In other words, by moving base  20  in the direction of the X-axis, one of the grinders  50   a ,  50   b ,  50   c , and  50   d  can be selected for use in processing. 
   The Finishing Unit 
   In  FIG. 2 , the finishing unit  7 , which can be displaced in the direction of the Y-axis (i.e., in the direction of the inner side of the apparatus), is disposed at a position above the lens-holding shaft  41  (i.e., at the right side in FIG.  2 ). 
   The finishing unit  7 , as shown in  FIGS. 2 and 8 , is constructed with (a) a base  74  that can be displaced in the direction of the Y-axis, (b) a rotating tool  70  for chamfering the peripheral portion of the lens  1 , (c) a rotating tool  71  for grooving the outer peripheral face of the lens  1 , (d) a motor  72  for finishing that drives these rotating tools  70  and  71 , and (e) a motor  73  for driving the finishing unit that drives the base  74  in the direction of the Y-axis. These components are disposed at positions above the frame (unlabeled) which stands on the base plate  15 . 
   The rotating tools  70  and  71  stand in the direction of the Z-axis and are disposed at positions separated by the prescribed distance in the direction of the X-axis along the lens-holding shaft  41 . Rotating tools  70  and  71  are each supported by a shaft on the base  74 . 
   As shown in  FIG. 8 , a pair of guide shafts  701  and  702  are fixed to the tool frame (unlabeled) shown in  FIG. 2  at positions separated by the prescribed distance in the directions of the Y-axis and oriented so that the shafts  701  and  702  are parallel with each other. The guide shafts  701  and  702  pass through holes penetrating stopping members  74   a  and  74   b , respectively. Stopping members  74   a  and  74   b  are disposed at the right side and the left side of the base  74 , and the right side and the left side of the base  74  are supported so that base  74  can be displaced in the direction of the Y-axis. 
   At the right side of  FIG. 8 , a screw  75  is supported by a shaft running parallel with the guide shaft  701  at the tool frame placed on the base plate  15 . Screw  75  is driven by the motor  73  for driving the finishing unit via a belt  76 . 
   To the stopping member  74   a , through which penetrates the guide  701 , a driving member  77  is fixed. Driving member  77  is engaged with the screw  75  at an outer screw formed at the inner periphery of the driving member. The base  74  is driven in the direction of the Y-axis when the driving member  77  is displaced in the direction of the Y-axis in accordance with the rotation of the screw  75 . 
   The rotating tool  70  for chamfering the lens  1  is constructed to include a grinder (or a cutter) having the hemispherical shape with a radius R. The rotating tool  71  for chamfering, as shown in  FIG. 8 , is fixed at a lower end of a shaft  703 , which is disposed in the vertical direction. The shaft  703  is supported by a bearing  704  disposed on the base  74 . A pulley  705  is fixed at the upper end of the shaft  703 . The pulley  705  is connected through a belt  706  to a pulley  720  of the motor  72  (i.e., a drive including a single motor) for finishing so as to be rotated by motor  72 . The pulleys  705 ,  720  and belt  706  provide a means for transmission between motor  72  and shaft  703 . 
   The rotating tool  71  for grooving the lens  1  is constructed to include an end mill having a narrowed tip. This rotating tool  71 , as shown in  FIG. 8 , is fixed at the lower end of a shaft  713  that is disposed in the vertical direction. Shaft  713  is supported by a bearing  714  disposed on the base  74 . A pulley  715  is fixed at the upper end of the shaft  713 . The pulley  715  is connected through a belt  716  to a pulley  720  of the motor  72  for finishing so as to be rotated by the motor  72 . The pulleys  715 ,  720  and belt  716  provide a means for transmission between motor  72  and shaft  713 . 
   These rotating tools may be placed so that the distance in the direction of the Z-axis from the base  74  to the tip of each tool is set at the same value. Alternatively, these rotating tools may be placed so that the distance in the direction of the Z-axis from the base  74  to the tip of the rotating tool for grooving  71  may be set shorter than the distance from the base  74  to the tip of the rotating tool  70  for chamfering so that the rotating tool  71  for grooving does not interfere with the lens-holding shaft  41  or the receiver  141  of the lens holder during the chamfering. In other words, the distance from the main shaft  51  to the tip of the rotating tool  71  for grooving may be set at the same value with, or longer than, the distance from the main shaft  51  to the tip of the rotating tool  70  for chamfering. 
