Abstract:
A method of processing an eyeglass lens includes: a first step of obtaining an actual three-dimensional target lens shape from a rim of an eyeglass frame; a second step of obtaining a circumferential length of the actual three-dimensional target lens shape and a two-dimensional target lens shape based on the actual three-dimensional target lens shape; a third step of transmitting at least the two-dimensional target lens shape without transmitting the circumferential length of the actual three-dimensional target lens shape; a fourth step of obtaining a circumferential length of a three-dimensional target lens shape restored based on the transmitted two-dimensional target lens shape; a fifth step of obtaining a bevel path having a circumferential length that substantially accords with the circumferential length of the restored three-dimensional target lens shape; and a sixth step of forming a bevel on a peripheral edge surface of the lens based on the obtained bevel path.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention is related to a target lens shape measuring apparatus, an eyeglass lens processing system having the same and an eyeglass lens processing method.  
         [0002]     U.S. Pat. No. Re.35,898 (Japanese Unexamined Patent Publication: H05-212661), for example, owned by the assignee of the present application discloses a method of processing an eyeglass lens as follows. That is, firstly, a three-dimensional target lens (shape) of a rim (lens frame) of an eyeglass frame is measured and a circumferential length thereof (hereinafter referred to as “three-dimensional target lens circumferential length) is obtained. Secondly, a bevel path having a circumferential length substantially identical to the obtained three-dimensional target lens circumferential length is obtained. Then, a bevel is formed on a peripheral (circumferential) edge surface of the lens based on the obtained bevel path. By obtaining the bevel path so as to be substantially identical to the three-dimensional target lens circumferential length with the above-described manner, the lens formed with the bevel can be fitly fitted to the rim.  
         [0003]     Recently, the lenses are processed concentrically at a lens processing center, and data for processing is transmitted from an eyeglass shop to the lens processing center through-a communication line.  
         [0004]     In such as a case, if the data on the three-dimensional target lens circumferential length is transmitted as the data for processing, there is no problem. However, if the data on the three-dimensional target lens circumferential length is not transmitted, the lens may not be able to be processed so as to be fitly fitted to the rim.  
       SUMMARY OF THE INVENTION  
       [0005]     In view of the foregoing problem, the present invention has been conceived with an object to provide a target lens shape measuring apparatus, an eyeglass lens processing system having the same and an eyeglass lens processing method, that allows performing high precision lens processing even when the data on the three-dimensional target lens circumferential length cannot be transmitted to the processing side.  
         [0006]     In order to achieve the foregoing object, the present invention provides the following.  
         [0007]     (1) A method of processing an eyeglass lens comprising: 
        a first step of obtaining an actual three-dimensional target lens shape from a rim of an eyeglass frame;     a second step of obtaining a circumferential length of the actual three-dimensional target lens shape and a two-dimensional target lens shape based on the actual three-dimensional target lens shape;     a third step of transmitting at least the two-dimensional target lens shape without transmitting the circumferential length of the actual three-dimensional target lens shape;     a fourth step of obtaining a circumferential length of a three-dimensional target lens shape restored based on the transmitted two-dimensional target lens shape;     a fifth step of obtaining a bevel path having a circumferential length that substantially accords with the circumferential length of the restored three-dimensional target lens shape; and     a sixth step of forming a bevel on a peripheral edge surface of the lens based on the obtained bevel path.        
 
         [0014]     (2) The method according to (1) further comprising a step of obtaining a radius of a sphere in which a circumferential length of an imaginary three-dimensional target lens shape obtained by projecting the two-dimensional target lens shape onto the sphere substantially accords with the circumferential length of the actual three-dimensional target lens shape, 
        wherein in the third step, the two-dimensional target lens shape and the sphere radius are transmitted, and     wherein in the fourth step, the circumferential length of the restored three-dimensional target lens shape is obtained based on the transmitted two-dimensional target lens shape and the transmitted sphere radius.        
 
         [0017]     (3) The method according to (1) further comprising: 
        a step of obtaining a radius of a sphere on which the actual three-dimensional target lens shape is; and     a step of obtaining a corrected two-dimensional target lens shape in which a circumferential length of an imaginary three-dimensional target lens shape obtained by projecting the corrected two-dimensional target lens shape onto the sphere substantially accords with the circumferential length of the actual three-dimensional target lens shape,     wherein in the third step, the corrected two-dimensional target lens shape and the sphere radius are transmitted, and     wherein in the fourth step, the circumferential length of the restored two-dimensional target lens shape is obtained based on the transmitted corrected two-dimensional target lens shape and the transmitted sphere radius.        
 
         [0022]     (4) The method according to (1) further comprising a step of obtaining a corrected two-dimensional target lens shape in which a circumferential length of the corrected two-dimensional target lens shape substantially accords with the circumferential length of the actual three-dimensional target lens shape, 
        wherein in the third step, the corrected two-dimensional target lens shape is transmitted, and     wherein in the fourth step, the circumferential length of the restored three-dimensional target lens shape is obtained the circumferential length of the transmitted corrected two-dimensional target lens shape.        
 
