Patent Publication Number: US-7220162-B2

Title: Eyeglass lens processing apparatus

Description:
BACKGROUND OF THE INVENTION 
   (1) Technical Field 
   The present invention relates to an eyeglass lens processing apparatus for processing an eyeglass lens. 
   (2) Related Art 
   In an eyeglass lens processing apparatus, an eyeglass lens is held (chucked) by two lens chuck shafts and is rotated, while the peripheral edge of the lens is processed by a processing tool such as a grindstone so that the lens can have a shape substantially identical with a target lens shape (traced outline). To hold the lens, a cup serving as a fixing jig is mounted on and fixed to a front refractive surface of the lens through a double-sided adhesive tape, the cup with the lens fixed thereto is mounted on a cup receiver at a distal end of one of the two lens chuck shafts, and a lens holder at a distal end of the other lens chuck shaft is brought into contact with a rear refractive surface of the lens. Further, to hold a lens having a refractive surface easy to slip such as a lens on which a water repellant coating is enforced, a film-shaped adhesive sheet may be bonded onto the refractive surface of the lens and, after then, the cup is mounted on and fixed to the lens through a double-sided adhesive tape. 
   When processing the lens, the shape of the lens is measured (the edge position of the lens is detected) in accordance with the target lens shape. In this case, when the adhesive tape is bonded in such a manner that it is sticking out of the cup greatly, or when the adhesive sheet is bonded while creased, there is a possibility that an error can be included in the measuring result. And, when the lens is processed based on the processing data that have been obtained from the measuring results containing such error, defective processing can occur. Such defective processing can also occur similarly when some other foreign bodies stick to the refractive surface of the lens. 
   SUMMARY OF THE INVENTION 
   The technical object of the present invention is to provide an eyeglass lens processing apparatus which can detect whether foreign bodies exist on a refractive surface of an eyeglass lens or not, thereby being able to prevent the defective processing of the lens previously. 
   In order to achieve the above object, the present invention is characterized by having the following arrangements.
     (1) An eyeglass lens processing apparatus, comprising:   

   a lens holding unit that holds an eyeglass lens; 
   a data input unit that inputs target lens shape data; 
   a lens measuring unit that measures a refractive surface of the held lens based on the input target lens shape data to obtain an edge position of the lens; and 
   a controller that detects presence or absence of a foreign body on the lens refractive surface based on the obtained edge position data.
     (2) The eyeglass lens processing apparatus according to (1), wherein the controller detects the presence or absence of the foreign body based on a mutual correlation between a variation of the edge position data and a variation of the target lens shape data.   (3) The eyeglass lens processing apparatus according to (2), wherein the controller detects the presence or absence of the foreign body based on whether an inflection point of the target lens shape data is present or not in the vicinity of an inflection point of the edge position data, or on whether a sharply varying point of the target lens shape data is present or not in the vicinity of a sharply varying point of the edge position data.   (4) The eyeglass lens processing apparatus according to (1), wherein   

   the lens measuring unit measures the lens refractive surface in a first measuring path based on the target lens shape data and a second measuring path arranged a given distance inwardly or outwardly of the first measuring path to obtain the edge position data, and 
   the controller detects the presence or absence of the foreign body based on a difference between the edge position data in the first measuring path and the edge position data in the second measuring path.
     (5) The eyeglass lens processing apparatus according to (1) further comprising a lens processing unit that processes the held lens,   

   wherein the controller limits processing of the lens when the presence of the foreign body is detected. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic external view of an eyeglass lens processing apparatus according to an embodiment of the invention. 
       FIG. 2  is a schematic structure view of a lens processing portion of the eyeglass lens processing apparatus. 
       FIG. 3  is a schematic structure view of a lens shape measuring portion of the eyeglass lens processing apparatus. 
       FIG. 4  is a schematic structure view of a chamfering/grooving portion of the eyeglass lens processing apparatus. 
       FIG. 5  is a schematic block diagram of a control system of the eyeglass lens processing apparatus. 
       FIGS. 6A and 6B  are explanatory views to show how to fix a cup to the refractive surface of a lens. 
       FIG. 7  is an explanatory view of target lens shape data. 
