JP2001255138A - Measurement jig - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement jig that enables to accurately measure for a three-dimensional freely curved surface. SOLUTION: The measurement jig, which measures the shape of a measured object 7 by a three-dimensional measurement instrument, comprises a jig body 22 and three globes 1, 2, 3 that are placed on the jig body 22 and measure the shape of the object 7, with the center position of body 22 as a reference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position of an optical surface of an optical component having a plurality of optical surfaces in one optical system, or an optical mirror surface formed on a mold when the optical component is manufactured by a molding method. The present invention relates to a measuring jig for accurately measuring a position.

[0002]

2. Description of the Related Art As a method of determining the position of an optical surface of an optical component having a plurality of optical surfaces, one of methods that has been known for a long time is a lens centering method. If the surfaces that make up the lens are spherical, the line connecting the centers of the respective spheres will be the optical axis, so by reshaping the outer diameter so that the outer diameter does not swing with respect to the optical axis, The center is the position of the optical surface.

However, when the optical surface is an asymmetrical three-dimensional free-form surface, there is no method for accurately measuring the position of the curved surface, and in the die machining, the curved surface position is indirectly determined to process the molded surface.

That is, in FIG. 3, a block 40 is fixed on a table of a machine tool so that its position can be accurately reproduced as an object obtained by precisely grinding six surfaces. For example, a stopper is previously set on a table, and the block 40 is fixed there. A tool (diamond cutting tool) 4 for machining a three-dimensional free-form surface is provided on the spindle 45 of the machine tool.
1 is set in advance, and the main shaft is rotated at a position away from the block 40. The X and Y scales of the machine tool may be set at arbitrary positions, but note the position scales to be machined.
Then, the distance between the block 40 and the cutting tool on the rotating main spindle is gradually reduced to cut the block 40.

FIG. 4 is a plan view after the block 40 has been cut (a view in which the cut surface is viewed from above), in which an elliptical shape 42 is processed. X1, x2 and y of this shape
By measuring 1, y2, the center position of the cutting tool turning on the main axis is x = (x1 + x2) ÷ 2, y =
(Y1 + y2) ÷ 2.

The free-form surface is machined to a desired position by moving the difference between the numerical value of the center position of the cutting tool thus obtained and the position of the three-dimensional free-form surface to be machined in the x and y directions. can do.

[0007]

However, in the above-described method of the prior art, since the processed three-dimensional free-form surface is not directly measured, the block 40 is cut and then subjected to, for example, thermal displacement of a machine tool. May affect the workpiece and change its position. It is also unclear whether the workpiece is accurately attached to the stopper with good reproducibility. Further, the moving axis of the processing machine also has an inherent moving error or the like. Due to these factors, there is a problem that a three-dimensional free-form surface is not always processed at an accurate position. To solve this problem, it is necessary to directly measure a three-dimensional free-form surface.

Accordingly, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a measuring jig capable of accurately measuring a three-dimensional free-form surface.

[0009]

Means for Solving the Problems To solve the above-mentioned problems,
In order to achieve the object, the measuring jig according to the present invention includes:
A jig for measuring a shape of an object to be measured with a three-dimensional measuring machine, the jig main body being disposed on the jig main body,
It is characterized by comprising three spheres for measuring the shape of the object to be measured with reference to the center position.

In the measuring jig according to the present invention, a high-precision ball bearing having a diameter of 2 to 10 mm is used for the three spheres.

Further, in the measuring jig according to the present invention, the three spheres are fixed to the jig body directly or at the tip thereof via a set screw with an adhesive. I have.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, an outline of an embodiment will be described.

A measuring machine for a three-dimensional free-form surface (hereinafter referred to as a measuring machine) uses a high-precision steel ball or a ball made of sapphire at the tip of a measuring probe. The movement of the measurement probe can be moved by NC control with respect to the X and Y axes, but the movement accuracy is not so high. Approx. ± 0.01mm
It is about. However, it is possible to measure the current position accurately (± 1 nm) using other means. Servo control is performed in the Z direction so that the measurement probe contacts the surface to be measured with a weak contact pressure, so that the measurement probe position (z direction) can be measured accurately (± 1 nm). This measurement accuracy can be achieved by utilizing the interference of the laser beam reflected by the hyper-flat mirror, but depends on the flatness of the hyper-flat mirror.

