JP2007253280A - Grinding method for optical spherical lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for grinding spherical lens, capable of shortening grinding work time, and rationalizing process control by conducting rough grinding in such a way that fine grinding can be performed in a single process. <P>SOLUTION: Rough grinding for creating a spherical lens surface is conducted in the following conditions (1)-(3). (1) Rough grinding to a lens material is conducted using a spherical center oscillation type grinding machine. (2) For a rough grinding tool disc, a diamond tool of #300-#600 (average grain size of 60μm-30μm), and a concentration degree of 50 or more is used. (3) The rotation speed of the rough grinding tool disc is set at 2500rpm-3500rpm. Surface roughness and spherical surface precision in a rough grinding process can thus be improved in such a way that the stock removal in the subsequent fine grinding process can be less than about 20μm. Grinding work time is shortened, and process control is rationalized. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lens grinding method for grinding an optical spherical lens used in a digital camera or the like, and more specifically, by making the precision grinding process a single grinding process, the machining time can be shortened and the process management is performed. The present invention relates to a grinding method that makes it easy to perform.

  As a method for grinding an optical spherical lens, a spherical surface creation method using a cup-type grindstone is widely known. For example, the lens spherical surface is processed through three steps of a rough grinding step, a fine grinding step, and a polishing step. As described in Non-Patent Document 1, the necessary margin for each step is 0.5 to 2 mm for rough grinding, 30 to 50 μm for fine grinding, and 10 to 20 μm for polishing. The surface roughness Rmax is 6 to 10 μm for rough grinding, 0.5 to 4 μm for fine grinding, and 0.01 to 0.02 μm for polishing. Table 1 shows a general range of margins, abrasive grains, and surface roughness in each step.

  Here, the calculation standard for the necessary margin is a value obtained by adding an R value error to four times the maximum surface roughness of the previous process, and the necessary margin for the process is determined by the surface roughness of the previous process. Further, an optimum diamond tool particle size is selected in accordance with the distribution of processing time in each process. In particular, based on the surface roughness in the rough grinding process, which is the first grinding process, the processing time distribution in the subsequent process and the grain size of the diamond tool are determined. Based on this, it is desirable that the margin of the fine grinding process is 50 μm in view of safety, and the surface roughness is 0.5 μm.

  In order to reduce the surface roughness, it is necessary to reduce the particle size of the diamond tool. However, if the particle size is reduced, the processing time naturally becomes longer. Therefore, conventionally, the fine grinding process is divided into two processes in consideration of the surface roughness, the allowance, and the processing time in the fine grinding process. In the first step, a 40 μm margin is ground using a metal bond grindstone as a diamond tool, and in the second step, the remaining 10 μm margin is ground using a resin bond grindstone with a smaller particle size as a diamond tool. As a result, fine grinding with a margin of 50 μm and a surface roughness of 0.5 μm is realized.

  In the spherical lens grinding process, if the surface roughness in the precision grinding process is sacrificed, the precision grinding can be performed in a single process and the machining time can be shortened. However, as described above, the surface roughness in the previous process is used as a reference to determine the allowance for the next process, and in this case, the allowance in the polishing process, which is the next process, increases. Processing time will be significantly longer. Therefore, the overall machining time cannot be shortened.

  In Patent Document 1, the rough grinding process and the fine grinding process are made into a single process, so that the grinding time of the spherical lens is shortened, and the processing apparatus is also used for rough grinding and fine grinding. A processing method is disclosed which requires only two types for the purpose. In the method disclosed herein, the rotational speed of the grindstone is increased to 5000 to 10,000 rpm in order to perform the rough grinding step and the fine grinding step in a single step.