       FIG. 8  is a flow chart to show how to detect whether a foreign body is present on the refractive surface of the lens or not. 
       FIGS. 9A and 9B  are views to show the target lens shape data and the edge position data of the front surface of the lens. 
       FIG. 10  is a view of differentiated data of the edge position data. 
       FIG. 11  is a view of differentiated data of the target lens shape data. 
       FIGS. 12A to 12C  are explanatory views of a method for detecting a foreign body from a difference between two edge positions data. 
   

   DETAILED DESCRIPTION OF PREFERED EMBODIMENTS 
   Now, an embodiment according to the invention will be described with reference to the accompanying drawings.  FIG. 1  is a schematic external view of an eyeglass lens processing apparatus  1  according to the embodiment of the invention. An eyeglass frame measuring apparatus  2  is connected to the processing apparatus  1 . As the measuring apparatus  2 , there can be used a measuring apparatus which is disclosed in, for example, U.S. Pat. No. 5,333,412 (Japanese patent publication Hei-4-93164) and U.S. Re. 35898 (Japanese patent publication Hei-5-212661). A touch panel  410  serving not only as a display portion for processing information and the like but also as an input portion for inputting processing conditions and the like, and a switch portion  420  including switches for instruction of processing such as a processing start switch are mounted on the top portion of the processing apparatus  1 . A lens to be processed is processed in a processing chamber which is formed within an opening/closing window  402 . Incidentally, the processing apparatus  1  may be formed integrally with the measuring apparatus  2 . 
     FIG. 2  is a schematic structure view of a lens processing portion disposed within the box body of the processing apparatus  1 . A carriage portion  700  which includes a carriage  701  and its moving mechanism is mounted on a main base  10 . A lens LE to be processed is held (chucked) by two lens chuck shafts  702 L and  702 R respectively rotatably held on the carriage  701 , is rotated, and is ground or processed by a grindstone  602 . The grindstone  602  according to the present embodiment includes a rough processing grindstone  602   a  for glass, a rough processing grindstone  602   b  for plastics, and a processing grindstone  602   c  for bevel-finishing and flat-finishing. A grindstone rotating shaft  601   a , on which the grindstone  602  is mounted, is connected to a grindstone rotating motor  601 . 
   The chuck shafts  702 L and  702 R are held on the carriage  701  in such a manner that their axes (the axis of rotation of the lens LE) are parallel to an axis of the shaft  601   a  (the axis of rotation of the grindstone  602 ). The carriage  701  can be moved not only in a direction of the axis of the shaft  601   a  (a direction of the axes of the chuck shafts  702 L and  702 R) (in the X-axis direction) but also in a direction perpendicular to the X-axis direction (in a direction where the distance between the axes of the chuck shafts  702 L and  702 R and the axis of the shaft  601   a  is varied) (in the Y-axis direction). 
   &lt;Lens Holding (Chucking) Mechanism&gt; 
   The chuck shaft  702 L is held on a left arm  701 L of the carriage  701  and the chuck shaft  702 R is held on a right arm  701 R thereof in such a manner that they can be rotated and are coaxial with each other. A cup receiver  730  is mounted on the distal end of the chuck shaft  702 L. A lens holder  731  is mounted on the distal end of the chuck shaft  702 R (see  FIG. 3 ). A lens holding (chucking) motor  710  is fixed to the right arm  701 R. The rotational movement of the motor  710  is transmitted through a pulley  711  mounted on the rotation shaft of the motor  710 , a belt  712  and a pulley  713  to a feed screw (not shown) connected to the pulley  713 ; the rotational movement of the feed screw moves a feed nut (not shown) in the axial direction thereof, the feed nut being threadedly engaged with the feed screw; and, the movement of the feed nut moves the chuck shaft  702 R in the axial direction thereof, the chuck shaft  702 R being connected with the feed nut. As a result of this, the chuck shaft  702 R is moved in a direction to approach the chuck shaft  702 L, so that the lens LE can be held (chucked) by the chuck shafts  702 L and  702 R. 
