JP2007136623A - Axisymmetric aspheric surface polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axisymmetric aspheric surface polishing method, simply correcting a polishing target value in a short time to polish an axisymmetric aspheric surface even when the polishing removing amount of an axisymmetric aspheric surface extending from the central axis of rotation to the peripheral edge part has a tendency of excess or shortage, thereby making the axisymmetric aspheric surface into a favorable optical surface. <P>SOLUTION: In this axisymmetric aspheric surface polishing method, the axisymmetric aspheric surface 1 after grinding is rotated round the center axis C of rotation of the axisymmetric aspheric surface 1, a rotating spherical polisher 6 is pressed from the normal direction of the axisymmetric aspheric surface 1, and scanned in the direction of a meridian to polish the whole of the axisymmetric aspheric surface 1. The method includes a correcting and polishing process of changing the ratio of the rotational frequency of the axisymmetric aspheric surface 1 to the rotational frequency of the polisher 6 after polishing the whole of the axisymmetric aspheric surface 1 to perform polishing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides an optical element having an optical aspheric surface such as a lens or a mirror, or a workpiece (work) such as a molding die for molding the optical element, for processing a good optical surface. The present invention relates to an axisymmetric aspheric polishing method.

  As a polishing method for processing an optically axisymmetric aspherical surface, the aspherical axis of a workpiece having an axially symmetric aspherical surface is rotated around the rotation center axis, and the rotating polisher is moved in the normal direction of the axisymmetric aspherical surface of the workpiece. While being pressed, the scanning is performed along the meridian, and the whole of the axisymmetric aspheric surface is polished by the relative movement of the two (for example, see Patent Document 1).

  In such a method, the polisher presses the axisymmetric aspherical surface after grinding from the normal direction based on the polishing target value, which is the NC or CNC polishing data created from actual processing or sample polishing. Attitude control and speed control. That is, at the contact portion between the axisymmetric aspherical surface and the polisher, the number of rotations of the workpiece and the polisher and the polisher feed so that the polishing removal amount by the polisher is equal at any position on the axisymmetric aspherical surface. The speed is decided.

  In this way, the axisymmetric aspheric surface is rotated about the rotation center axis, and the polisher is moved along the meridian of the axisymmetric aspheric surface while the polisher is pressed against the axisymmetric aspheric surface to polish the whole. Such a whole polishing is repeated from one time to a plurality of times as necessary to process a good optical aspherical surface.

Here, after the entire polishing for the purpose of uniform removal depth is performed on the shape of the axisymmetric aspherical surface before polishing, the polishing removal depth in the vicinity of the rotation center axis (hereinafter referred to as a polishing removal amount). ) Is more frequent than the peripheral portion. At this time, the result of the actual processing or sample polishing processing is discarded, and the polisher feed speed (by using the arithmetic unit is set so that the polishing removal depth is uniform in any part of the axisymmetric aspherical surface from the shape error. Hereinafter, the dwell time is calculated), and the polishing target value serving as the polishing data is corrected.
JP 2000-254848 A JP 2003-68688 A

However, according to the above-mentioned conventional axisymmetric aspherical polishing method, the polishing target value is corrected for the dwell time of the polisher using an arithmetic unit, so that a comparison calculation with the polishing target value before polishing is also necessary. Therefore, it takes more time and time to create the corrected polishing target value than before correction.
The present invention has been made in view of the above circumstances, and even if the removal amount of the axisymmetric aspherical surface from the rotation center axis to the peripheral portion shows an excessive tendency or an insufficient tendency, the polishing target value is simply set. An object of the present invention is to provide an axisymmetric aspherical polishing method that can correct and polish in a short time and can make an axisymmetric aspherical surface a good optical surface.

The present invention employs the following means in order to solve the above problems.
In the axially symmetric aspherical polishing method according to the present invention, the axisymmetric aspherical surface after grinding is rotated about the rotation center axis of the axisymmetric aspherical surface, and the rotating spherical polisher is moved from the normal direction of the axisymmetric aspherical surface. In the axially symmetric aspherical polishing method of pressing and scanning in the meridian direction to polish the entire axisymmetric aspherical surface, after the overall polishing of the axisymmetric aspherical surface, the rotational speed of the axisymmetric aspherical surface and the polisher And a modified polishing step for polishing by changing the ratio of the number of rotations.