When the method disclosed in Patent Document 1 is employed, rough grinding and fine grinding can be performed with a single processing apparatus, so that processing time can be shortened and process management is simplified. However, it is necessary to set the rotational speed of the grindstone to a rotational speed more than double the 2000 to 3000 rpm employed in general spherical lens processing. Further, as disclosed in Patent Document 1, the obtained surface roughness is about 2 μm, and it is impossible to obtain a surface roughness of about 0.5 μm. It is necessary to increase the margin.
Optical element processing technology '91, Japan Opto-Mechatronics Association, issued on September 5, 1991, 1-2 optical element processing process, 1-4 grinding / polishing Utility Model Registration No. 2600063

  When it is assumed that spherical lens grinding is performed in three steps: rough grinding, fine grinding, and polishing, surface roughening in rough grinding can be performed in order to reduce the time required for grinding and rationalize process management. It is desirable to reduce the fine grinding allowance so that fine grinding can be performed in a single step.

  In view of these points, the object of the present invention is to perform rough grinding so that fine grinding can be performed in a single process, thereby shortening the time for grinding the spherical lens and rationalizing process management. The object is to propose a grinding method of a spherical lens that can achieve the above.

  In order to solve the above-described problems, the present invention provides a rough grinding process for roughly creating a lens spherical surface by grinding a lens material to be processed using a rough grinding tool pan, and the rough grinding tool for forming the created lens spherical surface. In the method of grinding an optical spherical lens including a fine grinding step of fine grinding using a diamond tool finer than a plate and a polishing step of polishing the lens spherical surface after fine grinding, the rough grinding step is performed under the following conditions: It is characterized in that it is performed according to (1) to (3).

(1) Rough grinding of the lens material using a ball centering grinder
As the spherical rocking grinder, the rough grinding tool plate having a spherical grinding surface is rotated around a rotational center line passing through the spherical spherical center, and the rotational center line moves the spherical center. The coarse grinding tool plate is pivoted so as to draw a conical surface as a vertex, the lens material is rotated at the same speed in the same direction as the rough grinding tool plate, and the coarse grinding tool plate is rotated and pivoted. The ground material is pressed in the direction passing through the spherical center of the rough grinding tool plate, and while the lens material is fed in the same direction in this state, the lens material is subjected to spherical grinding, and the rough grinding tool plate is It is supported in a freely rotating state by a center rocking body, and the outer peripheral surface of this ball center rocking body is a spherical surface, and this outer circumferential surface is a spherical support surface centering on the spherical center of the grinding surface of the rough grinding tool pan. Compressed air is supplied between the outer peripheral surface and the support surface The spherical center swinging body is floated and used as a configuration in which spherical center swinging the spherical center swinging body while maintaining a floating state Te.
(2) As the rough grinding tool pan, a diamond tool having # 300 to # 600 (average particle size of 60 μm to 30 μm) and a concentration degree of 50 or more is used.
(3) The rotational speed of the rough grinding tool pan is 2500 rpm to 3500 rpm.

  According to the grinding method of the optical spherical lens of the present invention, the spherical accuracy (Δh) in the rough grinding step can be maintained within −0.003 mm with respect to the spherical accuracy in the polishing step. The margin in the process can be 20 μm or less per side. As a result, the precise grinding process can be a single grinding process. Thereby, shortening of processing time and rationalization of process management can be achieved.

  According to the grinding method of the optical spherical lens of the present invention, the surface roughness of the rough grinding process can be improved so that the allowance in the fine grinding process is about 20 μm or less. Therefore, according to the present invention, since precise grinding can be performed in a single process, the grinding time as a whole can be shortened, and process management can be rationalized.

  Hereinafter, an optical spherical lens grinding method to which the present invention is applied will be described with reference to the drawings.