   &lt;Lens Rotating Mechanism&gt; 
   A lens rotating motor  720  fixed to the left arm  701 L. The rotational movement of the motor  720  is transmitted through a gear  721  mounted on the rotation shaft of the motor  720 , a gear  722 , a gear  723  coaxial with the gear  722 , a gear  724 , and a gear  725  mounted on the chuck shaft  702 L to the chuck shaft  702 L, so that the chuck shaft  702 L can be rotated. Further, the rotational movement of the motor  720  is transmitted to the chuck shaft  702  through a rotary shaft  728  connected to the rotation shaft of the motor  720  and gears respectively similar to the gears  721 – 725 , thereby rotating the chuck shaft  702 R. As a result of this, the chuck shafts  702 L and  702 R are rotated synchronously with each other, thereby rotating the lens LE which is held (chucked) by them. 
   &lt;X-axis Direction Moving Mechanism of Carriage  701 &gt; 
   A moving support base  740  is movably supported by two guide shafts  703  and  704  which are fixed on the base  10  to be parallel thereto and extend in the X-axis direction. Further, an X-axis direction moving motor  745  is fixed on the base  10 . The rotational movement of the motor  745  is transmitted to the support base  740  through a pinion gear (not shown) mounted on the rotation shaft of the motor  745  and a rack gear (not shown) mounted on the rear portion of the support base  740 , so that the support base  740  can be moved in the X-axis direction. As a result of this, the carriage  701  supported by two guide shafts  756  and  757  respectively fixed to the support base  740  can be moved in the X-axis direction. 
   &lt;Y-axis Direction Moving Mechanism of Carriage  701 &gt; 
   The carriage  701  is movably supported by the guide shafts  756  and  757  which are fixed to the support base  740  to be parallel thereto and extend in the Y-axis direction. Further, a Y-axis direction moving motor  750  through a plate  751  is fixed to the support base  740 . The rotational movement of the motor  750  is transmitted through a pulley  752  mounted on the rotation shaft of the motor  750  and a belt  753  to a feed screw  755  which is rotatably held on the plate  751 ; and, owing to the rotational movement of the feed screw  755 , the carriage  701  with which the feed screw  755  is threadedly engaged is moved in the Y-axis direction. 
   Lens shape measuring portions  500 F and  500 R are disposed above the carriage  701 . A chamfering/grooving portion  800  is arranged in front of the carriage  701 . 
   Now,  FIG. 3  is a schematic structure view of the lens shape measuring portion  500 F for measuring the shape of the front refractive surface of the lens LE. A fixed support base  501 F is fixed mounted on a sub-base  100  standing on the main base  10  (see  FIG. 2 ); and a slider  503 F is movably supported by a guide rail  502 F fixed to the support base  501 F and extending in the X-axis direction. A moving support base  510 F is fixed to the slider  503 F; and, a feeler arm  504 F is fixed to the support base  510 F. An L-shaped feeler hand  505 F is fixed to the distal end of the arm  504 F; and a disk-shaped feeler  506 F is fixed to the distal end of the hand  505 F. When measuring the shape of the front refractive surface of the lens LE, the feeler  506 F is brought into contact with the front refractive surface of the lens LE. 
   A rack gear  511 F is fixed to the lower portion of the support base  510 F; and a pinion gear  512 F which is mounted on the rotation shaft of an encoder  513 F fixed to the support base  501 F is engaged with the gear  511 F. Further, a motor  516 F is fixed to the support base  501 F. The rotational movement of the motor  516 F is transmitted to the gear  511 F through a gear  515 F mounted on the rotation shaft of the motor  516 F, a gear  514 F, and the gear  512 F, so that the gear  511 F, support base  510 F, arm  504 F and the like are moved in the X-axis direction. During the measuring operation, the motor  516 F is always pressing the feeler  506 F against the front refractive surface of the lens LE with a constant force. The encoder  513 F detects the moving amount of the support base  510 F or the like in the X-axial direction (the position of the feeler  506 F). In accordance with the thus detected moving amount (position) and the rotation angles of the chuck shafts  702 L and  702 R, the shape of the front refractive surface of the lens LE is measured. 
   Incidentally, the lens shape measuring portion  500 R for measuring the shape of the rear refractive surface of the lens LE is symmetrical to the lens shape measuring portion  500 F and, therefore, the description thereof is omitted here. 