         [0025]     (5) The method according to (1) further comprising a step of obtaining a correction coefficient for correcting the two-dimensional target lens shape so that the circumferential length of the corrected two-dimensional target lens shape substantially accords with the circumferential length of the actual three-dimensional target lens shape, 
        wherein in the third step, the two-dimensional target lens shape and the correction coefficient are transmitted, and     wherein in the fourth step, the circumferential length of the restored three-dimensional target lens shape is obtained based on the circumferential length of the transmitted two-dimensional target lens shape and the transmitted correction coefficient.        
 
         [0028]     (6) An eyeglass lens processing system comprising: 
        a target lens shape measuring apparatus that obtains an actual three-dimensional target lens shape from a rim of an eyeglass frame;     an eyeglass lens processing apparatus that forms a bevel on a peripheral edge surface of an eyeglass lens; and     a transmitting portion that connects the measuring apparatus to the processing apparatus,     wherein the measuring apparatus includes a first arithmetic portion for obtaining a circumferential length of the actual three-dimensional target lens shape and a two-dimensional target lens shape based on the actual three-dimensional target lens shape,     wherein the transmitting portion transmits at least the two-dimensional target lens shape without transmitting the circumferential length of the actual three-dimensional target lens shape,     wherein the processing apparatus includes a second arithmetic portion for obtaining a circumferential length of a three-dimensional target lens shape restored based on the transmitted two-dimensional target lens shape, and obtaining-a bevel path having a circumferential length that substantially accords with the circumferential length of the restored three-dimensional target lens shape.        
 
         [0035]     (7) The eyeglass lens processing system according to (6), 
        wherein the first arithmetic portion obtains a radius of a sphere in which a circumferential length of an imaginary three-dimensional target lens shape obtained by projecting the two-dimensional target lens shape onto the sphere substantially accords with the circumferential length of the actual three-dimensional target lens shape,     wherein the transmitting portion transmits the two-dimensional target lens shape and the sphere radius, and     wherein the second arithmetic portion obtains the circumferential length of the restored three-dimensional target lens shape based on the transmitted two-dimensional target lens shape and the transmitted sphere radius.        
 
         [0039]     (8) The eyeglass lens processing system according to (6), 
        wherein the first arithmetic portion obtains a radius of a sphere on which the actual three-dimensional target lens shape is, and obtains a corrected two-dimensional target lens shape in which a circumferential length of an imaginary three-dimensional target lens shape obtained by projecting the corrected two-dimensional target lens shape onto the sphere substantially accords with the circumferential length of the actual three-dimensional target lens shape,     wherein the transmitting portion transmits the corrected two-dimensional target lens shape and the sphere radius, and     wherein the second arithmetic portion obtains the circumferential length of the restored two-dimensional target lens shape based on the transmitted corrected two-dimensional target lens shape and the transmitted sphere radius.        
 
         [0043]     (9) The eyeglass lens processing system according to (6), 
        wherein the first arithmetic portion obtains a corrected two-dimensional target lens shape in which a circumferential length of the corrected two-dimensional target lens shape substantially accords with the circumferential length of the actual three-dimensional target lens shape,     wherein the transmitting portion transmits the corrected two-dimensional target lens shape, and     wherein in the fourth step, the circumferential length of the restored three-dimensional target lens shape is obtained based on the circumferential length of the transmitted corrected two-dimensional target lens shape.        
 
         [0047]     (10) The eyeglass lens processing system according to (1), 
        wherein the first arithmetic portion obtains a correction coefficient for correcting the two-dimensional target lens shape so that the circumferential length of the corrected two-dimensional target lens shape substantially accords with the circumferential length of the actual three-dimensional target lens shape,     wherein the transmitting portion transmits the two-dimensional target lens shape and the correction coefficient, and     wherein the second arithmetic portion obtains the circumferential length of the restored three-dimensional target lens shape based on the circumferential length of the transmitted two-dimensional target lens shape and the transmitted correction coefficient.        
 
         [0051]     (11) A target lens shape measuring apparatus comprising: 
        a measuring portion that obtains an actual three-dimensional target lens shape from a rim of an eyeglass frame;     an arithmetic portion that obtains a circumferential length of the actual three-dimensional target lens shape and a two-dimensional target lens shape based on the actual three-dimensional target lens shape; and     an outputting portion that outputs at least the two-dimensional target lens shape without outputting the circumferential length of the actual three-dimensional target lens shape.        
 
         [0055]     (12) The target lens shape measuring apparatus according to (11), 
        wherein the arithmetic portion obtains a radius of a sphere in which a circumferential length of an imaginary three-dimensional target lens shape obtained by projecting the two-dimensional target lens shape onto the sphere substantially accords with the circumferential length of the actual three-dimensional target lens shape, and     the outputting portion transmits the two-dimensional target lens shape and the sphere radius.        
 
