JPH09253977A - Method for forming shape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a moving path of a machining means to be easily attained without performing any complex calculation. SOLUTION: An outer shape P of a sectional surface 3 of a part to be processed when a part C to be processed is sliced into a specifies thickness (d) is calculated for every sectional surface 3. A plane L passing through the outer shape P of the sectional surface 3 and perpendicular to the sectional surface 3 is set, thereby the outer shape is constructed by the sectional surface 3 and the plane L, and a cubic body S contacted at its inner side with the part C to processed is set. A processing means smaller than a processing area of the sectional surface 3 is scanned at the position S of the cubic body so as to remove each of the layers S1, S2... constituting the cubic body S, thereby the item to be processed is processed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a camera, a microscope,
The present invention relates to a lens used for an optical product such as a semiconductor manufacturing device, and a shape creating method for manufacturing a high-precision mold having a free curved surface.

[0002]

2. Description of the Related Art A glass lens is mainly used for an optical system of an optical product such as a camera, a microscope, and a semiconductor manufacturing apparatus. The conventional glass lens manufacturing process includes the following four processes.

(1) Pressing step: a step of forming a glass block by press-forming from molten glass.

(2) Grinding step: a step of manufacturing a rough surface lens having a desired curvature by grinding a glass block with a grinding machine.

(3) Smoothing step: a step of removing scratches and crack layers on the surface of the rough surface lens by interlocking a metal dish on which diamond pellets are attached on the rough surface lens. However, instead of the diamond pellets, abrasive grains having a large grain size may be supplied between the metal dish and the rough surface lens for processing. Also called sanding process.

(4) Polishing process: Using a polishing polisher,
By further polishing the rough lens obtained in the above step, while further removing the scratch and crack layers,
(1) to (3) are steps of correcting the shape error that has occurred.

In the case of manufacturing a spherical lens, a curve generator is used in the grinding step (2), and the grinding wheel is worked along the arc of the desired lens curvature for processing. Further, in the smoothing step (3), the metal dish having the target lens curvature is rocked on the lens to be processed for processing. Further, in the polishing step (4), a substance softer than glass is attached to a metal dish having a desired curvature, and processing is performed while supplying a polishing liquid in which abrasive grains are dispersed in water.

Incidentally, as the lens, there is an aspherical lens in addition to the spherical lens. This aspherical lens is important because it has excellent performance that cannot be obtained with a spherical lens. The method of processing an aspherical lens differs from the above-mentioned spherical lens in the following points.

First, in the grinding step (2), a spherical lens having a target radius of curvature of an aspherical lens is processed by a curve generator or the like. Then, this spherical lens is processed into an aspherical shape by using an NC controlled polishing machine.

In the polishing step (4), the shape error generated in the previous step is corrected, and the scratch and crack layers are removed. This process is small tool polishing,
Alternatively, uniform polishing and small tool polishing are used together.

Here, the small tool polishing is a method in which a polisher having a diameter smaller than the lens diameter is NC-controlled to be moved along an aspherical surface and polished. Uniform polishing refers to polishing while pressing a soft polisher having a sufficiently larger area than the lens diameter against the lens.

Since a small-diameter polishing pad is used in the small tool polishing, it is possible to accurately correct the shape error of a specific portion on the surface of the lens. On the other hand, the processing time is slow. On the other hand, in the uniform polishing, since the entire surface of the lens is polished at once, the scratch and crack layers can be removed relatively quickly, but the shape cannot be corrected. Further, depending on the uniform polishing, the shape error generated in the step (2) of NC grinding may be further increased. For this reason, it is general to perform small tool polishing after the uniform polishing to correct a shape error.

In the method of processing an aspherical lens, a smoothing step may be included between the grinding step and the polishing step. This is a method almost similar to the small tool polishing, but since it is processed by using abrasive grains having a large grain size, high-speed processing is possible. However, the shape accuracy as high as that of the small tool polishing cannot be obtained.

In the formation correction by the small tool polishing described above, the amount e (x, y) to be processed (referred to as required removal amount) is as follows by measuring the shape accuracy of the lens to be processed by a shape measuring machine. Required to. If the shape of the lens to be processed is p (x, y) and the shape of the lens design value is q (x, y), the required removal amount e (x, y) is p
Subtract q (x, y) from (x, y) and make a correction coefficient a so that this value does not become negative at any point (x, y).
Is the value added. That is, e (x, y) can be expressed as e (x, y) = p (x, y) -q (x, y) + a (1). Therefore, in order to obtain the shape according to the design value, at the point (x, y) of the lens to be processed, the point (x , Y) causes the polisher to stay for a predetermined time. Further, the polisher is made to scan and stay up to the next point. In small tool polishing, the amount to be processed correlates with the dwell time of the polisher on the lens to be processed. That is, in the process of scanning the polisher on the work surface, the required removal amount e (x,
y) so that the polisher stays for a long time in a large area,
By controlling the scanning of the polisher, it is possible to reduce the shape error.

Conventionally, the determination of the stay time and the scanning path as described above requires a complicated calculation as described below.