   Now,  FIG. 4  is a schematic structure view of the chamfering and grooving portion  800 . A fixed support base  801 , which serves as the base of the chamfering and grooving portion  800 , is fixed to the upper surface of the base  10  (see  FIG. 2 ) and, a plate  802  is fixed to the support base  801 . A motor  805 , which is used to rotate an arm  820  and thereby move a grindstone portion  840  to its processing position or retreating position, is fixed on the plate  802 . A hold member  811  which rotatably holds an arm rotating member  810  is fixed to the plate  802 . A gear  813  is fixed to the rotating member  810  which extends leftward of the plate  802 . The rotational movement of the motor  805  is transmitted through a gear  807  mounted on the rotation shaft of the motor  805 , a gear  815  and the gear  813  to the rotating member  810 , so that the arm  820  fixed to the rotating member  810  can be rotated. 
   A grindstone rotating motor  821  is fixed to the gear  813 . The rotational movement of the motor  821  is transmitted to a grindstone rotating shaft  830  through a rotary shaft  823  connected to the rotation shaft of the motor  821  and rotatably held by the rotating member  810 , a pulley  824  mounted on the shaft  823 , a belt  835 , and a pulley  832  mounted on the shaft  830  rotatably held by a hold member  831  which is fixed to the arm  820 , so that the shaft  830  can be rotated. As a result of this, a processing grindstone  841   a  for chamfering the rear surface of the lens LE, a processing grindstone  841   b  for chambering the front surface of the lens LE and a processing grinding stone  842  for grooving which are respectively mounted on the shaft  830  can be rotated. The axis of the shaft  830  is set inclined about 8° with respect to the axes of the chuck shafts  702 L and  702 R, which makes it easy for the grindstone portion  840  to follow the curve of the lens LE. The chamfering grindstones  841   a ,  841   b  and grooving grindstone  842  are respectively set about 30 mm in outer diameter. 
   In the grooving and chamfering time, the arm  820  is rotated by the motor  805 , while the grindstone portion  840  is moved to its retreating position or processing position. The processing position of the grindstone portion  840  is a position which exists between the chuck shafts  702 L,  702 R and the shaft  601   a  and where the rotation axis of the shaft  830  is set on a plane on which the rotation axes of the two kinds of shafts are present. Owing to this, similarly to the peripheral edge processing operation by the grindstone  602 , the axis-to-axis distance between the rotation axes of the chuck shafts  702 L,  702 R and the rotation axis of the shaft  830  can be varied by the motor  751 . 
   Now, the operation of the apparatus having the above-mentioned structure will be described below with reference to a schematic block diagram of a control system shown in  FIG. 5 . 
   Firstly, the shapes of right and left rims of an eyeglass frame are measured using the measuring apparatus  2 , thereby obtaining target lens shape data thereof. In the case of a rimless frame or the like, the shape of a template or the shape of a dummy lens is measured, thereby obtaining target lens shape data thereof. The target lens shape data from the measuring apparatus  2  are input to the processing apparatus  1  by pressing down a communication key displayed on a touch panel  410  and the data are then stored in a memory  161  as target lens shape data (SRn, θn) (n=1, 2, - - - , N) (see  FIG. 7 ) each composed of a radial length SRn and a radial angle θn with the geometric center OF of the target lens shape as a reference. Incidentally, the target lens shape data may be input from an external computer or the like through communication means (not shown), or may be input through a bar code reader or the like. When the target lens shape data is input, a target lens shape figure is displayed on the screen of the touch panel  410  based on the target lens shape data. An operator may operate a touch key displayed on the touch panel  410  to input lay-out data such as FPD (distance between the geometric centers of the right and left rims), PD of a eyeglass wearer (distance between pupils-centers of the eyeglass wearer), the height of an optical center of the lens LE with respect to the geometric center OF of the target lens shape, and the like. Further, the operator may operate a touch key displayed on the touch panel  410  to thereby set (input) the material of the lens LE, the kind of the eyeglass frame, the processing mode, whether a chamfering operation is necessary or not, and the like. When these processing conditions are set once, according to a program stored in a memory  163  in advance, a processing procedure and the like are decided by a main control portion  160 . 
