JP2000237942A - Grinding method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding method and a grinding apparatus capable of precisely processing a sharp edge even at a discontinuous portion of an axisymmetric aspherical component constituted by a plurality of discontinuous curved surfaces. I will provide a. SOLUTION: An axisymmetric disk-shaped grinding wheel 2 having a pointed tip 2A, and a grinding wheel rotation axis of the grinding wheel orthogonal to a rotation axis of an axisymmetric workpiece 4, and further on the workpiece 4. The grinding wheel 2 is driven in the radial direction and the rotation axis direction of the workpiece 4 in a state where the rotating direction of the grinding wheel 2 in contact with the workpiece 4 is parallel to the rotating direction of the workpiece 4, and a plurality of discontinuous Manufactures axisymmetric aspherical parts composed of various curved surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding method and an apparatus therefor, and more particularly to a method and an apparatus for grinding a micro Fresnel lens such as a holographic optical element.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
There were the following. (1) Yuji Yamazaki, Kazuto Nakamura, Hiroshi Hashimoto: Development of LED with built-in Fresnel lens, Journal of Precision Engineering, 59, 4 (199)
3) 123. (2) Masaaki Sunohara, Makoto Umeya, Yoshiyuki Shimizu, Yoshinori Shiratoh: Molding Holographic Aspheric Lenses-Die Technology for Use with DVD / CD-, Nikkei Mechanical, 458, (1995) 4
0. (3) Yutaka Yamagata, Toshiro Higuchi, Katsunobu Ueda, Joe Takashima, Motoharu Ohno: Fabrication of blazed free-form diffraction grating by precision cutting, Proceedings of the 1996 JSPE Spring Conference, (1996) 533 . (4) Shinya Morita, Yutaka Yamagata, Toshiro Higuchi: Study on Cutting Conditions for Holographic Optical Elements, Proc. Of the 1997 Autumn Meeting of The Japan Society for Precision Engineering, (1997) 21. (5) H. Suzuki, S .; Kodera, T .; Na
Kasuji, T, Ohta and K.K. Syoj
i: Precision Grinding of As
chemical CVD-SiC Molding
Die, Int. J. JSPE, 32, (1998) 2
5. (6) Hirofumi Suzuki, Nao Kodera, Shigeki Maekawa, Kumiko Morita, Eiichi Sakurai, Katsutoshi Tanaka, Hiroshi Takeda, Tsunemoto Niikawa, Katsuo Shoji: Study on ultra-precision grinding of micro aspheric surface-Micro aspheric surface by oblique axis grinding method Verification of Mirror Surface Grinding-, Journal of Precision Engineering, 64, 4 (1998) 541. In recent years, needs for micro Fresnel lenses such as holographic optical elements have been increasing. Such a Fresnel lens must be mass-produced by a molding method using a fine mold having a large number of discontinuous curved surfaces for the purpose of use.

FIG. 19 is a view showing an example of a molding process of a conventional glass Fresnel lens.

[0004] First, as shown in FIG.
19 and a glass material 53 were set between the upper mold 52 and FIG.
As shown in (b), the glass material 53 is heated and pressed by the upper mold 52. Next, as shown in FIG. 19C, the upper mold 52 is unloaded.

[0005] On the other hand, hitherto, machining of a mold has been mainly performed by cutting with a minute single-crystal diamond tool, and mold materials have been limited to soft metals such as oxygen-free copper, brass, and electroless Ni. As a result, the lens material was mainly a plastic lens having a low molding temperature. But D
VD (Digital Video Disc) or CD
(Compact Disc) etc.
In order to improve the performance, it is indispensable to improve the optical characteristics and heat resistance by changing to a glass lens, and it is necessary to develop ultraprecision and fine processing technology for a ceramic mold having such a fine shape.

FIG. 20 is a perspective view showing such a conventional ceramic grinding apparatus, and FIG. 21 is an explanatory view of a grinding method by the grinding apparatus.