         [0058]     (13) The target lens shape measuring apparatus according to (11), 
        wherein the arithmetic portion obtains a radius of a sphere on which the actual three-dimensional target lens shape is, and obtains a corrected two-dimensional target lens shape in which a circumferential length of an imaginary three-dimensional target lens shape obtained by projecting the corrected two-dimensional target lens shape onto the sphere substantially accords with the circumferential length of the actual three-dimensional target lens shape, and     wherein the transmitting portion transmits the corrected two-dimensional target lens shape and the sphere radius.        
 
         [0061]     (14) The target lens shape measuring apparatus according to (11), 
        wherein the arithmetic portion obtains a corrected two-dimensional target lens shape in which a circumferential length of the corrected two-dimensional target lens shape substantially accords with the circumferential length of the actual three-dimensional target lens shape, and     wherein the outputting portion transmits the corrected two-dimensional target lens shape.        
 
         [0064]     (15) The target lens shape measuring apparatus according to (11), 
        wherein the arithmetic portion obtains a correction coefficient for correcting the two-dimensional target lens shape so that the circumferential length of the corrected two-dimensional target lens shape substantially accords with the circumferential length of the actual three-dimensional target lens shape, and     wherein the outputting portion transmits the two-dimensional target lens shape and the correction coefficient.       
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0067]      FIG. 1  is a schematic block diagram of an eyeglass lens processing system;  
         [0068]      FIG. 2  is a schematic block diagram of a measuring mechanism incorporated in a target lens shape measuring apparatus;  
         [0069]      FIG. 3  is a schematic block diagram of a processing mechanism incorporated in an eyeglass lens processing apparatus;  
         [0070]      FIG. 4  is a schematic block diagram of a lens shape measuring unit;  
         [0071]      FIG. 5  is a schematic block diagram showing a control system of the processing apparatus;  
         [0072]      FIG. 6  is a graphic drawing for explaining a correction method of a two-dimensional target lens shape;  
         [0073]      FIG. 7A  and  FIG. 7B  are graphic drawings for explaining a correction method of a two-dimensional target lens shape; and  
         [0074]      FIG. 8  is a graphic drawing for explaining an imaginary three-dimensional target lens shape created when the two-dimensional target lens shape is projected onto a sphere. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0075]     Embodiments according to the present invention will be described hereunder with reference the accompanying drawings.  FIG. 1  is a schematic block diagram of an eyeglass lens processing system.  
         [0076]     In an eyeglass shop  10 , an order-issuing terminal  11  and a target lens shape measuring apparatus  100  are installed. In a lens processing workshop  20  an order-receiving terminal  21  and an eyeglass lens processing apparatus  200  are installed. The lens processing workshop  20  includes a lens manufacturer, a lens processing center and the like. The order-issuing terminal PC  11  and the order-receiving terminal  21  are communicably connected to a server  30  of a communications network NW. Ordering data including information on a target lens shape is transmitted from the order-issuing terminal  11 , and is received by the order-receiving terminal  21  via the server  30 . Each of the order-issuing terminal  11  and the order-receiving terminal  21  are a computer provided with a display monitor and an inputting device such as a keyboard and a mouse. The order-receiving terminal  21  of the lens processing workshop  20  is connected to the order-issuing terminals  11  of a plurality of eyeglass shops  10 . Although  FIG. 1  only shows one each of the eyeglass shop  10  and the lens processing workshop  20 , actually a plurality of these are connected to one another via the communications network NW.  
         [0077]      FIG. 2  is a schematic block diagram of a measuring mechanism  120  incorporated in the target lens shape measuring apparatus  100 . The measuring mechanism  120  includes a rotating base  122  driven by a pulse motor  121 , a fixed block  125  fixed to the rotating base  122 , a horizontally-moving carriage  127  movably supported by the fixed block  125  in a left and right direction in  FIG. 2 , a vertically-moving carriage  129  movably supported by the horizontally-moving carriage  127  in an upward and downward direction in  FIG. 2 , a gauge head shaft  131  rotatably attached to the vertically-moving carriage  129 , a gauge head  133  attached at the upper end of the gauge head shaft  131 , with the tip thereof aligned with the central axis of the gauge head shaft  131 , a motor  135  for vertically driving the vertically-moving carriage  129 , an encoder  136  that detects a travel of the vertically-moving carriage  129 , a motor  138  for horizontally driving the horizontally-moving carriage  127 , and an encoder  139  that detects a travel of the horizontally-moving carriage  127 . The motors and the encoders are connected to an arithmetic control unit  150 .  