First, when the polisher is allowed to stay for a time g (x, y) at an arbitrary point (x, y) on the workpiece and is rotated and machined, the machining amount distribution is f (x, y). , The processing amount h (x, y) in this case, the stay time g (x,
The relation between y) and f (x, y) can be expressed by the convolution operation shown in the following equation.

[0017]

[Equation 1]

Therefore, the optimum residence time distribution of the polisher for removing the required removal amount e (x) can be obtained from the equation (2). That is, e (x,
y),

[0019]

[Equation 2]

## EQU1 ## G (x, y) that satisfies the expression (3)
Is the dwell time of the polisher for correcting the shape error by processing e (x). Therefore, obtaining the residence time distribution that eliminates the shape error means obtaining g (x, y) from the equation (3). In order to obtain the staying time g (u, v) from the equation (3) (deconvolution calculation), Fourier transform is performed on both sides of the equation (3). E (ωx, ωy) = G (ωx, ωy) · F ( ωx, ωy) (4) where E (ωx, ωy), G (ωx, ωy), F (ω
x, ωy) is e (x, y), g (x, y), f
It represents the Fourier transform of (x, y). From equation (3), G
(X, y) is G (ωx, ωy) = E (ωx, ωy) / F (ωx, ωy) (5) Further, when the equation (5) is inverse Fourier transformed, the shape error e ( dwell time to remove x, y) is required. Here, the symbol F ⁻¹ represents the inverse Fourier transform.

G (x, y) = F ⁻¹ (E (ωx, ωy) / F (ωx, ωy)) (6) Further, the scanning path of the polisher is based on the stay time obtained from the equation (6). I had to decide.

[0022]

The calculation of the staying time for removing the shape error by the small tool polishing requires the extremely complicated calculation as described above, and the calculation also requires a long time. .

When F (ωx, ωy) is very small, the right side of the equation (6) diverges, and the stay time g (x,
It was difficult to ask for y).

Further, the staying time t thus obtained
Finding the optimum polisher scanning path from (x, y) also requires a very complicated calculation.

Such a problem is not limited to the above-described small tool polishing, but also a processing method in which the processing amount is a function of the processing time, for example, ion beam processing, plasma CV.
M (Chemical Vaporization M)
This occurs in common when performing shape creation processing using aching, etc.

An object of the present invention is to provide a shape creating method capable of easily obtaining a moving path of a processing means.

[0027]

In order to achieve the above object, the present invention provides the following shape creating method.

That is, the shape of the portion to be machined of the workpiece is obtained by obtaining the difference between the shape of the workpiece measured in advance and the target shape of the workpiece to be determined in advance, and the portion to be processed is obtained. , The coordinates of the outline of a plurality of cross sections formed in the portion to be processed when sliced at a predetermined interval smaller than the height value of the highest portion of the portion to be processed, the cross section For each cross-section, a machining means having a machining area whose width is smaller than that of the cross-section and whose machining amount is equal to the thickness when moved at a predetermined speed is provided in the coordinate position. Is a method of forming a shape by processing the workpiece by scanning at the above speed.

In this shape creating method, a plurality of cross sections formed when the portion to be processed of the workpiece is sliced at a predetermined interval is set to the portion to be processed of the workpiece. The processing means is scanned at a constant speed within the coordinates of the cross section. By repeating this for all the cross sections, the layers between the cross sections are sequentially removed from the top. In this method, processing errors occur at the edges of each layer,
Since the processing error is not added in the height direction, the height of the processing error that occurs is smaller than the value of the sliced interval. Therefore, it is possible to reduce the shape error of the workpiece before processing. Further, by setting the value of the above-mentioned slicing interval to a value smaller than the target shape accuracy, it is possible to process the shape error after processing to be less than the target shape accuracy.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the shape creating method of the present invention will be described below.

The present invention is a shape creating method for manufacturing an article in which a shape error is equal to or less than a target accuracy by processing a workpiece. First, the outline will be described.

The error shape of the workpiece 1 before machining is represented by the difference between the shape of the workpiece 1 before machining and the target shape 2 as shown in FIG. The function representing this error shape is defined by the error curved surface C
Call. The shape of the workpiece 1 before being processed can be measured by, for example, an interferometer, a three-dimensional measuring machine, or the like. This error shape is the part to be removed by processing.

In the present invention, as shown in FIG.
By moving in the axial direction, the outer shape of the cross section 3 of the error shape when the error shape is sliced on a plane is obtained.
The slicing interval is a predetermined constant interval d. In FIG. 2, the error shape is sliced by a plane, but an arbitrary curved surface such as a spherical surface may be used.

The outer shape of the cross section 3 is represented by a ring-shaped curve P, and the curve P is obtained by finding the line of intersection between the error curved surface C and the sliced plane.

Further, a plane L passing through the obtained contour P of the cross section 3 and perpendicular to the cross section 3 is obtained. In FIG. 2, plane L
Is parallel to the z-axis.