   Since two belts  706 ,  716  are wound around the pulley  720  of the motor  72  for finishing, the belts  706  and  716  are disposed at offset positions in the direction of the Z-axis. As shown in  FIG. 8 , a belt  716  is for driving the end mill and is wound at an upper position of the pulley  720 . Belt  706  is for driving the rotating tool  70  that has the spherical shape and this belt is wound at a lower position of the pulley  720 . Thus, the two rotating tools  70  and  71  are driven by one motor  72 . 
   As shown in  FIGS. 2 and 8 , the finishing unit  7  is placed at the prescribed waiting position where processing is not conducted. In this condition, the two rotating tools  70  and  71  are placed at inner positions within the apparatus  10  (i.e., at the right side in  FIG. 3 ) relative to the lens  1  and the styluses  60  and  61 . 
   When the finishing (i.e., the chamfering or the grooving) is conducted, as shown in  FIG. 14 , the two rotating tools  70  and  71  are displaced to positions directly above the lens-holding shaft  41  by driving the motor  73  for driving the finishing unit. 
   In this condition, wherein the measuring unit  6  is at the waiting position, the rotating tools  70  and  71  are advanced to positions between the styluses  60  and  61 . This position, wherein the rotating tools  70  and  71  at the positions vertically above the lens-holding shaft  41 , is called the “advanced position” (also referred to as the position for the processing) of the finishing unit  7 . 
   The finishing is conducted while the base  74  is placed at the advanced position shown in FIG.  9 . For example, when grooving is performed, the base unit  2  is displaced in the direction of the X-axis in accordance with the rotation angle of the lens-holding shaft  41  and the position of the lens  1  measured by the measuring unit  6  is determined as described above so that the axial line  71   c  of the rotating tool (i.e., the end mill)  71  faces towards the prescribed position of the peripheral portion  1   c  of the lens  1 . As shown in  FIGS. 11 ,  12 ,  13 ( a ) and  13 ( b ), the lens includes convex face  1   a , concave face  1   b , and peripheral portion  1   c . The peripheral portion  1   c  includes an outer peripheral portion  1   d  and an inner peripheral portion  1   e.    
   While the rotating tool  71  is rotated by driving the motor  72  for finishing and the lens  1  is rotated by driving the motor  45  for driving the lens, as shown in FIGS.  10 ( a ) and  10 ( b ), the lens unit  4  is elevated or lowered in the direction of the Z-axis in accordance with the rotation angle of the lens  1  and the base unit  2  is driven in the direction of the X-axis. A groove having the prescribed depth is formed along the peripheral portion  1   c  of the lens  1  by the rotating tool  71  that includes the end mill. Since the rotating tool  70  is connected to the motor  72  for finishing via the belt  706 , the rotating tool  70  makes idle rotation without conducting any processing. 
   When the chamfering process follows the grooving process, and after the outer peripheral portion  1   d  of the lens  1  is displaced in the lower direction from the tip of the rotating tool  70  by the prescribed distance, the base unit  2  is driven in the direction of the X-axis and the lens unit  4  is displaced to the position where the outer peripheral portion  1   d  of the lens  1  can face towards the rotating tool  70  having the hemispherical shape. 
   When chamfering the convex face  1   a , the base unit  2  is displaced in the direction of the X-axis so that the convex face  1   a  and the outer peripheral portion  1   d  are placed at a prescribed position directly below the side face of the rotating tool  70  having the hemispherical shape. As shown in  FIG. 11 , the lens unit  4  is elevated based on the rotation angle of the lens-holding shaft  41  and based on the position of the peripheral portion  1   c  of the lens  1  as measured by the measuring unit  6  as described above. The peripheral portion  1   c  of the lens  1  is brought into contact with the side face of the rotating tool  70  having the hemispherical shape. When chamfering of the convex face  1   a , the axial line  70   c  of the rotating tool  70  having the hemispherical shape is, as shown in  FIG. 11 , placed at a position shifted to the side of the convex face  1   a  and from the outer peripheral portion  1   d  of the lens  1 . 
   While the lens-holding shaft  41  is rotated by the motor  45  for driving the lens, the lens unit  4  is elevated or lowered and the base unit  2  is displaced in the direction of the X-axis based on the rotation angle of the lens-holding shaft  41  and based on the position of the peripheral portion  1   c  in accordance with the rotation angle, wherein the position of the peripheral portion is measured by the measuring unit  6  as described above. Thus, while lens-holding shaft  41  rotates, the lens unit  4  is elevated or lowered, and the base unit  2  is displaced along the X-axis, chamfering of the outer peripheral portion  1   d  of the convex face  1   a  of the lens  1  is conducted. 
