Abstract:
An eyeglass lens processing apparatus for processing a periphery of an eyeglass lens, includes: a lens rotating unit having rotating shafts for holding and rotating the lens; an abrasive wheel; an abrasive wheel state detecting unit for detecting a lowered processing performance of the abrasive wheel; and a notifying unit for notifying that dressing for the abrasive wheel is required based on a result of detection by the abrasive wheel state detecting unit.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to an eyeglass lens processing apparatus for processing a periphery of an eyeglass lens.  
           [0002]    An eyeglass lens processing apparatus for processing a periphery of an eyeglass lens comprises a circular abrasive wheel (grindstone) having a diamond layer formed of a fine diamond particle and metal powder and serves to carry out processing by causing the periphery of the lens to come in contact with the rotating abrasive wheel by pressure.  
           [0003]    In such processing using the abrasive wheel, if a large number of lenses are processed, the diamond particle slips off or is worn away or clogged so that the processing performance of the abrasive wheel is deteriorated and a time required for processing the lens is increased. In such a case, generally, dressing is carried out through a dressing bar in order to arrange the diamond layer.  
           [0004]    However, it is difficult for an operator to carry out the dressing in a proper timing. More specifically, there is a problem in that it is hard for the operator to decide whether or not the processing time is increased and when the dressing is to be carried out.  
         SUMMARY OF THE INVENTION  
         [0005]    In consideration of the drawbacks of the conventional apparatus, it is a technological object of the invention to provide an eyeglass lens processing apparatus capable of easily managing a time that the dressing is to be carried out over an abrasive wheel.  
           [0006]    In order to attain the object, the invention has the following structure.  
           [0007]    (1) An eyeglass lens processing apparatus for processing a periphery of an eyeglass lens, comprising:  
           [0008]    lens rotating means having rotating shafts for holding and rotating the lens;  
           [0009]    an abrasive wheel;  
           [0010]    abrasive wheel state detecting means for detecting a lowered processing performance of the abrasive wheel; and  
           [0011]    notifying means for notifying that dressing for the abrasive wheel is required based on a result of detection by the abrasive wheel state detecting means.  
           [0012]    (2) The eyeglass lens processing apparatus according to (1), further comprising:  
           [0013]    processing state detecting means for detecting a state of processing for the lens; and  
           [0014]    wherein the abrasive wheel state detecting means detects the lowered processing performance of the abrasive wheel based on a result of comparison between the detected state of processing and a predetermined reference.  
           [0015]    (3) The eyeglass lens processing apparatus according to (2), wherein:  
           [0016]    the processing state detecting means detects a processing time from a start of processing; and  
           [0017]    the abrasive wheel state detecting means detects the lowered processing performance of the abrasive wheel in case that the detected processing time exceeds a predetermined reference processing time.  
           [0018]    (4) The eyeglass lens processing apparatus according to (2), wherein:  
           [0019]    the processing state detecting means detects an end of processing over the entire periphery of the lens or at a predetermined rotation angle of the lens; and  
           [0020]    the abrasive wheel state detecting means detects the lowered processing performance of the abrasive wheel in case that the end of processing is not detected within a predetermined reference processing time.  
           [0021]    (5) The eyeglass lens processing apparatus according to (2), wherein:  
           [0022]    the processing state detecting means detects a number of lens rotation from a start of processing; and  
           [0023]    the abrasive wheel state detecting means detects the lowered processing performance of the abrasive wheel in case that the detected number of lens rotation exceeds a predetermined reference number of lens rotation.  
           [0024]    (6) The eyeglass lens processing apparatus according to (2), wherein:  
           [0025]    the processing state detecting means detects an end of processing over the entire periphery of the lens or at a predetermined rotation angle of the lens; and  
           [0026]    the abrasive wheel state detecting means detects the lowered processing performance of the abrasive wheel in case that the end of processing is not detected within a predetermined reference number of lens rotation.  