  FIG. 1 is a process diagram showing a grinding method of an optical spherical lens of this example. As shown in this figure, the grinding method of the present example includes three steps of a rough grinding step ST1, a fine grinding step ST2, and a polishing step ST3. The rough grinding step (CG step) ST1 is a step of roughly creating a lens spherical surface by grinding a lens material to be processed using a diamond tool (rough grinding tool pan). The fine grinding step ST2 is a step of finely grinding the created lens spherical surface using a diamond tool whose count is finer than the coarse grinding tool pan, and is a single grinding step. The grinding machine to be used is not limited to the ball center swing type, and a grinder using a general cup type grindstone can be used. A resin bond grindstone may be used as the diamond tool. Next, the polishing step ST3 is a step of polishing the lens spherical surface after fine grinding. In this step, the spherical surface is polished with a polishing liquid containing cerium oxide or the like, for example, with a urethane sheet.

(Rough grinding process)
In the rough grinding step ST1 of this example, a spherical surface is created on the lens material under the following conditions (1) to (3).
(1) A lens material is roughly ground using a ball center rocking type grinding machine, and a ball center rocking grinding apparatus having the configuration shown in FIG. 2 is adopted.
(2) As a rough grinding tool plate, a diamond tool having # 300 to # 600 (average particle size of 60 μm to 30 μm) and a concentration degree of 50 or more is used.
(3) The rotational speed of the rough grinding tool plate is 2500 rpm to 3500 rpm, for example 3000 rpm.

(Spherical rocking grinder)
The schematic configuration and operation of the spherical rocking grinder 1 of this example are as follows. A rough grinding tool plate having a spherical grinding surface is rotated around a rotation center line passing through the spherical center of the spherical surface, and the rotation center line draws a conical surface with the spherical center at the top. Rock heart. The lens material is rotated at the same speed in the same direction as the rough grinding tool pan, and pressed against the grinding surface of the coarse grinding tool pan rotating and pivoting in the direction passing through the center of the rough grinding tool pan. The lens material is subjected to spherical grinding while feeding the lens material in the same direction. Here, the rough grinding tool pan is supported by a spherical rocking body so as to be freely rotatable, the outer peripheral surface of the spherical rocking member is a spherical surface, and this outer circumferential surface is centered on the spherical surface of the grinding surface of the rough grinding tool pan. Is placed on a spherical support surface, and compressed air is supplied between the outer peripheral surface and the support surface to float the spherical rocking body, and the spherical rocking body is swung while maintaining the floating state. It is supposed to let you.

  Referring to FIG. 2 in detail, the spherical rocking grinder 1 of this example includes a lens holder 3 for holding a lens material W to be processed, and a lens material held by the lens holder 3. A tool plate 4 having a spherical grinding surface 4a for grinding W is provided.

  The lens holder 3 is fixed to the lower end of the vertical lens spindle 5 with the holding surface 3a held horizontally so that the holding surface 3a faces downward. A suction passage 5 a extending in the axial direction is formed at the center of the lens spindle 5, its lower end opens to the center of the holding surface 3 a of the lens holder 3, and its upper end passes through the rotary joint 6 and the air filter 7. Via the suction side of the vacuum generator 8. By vacuum-suctioning the suction passage 5 a by the vacuum generator 8, the lens material W is sucked and held on the holding surface 3 a of the lens holder 3.

  The lens spindle 5 is coaxially arranged inside a cylindrical vertical holding cylinder 9 whose upper end is sealed, and is supported by the vertical holding cylinder 9 in a rotatable state via a pair of upper and lower bearings 10 and 11. ing. The lens spindle 5 is rotationally driven by a lens shaft rotating motor 12 around a lens rotation center line 5A which is a vertical center line thereof. An air cylinder 13 is connected to the upper end of the vertical holding cylinder 9, and the air cylinder 13 is fixed inside a support cylinder 14 whose upper end is sealed. The vertical holding cylinder 9 is pressed downward by a predetermined force by the air cylinder 13.

  The lens spindle 5 is moved up and down by a work feeding mechanism 20. The workpiece feeding mechanism 20 includes a horizontal arm 21, and the vertical holding cylinder 9 is inserted in a coaxial state into a vertical cylindrical portion 22 attached to the tip of the horizontal arm 21, and the support cylinder 14 is placed on the horizontal arm 21 on the upper surface. It is fixed. The horizontal arm 21 is moved up and down along the vertical linear guide 26 by a lifting mechanism including a feed screw 23, a nut 24, and a servo motor 25.

