METHOD FOR CONTROLLING EYEGLASS LENS PROCESSING DEVICE USING HALL SENSOR

Abstract

A method for controlling an eyeglass lens processing device includes: polishing the lens, and measuring a separation distance between a movable block and a carriage using a Hall sensor detection unit, in an n.sup.th rotation direction of what is obtained by equally dividing an angle of 360 degrees covered by one rotation of the lens rotation axis into m (S100); determining whether the separation distance in the n.sup.th rotation is less than a predetermined separation distance upper limit (S200); determining whether the separation distance in the n.sup.th rotation is greater than or equal to a predetermined separation distance lower limit (S300) if the separation distance in the n.sup.th rotation is less than the predetermined separation distance upper limit in S200; and rotating the lens to an n+1.sup.th rotation position (S400) if the separation distance in the n.sup.th rotation is greater than or equal to the predetermined separation distance lower limit in S300.

Claims

1. A method for controlling an eyeglass lens processing device for processing a lens while controlling a rotational speed of a lens rotation axis, the method for controlling an eyeglass lens processing device using a Hall sensor, comprising: (a) polishing the lens, and measuring a separation distance (dn) between a movable block (22) and a carriage (12) using a Hall sensor detection unit (30), in an n.sup.th rotation direction of what is obtained by equally dividing an angle of 360 degrees covered by one rotation of the lens rotation axis into m, wherein a position of the movable block (22) represents a target polishing position of the lens in the n.sup.th rotation direction, a position of the carriage (12) represents a polishing position of the lens in the n.sup.th rotation direction, and the separation distance (dn) between the movable block (22) and the carriage (12) represents a difference between the target polishing position of the lens and the polishing position of the lens (S100); (b) determining whether the separation distance (dn) in the n.sup.th rotation is less than a predetermined separation distance upper limit (dx_high) (S200); (c) determining whether the separation distance (dn) in the n.sup.th rotation is greater than or equal to a predetermined separation distance lower limit (dx_low) (S300) if the separation distance (dn) in the n.sup.th rotation is less than the predetermined separation distance upper limit (dx_high) in said step S200; and (d) rotating the lens to an n+1.sup.th rotation position (S400) if the separation distance (dn) in the n.sup.th rotation is greater than or equal to the predetermined separation distance lower limit (dx_low) in said step S300.

2. The method for controlling an eyeglass lens processing device using a Hall sensor of claim 1, further comprising: determining whether (a separation distance (dn−1) in an n−1.sup.th rotation)/(a separation distance (dn−2) in an n−2.sup.th rotation) is greater than or equal to (the separation distance (dn) in the n.sup.th rotation)/(the separation distance (dn−1) in the n−1.sup.th rotation) (S210) if the separation distance (dn) in the n.sup.th rotation is greater than or equal to the predetermined separation distance upper limit (dx_high) in said step S200; rapidly increasing the rotational speed of the lens rotation axis (S220) if (the separation distance (dn−1) in the n−1.sup.th rotation)/(the separation distance (dn−2) in the n−2.sup.th rotation) is greater than or equal to (the separation distance (dn) in the n.sup.th rotation)/(the separation distance (dn−1) in the n−1.sup.th rotation) in said step S210, and slowly increasing the rotational speed of the lens rotation axis (S225) if (the separation distance (dn−1) in the n−1.sup.th rotation)/(the separation distance (dn−2) in the n−2.sup.th rotation) is less than (the separation distance (dn) in the n.sup.th rotation)/(the separation distance (dn−1) in the n−1.sup.th rotation) in said step S210; and rotating the lens to the n+1.sup.th rotation position (S400).

