JPH09323353A - Manufacture of microlens array and presser urging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to manufacture a microlens array having excellent diffusibility without directionality. SOLUTION: When dents are formed at a mold base material 5, a presser 1 is rotated at a predetermined angle with respect to the axis of the urging direction of the presser 1 by a motor 3, and then the presser 1 is urged to the surface of the material 5 by a moving coil unit 2. As a result, the dents having irregular distortion directions are formed at the material 5. The dent shapes of the material 5 are transferred to an optical member, and a microlens array having small directivity of a transmitted light is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a microlens array and an indenter pressing device used in the method.

[0002]

2. Description of the Related Art A typical example of using a microlens array is a focusing screen of a single lens reflex camera. FIG.
FIG. 3 is a sectional view showing a basic configuration of a single-lens reflex camera.
The focusing screen 30 is a matte surface 3 including a microlens array.
0a and a Fresnel lens surface 30b having an annular structure. The microlens array is composed of a large number of microlenses, and the light flux reflected by the main mirror 32 after passing through the taking lens 31 is diffused by the matte surface 30a and then by the Fresnel lens surface 30b.
The image forming light beam outside the optical axis of is deflected in the optical axis direction. Focusing screen 3
The light flux diffused by 0 passes through the condenser lens 33 and the pentaprism 34, reaches the finder optical system 35, and is observed by a photographer looking through the finder.

By the way, as a method of manufacturing a microlens array, a method using an indentation method is known. In the indentation method, an indenter is pressed against a mold with a predetermined load to form a large number of indentations (concave surfaces) at predetermined intervals, and the mold is used to perform injection molding, compression molding, cast molding, etc. An array is created. At this time, a large number of indentations are formed on the mold by vertically moving the indenter in the vertical direction and moving the mold in the horizontal direction. Diamond is generally used as the indenter, and the microlens shape is determined by the tip shape of the indenter. Usually, the curvature radius of the microlens required for optical design is multiplied by the transfer coefficient to be used as the curvature radius of the indenter.

[0004]

Generally, the tip shape of the indenter is not an ideal spherical surface, but is actually distorted. As a result, the directions of distortion of the microlens shape are aligned, and in the microlens array manufactured in this way, the light transmitted through the microlens array has directionality, making it difficult to see the focusing screen. There was a flaw. In addition, there is a problem that a state (brightness or darkness) of the subject image viewed by the photographer through the viewfinder optical system and an image actually exposed on the film are deviated.

An object of the present invention is to provide a manufacturing method capable of manufacturing a microlens array having no directivity and good diffusivity, and a manufacturing apparatus used in the manufacturing method.

[0006]

The present inventor diligently studied the cause of the directionality of light transmitted through the microlens array, and found the following points.

FIG. 7 is a view showing the tip portion of the indenter 1,
It is measured by a non-contact shape measuring device using optical interference. In FIG. 7, the z-axis is the axial direction of the indenter 1 (that is, the pressing direction of the indenter), and the curve 101 represents the contour line of the tip of the indenter. The interval between the contour lines is λ / 2 (λ is the wavelength of the light source light). Although the final shape generation of the tip portion of the indenter 1 is all performed by polishing, it is not a perfect spherical surface, and in many cases the shape is distorted due to the partial hardness difference due to the influence of the crystal orientation. If the tip shape of the indenter is a perfect spherical surface, z
The radii of curvature when cross-sectioned in a plane including the axis (plane perpendicular to the paper surface) are the same regardless of the direction of the cross-section. However, when the shape of the tip of the indenter is distorted, the radius of curvature varies depending on the direction of the cross section, as can be seen from the XX ′ cross section and the YY ′ cross section in FIG. 7.