Here, the solids surrounded by the cross section 3 and the plane L are defined as Si (i = 1, 2, 3, ...). Solid S, which is a stack of all solids Si (hatched part in FIG. 3)
Is inscribed in the error curved surface C. The error shape after processing when the solid S is removed is calculated from the error curved surface C to the solid S.
The error curved surface C ′ shown in FIG. 4 is obtained. As shown in FIG. 7, the height of the error curved surface C ′ is equal to or less than the interval d when sliced in FIG. Therefore, when slicing in FIG. 2, by setting the interval d to be equal to or less than the target accuracy ε, it is possible to obtain an article whose shape error is equal to or less than the target accuracy ε.

Therefore, as the movement path of the processing means, the movement path for removing the solid S may be obtained. Solid S
Since the end portion is perpendicular to the main plane, the movement path of the processing means can be easily obtained. For example, since the solid S is a stack of solid Si, a method of removing solid Si in order from the top can be used. Specifically, a constant processing amount (depth) when moved at a constant speed
By using the processing means that obtains, the moving path for scanning at a constant speed within the coordinates of the cross section 3 is obtained. Further, for example, by using a processing means in which the staying time and the processing amount are correlated, the staying time of the processing means is correlated with the height of the solid S in the z direction to obtain xy.
Find the movement path to move in the plane.

By moving the processing means on the workpiece along the movement path thus obtained, it is possible to obtain an article having a shape error equal to or less than the target accuracy as shown in FIG.

In the present invention, the processing means has a processing area smaller than that of the cross section 3 when it is made to stay at one place without being moved. For example, a small tool polishing method, an ion beam processing method, plasma CVM, or the like can be used. In the small tool polishing method, since the processing area corresponds to the area of the polisher, a tool having a polisher diameter smaller than the cross section 3 is used. Further, in the ion beam method, since the beam diameter corresponds to the processing area, the beam diameter is converged and used so as to be smaller than the cross section 3. Further, in the plasma CVM, since the diameter of the electrode for generating plasma corresponds to the processing area, the electrode in which the diameter of the portion where plasma is generated is smaller than the cross section 3 is used.

In all of the small tool polishing method, the ion beam method and the plasma CVM, there is a correlation between the residence time of the processing means and the processing amount, and when the processing means is moved at a constant speed. A constant processing depth can be obtained.

The above-mentioned shape creating method will be described in more detail below. Here, scan the processing means,
A case will be described in which the moving path of the processing means for processing each solid Si of the solid S in FIG. 2 in order from the top is obtained.

In order to remove the solid body having the thickness d shown in FIG. 2 by the scanning of the processing means, it is necessary to previously obtain the scanning speed v and the scanning pitch Δm which are the scanning conditions of the processing means. Therefore, this scanning condition is obtained in advance according to each step of FIG.

First, as shown in FIG. 5, the machining amount (machining depth) d when the machining means is scanned on the workpiece at an appropriate speed v and a scanning pitch Δm is calculated or experimented (step 601, 602).

In the case of obtaining by calculation, the shape of the machining mark (hereinafter referred to as the static machining mark shape) when the machining means and the workpiece are machined in a state where they are relatively stationary for a certain period of time is previously obtained by an experiment. This is used as data.

The processing amount d becomes equal to or less than the desired target accuracy ε (step 603), and furthermore, no waviness occurs in the processed shape (that is, the scanned plane is uniformly processed) (step 604). The scanning pitch Δm and the scanning speed v are changed little by little until the above condition is satisfied (step 605), and the calculation or experiment of the processed shape and the processed amount d is repeated.

In steps 601 to 605, the scanning pitch Δ that satisfies the conditions of steps 603 and 604.
When m and the scanning speed v cannot be obtained, the machining conditions are changed to obtain the static machining trace shape again, and the step 6 is performed again.
Perform 01-605 calculations or experiments. The processing conditions include polishing pressure, abrasive grain size, etc. in the small tool polishing method, and input power, reaction gas concentration, reaction gas flow rate, gap length, etc. in plasma CVM.

As a result, the scanning pitch Δm, the scanning speed v,
And the processing amount d at that time is obtained.

Next, the following calculation for obtaining the movement path of the processing means is performed. This calculation can be executed by causing a calculation device to calculate a program as shown in FIG. 7. The program is stored in a storage device or the like in advance, and data required for calculation is input from the outside.

First, in steps 701 and 702, the calculation unit calculates the shape data of the workpiece and the target shape data, and the scanning pitch Δm of the processing means obtained as described above.
The processing amount d is received from the outside. Then, the difference between the shape data of the workpiece and the target shape data is obtained to obtain the error curved surface C representing the shape (error shape) to be processed (step 703).

Next, in step 704, a curve representing the outer shape of the cross section when the shape to be processed (error shape) is sliced on the plane at intervals d from the top is obtained. The normal direction of the plane is set in advance. Here, the plane is defined as parallel to the main plane (xy plane) of the target shape. Specifically, the curve Pi (where i = 1, 2, 3, ...) Is obtained by finding the line of intersection between the obtained error curved surface C and the plane (here, represented by z = i · d). Is calculated (FIGS. 8 and 9). i represents the outer shape of the i-th section from the top. The slice interval d is determined in step 702.
The value is equal to the processing amount d received in. Here, the shape to be processed is sliced by a plane, but a curved surface may be used.

