Abstract:
An eyeglass lens is designed to permit the operator to preset by himself the conditions for bevel formation in AUTO mode so that he can perform efficient lens processing. The eyeglass lens grinding apparatus includes frame data inputting section for entering configuration data on an eyeglass frame, layout data inputting section for entering layout data to be used in providing a layout of an eyeglass lens to be processed which corresponds to the eyeglass frame, edge position detecting section for determining data on the edge position of the processed lens on the basis of the frame configuration data and the layout data. The lens grinding apparatus further includes an arithmetic control circuit, a parameter input section, and a sequence program stored in a main program memory. The sequence program allows a user to input or alter the parameters—even when the lens grinding apparatus operates in an auto-processing mode—used to calculate bevel processing data. Allowing a user to input or alter parameters, even in an auto-processing mode, enhances the utility of the lens grinding apparatus. Further, even after the bevel processing data has been calculated on the basis of a user input or altered parameter, the user can, in a forced-processing mode, further alter a portion of the bevel processing data calculated using an altered parameter in the auto-processing mode.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an eyeglass lens grinding apparatus for grinding the periphery of lenses to fit into an eyeglass frame. 
     An eyeglass lens grinding apparatus is known and it grinds the periphery of lenses to form a bevel at which each lens is supported in the groove of the eyeglass frame so as to achieve good fit into the latter. 
     In lens processing with this type of grinding apparatus, it is important to determine the best bevel position with respect to the edge position of a lens which has been processed into conformity with the configuration of an eyeglass frame. This is largely dependent on the experience and special hunch of the operator and great skill has been required to form satisfactory bevels. To deal with this problem, the edge position predestined by lens processing is measured and after the bevel position that divides the edge at a preset ratio is automatically determined on the basis of the obtained information, processing is subsequently carried out in accordance with the thus obtained information on the bevel position. An apparatus capable of this automated (AUTO) processing is already in commercial use. 
     However, the bevel position to be determined in the automated processing is entirely up to the manufacturer of the processing apparatus and the bevel formed is not necessarily in compliance with the specifications required by the processor (who has presented the eyeglasses). To accommodate this situation, the apparatus described above is adapted to be such that the processing mode is shifted to FORCED mode and the bevel position can be altered by supplying the apparatus with the necessary information. However, it is cumbersome to adjust the bevel position in each processing cycle. 
     In addition, the thickness of the rim of the eyeglass frame is generally different depending upon whether its constituent material is metallic or plastic and, it often becomes necessary to alter the bevel position in accordance with the constituent material of the frame. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under these circumstances and has as an object providing an eyeglass lens grinding apparatus which enables the processor to preset by himself the conditions of bevel formation in automated processing such as to permit for efficient lens processing. 
     Another object of the invention is to provide an eyeglass lens grinding apparatus which is capable of bevel formation as appropriate for the constituent material of the eyeglass frame into which the lens is to be fitted. 
     The stated objects of the invention can be attained by the following. 
     (1) An eyeglass lens grinding apparatus for grinding the periphery of a lens to fit into an eyeglass frame, comprising: 
     frame data inputting means for entering configuration data on said eyeglass frame; 
     layout data inputting means for entering layout data to be used in providing a layout of the lens corresponding to said eyeglass frame; 
     edge position detecting means for determining data on the edge position of the processed lens on the basis of said frame configuration data and said layout data; 
     bevel data calculating means which possesses calculation formula having at least one parameter and which calculators bevel data; 
     standard value storage means for storing a standard value of said parameter; 
     parameter altering means for altering the parameter from its standard value; and 
     control means for automatically bevelling the lens on the basis of the bevel data calculated using the altered parameter. 
     (2) The eyeglass lens grinding apparatus recited in (1), wherein said parameter comprises either the ratio of dividing the edge thickness of the processed lens or the amount of offset or both. 
     (3) The eyeglass lens grinding apparatus recited in (2), which further includes frame material designating means and wherein said ratio or amount of offset varies with the constituent material of the eyeglass frame. 