  Here, the proximity cylinder 27 for detecting the upper end 9a of the vertical holding cylinder 9 attached to the inside of the support cylinder 14 supporting the lens spindle 5 via the air cylinder 13 is attached. . Normally, the proximity sensor 27 is in an off state, and when the vertical holding cylinder 9 rises relative to the support cylinder 14, the upper end 9a is detected by the proximity sensor 27, and the sensor output is turned on.

  Next, the tool plate 4 disposed below the lens holder 3 is disposed such that the spherical center O of the spherical grinding surface 4a is positioned on the extension of the lens rotation center line 5A on the lens holder 3 side. . A spindle 4 b is integrally formed on the back surface of the tool plate 4, and the spindle 4 b is supported in a freely rotatable state by a spherical rocking body 31. Here, the spindle 4b is supported by the ball center rocking body 31 so that the rotation center line 4A of the tool plate 4 intersects the lens rotation center line 5A extending vertically at an acute angle θ at the ball center O. .

  The spherical rocking body 31 includes a hemispherical cup portion 31a and a cylindrical portion 31b projecting radially outward from the outer peripheral surface portion at the center of the bottom of the cup portion 31a, and is coaxial with the cylindrical portion 31b. The spindle 4b is attached in a rotatable state. A flange 31c extends laterally from the lower end of the cylindrical portion 31b, and a spindle driving motor 32 is mounted on the flange 31c.

  The cup portion 31 a of the ball center rocking body 31 is supported by a ring-shaped inner peripheral surface 33 a formed on the support plate 33 in a state in which the ball core can rock. The annular inner peripheral surface 33a is a spherical surface having the spherical center O as a spherical center, and the cup portion 31a having a spherical outer peripheral surface 31d placed on the annular inner peripheral surface 33a can swing around the spherical center O. It is. In this example, a compressed air blowing hole or groove 33b is formed in the annular inner peripheral surface 33a, and the compressed air is supplied to the annular inner peripheral surface 33a through a compressed air supply path 33c. Accordingly, the cup portion 31a is held in a state of being lifted from the annular inner peripheral surface 33a. Therefore, the ball swinging body 31 can be swung smoothly around the ball center O.

  The lower end of the ball swinging body 31 is connected to the output shaft of the electric motor 36 via a link joint 34 and a swinging width adjusting unit 35. The connection point 34a between the ball center rocking body 31 and the link joint 34 is located on the extension line of the tool pan rotation center line 4A, and the rotation center line 36A of the electric motor 36 is always kept facing the ball center O. When the adjustment knob 35a of the swinging width adjustment unit 35 is operated, the distance between the connection point 34a and the rotation center line 36A of the electric motor 36 changes. Therefore, the swing width of the swing motion of the ball center swing body 31 can be adjusted.

  Next, the electric motor 36 is supported by a swing angle adjusting unit 37. The swing angle adjusting unit 37 includes an arcuate cam 38 disposed at a fixed position, and the cam 38 has an arc shape with the sphere center O as the center. A support member 39 is attached so as to be slidable along the cam 38, and an electric motor 36 is attached thereto. A nut 40 is fixed to the support member 39, and a feed screw 41 is screwed into the nut 40. The end of the feed screw 41 is connected to the handle 42.

  When the handle 42 is turned, the support member 39 moves along the cam 38. That is, the tool plate spindle 4b supported by the ball center rocking body 31 rocks by a predetermined amount around the ball center O. Therefore, the swing angle adjusting unit 37 can change the angle θ formed by the rotation center line 4A of the tool plate 4 with respect to the vertical lens rotation center line 5A, that is, the angle of the swing center line.