FIG. 8 is a view for explaining a microlens array manufactured by using such a distorted indenter 1. FIG.
(A) is a plan view of the microlens array, and the distortion of the indenter tip shape is transferred to the shape of each microlens 40 formed by transferring the indentation shape of the mold. As can be seen from the state of the contour line 401, the radius of curvature is large on the left side of the figure and large on the right side of the center of the microlens 40. Furthermore, the directions of distortion of the microlenses 40 are aligned in the same direction. FIG.
It is the figure which showed typically the light and dark observed from a finder optical system, when the focusing screen in which the micro lens array shown to (a) was formed is used and a point light source was imaged. Refraction of light is suppressed in a portion having a large radius of curvature of the microlens 40, and conversely, refraction is generated more strongly in a portion having a smaller radius of curvature. Therefore, there is a brightest portion on the left side of the center of the finder, and as it gets farther from it Gradually dark, with extremely dark areas in the upper right and lower right corners.

Therefore, the microlens array of the present invention is constructed as follows. An embodiment of the invention will be described in association with FIG. (1) The invention of claim 1 is a microlens which presses the indenter 1 against the surface of the mold base material 5 to form a plurality of indentations, and transfers the shape of the indentations to an optical member to form a plurality of minute convex curved surfaces. The indenter 1 is applied to an array manufacturing method and is used for forming an indentation.
The above object is achieved by including the step of rotating the indenter 1 by a predetermined angle with respect to the axis of the pressing direction and then pressing it against the surface of the mold base material 5. (2) The invention of claim 2 is applied to a method for manufacturing a microlens array in which a plurality of minute concave curved surfaces are formed by pressing the indenter 1 against the surface of a member to be processed made of an optical material to form minute concave curved surfaces. At this time, the above-described object is achieved by including a step of rotating the indenter 1 by a predetermined angle with respect to the axis of the indenter 1 in the pressing direction and then pressing the indenter 1 against the surface of the workpiece. (3) The invention according to claim 3 is applied to the manufacturing method according to claim 1 or 2, wherein the indenter 1 is rotated by a predetermined angle for each indenter pressing operation. (4) The indenter pressing device according to the invention of claim 4 is the device according to claim 1.
An indenter pressing device used in the manufacturing method according to any one of 1 to 3, wherein the indenter driving device 2 presses the indenter 1 against the die base material 5, and the indenter 1 is rotated about an axis in the pressing direction of the indenter 1. The indenter rotating device 3 and the control means 2 for controlling the indenter rotating device 3 and the indenter driving device 2 so as to press the die base material 5 after rotating the indenter 1 at a predetermined angle when forming each indentation.
0, 22, 23, 24 are provided to achieve the above-mentioned object. (5) According to the invention of claim 5, in the indenter pressing device according to claim 4, the die base material 5 is placed, and the die base material 5 is moved in the moving direction (Z direction) of the indenter 1 by the indenter drive device 2. The control means 2 includes a stage 6 that is driven in a plane (xy plane) orthogonal to each other.
0, 21, 22, 23 and 24 control the indenter rotating device 3 and the indenter driving device 2 in conjunction with the driving of the die base material 5 by the stage 6.

(1) In the invention of claims 1 to 4, when the indenter 1 is pressed against the surface of the die base material 5 or the member to be processed, the indenter 1 is rotated by a predetermined angle and then pressed against the die base material 5. Including the process, the direction of strain of the indentation varies. (2) In the invention of claim 5, the indenter 1 is rotated and pressed in association with the movement of the stage 6.

In the section of the means for solving the above-mentioned problem which explains the constitution of the present invention, the drawings of the embodiments of the present invention are used in order to make the present invention easy to understand. However, the present invention is not limited to the embodiment.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic view of an indenter pressing device for forming an indentation that becomes a mold of a microlens array on a mold base material 5. The die base material 5 is placed on the XY stage 6 by a mechanical method or a fixing method such as adhesion. 7X and 7Y are stage moving motors that drive the XY stage 6, and are controlled by the stage drive circuit 20. 8X and 8Y are digital micrometers that detect the position of the XY stage 6, and the movement amount of the XY stage 6 is detected by the stage movement amount detection circuit 21 based on the outputs of the digital micrometers 8X and 8Y.