In these figures, 101 is a grinding wheel axis, 1
02 is a grinding wheel, 103 is a spindle, and 104 is a workpiece (Fresnel-shaped workpiece).

As shown in FIG. 1, an axisymmetric disk-shaped grinding wheel 102 is used, and the rotation direction of the grinding wheel 102 which is in contact with the axisymmetric workpiece 104 is perpendicular to the rotation direction of the workpiece 104. I have.

As apparent from these figures, the grinding of the axisymmetric aspherical workpiece has been performed by the simultaneous two-axis control machine for the X and Z axes.

[0010]

In the above-described conventional grinding apparatus, when an axisymmetric aspherical optical component (Fresnel lens) composed of discontinuous curved surfaces is ground,
As shown in FIGS. 20 and 2 1, is rotating the direction orthogonal direction of rotation and the grinding wheel 102 of the workpiece 104 at the processing point, the arc shape of the grinding wheel 102 is transferred to the step portion, in a sharp step There is a problem that precision processing of the Fresnel shape is difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to precisely grind a sharp edge even at a discontinuous portion of an axisymmetric aspherical part constituted by a plurality of discontinuous curved surfaces. An object is to provide a processing method and an apparatus therefor.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides: [1] In a grinding method, an axisymmetric disk-shaped grinding wheel having a sharp tip and a rotating axisymmetric workpiece are provided. In a state where the grinding wheel rotation axis of the grinding wheel is orthogonal to the axis, and furthermore, the grinding wheel is arranged so that the rotation direction of the grinding wheel contacting on the workpiece is parallel to the rotation direction of the workpiece. The workpiece is driven in the radial direction and the rotation axis direction of the workpiece to produce an axisymmetric aspherical part composed of a plurality of discontinuous curved surfaces.

[2] In the grinding method according to the above [1], the aspherical component is a hard Fresnel optical component.

[3] In the grinding method according to the above [2], the aspherical part is a glass micro Fresnel lens.

[4] In the grinding method according to the above [1], the feed speed of the grinding wheel can be controlled.

[5] A four-axis (X, Y, Z, C) controlled grinding machine equipped with a vertical grinding wheel spindle with an aerostatic bearing and a horizontal spindle, and a linear scale feedback system with a resolution of nm order. An axially symmetric disk-shaped grinding wheel having a knife-edge shaped tip, and an axisymmetric workpiece having a rotation axis Z orthogonal to a grinding wheel rotation axis Y of the grinding wheel; Simultaneous axis 2
The apparatus is provided with axis control means and grinding wheel feed speed control means.

[0017]

Embodiments of the present invention will be described below in detail.

FIG. 1 is a perspective view of a main part of a grinding apparatus showing an embodiment of the present invention, and FIG. 2 is an explanatory view of a grinding method by the grinding apparatus.

As shown in these figures, a grinding wheel 2 having a grinding wheel shaft 1 and a sharp knife edge shape having a sharp tip 2A is used. The rotation direction of a workpiece 4 at a grinding point and the grinding wheel 2
The grinding direction is such that the rotation directions are parallel. Reference numeral 3 denotes a spindle on which the workpiece 4 is mounted.

In this embodiment, the Y axis (vertical axis), which is the rotation axis of the grinding wheel 2, and the Z axis, which is the rotation axis of the workpiece 4, are used.
A grinding method by simultaneous two-axis control of the axis (horizontal axis) was used.

The details will be described below.

(1) Positioning of Grinding Wheel In the cutting of an axisymmetric aspherical surface by a grinding wheel having an arc-shaped cutting edge, the coordinates of the center of the arc serving as the base point for positioning the grinding wheel are calculated as shown in the following equation. Then, processing is performed while performing NC control.

[0023]

(Equation 1)

Where (Y _W , Z _W ) are the coordinates of the workpiece,
(Y ₀ , Z ₀ ) is the center coordinate of the cutting edge circle of the grinding wheel,
R is the radius of curvature of the cutting edge circle of the grinding wheel, and θ is the tangential angle at the processing point.