     (4) The eyeglass lens grinding apparatus recited in (3), wherein the constituent material of the eyeglass frame is either metallic or plastic. 
     (5) The eyeglass lens grinding apparatus recited in (1), wherein said parameter is the ratio of dividing the edge thickness of the processed lens and the calculation formula possessed by said bevel data calculating means has the power of the lens as a variable. 
     (6) The eyeglass lens grinding apparatus recited in (1), which further includes curve calculating means for calculating the front and rear surface curves of the lens on the basis of the result of detection by said edge position detecting means, said parameter is the ratio of dividing the edge thickness of the processed lens and the calculating formula possessed by said bevel data calculating means has a variable based on the difference between the front and rear surface curves of the lens. 
     (7) An eyeglass lens grinding apparatus for grinding the periphery of a lens to fit into an eyeglass frame, comprising: 
     frame data inputting means for entering configuration data on said eyeglass frame; 
     layout data inputting means for entering layout data to be used in providing a layout of the lens corresponding to said eyeglass frame; 
     edge position detecting means for determining data on the edge position of a processed lens on the basis of the said frame configuration data and said layout data; 
     bevel data calculating means which possessed a calculating formula having at least one parameter and which calculates bevel data; 
     standard value storage means for storing a standard value of said parameter; 
     parameter altering means for altering the parameter from its standard value; 
     forced processing data inputting means for further altering the bevel data calculated using the altered parameter; and 
     control means for bevelling the lens on the basis of second bevel data altered on the basis of the data entered by said forced processing data inputting means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
     FIG. 1 is a perspective view showing the general layout of the eyeglass lens grinding machine of the invention; 
     FIG. 2 is a cross-sectional view of a carriage; 
     FIG. 3 is a diagram showing a carriage drive mechanism, as viewed in the direction of arrow A in FIG. 1; 
     FIG. 4 is a perspective view of the functional part of an eyeglass frame and template configuration measuring section; 
     FIG. 5 is a sectional view of a lens configuration measuring section; 
     FIG. 6 is a plan view of the lens configuration measuring section; 
     FIG. 7 is a diagram showing the outer appearance of a display section and an input section; 
     FIG. 8 is a diagram showing the essential part of a block diagram of the electronic control system for the eyeglass lens grinding machine of the invention; and 
     FIG. 9 is a diagram showing an exemplary image for “CHANGE BEVEL PARAMETERS”. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view showing the general layout of the eyeglass lens grinding machine of the invention. The reference numeral  1  designates a machine base, on which the components of the machine are arranged. The numeral  2  designates an eyeglass frame and template configuration measuring section, which is incorporated in the upper section of the grinding machine to obtain three-dimensional configuration data on the geometries of the eyeglass frame and the template. Arranged in front of the measuring section  2  are a display section  3  which displays the results of measurements, arithmetic operations, etc. in the form of either characters or graphics, and an input section  4  for entering data or feeding commands to the machine. Provided in the front section of the machine is a lens configuration measuring section  5  for measuring the geometry (edge thickness) of the lens to be processed. 
     The reference numeral  6  designates a lens grinding section, where an abrasive wheel group  60  made up of a rough abrasive wheel  60   a  for use on glass lenses, a rough abrasive wheel  60   b  for use on plastic lenses and a finishing abrasive wheel  60   c  for tapered edge (bevel) and plane processing operations is mounted on rotating shaft  61   a  through a spindle unit  61  fixed to the machine base  1 . Shown by  65  is an AC motor for rotating the abrasive wheels and its rotation is transmitted to the abrasive wheel group  60  via a pulley  63  attached to the rotational shaft  61   a , a belt  64  and a pulley  66 . Shown by  7  is a carriage section and  700  is a carriage. 
     (Layout of the Major Components) 
     The layout of the major components of the grinding apparatus will now be described. 
