JP2004148454A - Method and device for grinding forming die of micro lens array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinding method for precisely grinding a forming die of a micro lens array constituted by aggregating many micro lenses. <P>SOLUTION: A workpiece is mounted on a workpiece spindle and grinding stone provided on a grinding spindle installed at a right angle or inclined to a rotary shaft of the workpiece spindle is pressed on the workpiece. The grinding stone is turned in the same direction as rotation of the rotating workpiece and at the same speed, while keeping a distance between the rotary shaft of the workpiece spindle and a center of a machining point of the workpiece constant, to machine a spherical shaped hole of a concave surface. <P>COPYRIGHT: (C)2004,JPO

Description

【００１７】
【数２】

工作物主軸の任意の回転角Ｃ_ｉｊにおける研削砥石の座標（Ｘ_ｉｊ，Ｙ_ｉｊ）は次式で表される。
【００１８】
【数３】

従って、上記式（１）（２）（３）を満たすように、研削砥石をＺ方向に切り込むように研削砥石を同時４軸（Ｘ、Ｙ、Ｚ、Ｃ）制御すればよい。上記の制御は図示せぬコンピュータ等の制御手段により行う。
【００１９】
用いる研削砥石形状について図７により説明する。
工作物スピンドル４の回転軸と研削スピンドル２の回転軸（研削砥石２の回転軸）がなす角度が直角の場合は、図７（ａ）（ｂ）に示すように研削砥石として円盤状の砥石、楕円体状の砥石および球状の研削砥石を用いればよい。工作物スピンドル４の回転軸と研削スピンドル２の回転軸（研削砥石２の回転軸）がなす角が４５度の場合は、図７（ｃ）（ｄ）に示すように円柱状の砥石、楕円体状および球状の砥石を用いればよい。いずれも工作物は高精度な球面（凹面）となる。
【００２０】
続いてマイクロレンズアレイの成形型の研削方法を行う際の条件について説明する。
工作物にガラスレンズ成形材料である超硬合金に同形状を研削加工した事例で説明する。研削スピンドルには最大１０万ｒｐｍの空気静圧軸受けを用い４５度傾斜させ、砥石は外径１．６ｍｍのダイヤモンド砥石を球状に成形して用いた。工作物上のレンズアレイの各ピッチはΔＸ＝１．０ｍｍ、ΔＹ＝１．０ｍｍとし、レンズ数は５×３（計１５個）とした。曲率半径は０．８ｍｍとした。マイクロレンズアレイ成形型の３次元トポグラフィーと、加工後に非接触表面粗さ計で測定した結果を図８に示す。この結果からも判るように高精度なマイクロレンズアレイ成形型が得られる。
【００２１】
以上本発明に係る実施形態について説明したが、被加工材は上記した超硬合金に限定されることなく、種々の材料を対象とすることができる。また研削砥石もダイヤモンド砥石に限定されることはない。また研削砥石をＸ軸とＹ軸を同時制御して円弧形状に軌跡を描かせながら駆動する機構も種々の機構を採用することができる。
さらに、本発明はその精神または主要な特徴から逸脱することなく、他のいかなる形でも実施できる。そのため、前述の実施形態はあらゆる点で単なる例示にすぎず限定的に解釈してはならない。
【００２２】
【発明の効果】
以上の説明から明らかなように、本発明によれば、工作物を主軸（工作物スピンドル）に取りつけ、その主軸の回転軸に対して直角または傾斜させて設置した研削スピンドルに設けた研削砥石を工作物に押しつけ、さらに、主軸の回転軸と工作物の加工点の中心との距離を一定に保ちながら、回転する工作物の回転と同じ方向で、かつ、同じ速度で研削砥石を旋回させて凹面の球面形状の穴を精密加工し、さらに、工作物上の位置を変えて上記一連の動作を複数回繰り返すことを特徴とするため、マイクロレンズアレイ成形型を高精度に、良好な表面粗さに、良好なピッチ精度に精密研削することができる。
【図面の簡単な説明】
【図１】本発明に係るマイクロレンズアレイの成形型の研削方法に用いる装置の構成図である。
【図２】図１の装置の工作物と砥石の拡大図である。
【図３】目標工作物（マイクロレンズアレイの成形型）の形状の例
【図４】マイクロレンズアレイにおける一つの球面形状（凹面）の穴を高精度に加工するための原理図（３次元図）である。
【図５】工作物の回転軸方向からみた正面図である。
【図６】砥石の軌跡の説明図である。
【図７】砥石形状の図である。
【図８】マイクロレンズアレイ成形型加工結果の例である。
【図９】従来の代表的なマイクロレンズアレイ成形型の精密加工方法の説明図である。
【符号の説明】
１ 工作物
１ａ 工作物の回転基準
２ 研削砥石
３ 研削スピンドル
４ 主軸（工作物スピンドル）
５ 主軸モータ
６ Ｘ軸テーブル
７ Ｙ軸テーブル
８ Ｚ軸テーブル
９ 研削痕（球面状の穴）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a precision machining method for machining a workpiece having a complicated shape composed of a large number of concave spherical surfaces with high precision, and particularly relates to a mold for a microlens array formed by aggregating a large number of microlenses. The present invention relates to a grinding method and an apparatus therefor that precisely grinds steel.
[0002]
[Prior art]
A microlens array composed of a large number of microlenses is capable of increasing the amount of information transmitted and achieving finer exposure in next-generation semiconductor exposure equipment. Expected.
2. Description of the Related Art In recent years, the capacity of information transmission of optical communication devices has been increased, and miniaturization of exposure in next-generation semiconductor exposure apparatuses has been advanced. Promising for realizing this is a microlens array in which a large number of microlenses are aggregated. In order to mass-produce this microlens array precisely, it is necessary to mass-produce it by injection molding or a glass press method using a microlens array lens mold in which a large number of concave-shaped holes are aggregated. As this important microlens array mold, those described in Patent Literature 1 and Non-Patent Literature 1 are conventional representative precision processing methods.
[0003]
[Patent Document 1] JP-A-12-246614 (Claim 1)
[Non-Patent Document 1] Proceedings of the 2001 Precision Society Academic Lectures, 139 pages
In the method described in Patent Document 1, only a soft metal material mold can be mirror-finished, and a large amount of processing time is required when a large number of lens holes are machined because the entire surface is scanned along the shape of the hole. There are problems such as.
[0005]