3. The method for controlling an eyeglass lens processing device using a Hall sensor of claim 1, further comprising: determining whether (a separation distance (dn−1) in an n−1.sup.th rotation)/(a separation distance (dn−2) in an n−2.sup.th rotation) is less than (the separation distance (dn) in the n.sup.th rotation)/(the separation distance (dn−1) in the n−1.sup.th rotation) (S310) if the separation distance (dn) in the n.sup.th rotation is less than the predetermined separation distance lower limit (dx_low) in said step S300; rapidly decreasing the rotational speed of the lens rotation axis (S320) if (the separation distance (dn−1) in the n−1.sup.th rotation)/(the separation distance (dn−2) in the n−2.sup.th rotation) is less than (the separation distance (dn) in the n.sup.th rotation)/(the separation distance (dn−1) in the n−1.sup.th rotation) in said step S310, and slowly decreasing the rotational speed of the lens rotation axis (S325) if (the separation distance (dn−1) in the n−1.sup.th rotation)/(the separation distance (dn−2) in the n−2.sup.th rotation) is greater than or equal to (the separation distance (dn) in the n.sup.th rotation)/(the separation distance (dn−1) in the n−1.sup.th rotation) in said step S310; and rotating the lens to the n+1.sup.th rotation position (S400).

4. The method for controlling an eyeglass lens processing device using a Hall sensor of claim 1, wherein the eyeglass lens processing device comprises: lens-clamping shafts (10) configured to be rotated by a driving means (18) and to clamp the lens in a detachable manner, and having centers of their cross-section located on an extension line of the lens rotation axis; the movable block (22) in which a polishing wheel (20) for polishing the lens clamped and rotated by the lens-clamping shafts (10) is installed on a polishing wheel mount, and whose position changes according to a desired polishing depth of the lens; the carriage (12) configured to move the lens clamped and rotated by the lens-clamping shafts (10) to cause it to be in contact with the polishing wheel (20), and to come into contact with the movable block (22) when the lens in contact with the polishing wheel (20) is polished to the desired polishing depth; and the Hall sensor detection unit (30) in which a magnet (32) for detecting whether the movable block (22) and the carriage (12) are in contact and a Hall sensor (34) for detecting a strength of a magnetic field generated by the magnet (32) are mounted, respectively, on one of the carriage (12) or the movable blocks (22).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a perspective view showing the structure of an eyeglass lens processing device;

[0016] FIGS. 2 and 3 are diagrams showing a method of detecting a positional relationship between a carriage 12 on which a lens is mounted and a movable block 22 installed in a polishing wheel mount in the eyeglass lens processing device;

[0017] FIG. 4 is a flow diagram showing a method of changing a lens rotation speed in the eyeglass lens processing device shown in FIG. 1;

[0018] FIG. 5 is a graph showing a change in the value of a Hall sensor according to a distance in the eyeglass lens processing device shown in FIG. 3; and

[0019] FIG. 6 is a flow diagram showing a method of changing a lens rotation speed using a Hall sensor in a method for controlling an eyeglass lens processing device in accordance with the present invention.

DETAILED DESCRIPTION

[0020] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In the drawings attached, the same reference numerals are assigned to elements that perform the same or similar functions as conventional elements.

[0021] FIG. 3 is a diagram showing the structure of an eyeglass lens processing device provided with a Hall sensor that may be used in the present invention. As shown in FIG. 3, the eyeglass lens processing device that may be used in the present invention includes a movable block 22 installed in a polishing wheel mount; a carriage 12; and a Hall sensor detection unit 30 including a magnet 32 and a Hall sensor 34. The movable block 22 is installed in the polishing wheel mount (i.e., a frame of the eyeglass lens processing device) on which a polishing wheel 20 (see FIG. 1) for polishing a lens is mounted, and is a typical movable block whose position (height) is adjusted according to a desired polishing depth (hereinafter, “target depth”) of the lens (see Patent Documents 1 and 2). For example, if the desired polishing depth of the lens is long, in other words, if the shape of the desired eyeglass lens is small and a greater depth needs to be polished from the outer periphery of the blank lens, the movable block 22 is located relatively lower. On the contrary, if the desired polishing depth of the lens is short, in other words, if the shape of the desired eyeglass lens is large and only a short depth needs to be polished from the outer periphery of the blank lens, the movable block 22 is located relatively higher. The movable block 22 moves up and down in the Y-axis direction using a motor, and the size of the lens to be processed is determined using the distance traveled by the motor, that is, the position (height) of the movable block 22.