   Before or after the above operation, as a previous step to be executed prior to the operation in which the lens LE is held (chucked) by the chuck shafts  702 L and  702 R, as shown in  FIGS. 6A and 6B , a cup  50  is mounted on and fixed to the front refractive surface of the lens LE using a blocking device. The cup  50  is mounted on and fixed to the lens LE through a double-sided adhesive tape  51 . Further, in the case of a lens having a refractive surface easy to slip such as a lens with a water-repellent coating enforced thereon, a film-shaped adhesive sheet  52  may be firstly bonded to the front refractive surface of the lens and, after then, the cup  50  may be mounted on and fixed to the lens through the tape  51 . Incidentally, in order to make it difficult for the lens holder  731  to slip, the sheet  52  may also be bonded to the rear refractive surface of the lens. 
   After completion of the mounting and fixation of the cup  50  to the front refractive surface of the lens LE, the base portion of the cup  50  is mounted on the cup receiver  730 . Then, when the lens holding (chucking) switch of the switch portion  420  is pressed down, the chuck shaft  702 R is moved in the direction to approach the chuck shaft  702 L, the lens holder  731  is contacted with the rear refractive surface of the lens LE, and the lens LE is held (chucked) by the chuck shafts  702 L and  702 R. 
   When the processing start switch of the switch portion  420  is depressed, the main control portion  160  controls the lens shape measuring portions  500 F and  500 R in accordance with the target lens shape data input therein, thereby measuring the shape of the lens LE (detecting the edge position thereof). Incidentally, when the cup  50  is fixed to the lens LE in such a manner that the axis of the cup  50  is coincident with the optical center of the lens LE (optical center holding (chucking) mode), the target lens shape data stored in the memory  161  with the geometric center OF of the target lens shape as a reference are converted to the target lens shape data with the optical center thereof as a reference in accordance with the layout data such as the input FPD, PD and optical center height, and are used. Further, when the cup  50  is fixed to the lens LE in such a manner that the axis of the cup  50  is coincident with the geometric center (boxing center) of the target lens shape laid out for the lens LE (boxing center holding (chucking) mode), the target lens shape data with the geometric center OF of the target lens shape as a reference stored in the memory  161  can be used as they are. Now, description will be given below of the boxing center holding mode. 
   The main control portion  160  drive the motor  516  F to move the arm  504 F from its retreating position to its measuring position and, after then, in accordance with the target lens shape data, drives the motor  750  to move the carriage  701  and drives the motor  516 F to move the arm  504 F toward the lens LE (in a direction to approach the lens LE), thereby bringing the feeler  506 F into contact with the front refractive surface of the lens LE. Then, in a state where the feeler  506 F is in contact with the front refractive surface, the main control portion  160  drives the motor  750  in accordance with the target lens shape data, while driving the motor  720  to rotate the lens LE, to thereby move up and down the carriage  701 . With such rotation and movement of the lens LE, the feeler  506 F is moved in the axial direction of the chuck shafts  702 L and  702 R (in the X-axis direction) along the shape of the front refractive surface of the lens LE. The amount of this movement is detected by the encoder  513 F, so that the shape of the front refractive surface of the lens LE(SRn, θn, zfn) (n=1, 2, - - - , N) is measured. Incidentally, zfn expresses the height (thickness) of the front refractive surface of the lens LE. The shape of the rear refractive surface of the lens LE(SRn, θn, zrn) (n=1, 2, - - - , N) is measured by the lens shape measuring portion  500 R. Here, zrn expresses the height (thickness) of the rear refractive surface of the lens LE. The data of the shapes of the front and rear refractive surfaces of the lens LE are stored in the memory  161 . 
   Further, the main control portion  160  detects whether a foreign body is present or not on the refractive surface of the lens LE in accordance with the measured (detected) results of the lens shape (edge position). The foreign body on the refractive surface of the lens LE includes, for example, the tape  51  bonded in such a manner that it sticks greatly out of the cup  50  which often occurs when the lens LE is processed so as to substantially coincide with a target lens shape which has a narrow top-and-bottom width (vertical width), the sheet  52  bonded in a creased manner, or a processing waste remaining within the processing chamber. 