Reference numeral 2 is a moving coil device fixed to the body 4 of the indenter pressing device, and its detailed cross section is shown in FIG. The indenter 1 having a conical tip is attached to the shaft 11 of the moving coil device 2. The moving coil device 2 includes a motor 3 for rotating a shaft 11 to which the indenter 1 is attached. The motor 3 is a stepping motor, and the rotation angle indexing circuit 2
The rotation angle is controlled by the number of pulses from 3. 22 is a moving coil drive circuit for driving the shaft of the moving coil device 2 in the vertical direction, 24 is each circuit 20,
It is a computer that gives a predetermined instruction to 21, 22, and 23. Working conditions (rotation angle, indentation pitch, etc.) can be input to the computer 24 by an input device.

In FIG. 2, reference numeral 12 denotes a cylindrical permanent magnet provided so as to be fitted on the shaft 11 and fixed to the base plate 10c. Reference numeral 13 denotes a coil support frame which is attached to the shaft 11 and is provided so as to be externally fitted to the permanent magnet 12, and the coil 14 is wound in an annular shape. Reference numeral 15 denotes an annular permanent magnet provided so as to be externally fitted to the coil 14 and fixed to the base plate 10a.

Reference numerals 9a and 9b are leaf springs, and the base end of the leaf spring 9a is fixed to a block 17 fixed to a base plate 10c by a pressing plate 17a and bolts. Leaf spring 9
The tip of a is connected to the shaft 11 by being sandwiched between the pressing plate 16a and the block 16 together with the connecting ring 18 integrated with the shaft 11 by the pin 18a. On the other hand, the base end of the leaf spring 9b is fixed to the block 17 fixed to the base plate 10a by a holding plate 17a and bolts. The tip of the leaf spring 9b has a connecting ring 18
At the same time, it is connected to the shaft 11 by being sandwiched between the pressing plate 13 a and the support frame 13. Therefore,
The shaft 11 is elastically supported by leaf springs 9a and 9b so as to be capable of reciprocating along a vertical line, but the shaft 11 itself can rotate. The upper end of the shaft 11 is connected to the indenter rotating motor 3 via a joint 19. Since the joint 19 has rigidity in the rotational (radial) direction and has a flexible structure in the vertical (thrust) direction, the rotation of the motor 3 is transmitted to the shaft 11, but the vertical movement of the shaft 11 does not occur. It is not transmitted to the motor 3.

Next, the details of the shaft drive portion of the moving coil device 2 will be described with reference to FIG. As shown in FIG. 3, the lower part of the permanent magnet 15 has an S pole and the upper part has an N pole.
The lower part of the permanent magnet 12 is magnetized to the N pole and the upper part is magnetized to the S pole, and the direction of the magnetic force line is vertically downward on the central axis of the shaft 11 as shown by an arrow B. Here, when an electric current is applied so that the magnetic force lines generated in the coil 14 are directed vertically downward as indicated by an arrow B on the central axis of the shaft 11, a vertically downward force is exerted on the coil 14 to move the shaft 11 vertically downward. Moving. On the other hand, when a reverse current is applied to the coil 14, a force vertically upward acts to move the shaft 11 vertically upward. The moving coil drive circuit 22 has a variable pulse current generator, and outputs a pulse-wave-shaped current whose polarity changes periodically to the coil 14 to output the indenter 1.
Can be moved up and down at high speed. The vertical movement cycle can be set to 0.1 to 50 Hz. The upper and lower strokes are about 50 μm. Further, the pressing force of the indenter 1 can be changed by changing the magnitude of the current supplied to the coil 14. In addition, the XY stage 6,
The moving coil device 2 and the motor 3 are controlled by the circuits 20 to 23 based on a command from the computer 24.