[0022] The carriage 12 is a typical device, on which a lens is mounted and which can move the mounted lens to be in contact with the polishing wheel 20. The carriage 12 moves the lens up and down and left and right, and rotates it to be in contact with the polishing wheel 20, and as the lens in contact with the polishing wheel 20 is polished, the carriage 12 descends, for example, by the action of gravity or the like, thereby causing the distance between the carriage 12 and the movable block 22 to be shortened. When the lens continues to be polished and the polishing depth of the lens reaches the “target depth” (i.e., when the polishing is completed), the carriage 12 and the movable block 22 come into contact with each other and the carriage 12 can no longer descend, thereby stopping the polishing of the lens as well. In this way, when the carriage 12 and the movable block 22 come into contact with each other, the processing is completed to the target depth at the corresponding position of the lens, and thus, the lens is separated from the polishing wheel 20, rotated to the next processing position, then the position of the movable block 22 is adjusted to the target polishing depth at the rotated position, and then the lens is brought into contact with the polishing wheel 20 again, thereby processing the corresponding position of the lens.

[0023] The eyeglass lens processing device used in the present invention uses the Hall sensor detection unit 30 to detect the positions of the movable block 22 and the carriage 12. As shown in FIG. 3, the Hall sensor detection unit 30 includes a magnet 32 and a Hall sensor 34, and the magnet 32 is mounted on one of the carriage 12 and the movable block 22, and the Hall sensor 34 is mounted on the other. In the eyeglass lens processing device, the physical contact between the movable block 22 and the carriage 12 only acts as a mechanical stopper for preventing a further descent of the carriage 12, and it is determined whether the movable block 22 and the carriage 12 are in contact with each other by means of a detection signal of the Hall sensor detection unit 30.

[0024] Therefore, as shown in FIGS. 1 and 3, the eyeglass lens processing device that may be used in the present invention may comprise lens-clamping shafts 10 configured to be rotated by a driving means 18 and to clamp the lens in a detachable manner, and having centers of their cross-section located on an extension line of the lens rotation axis; the movable block 22 in which the polishing wheel 20 for polishing the lens clamped and rotated by the lens-clamping shafts 10 is installed in the polishing wheel mount, and whose position changes according to the desired polishing depth of the lens; the carriage 12 configured to move the lens clamped and rotated by the lens-clamping shafts 10 to cause it to be in contact with the polishing wheel 20, and to come into contact with the movable block 22 when the lens in contact with the polishing wheel 20 is polished to the desired polishing depth; and the Hall sensor detection unit 30 in which the magnet 32 for detecting whether the movable block 22 and the carriage 12 are in contact and the Hall sensor 34 for detecting the strength of a magnetic field generated by the magnet 32 are mounted, respectively, on one of the carriage 12 or the movable blocks 22.

[0025] The Hall sensor 34 is a sensor that detects the direction and magnitude of a magnetic field using the Hall effect in which a voltage is generated in a direction perpendicular to an electric current and a magnetic field when the magnetic field is applied to an electrical conductor through which the current flows, and can obtain the position information of the magnet 32 by detecting the strength of the magnetic field generated by the magnet 32 with the Hall sensor 34. Therefore, it is possible to determine the positions of the movable blocks 22 and the carriage 12 (e.g., whether they are in contact) from output signals of the Hall sensor 34. For example, let an output value of the Hall sensor 34 be A while the movable block 22 and the carriage 12 are in contact, then it may be determined that the movable block 22 and the carriage 12 are spaced apart from each other if an output value of the Hall sensor 34 is less than or greater than A (depending on the polarity of the magnet).