In addition, to summarize the processing method disclosed in Non-Patent Document 1, as shown in FIG. 9, the work surface of the workpiece is divided into a grid pattern at a pitch of ΔX and ΔY, and By linearly interpolating so as to pass through the point, the round bit whose tip is formed in an arc shape is driven in the X direction. Further, the cutting tool is similarly driven in the X direction by giving a feed of ΔY, and a series of these scans is repeated to create a large number of lens shapes. At this time, since the cutting point moves in an arc shape on the cutting edge of the round tool, a complicated tool locus is calculated in consideration of the radius of the cutting edge of the round tool and the rake angle of the tool when the cutting edge becomes an arc shape. There is a need. Further, in this conventional method, since a single-crystal diamond tool is used as a tool, only a mold of a metal material can be mirror-finished, and only a plastic having a low molding temperature is possible as a molded lens material. In addition, there is a problem that an enormous processing time is required for scanning the entire surface.
[0006]
[Problems to be solved by the invention]
In the future, microlens arrays will be able to increase the amount of information transmitted and to achieve finer exposure in next-generation semiconductor lithography equipment. . In order to develop such a device and increase its precision, it is necessary to develop a precision processing method (grinding method) for precisely processing a mold for forming a microlens array in which a large number of microlenses are aggregated. However, in the conventional method, only a metal can be processed, and a glass lens having a high melting point cannot be formed, and only a plastic having a low melting point can be formed. In addition, there is a problem that an enormous processing time is required for scanning the entire surface.
[0007]
Accordingly, an object of the present invention is to provide a method and an apparatus for grinding a mold for a microlens array composed of a plurality of concave surfaces (spherical surfaces) used for molding a microlens array, and to solve the above problems. And
[0008]
According to the present invention, a grinding wheel provided on a grinding spindle installed at a right angle or at an angle to a rotation axis of a workpiece spindle is pressed against a workpiece, and a distance between the rotation axis of the workpiece spindle and the center of a processing point of the workpiece is adjusted. While maintaining a constant, in the same direction as the rotation of the rotating workpiece, and at the same speed, the grinding wheel is turned to precisely machine a concave spherical hole. The micro lens array mold composed of multiple concave surfaces (spherical surfaces) used to mold the array is processed with high precision, that is, the shape precision (sphericity), surface roughness, and the pitch between each lens are processed with high precision. can do.
[0009]
[Means for Solving the Problems]
For this reason, the technical development means adopted by the present invention are:
The workpiece is mounted on the workpiece spindle, and the grinding wheel provided on the grinding spindle installed at right angles or at an angle to the rotation axis of the workpiece spindle is pressed against the workpiece. While maintaining a constant distance to the center of the processing point, in the same direction as the rotation of the rotating workpiece, and, at the same speed, turning the grinding wheel to process a concave spherical hole. This is a method of grinding a mold for a microlens array.
Further, there is provided a grinding method of a mold for a microlens array, wherein a plurality of concave surfaces are formed by repeating a series of operations a plurality of times while changing the position of a workpiece, in the hole machining.
Further, when the angle between the rotation axis of the workpiece spindle and the rotation axis of the grinding spindle is a right angle, the grinding wheel may be ground using one of a disk-shaped or spherical grinding wheel as the grinding wheel. This is a method of grinding a molding die for a microlens array, which is a feature.
Further, when the angle between the rotation axis of the workpiece spindle and the rotation axis of the grinding spindle is 45 degrees, the grinding wheel uses one of a columnar, elliptical, or spherical grinding wheel as the grinding wheel. This is a method of grinding a mold for a microlens array, characterized in that grinding is performed.
Further, there is provided a method of grinding a mold for a microlens array, characterized in that free abrasive grains are added between the grinding wheel and the workpiece.