           [0027]    (7) The eyeglass lens processing apparatus according to (2), wherein:  
           [0028]    the processing state detecting means detects an amount of processing at a predetermined rotation angle of the lens; and  
           [0029]    the abrasive wheel state detecting means detects the lowered processing performance of the abrasive wheel in case that the amount of processing detected within a predetermined processing time or a predetermined number of lens rotation does not meet a predetermined reference amount of processing.  
           [0030]    (8) The eyeglass lens processing apparatus according to (2), further comprising:  
           [0031]    changing means for changing a value of the reference.  
           [0032]    (9) The eyeglass lens processing apparatus according to (8), further comprising:  
           [0033]    lens thickness input means for inputting a thickness of the lens; and  
           [0034]    wherein the changing means changes the reference value based on the inputted lens thickness.  
           [0035]    (10) The eyeglass lens processing apparatus according to (2), further comprising:  
           [0036]    lens material input means for inputting a material of the lens to be processed; and  
           [0037]    wherein the processing state detecting means detects the state of processing for the lens only in case that a glass is inputted as the material.  
           [0038]    (11) The eyeglass lens processing apparatus according to (2), wherein:  
           [0039]    the processing state detecting means detects the states of processing for a plurality of lenses; and  
           [0040]    the abrasive wheel state detecting means detects the lowered processing performance of the abrasive wheel based on a result of comparison between an average of the detected states of processing and the predetermined reference.  
           [0041]    (12) The eyeglass lens processing apparatus according to (1), further comprising:  
           [0042]    processing control means for controlling processing for the lens based on a result of detection by the abrasive wheel state detecting means.  
           [0043]    (13) The eyeglass lens processing apparatus according to (12), further comprising:  
           [0044]    processing state detecting means for detecting a state of processing for the lens;  
           [0045]    wherein the abrasive wheel state detecting means detects the lowered processing performance of the abrasive wheel based on a result of comparison between the detected state of processing and predetermined first and second references; and  
           [0046]    wherein the processing control means stops the processing for the lens based on a result of comparison by the abrasive wheel state detecting means using either one of the first and second references.  
           [0047]    (14) The eyeglass lens processing apparatus according to (1), wherein:  
           [0048]    the abrasive wheel includes a rough processing abrasive wheel and finish processing abrasive wheel; and  
           [0049]    the notifying means gives a notification regarding the rough processing abrasive wheel and a notification regarding the finish processing abrasive wheel independently of each other.  
           [0050]    (15) An eyeglass lens processing apparatus for processing a periphery of an eyeglass lens, comprising:  
           [0051]    an abrasive wheel;  
           [0052]    counting means for counting a number of lenses which have been processed; and  
           [0053]    notifying means for notifying that dressing for the abrasive wheel is required in case that the counted number of lenses exceed a predetermined reference number.  
           [0054]    (16) The eyeglass lens processing apparatus according to (15), further comprising:  
           [0055]    lens material input means for inputting a material of the lens to be processed; and  
           [0056]    wherein the counting means only counts the number of the processed lenses, each being inputted as a glass by the input means.  