  This invention changes the ratio of the rotational speed of the axisymmetric aspherical surface and the rotational speed of the polisher even if the removal amount of the axially symmetric aspherical surface from the rotational center axis line to the peripheral portion tends to be excessive or insufficient. Thus, the polishing removal amount according to the distance from the rotation center axis can be changed without changing the dwell time and angle of the polisher with respect to the axisymmetric aspheric surface, and the polishing target value can be corrected.

  Further, an axially symmetric aspherical surface polishing method according to the present invention is the axially symmetric aspherical surface polishing method, wherein a polishing removal amount with respect to a polishing target value of the axially symmetric aspherical surface before polishing is In the case where there is a tendency to excessively or insufficiently linearly extend from the rotation center axis of the axisymmetric aspheric surface to the peripheral portion, the modified polishing step calculates the polishing removal amount from the rotation speed of the axisymmetric aspheric surface and the rotation speed of the polisher. A step of calculating an approximate expression having a linear inclination in a direction that eliminates the tendency of excess or deficiency of the polishing removal amount from a linear function for calculation, and rotation of the axisymmetric aspherical surface from the approximate expression And calculating the corrected polishing target value by back-calculating the number and the number of rotations of the polisher.

  In the present invention, when the shape measurement result of the axisymmetric aspherical surface before polishing and the shape measurement result after polishing were compared, the polishing removal amount tended to be excessive or insufficient linearly from the rotation center axis to the peripheral edge. In this case, by calculating an approximate expression that reverses this tendency, the rotational speed of the axisymmetric aspherical surface to be corrected and the rotational speed of the polisher can be calculated.

  An axially symmetric aspherical surface polishing method according to the present invention is the axially symmetric aspherical surface polishing method, wherein the rotational speed of the axially symmetric aspheric surface and the rotational speed of the polisher at the polishing target value before correction are determined. When the rotation speed of the axisymmetric aspherical surface and the rotation speed of the polisher are Nwi and Npi, respectively, at the corrected polishing target value, respectively, Nwo and Npo, the function is such that Npi / Nwi is higher than Npo / Nwo. When it is small, the polishing removal amount is gradually increased from the vicinity of the rotation center axis of the axisymmetric aspheric surface toward the peripheral portion, and when Npi / Nwi is larger than Npo / Nwo, the rotation center of the axisymmetric aspheric surface is increased. The polishing removal amount tends to gradually decrease from the vicinity of the axis toward the peripheral portion.

  In this invention, by changing the rotational speed of the axisymmetric aspheric surface and the rotational speed of the polisher, the polishing removal amount from the vicinity of the rotation center axis to the peripheral portion can be increased or decreased, and the polishing target value is easily corrected. can do.

An axially symmetric aspherical surface polishing method according to the present invention is the axially symmetric aspherical surface polishing method, wherein the function uses a Preston equation.
Since the present invention uses a function based on Preston's formula often used in simulations related to polishing, it can be applied without any sense of incongruity when creating NC or CNC data.

  According to the present invention, even if the removal amount of the axisymmetric aspherical surface from the rotation center axis to the peripheral portion shows an excessive tendency or an insufficient tendency, the polishing target value is corrected easily and evenly in a short time. Polishing can be performed with the polishing removal amount, and an axially symmetric aspherical surface can be a good optical surface.

An embodiment according to the present invention will be described with reference to FIGS.
In the axially symmetric aspherical polishing method according to this embodiment, as shown in FIG. 1, an aspherical workpiece 2 on which a convex axially symmetric aspherical surface 1 is formed is fixed to a workpiece yatoy 5 that can be rotated by a workpiece rotating shaft 3. Perform in the state. The workpiece rotation axis 3 on the rotation center axis C of the axisymmetric aspherical surface 1 is connected to a drive unit (not shown) and rotated, so that the axisymmetric aspherical surface 1 is based on polishing operation data (NC control). The attitude is controlled freely with respect to the XYθ direction shown in the figure. The polisher 6 has a spherical tip, is fixed via a drive unit (not shown) and a polisher rotating shaft 7, and can be rotated by the drive unit while being pressed against the axisymmetric aspherical surface 1, as shown in FIG. Has been.