     (A) Carriage section 
     The construction of the carriage section will now be described with reference to FIGS. 1 to  3 . FIG. 2 is a cross-sectional view of the carriage, and FIG. 3 is a diagram showing a drive mechanism for the carriage, as viewed in the direction of arrow A in FIG.  1 . 
     A shaft  701  is secured on the base  1  and a carriage shaft  702  is rotatably and slidably supported on the shaft  701 ; the carriage  700  is pivotally supported on the carriage shaft  702 . Lens rotating shafts  704   a  and  704   b  are coaxially and rotatably supported on the carriage  700 , extending parallel to the shaft  701 . The lens rotating shaft  704   b  is rotatably supported in a rack  705 , which is movable in the axial direction by means of a pinion  707  fixed on the rotational shaft of a motor  706 ; as a result, the lens rotating shaft  704   b  is moved axially such that it is opened or closed with respect to the other lens rotating shaft  704   a , thereby holding the lens LE in position. 
     A drive plate  716  is securely fixed at the left end of the carriage  700  and a rotational shaft  717  is rotatably provided on the drive plate  716 , extending parallel to the shaft  701 . A pulse motor  721  is secured to the drive plate  716  by means of a block  722  and the rotation of the pulse motor  721  is transmitted to the shaft  702  via a gear  720  provided at the right end of the rotational shaft  717 , a pulley  718  provided at the left end of the rotational shaft  717 , a timing belt  719  and a-pulley  703   a . The rotation of the shaft  702  in turn is transmitted to the lens rotating shafts  704   a  and  704   b  via timing belts  709   a  and  709   b , pulleys  703   b ,  703   c ,  708   a  and  708   b , whereupon the lens rotating shafts  704   a  and  704   b  are rotated in synchronism. 
     An intermediate plate  710  is rotatably secured at the left end of the carriage  700 . The intermediate plate  710  has a rack  713  which meshes with a pinion  715  attached to the rotational shaft of a carriage moving motor  714 . Rotating pinion  715  will cause the carriage  700  to move along the axis of the shaft  701 . 
     The carriage  700  is allowed to pivot by a pulse motor  728 , which is secured to a block  722  in such a way that a round rack  725  meshes with a pinion  730  secured to the rotational shaft  729  of the pulse motor  728 . The round rack  725  extends parallel to the shortest line segment connecting the axis of the rotational shaft  717  and that of the shaft  723  secured to the intermediate plate  710 ; in addition, the round rack  725  is held to be slidable with a certain degree of freedom between a correction block  724  which is rotatably fixed on the shaft  723  and the block  722 . A stopper  726  is fixed on the round rack  725  so that it is capable of sliding only downward from the position of contact with the correction block  724 . With this arrangement, the axis-to-axis distance r′ between the rotational shaft  717  and the shaft  723  can be controlled in accordance with the rotation of the pulse motor  728  and it is also possible to control the axis-to-axis distance r between the abrasive wheel rotating shaft  61   a  and each of the lens rotating shafts  704   a  and  704   b  since r has a linear correlationship with r′. 
     The layout of the carriage section is basically the same as what is described in commonly assigned U.S. Pat. No. 5,347,762, to which reference should be made for further details. 
     (B) Eyeglass Frame and Template Configuration Measuring Section 
     FIG. 4 is a perspective view of the functional part  2   a  of the eyeglass frame and template configuration measuring section  2 . The functional part  2   a  comprises a moving base  21  which is movable in a horizontal direction, a rotating base  22  which is rotatably and axially supported on the moving base  21  and which is rotated by a pulse motor  30 , a moving block  37  which is movable along two rails  36   a  and  36   b  supported on retainer plates  35   a  and  35   b  provided vertically on the rotating base  22 , a gage head shaft  23  which is passed through the moving block  37  in such a way that it is capable of both rotation and vertical movements, a gage head  24  attached to the top end of the gage head shaft  23  such that its distal end is located on the central axis of the shaft  23 , an arm  41  which is rotatably attached to the bottom end of the shaft  23  and is fixed to a pin  42  which extends from the moving block  37  vertically, a light shielding plate  25  which is attached to the distal end of the arm  41  and which has a vertical slit  26  and a 45° inclined slit  27  formed therein, a combination of a light-emitting diode  28  and a linear image sensor  29  which are attached to the rotating base  22  to interpose the light shielding plate  25  therebetween, and a constant-torque spring  43  which is attached to a drum  44  rotationally and axially supported on the rotating base  22  and which normally pulls the moving block  37  toward the distal end of the head gage  24 . 
