JPH09254268A - Shape creating method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To process a rotary body with high accuracy by moving the rotary body so as to rotate centering around its rotary center axis and linearly moving the same in its diameter direction and relatively moving the rotary body by the linear movement of the center axis in its axial direction and inclining the axial direction within the plane containing the center axis. SOLUTION: A lens 10 to be processed of which the outer shape is approximate to a rotary body such as a spherical surface lens low in shape accuracy is arranged on a work table 1 so that the center of the approximate spherical surface of the lens to be processed coincides with the center of the rotary driving of the work table 1 by a rotary drive device 604. Further, the lens 10 to be processed is moved in a y-axis direction and an x-axis direction by the x-direction drive device 601 and y-direction drive device of a positioning unit 6. An electrode inclining unit for inclining the shaft of a processing electrode 2 in the normal line direction of the lens 10 to be processed so that a plasma forming surface becomes parallel to the contact plane of the surface of the part desired to be processed of the lens 10 to be processed is attached to a processing electrode 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing an optical lens used for optical products such as a camera, a microscope, and a semiconductor manufacturing apparatus, and more particularly to an apparatus suitable for manufacturing an aspherical lens.

[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 glass lens is manufactured through the following steps.

(1) Pressing step: a step of forming glass blocks by pressing from molten glass, (2) Grinding step: a rough surface having a desired curvature by grinding the glass blocks with a grinding machine. The process of manufacturing a lens.

(3) Smoothing step: a step of removing a scratch or a crack layer on the surface of the rough surface lens by moving a metal dish having diamond pellets adhered on the rough surface lens. Instead of diamond pellets,
In some cases, abrasive grains having a large grain size are supplied between the metal dish and the rough surface lens for processing. Also called sanding process.

(4) Polishing step: A step of polishing the rough surface lens with a polishing polisher to further remove scratches and crack layers on the surface of the rough surface lens, and to correct the shape error generated during the grinding step. .

When a spherical lens is manufactured by the steps (1) to (4), a curve generator is used in the grinding step (2), and a grinding wheel is moved along an arc of a desired lens curvature for processing. I do. In the smoothing step (3), a metal dish having a desired lens curvature is swung on the lens to be processed for processing. In the polishing step (4), a substance softer than glass is attached to a metal dish having a desired curvature, and the polishing is performed while supplying a polishing liquid in which abrasive grains are dispersed in water.

By the way, in addition to the spherical lenses, there are aspherical lenses. This aspherical lens is important because it has excellent performance that cannot be obtained with a spherical lens. The aspherical lens is generally processed by the following method.

First, a spherical lens having an approximate radius of curvature close to the curvature of the target aspherical lens is processed by the above-mentioned grinding process. Then, this spherical lens is processed into an aspherical shape by using a NC control grinding machine. At this point, a shape error of about several μm has occurred.

In the polishing step, the shape error generated in the previous step is corrected and the scratch and crack layers are removed. The polishing process is performed by a small tool polishing or a combination of uniform polishing and small tool polishing.

The small tool polishing is a method in which an NC control polishing machine is equipped with a polishing pad having a diameter smaller than the lens diameter and polishing is performed along an aspherical surface. Uniform polishing refers to polishing while pressing a soft polishing pad 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 highly accurately correct the shape error at an arbitrary position 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 naturally the shape cannot be corrected. In some cases, the uniform polishing may cause a larger shape error than the NC grinding. For this reason, it is general to carry out small tool polishing to correct the shape error after the uniform polishing, and in this case as well, processing time is required.

[0012] On the other hand, as a processing method which does not cause a strain on a workpiece, a strain-free processing method utilizing a radical reaction is described in JP-A-1-125829. In this processing method, plasma is used to generate radicals, especially plasma CVM (Chemical Vaporization).
Ion Machining) (Mori et al.,
Proceedings of the Japan Society for Precision Engineering Spring Conference Academic Lecture P. 637
1992).

The plasma CVM generates plasma at the processing electrode under high pressure and supplies a reactive gas having a high electronegativity such as halogen to the plasma. This is a method in which radicals of the reaction gas are generated, the radicals are caused to react with the surface of the workpiece, and the reaction products are volatilized to perform the processing.

In high-precision machining of a planar object by plasma CVM, the shape (pre-machining shape) of the workpiece is compared with the design value of the object to remove the convex portion of the pre-machining shape. It will be the basis. Specifically, the workpiece is attached to a positioning stage capable of NC control, and the machining electrode is installed at a position facing the surface to be machined and a distance from the surface to be machined. In this state, electric power is supplied to the processing electrode to generate plasma in the processing electrode, and a reactive gas is continuously supplied to the plasma. The positioning stage is moved by numerical control, and the positioning stage is controlled so that the machining electrode stays in the vicinity of the position on the workpiece to be removed for a time corresponding to the removal amount. That is, if the amount of processing is large, it is made to stay for a long time, and if it is small, it is made to stay for a short time. Thereby, it can be processed into a desired shape.

[0015]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a shape creating method capable of processing a rotary object-shaped workpiece such as a spherical lens or an aspherical lens with higher accuracy.