In the grinding method of the present invention, as shown in FIG. 1 and FIG. 2, in order to create a Fresnel shape with a sharp grinding wheel 2 having a sharp tip 2A, calculation was made with R = 0 in the above equation (1).

(2) Feed Speed Control As shown in FIG. 3, when the grinding wheel 2 is fed in the Y direction while rotating the axisymmetric workpiece 4, the radial position of the workpiece 4 is set to r (mm) and the grinding is performed. Assuming that the rotation speeds of the grinding wheel 2 and the workpiece 4 are ω ₁ and ω ₂ (rpm), respectively, a feed amount F _C (mm / m) in the circumferential direction of the workpiece 4 per one rotation of the grinding wheel 2.
in) is represented by the following equation.

F _C = 2πr · ω ₂ / ω ₁ (2) Assuming that the grinding wheel feed speed is F _Y (mm / min), the grinding wheel 2 moves in the radial direction of the workpiece 4 per rotation of the workpiece 4. The distance F _r (mm / rev) to be moved can be expressed by the following equation.

F _r = F _Y / ω ₂ (3) Next, assuming that the number of working abrasive grains in the area where the workpiece 4 can be contacted is N and the length of an average grinding mark by one abrasive grain is l _W , The pitch P of the abrasive scratches in the circumferential direction on the object 4 is expressed by the following equation.

P = F _C · F _r / N · l _W (4) From the above equations (2), (3) and (4), the following equation is obtained.

P = 2π · F _Y · r / N · l _W · ω ₁ (5) Here, the number N of abrasive grain cutting edges is the working abrasive density δ (/ mm ² ) of the grinding wheel surface, The contact area between the workpiece and the grinding wheel is A (m
m ² ), it is expressed by the following equation.

N = δ · A (6) Here, δ is determined by the hardness of the grinding wheel, the degree of concentration, and the like. If δ and A are constant during processing, N is also constant.

Assuming that the average apex angle of the cutting edge of the abrasive grains protruding from the surface of the grinding wheel is θ and the shape of the abrasive grains is transferred, the surface roughness (R _y ) of the workpiece can be obtained from FIG. ) Can be expressed as:

R _y = (P / 2) cot (θ / 2) (7) From the above equations (5) and (7), the following equation is obtained.

R _y = (π · F _Y · r / N · l _W · ω ₁ ) cot (θ / 2) (8) That is, from this equation, the grinding wheel feed speed F _Y is calculated as in the conventional case.
Is fixed, it can be seen that the surface roughness of the workpiece 4 deteriorates in proportion to the radial position of the workpiece. Therefore, in the method of the present invention, the feed speed F _Y of the grinding wheel 2 was changed as in the following equation.

F _Y (r) = k · P · N · l _W · ω ₁ / 2πr (9) where k is a proportionality constant.

Further, as shown in FIG. 3, the circumferential length L (r) at which the processing point moves on the processing surface during one rotation of the grinding wheel 2 is expressed by the following equation.

L (r) = 2πr · ω ₂ / ω ₁ (10) Here, assuming that the interference area with the workpiece during one rotation of the grinding wheel 2 is A (r), the workpiece 4 in the middle is A (r). Removal amount V
(R) is as follows.

V (r) = L (r) · A (r) (11) From the above equations (10) and (11), the following equation is obtained.

V (r) = 2πr · (ω ₂ / ω ₁ ) · A (r) (12) In the case where the shape of the workpiece 4 is a plane, if the depth of cut is δ, the following relationship is established.

A (r) = F _Y (r) · δ (13) From the above equations (12) and (13), the following equation is obtained.

V (r) = 2πr · (ω ₂ / ω ₁ ) · F _Y (r) · δ (14) From the above equations (9) and (14), the following equation is obtained.

V (r) = k · ω ₂ · δ · P · N · l _W = const (15) That is, since V (r) is constant in this case, the grinding resistance is reduced between the workpiece and the grinding wheel. Assuming that it is proportional to the interference volume (removal rate), it means that the shape accuracy is also improved.