Next, in step 705, a straight line T (here, y = k · Δm, k = 1, 2 ,, on the plane (xy plane) on which the curve Pi exists, with an interval Δm, as shown in FIG.
3 ...), the two intersection points P of the two
^k _{i, 1} (x ^k _{i, 1} , y ^k _{i, 1} , z ^k _{i, 1} ), P ^k _{i, 2} (x ^k _{i, 2} , y
The coordinates of ^k _{i, 2} , z ^k _{i, 2} ) are obtained for all straight lines T. Further, where P ^k _{i, 1} of 1 and P ^k _{i, 2} of 2 shows how the intersection of either end of the straight line T. Δm is the value of the scanning pitch accepted in step 702.

After the steps 704 and 705 are performed for all the cross-sections when the shape to be processed is sliced (step 706), the moving path data of the processing means is output at step 707. Specifically, as shown below, P
^k _{i, 1} (x ^k _{i, 1} , y ^k _{i, 1} , z ^k _{i, 1} ), P ^k _{i, 2} (x ^k _{i, 2} , y
^The paths in which the coordinate data of ^k _{i, 2} , z ^k _{i, 2} ) are connected in numerical order of k are sequentially output to the driving device of the processing means in accordance with the movement of the processing means.

P ¹ _{i, 1} → P ¹ _{i, 2} P ¹ _{i, 2} → P ² _{i, 2} P ² _{i, 2} → P ² _{i, 1} P ² _{i, 1} → P ³ _{i, 1} P ³ _{i , 1} → P ³ _{i, 2} P ³ _{i, 2} → P ⁴ _{i, 2}・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ P ^k-1 _{i, 1} → P ^k _{i, 1} P ^k _{i, 1} → P ^k _{i, 2 Further} , the speed v obtained in steps 601 to 605 is set as the moving speed of the processing means in the driving means of the processing means. The driving means, according to the received NC data,
The processing means is moved at the speed v. In addition, step 601
The processing conditions (e.g., electric power, reaction gas concentration, reaction gas flow rate, gap length) used in steps 605 to 605 are also set.

As a result, the machining means is surrounded by the curves P ₁ , P ₂ , P ₃ ... P _i ... Of the portion (error shape) of the workpiece to be machined, as shown in FIG. Within the part,
Scanning is performed at the scanning pitch Δm. As a result, the portions indicated by the solids S ₁ , S ₂ , S ₃ ... In FIG. 3 are sequentially removed,
The target shape can be obtained within the shape accuracy d.

Since the operations shown in the above steps 701 to 707 can be easily performed by using a personal computer or the like, the route of the processing means can be easily set without performing complicated calculation as in the conventional case. Can ask,
High precision processing is possible.

As described above, there are two main reasons why the path of the processing means can be easily obtained in the present embodiment. The first reason is that in the present embodiment, a method of approximating the shape (error shape) to be processed into a solid S in which layers are stacked in a step shape is used. Also, the second
The reason is that in the present embodiment, since the processing means is moved so as to remove the approximate solids one by one, it is possible to scan the processing means at a constant speed.

The second reason will be further described. In general, the processing method has a property that the processing speed (processing amount per unit time) is gradually changed with the passage of time when the processing means is allowed to stay in one place.
For example, in plasma CVM and small tool polishing, the processing speed and the passage of time have such a relationship. In order to perform shape creation by using such a processing means while changing the staying time of the processing means at the processing point as in the prior art, it is necessary to grasp the relationship between the processing amount and the staying time in advance. It was Then, using this relationship, it is necessary to calculate the staying time required to obtain the target processing amount when the processing means is stayed on the curved surface. for that reason,
The calculation was complicated. However, in the present invention,
Since the shape to be processed is approximated by the step-like solid S and layers having a constant thickness are removed one by one, the processing means may be moved at a constant speed. Therefore, it is not necessary to grasp the relationship between the stay time and the processing speed in advance, and the movement route can be easily obtained.

In this embodiment, the method of scanning at a constant speed when moving the processing means is used, but the present invention is not limited to this method, and the processing means is allowed to stay at one place. It is also possible to use a method of processing. Even in this case, in the present embodiment, the shape (error shape) to be processed is approximated by the step-shaped solid S, and therefore the amount to be processed at a certain point is the layer stack of layers at that point of the solid S. It is represented by a number (height of the solid S). Therefore, by grasping the relationship between the processing amount and the stay time in advance, the stay time can be calculated more easily than before.