[0016]

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

That is, it is a method of processing the workpiece by bringing the processing region at the tip of the processing means into contact with the workpiece, and creating the shape of the workpiece. When the axial direction of the processing means is made to coincide with the normal line of the portion to be processed on the surface of the workpiece, and the outer shape of the workpiece is a rotary body shape, the processed surface of the workpiece has already been processed. In order to move the processing means from a portion to a portion to be processed next, the processing means is moved with respect to the workpiece about a rotation center axis of the rotation body and a diameter of the rotation body. In a plane including the rotation center axis of the rotating body, while relatively moving by linear movement in the direction of rotation and linear movement in the axial direction of the rotation center axis of the rotating body. It is a method of creating a shape characterized by:

As a processing means, a processing electrode of plasma CVM or small tool polling can be used. In the case of small tool polishing, the processing area is the polishing pad. In the case of plasma CVM, the processing region is a plasma region separated by a certain gap length from the processing electrode tip, so that the distance between the processing electrode tip and the workpiece is controlled to be a predetermined gap length. .

In the present invention, by tilting the processing means so that the axial direction of the processing means coincides with the normal line direction of the workpiece, the surface of the tip of the processing means becomes the tangential plane of the surface of the workpiece. Keep parallel. As a result, the processing depth of the workpiece processed by the processing means can be made uniform. Further, in the present invention, when the portion to be machined is a rotating body such as a spherical surface or an aspherical surface, the workpiece is centered on the rotation axis of the rotating body with respect to the processing means. The rotational movement, the linear movement in the radial direction, and the linear movement in the rotation axis direction of the rotating body move the tip of the processing means to the position to be processed. As a result, the positioning can be performed with a small degree of freedom, and the positioning becomes easy.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A lens processing apparatus according to an embodiment of the present invention will be described with reference to FIG. The lens processing apparatus of the present invention includes a work table 1 for mounting a lens 10 to be processed and a processing electrode 2 for generating plasma in the vicinity of the lens 10 to be processed inside a chamber 9. The work table 1 is made of a conductive material.

As the processing electrode 2, in the case of the embodiment shown in FIG. 1, an electrode having a cylindrical tip portion for generating plasma is used. Hereinafter, of the outer surface of the processing electrode 2, the surface of the tip facing the lens 10 to be processed and generating plasma is referred to as a plasma generation surface.

For the machining electrode 2, the axis of the machining electrode 2 is tilted in the normal direction of the lens 10 to be processed so that the plasma generating surface is parallel to the tangent plane of the surface of the lens 10 to be processed. The electrode tilting unit 8 is attached. In the present embodiment, as shown in FIG. 1, the electrode tilting unit 8 rotates the machining electrode 2 about the base of the machining electrode 2 in the zx plane by an angle θ, so that the machining electrode 2 is moved to the z axis. In contrast, it is configured to be inclined by θ.

A positioning unit 6 is attached to the work table 1 for moving the plasma generating surface of the electrode 2 to be processed to a portion of the lens to be processed during processing. The positioning unit 6 includes a work table 1
An x-direction driving device 601 that drives the lens 10 in the radial direction (x direction) of the lens 10 to be processed, a z-direction driving device 603 that drives the lens 10 in the height direction (z direction), and a φ-direction driving device 604 that rotates. Is built in. Further, the positioning unit 6 also has a built-in y-direction drive device 602 for manually driving the work table 1 in the y-direction, but this is not used for movement during machining in the present embodiment. , Used only for initial alignment.

Drive units 601, 603, 60 for x, z and Φ directions of the electrode tilting unit 8 and the positioning unit 6
A control unit 7 for controlling these operations is connected to 4. Since the y-direction drive device 602 is manual, it is not connected to the control unit 7. The control unit 7 includes a memory 711 for storing externally input data and a control operation program, and a CPU 701 that reads the data and the program to perform a control operation.

On the other hand, a power supply system 3 for supplying power for plasma generation is connected to the processing electrode 2. Further, the chamber 9 is provided with a gas supply system 4 for supplying a reaction gas in the vicinity of the processing electrode 2 and a gas exhaust system 5 for exhausting a gas generated by the reaction between the reaction gas and the lens 2 to be processed. There is.

Next, using the lens processing apparatus of FIG.
The operation of each part when manufacturing a high-precision optical lens will be described.

As the lens 10 to be processed, a lens whose outer shape can be approximated to that of a rotating body, such as a spherical lens having a low shape accuracy, is used. First, the lens 10 to be processed is installed on the work table 1 of the lens processing apparatus of FIG. At this time, the lens is set so that the center of the approximate spherical surface of the lens to be processed coincides with the center of rotation drive of the work table 1 by the rotation drive device 604. Further, the lens 10 to be processed is moved to the y direction by the x-direction driving device 601 and the y-direction driving device of the positioning unit 6.
The tilt unit 8 is moved in the axial direction and the x-axis direction, and
Positioning is performed so that the surface that inclines is aligned with the radial direction (x-axis direction) of the spherical surface of the lens 10 to be processed. This completes the initial alignment.

The chamber 9 is closed and the gas exhaust system 5 temporarily depressurizes the chamber 9. Then, the reaction gas is supplied by the gas supply system 4, and the pressure in the chamber is set to a predetermined pressure (several hundred torr).

The control unit 7 instructs the x-direction driving device 601, the z-direction driving device 603, the φ-direction driving device 604 of the positioning unit 6 and the electrode tilting unit 8 about the driving amount. The control operation of the control unit 7 will be described with reference to the flow of FIG.