   When chamfering of the inner peripheral portion  1   e  of the concave face  1   b  of the lens  1  is conducted in succession following completion of chamfering of the outer peripheral portion  1   d  of the convex face  1   a , the peripheral portion  1   c  of the lens  1  is displaced in the lower direction from the tip of the rotating tool  71  by the prescribed distance. Then, as shown in  FIG. 12 , the base unit  2  is displaced in the direction of the X-axis so that the lens unit  4  is displaced to a position wherein the axial line  70   c  of the rotating tool  70  is placed at the right side of the peripheral portion  1   c  of the lens  1  as shown in  FIG. 12 , and the side of the rotating tool  70  having the hemispherical shape faces towards the inner peripheral portion  1   e  of the lens  1 . 
   When chamfering the inner peripheral portion  1   e  of the lens, the lens unit  4  is elevated based on the rotation angle of the lens-holding shaft  41  and the position of the peripheral portion  1   c  of the lens  1  measured by the measuring unit  6  described above. While the lens-holding shaft is rotated by the motor  45  for driving the lens, the lens unit  4  is elevated or lowered and the base unit  2  is displaced in the direction of the X-axis based on the rotation angle of the lens-holding shaft  41  and the position of the peripheral portion  1   c  in accordance with the rotation angle, wherein the position of the peripheral portion  1   c  is measured by the measuring unit  6  described above. Thus, while lens-holding shaft  41  rotates, the lens unit  4  is elevated or lowered, and the base unit  2  is displaced along the X-axis, chamfering of the inner peripheral portion  1   e  of the concave face  1   b  of the lens  1  is conducted. 
   When the finishing is completed, the base  74  is driven to the waiting position, the motor  72  for finishing is stopped and the lens unit  4  is moved to the prescribed position for attachment and detachment for the lens holder  16  from the receiver  141 . Thus, the processing is completed. 
   The Control Unit 
   The lens processing apparatus  10  is constructed to include the various mechanisms (units) described above, and further has a control unit  9  (also referred to as the “central unit”) for controlling these various mechanisms as shown in FIG.  14 . 
   As shown in  FIG. 14 , the control unit  9  includes a microprocessor (CPU)  90 , a means for memory (i.e., a memory, a hard disk and the like)  91  and an I/O control portion (i.e., an interface)  92  connected to the CPU  90 , which is connected to the motors and the sensors of the apparatus  10 . The control unit  9  reads the data describing the shape of the lens frame that is sent from the apparatus  900  for measuring the shape of the frame. The apparatus  900  for measuring the shape of the frame is placed outside of the apparatus  10 , but it is connected to send lens frame shape data to the control unit  9 . The control unit  9  also reads inputted data from various sensors, and generates various output control signals to drive the various motors of the apparatus  10  so that the prescribed processing is conducted based on the properties (i.e., the material, the hardness and the like) of the lens  1 , which is set by the operation portion  13 . A suitable apparatus  900  for measuring the shape of the frame is the apparatus disclosed in Japanese Patent Application Laid-Open No. Heisei 6(1994)-47656; however, other similar types of devices can be used without departing from the scope of the present invention. 
   The control unit  9  also comprises a servomotor control portion  93  that positions the lens unit  4  in the directions of the X-axis and the Z-axis by driving the X-axis motor  25  of the base unit  2  and the Z-axis motor  42  of the elevating and lowering unit  3 , respectively. 
   The motor  55  for driving the main rotating unit  50  and the motor  72  for finishing, which drives the rotating tools  70  and  71 , are each connected to the I/O control portion  92  via driving portions  901  and  902 , respectively, so that the condition of rotation, or the speed of rotation, is controlled in accordance with the direction (i.e., control signals) from the microprocessor  90 . 
   The motor  46  for the lens chuck, which controls the holding pressure applied to the lens  1  by changing the position of the shaft  41 R of the lens-holding shaft  41 , is connected to the I/O control portion  92  via a driving portion  911  so as to control the holding pressure in accordance with the driving electric current. 
   The motor  45  for driving the lens is connected to the I/O control portion  92  via a driving portion  912  that controls the rotation angle of the lens-holding shaft  41 , and therefore the rotation angle of the lens  1 . The microprocessor  90  directs the processing position of the lens  1  based on the data describing the shape of the lens frame obtained from the apparatus  900  for measuring the shape of the frame. In addition to the lens frame shape data, microprocessor  90  also uses rotation angle data provided by the sensor  145  for detecting the position of the lens, which detects the rotation angle of the lens  1  to generate control signals for the Z-axis motor. Microprocessor  90  uses these control signals to drive the Z-axis motor  42  so that the processing depth, in accordance with the rotation angle based on the data describing the shape of the lens frame, is achieved. 