  Here, the drive control of each part is performed by the controller 50 for numerical control. An input device 51 is connected to the controller 50. Through the input device 51, the lens material can be sent out by manual operation, and the cutting amount can be set.

  With reference to FIG. 3, a rough grinding operation for creating a lens spherical surface on the lens material W by using the spherical rocking grinder 1 having this configuration will be described.

  First, as the tool pan 4, a diamond pellet having a concentration degree of 50 or more with # 300 to # 600, for example, # 400, prepared so as to match the target spherical shape is prepared. It is attached to the spindle 4b. At this time, adjustment is made so that the center of the spherical grinding surface of the tool plate 4 is positioned on the rotation center line of the tool plate 4 and coincides with the swing center of the spherical rocking body 31. Next, the lens material W is sucked and held by the lens holder 3 at a position where it does not contact the tool plate 4. Next, the servo motor 25 is driven by a manual operation, and the lens material W is jog-fed toward the tool plate 4. When the lens material W comes into contact with the tool tray 4, the lowering of the lens spindle 5 stops. Thereafter, only the horizontal arm 21 (work feed table) is lowered by jog feed. As a result, the lens spindle 5 and the vertical holding cylinder 9 that rotatably supports the lens spindle 5 are raised relative to the horizontal arm 21, and the proximity sensor 27 detects the upper end 9a of the vertical holding cylinder 9. Switch on.

  After confirming that the proximity sensor 27 is switched on, the jog feed is temporarily stopped. Thereafter, the feed speed of the servo motor 25 is set to an extremely low speed, and the horizontal arm 21 is raised. When the horizontal arm 21 is raised, the stopped lens spindle 5 and vertical holding cylinder 9 are lowered relative to the proximity sensor 27. As a result, the upper end 9a of the vertical holding cylinder is disengaged from the detection position of the proximity sensor 27, and the proximity sensor 27 is turned off again. The controller 50 stores the position at the moment of switching off as the machining start position.

  The controller 50 adds the machining allowance from the machining start position and sets the machining completion position. Also, the speed change point is set by adding the amount of the first cutting amount to the machining start position. When a machining start command is input after setting each point in this manner, the rotation of the lens material W that is sucked and fixed to the tool plate 4 and the lens holder 3 is started. Further, the swing motion of the ball center swing body 31 is started.

  In this example, the tool plate 4 and the lens material W are rotated in the same direction at the same speed of 3000 rpm. Thereafter, the lens material W is sent out to the processing start position by fast-forwarding.

  After reaching the machining start position, the speed is switched to the first cutting speed, and grinding is performed while feeding the lens material W at this speed. FIG. 3 (a) shows a state at the start of grinding.

  After the lens material W is cut by the first cutting amount and reaches the first cutting position, that is, after reaching the cutting state as shown in FIG. Then, cutting is performed while feeding the lens material W at a finishing speed slower than the first cutting speed. As a result, the lens material W is ground to form a spherical lens surface Wa as shown in FIG.

  When it is confirmed that the machining completion position has been reached, the horizontal arm 21 is raised to the upper end position after stopping the swinging by the ball swinging body 31. Thereafter, the rotation of the tool plate 4 and the lens material W is stopped.

  According to the rough grinding step ST1 of this example, the grinding accuracy in the rough grinding step can be increased, and the spherical accuracy (Δh) in the rough grinding step is within −0.003 mm with respect to the spherical accuracy in the polishing step. Can be maintained. As a result, the margin in the next precision grinding step ST2 is 20 μm or less per side. For this reason, in the said precise grinding process ST2, it can be set as the single grinding process using the resin bond grindstone. Thereby, shortening of processing time and rationalization of process management can be achieved.

  Table 2 is a table showing an example of conditions and results when the spherical lens is ground by applying the present invention. In this example, the allowance in the rough grinding process is 1 mm. It was confirmed that the surface roughness (Rmax) and the spherical surface accuracy (Δh) of the rough grinding process can be improved, and the allowance in the next fine grinding process may be 15 μm. As a result, it was confirmed that the fine grinding process can be performed only once and the processing time is 20 seconds.