Also, a work spindle for holding the work, a grinding spindle that can be arranged at right angles or at an angle to the rotation axis of the work spindle, and pressing against the work with the grinding spindle attached. A grinding wheel that can rotate, while the grinding spindle maintains the grinding wheel at a constant distance between the rotation axis of the workpiece spindle and the center of the processing point of the workpiece, and in the same direction as the rotation of the rotating workpiece, and And a grinding device for forming a microlens array, wherein the grinding wheel can be turned at the same speed.
Further, the grinding spindle is provided on a table that moves the grinding spindle in the X-axis direction, the Y-axis direction, and the Z-axis direction.
[0010]
Embodiment
DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an apparatus used for a method of grinding a mold for a microlens array according to the present invention, and FIG. It is an enlarged view.
In the figure, reference numeral 1 denotes a workpiece serving as a mold for a microlens array after finishing, 1a denotes a rotation reference of the workpiece, 2 denotes a grinding wheel, 3 denotes a grinding spindle on which the grinding wheel 2 is mounted, and 4 denotes a main spindle on which the workpiece 1 is mounted. (Workpiece spindle), 5 is a spindle motor, 6 is an X-axis table that drives the rotating grinding wheel and the grinding spindle in the X-axis direction, 7 is a Y-axis table, 8 is a Z-axis table, and 9 is a processing by the grinding wheel 2. Grinding marks (holes). The workpiece 1 that is to be a mold for the microlens array is mounted on the main shaft 4 and is finished.
[0011]
FIG. 3 shows an example of the shape of a target workpiece, which is the shape of a microlens array mold. A hole 9 having a spherical shape (concave surface) is formed in the workpiece 1. The pitch in the X-axis direction is ΔX, and the pitch in the Y-axis direction is ΔY. Each of these holes becomes a lens type. Here, as shown in FIG. 3, the processing of a microlens array mold in which 5 × 3 rows (15 in total) of lens molds are aggregated is taken as an example. However, the present invention is not limited to this number. The setting of the workpiece is attached to the main shaft 4 based on the rotation reference 1a of the workpiece.
[0012]
The processing principle of a microlens array mold in which a number of spherical (concave) holes are dug at a pitch ΔX in the X-axis direction and a pitch ΔY in the Y-axis direction using the above apparatus will be described. FIG. 4 is a principle view (three-dimensional) for processing one hole of a spherical shape (concave surface) in the microlens array with high precision, and FIG. 5 is a front view seen from the rotation axis direction of the workpiece. The working principle will be described with reference to FIG.
[0013]
As the main shaft (rotation direction C direction) 4 rotates, the workpiece 1 also rotates. In response, the grinding wheel 2 is also driven while simultaneously controlling the X axis and the Y axis to draw a locus in an arc shape. Here, the drive is performed while synchronizing the rotation of the processing mark (spherical hole) with the rotation of the workpiece so that the driving trajectory of the grinding wheel coincides. At the same time, by providing a cut in the Z-axis direction, the spherical hole can be processed with good sphericity and good surface. In addition, it is possible to perform grinding with higher precision by adding free abrasive grains between the grinding wheel and the workpiece by appropriate means.
[0014]
Such a hole machining is equivalent to cutting in the Z-axis direction while turning the grinding wheel when one machining mark (spherical hole) is centered, and the cutting direction of the abrasive grains on the grinding wheel is 360. Very good surface roughness is obtained due to the degree of movement. In the same manner, the same scanning is repeated while changing the positions of the grinding wheel and the workpiece to form a large number of processing marks (spherical holes), and the microlens array mold is processed with high precision.
[0015]
The locus of the grinding wheel will be described mathematically with reference to FIG.
In a certain (i, j) th machining mark (spherical hole) on the workpiece, if the coordinates based on the rotation reference 1a of the workpiece are (X _oi , Y _oji ), the rotation on the main axis The radius r _ij and the rotation angle C _oij are represented by the following equations.
[0016]
(Equation 1)