When the radial position r is small, F _Y
Although the value of (r) increases, in the present invention, the feed amount F
_An upper limit is set so that _Y (r) / ω ₁ does not become too large. Here, the upper limit is set to 0.4 mm / min (1.3 μm).
m / rev).

(3) Grinding Apparatus and Grinding System FIG. 5 is a perspective view of a grinding apparatus showing an embodiment of the present invention. The same parts as those shown in FIGS. 1 to 4 are denoted by the same reference numerals, and description thereof will be omitted.

In this figure, 11 is a motor for rotating the main shaft, 12 is a vacuum chuck, 13 is a jig, and 14 is an X-axis.
A Z-axis guide table, 15 is a Y-axis guide table, 16 is a motor for rotating the grindstone shaft 1, and 17 is a coolant nozzle.

As a grinding device, a simultaneous 4-axis (X, Y, Z, C) control processing machine [Toshiba Machine Co., Ltd.] as shown in FIG.
ULG100A (H3)] was used. The main shaft 3 is mounted laterally on the Z-axis guide table, and free-form surfaces can be machined.

Here, the X, Y, and Z axis tables are VV
Rolling guide with needles on the groove surface. Positioning is linear (glass) to suppress fluctuations due to temperature changes.
This is performed by scale feedback control, and the positioning resolution is 1 nm. A Y-axis guide table 15 was mounted on the X-Z-axis guide table 14, and a high-speed rotating grinding spindle was installed on the Y-axis guide table 15. The spindle 3 is an aerostatic bearing having a maximum rotation speed of 3000 rpm, and the grinding spindle has a maximum rotation speed of 4 × 10 ⁴ rpm.
Air static pressure bearing.

The axially symmetric workpiece 4 was attached to the main shaft 3 by a vacuum chuck 12 via a jig 13. At this time, while measuring with an electric micrometer, adjustment was made so as to obtain a coaxiality of ± 0.5 μm or less. Further, a balance weight was attached to the screw holes provided in the main shaft 3 and the grinding wheel shaft 1 so that the unbalance between the main shaft 3 and the grinding wheel 2 was adjusted to 0.1 μm and 0.01 μm or less, respectively. Using the same device, simultaneous Y axis (vertical axis) and Z axis 2
The prototype was manufactured while controlling the axis. The X and C axes were used only when adjusting the origin of the grinding wheel 2.

(4) Diamond Wheel (Whetstone) and Truing Method Thereof In the embodiment of the present invention, a disk-shaped diamond wheel (grindstone) was used as the grinding wheel 2 as shown in FIG.
The tip 2A is sharpened in a knife edge shape with θ (for example, 45 °), and the wheel tip 2A creates a Fresnel shape composed of minute steps. In FIG. 6,
φL ₁ is 70 mm, L ₂ is 3 mm, L ₃ is 3 mm, φL
₄ is 10 mm. In order to finish only by grinding,
In addition, in order to minimize the wear of the grindstone which affects the shape error of the workpiece, a resinoid diamond wheel 2B having an abrasive grain diameter of # 1200 and a relatively coarse grain was used. 2C is a steel pedestal of the wheel.

FIG. 7 is an explanatory view of the truing of the diamond wheel. FIG. 7 (a) is a conceptual diagram of the truing on the side surface of the grinding wheel, and FIG. 7 (b) is a conceptual diagram of the truing of the end grinding wheel surface.

As shown in these figures, the truing of the diamond wheel 2 is performed by connecting the truer 5 to the main shaft 3 on the machine.
And the lower surface and the upper surface (45 ° taper portion) of the diamond wheel 2 were traversed.

Here, the truing conditions are shown in Table 1.

[0053]

[Table 1]

The truer 5 has a straight shape # 200.
Wet processing was performed using a resinoid bonded diamond wheel. The truer 5 was attached to the main shaft 3 by a vacuum chuck via a jig, and adjusted so that a coaxiality of 1 μm or less was obtained while measuring the outer periphery with an electric micrometer. The edge (tip) 2A of the wheel 2 was formed sharply, and the edge 2A was ground.