  As shown in FIG. 2, the polishing process includes a uniform polishing step (S01) for polishing the entire axisymmetric aspherical surface 1 after grinding, and an axisymmetric aspherical surface 1 after obtaining a mirror surface (optical roughness). A shape measuring step (S02) and a modified polishing step (S03) for performing polishing by changing the ratio of the rotational speed of the axisymmetric aspherical surface 1 and the rotational speed of the polisher after the entire polishing of the axially symmetric aspherical surface 1 is performed. ing.

  In the uniform polishing step (S01), the aspherical workpiece 2 after grinding is rotated around the workpiece rotation axis 3 at a set rotation speed based on a preset polishing target value, and is rotated at the set rotation speed. The spherical polisher 6 is pressed from the normal direction of the axisymmetric aspherical surface 1 and scanned in the meridian direction, and the relative polishing removal motion is given by the attitude control of XYθ to uniformly polish the axisymmetric aspherical surface 1. The entire surface is polished so that the removal amount is obtained.

In the shape measuring step (S02) of the axially symmetric aspherical surface 1, the shape of the axially symmetric aspherical surface 1 after uniform polishing is measured, and the polishing removal amount is compared with the polishing target value used in the uniform polishing step (S01). To grasp.
As a result, whether the removal amount of polishing tends to be excessive or insufficient from the rotation center axis C to the peripheral edge of the axisymmetric aspherical surface 1 with respect to the polishing target value of the axisymmetric aspherical surface 1 before polishing, It is determined whether or not the tendency of time is linear.

  In the modified polishing step (S03), the above-described tendency of the polishing removal amount from a linear function for calculating the polishing removal amount of the axisymmetric aspherical surface 1 from the rotational speed of the axisymmetric aspherical surface 1 and the rotation speed of the polisher 6. Step (S03-1) representing the first approximate expression, and the second approximate expression having a linear inclination that is a direction to eliminate the excess tendency or the insufficient tendency of the polishing removal amount from the function with respect to the first approximate expression. A step of calculating (approximate equation) (S03-2), and a step of back-calculating the rotational speed of the axisymmetric aspherical surface 1 and the rotational speed of the polisher 6 from the second approximate expression to create a corrected polishing target value ( S03-3) and a step of actual polishing (S03-4) based on the corrected polishing target value are performed.

  Here, the above-mentioned function is defined such that the rotational speed of the axisymmetric aspherical surface 1 and the rotational speed of the polisher 6 at the polishing target value before correction are Nwo and Npo, respectively, and the axially symmetric aspherical surface 1 at the corrected polishing target value is obtained. The number of rotations and the number of rotations of the polisher 6 are Nwi and Npi, respectively. At this time, as a function described above, when Npi / Nwi is smaller than Npo / Nwo, the polishing removal amount is gradually increased from the vicinity of the rotation center axis C of the axisymmetric aspherical surface 1 toward the peripheral portion, and Npi / Nwi is When it is larger than Npo / Nwo, it is based on the following formula (1), which has a tendency to gradually reduce the polishing removal amount from the vicinity of the rotation center axis C of the axisymmetric aspherical surface 1 toward the peripheral edge.

  Here, Dp is the amount of polishing removal, r is the distance from the central axis C of the rotation axis to the position where the polisher 6 is in contact with the axisymmetric aspherical surface 1, Δδ is the polishing spread range of the polisher 6, ie, experiments and past The diameter of the polishing mark calculated from the processing result is shown.

  Further, h represents the polishing removal volume according to the Preston equation developed as in Equation (2).

  Here, k is a coefficient obtained from experiments and past processing results, p is a polishing pressing force, v is a relative speed at the processing point of the polisher 6 with respect to the axisymmetric aspherical surface 1, and Δt is a dwell time of the polisher 6 (∝1 / Feed speed). The relative speed (v) is expressed by the formula (3).

  Here, Rp is the outer diameter of the polisher 6, Rw is the distance from the rotation axis central axis C to the position where the polisher 6 is in contact with the axisymmetric aspherical surface 1, Np is the rotational speed of the polisher 6, and Nw is the aspherical workpiece 2 indicates the number of rotations.

Next, the operation and effect of the axisymmetric aspherical polishing method based on the above-described polishing process will be described.
First, for example, assuming that an axisymmetric aspherical surface 1 as shown in FIG. 3 is obtained by grinding, a uniform polishing step (S01) is performed based on a predetermined polishing target value.