         [0078]     When measuring a target lens shape, the eyeglass frame is fixed to a frame holder (for example, according to Japanese Unexamined Patent Publication No.2000-314617 (U.S. Pat. No. 6,325,700)) which is not shown in  FIG. 2 , before starting the measurement. The arithmetic control unit  150  drives the motors  135  and  138  such that the tip of the gauge head  133  contacts an inner groove of the rim of the eyeglass frame. Then, the pulse motor  121  is rotated at predetermined pulses per rotation. This rotation causes the gauge head  133  and the horizontally-moving carriage  127  to horizontally move along a radius vector of the rim, and the encoder  139  detects the movement. Also this rotation causes the gauge head  133  and the vertically-moving carriage  129  to vertically move along a curve (warp) of the rim, and the encoder  136  detects the movement. The three-dimensional shape (three-dimensional target lens shape) of the inner groove of the rim is measured as (rn, θn, zn) (n=1, 2, . . . , N) based on a rotational angle (radius vector angle) θ of the rotating base  122  driven by the pulse motor  121 , a horizontal travel(radius vector length) r detected by the encoder  139  and a vertical travel z detected by the encoder  136 . It is to be noted that the details of this measuring mechanism are basically similar to those described in Japanese Unexamined Patent Publication No. 2000-314617 (U.S. Pat. No. 6,325,700). The arithmetic control unit  150  obtains a frame PD (separation between geometrical centers of the left and right rims), through the measurement of the left and right rims. With respect to the three-dimensional target lens shape, the shape data of a rim may be symmetrically inverted, to be employed as the shape data of the other rim.  
         [0079]      FIG. 3  is a schematic block diagram of a processing mechanism  240  incorporated in the eyeglass lens processing apparatus  200 . A lens to be processed LE is held by two lens rotating shafts  211 R and  211 L attached to a carriage  210 , to be ground by a grindstone  251  attached to a grindstone rotating shaft  250 . The grindstone  251  includes three grindstones, namely a roughing grindstone  251   a  for plastics, a roughing grindstone  251   b  for glasses and a finishing grindstone  251   c  provided with a beveling groove and a flat processing surface. The grindstone rotating shaft  250  is rotated by a motor  253 .  
         [0080]     A motor mounting block  214  is attached on the left arm side of the carriage  210  and is rotatable about an axial line of the lens rotating shaft  211 L. A lens rotating motor  215  is mounted on the block  214 , so that the rotation of the motor  215  is transmitted to the lens rotating shaft  211 L via a gear and so on. A chuck motor  212  is attached on the right arm side of the carriage  210  for moving the lens rotating shaft  211 R in an axial direction.  
         [0081]     The carriage  210  is rotatable and slidable with respect to a carriage shaft  220  disposed parallel to the lens rotating shafts  211 R and  211 L, so as to be driven by a motor  222  in a left and right direction together with a moving arm  221 .  
         [0082]     A swinging block  230  is attached to the moving arm  221  and is rotatable about an axial line that is aligned with the center of the grindstone rotating shaft  250 . The swinging block  230  is provided with a carriage driving motor  231  and a feeding screw  232 , and the rotation of the motor  231  is transmitted to the feeding screw  232  via a belt and so on. A guide block  233  is fixed to the upper end of the feeding screw  232  so as to be abutted to a lower end face of the motor mounting block  214 , and the guide block  233  moves along two guide shafts  235  erected on the swinging block  230 . Rotating the motor  231  causes the guide block  233  to move up and down, by which the carriage  210  can move up and down pivoting about the carriage shaft  220 . Further, a spring (not shown) is provided between the carriage  210  and the moving arm  221 , so as to constantly urge the carriage  210  downward, thus to press the lens LE against the grindstone  251 .  
         [0083]     A lens shape measuring unit  300  is placed behind the carriage  210 .  FIG. 4  is a schematic block diagram of the lens shape measuring unit  300  (detecting mechanism of a lens edge position). An arm  305  with a gauge head  303  for the rear face of the lens LE is attached to the right end of a shaft  301 . An arm  309  with a gauge head  307  for the front face of the lens LE is attached to a central portion of the shaft  301 . The tips of the gauge head  303  and the gauge head  307  are opposing each other. An axial line connecting the tip of the gauge head  303  and the tip of the gauge head  307  is parallel to axial lines of the lens rotating shafts  211 L and  211 R. The shaft  301  is movable along an axial direction of the lens rotating shafts  211 L and  211 R (axial direction of the shaft  301 ) together with a slide base  310 .  
         [0084]     The slide base  310  is provided with a rack  330  extending in a left and right direction, so that left and right movement of the slide base  310  is detected by an encoder  331  having a pinion being engaged with the rack  330 . Behind the slide base  310 , a driving plate  311  of a bent shape is pivotally attached around a shaft  312 , and a driving plate  313  of an inverse bent shape is pivotally attached around a shaft  314 . A spring  315  is provided between the driving plates  311  and  313  so as to urge the driving plates toward each other. A stopper pin  317  is provided between the end faces  311   a  and  313   a  of the driving plates  311  and  313 . When an external force is not applied to the slide base  310 , the end faces  311   a  and  313   a  of the driving plates  311  and  313  are both in contact with the stopper pin  317 , and such a state constitutes the initial position of the left and right movement. A guide pin  319  is fixed to the slide base  310 , so as to contact with the end faces  311   a  and  313   a  of the driving plates  311  and  313 . When a force toward the right in  FIG. 4  is applied to the slide base  310 , the guide pin  319  pushes the end face  313   a  to the right, while the slide base  310  is urged by the spring  315  in a direction of the initial position. On the contrary, when a force toward the left in  FIG. 4  is applied to the slide base  310 , the guide pin  319  pushes the end face  311   a  to the left, while the slide base  310  is likewise urged by the spring  315  in a direction of the initial position. Based on such movement of the slide base  310 , the encoder  331  detects a travel of the gauge head  303  contacting the rear face of the lens LE and a travel of the gauge head  307  contacting the front face of the lens LE. In addition, the shaft  301  is axially rotated by a motor (not shown), so as to move the gauge heads  303  and  307  from a non-operating position to a measuring position, which is the state shown in  FIG. 4 .  