(5) Grinding Conditions As the mold material, fine-grain cemented carbide WC was used assuming that glass forming was performed. Here, first, a planar workpiece was ground, and the effect of the above (2) [feed speed control] was examined. Finally, a prototype of the Fresnel-shaped mold shown in FIG. 8 was manufactured and verified.

In this embodiment, as shown in FIG. 8, an axially symmetric Fresnel-shaped mold represented by the following equation was prototyped.

Z (Y) = mod {g (Y), b} (16) where Y is the position of the workpiece in the radial direction, Z is the position of the workpiece in the rotation axis direction, and g (Y) is Aspheric function (polynomial), b
Is a step of the groove of the Fresnel lens.

Further, g (Y) is expressed by the following equation, similarly to a general axisymmetric aspheric polynomial function.

[0059]

(Equation 2)

Here, C _V , K, C _i (i = n) are aspheric constants.

In this case, g (Y) is an aspherical surface (effective diameter: about φ4 mm) having an approximate radius of curvature of about 50 mm, and the step b is set to be about 0.005 mm (5 μm). Assuming that a glass press is performed, a fine-grain cemented carbide was used as a mold material.

Table 2 shows the grinding conditions.

[0063]

[Table 2]

The grinding wheel for finishing is # 120
A 0 resinoid bonded diamond wheel was used.
The cut is 2 μm and the feed rate is 0.025 to 0.4.
mm / min.

(6) Surface Grinding The effect of improving the surface roughness and shape accuracy by controlling the wheel feed speed will be verified. In the following, the results in the case of using a flat-shaped cemented carbide for the workpiece are shown.

(A) Surface Roughness FIG. 9 shows the change in surface roughness when surface grinding is performed under the conditions shown in Table 2. Non-contact surface roughness meter (Max manufactured by ZYGO)
inNT) at the radial position of the workpiece. Evaluation area is about 180μm × 160μm
Met. The horizontal axis is the radial position of the workpiece, and the vertical axis is P
-V value corresponds to the maximum height _Ry . The circles indicate that the grinding wheel feed speed was changed from 0.025 to 0.4 mm / min by equation (9), and the black circles indicate that the grinding wheel feed speed was 0.2 μm / m.
It is fixed to in. It can be seen that the surface roughness is improved and uniformized by controlling the wheel feed speed.

(B) Shape Accuracy FIG. 10 shows a shape error curve obtained by measuring the workpiece with a shape measuring machine having a diamond stylus of 2 μm at the tip [UA3P manufactured by Matsushita Electric Industrial Co., Ltd.]. The upper curve “a” is obtained when the feed speed of the grinding wheel is fixed, and the lower curve “b” is obtained by changing the equation (9). When the feed rate is constant, the removal amount V (r) of the workpiece is larger at the outer periphery and smaller at the inner periphery according to the equation (14). As a result, the grinding resistance also varies and the shape error increases. On the other hand, when the feed rate is controlled in accordance with the equation (15), V (r) is constant at the outer peripheral portion and the inner peripheral portion. As a result, it is considered that the grinding resistance is constant and the shape error is reduced. Can be

(7) Grinding Experiment of Fresnel Shape By the grinding method of the present invention, ultra-precision grinding of the mold of the Fresnel lens shown in FIG. 8 was performed, and the possibility of grinding was verified. After the truing of the diamond wheel was performed under the conditions shown in Table 1, grinding was performed under the conditions shown in Table 2 as shown in FIG.

(A) Shape Accuracy FIG. 12 shows the cross-sectional shape measured after performing the primary processing in the above experiment. The shape error curve is 3 under the conditions in Table 2.
The workpiece was removed from the main spindle after the cutting by giving a notch, and measured by a contact type shape measuring device [UA3P manufactured by Matsushita Electric Co., Ltd.] equipped with a diamond stylus having a radius of curvature of 2 μm at the tip and a vertex angle of 60 °. is there. Each step has a step of about 5 μm as designed.