     The moving block  37  also has a mounting hole  51  through which a measuring pin  50  is to be inserted for measurement of the template. 
     The functional part  2   a  having the construction just described above measures the configuration of the eyeglass frame in the following manner. First, the eyeglass frame is fixed in a frame holding portion (not shown but see, for example, U.S. Pat. No. 5,347,762) and the distal end of the gage head  24  is brought into contact with the bottom of the groove formed in the inner surface of the eyeglass frame. Subsequently, the pulse motor  30  is allowed to rotate in response to a predetermined unit number of rotation pulses. As a result, the gage head shaft  23  which is integral with the gage head  24  moves along the rails  36   a  and  36   b  in accordance with the radius vector of the frame and also moves vertically in accordance with the curved profiles of the frame. In response to these movements of the gage head shaft  23 , the light shielding plate  25  moves both vertically and horizontally between the LED  28  and the linear image sensor  29  such as to block the light from the LED  28 . The light passing through the slits  26  and  27  in the light shielding plate  25  reaches the light-receiving part of the linear image sensor  29  and the amount of movement of the light shielding plate  25  is read. Briefly, the position of slit  26  is read as the radius vector r of the eyeglass frame and the positional difference between the slits  26  and  27  is read as the height information z of the same frame. By performing this measurement at N points, the configuration of the eyeglass frame is analyzed as (rn, θn, zn) (n=1, 2, . . . , N). The eyeglass frame and template configuration measuring section  2  under consideration is basically the same as what is described in commonly assigned U.S. Pat. No. 5,138,770, to which reference should be made. 
     For measuring a template, the template is fixed on a template holding portion (see, for example, U.S. Pat. No. 5,347,762) and, the measuring pin  50  is fitted in the mounting hole  51 . As in the case of measurement of the eyeglass frame configuration, the pin  50  will move along the rails  36   a  and  36   b  in accordance with the radius vector of the template and, hence, the position of slit  26  detected by the linear image sensor  29  is measured as information radius vector. 
     (C) Lens Configuration Measuring Section 
     FIG. 5 is a sectional view of the lens configuration measuring section  5  and FIG. 6 is a plan view of the same. The basic components of the lens configuration measuring section  5  are a measurement arm  527  having two feelers  523  and  524 , a rotating mechanism comprising a DC motor  503  for rotating the measurement arm  527 , a pulley  513 , a belt  514 , a pulley  507 , a shaft  501  and a pulley  508  and so forth, as well as a detection mechanism comprising a sensor plate  510  and photoswitches  504  and  505  which detect the rotation of the measurement arm  527  to control the rotation of the DC motor  503 , a potentiometer  506  which detects the amount of rotation of the measurement arm  527  to provide data on the geometries of the front and rear surfaces of the lens, and so forth. The layout of the lens configuration measuring section  5  is basically the same as what is descried in commonly assigned Unexamined Published Japanese Patent Application No. Hei 3-20603 and so forth, to which reference should be made for further details. 
     In the process of measuring the lens profile (edge thickness), the lens to be processed is revolved with the feeler  523  contacting the front refractive surface of the lens, whereby the potentiometer  506  detects the amount of rotation of the pulley  508  to provide data on the geometry of the front refractive surface of the lens; thereafter, the feeler  524  is brought into contact with the rear refractive surface of the lens and the same procedure is repeated to provide data on the geometry of the rear refractive surface of the lens. 