         [0085]     When measuring the lens shape, the lens LE is moved to the left in  FIG. 4 , so that the front face of the lens LE contacts the gauge head  307 . The gauge head  307  is constantly urged toward the front face of the lens LE by the spring  315 . Under such a state, the carriage  210  is moved up and down according to the radius vector information while the lens LE is being rotated, by which a position of an edge of the front face of the lens LE is detected by the encoder  331 . In the same manner, bringing the gauge head  303  into contact with the rear face of the lens LE and moving the carriage  210  up and down according to the radius vector information while the lens LE is being rotated allows the encoder  331  to detect a position of an edge of the rear face of the lens LE.  
         [0086]      FIG. 5  is a block diagram showing a control system of the processing apparatus  200 . A memory  351 , a display monitor  352 , an input section  353  are connected to an arithmetic control unit  350  in addition to the motors  253 ,  215 ,  212 ,  222  and  231  and the encoder  331  of the lens shape measuring unit  300 . The order-receiving terminal  21  is connected to the arithmetic control unit  350 , so that the data transmitted from the order-issuing terminal  11  can be input thereto.  
         [0087]     An operation of the foregoing processing system will be described. At the eyeglass shop  10 , the target lens shape measuring apparatus  100  is employed to measure a target lens shape. Upon placing the eyeglass frame on the frame holder of the apparatus  100  and starting the measurement, the three-dimensional target lens shape is measured as (rn, θn, zn) (n=1, 2, . . . , N) as already stated. The arithmetic control unit  150  converts the three-dimensional target lens shape data (rn, θn, zn) into orthogonal coordinates data (xn, yn, zn).  
         [0088]     The three-dimensional target lens shape data may remain in this format, however, it is preferable to correct the two-dimensional target lens shape data as follows.  
         [0089]      FIG. 6 ,  FIG. 7A  and  FIG. 7B  are drawings for explaining a correction method of the two-dimensional target lens shape data. Referring to  FIG. 6 , “TO” designates the three-dimensional target lens shape data (xn, yn, zn) on the orthogonal coordinates system xyz, and TR designates the two-dimensional target lens shape projected on the xy plane (xn, yn). An xz component (xa, za) of a point Va corresponding to a smallest value in the x-axis, and an xz component (xb, zb) of a point Vb corresponding to a greatest value in the x-axis are selected out of the x components of the three-dimensional target lens shape data (xn, yn, zn), and an angle of a line segment connecting the points Va and Vb with respect to the x-axis is defined as αa, as shown in  FIG. 7 . The direction inclined by the angle αa is regarded as a new X-axis. Likewise, a yz component (yc, zc) of a point Vc corresponding to a smallest value in the y-axis, and a yz component (yd, zd) of a point Vd corresponding to a greatest value in the y-axis are selected out of the y components of the three-dimensional target lens shape data (xn, yn, zn), and an angle of a line segment connecting the points Vc and Vd with respect to the y-axis is defined as αb, as shown in  FIG. 7 . Then, the direction inclined by the angle αb is regarded as a new Y-axis.  
         [0090]     Further, a direction defined by a perpendicular bisector of the line segment connecting the points Va and Vb, and a perpendicular bisector of the line segment connecting the points Vc and Vd is regarded as a new Z-axis Then, the three-dimensional target lens shape data (xn, yn, zn) is converted into new three-dimensional target lens shape data (Xn, Yn, Zn) based on the new coordinate system XYZ, utilizing the angles αa and αb. Upon projecting the three-dimensional target lens shape data (Xn, Yn, Zn) onto the new XY plane, corrected two-dimensional target lens shape data (Xn, Yn) is obtained. The reference point of the XY coordinate system defined at this stage becomes the geometrical center of the two-dimensional target lens shape data (Xn, Yn) When processing the lens, the geometrical center of the target lens shape or the optical center of the lens LE is employed as the lens rotation axis. Therefore, utilizing the corrected two-dimensional target lens shape data allows minimizing a processing error that affects the warp of the rim.  
         [0091]     Calculating distances between the respective data in the three-dimensional target lens shape data (Xn, Yn, Zn) (n=1, 2, . . . , N), and summing the distances gives a circumferential length FL of the actually measured three-dimensional target lens shape. Then, a radius of a sphere in which a circumferential length of an imaginary three-dimensional target lens shape obtained by projecting the two-dimensional target lens data (Xn, Yn) onto the sphere substantially accords with the circumferential length FL is calculated. Such calculation may be performed as follows.  
         [0092]     First, four points of the three-dimensional target lens shape data (Xn, Yn, Zn) are arbitrarily selected, and a radius SR of such a sphere SP that allows the four points to be distributed on its surface is calculated. Here, the calculation is made on the assumption that the center of the sphere SP is on the Z-axis. The two-dimensional target lens shape data (Xn, Yn) is again converted into polar coordinates data, to thereby obtain two-dimensional target lens shape data (rσn, rθn). The two-dimensional target lens shape data (rσn, rθn) is projected onto the sphere SP as shown in  FIG. 8 , and the Z-coordinate rzn on the surface of the sphere SP is calculated by the formula given below. 
 