Then, it transfers to a shape measurement process (S02) and suppose that the shape measurement result of the surface of the axisymmetric aspherical surface 1 as shown in FIG. 4 was obtained, for example.
This shape measurement result is compared with the shape measurement result before the polishing process to compare whether the polishing removal amount of the axisymmetric aspherical surface 1 tends to be excessive or insufficient from the vicinity of the rotation center axis C to the periphery.

  Here, with respect to the shape accuracy before polishing, the polishing removal amount on the peripheral edge side has a linear gradient more than the vicinity of the rotation center axis C, indicating a tendency of deficiency. Therefore, in order to equalize the entire polishing removal amount of the axisymmetric aspherical surface 1, the ratio of the rotational speed of the aspherical workpiece 2 during polishing: Nwo and the rotational speed of the polisher 6: Npo is adjusted to From the vicinity of the rotation center axis C of the symmetric aspherical surface 1 toward the periphery, the tendency of the polishing removal amount tends to increase more than the state before polishing.

Moving to the modified polishing step (S03), in the step (S03-1) in which the shape measurement result is expressed by a linear first approximate expression, first, a linear first approximate expression not showing the polishing tendency shown in FIG. Approximate as
Next, in the step of calculating the second approximate expression (S03-2), a linear second approximate expression A obtained by inverting the slope of the first approximate expression is calculated by a computer, and as shown in FIG. Display a graph.

Then, in the step of creating the corrected polishing target value (S03-3), when the rotational speed of the aspherical workpiece 2 after correction: Nwi and the rotational speed of the polisher 6 after correction: Npi are variables, Npi and Nwi for realizing Npi / Nwi <Npo / Nwo are obtained from the second approximate expression A.
That is, from the viewpoint of whether Nwi is larger than Nwo, Npi is smaller than Npo, or both, until the second approximate expression A shown in the graph and Expression (1) match , Nwi and Npi are repeatedly applied to equation (1). As a result, the rotational speed Nwi and polisher rotational speed Npi of the aspherical workpiece 2 when the formula (1) and the second approximate expression A coincide with each other are obtained.

Subsequently, the process proceeds to an actual polishing step (S03-4), and polishing is performed based on Nwi and Npi obtained as described above as corrected polishing target values.
As a result, in the polishing target value before correction, the polishing removal amount tends to be deficient in the peripheral portion of the axisymmetric aspherical surface 1 than in the vicinity of the rotation center axis C. The target value tends to increase, and acts to maintain an even polishing removal amount over the entire surface of the axisymmetric aspherical surface 1.

  In this way, the entire surface of the axisymmetric aspherical surface 1 is again polished with a uniform removal polishing amount and processed into a surface property (skin roughness) having a good optical function surface (mirror surface) while maintaining the shape accuracy. Then, the polishing of the axisymmetric aspherical surface 1 (polishing of the entire optical surface) is completed.

  According to this axisymmetric aspherical polishing method, the residence time and angle of the polisher 6 with respect to the axisymmetric aspherical surface 1 can be changed by changing the ratio of the rotational speed of the aspherical workpiece 2 and the rotational speed of the polisher 6. In addition, the polishing removal amount can be changed according to the distance from the rotation center axis C, and the polishing target value can be corrected. Therefore, the polishing target value can be simply corrected in a short time and polished, and the axisymmetric aspherical surface 1 can be made a good optical surface.

  At this time, when the shape measurement result of the axisymmetric aspherical surface 1 before polishing is compared with the shape measurement result after polishing, the polishing removal amount changes linearly from the rotation center axis C to the peripheral edge. By replacing the change state with the linear first approximate expression, the second approximate expression A that reverses the change in the polishing removal amount can be calculated. Then, the rotational speed of the aspherical workpiece 2 and the rotational speed of the polisher 6 to be corrected can be easily calculated from the second approximate expression A.