[0026] FIG. 4 is a flow diagram showing a method of changing a lens rotation speed in the typical eyeglass lens processing device shown in FIG. 1. In the typical eyeglass lens processing device, one rotation (360 degrees) of a lens rotation axis is divided equally into m times to carry out the rotation, and each direction is processed. For example, if one rotation (360 degrees) of the lens rotation axis is divided equally into 180 times to carry out the rotation, the entire periphery (360 degrees) of the lens is processed by rotating 180 times with 2 degrees at a time. After processing the lens in one direction (e.g., an n.sup.th rotation), if the lens is rotated with an acceleration of a to process the next direction of the lens (an n+1.sup.th rotation direction, i.e., next part), then the force F exerted on the lens is proportional to the weight M of the rotating body including the lens and the rotational acceleration a. In case the weight M could not be changed, since the rotational acceleration a needed to be adjusted in order to adjust the force exerted on the lens, the rotational acceleration a was adjusted as in the manner of FIG. 4.

[0027] As shown in FIG. 4, in step S10, it is determined whether the contact sensor is in contact (On/Off) in the n.sup.th direction (n.sup.th time). At this time, if the contact sensor is in contact (On) in the n.sup.th direction, the rotational speed of the lens rotation axis is increased with an acceleration of a (S20) (however, the increased rotational speed is less than the maximum speed), and then the lens is rotated in the n+1.sup.th direction (n+1 times) (S30).

[0028] If the contact sensor is in non-contact (Off) in the n.sup.th direction, the rotational speed of the lens rotation axis is changed to or decelerated to the minimum speed (S25), and then the lens is rotated to the n+1.sup.th direction (n+1.sup.th time) (S30). After step S30, the process proceeds to step S10 again.

[0029] At this time, the overall processing speed of the lens is determined according to the acceleration a. If the acceleration a is set to a predetermined maximum speed or higher (i.e., if processing while rotating the lens too fast), a phenomenon in which the lens slips occurs. In order to prevent the lens from slipping, it is necessary to decrease the acceleration, thereby reducing the overall processing speed. Therefore, in order to process the lens at high speed, it is necessary to find an appropriate rotational speed.

[0030] Let the volume of the lens processed in a unit time t be L, then the processing speed V for the volume Ln to be processed in the n.sup.th direction may be expressed as Equation 1 below:

Processing speed(V)=k*Ln/L(k=proportional factor)   (Equation 1)

[0031] That is, in order to calculate the processing speed, it is necessary to calculate the volume of the lens; however, since an actual eyeglass lens has a spherical aberration consisting of multi-order terms, it is difficult to obtain the volume thereof. In addition, the lens volume L processed per unit time in Equation 1 indicates a grinding force, which also needs a separate measurement. In other words, since it is difficult to obtain the processing volume of the lens and also difficult to measure an absolute grinding force, a Hall sensor is used to measure a relative grinding force and to set an appropriate processing speed, thereby processing the lens faster in the present invention.

[0032] FIG. 5 is a graph showing a change in the value of a Hall sensor according to a distance in the eyeglass lens processing device shown in FIG. 3. With reference to FIG. 5, if the Hall sensor 34 of a non-contact type is used to convert the strength of the magnetic force of the magnet 32 (y-axis in the graph, Value) into a distance (x-axis in the graph, mm), the separation distance between the movable block 22 and the carriage 12 (the distance between the Hall sensor 34 and the magnet 32, referred to as “separation distance” below) may be determined at a relatively short distance, and control the rotational speed of the lens.

[0033] In an n.sup.th rotation direction of what is obtained by equally dividing one rotation (360 degrees) of the lens rotation axis into m times, let the separation distance between the movable block 22 and the carriage 12 be dn, then if m is sufficiently large, it can be said that dn=dn−1. When the polishing wheel 20 is stopped, if the separation distance in the first rotation direction is d1, then the separation distance in the second rotation direction becomes approximately d1+d2. If the polishing wheel 20 is rotated and the lens is polished, the separation distance will be less than d1+d2 in the second direction of rotation, and if the separation distance d2 in the second direction is equal to or less than the separation distance d1 in the first direction, it may be considered that the lens is sufficiently processed in the first direction.