   Now, description will be given below of a method for detecting the foreign body on the front refractive surface of the lens LE (see a flow chart shown in  FIG. 8 ). Here,  FIG. 9A  is a graphical representation of the target lens shape data shown in  FIG. 7 , in which the horizontal axis expresses the radial angle θ and the vertical axis expresses the radial length SR.  FIG. 9B  is a graphical representation of the measured (detected) results of the front refractive surface shape (edge position) of the lens LE, in which the horizontal axis expresses the radial angle θ and the vertical axis expresses the edge position zf from the reference position (distance from the reference position to the edge). 
   Firstly, the main control portion  160  differentiates the edge position data shown in  FIG. 9B .  FIG. 10  shows the results of the differentiation of the edge position data. Then, the main control portion  160  extracts points (radial angles) having a large varying amount from the differentiated data. The reason for this is that, if there is present any foreign body such as the tape  51  on the refractive surface of the lens LE, normally, a sharp variation occurs in the edge position data. In  FIG. 10 , as the points having a large varying amount, portions ΔFθa, ΔFθb, ΔFθc, and ΔFθd which respectively exceed a given threshold value (±20) are extracted. However, when a sharp variation is found in the target lens shape data itself, in some cases, it is difficult to detect the foreign body only by means of the differentiating processing of the edge position data and the threshold value processing of the differentiated data. In view of this, preferably, variations in the edge position data may be compared with variations in the target lens shape data with respect to the same radial angle; and, in accordance with their mutual correlation, presence or absence of the foreign body is detected. In other words, since the lens refractive surface has a curve, when no foreign body is present on the lens refractive surface, the peak of the variation of the edge position data (the inflection point of the edge position data) substantially coincides with the peak of the variation of the target lens shape data (the inflection point of the radial length data). On the other hand, when a foreign body is present on the lens refractive surface, the peak of the variation of the edge position data appears even in a point where the peak of the variation of the target lens shape data is not found. 
   The peak of the variation of the edge position data can be extracted from the differentiated data. For example, the peak of the variation of the edge position data shown in  FIG. 9B  can be retrieved based on the waveform of the differentiated data shown in  FIG. 10 . In  FIG. 10 , the portion ΔFθa is firstly extracted as a point having a large variation amount of the differentiated data. Since this portion ΔFθa is a portion which has a large minus value in the differentiated data, by retrieving the increasing side of the edge position data existing leftward of this portion, a point FPa in  FIG. 9B  is extracted as the peak of the variation of the edge position data. Next, the peak of the variation of the target lens shape data in  FIG. 9A  is checked whether it is present or not in the vicinity (for example, in the range of ±6°) of the radial angle of the point FPa, and a point SRPa shown in  FIG. 9A  is extracted as the peak of the variation of the target lens shape data. Therefore, it is judged that the peak FPa of the variation of the edge position data is not caused by a foreign body. 
   Next, since the portion ΔFθb extracted as a point having a large variation amount in the differentiated data is a portion having a large plus value in the differentiated data, by retrieving the increasing side of the edge position data existing rightward of this portion, a point FPb in  FIG. 9B  is extracted as the peak of the variation of the edge position data. Next, it is checked whether the peak of the variation of the target lens shape data in  FIG. 9A  is present or not in the vicinity of the radial angle of the point FPb, and a point SRPb shown in  FIG. 9  is extracted as the peak of the variation of the target lens shape data. Therefore, it is judged that the peak FPb of the variation of the edge position data is not caused by a foreign body. 
   Then, because the portion ΔFθc extracted as a point having a large variation amount in the differentiated data is a portion having a large minus value in the differentiated data, by retrieving the increasing side of the edge position data existing leftward of this portion, then a point FPc in  FIG. 9B  is extracted as the peak of the variation of the edge position data. Next, it is checked whether the peak of the variation of the target lens shape data in  FIG. 9A  is present or not in the vicinity of the radial angle of the point FPc. Since no peak of the variation of the target lens shape data is present in the vicinity of the radial angle of the point FPc, it is judged that the peak FPc of the variation of the edge position data is caused by a foreign body. 