           [0057]    The present disclosure relates to the subject matter contained in Japanese patent application No. 2001-433 (filed on Jan. 15, 2001), which is expressly incorporated herein by reference in its entirety. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0058]    [0058]FIG. 1 is a view showing a structure of the appearance of an eyeglass lens processing apparatus according to the invention;  
         [0059]    [0059]FIG. 2 is a perspective view showing a schematic structure of a processing section provided in a housing of an apparatus body;  
         [0060]    [0060]FIG. 3 is a view showing a schematic structure of a main part of a carriage section;  
         [0061]    [0061]FIG. 4 is a view showing the carriage section seen in a direction of E in FIG. 2;  
         [0062]    [0062]FIG. 5 is a block diagram showing a control system of the apparatus;  
         [0063]    [0063]FIG. 6 is a flow chart for explaining an operation for detecting a deterioration in the processing performance of each abrasive wheel;  
         [0064]    [0064]FIG. 7 is a flow chart for explaining an operation for temporarily interrupting the processing;  
         [0065]    [0065]FIG. 8 is a diagram showing an example of a screen obtained when each reference time for message display and processing stop are to be changed; and  
         [0066]    [0066]FIG. 9 is a view illustrating another embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0067]    Hereafter, a description will be given of an embodiment of the invention. FIG. 1 is a diagram illustrating the external configuration of an eyeglass-lens processing apparatus in accordance with the invention. An eyeglass-frame-shape measuring device  2  is incorporated in an upper right-hand rear portion of a main body  1  of the apparatus. As the frame-shape measuring device  2 , ones that disclosed in U.S. Pat. Nos. 5,228,242, 5,333,412, U.S. Pat. No. 5,347,762 (Re. 35,898) and so on, the assignee of which is the same as the present application, can be used. A switch panel section  410  having switches for operating the frame-shape measuring device  2  and a display  415  for displaying processing information and the like are disposed in front of the frame-shape measuring device  2 . Further, reference numeral  420  denotes a switch panel section having various switches for inputting processing conditions and the like and for giving instructions for processing, and numeral  402  denotes an openable window for a processing chamber.  
         [0068]    [0068]FIG. 2 is a perspective view illustrating the arrangement of a lens processing section disposed in the casing of the main body  1 . A carriage section  700  is mounted on a base  10 , and a subject lens LE clamped by a pair of lens rotation shafts (lens chuck shafts)  702 L and  702 R of a carriage  701  is ground by a group of abrasive wheels  602  attached to an abrasive wheel rotating shaft  601 . The group of abrasive wheels  602  include a rough abrasive wheel  602   a  for plastic lenses, a rough abrasive wheel  602   b  for glass lenses, and a finishing abrasive wheel  602   c  for beveling processing and flat processing. The rotating shaft  601  is rotatably attached to the base  10  by a spindle  603 . A pulley  604  is attached to an end of the rotating shaft  601 , and is linked through a belt  605  to a pulley  607  which is attached to a rotating shaft of an abrasive-wheel rotating motor  606 . A lens-shape measuring section  500  is provided in the rear of the carriage  701 . As the lens-shape measuring section  500 , not only one that is disclosed by Japanese patent publication No. 2000-317796, but also other conventional devices can be used.  
         [0069]    Referring to FIGS. 2, 3, and  4 , a description will be given of the construction of the carriage section  700 . FIG. 3 is a schematic diagram of essential portions of the carriage section  700 , and FIG. 4 is a view, taken from the direction of arrow E in FIG. 2, of the carriage section  700 .  
         [0070]    The carriage  701  is capable of rotating the lens LE while chucking it with two shafts  702 L and  702 R, and is rotatably slidable with respect to a carriage shaft  703  that is fixed to the base  10  and that extends in parallel to the shaft  601 . Hereafter, a description will be given of a lens chuck mechanism and a lens rotating mechanism as well as an X-axis moving mechanism and a Y-axis moving mechanism of the carriage  701  by assuming that the direction in which the carriage  701  is moved in parallel to the abrasive-wheel rotating shaft  601  is the X axis, and the direction for changing the axis-to-axis distance between the shafts ( 702 L,  702 R) and the shaft  601  by the rotation of the carriage  701  is the Y axis.  
         [0071]    &lt;Lens Chuck Mechanism and Lens Rotating Mechanism&gt; 
         [0072]    The shaft  702 L and the shaft  702 R are rotatably held coaxially by a left arm  701 L and a right arm  701 R, respectively, of the carriage  701 . A chucking motor  710  is fixed to the center of the upper surface of the right arm  701 R, and the rotation of a pulley  711  attached to a rotating shaft of the motor  710  rotates a feed screw  713 , which is rotatably held inside the right arm  701 R, by means of a belt  712 . A feed nut  714  is moved in the axial direction by the rotation of the feed screw  713 . As a result, the shaft  702 R connected to the nut  714  can be moved in the axial direction, so that the lens LE is clamped by the shafts  702 L and  702 R.  