Further, in the above-mentioned present embodiment, as shown in FIG. 11, the scanning directions of the processing means are the same in the layers P ₁ , P _2, ..., However, as shown in FIG. It is also possible to set different directions for each. This is because, depending on the processing means, extremely minute scratches may occur in the scanning direction of the processing means. In this case, when the processing means is scanned in the same direction for each layer, minute scratches are also generated in the same direction, which may deteriorate the performance of the optical component. Also, even if the scratches are shallow one by one, the scratches in the same direction will overlap,
It is possible that the wound will eventually deepen. Therefore, as shown in FIG. 5, by changing the scanning direction of the processing means in at least one of the layers, the directions of the scratches can be randomized and the scratches can be kept shallow. It can be prevented from lowering. Specifically, the direction of the straight line T set in step 705 of FIG.
It can be realized by setting different directions in at least one of P ₁ , P ₂ ...

In the above embodiment, the case where the portion to be processed is sliced by a plane has been described. However, when the target shape is a curved surface such as a spherical lens, the portion to be processed is a curved surface such as a spherical surface. It can be configured to slice with. In this case, in step 704 of FIG. 7, for example, the error curved surface C is a spherical surface parallel to the spherical surface of the target shape.
A curve P when sliced is obtained. The interval between the spheres to be sliced is d, as in the case of the plane. Then, in step 707, P ^k _{i, 1} (x ^k _{i, 1} , y ^k _{i, 1} , z ^k _{i, 1} ),
Setting a plurality of points q (x, y, z) at predetermined intervals on the movement path between P ^k _{i, 2} (x ^k _{i, 2} , y ^k _{i, 2} , z ^k _{i, 2} ), The xyz coordinates are calculated so that this point q (x, y, z) is located on the sphere when sliced. Then, P ^k _{i, 1} (x ^k _{i, 1} , y ^k _{i, 1} , z ^k _{i, 1} ), P ^k _{i, 1}
^A plurality of points q (x, x, between ^k _{i, 2} (x ^k _{i, 2} , y ^k _{i, 2} , z ^k _{i, 2} )
The configuration is such that y, z) coordinates are output. Thus, the tip of the processing means can be configured to scan the workpiece along the spherical surface when sliced.

Further, in the above embodiment, in step 705 of FIG. 7, P ^k _{i, 1} (x ^k _{i, 1} , y ^k _{i, 1} ,
xyz of z ^k _{i, 1} ), P ^k _{i, 2} (x ^k _{i, 2} , y ^k _{i, 2} , z ^k _{i, 2} )
Each coordinate is calculated. However, the plasma CVM is used as the processing means, and the plasma C
When the value of the gap length between the electrode of the VM and the work piece is larger than the height value of the highest portion of the work piece to be machined, the value of the machining means in the z direction is kept constant. It is possible to process all the parts to be processed by keeping the value of. That is, the surface on which the processing means is scanned is P ₁ ,
The areas P ₂ , P _3, ... Can be made to be on the same plane. In that case, in step 705, xy coordinates, P ^k _{i, 1} (x ^k _{i, 1} , y ^k _{i, 1} ), P ^k _{i, 2} (x ^k _{i, 2} , y ^k
Only _{i, 2} ) is calculated, and as the z coordinate, one of the planes passing through P ₁ , P ₂ , P ₃ ... Is selected, and the value of the z coordinate of this plane is used. When a spherical surface is used as the slicing surface, one of the spherical surfaces passing through P ₁ , P ₂ , P _3, ... Is selected, and P ₁ , P ₂ ,
When scanning the area P _3, ..., The processing means can be controlled so as to be along the selected spherical surface. In the case of such a configuration, the calculation of the z coordinate is simplified, so that the calculation time can be shortened and the processed shape similar to the case where the z coordinate is controlled can be obtained.

[0062] In the case of processing by such a processing means along a same plane scanning each region of _{P 1, P 2, P 3} ··· is, P _1, P _2, P _The order of scanning the areas ₃ ... Does not necessarily have to be the order of P ₁ , P ₂ , P ₃ ... For example, of the order and _{··· P 3, P 2, P} 1,
··· P _3, P _1, be scanned in the order of _{P 2, P 1, P 2} , P 3
It is possible to obtain the same processed shape as when scanning in the order of.

[0063]

EXAMPLE An example in which the shape creating method provided by the present invention is applied to a lens processing apparatus using plasma CVM will be described below.

The principle and apparatus of the plasma CVM are described in Japanese Patent Laid-Open No.
-125829 and "Mori et al., Proceedings of the Japan Society for Precision Engineering, Spring Conference Academic Lectures, P. 637, 1992 ".

The main components of the lens processing apparatus using the plasma CVM are, as shown in FIG. 13, a chamber 9, a positioning unit 6, an electrode 52, a tilting unit 8, a power supply system 53, a gas supply system 4, and a gas exhaust system 5. , Control system 7. Each component will be described in detail below.

The chamber 9 is composed of two chambers. Chambers 9a and 9b
Call. The chamber 9a has a diameter of about 600 mm and a height of about 300.
mm made of stainless steel. The chamber 9a is provided with the lens 10 to be processed, the electrode 52, and the work table 51, and the processing is performed in this. Chamber 9b is about φ1
The positioning unit 6 is made of stainless steel having a height of 500 mm and a height of about 1000 mm and is connected to the work table 51. These two chambers 9a and 9b are connected to a bellows 9c made of stainless steel via a partition wall 9d. The connecting rod 101 that connects the work table 51 and the positioning unit is fixed to the partition wall 9d. In this way, the chamber 9 is divided into the two chambers 9a and 9b, the lens 10 to be processed is arranged on one side, and the positioning unit 6 is arranged on the other side, thereby preventing the positioning unit 6 from being corroded by the reaction gas. The work table 51 was made of stainless steel having a diameter of about 400 mm.