The memory 711 stores in advance the shape data of the lens 10 to be processed, which is received from the user via the receiving unit 702, and the shape design value after the processing by the design. The shape data of the lens 10 to be processed before processing is measured using a shape measuring machine such as an interferometer or a coordinate measuring machine.

The CPU 701 of the control unit 7 has a memory 711.
From, read the program shown in the flow of Figure 7,
It works as follows.

First, the shape data of the lens 10 to be processed and the shape (design value) to be processed are read from the memory (steps 701 and 702).

By comparing the design value and the shape data of the lens 10 to be processed, the shape difference between the two is calculated, and the region 601 (FIG. 6) to be processed on the lens 10 to be processed is calculated (step 7).
03). Then, as shown in FIG. 6, the electrode scanning path 602 is set in the area 601 in a predetermined direction. Control unit 7
Is a section P _i within the scanning path 602 of the lens 10 to be processed.
˜P _i ′, points q ⁱ ₁ , q ⁱ ₂ , q ⁱ at predetermined intervals
_3. Set q ⁱ _j and q ⁱ _{j + 1} . The control unit 7 determines that the tip of the machining electrode 2 is at this point q ⁱ ₁ , q ⁱ ₂ , q ⁱ ₃ ... q ⁱ _j , q.
^The positioning unit 6 and the electrode tilting unit 8 are controlled so as to move sequentially over ⁱ _{j + 1} . At this time, the processing electrode 2 is tilted so that the axial direction of the processing electrode 2 coincides with the normal direction of the lens 10 to be processed at each point qj.

Specifically, as shown in FIG. 8, the coordinates (x ⁱ _j , y ⁱ _j , z ⁱ _j ) are obtained for each point q ⁱ _j . Then, the xy coordinates of the obtained coordinates of the point q ⁱ _j are polar coordinates (r ⁱ _j , φ ⁱ _j ,
z ⁱ _j ). However, r ⁱ _j = √ ((x ⁱ _j ) ² +
(Y ⁱ _j ) ² ) and φ ⁱ _j are angles (φ ⁱ _j = tan ⁻¹ (y ⁱ _j / x ⁱ _j )) formed between the radial direction in which the point q ⁱ _j is located and the x-axis.
Further, the normal line direction of the lens 10 to be processed at the point q ⁱ _j is obtained from the shape data of the lens 10 to be processed, and the angle θ ⁱ _j formed by this normal line and the central axis of the lens 10 to be processed is obtained. This (r ⁱ _j , φ ⁱ _j , z ⁱ _j , θ ⁱ _j ) is set as the data of the point q ⁱ _j (step 705).

Further, the control section 7 determines the point q ⁱ _j from the difference between the shape data of the lens 10 to be processed and the shape (design value) to be processed.
In step 706, the amount to be machined is calculated, and the time T ⁱ _j for which the machining electrode 2 is to stay is further calculated from this amount (step 706).

In steps 705 and 706, all points q ⁱ _j set on the electrode scanning path 602 are obtained.

The control unit 7 controls the point q ¹ ₁ (r ¹ ₁ , φ ¹ ₁ , z ¹ ₁ ,
First, in order to position the tip of the machining electrode 2 at θ ¹ ₁ ), θ ¹ ₁ is output to the tilting unit 8 and x of the positioning unit 6 is output.
In the direction drive device 601, (r ¹ ₁ + (d + s) sin θ ¹ ₁ )
Is output to the z-direction driving device 603 (z ¹ ₁ + (d + s)
(1-cos [theta] ¹ ₁₎₎ and then outputs a phi ¹ ₁ to phi direction drive unit 604 (step 707). Thus, the positioning unit 6 moves the tip of the electrode 2 in a position apart a distance s from the point q ¹ ₁ of the uncut lens 10. The electrode tilting unit 8 makes the axial direction of the machining electrode 2 coincide with the normal direction of the point q ¹ ₁ . Here, d is the length of the processing electrode 2. s is a gap length between the processing electrode 2 and the lens 10 to be processed, which is predetermined for processing. Therefore, the plasma generation surface at the tip of the electrode 2 is the point q of the lens 10 to be processed.
¹ ₁ the machining distance s, parallel to facing the tangent plane of the lens to be processed 10.

Then, the gas supply system 4 is made to supply the reaction gas at a predetermined gas pressure. In addition, the control unit 7
The power supply system 3, during the time T ¹ _1, which had been obtained in step 706, an instruction to apply a high frequency power to the machining electrode 2. The amount of power supplied by the power supply system 3 is set in advance. As a result, plasma is generated on the plasma generation surface of the processing electrode 2, and radicals of the reaction gas are generated by this plasma, and the radicals of the reaction gas react with the lens 10 to be processed. The reaction product volatilizes and is exhausted from the gas exhaust system 5. As a result, the lens to be processed 1
Point q ¹ ₁ 0 is processed by the processing amount necessary.