         [0073]    A rotatable block  720  for attaching a motor, which is rotatable about the axis of the shaft  702 L, is attached to a left-side end portion of the left arm  701 L, and the chuck shaft  702 L is passed through the block  720 , a gear  721  being secured to the left end of the shaft  702 L. A pulse motor  722  for lens rotation is fixed to the block  720 , and as the motor  722  rotates the gear  721  through a gear  724 , the rotation of the motor  720  is transmitted to the shaft  702 L. A pulley  726  is attached to the shaft  702 L inside the left arm  701 L. The pulley  726  is linked by means of a timing belt  731   a  to a pulley  703   a  secured to a left end of a rotating shaft  728 , which is held rotatably in the rear of the carriage  701 . Further, a pulley  703   b  secured to a right end of the shaft  728  is linked by means of a timing belt  731   b  to a pulley  733  which is attached to the shaft  702 R in such a manner as to be slidable in the axial direction of the shaft  702 R inside the right arm  701 R. By virtue of this arrangement, the shaft  702 L and the shaft  702 R are rotated synchronously.  
         [0074]    &lt;X-axis Moving Mechanism and Y-axis Moving Mechanism of Carriage&gt; 
         [0075]    The shaft  703  is provided with a movable arm  740  which is slidable in its axial direction so that the arm  740  is movable in the X-axis direction (in the axial direction of the shaft  703 ) together with the carriage  701 . Further, the arm  740  at its front portion is slidable on and along a guide shaft  741  that is secured to the base  10  in a parallel positional relation to the shaft  703 . A rack  743  extending in parallel to the shaft  703  is attached to a rear portion of the arm  740 , and this rack  743  meshes with a pinion  746  attached to a rotating shaft of a motor  745  for moving the carriage in the X-axis direction, the motor  745  being secured to the base  10 . By virtue of the above-described arrangement, the motor  745  is able to move the carriage  701  together with the arm  740  in the axial direction (in the X-axis direction).  
         [0076]    As shown in FIG. 3( b ), a swingable block  750  is attached to the arm  740  in such a manner as to be rotatable about the axis La which is in alignment with the rotational center of the shaft  601 . The distance from the center of the shaft  703  to the axis La and the distance from the center of the shaft  703  to the rotational center of the shaft ( 702 L,  702 R) are set to be identical. A Y-axis moving motor  751  is attached to the block  750 , and the rotation of the motor  751  is transmitted by means of a pulley  752  and a belt  753  to a female screw  755  held rotatably in the block  750 . A feed screw  756  is inserted in a threaded portion of the screw  755  in mesh therewith, and the screw  756  is moved vertically by the rotation of the screw  755 .  
         [0077]    A guide block  760  which abuts against a lower end surface of the block  720  is fixed to an upper end of the screw  756 , and the block  760  moves along two guide shafts  758   a  and  758   b  implanted on the block  750 . Accordingly, as the block  760  is vertically moved together with the screw  756  by the rotation of the motor  751 , it is possible to change the vertical position of the block  720  abutting against the block  760 . As a result, the vertical position of the carriage  701  attached to the block  720  can be also changed (namely, the carriage  701  rotates about the shaft  703  to change the axis-to-axis distance between the shafts ( 702 L,  702 R) and the shaft  601 ). A spring  762  is stretched between the left arm  701 L and the arm  740 , so that the carriage  701  is constantly urged downward to impart processing pressure onto the lens LE. Although the downward urging force acts on the carriage  701 , the downward movement of the carriage  701  is restricted such that the carriage  701  can only be lowered down to the position in which the block  720  abuts against the block  760 . A sensor  764  for detecting an end of processing is attached to the block  720 , and the sensor  764  detects the end of processing at each radius vector angle of the lens LE (each rotation angle) by detecting the position of a sensor plate  765  attached to the block  760 .  