The positioning unit 6 positions the work table 51 with the degree of freedom of linear movement and rotation of the three axes of X, Y, and Z. Therefore, the rotary drive source 42a, the X-direction drive source 22 and A Y-direction drive source (not shown), a Z-direction drive source 122, and drive mechanisms 23, 123, 124, 125, 126, which transmit these drive forces to the connecting rod 101.
And 128, 129, 151 and 152. X,
Each Y has a stroke of about 150 mm and Z has a stroke of 50 mm.

The electrode 52 has an outer diameter of 4 mm and an inner diameter of 2 mm.
The Ni pipe of No. 3 was used. However, the electrode 52 can be replaced with an electrode having a different material and shape. In addition, a pressure sensor was provided in the chamber 9a. On the other hand, the gas exhaust system has a dry pump. Further, a PID control valve is provided between the dry pump and the chamber 9a. The pressure in the chamber 9a is detected by this sensor, and the PID control valve is controlled based on the detection signal to keep the pressure in the chamber 9a constant.

The power supply system 53 is 130 MHz,
High-frequency power source 31 with maximum output of 1 kW and matching circuit 32
It was constituted by. The tilting unit 8 described later is attached to the matching circuit 32. The matching circuit 32 is provided for impedance matching between the chamber 9a and the high frequency power supply 31 and effectively supplying power to the electrode 52.

The tilting unit 8 tilts the electrode 52 so that the surface of the tip of the electrode 52 where plasma is generated is parallel to the portion to be processed on the surface of the workpiece 10.
The tilting unit 8 includes a rotary power source 85 provided outside the chamber 9a, a roller 83, and a rotary power source for the roller 83.
And a supporting portion (not shown) for supporting the roller 83 on the chamber 9a. The electrode 52 is attached to the roller 83. The connecting rod 84 is made of ceramics for insulating the electrode 52 and the chamber 9a. By rotating the rotary power source 85 by a predetermined angle, power is transmitted to the roller 83 by the connecting rod 84, and the electrode 52 can be tilted by a predetermined angle.

The gas supply system 4 is composed of a mass flow controller and a valve for controlling the flow rate of the reaction gas. The reaction gas whose flow rate is controlled by the gas supply system 4 flows inside the pipe-shaped electrode 52 and is continuously supplied from the tip of the electrode 52 to the plasma generated at the tip of the electrode 52. In the apparatus shown in FIG. 13, the reaction gas can be adjusted in the range of 30 cc / min to 100 L / min. The reaction gas is H
e, SF ₆ and N ₂ can be used. The reaction gas can be selected in various ways other than the above depending on the glass material of the lens to be processed.

With this structure, the gas produced in the reaction is
It is sucked by the dry pump of the gas exhaust system 5 and discharged to the outside of the chamber 9a. In addition, the produced gas, which is toxic to the human body,
After being adsorbed by the adsorption device of the gas exhaust system 5, it becomes harmless gas and is released to the atmosphere.

The control system 7 is connected to the tilting unit 6 and the positioning unit 8. The control system is
It has a calculation unit 71, a memory 72, and a reception unit 73.
Three programs are stored in the memory 72.
One of the programs is an NC program for calculating the electrode scanning path shown in the flowchart of FIG.
The second program calculates the normal line of the lens surface to be processed in the calculated scanning path, calculates the tilt angle of the electrode for matching the axial direction of the electrode with this, and based on this, the tilt unit Is a program for obtaining the driving amount of the. The third program uses the calculated tilt angle for electrode 5
The position of the tip of the electrode 52 when 2 is tilted is obtained, and the portion (actual processing point) separated from the tip position of this electrode by a predetermined gap length scans the lens to be processed along the scanning path. Is a program for obtaining the drive amount of each drive unit of the positioning unit 6 for moving the lens 10 to be processed. In the memory 72, the workpiece shape data received by the receiving unit 73 from the operator,
The target shape data, the electrode scanning pitch Δm, the scanning speed v, etc., which are obtained in advance, are stored.

The arithmetic unit 71 reads the NC program and data from the memory 72 at the time of processing and calculates the NC path. In addition, load the second program, N
The tilt angle for matching the electrode with the normal line of the lens 10 to be processed on the C path is calculated, and the driving amount of the tilt unit is calculated based on the tilt angle. Further, the calculation unit 71 reads the third program, and the processing point, which is separated from the tip of the electrode 52 in which the electrode 52 is tilted at the calculated tilt angle by the gap length, is along the scanning path of the lens to be processed 10. R, X, Y, Z drive units 2 of the positioning unit 6 so that they move in
The control signal is output to 2, 42a, 122 and the like.