After the processing of the point q ¹ ₁ (r ¹ ₁ , φ ¹ ₁ , z ¹ ₁ , θ ¹ ₁ ) is completed, the control section 7 temporarily stops the supply of electric power to the processing electrode 2, The tip of 2 is the point q ¹ ₂ (r ¹ ₂ ,
φ ¹ _2, z ¹ _2, is moved theta ¹ ₂₎ to. Specifically, the following formula is calculated and Δθ ¹ ₂ = θ ¹ ₂ −θ ¹ ₁ Δr ¹ ₂ = r ¹ ₂ −r ¹ ₁ + (d + s) (sin θ ¹ ₂ −sin θ
¹ ₁ ) Δz ¹ ₂ = z ¹ ₂ −z ¹ ₁ + (d + s) (cos θ ¹ ₂ −cos θ
¹ ₁ ) Δφ ¹ ₂ = φ ¹ ₂ −φ ¹ ₁ Δθ ¹ ₂ is output to the tilt unit 8, Δr ¹ ₂ is output to the x-direction drive device 601 of the positioning unit 6, and Δz ¹ ₂ is z.
It outputs to the direction driving device 603, and outputs Δφ ¹ ₂ to the φ direction driving device 604. Thereby, the tip of the machining electrode 2 is
While drawing the locus 801 in FIG. 8, move to the point q ¹ ₂ . After the movement, the control unit 7, to the power supply system 3, and instructs the power supply to between the machining electrode 2 times T ¹ _2, to perform the machining of the point q ¹ _2. This is repeated for all points of the path of P _{1 to} P ₁ ′, and when it is finished, it is similarly performed for the path of P _{2 to} P ₂ ′, and processing is performed for all the paths P _{i to} P _i ′ (step 708). Δθ ⁱ _j , Δ used in this operation
A general formula for obtaining r ⁱ _j , Δz ⁱ _j , and Δφ ⁱ _j is shown.

Δθ ⁱ _{j + 1} = θ ⁱ _{j + 1} −θ ⁱ _j Δr ⁱ _{j + 1} = r ⁱ _{j + 1} −r ⁱ _j + (d + s) (sin θ ⁱ _{j + 1} −s
in θ ⁱ _j ) Δz ⁱ _{j + 1} = z ⁱ _{j + 1} −z ⁱ _j + (d + s) (cos θ ⁱ _{j + 1} −c
os θ ⁱ _j ) Δφ ⁱ _{j + 1} = φ ⁱ _{j + 1} −φ ⁱ _{j By the} above steps, the tip of the processing electrode 2 is moved along the scanning path 602 in the region 601 to be processed in FIG. However, since the processing can be performed in the required processing amount, the lens 10 to be processed can be processed into the designed shape.

Lens 1 to be processed when controlled in this way
The locus of the tip of the processing electrode 2 on 0 depends on the interval between the points q ⁱ _j set on the scanning path 602. That is, as shown in FIG. 10, the smaller the interval between the points q ⁱ _j , the more linear the locus can be. Further, as the distance from the rotation center (x = 0, y = 0) of the lens to be processed 10 becomes smaller, the deviation width w from the straight line becomes smaller. As described above, in the present embodiment, by tilting the processing electrode 2, Lens to be processed 10 for plasma generation surface
Since the plasma is kept parallel to the tangent plane of H.sub.2, the plasma intensity becomes uniform, and the reaction gas flows evenly between the electrode 2 and the lens 10 to be processed. The parts where the plasma generation surfaces face each other can be uniformly processed. Therefore, the lens to be processed can be processed into a desired shape with high accuracy by a processing amount corresponding to the staying time of the processing electrode 2.

In order to make the plasma generating surface parallel to the lens to be processed, the scanning path 60 is inclined while the processing electrode 2 is inclined.
In the case of moving along the line 2, normally, it is necessary to move the lens 10 to be processed in the xyz direction and rotate the processing electrode 2 in the φ direction and the θ direction as shown in FIG. . Therefore, the axis directions to be controlled are x, y,
There are also five axes, z, φ, and θ, which complicates calculation and control. On the other hand, in the present embodiment, the processing electrode 2 is always tilted (θ) in the radial direction of the lens 10 to be processed, and the lens 10 to be processed is radially (x = r direction) and rotational direction (φ direction).
And moved in the height direction (z direction). Therefore, it is not necessary to control the movement amount in the y direction during processing. Therefore, since the axial directions to be controlled are the four axes of r, z, φ, and θ, the control unit 7 can easily control the positioning unit 6 and the electrode tilting unit 8 during processing. Further, in the present embodiment, the y-direction driving device 604 is provided in the positioning unit 6 and is manually operated in order to perform the initial alignment when the processing lens 10 is mounted on the work stage 1. When using a method capable of accurately installing the processing lens 10 from the beginning at a position to be aligned when the processing lens 10 is mounted on the work stage 1, y
It is not necessary to have the directional drive 604.

When the driving amounts of the five axes of x, y, z, φ, and θ are controlled to tilt the processing electrode 2 and keep the plasma generating surface parallel to the tangential plane of the lens to be processed 10, The movement amount of the processing lens 10 in the xy directions is required to be equal to the diameter of the lens to be processed plus the inclination of the processing electrode. On the other hand, when the movement is controlled by the four axes of r, z, φ, and θ as in the present embodiment, the above equation Δr ⁱ _{j + 1} = r ⁱ _{j + 1} −r ⁱ _j + (D + s) (sin θ ⁱ _{j + 1} −s
As can be seen from in θ ⁱ _j ), the amount of movement in the r direction is obtained by adding only the tilt of the processing electrode 2 to the radius of the lens to be processed,
The required amount of movement can be halved when controlling with 5 axes. Therefore, the diameter of the chamber 9 can be halved, which is particularly effective for a device for processing a large lens 10 to be processed. Further, since the diameter of the chamber 9 and the movement amount of the positioning unit 6 can be reduced by half in this way, the device cost can be reduced.