FIG. 13 shows a difference from the target shape calculated by removing the vicinity of the step based on the result, that is, a shape error curve. The shape accuracy was about 2.41 μm PV. This is due to an error in the origin position of the grinding wheel.

Based on the measurement results, the origin position of the diamond wheel is corrected in the Y direction and grinding is performed, and the results obtained by the same measurement method are shown in FIG. About 0.1
A shape accuracy of 1 μm PV is obtained.

FIG. 15 shows a three-dimensional shape measured by a non-contact shape measuring device (NH-3 manufactured by Mitaka Optical Instruments Co., Ltd.).
Shown in It can be seen that a relatively sharp edge is obtained.

Finally, only the step portion of the Fresnel shape after grinding is measured by the above-mentioned contact type shape measuring device, and a cross-sectional curve enlarged and displayed is shown in FIG. A shape error region having a width of about 25 μm exists beside the step portion that looks sharp.
This is considered to be because the tip of the diamond wheel has an arc shape. In order to further reduce the shape error region, it is necessary to improve the truing method of the diamond wheel to further sharpen the shape of the tip.

(B) Surface Roughness FIG. 17 shows the surface roughness measured near the center of the workpiece after grinding. Non-contact surface roughness meter (M made by ZYGO)
axinNT) near the center of the workpiece. Evaluation area is about 180μm × 160μ
m. About the surface roughness of 10NmR _y is obtained, high specularity is obtained.

Finally, when a Nomarski micrograph (not shown) of the ground surface is viewed, very fine abrasive grain scratches are observed on the surface, but it is understood that a processed surface in the ductile mode is obtained. In the conventional aspherical grinding method, the rotation direction of the grinding wheel at the processing point is orthogonal to the rotation direction of the workpiece, but in the grinding method of the present invention, the grinding wheel is positioned parallel to the rotation direction of the workpiece. In a relationship. Therefore, it is considered that the surface roughness tends to be worse than that of the conventional method. However, it has become clear that good surface roughness can be obtained by changing the feed speed of the grinding wheel according to the radial position of the workpiece.

From the above results, it has become clear that the grinding method of the present invention is effective in processing a Fresnel shape made of a hard brittle material such as ceramics.

(8) Result As described above, a fine Fresnel-shaped grinding process composed of a large number of discontinuous curved surfaces is realized, and it becomes possible to mass-produce (press-mold) glass micro Fresnel lenses. To this end, the present invention has developed a grinding system having the following features.

(A) Equipped with a vertical grinding wheel spindle of aerostatic bearing type and a horizontal spindle, and four axes (X,
Y, Z, C) control is possible.

(B) A non-continuous aspheric surface is formed by driving a sharp disk-shaped grinding wheel having a knife-edge shape while simultaneously controlling the Y-axis (vertical axis) and the Z-axis (horizontal axis) simultaneously. Creation of shapes is possible.

(C) It is possible to control the feed speed of the grinding wheel corresponding to the position in the radial direction on the axisymmetric aspherical workpiece.

Using the above-described grinding system, a fine-grain cemented carbide Fresnel shape was ground, and the possibility of grinding was examined. As a result, the following became clear.

(1) When the feed rate is controlled, the surface roughness of the workpiece becomes good, the entire surface is made uniform, and the shape accuracy becomes similarly good.

[0083] (2) As a result of a prototype mold cemented carbide Fresnel shape, surface roughness of the shape accuracy and about 10NmR _y of about 0.1μm is obtained, grinding method of the present invention, the grinding of the Fresnel shape It is valid.

In FIG. 1, a grinding wheel having a sharp knife edge shape may be driven as shown in FIG. That is, not only the Y and Z axes but also the X axis may be combined. In short, the grinding wheel rotation axis and the workpiece rotation axis may be parallel to each other in processing the Fresnel step portion.

The present invention is not limited to the above-described embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0086]

According to the present invention, the following effects can be obtained.

(A) A sharp edge can be precisely machined even at a discontinuous portion of an axisymmetric aspherical component composed of a plurality of discontinuous curved surfaces.