As described above, it is the plasma CVM that controls the processing point, which is separated from the tip of the electrode 52 by the gap length, to scan along the scanning path on the lens 10 to be processed.
Then, the processing is performed by the plasma generated at the tip of the electrode 52, not by the electrode 52 itself. Therefore, it is necessary to keep the electrode 52 and the lens to be processed at a constant interval (gap length).

A procedure for manufacturing a lens having a desired shape from a lens to be processed using the apparatus having the above-mentioned structure will be described.

First, the lens 10 to be processed of quartz glass is set on the work table 51. Next, the chamber 9a is sealed, and the inside of the chamber 9a is exhausted by the gas exhaust system 5. The gas supply system 4 supplies H to the chamber 9a.
The reaction gas in which a few percent of SF ₆ was mixed with
It is kept constant in the range of 0 to 760 torr.

When a high frequency (130 MHz) of about 100 W is applied to the electrode 52 from the power supply system 53, plasma can be generated only at the tip of the electrode 52.
Then, by the gas supply system 4, the pipe-shaped electrode 5
The reaction gas is continuously supplied to the plasma from the tip of 2 at a constant flow rate of about several tens L / min. The control system 7
As described above, the positioning unit and the electrode tilting unit are controlled based on the NC data, and the electrode plasma generation surface is scanned so as to be parallel to the processing point of the lens to be processed.

As a result, the quartz glass (SiO ₂ ) reacts with the reaction gas, and the removal process proceeds. The reaction formula is considered to be the following formula. Note that He does not contribute to the reaction.

SF ₆ → S + 6F ^* 3SiO ₂ + 2SF ₆ → 3SiF ₄ + 3O ₂ + 2S The processed lens 10 has a shape error of about 1 μm before processing.
With a flat lens with a diameter of 100 mm, the target accuracy ε
= 0.1 μm, the lens processing apparatus shown in FIG. 13 was used for actual processing. As a result, as shown in FIGS. 14 and 15, the processing time was about 5.5 hours, and the shape error was about PV.
It could be 1 μm. In this processing example, since the lens 10 to be processed is a flat lens, the tilt unit 8
Was not used, and processing was performed while maintaining the axial direction of the electrode 52 parallel to the z axis.

Further, as another lens 10 to be processed, a spherical lens having a shape error of about 1 μm and a diameter φ150 before processing is used, and processing is performed by the lens processing apparatus of FIG. 14 with a target accuracy ε = 0.1 μm. It was As a result, as shown in FIG. 15, when the processing time was about 8 hours, the shape error was about 0.1 μm PV.
I was able to. In this processing example, since the lens 10 to be processed is a spherical lens, step 70 in FIG.
In 4, the curve P obtained by slicing the error curved surface C with a spherical surface parallel to the spherical surface of the target shape was obtained. Then, at the time of processing, the electrode tilting unit 8 is used to maintain the axial direction of the electrode in the normal direction of the lens 10 to be processed, and the tip of the electrode along the cross section of the spherical surface when the error curve C is sliced. The processing point scans the lens 10 to be processed.

In this embodiment, the case where the plasma CVM is used as the processing means has been described. However, when the small tool polishing method is used, the electrode 52 described above is used.
Similar processing can be performed by replacing the tip of the and the polisher. In that case, plasma CVM
It is not necessary to maintain the fixed gap length between the tip of the electrode 52 and the lens 10 to be processed as in the above case, and the polisher may be moved so as to contact the lens 10 to be processed.

As described above, according to the shape creating method provided by the present invention, it is possible to accurately machine a workpiece without complicated calculations. Therefore, a highly accurate product can be manufactured at low cost.

In addition to the above-mentioned plane lens or spherical lens, an aspherical lens can be processed with high precision.

Further, in the present invention, polishing or laser processing can be used as the processing means.

[0086]

As described above, according to the shape creating method provided by the present invention, the movement path of the processing means can be easily obtained without complicated calculation, and thus the work piece can be processed easily and accurately. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining a shape creating method of the present invention.

FIG. 2 is an explanatory diagram for explaining the shape creating method of the present invention.

FIG. 3 is an explanatory diagram for explaining the shape creating method of the present invention.

FIG. 4 is an explanatory diagram for explaining the shape creating method of the present invention.

FIG. 5 is an explanatory view for explaining a scanning pitch of the processing means of the shape creating method of the present invention.

FIG. 6 is a flowchart showing the calculation for obtaining the scanning pitch and the moving speed of the processing means of the shape creating method of the present invention.

FIG. 7 is a flowchart showing an operation for obtaining the movement path of the processing means of the shape creating method of the present invention.

FIG. 8 is an explanatory diagram for explaining the shape creating method of the present invention.

FIG. 9 is an explanatory diagram for explaining the shape creating method of the present invention.

FIG. 10 is an explanatory diagram for explaining the shape creating method of the present invention.

FIG. 11 is an explanatory diagram for explaining the shape creating method of the present invention.

FIG. 12 is an explanatory diagram for explaining the shape creating method of the present invention.