     (D) Display Section and Input Section 
     FIG. 7 is a diagram showing the outer appearance of the display section  3  and the input section  4 . The display section  3  is formed of a liquid-crystal display and, under the control of a main arithmetic control circuit to be described later, it displays various images such as a parameter setting image, a layout image on which layout information can be entered and an image that simulates the bevel position relative to the lens geometry and the state of bevel cross section. 
     The input section  4  includes various setting switches such as a switch  402  for designating the constituent material of the lens to be processed, a switch  403  for designating the constituent material (metallic or plastic) of the frame, a mode switch  404  for selecting the mode of lens processing [whether it is automated bevel processing, forced bevel processing, plane processing or plane-specular processing (polishing)], a R/L switch  405  for determining whether the lens to be processed is for use on the right eye or the left eye, a switch  407  for changing the image to be displayed on the display section  3  (between a layout image, a menu image and a parameter setting image), a MOVE switch  408  for selecting an appropriate input item by moving the cursor or arrow that are displayed on the display section  3 , a “+” switch  409   a  and “−” switch  409   b  for entering numerical data, a switch  410  for use on such occasions as the change of the format in which the layout data are to be entered, a START/STOP switch  411  for starting or stopping the lens processing operation, a switch  413  for opening or closing the lens chucks, a tracing switch  416  for giving directions on the lens frame or template tracing, a next-data switch  417  for transferring the data from the tracing operation, and so forth. 
     (E) Electronic Control System for the Machine 
     FIG. 8 shows the essential part of a block diagram of the electronic control system for the eyeglass lens grinding machine of the invention. A main arithmetic control circuit  100  which is typically formed of a microprocessor and controlled by a sequence program stored in a main program memory  101 . The main arithmetic control circuit  100  can exchange data with IC cards, eye examination devices and so forth via a serial communication port  102 . The main arithmetic control circuit  100  also performs data exchange and communication with a tracer arithmetic control circuit  200  of the eyeglass frame and template configuration measurement section  2 . Data on the eyeglass frame configuration are stored in a data memory  103 . 
     The display section  3 , the input section  4 , a sound reproducing device  104  and the lens configuration measuring section  5  are connected to the main arithmetic control circuit  100 . The measured data of lens which have been obtained by arithmetic operations in the main arithmetic control circuit  100  are stored in the data memory  103 . The carriage moving motor  714 , as well as the pulse motors  728  and  721  are connected to the main operation arithmetic circuit  100  via a pulse motor driver  110  and a pulse generator  111 . The pulse generator  111  receives commands from the main operation arithmetic circuit  100  and determines how many pulses are to be supplied at what frequency in Hz to the respective pulse motors to control their operation. 
     The operation of the eyeglass lens grinding machine having the above-described construction will now be explained. 
     There are two modes of forming a bevel on the edge of a lens; one is an auto-processing mode in which bevel calculations are performed by computing formulae based on preliminarily machine-loaded parameters so as to accomplish automatic bevelling, and the other is a forced processing mode in which each time lens-processing is effected, the operator changes the bevelling data used in the auto-processing mode and performs the processing of the lens. On the pages that follow, processing in an auto mode is mainly described. 
     Before starting lens processing in an auto mode, the operator may himself set parameters on the shape of a bevel to be formed on the edge of the lens to be processed. The procedure of the setting operation is as follows. Manipulate the image change switch  407  to have a menu appear on the display  3  and then select the item “ADJUST BEVEL POSITION”, whereupon an image for “CHANGE BEVEL PARAMETERS” appears on the display section  3  (see FIG.  9 ). Four items are available to change bevel parameters and two of them apply to the case where the! eyeglass frame of interest is metallic and the other two apply to the case where it is plastic. The items available for the first case are- item  351  for entering the desired ratio by which the edge thickness along the entire periphery of the lens is to be divided in a specified layout for the position of the bevel&#39;s apex and item  352  for entering the amount of an offset by which the position of the bevel&#39;s apex, given the desired ratio of division, is translated towards either the front or rear surface of the lens. The items available for the second case are item  353  for entering the desired ratio of dividing the edge thickness of the lens as in the first case and item  354  for entering the amount of offset of the position of the bevel&#39;s apex. To select a particular item, the operator manipulates the MOVE switch  408  such that an arrow mark  350  on the left margin of the image is moved up and down. If a particular item is selected, relevant data are entered by adjusting the numerals appearing to the right of the respective CHANGE items (as indicated by  361 - 364 ) through the manipulation of switches  409   a  and  409   b . Before adjustment, stored standard values are displayed for the respective items. 