         [0078]    The operation of the apparatus described above will be explained with reference to a block diagram showing a control system in FIG. 5. First of all, the whole processing operation of the apparatus will be described. Herein it is assumed that a glass lens is processed.  
         [0079]    The shape of an eyeglass frame (or a template) for fitting is measured by the frame shape measuring device  2 , and data thus obtained by the measurement are input to a data memory  161  by pressing a switch  421 . By operating each switch of a switch panel section  420 , an operator inputs necessary layout data such as the PD of a wearer and the height of an optical center, the material of the lens and a processing mode. The material of the lens is specified with a switch  426 . If the necessary input is completed, the lens LE is chucked and processed through the shaft  702 L and the shaft  702 R.  
         [0080]    When the apparatus is operated by pressing a start switch  423 , a control section  160  operates the lens shape measuring section  500  to measure the shapes of the front and rear surfaces of the lens. By the measurement, the thickness of a lens having a processing radius vector shape is obtained. When the shape of the lens is obtained, the control section  160  operates each data on rough processing and finishing processing for each radius vector angle in accordance with a predetermined program based on the input data. In order of the rough processing and the finishing processing, the processing is automatically executed.  
         [0081]    The control section  160  drives the motor  745  such that the lens LE comes to a portion above the rough abrasive wheel  602   b  for glass, and thus moves the carriage  701 . Based on rough processing data, then, the motor  751  is rotated to move the carriage  701  in a Y-axis direction and the lens LE is rotated by the motor  722  to carry out the rough processing. The movement of the carriage  701  in the Y-axis direction and the rotation of the lens LE are repeated until the end of the processing is detected by the sensor  764  over the whole radius vector angle of the lens LE. When the end of the processing is detected, the rough processing is completed.  
         [0082]    When the rough processing is completed, the finishing processing is successively executed automatically after the lens LE is removed from the rough abrasive wheel  602   b . In the case of finishing processing for beveling, after the lens LE is moved to a beveling groove portion of the finishing abrasive wheel  602   c , the rotation of the lens LE and the movement of the carriage  701  in the Y-axis and X-axis directions are controlled based on the finishing processing data. When the end of the processing is detected over the whole periphery of the lens LE through the sensor  764 , the finishing processing is completed.  
         [0083]    By repeating such processing, a large number of lenses are processed. In the rough abrasive wheel  602   b  and the finishing abrasive wheel  602   c , consequently, processing performance is deteriorated due to slip-off or wear of the diamond particle so that a time required for processing the lens is gradually increased. The control section  160  measures times required from the start of the rough processing and the finishing processing by means of a counting function  162  provided therein. By the result of the measurement, a deterioration in the processing performance of each abrasive wheel is detected and a notice that dressing is required is given to an operator based on the result of the detection (see a flow chart of FIG. 6).  
         [0084]    During the rough processing, when the measured time for the rough processing passes a preset reference time TR 1  (for example, 5 minutes) (when the end of the processing of the whole periphery is not detected by the sensor  764  even if the time TR 1  passes), the control section  160  causes the display  415  to display a message that the dressing is required for the rough abrasive wheel  602   b . While the display is carried out when all processing including the finishing processing is completed, it may be performed when the time TR 1  passes.  
         [0085]    Similarly, when the measured time for the finishing processing passes a preset reference time TF 1  (for example, 5 minutes) (when the end of the processing of the whole periphery is not detected by the sensor  764  even if the time TF 1  passes), in the finishing processing, a message that the dressing of the finishing abrasive wheel  602   c  is required is displayed on the display  415  after the processing is completed.  
         [0086]    In addition to the display of the message, the notice that the dressing is required may be given in a voice or an alarm by a voice generating section  165 .  