(B) When the feed speed is controlled, the surface roughness of the workpiece becomes good, the entire surface becomes uniform, and the shape accuracy becomes similarly good.

[0089] As a result of trial type cemented carbide Fresnel shape, surface roughness of the shape accuracy and about 10NmR _y of about 0.1μm was obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part showing a grinding apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a grinding method using a grinding apparatus according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a method of controlling a feed speed of a grinding wheel of a grinding apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a feed speed of a grinding wheel and a surface roughness profile of a grinding apparatus according to an embodiment of the present invention.

FIG. 5 is a perspective view of a grinding apparatus showing an embodiment of the present invention.

FIG. 6 is a configuration diagram of a grinding wheel of the grinding apparatus showing the embodiment of the present invention.

FIG. 7 is an explanatory diagram of truing of a diamond wheel showing an embodiment of the present invention.

FIG. 8 is a sectional view of a Fresnel-shaped mold showing an embodiment of the present invention.

FIG. 9 is a view showing the surface roughness of a planar surface at various radial positions showing an embodiment of the present invention.

FIG. 10 is a view showing the surface roughness of a planar surface at various radial positions showing an embodiment of the present invention.

FIG. 11 is a perspective view of an aspherical surface grinding device showing an embodiment of the present invention.

FIG. 12 is a diagram showing a measurement cross section of the Fresnel surface after performing primary processing according to the embodiment of the present invention.

FIG. 13 is a diagram showing a deviation profile after primary grinding showing an example of the present invention.

FIG. 14 is a diagram showing a deviation profile after secondary grinding showing an example of the present invention.

FIG. 15 is a three-dimensional topography of a Fresnel surface showing an embodiment of the present invention.

FIG. 16 is a Fresnel depth profile measured using a stylus device (contact-type shape measuring device) showing an example of the present invention.

FIG. 17 is a surface roughness profile after grinding according to an example of the present invention.

FIG. 18 is a perspective view of a main part showing a grinding apparatus according to another embodiment of the present invention.

FIG. 19 is a view showing an example of a molding process of a conventional glass Fresnel lens.

FIG. 20 is a perspective view showing a conventional grinding apparatus.

FIG. 21 is an explanatory diagram of a grinding method using a conventional grinding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Grinding wheel shaft 2 Sharp knife-edge-shaped grinding wheel 2A Tip 2B Diamond wheel 2C Steel pedestal of wheel 3 Main shaft 4 Workpiece 5 Truer 11 Motor for rotating main shaft 12 Vacuum chuck 13 Jig 14 X-Z axis guide table 15Y Shaft guide table 16 Motor for rotating the grinding wheel shaft 17 Coolant nozzle

Claims (5)

[Claims] 1. An axisymmetric disk-shaped grinding wheel having a sharp pointed end, and the grinding wheel rotating axis of the grinding wheel being orthogonal to a rotating axis of the axisymmetric workpiece, and further being in contact with the workpiece. In a state where the rotation direction of the grinding wheel is arranged so as to be parallel to the rotation direction of the workpiece, the grinding wheel is driven in the radial direction and the rotation axis direction of the workpiece, and an axis configured by a plurality of discontinuous curved surfaces A grinding method characterized by producing a symmetrical aspherical part. 2. The grinding method according to claim 1, wherein
The grinding method, wherein the aspherical component is a hard Fresnel optical component. 3. The grinding method according to claim 2, wherein
The grinding method, wherein the aspherical component is a glass micro Fresnel lens. 4. The grinding method according to claim 1, wherein
A grinding method capable of controlling a feed speed of the grinding wheel. 5. A vertical grinding wheel spindle with an aerostatic bearing and a horizontal spindle, and four axes (X,
A grinding machine controlled by Y, Z, C), wherein (a) an axisymmetric disk-shaped grinding wheel having a sharp tip at the edge of a knife; An axially symmetric workpiece having a rotation axis Z, and (c) the YZ
A grinding device comprising: a simultaneous two-axis control means; and (d) a grinding wheel feed speed control means.