     The ratio to be selected from items  351  and  353  is 0% if the position of the bevel&#39;s apex coincides with the front surface of the lens and 100% if it coincides with the rear surface of the lens. Hence, a ratio of 30% means that the position of the bevel&#39;s apex is determined such that the ratio of the front side of the edge thickness to the rear side is 3:7. Speaking of the amount of offset to be selected from items  352  and  354 , entry of “+2.0 mm” means that the position of the bevel&#39;s apex given a specified ratio of division is translated 2.0 mm towards the rear surface of the lens. 
     Different settings of the layout of bevel position can be selected depending upon whether the constituent material of the eyeglass frame is metallic or plastic. Hence, even in processing in AUTO mode, an appropriate bevel position can be set in accordance with the constituent material of which the eyeglass frame is made. Generally speaking, metallic frames have thin rims whereas plastic frames have thick rims; therefore, in order to ensure good aesthetic appeal when lenses are fitted in an eyeglass frame, the position of the bevel&#39;s apex may be set closer to the front surface of each lens if the frame is metallic or it may be set towards the center if the frame is plastic. This can be accomplished by adjusting the amount of offset. 
     When the necessary changes have been entered, the CHANGE switch  410  is manipulated to return the displayed image to a menu, whereupon the standard values in the program for bevel calculations are rewritten and stored. 
     We then describe the actual processing operation. In the first place, an eyeglass frame (or a template therefor) is set on the eyeglass frame and template configuration measuring section  2  and the tracing switch  416  is touched to start tracing. The radius vector information on the eyeglass frame as obtained by the functional part  2   a  is stored in a trace data memory  202 . when the next data switch  417  is touched, the data obtained by tracing is transferred into the machine and stored in the data memory  103 . At the same time, graphics in the form of a frame is presented on the screen of the display section  3  on the basis of the eyeglass frame data, rendering the machine ready for the entry of processing conditions. 
     In the next step, the operator who is looking at the screen of the display section  3  operates on the input section  4  to enter layout data such as the PD, the FPD and the height of the optical center. The apparatus is supplied with new radius vector information (r s δ n , r s θ n ) based on the radius vector information for the eyeglass frame and the entered layout data. 
     Subsequently, the operator determines what the lens to be processed and the frame are made of and as to whether the lens is for use on the right or left eye and enters the necessary data. In addition, the operator touches the MODE switch  404  to select the AUTO processing mode. After entering the processing conditions, the lens to be processed is subjected to specified preliminary operations (e.g., centering of the suction cup) and chucked between the lens rotating shafts  704   a  and  704   b . Then, the START/STOP switch  411  is touched to activate the machine. 