  On the other hand, in the case of a conventional lens grinding method, that is, a margin in precision grinding is 30 to 50 μm, and a method including two steps of a grinding step with a metal bond grindstone and a grinding step with a resin grindstone, As shown in the last column, the processing time for rough grinding and polishing is the same as in this example, but the precise grinding process takes 40 seconds, which is twice the processing time in this example. In addition, since the precision grinding process consists of two steps, work time for transferring the lens material from one grinding machine to the other grinding machine is required. In addition, process management is more complicated than in the case of one process.

  As described above, when the grinding method of the present invention is employed, the surface roughness and spherical accuracy of the rough grinding can be improved so that the allowance in the fine grinding process is about 20 μm or less. Therefore, since the fine grinding can be performed in a single process, the grinding time as a whole can be shortened, and the process management can be rationalized.

It is process drawing which shows the grinding process process of the spherical glass lens by this invention. It is a schematic block diagram which shows the ball center rocking | swiveling type grinding machine suitable for using for rough grinding. It is explanatory drawing which shows the grinding operation by the grinding machine of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ball center rocking type grinding machine, 3 Lens holder, 4 Tool plate, 4a Spherical grinding surface, 4A Tool plate rotation center line, 5 Lens spindle, 5A Lens rotation center line, 20 Work lifting mechanism, 21 Horizontal arm, 31 Ball swing body, 33 support plate, 33a annular inner peripheral surface, 33b compressed air blowing hole or groove, 35 swing width adjusting unit, 36A rotation center line, 37 swing angle adjusting unit, W lens material, O ball center

Claims (3)

A rough grinding process in which a lens material to be processed is ground using a coarse grinding tool plate to create a rough lens spherical surface, and the created lens spherical surface is refined using a diamond tool with a finer count than the rough grinding tool plate. In an optical spherical lens grinding method including a fine grinding step for grinding and a polishing step for polishing a lens spherical surface after fine grinding, the rough grinding step is performed according to the following conditions (1) to (3): An optical spherical lens grinding method.
(1) Rough grinding of the lens material using a ball centering grinder
As the spherical rocking grinder, the rough grinding tool plate having a spherical grinding surface is rotated around a rotational center line passing through the spherical spherical center, and the rotational center line moves the spherical center. The coarse grinding tool plate is pivoted so as to draw a conical surface as a vertex, the lens material is rotated at the same speed in the same direction as the rough grinding tool plate, and the coarse grinding tool plate is rotated and pivoted. The ground material is pressed in the direction passing through the spherical center of the rough grinding tool plate, and while the lens material is fed in the same direction in this state, the lens material is subjected to spherical grinding, and the rough grinding tool plate is It is supported in a freely rotating state by a center rocking body, and the outer peripheral surface of this ball center rocking body is a spherical surface, and this outer circumferential surface is a spherical support surface centering on the spherical center of the grinding surface of the rough grinding tool pan. Compressed air is supplied between the outer peripheral surface and the support surface The spherical center swinging body is floated and used as a configuration in which spherical center swinging the spherical center swinging body while maintaining a floating state Te.
(2) As the rough grinding tool pan, a diamond tool having # 300 to # 600 (average particle size of 60 μm to 30 μm) and a concentration degree of 50 or more is used.
(3) The rotational speed of the rough grinding tool pan is 2500 rpm to 3500 rpm. In claim 1,
A grinding method for an optical spherical lens, characterized in that the spherical accuracy (Δh) in the rough grinding step is maintained within −0.003 mm with respect to the spherical accuracy in the polishing step. In claim 1 or 2,
The margin in the fine grinding process is 20 μm or less per side,
An optical spherical lens grinding method, wherein the precision grinding step is a single grinding step.

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