FIG. 4 is a flow chart showing an example of a mold manufacturing process, and a method of manufacturing a microlens array mold by an indenter pressing device will be described with reference to FIGS. 4 and 1. In the flowchart of FIG. 4, the indentation size α is 20 μm.
The explanation is given assuming the case. First, the mold base material 5 is X
It is started by fixing it on the Y stage 6 and pressing the start button of the device. After the indenter 1 is rotated by a predetermined angle (in the present embodiment, rotated clockwise by 1.8 degrees) by the motor 3 in step S1, the process proceeds to step S2 and the indenter 1 is applied to the die base material 5 with a predetermined force. Press. Step S
Step 3 is a step of determining whether or not all the indentations for one row in the x direction shown in FIG. 1 have been formed, and if not completed, the process proceeds to step S5. Step S5 is a step of determining whether or not the indentation formed in step S2 is an odd-numbered row in the y direction, and in the case of an odd-numbered row, step S5.
After setting d = 20 in step 6, the XY stage 6 is set in step S8.
Is moved in the x direction by dμm (that is, 20 μm). On the other hand, if it is determined in step S5 that the number of columns is an even number, the flow advances to step S7 to set d = -20, and then the flow advances to step S8 to move the XY stage 6 in the x direction to dμm, that is, −x.
The XY stage 6 is moved by 20 μm in the direction.

On the other hand, if it is determined in step S3 that the formation of the indentation for one row is completed, the process proceeds to step S4.
Step S4 is a step of determining whether or not formation of all the indentations is completed. If not completed, the process proceeds to step S9, in which the indentation is formed on the XY stage 6 in the y direction by about 3 ^{1 / of the} size α. ^2/2-fold (approximately 17.32Myuemu) only by moving further -1/2 times the size α of the indentation in the x direction (1
0 μm). Then, returning to step S1, the above-described operation is repeated, and when the formation of all the indentations is completed, a series of operations is ended. In this way, the spacing 20
A mold with a large number of indentations formed in μm is produced. As the mold material for the microlens array, martensitic stainless steel, which is a crystalline material, is used, and the indented surface is mirror-finished by metal polishing in advance. Moreover, diamond is suitable for the indenter material.

Although the rotation angle is set to 1.8 degrees in this embodiment, for example, when 200 microlenses 40 are formed in one row, 1.8 degrees × 200 = 360.
Since it is the degree, the arrangements of the first line, the second line, the third line, ... Are all the same. Therefore, the rotation angle is determined according to the number of vertical and horizontal microlenses 40 so that the entire directivity does not occur with periodicity for each row or each column. Further, the indenter is rotated by a predetermined angle for each indentation, but the indenter may be rotated for every plural indentations such as every two indentations as long as the directionality is not generated. Further, the indenter may be rotated by a random angle for each pressing, instead of rotating by a constant angle.

FIG. 5 is a view for explaining a microlens array manufactured by a known method using the mold manufactured as described above, and is a view similar to FIG. 7 described in the prior art. , The case where the rotation angle of the indenter is random is shown. As can be seen from FIG. 5A, since the indenter 1 is rotated by a predetermined angle every time the indentation is formed, the strain directions of the individual microlenses 40 are random without being aligned in a fixed direction. As a result, since the diffused light from the microlens array has no directivity, when this microlens array is used as the focusing screen, the bright portion is located at the center of the finder as shown in FIG. 5B. , A symmetry that darkens as you move away from the center. That is, it is possible to obtain a focusing screen that is uniform in the vertical and horizontal directions with respect to the center. Further, conventionally, it was necessary to select and use an indenter having a very small strain, but according to the present embodiment, there is no such need, so that the manufacturing cost can be reduced. Furthermore, when changing the working conditions (rotation angle, pitch of the impression, etc.), it is only necessary to change the data input to the computer 24.