In particular, since a function based on Preston's equation often used in polishing-related simulations is used when adjusting the polishing removal amount, it can be applied without any discomfort when creating NC or CNC data.
Further, the adjustment using only the rotational speed of the aspherical work 2 can also reduce the influence on the kinks (unevenness) generated at the center of the axisymmetric aspherical surface 1.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  Based on the above embodiment, the rotational speed (Nwo) of the aspherical workpiece 2 is 200 times / minute, the diameter (D) of the polisher 6 is 5 mm, the rotational speed (Npo) is 150 times / minute, Polishing was actually performed with the polishing pressing force (P) on the spherical surface 1 being 1N.

First, a uniform polishing step (S01) was performed based on a predetermined polishing target value. And it moved to the shape measurement process (S02), and obtained the measurement result as shown in FIG. As a result, it has been found that the polishing removal amount at the peripheral portion tends to be insufficient compared to the vicinity of the rotation center axis C. Therefore, it is necessary to increase the polishing removal amount at the peripheral portion, and the correction polishing step (S03) is performed. did. At this time, by calculating the second approximate expression A as shown in FIG. 5 from the first approximate expression (not shown) and using this, it is possible to prevent the deviation of the polishing removal amount of the axisymmetric aspherical surface 1 from being increased. Judge. From the formula (1) corresponding to the second approximate formula A, as the corrected grinding target value, the rotational speed (Nwi) of the workpiece rotating shaft 3 is 240 times / minute, and the rotational speed (Npi) of the polisher 6 is 120. The condition of times / minute was obtained.
Thus, when it grind | polished actually using the grinding | polishing processing target value after this correction | amendment, the shape measurement result as shown in FIG. 6 was obtained.

  For the axisymmetric aspherical surface 1 having a shape measurement result as shown in FIG. 7, the rotational speed (Nwo) of the aspherical workpiece 2 is 200 times / minute and the diameter of the polisher 6 ( Polishing was actually performed with D) being 5 mm, the rotation speed (Npo) being 150 times / minute, and the polishing pressing force (P) of the polisher 6 against the axisymmetric aspherical surface 1 being 1 N.

First, a uniform polishing step (S01) was performed based on a predetermined polishing processing target value, and the process moved to a shape measurement step (S02) to obtain a measurement result as shown in FIG.
Also in the present Example 2, since the polishing removal amount at the peripheral edge portion showed a tendency of being deficient as compared with the vicinity of the rotation center axis C, the correction polishing step (S03) was performed, and the first approximate expression (not shown) is shown in FIG. Such a second approximate expression B is calculated. From this second approximate expression B, after determining that the polishing removal amount of the axisymmetric aspherical surface 1 can be changed, the number of rotations (Nwi) of the workpiece rotation shaft 3 is 280 times as the corrected polishing target value. / Min, and the number of revolutions (Npi) of the polisher 6 was 150 times / min.
Thus, when it grind | polished actually using this grinding | polishing target value after correction | amendment, the shape measurement result as shown in FIG. 10 was obtained.

  For the axisymmetric aspherical surface 1 having a shape measurement result as shown in FIG. 11, the rotational speed (Nwo) of the aspherical workpiece 2 is 200 times / minute and the diameter of the polisher 6 ( Polishing was actually performed with D) being 5 mm, the rotation speed (Npo) being 150 times / minute, and the polishing pressing force (P) of the polisher 6 against the axisymmetric aspherical surface 1 being 1 N.

First, a uniform polishing step (S01) is performed based on a predetermined polishing target value, and then the shape measurement step (S02) is performed. Unlike the above embodiment, as shown in FIG. The measurement result which shows that the polishing removal amount tends to be excessive at the peripheral portion was obtained.
In this case, when the rotational speed of the aspherical work 2 after correction is Nwi and the rotational speed of the polished polisher 6 is Npi, Npi / Nwi> Npo / Nwo, so that the axisymmetric aspherical surface 1 The adjustment policy is determined so that the tendency of the polishing removal amount decreases from the vicinity of the rotation center axis C toward the peripheral edge as compared with the state before polishing.

  Then, the process proceeds to the modified polishing step (S03). Here, in order to obtain a polishing removal amount with a minimum shape error on the entire optical surface after polishing, the polishing removal amount in the peripheral portion is more actively reduced than in the vicinity of the rotation center axis C. That is, in the step (S03-1) represented by the first approximate expression, the shape measurement result is not applied as it is, but the peripheral portion tends to have a larger amount of polishing removal than the actual result. An approximate expression was calculated. Based on this first approximate expression, in the step of calculating the second approximate expression (S03-2), the second approximation (not shown) showing a tendency that the polishing removal amount tends to be excessively insufficient in the peripheral portion than in the vicinity of the central axis C. The formula was calculated.