[0017]
(Equation 2)

The coordinates (X _ij , Y _ij ) of the grinding wheel at an arbitrary rotation angle C _ij of the workpiece spindle are represented by the following equation.
[0018]
[Equation 3]

Therefore, the grinding wheel may be simultaneously controlled in four axes (X, Y, Z, C) so that the grinding wheel is cut in the Z direction so as to satisfy the above expressions (1), (2), and (3). The above control is performed by control means such as a computer (not shown).
[0019]
The shape of the grinding wheel used will be described with reference to FIG.
When the angle between the rotation axis of the workpiece spindle 4 and the rotation axis of the grinding spindle 2 (the rotation axis of the grinding wheel 2) is a right angle, a disk-shaped grinding wheel is used as the grinding wheel as shown in FIGS. An ellipsoidal grinding wheel and a spherical grinding wheel may be used. When the angle formed by the rotation axis of the workpiece spindle 4 and the rotation axis of the grinding spindle 2 (the rotation axis of the grinding wheel 2) is 45 degrees, as shown in FIGS. Body-shaped and spherical grinding wheels may be used. In each case, the workpiece becomes a highly accurate spherical surface (concave surface).
[0020]
Next, conditions for performing the method of grinding the mold for the microlens array will be described.
An example in which the same shape is ground on a cemented carbide as a glass lens molding material on a workpiece will be described. The grinding spindle used was an air static pressure bearing of 100,000 rpm at the maximum and was inclined at 45 degrees, and the grinding stone was a spherical diamond grinding stone with an outer diameter of 1.6 mm. Each pitch of the lens array on the workpiece was ΔX = 1.0 mm, ΔY = 1.0 mm, and the number of lenses was 5 × 3 (15 in total). The radius of curvature was 0.8 mm. FIG. 8 shows the three-dimensional topography of the microlens array mold and the results of measurement using a non-contact surface roughness meter after processing. As can be seen from this result, a highly accurate microlens array mold can be obtained.
[0021]
Although the embodiment according to the present invention has been described above, the work material is not limited to the above-mentioned cemented carbide, but may be any of various materials. Also, the grinding wheel is not limited to the diamond wheel. Also, various mechanisms can be employed for driving the grinding wheel while simultaneously controlling the X axis and the Y axis to draw a locus in an arc shape.
Furthermore, the present invention may be embodied in any other form without departing from its spirit or essential characteristics. Therefore, the above-described embodiment is merely an example in all aspects and should not be interpreted in a limited manner.
[0022]
【The invention's effect】
As is apparent from the above description, according to the present invention, a workpiece is mounted on a spindle (a workpiece spindle), and a grinding wheel provided on a grinding spindle installed at right angles or at an angle to a rotation axis of the spindle is provided. Pressing against the workpiece and further turning the grinding wheel in the same direction as the rotation of the rotating workpiece and at the same speed, while keeping the distance between the rotation axis of the main spindle and the center of the processing point of the workpiece constant It is characterized by precision machining of a concave spherical hole and repetition of the above series of operations multiple times by changing the position on the workpiece. In addition, precision grinding can be performed with good pitch accuracy.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an apparatus used for a method of grinding a mold for a microlens array according to the present invention.