 rzn=SR −( SR   2   −rσn   2 ) 1/2 ( n= 1, 2 , . . . , N ) 
 
 This gives the imaginary three-dimensional target lens shape data (rσn, rθn, rzn) (n=1, 2, . . . , N) on the sphere SP. Summing the distances between the respective data in the imaginary three-dimensional target lens shape data (rσn, rθn, rzn) (n=1, 2, . . . , N) gives a circumferential length FLSR of the imaginary three-dimensional target lens shape on the sphere SP which has the radius SR. 
 
         [0093]     The circumferential length FLSR and the circumferential length FL are compared, thus to obtain a difference in circumferential length ΔFL (=FL−FLSR). If the circumferential length difference ΔFL is deviated from a predetermined permissible range, which is substantially 0, the imaginary three-dimensional target lens shape data (rσn, rθn, rzn) (n=1, 2, . . . , N) is recalculated based on a radius SR+α determined by appropriately increasing or decreasing the radius SR of the sphere SP, followed by recalculation of the circumferential length FLSR and thus obtaining the circumferential length difference ΔFL. Then, a radius SR of the sphere that satisfies the predetermined tolerance of the difference in circumferential length ΔFL is finally recalculated. In other words, the circumferential length FLSR calculated upon projecting the two-dimensional target lens shape onto the sphere SP having the finally obtained radius SR accurately accords with the circumferential length FL.  
         [0094]     The two-dimensional target lens shape data (rσn, rθn) converted to the polar coordinates data, the finally obtained radius SR of the sphere SP by the circumferential length calculation, FPD and so on are transmitted from the measuring apparatus  100  to the order-issuing terminal  11 . Here, the radius SR is customarily converted to a frame curvature Crv (523 divided by the radius SR in millimeter) for practical use. The radius SR, or the frame curvature Crv corresponds to the circumferential length-related data generated by associating the circumferential length FL with data of a different format. Data such as a pupil distance PD, material of the lens LE and the rim to be used for layout may be input to the measuring apparatus  100 , so that such data can be simultaneously transmitted to the order-issuing terminal  11 . The order issuing terminal  11  receives the input of data necessary for ordering the lens, such as degree prescription, in addition to the processing data transmitted by the measuring apparatus  100 , and outputs all such data to the lens processing workshop  20 .  
         [0095]     The data that has been output is transmitted to the lens processing workshop  20  via the server  30  of the communications network NW, thus to be received by the order-receiving terminal  21 . The processing data is sequentially output from the order-receiving terminal  21  to the processing apparatus  200 .  
         [0096]     A processing operation of the processing apparatus  200  will be described hereunder. After outputting the processing data received by the order-receiving terminal  21  to the processing apparatus  200 , the lens LE is held by the lens rotating shafts  211 L and  211 R and the processing apparatus  200  is activated. The arithmetic control unit  350  first performs the measurement of the lens shape based on the two-dimensional target lens shape data (rσn, rθn) Once the front face shape and the rear face shape of the lens LE have been measured, calculation of the bevel path is performed based on the obtained edge position information, and the two-dimensional target lens shape data and the radius SR of the sphere SP transmitted from the eyeglass shop (if the frame curvature Crv has been transmitted, the radius SR is worked out from the frame curvature).  
         [0097]     The calculation of the bevel path will be explained. First, the three-dimensional target lens circumferential length is restored, based on the two-dimensional target lens shape data (rσn, rθn) and the radius SR. The same concept as  FIG. 8  referred to earlier is employed here, i.e. the two-dimensional target lens shape data (rσn, rθn) is again projected onto the sphere SP having the radius SR, so as to restore the three-dimensional target lens shape data. More specifically, the Z coordinate rzn on the sphere SP on which the two-dimensional target lens shape data (rσn, rθn) is projected is calculated by the formula of: 
 