If the machining electrode 2 is not tilted, x
The machining electrode 2 can be made to scan the scanning system of the lens to be processed 10 and 602 only by driving in the three axis directions of yz. In that case, the surface of the tip of the machining electrode 2 is to be processed to the lens to be processed. Cannot be kept parallel to the tangent plane of. Therefore, as shown in FIGS. 4A and 4B, it is unavoidable that one edge of the processed electrode 2 moves closer to or away from the lens 10 to be processed than the other edge of the processed electrode 2. In the case of FIG. 4A, since the edge portion 307 of the processing electrode 2 is close to the lens 301 to be processed, a region 303 having high plasma intensity is generated in the plasma 306, and this region 303 is generated.
The processing amount of the lens 10 to be processed in contact with is increased. Further, in the case of FIG. 4B, the edge portion 308 of the processing electrode 2 is too far from the lens 10 to be processed, and the plasma 304 has a region 305 of low plasma intensity.
The processing amount of the lens 301 to be processed that is in contact with this region 305 is reduced.

Besides the plasma intensity, FIG.
In the case of (a) and (b), the size and shape of the space formed between the lens to be processed and the electrode change, and accordingly, the space between the electrode and the lens to be processed changes. The flow rate of the reaction gas is different. The variation in the processing amount also occurs due to the change in the flow rate of the reaction gas.

On the other hand, in the present embodiment, by tilting the processing electrode 2, it is possible to keep it parallel to the surface of the lens 10 to be processed, so that the processing amount becomes uniform,
The lens to be processed can be processed with high accuracy. Also,
By tilting the processing electrode, the operation of scanning the processing electrode 2 on the surface of the lens 10 to be processed becomes complicated, but in the present embodiment, the axial direction for moving the lens 10 to be processed is the radial direction and the rotation direction. By setting the height direction, the movement amount is small and the number of axes to be controlled is reduced, so that the processing electrode 2 can be easily scanned on the surface of the lens 10 to be processed.

In the above-described embodiment, while the electrode is moved from the processing point on the lens to be processed to the processing point, the power supply to the processing electrode is temporarily stopped so that the trajectory of the electrode is processed during the movement. However, the present invention is not limited to this method, and it is also possible to use a method in which the gap length between the lens to be processed and the electrode during movement is made wider than that during processing. In this case, a step of instructing the x-direction drive device 601 and the z-direction drive device with a predetermined constant drive amount to widen the gap is added before the movement in step 708, and then in step 708. This can be achieved by causing the movement and when the step 708 is completed, this time, in order to restore the gap, the step of restoring the drive amount of the above-mentioned drive device to the original amount is performed. . When the method of widening the gap length is used, it is not necessary to temporarily stop the power supply to the working electrode.

In the above-mentioned embodiment, a cylindrical electrode is used as the machining electrode 2, but the present invention is not limited to the cylindrical electrode. In the cylindrical electrode, the surface for generating plasma, that is, the surface facing the lens to be processed is
Although it is a flat surface, a pipe-shaped electrode, an electrode in which a surface for generating plasma is divided into a plurality of surfaces, an electrode having a curved surface for generating plasma, or a net-shaped electrode may be used. When the plasma generation surface is a curved surface, the plasma generation surface of the processing electrode is processed by keeping the contact surface at the center of the plasma generation surface parallel to the contact surface of the processed part of the lens to be processed before processing. Can be kept parallel to the lens. Further, when the ring-shaped plasma is generated only in the peripheral portion of the electrode as in the case of using the pipe-shaped electrode, the plane formed by the portion where the plasma is generated is defined as the plasma generation surface. To be parallel to the lens to be processed.

The tangent plane of the processed portion of the lens to be processed can be defined by the tangent plane of the curved surface of the lens to be processed before processing when the processing amount is small. However, when the amount of processing is large, the inclination of the tangent plane changes in response to the change in the curved surface of the lens being processed, so the change in the curved surface is calculated or measured and the processed electrode is made to follow this change. It is desirable to tilt.

Further, in the above embodiment, the plasma C
Although the processing apparatus by the VM method has been described, the method of keeping the processing means parallel to the lens to be processed is also effective for processing methods other than the plasma CVM method. For example, even in the small tool polishing method, by keeping the polishing pad parallel to the surface of the lens to be processed and contacting the lens to be processed,
Since it is possible to equalize the amount of processing on the surface that the polishing pad contacts, highly accurate processing can be performed. That is,
By keeping the axial direction of the rod with the polishing pad aligned with the normal direction of the surface of the workpiece, the polishing pad can be kept parallel to the surface of the lens to be polished, improving the polishing accuracy. You can

Also in the case of small tool polishing, the polishing pad is moved on the lens to be processed by driving the lens to be processed 10 in the radial direction, the rotation direction and the height direction as in the present embodiment. The control can be easily performed.