         [0087]    By the notice, the operator can precisely know a time that the dressing is required for the respective abrasive wheels. After the notice of each dressing is displayed on the display  415 , a stop switch  424  is pressed to erase the display of the message, thereby carrying out the necessary dressing.  
         [0088]    When the processing time is increased, moreover, the processing may be once interrupted to carry out the dressing and may be then restarted. FIG. 7 is a flow chart showing an operation to be carried out with such a structure. The control section  160  measures a time required from the start of the rough processing. When the measured time for the rough processing exceeds a preset reference time TR 2  (for example, 10 minutes) (when the end of the processing of the whole periphery is not detected by the sensor  764  even if the time TR 2  is reached), the carriage  701  is raised to separate the lens LE from the rough abrasive wheel  602   b  and the rotation of the lens LE and that of the abrasive wheel are stopped to interrupt the processing. At the same time, a message that the processing is interrupted and the dressing of the rough abrasive wheel  602   b  is required is displayed on the display  415 . When the processing is interrupted, the operator presses the switch  424  to erase the display of the message and sets a dress mode with a switch  425 , thereby carrying out the dressing over the rough abrasive wheel  602   b  in a predetermined procedure. Then, the switch  423  is pressed to restart the rough processing.  
         [0089]    Also in the finishing processing, similarly, the control section  160  measures the time required from the start of the finishing processing. When the measured time for the finishing processing exceeds a predetermined reference time TF 2  (for example, 10 minutes) (when the end of the processing of the whole periphery is not detected by the sensor  764  even if the time TF 2  is reached), the processing to be carried out by the finishing abrasive wheel  602   c  is once interrupted. After the finishing abrasive wheel  302   c  is subjected to the dressing, the switch  423  is pressed to restart the finishing processing.  
         [0090]    For the times TR 1  and TF 1 , suitable times are predetermined in consideration of a time required for processing a thick lens (a lens having a large processing amount) in a state in which the diamond layers of the abrasive wheels  602   b  and  602   c  are normally arranged or an increase in the processing time with an increase in the number of lenses to be processed.  
         [0091]    Moreover, while the times TR 2  and TF 2  required for deciding whether or not the processing is temporarily interrupted may be equal to the times TR 1  and TF 1  for the message display, it is advantageous that the times TR 2  and TF 2  are set to be longer than the times TR 1  and TF 1 . More specifically, in the case in which TR 2 =TR 1  and TF 2 =TF 1  are set, the processing is always interrupted temporarily if it is decided that the necessary time for the dressing arrives. Consequently, a great deal of time and labor is taken for reprocessing and a processing error is apt to be made. On the other hand, if TR 2  and TF 2  are set to be longer than TR 1  and TF 1  respectively, it is preferable that the lens should be completely processed and the dressing should be carried out before the measured times (processing times) TR 2  and TF 2  are reached. Therefore, it is possible to eliminate a great deal of time and labor of the reprocessing and a processing error caused by the reprocessing. It is effective to set the times TR 2  and TF 2  that the processing is once interrupted in that the processing time can be prevented from being excessively increased and a state in which the end of the processing is not detected can be avoided.  
         [0092]    While the reference for detecting a deterioration in the processing performance of the abrasive wheel is managed by the time in the embodiment, the number of rotations of the lens LE can also be employed. The reason is that a time required for completing the processing and the number of rotations of the lens LE are almost proportional to each other in the case in which the lens LE is to be processed by a rotation at an almost equal speed. The number of rotations of the lens LE can be known from the number of rotations of the motor  722 .  
         [0093]    In the lens processing, moreover, when the end of the processing is detected at a predetermined radius vector angle, the lens is rotated every minute angle and such an operation is repeated over the whole periphery. Thus, processing control is carried out. In this case, it is also possible to detect a deterioration in the processing performance of each abrasive wheel by a comparison of a time required for the end of the processing at an angle for the start of the processing with a preset reference time.  