From this second approximate expression, the corrected target values for polishing were obtained such that the rotational speed (Nwi) of the workpiece rotating shaft 3 was 120 times / minute and the rotational speed (Npi) of the polisher 6 was 180 times / minute. .
Thus, when actual polishing was performed using the corrected polishing target value, as shown in FIG. 13, a shape measurement result was obtained that resulted in a polishing result with a minimum shape error over the entire axisymmetric aspheric surface.

It is explanatory drawing which shows the grinding | polishing state of the axially symmetric aspherical surface in the axially symmetric aspherical surface polishing method which concerns on one Embodiment of this invention. It is a flow figure showing an axisymmetric aspherical surface polishing method concerning one embodiment of the present invention. 4 is a graph showing a shape measurement result of an axisymmetric aspheric surface after grinding in Example 1. 6 is a graph showing the shape measurement result of an axially symmetric aspherical surface after uniform polishing in Example 1. 6 is a graph showing a second approximation formula in Example 1. 6 is a graph showing a shape measurement result of an axisymmetric aspheric surface after correction polishing in Example 1. It is a graph which shows the shape measurement result of the axisymmetric aspherical surface after grinding in Example 2. 6 is a graph showing a shape measurement result of an axially symmetric aspherical surface after uniform polishing in Example 2. 10 is a graph showing a second approximation formula in Example 2. It is a graph which shows the shape measurement result of the axisymmetric aspherical surface after the correction grinding | polishing in Example 2. FIG. 10 is a graph showing a shape measurement result of an axisymmetric aspherical surface after grinding in Example 3. 10 is a graph showing the shape measurement result of an axially symmetric aspherical surface after uniform polishing in Example 3. 10 is a graph showing a shape measurement result of an axisymmetric aspheric surface after correction polishing in Example 3.

Explanation of symbols

1 Axisymmetric aspherical surface 6 Polisher C Rotation center axis

Claims (4)

The axisymmetric aspheric surface after grinding is rotated around the axis of rotation of the axisymmetric aspheric surface, the rotating spherical polisher is pressed from the normal direction of the axisymmetric aspheric surface, and scanned in the meridian direction. In the axially symmetric aspherical polishing method for polishing the entire axially symmetric aspherical surface,
An axially symmetric aspherical surface comprising a modified polishing step of performing polishing by changing the ratio of the rotational speed of the axially symmetric aspherical surface and the rotational speed of the polisher after the entire polishing of the axially symmetric aspherical surface Polishing method. When the polishing removal amount tends to be excessive or insufficient linearly from the rotation center axis to the peripheral edge of the axisymmetric aspheric surface with respect to the target processing value of the axisymmetric aspheric surface before polishing, the corrected polishing The process is
From a linear function for calculating the polishing removal amount from the rotational speed of the axisymmetric aspheric surface and the rotational speed of the polisher, a linear inclination in a direction to eliminate the excessive tendency or the insufficient tendency of the polishing removal amount is obtained. Calculating an approximate expression having:
The shaft according to claim 1, further comprising a step of reversely calculating the rotational speed of the axisymmetric aspherical surface and the rotational speed of the polisher from the approximate expression to create a corrected polishing target value. Symmetric aspheric polishing method. The rotation speed of the axisymmetric aspherical surface and the rotation speed of the polisher at the polishing target value before correction are set to Nwo and Npo, respectively, and the rotation speed of the axisymmetric aspherical surface and the rotation of the polisher at the corrected polishing target value are set. When the numbers are Nwi and Npi respectively,
The function is
When Npi / Nwi is smaller than Npo / Nwo, the polishing removal amount is gradually increased from the vicinity of the rotation center axis of the axisymmetric aspheric surface toward the peripheral portion,
3. When Npi / Nwi is larger than Npo / Nwo, there is a tendency that the polishing removal amount gradually decreases from the vicinity of the rotation center axis of the axisymmetric aspheric surface toward the peripheral portion. Axisymmetric aspheric polishing method. 3. The axisymmetric aspherical polishing method according to claim 2, wherein the function uses a Preston equation.

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