[0034] Although the correlation between the separation distance d and the grinding force may not be known, if the separation distance d is kept constant, the grinding force and the processing speed V in the corresponding rotation direction may be considered appropriate. In other words, although an absolute grinding force may not be measured, an appropriate grinding force can be determined by estimating relative magnitudes of the previous grinding force and the current grinding force from the separation distance d. In this way, in order to maintain an appropriate grinding force, if the lens is processed while maintaining the separation distance d to be equal to or less than a certain distance, the processing speed Vn in the n.sup.th rotation direction may be considered the maximum speed Vmax. Since the amount to be processed is the same even if processed at a speed higher than the maximum speed Vmax, a speed higher than the maximum speed Vmax does not affect the lens processing speed. In summary, if a constant separation distance dx is maintained for 360 degrees of the entire periphery of the lens, the lens can be processed at the fastest speed possible.

[0035] If the lens is processed with an excessively slow lens rotation speed, the lens may have been processed with a more grinding force over a longer time. In this case, the separation distance d becomes dn<dn−1≤dx, and so, it is necessary to increase the rotational speed (i.e., processing speed) of the lens again such that dn<dn+1≤dx. On the contrary, if the lens is processed at an excessively high speed, the lens is processed for a shorter time, with the grinding force being insufficient. In this case, the separation distance d becomes dn>dx, and so, it is necessary to decrease the processing speed such that dn+1≤dx.

[0036] If the processing speed is set to be too high, the lens is rotated before grinding is carried out, and so, lens slippage is likely to occur. Therefore, it is necessary to reduce the set processing speed below a threshold. This was also applied to the conventional method of FIG. 4.

[0037] However, since the conventional method determines only the on and off of the contacts, whereas the Hall sensor can determine a distance value in a certain section as shown in FIG. 5, if the speed is controlled within a range by setting an upper limit dx_high and a lower limit dx_low of a constant separation distance, it is possible to prevent the occurrence of situations in which the speed must be reduced below the threshold. Since the lower limit dx_low is a value greater than ‘0,’ setting the lower limit does not affect the processing speed. However, if the upper limit is set too high and the rotation is carried out at the existing speed with the upper limit, lens slippage may occur due to an insufficient grinding force. Therefore, it is necessary to set an appropriate upper limit dx_high.

[0038] For the 360-degree rotation of the lens to be processed, if a position control movement is made m times (points, turns), the lens rotates 360/m degrees by one-time position control. The radius of a typical eyeglass lens does not exceed 85 mm, and the radius of a normal lens does not exceed 50 mm. The maximum separation distance for one rotation, dmax, generated by one rotation of the lens is “50 mm*tan (360/m)”.

[0039] If it is set such that the lower limit dx_low+the maximum separation distance for one rotation, dmax=the upper limit dx_high, then a slip of less than 360/m degrees may occur. However, if the lens is rotated without being processed, part of the rotational force exerted on the lens may be canceled out by the clearance of the mechanism, and thus, if the value of m is set to a range or higher that does not affect the lens processing performance and is set to a certain value or lower for a discernable maximum distance dmax, the final lens to be processed can be processed at maximum speed without slipping.

[0040] Furthermore, the amount of change in speed to keep the separation distance d within the constant separation distance dx is controlled according to the amount of increase in the separation distance, and the separation distance within the lower limit dx_low and the upper limit dx_high minimizes control elements to prevent unnecessary speed changes.

[0041] FIG. 6 is a flow diagram showing a method of changing a lens rotation speed using a Hall sensor in a method for controlling an eyeglass lens processing device in accordance with the present invention. Referring to FIG. 6, the method for controlling an eyeglass lens processing device using a Hall sensor of the present invention is performed by the following steps.

[0042] First, the lens is polished in an n.sup.th rotation direction of what is obtained by equally dividing one rotation (360 degrees) of the lens rotation axis into m, and a separation distance dn between the movable block 22 and the carriage 12, that is, a distance between the magnet 32 and the Hall sensor 34 of the Hall sensor detection unit 30 is measured (S100). As described above, a position of the movable block 22 represents a target polishing position of the lens in the n.sup.th rotation direction, a position of the carriage 12 represents a polishing position of the lens in the n.sup.th rotation direction, and the separation distance dn between the movable block 22 and the carriage 12 serves as a polishing index representing a difference between the target polishing position of the lens and the polishing position of the lens.