[0052] Also, in the case of this embodiment, in step 706 of FIG. 7 determines the time T ⁱ _j to be staying the machining electrode 2 at each point q ⁱ _j, to control the amount of processing by the residence time As a result, the lens 10 to be processed is processed by one-time control. However, the present invention is not limited to this, and the processing electrode 2 is scanned for a fixed staying time, and the region where the amount to be processed is large is scanned a plurality of times, so that the processing is performed by the target processing amount. Can be configured.

For example, as shown in FIG. 11, each region H ₁ , H ₂ , H ₃ , H ₄ , H _5, ... When the region 601 to be processed is sliced at a predetermined height h (working amount).・ Set
A scanning path is determined so that the processing electrode 2 scans each area. As a result, a region having a large amount to be processed is scanned a plurality of times according to the amount to be processed. Further, the dwell time and the scanning pitch of each point of the processing electrode 2 are set in advance so that the lens 10 to be processed is uniformly removed by the processing amount h by one scanning. As a result, the regions H ₁ , H ₂ ,
By scanning in the order of H ₃ , H ₄ , and H ₅ , the layers can be removed in order from the upper layer, and the target shape of the lens to be processed can be obtained. At this time, the tip of the processing electrode 2 is
When scanning each of the areas H ₁ , H ₂ , H _3, ..., The distance between the processing electrode 2 and the lens 10 to be processed is set so as to maintain a constant gap length with respect to the surface of the area being scanned. Control. However, the region 601 to be processed of the lens 10 to be processed
When the value of the height of the highest portion is smaller than the gap length between the processing electrode 2 and the lens 10 to be processed, _one of the areas H ₁ , H ₂ , H ₃ ... It is possible to fix the distance between the processing electrode 2 and the lens 10 to be processed so as to maintain a constant gap length between them, and to process all the regions H ₁ , H ₂ , H ₃ ... With this distance. . In this way, when the distance between the processing electrode 2 and the lens 10 to be processed is fixed, the areas H ₁ , H ₂ , H ₃ ... Are arranged in the order of H ₃ , H ₂ , H ₁ , or H ₂ , H 3. Even if scanning in the order of ₁ , H ₃ , H ₁ , H ₂ , H ₃
It is possible to obtain a processed shape similar to the case of scanning in the order of.

Further, in these cases, as shown in FIG. 12, by making the scanning direction different from the other regions in at least one region, the processing mark formed on the lens 10 to be processed becomes deep. Can be prevented.

[0055]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A lens processing apparatus according to an embodiment of the present invention will be described with reference to FIG. The parts corresponding to those of the processing apparatus according to the embodiment of FIG. 1 are designated by the same reference numerals as those in FIG. 1, and the description thereof will be omitted.

The chamber 9 includes two chambers 9a and 9b.
Is divided into The chamber 9a that houses the lens 10 to be processed and the work table 1 is made of stainless steel and has a diameter of about 600 mm and a height of about 300 mm. Positioning unit 6
Is stored in a chamber 9b independent of the chamber 9a,
The positioning unit 6 was prevented from being exposed to the reaction gas and corroding. Chamber 9b that houses the positioning unit 6
Was made of stainless steel having a diameter of about 1500 mm and a height of 1000 mm. A stainless bellows 9c was connected between the chambers 9a and 9b via a partition wall 9d. The connecting rod 101 connecting the work table 1 and the positioning unit 6 was fixed to the partition wall 9d on the bottom surface of the bellows 9c. Work table 1
Was made of stainless steel with a diameter of 400 mm.

The machining electrode 2 has an outer diameter of 5 mm and an inner diameter of 3
A mm pipe made of Ni was used. However, the electrode 2 can be replaced and various shapes can be attached.

The power supply system 3 includes a high frequency power source 31 having a maximum output of 1 kW at 130 MHz and a matching circuit 32.
Composed by and. The matching circuit 32 is provided for impedance matching between the chamber 9a side and the high frequency power supply 31.

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 processing electrode 2 and is continuously supplied from the tip of the electrode 2a to the plasma generated at the tip of the electrode 2a. In the apparatus shown in FIG. 2, the reaction gas can be adjusted in the range of 30 cc / min to 100 L / min. He, SF is used as the reaction gas.
₆ , N ₂ can be used. The reaction gas can be selected variously depending on the glass material of the lens 10 to be processed.

The gas exhaust system 5 is composed of a dry pump, an adsorption device, and a valve. With this configuration, the gas generated by the reaction is sucked by the dry pump and discharged to the outside of the chamber 9a. Further, the produced gas, which is toxic to the human body, is adsorbed by the adsorption device, and then a harmless gas is released to the atmosphere.

The positioning unit 6 for moving the lens 10 to be processed and the work table 1 has the degree of freedom of linear movement and rotation in the three axial directions of X, Y and Z. X and Y are about 150 each
mm and Z had a stroke of 50 mm.

The mechanism of the positioning unit 6 will be further described.

A connecting rod 101 is attached to the work table 1. The partition wall 9d is provided with a through hole. The connecting rod 101 penetrates the through hole in an airtight state and is fixed to the partition wall 9d. Therefore, when the connecting rod 101 is displaced, the partition wall 9d is displaced within the degree of freedom of the bellows 9c. A rotation drive source 42a for rotating the work table 1 is attached to an end portion of the connecting rod 101 to rotate the connecting rod 101.