FIG. 2 is an enlarged view of a workpiece and a grindstone of the apparatus of FIG.
FIG. 3 shows an example of a shape of a target workpiece (a mold for forming a microlens array). FIG. 4 is a principle diagram (three-dimensional diagram) for processing one spherical (concave) hole in the microlens array with high accuracy. ).
FIG. 5 is a front view of the workpiece viewed from a rotation axis direction.
FIG. 6 is an explanatory diagram of a locus of a grindstone.
FIG. 7 is a diagram of a grindstone shape.
FIG. 8 is an example of a processing result of a microlens array molding die.
FIG. 9 is an explanatory view of a precision processing method of a conventional typical microlens array molding die.
[Explanation of symbols]
Reference Signs List 1 Workpiece 1a Workpiece rotation reference 2 Grinding wheel 3 Grinding spindle 4 Spindle (workpiece spindle)
5 Spindle motor 6 X-axis table 7 Y-axis table 8 Z-axis table 9 Grinding marks (spherical holes)

Claims (7)

The workpiece is mounted on the workpiece spindle, and the grinding wheel provided on the grinding spindle installed at right angles or at an angle to the rotation axis of the workpiece spindle is pressed against the workpiece. While maintaining a constant distance to the center of the processing point of the same, in the same direction as the rotation of the rotating workpiece, and, at the same speed, turning the grinding wheel to machine a concave spherical hole. Grinding method for forming mold of micro lens array. 2. The method according to claim 1, wherein a plurality of concave surfaces are formed by repeating a series of operations a plurality of times while changing the position of the workpiece. The grinding wheel is characterized in that when the angle between the rotation axis of the workpiece spindle and the rotation axis of the grinding spindle is a right angle, the grinding is performed using one of a disk-shaped or spherical grinding wheel as the grinding wheel. 3. The method for grinding a mold for a microlens array according to claim 1 or claim 2. When the angle between the rotation axis of the workpiece spindle and the rotation axis of the grinding spindle is 45 degrees, the grinding wheel is ground using one of a columnar, elliptical, or spherical grinding wheel as the grinding wheel. The method for grinding a mold for a microlens array according to claim 1, wherein the grinding is performed. The method for grinding a mold for a microlens array according to any one of claims 1 to 4, wherein processing is performed by adding loose abrasive grains between the grinding wheel and the workpiece. A workpiece spindle for holding the workpiece, a grinding spindle which can be arranged at right angles or at an angle to the rotation axis of the workpiece spindle, and a grinding which can be pressed against the workpiece while being mounted on the grinding spindle A grinding wheel, wherein the grinding spindle holds the grinding wheel in the same direction as the rotation of the rotating workpiece while maintaining a constant distance between the rotation axis of the workpiece spindle and the center of the processing point of the workpiece. A micro-lens array forming die grinding apparatus characterized in that the grinding wheel can be turned at a high speed. The grinding apparatus according to claim 6, wherein the grinding spindle is provided on a table that moves the grinding spindle in the X-axis direction, the Y-axis direction, and the Z-axis direction.

Images