   When the prescribed processing depth is achieved, a sensor  320  for detecting completion of processing, which will be described later in detail, is switch to ON and the actual position of processing (i.e., the completed processing position) is fed back to the microprocessor  90 . 
   The motor  73  for driving the finishing unit that drives the finishing unit  7  in the direction of the Y-axis is connected to the I/O control portion  92  via a driving portion  913 , which controls the positioning. 
   Outputs from linear scales (not shown in the Figure) connected to the styluses  60  and  61  of the measuring unit  6  are also input into the microprocessor  90 . 
   The operation portion  13 , disposed on the front of the cover of the apparatus  10  for processing a lens, is connected to the I/O control portion  92  and transfers the direction data inputted by the operator (for example, the material of the lens  1  and whether the processing should be with or without the beveled processing or the grooving) to the microprocessor  90 . Microprocessor  90  outputs the response to these operator inputted directions so that the information corresponding to the processing content is outputted to the display portion  12  via the driving portion  921 . 
   By operating the control portion  9 , data for flat grinding and data for beveled grinding that are used for flat grinding and for beveled grinding, respectively, are created by calculation from the data describing the shape of the lens frame. Furthermore, data for grooving and data for chamfering are created by calculation based on the positions of the entire peripheral portion (i.e., coordinates of apices in the section of the lens at the side of the convex face  1   a  and at the side of the concave face  1   b ) of the lens  1 , wherein these positions of the entire peripheral portion are measured by the measuring unit  6  based on the data describing the shape of the lens frame. 
   During the processing of a lens, the servomotor control portion  93  drives the X-axis motor and the Z-axis motor in accordance with the lens processing data corresponding to the rotation angle of the lens  1 , which is also the rotation angle of the lens-holding shaft  41 . The rotation angle of the lens  1  is detected by the sensor  145  for detecting the position of the lens so that the lens  1  is displaced relative to the rotating tool  50  in accordance with the lens position data provided by the sensor  145 . The processing is conducted in this manner. 
   Outline of the Processing 
   The lens processing procedures performed using the apparatus  10  for processing a lens will be described as follows. The outlined method includes both preparatory steps and lens processing steps. 
   First, the lens  1  is set into the lens-holding shaft  41 . Next, the data describing the shape of the lens frame are read by the apparatus  900  for measuring the shape of the frame, which measures the shape of a lens frame that is outside of the apparatus  10 . Subsequently, an operator uses the operation portion  13  to input the directions corresponding to the conditions of the lens processing, such as the material of the lens  1  and whether the processing should be with or without the beveled processing or the grooving. To begin the lens processing steps, the operator inputs the direction signal for starting the processing using the operation portion  13 . Then, the steps of the lens processing are conducted. 
   When the start of lens processing is directed, the pressing shaft  41 R of the lens-holding shaft  41  is displaced to the position for holding the lens shown in  FIG. 6  by driving the motor  46  for the lens chuck and the holding pressure is set in accordance with the material of the lens  1 . 
   To process the lens  1 , the main rotating tool  50  is rotated by driving the motor  55 . The lens unit  4  is lowered by driving the elevating and lowering unit  3  and the base unit  2  is displaced in the direction of the X-axis to the position where the peripheral portion  1   c  of the lens  1  is faced towards the rough grinder  50   a  for flat grinding of the main rotating tool  50 . The processing depth is provided and set by the elevating and lowering unit  3  while the lens  1  is rotated by the motor  45  for driving the lens. Then, the rough grinding is conducted to achieve the processing depth calculated at every rotation angle of the lens-holding shaft  41 . 
   When the sensor  320  for detecting completion of the processing, which is part of the above lens unit  4 , gives the ON signal for the entire periphery of the lens, sensor  320  has detected that the grinding step has been completed. 
   Once the rough processing is completed, the lens unit  4  is temporarily elevated. The base unit  2  is moved in the direction of the X-axis to the position where the lens  1  faces towards the finishing grinder  50   b  for flat grinding of the main rotating tool  50 . Then, the finishing grinding is conducted in the same manner as is conducted for the rough grinding step. When the sensor  320  for detecting completion of the processing of the lens unit  4  gives the ON signal for the entire periphery of the lens  1 , the finishing processing on the entire peripheral portion of the lens  1  is completed. 