 rzn=SR −( SR   2   −rσn   2 ) 1/2 ( n= 1, 2, . . . ,  N ) 
 
 thus to restore the three-dimensional target lens shape data (rσn, rθn, rzn) (n=1, 2, . . . , N) on the sphere SP. Then, summing the distances between the respective data in the restored three-dimensional target lens shape data (rσn, rθn, rzn) restores the circumferential length FLSR. This value substantially accords with the circumferential length FL obtained by the measuring apparatus  100 . 
 
         [0098]     To calculate a peak point of the bevel path, a method of tracking the front face of the lens LE based on the edge position information, a method of dividing the edge thickness by a predetermined ratio (for example, 3:7), a method of matching with the curve of the rim, and so on are known. For example, in the case of dividing the edge thickness by a predetermined ratio, the positional data on the bevel peak point in a Z direction can be obtained as (rθn, yzn) (n=1, 2, . . . , N) by relating the bevel peak point to the radius vector angle rθn of the two-dimensional target lens shape data, and based on the front and rear face edge positions and the division ratio of the edge thickness. From the result, the bevel path data (rσn, rθn, yzn) (n=1, 2, . . . , N) can be obtained, therefore calculating and summing the distances between the respective data gives an approximate circumferential length YL of the bevel path. Then, the bevel path is calculated based on the corrected circumferential length YL, such that the circumferential length YL of the bevel path substantially accords with the restored circumferential length FLSR (i.e. satisfies a predetermined tolerance). In this apparatus, the correction of the bevel path for making the circumferential length YL of the bevel path substantially accord with the circumferential length FLSR is performed by converting into the processing data of the lens LE in the radius vector direction.  
         [0099]     The processing data in the radius vector direction is handled as the data which varies the axis-to-axis distance L between the axial lines of the lens rotating shafts  211 L and  211 R and the grindstone rotating shaft  250  according to a movement of the carriage  210 . The two-dimensional target lens shape data (rσn, rθn) is substituted in the following formula so as to obtain a maximum value of L. Here, R represents the radius of the grindstone  25 .  
               L   =       r   ⁢           ⁢   δ   ⁢           ⁢     n   ·   cos     ⁢           ⁢   r   ⁢           ⁢   θ   ⁢           ⁢   n     +         R   2     -       (     r   ⁢           ⁢   δ   ⁢           ⁢     n   ·   sin     ⁢           ⁢   r   ⁢           ⁢   θ   ⁢           ⁢   n     )     2             ⁢           ⁢     
     ⁢           ⁢     (       n   =   1     ,   2   ,   3   ,   …   ⁢           ,   N     )             Formula   ⁢           ⁢   1             
 
         [0100]     Then, (rσn, rθn) is rotated about the processing center by an arbitrary minute unit angle, and a maximum value of L in this state is calculated. Such a rotating angle is defined as ζi (i=1, 2, . . . , N) for executing the same calculation over an entire circumference, and maximum value of L at each ζi is defined as Li, and the corresponding rθn as Θi. The obtained (Li, ζi, Θi) (i=1, 2, . . . , N) is used as the processing data associated with the distance  
         [0101]     Then, a size correction amount Δ1 is obtained by: 
 
Δ1=( YL−FLSR )/2π
 
 based on the circumferential length YL of the bevel path and the restored circumferential length FLSR. Then, a value Lai corrected from Li by Δ1 at every rotational angle ζi is obtained by: 
 
 Lai=Li−Δ 1( i= 1, 2, . . . , N) 
 
 based on which the corrected beveling information (Lai, ζi, Zi) (i=1, 2, . . . , N) can be calculated. Here, Zi is obtained by converting the yzn of the bevel path data (rθn, yzn) to the relation with ζi. 
 