In the above-described embodiment, the shape of the indentation formed on the die base material 5 is transferred to the optical member to manufacture the microlens array, but the indentation is formed on the optical member using the indenter pressing device described above. It may be formed directly. In this case, the microlens array has a large number of minute concave curved surfaces, but has the same diffusivity as the microlens array having a minute convex curved surface manufactured by using a mold.

In the correspondence between the above-described embodiment of the invention and the matters in the claims, the moving coil device 2 constitutes an indenter driving device, and the motor 3 constitutes an indenter rotating device. Is the stage drive circuit 2
0, a moving coil drive circuit 22, a rotation angle indexing circuit 23, and a computer 24.
The control means in is composed of a stage drive circuit 20, a stage movement amount detection circuit 21, a moving coil drive circuit 22, a rotation angle indexing circuit 23 and a computer 24.

[0023]

As described above, according to the present invention,
Before pressing the indenter against the surface of the mold base material or the workpiece,
Since the indenter is rotated by a predetermined angle each time, the direction of strain of the indentation varies, so a microlens array made by using the mold base material as a mold or a microlens array formed from the processed member has a directivity of transmitted light. Is small and the diffusivity is improved. Further, unlike the conventional case, an indenter having no distortion and good shape accuracy is not required, so that manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of an indenter pressing device.

FIG. 2 is a sectional view showing details of a moving coil device 2.

FIG. 3 is a diagram for explaining the operation of the moving coil device 2.

FIG. 4 is a flowchart showing a mold manufacturing process.

FIG. 5 is a diagram illustrating a microlens array,
(A) is a plan view of a microlens array, (b) is the figure which showed typically the light and dark observed from a finder optical system.

FIG. 6 is a sectional view of the camera.

FIG. 7 is a diagram illustrating a tip shape of an indenter.

8A and 8B are diagrams illustrating a conventional microlens array, FIG. 8A is a plan view of the microlens array, and FIG. 8B is a diagram schematically showing light and darkness observed from a finder optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Indenter 2 Moving coil device 3 Motor 5 Mold base material 6 XY stage 20 Stage drive circuit 21 Stage movement amount detection circuit 22 Moving coil drive circuit 23 Rotation angle indexing circuit 24 Computer

Claims (5)

[Claims] 1. A method of manufacturing a microlens array, wherein an indenter is pressed against the surface of a die base material to form a plurality of indentations, and the shape of the indentations is transferred to an optical member to form a plurality of minute convex curved surfaces. A method of manufacturing a microlens array, which comprises the step of rotating the indenter by a predetermined angle with respect to an axis in the pressing direction of the indenter and then pressing the indent on the surface of the die base material when forming the indentation. 2. A method of manufacturing a microlens array in which an indenter is pressed against the surface of a member to be processed made of an optical material to form a plurality of minute concave curved surfaces, the pressing of the indenter when forming the minute concave curved surfaces. A method of manufacturing a microlens array, comprising the step of rotating the indenter by a predetermined angle with respect to the axis of the direction and then pressing the indenter against the surface of the member to be processed. 3. The method of manufacturing a microlens array according to claim 1, wherein the indenter is rotated by a predetermined angle for each indenter pressing operation. 4. An indenter pressing device used in the manufacturing method according to claim 1, wherein the indenter driving device presses the indenter against the die base material or the member to be processed, and An indenter rotating device that rotates the indenter about an axis in the pressing direction, and when forming each indentation or each minute concave curved surface, presses the die base material or the workpiece after rotating the indenter by a predetermined angle. An indenter pressing device comprising: control means for controlling the indenter rotating device and the indenter driving device. 5. The indenter pressing device according to claim 4, wherein the die base material or the processed member is placed, and the die base material or the processed member is orthogonal to a moving direction of the indenter by the indenter driving device. An indenter, characterized in that the control means controls the indenter rotating device and the indenter driving device in conjunction with the driving of the die base material or the processed member by the stage. Pressing device.