   When the grooving of the lens by the finishing unit  7  is necessary, the grooving is conducted by forming a groove at the peripheral portion  1   c  of the lens  1  by using the rotating tool  71  of the end mill as shown in FIG.  10 . Then, the chamfering of both faces  1   a ,  1   b  of the peripheral portion of the lens  1  is conducted by successively bringing the peripheral portions  1   d  and  1   e  of the lens  1  at the side of the concave face  1   a  and the convex face  1   b , respectively, into contact with the side of the rotating tool  70  having the hemispherical shape by driving the base unit  2  in the direction of the X-axis. 
   Once grooving and chamfering steps are completed, the pressing shaft  41 R of the lens-holding shaft  41  is displaced to the position for releasing the lens shown in  FIG. 7  by driving the motor  46  for the lens chuck. With the apparatus  10  in the lens releasing condition, the operator removes the completely processed lens  1  from the apparatus. 
   Workings of the Apparatus in Accordance with the Present Invention 
   As described above, because the rotating tool  70  having the hemispherical shape for chamfering and the rotating tool  71  constructed to include the end mill for grooving are independently formed (i.e., are separate structures), and because each of these tools are disposed at positions separated by the prescribed distance along the lens-holding shaft  41 , the rotating tool  71  for grooving does not interfere with the lens-holding shaft  41  or the receiver  141  of the lens holder during the chamfering step even when the lens  1  has a small diameter. Therefore, chamfering and grooving can be conducted accurately for a lens  1  having any size. 
   Because the rotating tool  70  for chamfering and the rotating tool  71  for grooving used in the finishing steps are fixed at the base  74  that is displaceable in the direction of the Y-axis, and because the positioning of the lens is conducted by the lens unit  4  that is displaceable in the vertical direction and in the direction of the main shaft  51 , it is not necessary that lens positioning be controlled by the finishing unit. It is merely necessary that the finishing unit be accurately positioned between the advanced position shown in FIG.  9  and the retired position shown in FIG.  8 . Therefore, the mechanism of the finishing unit can be simplified, thereby decreasing the cost of production. In addition, because the two rotating tools  70  and  71  are driven efficiently by a single motor  72 , there is no need to provide a second motor to drive both tools. Thus, there is no need to increase the size of the apparatus which keeps the costs of production down. 
   Because the lens unit  4  is displaceable relative to the fixed rotating tools  70  and  71 , and because the lens unit  4  can be positioned in the same manner for flat grinding or for beveled grinding in which the lens  1  is displaced relative to the main rotating tool  50 , the main processing and the finishing processing, such as the chamfering and the grooving of the peripheral portion of the lens, can be conducted by a single positioning mechanism under a single control unit that directs positioning. Therefore, the complexity of the positioning mechanism and the control of the positioning mechanism can be minimized so as to keep the cost of production down. 
   The rotating tool  70  having the hemispherical shape is formed with a grinder or a cutter having diamond or the like and has the prescribed radius R as shown in FIG.  13 ( a ). As shown in FIG.  13 ( b ), when the lens  1 , or the lens-holding shaft  41 , is elevated from the lower position in the Figure, the angle of chamfering θ at the portion to be chamfered (in this case, the inner peripheral portion  1   e ) is decided in accordance with the processing depth Lx in the direction of the X-axis (i.e., the displacement in the direction of the axis of rotation of the lens  1 ) and the processing depth Lr in the direction of the Z-axis (i.e., the displacement in the radial direction of the lens  1 ). 
   The processing depth Lx is the distance in the direction of the X-axis from an apex C to an apex D. The apex C is the intersection of the line of the peripheral face  1   c  and the line of the concave face  1   b  in the section of the lens  1  before the processing at one rotation angle. The apex D is the intersection of the line of the outer peripheral face  1   d  and the line S chamfered from face  1   e  in the section of the lens  1  after the processing at the same rotation angle. The processing depth Lz is the distance in the direction of the Z-axis (i.e., in the radial direction of the lens) from the apex C to an apex E. The apex E is the intersection of the line of the concave face  1   b  and the line S chamfered from face  1   e  in the section of the lens  1  after the processing. The angle θ between the outer peripheral face  1   d  and the chamfered portion of face  1   e  can be set as desired in accordance with the ratio of Lx to Lz. The X- and Y-coordinates of the apex C change depending on the rotation angle of lens  1  (which is also the rotation angle of the lens-holding shaft  41 ). These coordinates are values obtained by the measurement performed in advance using the styluses  60  and  61  of the measuring unit  6  as described above to measure the side of the convex face  1   a  and the side of the concave face  1   b.    