Further, in order to displace the work table 1 in the z direction, a driving power source 122 and a ball screw shaft 123 connected thereto are arranged. Ball screw shaft 1
The axial direction of 23 is the z direction. Also, ball screw shaft 1
A guide rod 23 is arranged in parallel with 23. A nut block 125 is attached to the ball screw shaft 123 and the guide rod 23. The nut block 125 includes a support rod 128 that supports the connecting rod 101.
Has been fixed.

The nut block 125 is formed with a female screw that meshes with the male screw of the ball screw shaft 123. Further, the nut block 125 is provided with a through hole that allows the guide rod 23 to pass therethrough. Drive power source 122
However, when the ball screw shaft 123 is rotated, the nut block 125 is displaced in the z direction while being guided by the guide rod 23. When the nut block 125 is displaced in the z direction, the support rod 128 is also displaced in the z direction, and the connecting rod 101 and the work table 1 supported by the support rod 128 are also displaced in the z direction.

The driving power source 122 is a support block 126.
Fixedly mounted on top. This support block 126
Are mounted on a support table 124 having a smooth surface. The drive power source 22 is also fixed on the support table 124.

A female screw is formed on the support block 126 in the y direction and meshes with the ball screw shaft 129. When the driving power source 22 rotates the ball screw shaft 129,
The support block 126 slides on the support table 124 in the y direction. Accordingly, the ball screw shaft 123, the guide rod 23, the nut block 125, the support rod 128,
The connecting rod 101 is also displaced in the y direction, so that the work table 1 is also displaced in the y direction.

Further, as a mechanism for displacing the work table 1 in the x direction, there are provided a ridge 151 provided on the back surface of the support table 124 and a groove 152 for guiding the ridge 151. The longitudinal direction of the convex line 151 and the concave groove 152 is the x direction. A ball screw shaft for displacing the support table 124 in the x direction and a driving power source (not shown) are attached to the support table 124.

The above is the configuration of the positioning unit 6.

Next, the structure of the electrode tilting unit 8 will be described with reference to FIGS. Here, FIG. 5 is a cross-sectional view of the electrode tilting unit 8. As shown in FIGS. 3 and 5, in the present embodiment, the electrode 2 is fixed to the roller 81, and the shaft 82 fixedly attached to the roller 81 is supported by the supporting portion 83. Of the shaft rod 82,
The shaft rod 82a on one side was connected to a driving power source 85 installed outside the chamber 9a. The shaft rod 82a is made of ceramics. By driving the driving power source 85 and rotating the shaft rod 82, the electrode 2 is tilted, and the central axis of the electrode 2 is set at an arbitrary position of the lens 10 to be processed.
Can be oriented in the normal direction of. In addition, the drive power source 8
Since No. 5 is installed outside the chamber, it is not corroded by the reaction gas. Further, the shaft rod 82b on the other side is provided with a flow path 102 for flowing a reaction gas. The roller 81 has a flow path 102 and a flow path 11 of the electrode 2.
A flow channel 112 that connects with 3 is provided. The reaction gas of the gas supply system 4 is supplied from the gas hose 103 fixed to one end of the shaft rod 82b, and the flow path 10 of the shaft rod 82b is supplied.
2, the flow path 112 of the roller 81 and the flow path 1 inside the electrode
It passes through 13 and is supplied to the plasma generated at the tip of the electrode 2.

The control unit 7 has the same structure as in FIG. The control unit 7 controls the positioning unit 6 and the electrode tilting unit 8 by performing the operation shown in the flow of FIG. 7. Specifically, in steps 707 and 708 of FIG.
¹ ₁ , Δθ ⁱ _{j + 1} is instructed to the driving power source 85 of the electrode tilting unit, r ¹ ₁ , Δr ⁱ _{j + 1} is instructed to the x-direction driving power source (not shown), and φ ¹ ₁ , Δφ ⁱ the _{j + 1} instructs the rotational drive power source 42a, z ¹ _1, and instructs the Delta] z ⁱ _{j + 1} in the z-direction driving power source 122. Further, the y-direction drive power source 22 is manually instructed the drive amount.

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

First, the processed lens 10 of quartz glass is set on the work table 1. 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 5 supplies the reaction gas in which He is mixed with several% of SF ₆ to the chamber, and several hundred to seven
It is kept constant within the range of 60 torr.

When a high frequency (130 MHz) of about 100 W is applied to the processing electrode 2 from the power supply system 3, plasma can be generated only at the tip of the electrode 2. Then, the reaction gas is continuously supplied to the plasma from the tip of the pipe-shaped electrode 2 from the gas supply system 4 at a constant flow rate of about several tens L / min. The control unit 7 controls the positioning unit 6 and the electrode tilting unit 8 as in the flow chart of FIG.
Scan toward the normal direction of.

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 shape error from the design value of the target spherical lens is about 1 μm.
When the spherical lens of m was used as the lens to be processed 10 and the shape was corrected by the processing apparatus of the present invention to manufacture the spherical lens, the shape error could be 0.1 μm in the processing time of about 8 hours. However, the lens 10 to be processed is φ150
mm.

The above is an example of processing the spherical lens, but similarly, the aspherical lens can be processed with high precision and high speed by using the spherical lens or the aspherical lens as the lens to be processed.