         [0102]     Once the processing data has been calculated, the processing is executed by the grindstone  251 . The arithmetic control unit  350  drives the motor  222  so as to move the carriage  210  such that the lens LE is located on the grindstone  251   a  or the grindstone  251   b , and thus moves the carriage  210  up and down while driving the motor  215  to rotate the lens LE (changing the distance L between axial lines of the lens rotating shaft  211 L and  211 R and the grindstone rotating shaft  250 ) based on the processing data of the roughing (rough processing). By this process, the lens LE is shaped into the two-dimensional target lens shape.  
         [0103]     Then, the lens LE is moved to the beveling groove of the grindstone  251   c . In the beveling finish process, the position of the lens LE is controlled by the motor  215  based on the ζi of the beveling information (Lai, ζi, Zi) (i=1, 2, . . . , N) ; the motor  231  is controlled based on Lai; and the motor  222  is controlled based on Zi. As a result, the bevel path having the circumferential length that substantially accords with the actual circumferential length of the rim can be accurately formed around the periphery edge surface of the lens LE.  
         [0104]     Although the present invention has been described based on the foregoing embodiment, the present invention is not limited to this embodiment. For example, the calculation of the restored circumferential length FLSR based on the two-dimensional target lens shape and the frame curvature (or the radius SR of the sphere) may be performed by another computer (such as the order-receiving terminal  21 ), instead of the arithmetic control unit  350  of the processing apparatus  200 .  
         [0105]     Further, the calculation of the bevel path having the circumferential length that substantially accords with the circumferential length FLSR, performed based the restored circumferential length FLSR, may be alternatively performed through calculating a ratio (FLSR/YL) between the restored circumferential length FLSR and the circumferential length YL of the bevel path obtained based on the edge position, and correcting the bevel path data (rσn, rθn, yzn) (n=1, 2, . . . , N) based on the obtained ratio.  
         [0106]     Further, as a method of associating the circumferential length FL with data of a different format, the frame curvature or the sphere radius SR which is the base thereof is employed in the foregoing embodiment, however, the following method maybe adopted. For example, instead of correcting the radius SR, the two-dimensional target lens shape data is corrected. In other words, the radius SSR of a sphere in which arbitrary four points of the three-dimensional target lens shape data (XSn, Yn, Zn) of the rim are on the sphere is calculated. Then, a ratio ks between the circumferential length FLSSR and the circumferential length FL is obtained with respect to the three-dimensional target lens shape data corresponding to the state that the two-dimensional target lens shape data (rσn, rθn) (n=1, 2, . . . , N) is projected onto the sphere having the radius SSR, and the two-dimensional target lens shape data (rσn, rθn) is corrected based on the ratio ks. The corrected two-dimensional target lens shape data (ksrσn, rθn) (n=1, 2, . . . , N), and the radius SSR or the frame curvature Crvs to be obtained based thereon are employed as the output data (the frame curvature does not have to be strictly accurate, and, for example, radius data of a circle that passes through three points on an upper portion of the rim may simply be employed). On the side of the processing apparatus  200 , the three-dimensional target lens shape data can be restored by projecting the corrected two-dimensional target lens shape data (ksrσn, rθn) (n=1, 2, . . . , N) onto the sphere having the radius SSR or a radius calculated from the frame curvature. The circumferential length calculated at this stage corresponds to the restored three-dimensional target lens circumferential length FLSR which substantially accords with the circumferential length FL. The subsequent steps are similar to the foregoing embodiment, i.e. the size correction amount Δ1 is calculated based on the circumferential length YL and the restored circumferential length FLSR, and the beveling information (Lai, ζi, Zi) (i=1, 2, . . . , N) corresponding to the corrected bevel path is calculated, and beveling processing is performed based on the result.  
         [0107]     Alternatively, instead of associating the calculation of the restored circumferential length FLSR with the two-dimensional target lens shape data and the spherical radius SR or the frame curvature, the two-dimensional target lens shape data (ksrσn, rθn) (n=1, 2, . . . , N) may be corrected into the two-dimensional target lens shape data (Rσn, Rθn) such that the circumferential length of the two-dimensional target lens shape data (rσn, rθn) (n=1, 2, . . . , N) substantially accords with the circumferential length FL, and such corrected data may be output from the measuring apparatus  100 . On the side of the processing apparatus  200 , the circumferential length of the two-dimensional target lens shape data (Rσn, Rθn) (n=1, 2, . . . , N) is calculated, and the obtained value is converted to the restored circumferential length FLSR. The subsequent steps are similar to the foregoing embodiment, i.e. the size correction amount Δ1 is calculated based on the circumferential length YL and the restored circumferential length FLSR, and the beveling information (Lai, ζi, Zi) (i=1, 2, . . . , N) corresponding to the corrected bevel path is calculated, which allows performing accurate processing. The processing apparatus  200  may calculate the two-dimensional circumferential length along with the two-dimensional target lens shape data (Rσn, Rθn) (n=1, 2, . . . , N), and output such data.  
         [0108]     Still further, the circumferential length F 2 L of the two-dimensional target lens shape data (rσn, rθn) (n=1, 2, . . . , N) may be calculated, and a circumferential length correction coefficient K 1  of the ratio of the circumferential length FL with respect to such circumferential length F 2 L may be calculated, to thereby output the two-dimensional target lens shape data (rσn, rθn) and the circumferential length correction coefficient K 1  on the side of the processing apparatus  200 , the circumferential length FLSR can be restored based on the circumferential length F 2 L of the received two-dimensional target lens shape data (rσn, rθn) and the circumferential length correction coefficient K 1 .