[0043] Next, it is determined whether the separation distance dn in the n.sup.th rotation is less than a predetermined separation distance upper limit dx_high (S200).

[0044] In step S200 above, if the separation distance dn in the n.sup.th rotation is greater than or equal to the predetermined separation distance upper limit dx_high, it is determined whether (a separation distance dn−1 in an n−1.sup.th rotation)/(a separation distance dn−2 in an n−2.sup.th rotation) is greater than or equal to (the separation distance dn in the n.sup.th rotation)/(the separation distance dn−1 in the n−1.sup.th rotation) (S210).

[0045] In step S210 above, if (the separation distance dn−1 in the n−1.sup.th rotation)/(the separation distance dn'2 in the n−2.sup.th rotation) is greater than or equal to (the separation distance dn in the n.sup.th rotation)/(the separation distance dn−1 in the n−1.sup.throtation), the rotational speed of the lens rotation axis is rapidly increased (S220), thereby rotating the lens to the n+1.sup.th rotation position (S400). On the other hand, in step S210 above, if (the separation distance dn−1 in the n−1.sup.th rotation)/(the separation distance dn−2 in the n−2.sup.th rotation) is less than (the separation distance dn in the n.sup.th rotation)/(the separation distance dn−1 in the n−1.sup.th rotation), the rotational speed of the lens rotation axis is increased slowly (S225), thereby rotating the lens to the n+1.sup.th rotation position (S400).

[0046] In step S200 above, if the separation distance dn in the n.sup.th rotation is less than the predetermined separation distance upper limit dx_high, it is determined whether the separation distance dn in the n.sup.th rotation is greater than or equal to a predetermined separation distance lower limit dx_low (S300).

[0047] In step S300 above, if the separation distance dn in the n.sup.th rotation is less than the predetermined separation distance lower limit dx_low, it is determined whether (the separation distance dn−1 in the n−1.sup.th rotation)/(the separation distance dn−2 in the n−2.sup.th rotation) is less than (the separation distance dn in the n.sup.th rotation)/(the separation distance dn−1 in the n−1.sup.th rotation) (S310).

[0048] In step S310 above, if (the separation distance dn−1 in the n−1.sup.th rotation)/(the separation distance dn−2 in the n−2.sup.th rotation) is less than (the separation distance dn in the n.sup.th rotation)/(the separation distance dn−1 in the n−1.sup.th rotation), the rotational speed of the lens rotation axis is rapidly decreased (S320), thereby rotating the lens to the n+1.sup.th rotation position (S400). On the other hand, in step S310 above, if (the separation distance dn−1 in the n−1.sup.th rotation)/(the separation distance dn−2 in the n−2.sup.th rotation) is greater than or equal to (the separation distance dn in the n.sup.th rotation)/(the separation distance dn−1 in the n−1.sup.th rotation), the rotational speed of the lens rotation axis is decreased slowly (S325), thereby rotating the lens to the n+1.sup.th rotation position (S400).

[0049] In step S300 above, if the separation distance dn in the n.sup.th rotation is greater than or equal to the predetermined separation distance lower limit dx_low, the lens is rotated to the n+1.sup.th rotation position (S400).

[0050] In this way, if a predetermined separation distance upper limit dx_high and a lower limit dx_low are set, and processed while controlling as shown in FIG. 6, the lens can be processed stably while maintaining the maximum grinding force.

[0051] According to the method for controlling an eyeglass lens processing device in accordance with the present invention, it is possible to maintain the rotational speed of a lens rotation axis for processing a lens to be constant, to increase the average processing speed, and to prevent the lens from slipping.

[0052] Although the present invention has been described by way of limited embodiments and drawings as set forth above, the present invention is not limited to the above embodiments, and those of ordinary skill in the art to which the present invention pertains can make various modifications and variations from such descriptions. Therefore, the spirit of the present invention should be understood only by the claims set forth below, and all equal or equivalent modifications thereof are intended to be within the scope of the spirit of the present invention.