[0078]

As described above, by using the shape generating method provided by the present invention, it is possible to process a rotating body-shaped workpiece such as a spherical lens or an aspherical lens with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a lens processing device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a lens processing apparatus according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a configuration of an electrode tilting unit 8 of the lens processing apparatus of FIG.

4A and 4B are explanatory views showing the arrangement of electrodes and a lens to be processed when the electrodes are not tilted, and the state of plasma.

5 is a partial cross-sectional view showing the configuration of an electrode tilting unit 8 of the lens processing device of FIG.

FIG. 6 is an explanatory diagram showing an electrode scanning path of the lens processing apparatus according to the embodiment of the present invention.

FIG. 7 is a flowchart showing the operation of the control unit 7 of the lens processing apparatus according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram showing an electrode scanning path of the lens processing apparatus according to the embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a movement axis required when the axial direction of the electrode is made to coincide with the normal direction of the lens to be processed by a normal method.

FIG. 10 is an explanatory diagram showing trajectories of electrodes of the lens processing apparatus according to the embodiment of the present invention.

FIG. 11 is an explanatory diagram showing an electrode scanning path of the lens processing apparatus according to the embodiment of the present invention.

FIG. 12 is an explanatory diagram showing an electrode scanning path of the lens processing apparatus according to the embodiment of the present invention.

[Explanation of symbols]

1 ... Work table, 2 ... Processing electrode, 3 ...
Power supply system, 4 ... Gas supply system, 5 ...
・ Gas exhaust system, 6 ・ ・ ・ Positioning unit, 7 ・
..Control unit, 8 ... Electrode tilting unit, 9 ... Chamber, 601, ...
2 ... Scanning path of electrodes.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yuzo Mori 8-16-9 Private City, Katano City, Osaka Prefecture

Claims (10)

[Claims] 1. A reaction gas is supplied to a workpiece, an electrode for locally generating plasma is opposed to the workpiece, and the reaction gas and the workpiece are caused by the plasma generated by the electrode. Of the outer surface of the electrode when the processing is performed by processing the workpiece by volatilizing the reaction product to create a shape of the workpiece. The plasma generation surface that faces the workpiece and generates the plasma is kept parallel to the portion to be processed on the surface of the workpiece, and if the outer shape of the workpiece is a rotating body, In order to move the electrode from the processed part of the surface of the work piece to the part to be processed next, the electrode is relatively positioned with respect to the work piece with the rotation center axis of the rotating body as the center. Rotational movement and radial direction of the rotating body And linear movement,
The rotating body is moved by linear movement in the axial direction of the rotation center axis of the rotating body, and the normal direction of the plasma generation surface of the electrode is inclined within a plane including the rotation center axis of the rotating body. Shape creation method. 2. The shape creating method according to claim 1, wherein the electrode having the plasma generation surface smaller than the surface of the workpiece is used as the electrode. 3. The shape creating method according to claim 1, wherein the rotational movement, the linear movement in the radial direction, and the linear movement in the rotation axis direction are performed by moving the workpiece. . 4. The shape creating method according to claim 1, wherein in order to tilt the axial direction of the electrode, the electrode is rotationally moved about a point on the electrode axis within the plane. 5. The shape creating method according to claim 1, wherein the electrode is allowed to stay on a plurality of points to be processed on the surface of the workpiece for a time corresponding to a required processing amount. 6. The shape creating method according to claim 5, wherein the electrode is moved over a surface of the workpiece to move the workpiece from a point to be processed to a point. 7. A method for processing a workpiece by bringing the processing region at the tip of a processing means into contact with the workpiece to create a shape of the workpiece, wherein the processing includes: The axial direction of the processing means is made to coincide with the normal line of the portion to be processed on the surface of the workpiece, and when the outer shape of the workpiece is a rotator shape, the processed surface of the workpiece has already been processed. In order to move the processing means from a portion to a portion to be processed next, the processing means is moved with respect to the workpiece about a rotation center axis of the rotation body and a diameter of the rotation body. Linear movement in the direction,
While relatively moving by linear movement in the axial direction of the rotation center axis of the rotating body, the axial direction of the processing means,
A shape creating method characterized by inclining in a plane including a rotation center axis of the rotating body. 8. A support part for supporting a work piece, an electrode arranged at a position facing the work piece for forming plasma, and the work piece being rotationally moved relative to the electrode. Rotation driving means for moving the workpiece, first linear driving means for linearly driving the workpiece relatively to the electrode, and linearly driving the electrode on the main plane of the workpiece. The second linear driving means, the tilt driving means for tilting the electrode shaft within the predetermined plane, the rotation driving means, the first and second linear driving means, and the tilt driving means. And a control means for controlling, wherein the control means, when the outer shape of the workpiece is a rotating body, sets the rotation center of the rotation moving means to the rotation axis of the rotating body of the workpiece. The tilt drive means A shape creating device, characterized in that a plane determined by caulking is matched with a diameter of the rotating body of the workpiece. 9. The control means according to claim 8, wherein the control means obtains a normal line of a point to be machined on the surface of the work piece by using the shape data of the work piece, and the normal line and the electrode axis. The shape generating device is characterized in that an inclination amount of the electrode for making the same coincide with each other is obtained and is instructed to the inclination driving means. 10. The shape creating apparatus according to claim 8, wherein a diameter of a surface of the electrode facing the workpiece is smaller than a diameter of the workpiece.