     In response to the entry of a start signal, the machine performs arithmetic operations to effect processing correction (the correction of the radius of each abrasive wheel) on the basis of the entered data so as to yield information for the processing correction (see, for example, U.S. Pat. No. 5,347,762). Subsequently, the lens configuration measuring section  5  is activated to measure the lens configuration, thereby yielding edge position information (lZ n , rZ n ) for the bevel&#39;s apex or shoulder for both the front and rear surfaces of the lens in association with the radius vector information. On the basis of both the edge position information and the aforementioned conditions for bevel forming ratio which are dependent on the constituent material of the eyeglass frame (metallic or plastic) as designated by manipulation of the switch  403 , the position of the bevel&#39;s apex yZ n  is determined by the following equation: 
     
       
         lZ n +(rZ n −lZ n )R/100=yZ n    
       
     
     where R is the ratio of dividing the edge thickness which is entered as a bevel parameter. If the amount of offset is also an input item, it is added so as to determine the position of the bevel&#39;s apex in association with the radius vector information and the thus determined position is used as bevel data. Another way to calculate the position of the bevel&#39;s apex is such that the curves of the front and rear surfaces of the lens are determined from the information on the edge position and if the curve of the front surface is within a certain range, the position of the bevel&#39;s apex is shifted from the edge position of the front surface by a certain amount towards the rear surface and a bevel curve which is the same as the curve of the front surface of the lens is established (see, for example, U.S. Pat. No. 5,347,762). 
     In the AUTO processing mode, rough grinding is started in response to the entry of a START signal. The machine moves the chucked lens to the rough abrasive wheel specified in accordance with the designated constituent material of the lens to be processed and subsequently the machine controls the drive of the associated motors based on the information for processing correction such as to perform the processing of the lens. During this rough grinding operation, bevel sections based on the bevel data determined by bevel calculations are automatically displayed in succession on the display section  3  to cover the entire periphery of the lens and this helps the operator check for the correctness of the bevelling operation. 
     After the end of the rough grinding operation, the process then goes to the finishing operation. The machine disengages the lens from the rough abrasive wheel, replaces it into the bevel processing groove on the finishing abrasive wheel  60   c  and controls the drive of the associated motors based on the bevelling information so as to form the desired bevel. 
     As described above, the operator, even if he is performing AUTO processing, can set the layout for the position of the bevel&#39;s apex in advance and, hence, is capable of forming a bevel that complies with the specifications he desires. In addition, the bevel forming operation can be set specifically in accordance with the constituent material of the eyeglass frame and, hence, automated processing can be performed by means of materials designation, in a manner that is appropriate to the designated material. 
     In a forced processing mode, bevel data calculated with altered parameters are displayed on the display section  3  (for bevel simulation) and switches in the input section  4  are manipulated to make further changes in the displayed bevel data, thereby ensuring efficient formation of a bevel that complies with the specifications the operator desires. 
     The foregoing description assumes that bevel formation is performed on the basis of a preset desired ratio of dividing the edge thickness. In practice, however, the edge thickness of the lens to be processed varies with its power, so the ratio of dividing the edge thickness may be adapted to be variable in accordance with the lens power which is either entered as input data or calculated by mathematical operations (the lens power is determined by the refractive index of the lens material and the curves of its front and rear surfaces but, alternatively, it may be based on the curves of the front and rear surfaces of the lens as determined from the information on the edge position). The ratio of dividing the edge thickness may be varied linearly over a specified range of lens power or it may be varied stepwise; if desired, the two ways of variation may be combined. With an eyeglass lens of a positive power having a steep curve on the front surface, the ratio is preferably set at about 50% because the bevel curve can be rendered gentle enough to provide a good fit into the eyeglass frame. When setting bevel parameters for performing the above-described method of bevel formation in AUTO processing mode, particularly good convenience is achieved by entering the point of variation and designating the ratios before and after the variation. 
     It is also within the scope of the invention to vary the amount of offset in accordance with a minimum edge thickness that is derived from the lens power and the information on the edge position. The setting of bevel parameters may be such that the operator has various options to choose that comprise preset parametric combinations. 
     As described on the foregoing pages, the apparatus of the invention enables the operator to set the conditions for bevel formation easily even in the AUTO mode and, hence, a bevel that complies with the specification the operator desires can be formed efficiently. 
     In addition, different bevels can be formed in accordance with what constituent material the eyeglass frame is made of and this allows for efficient formation of a bevel that provides good aesthetic appeal when the processed lenses and fitted into the eyeglass frame.