   If it is judged that a foreign body is present on the front and rear refractive surfaces of the lens LE, the main control portion  160  displays an error message or the like on the touch panel  410  and limits (stops) the processing operations to be executed thereafter. The operator must take out the lens LE from the chuck shafts  702 L and  702 R once, remove the foreign body existing on the refractive surfaces of the lens LE (and bond the tape  51  and sheet  52  again), make the chuck shafts  702 L and  702 R hold (chuck) the lens LE again, and resume the processing operation. Incidentally, when the processing apparatus is structured such that the existing position of the foreign body can be displayed on the touch panel  410 , it is easier for the operator to check the presence or absence of the foreign body. 
   When the foreign body detection judges that no foreign body is present, the main control portion  160  executes the peripheral edge processing operation of the lens LE. When the lens LE is a plastic lens, the main control portion  160  drives the motor  745  to move the carriage  701  in the X-axis direction and thereby set the lens LE on the grindstone  602   b ; and the main control portion  160  drives the motor  720  to rotate the lens LE and simultaneously drives the motor  750  to move the carriage  701  up and down based on the rough processing data obtained from the target lens shape data, thereby executing a rough processing operation on the lens LE. After completion of the rough processing operation, a finishing (finish operation) operation is started. When a bevel-finishing mode is specified, the main control portion  160  finds bevel-finishing data in accordance with the edge position data on the front and rear surfaces of the lens LE. And, the main control portion  160  drives the motor  745  to move the carriage  701  in the X-axis direction and thereby set the lens LE on a beveling groove formed in the grindstone  602   c . Then, in accordance with the bevel-finishing data, the main control portion  160  drives the motor  720  to rotate the lens LE and simultaneously drives the motors  745  and  750  to move the carriage  701  right and left as well as up and down, thereby carrying out a bevel-finishing operation. On the other hand, when a flat finishing and grooving mode is specified, the main control portion  160  finds flat finishing data and grooving data in accordance with the target lens shape data and the edge position data on the front and rear surfaces of the lens LE. Then, the main control portion  160  drives the motor  745  to move the carriage  701  in the X-axis direction and thereby sets the lens LE on a flat portion of the grindstone  602   c . Then, in accordance with the flat-finishing data, the main control portion  160  drives the motor  720  to rotate the lens LE and simultaneously drives the motors  745  and  750  to move the carriage  701  right and left as well as up and down, thereby executing a flat-finishing operation on the lens LE. Further, the main control portion  160  drives the motor  745  to move the carriage  701  in the X-axis direction and thereby sets the lens LE on the grindstone  842  moved to its processing position; and the main control portion  160  drives the motor  720  to rotate the lens LE and simultaneously drives the motors  745  and  750  to move the carriage  701  right and left as well as up and down in accordance with the grooving data, thereby carrying out a grooving operation on the lens LE. 
   Further, when a chamfering operation is specified, the main control portion  160 , in the above-mentioned lens shape measuring operation, detects the edge position of the lens LE in accordance with the target lens shape data and, after then, detects the edge position existing 0.5 mm inwardly or outwardly of the radial length of the target lens shape data. This two edge position detecting operations are performed respectively on the front and rear surfaces of the lens LE and, based on the results of such detecting operations, the respective inclined conditions of the front and rear surfaces are obtained. In accordance with the respective edge positions of the front and rear surfaces and the respective chamfering amounts, the main control portion  160  finds chamfering data on the front and rear surfaces of the lens LE. Then, the main control portion  160  drives the motor  745  to move the carriage  701  in the X-axis direction and thereby sets the lens LE on the grindstone  841   a  moved to its processing position; and the main control portion  160  drives the motor  720  to rotate the lens LE and simultaneously drives the motors  745  and  750  to move the carriage  701  right and left as well as up and down in accordance with the chamfering data on the lens rear surface, thereby executing a chamfering operation on the lens rear surface. Further, the main control portion  160  drives the motor  745  to move the carriage  701  in the X-axis direction and thereby sets the lens LE on the grindstone  841   b ; and the main control portion  160  drives the motor  720  to rotate the lens LE and simultaneously drives the motors  745  and  750  to move the carriage  701  right and left as well as up and down based on the chamfering data on the lens front surface, thereby carrying out a chamfering operation on the lens front surface. 