   The chamfered portion of face  1   e  has a concave shape as shown in  FIG. 13  because the rotating tool  70  having the hemispherical shape having the radium R is used. The angle between the straight line S passing through the apices D and E after processing and the outer peripheral face  1   d  is used to define the chamfering angle θ. 
   Therefore, for the control of positioning in accordance with the chamfering angle θ of the lens  1 , as shown in FIG.  13 ( b ), the ratio of the processing depths Lx to Lz is obtained when the chamfering angle θ is decided. Then, when either one of the two processing depths in the direction of the X-axis or in the direction of the Z-axis (i.e., in the radial direction) is decided, both of the distances Lx and Lz from the apex C can be determined before processing to the apices D and E, respectively. When circles having a radius R, which is the same as the radius R of the hemispherical shape of the rotating tool, are drawn at the centers placed at these apices D and E, the intersection of these circles gives the X- and Z-coordinates of the center of the sphere  70   cr  of the tool as shown in FIG.  13 ( b ). 
   When the chamfering angle θ and the chamfering amount (i.e., the processing depth) are set as described above, the relative positions of the lens  1  and the rotating tool  70  having the hemispherical shape in accordance with the desired chamfering angle θ, and the desired processing depth (i.e., the position of the axial line of the lens-holding shaft  41   c  in the direction of the Z-axis (Δz) and the position of the apex C in the direction of the X-axis (Δx) in FIG.  13 (A)) can be determined by calculating the coordinates (Xr, Zr) of the center of the sphere  70   cr  of the rotating tool  70  having the hemispherical shape from the coordinates of the apex C measured before processing at every rotation angle. When the rotating tool  70  for chamfering is kept rotating at the prescribed position (i.e., on the vertical line of the lens-holding shaft  41 ), and the lens unit  4  is elevated and lowered and, simultaneously, displaced in the direction of the X-axis by the displacement of the base unit  2  while the lens  1  is also rotated, the chamfering at the convex side and at the concave side of the lens  1  can be achieved to the desired chamfering angle θ. This allows the finishing unit  7  to chamfer to the desired chamfering depth using a simplified mechanism for the rotating tool. Moreover, since chamfering can be conducted in various manners using a single rotating tool having the hemispherical shape  70 , exchange of tools is not necessary and the processing time is decreased. 
   As shown in  FIG. 13 , chamfering is conducted at the side of the concave face  1   b  at the inner peripheral portion  1   e  of the lens  1 . For chamfering at the side of the convex face  1   a , the relative distance Δz between the lens-holding shaft  41  and the rotating tool  70  in the direction of the Z-axis and the relative distance Δx between the coordinate of the apex of the lens  1  and the center  70   cr  of the rotating tool  70  are determined from the coordinates of the apices, the chamfering angle θ and the chamfering depth at every rotation angle based on the data corresponding to the position of the peripheral portion  1   c  of the lens, which are set in advance. 
   Since the radius R of the rotating tool  70  having the hemispherical shape is constructed independently of the rotating tool  71  for grooving, the width of the formed groove is not restricted, which is unlike in the conventional case wherein chamfering and grooving are conducted by using a single ball end mill. Therefore, the radius R can be set at the most suitable value for chamfering without worry about interference. 
   In the above embodiment, the present invention is applied to the apparatus  10  in which the processing of the lens  1  is conducted by displacing the lens-holding shaft  41  in the vertical direction. The present invention can also be applied to an apparatus having an arm which supports a lens-holding arm in a manner such that the lens-holding arm can be swung in a conventional manner. For example, when an arm and a positioning member for deciding the angle of the arm can be set in a manner such that the arm and the positioning member can be brought into contact with, or separated from, each other, the relative displacement between the arm and the positioning member is detected after being amplified by a sensor arm. In this case, the position of the contact between the arm and the positioning member is detected based on the relative displacement amplified by the sensor arm, so the same effect as that described for the above embodiment can be obtained. The present invention can be applied in the same manner to apparatuses in which a lens-holding shaft is displaced in the horizontal direction as well. 
   While the present invention has been described with reference to certain illustrative embodiments, one of ordinary skill in the art will recognize that additions, deletions, substitutions, modifications and improvements can be made while remaining within the spirit and scope of the present invention as defined by the appended claims.