FIG. 13 is a block diagram showing the configuration of a lens processing apparatus according to an embodiment of the present invention.

FIG. 14 is an explanatory diagram showing a shape of a lens to be processed before being processed by the lens processing apparatus according to the embodiment of the present invention.

FIG. 15 is an explanatory diagram showing the shape of a lens to be processed after processing by the lens processing apparatus of one embodiment of the present invention.

FIG. 16 is a graph showing the shape of a lens to be processed before and after processing by the lens processing apparatus according to the embodiment of the present invention.

[Explanation of symbols]

4 ... Gas supply system, 5 ... Gas exhaust system, 6 ... Positioning unit, 7 ... Control unit, 8 ...
..Electrode tilting unit, 9 ... Chamber, 51 ...
Work table, 52 ... Electrode, 53 ... Power supply system.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Shibata 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Nikon Co., Ltd. (72) Inventor Yuzo Mori 8-16 9 Private City, Katano, Osaka Prefecture

Claims (13)

[Claims] 1. A shape of a portion to be processed of a workpiece is obtained by obtaining a difference between a shape of the workpiece measured in advance and a target shape of the workpiece determined in advance, and the portion to be processed. , The contour coordinates of a plurality of cross-sections formed in the portion to be processed when sliced at a predetermined interval smaller than the height value of the highest portion of the portion to be processed, the cross-section The processing area is smaller than the cross section, and the processing amount when the workpiece is moved at a predetermined speed is equal to the thickness. The method for forming a shape is characterized in that the workpiece is processed by scanning at a speed of 1. 2. The shape creating method according to claim 1, wherein a value smaller than a target shape accuracy is used as the value of the predetermined interval. 3. The cross section according to claim 1, wherein:
A method for creating a shape, characterized in that, when the processing means is scanned, the processing is performed sequentially from the cross section located on the outside. 4. The scanning device according to claim 1, wherein, when scanning the processing means, a direction in which the processing means is scanned is different from other cross sections in at least one of the plurality of cross sections. A shape creating method characterized by the above. 5. The processing means according to claim 1,
An electrode is used to supply electric power to the electrode to generate plasma at the tip, supply a reactive gas to the plasma, and react the reactive gas with the workpiece to process the workpiece. A shape creating method characterized by the above. 6. The shape creating method according to claim 5, wherein the electrode has an area of a tip portion smaller than any of the plurality of cross sections. 7. The slicer according to claim 1, wherein when the slice is sliced at the predetermined interval, the slice is sliced so as to be a flat surface, and when the slice is scanned, the slicer is moved along the plane. A shape creation device characterized by moving. 8. The slicing device according to claim 1, wherein, when slicing into the predetermined intervals, the slicing is performed so that the cross sections are curved surfaces parallel to each other, and when the processing means is scanned, the processing means is curved. A shape generating device characterized by moving along a shape. 9. A shape of a portion to be processed of the workpiece is obtained by calculating a difference between a shape of the workpiece measured in advance and a target shape of the workpiece determined in advance, and the portion to be processed. , The outer shape of a plurality of cross sections formed in the portion to be processed when sliced at intervals of a predetermined value smaller than the height value of the highest portion of the portion to be processed, For each of the cross sections, and by setting a plane perpendicular to the cross section through the contour of the cross section, the contour is composed of the cross section and a plane perpendicular to the cross section, and By setting a contacting solid and moving a processing means having a processing area smaller than the cross section at the position of the set solid by an amount of movement necessary to remove the solid, Shape creating method characterized by processing the factory product. 10. The shape creating method according to claim 9, wherein a value smaller than a target shape accuracy is used as the value of the predetermined interval. 11. The method according to claim 9, wherein, as a method of moving the processing means necessary for removing the solid, scanning the processing means at the plurality of cross-section positions is performed in order from the outer cross-section. A method for creating a shape, characterized by using a method for all the cross sections. 12. A support means for supporting a workpiece, a processing means for processing the workpiece, a moving means for moving the processing means relative to the workpiece, and the moving means. And a control means for controlling the movement amount of the means, the control means determining the difference between a shape of the workpiece inputted in advance and a predetermined target shape of the workpiece to be processed. And a first means for determining the shape of the portion to be processed, and the outer shape of a plurality of cross-sections formed in the portion to be processed when the portion to be processed is sliced to a predetermined thickness. Second means for obtaining coordinates for each of the cross sections, and third movement path for connecting the coordinates to scan the processing means on the respective cross sections and outputting the movement path to the movement means. With means of A shape generating device characterized by the above. 13. A control device for controlling the amount of movement of a processing means of a shape creating device, wherein a difference between a shape of a workpiece inputted in advance and a predetermined target shape of the workpiece is calculated. A first means for obtaining the shape of a portion of the work piece to be processed by obtaining the shape; and forming the portion to be processed when the portion to be processed is sliced into a predetermined thickness. Second means for obtaining the coordinates of the outlines of a plurality of cross sections for each of the cross sections, and a moving path connecting the coordinates to scan the cross section by the processing means, and the moving path is moved by the moving path. And a third means for outputting to the means.