   Incidentally, the above-mentioned foreign body detecting method can be changed in other various manners. For example, as a foreign body detecting method based on the mutual correlation between the variations of the edge position data and the variations of the target lens shape data, there can also be employed the following method. Here,  FIG. 11  shows the results of differentiation of the target lens shape data shown in  FIG. 9A . The differentiated data of the target lens shape data is compared with the differentiated data of the edge position data shown in  FIG. 10 . With respect to the portions ΔFθa, ΔFθb, ΔFθc, and ΔFθd which are respectively extracted as points having a large variation amount in  FIG. 10 , when the differentiated data of the target lens shape data shown in  FIG. 11  are compared with the differentiated data of the edge position data, Δ SRθa which is the peak of the variation in  FIG. 11  exists in the vicinity of the radial angle of ΔFθa which is the peak of the variation shown in  FIG. 10 ; and, Δ SRθb which is the peak of the variation in  FIG. 11  is exists in the vicinity of the radial angle of ΔFθb which is the peak of the variation shown in  FIG. 10 . However, no peak of the variation in  FIG. 11  exists in the vicinity of the respective radial angles of the portions ΔFθc and ΔFθd which are respectively the peaks of the variation in  FIG. 10 . Therefore, it can be judged that the peaks ΔFθc and ΔFθd of the variation of the edge position data are caused by the presence of a foreign body. Thus, the foreign body detection can also be realized in such a manner that, by using the differentiated results of the edge position data and target lens shape data, it is checked whether the sharply varying points of the target lens shape data is present or not in the vicinity of the sharply varying points of the edge position data. 
   Further, there can also be employed another method for detecting a foreign body which, as in the case where the above-mentioned chamfering operation is specified, uses the results obtained when two edge position detecting operations are respectively performed on the front and rear surfaces of the lens LE. When a foreign body such as the tape  51  is present on the lens refractive surface, normally, the end of the foreign body rarely coincides with the lens meridian direction (the same radial angle in the edge position detection). For this reason, the edge positions are detected twice on measuring paths shifted by a given distance at the same radial angle from each other and, it is judged whether there exists a portion having a large varying amount or not in accordance with a difference between the detected edge positions. This makes it possible to detect the presence or absence of a foreign body. When no foreign body is present, the varying amount of the difference with respect to the radial angle is small. On the other hand, when any foreign body is present, a portion having a large varying amount in the difference with respect to the radial angle appears. 
   Now, description will be given here of an example of this detecting method. Here,  FIG. 12A  is a graphical representation of the results of edge position detection made twice on the front surface of the lens LE. In  FIG. 12A , FL 0 , similarly in  FIG. 9A , expresses measurement results obtained in a first measuring path of the target lens shape data, while FL 1  expresses measurement results obtained in the second measuring path existing 0.5 mm inwardly of the first measuring path.  FIG. 12B  is a graphical representation of the difference data between FL 0  and FL 1 .  FIG. 12C  is a graphical representation of results obtained by differentiating the difference data. Incidentally, in the differentiating process in  FIG. 12C , in order to facilitate the understanding of a sharply varying tendency, the detection results of the edge positions in 1000 points are calculated by averaging them by 10 points. 
   In  FIG. 12A , there is shown an example of the lens front surface in which a foreign body is present between two points FPc and FPd on FL 0 . Using the differentiating processing in  FIG. 12C , it is checked whether there exists or not a point varying sharply exceeding a given threshold value; and, the presence or absence of a foreign body is detected depending on the presence or absence of such point. In this example, since there are present points Δ FDa, Δ FDb, Δ FDc, and Δ FDd which respectively exceed the threshold value ±5, it is judged that a foreign body is present in these points. By the way, in the differentiating process in  FIG. 12C , the threshold value, which is used to detect the presence or absence of the foreign body, may be determined experimentally. 
   As described above, the presence or absence of a foreign body on the refractive surface of a lens can be detected before the lens is processed, thereby being able to prevent the defective processing of the lens.