         [0094]    Moreover, the detection of a deterioration in the processing performance is not always carried out every time the lens is to be processed. A time required for the end of the processing for each lens or the number of rotations of the lens may be stored in a memory and, for example, a mean value of 10 lenses which is stored may be compared with a reference value. Thus, it is possible to evaluate the deterioration in the processing performance of the abrasive wheel with an overall tendency.  
         [0095]    Moreover, it is advantageous for the operator to optionally change each reference value for deciding whether or not a notice for the promotion of the dressing is to be given and the processing is to be stopped. In the case in which the times TR 1 , TR 2 , TF 1  and TF 2  in the above example are to be changed, the following operation is carried out. First of all, a parameter setting screen for changing a dress reference such as the time TR 1  is called over the display  415  with the switch  426 . FIG. 8 shows an example of the screen obtained at that time. After a cursor  450  is set to a parameter item to be changed with switches  427   a  and  427   b  for moving the cursor  450 , a set time is changed with numeric variation switches  428   a  and  428   b . The switch  426  is pressed again to get out of the parameter setting screen. Consequently, each reference time to be managed by the control section  160  is updated.  
         [0096]    Moreover, there is a tendency in which a thick lens has a long processing time and a thin lens has a short processing time. By utilizing data on a lens thickness obtained as a result of the measurement of the lens shape measuring section  500 , therefore, it is also possible to determine a decision reference of a deterioration in processing performance. For example, the control section  160  changes a decision reference value corresponding to the data on the lens thickness such that a reference time is increased if the lens thickness is great and is reduced if the lens thickness is small.  
         [0097]    [0097]FIG. 9 is a view illustrating another embodiment. Only different portions from those of the embodiment described above are shown and the structures shown according to the embodiment described above are employed for the same functions. In FIG. 9, an encoder  770  is fixed to a block  720 ′ for motor attachment and a pinion  771  attached to a rotating shaft of the encoder  770  meshes with a rack formed on a guide shaft  758   a ′ extended in parallel with a feed screw  756 . The output of the encoder  770  is input to the control section  160  and the moving distance of elevation (Y-axis movement) of the carriage  701  is detected.  
         [0098]    Description will be given to the detection of a deterioration in the processing performance of an abrasive wheel with such a structure. In the case in which the lens LE is processed by a rotation at an almost equal speed (particularly, rough processing), the output of the encoder  770  obtained by processing the lens LE with one rotation is first stored every predetermined angle. Next, the output of the encoder  770  is obtained every equal angle when a second rotation is started. Consequently, a processing distance (a processing amount) for each angle is obtained from the first rotation to the second rotation. The processing distance (the processing amount) for each angle is compared with a predetermined reference processing distance (a reference processing amount). If the processing distance is equal to or smaller than the reference processing distance, it is decided that the processing performance is deteriorated.  
         [0099]    Moreover, in the case in which the lens LE is to be rotated and processed after the end of the processing is detected for each lens rotating angle, a processing distance within a predetermined time at an angle for the start of the processing is compared with the reference processing distance. If the progress of the processing is slow, it is decided that the processing performance is deteriorated. In the case of a variant, furthermore, it is preferable that the operator can optionally change each reference value.  
         [0100]    As another variant, furthermore, it is also possible to give a notice of a time that the dressing is required for the rough abrasive wheel  602   b  and the finishing abrasive wheel  602   c  depending on whether or not the number of processed glass lenses reaches a reference number. Based on the input of a material when setting the processing conditions, the control section  160  decides whether the material of the processed lens is glass or not. When the operator executes an operation for erasing a message display in order to carry out the dressing, the control section  160  resets a count number.  
         [0101]    As described above, the invention can be variously changed and various changes are also included in the invention within the same technical thought.  
         [0102]    As described above, according to the invention, it is possible to easily manage the dressing time of an abrasive wheel.