Therefore, the measuring machine travels along the curved surface at a position separated from the curved surface by the radius of the sphere at the tip of the probe, so that the curved surface shape and its position can be accurately measured in the coordinate system of the measuring machine. I can do it. Therefore, three spheres are used to know the relationship between the coordinate system of the measuring device and the coordinate system of the device under test.

Further, since the three spheres require high precision sphericity, a high precision ball bearing is used, and the diameter of the two spheres is 2 to 2 from the viewpoint of easy measurement and easy attachment to a jig. 10 mm is suitable.

Further, for attachment to a measuring jig,
There is a need for a method of fixing the sphere directly to the measuring jig with an adhesive, or fixing the sphere with an adhesive on the side opposite to the side on which the screw is formed, and fixing it to the jig.

FIG. 1 shows a state in which an object to be measured is attached to a jig for measuring the position of an optical mirror surface using three spheres.

The perpendicularity, flatness, and surface roughness of the surface, which serve as references when producing the measuring jig, are produced with as high accuracy as possible. In this example, the bottom surfaces in contact with the reference surfaces 5 and 6 and the base upper surface 4 are:
Squareness 0.0005mm / 30mm or less, flatness 0.0
003 mm and a surface roughness of 0.02 μm rms. The base upper surface 4 is also processed to a flatness of 0.0003 mm or less. Three spheres 1, 2, and 3 also have a sphericity of 0.1
μm or less.

The method of mounting the ball is as shown in FIG. An adhesive having a strong adhesive force is put into the upper surface 8 of the sphere support member 20 and bonded in advance. In the shaft part 9,
When the screw 10 is screwed into the jig body 22, a parallel surface is formed in the opposite direction in order to strongly fix the screw 10 with a spanner or the like.

When the assembling of the sphere support member 20 with the three spheres 1, 2, 3 attached to the jig body 22 is completed,
The positions of the three spheres 1, 2, 3 with respect to the reference planes 5, 6 are accurately measured. In the present embodiment, a three-dimensional measuring machine capable of high-accuracy measurement is used. Using the surface 4 as an xy plane, the surface 4 is measured at multiple points, z = 0 is determined, and the z direction is set perpendicular to the surface 4. Next, it is assumed that the direction of the surface 5 is x-axis and y = 0, and that the surface 6 is y-axis and x = 0. With this, the coordinate system of the position measuring jig is determined. Next, the center coordinates of the spheres 1, 2, 3 are determined. The center position and radius of the sphere can be obtained by using the function of the coordinate measuring machine.

Next, a coordinate system formed by three spheres is determined by calculation. The way of determining is to define a plane passing through the centers of the spheres 1, 2, 3 and set it as an xy plane. The direction perpendicular to the xy plane is the z-axis. When the direction of the z-axis is specified from the upper part of the position measuring jig and the sphere is specified in the counterclockwise direction, for example, 1, 2, 3, the upper side becomes z + and the sphere is specified in the clockwise direction, such as 2, 1, 3. The lower side is set to z +. Then 3
It is assumed that the y-axis is designated by two points of the two spheres and the order thereof. For example, by designating 2, 1, the direction from the sphere 2 toward 1 is defined as the y-axis. When the z-axis and the y-axis are determined, the x-axis can be determined as the right-handed coordinates. Next, when the origin of the coordinate system formed by three spheres is designated by a sphere number, the position and orientation of the coordinate system formed by three spheres have been defined.

When the preparation is completed in this way, measurement is performed with a three-dimensional free-form surface measuring machine. First, three spheres 1, 2,
The upper part of each of the three is measured as a spherical surface, the center position of the spherical surface is determined, and a coordinate system passing through the three spheres is defined in the same manner as above. Next, the curved surface of the DUT 7 is measured in the same setup state. Since the function of the curved surface is input to the measuring device in advance, a parallel movement in the x, y, and z axes directions and a rotation around the x, y, and z axes are given so that the measured shape error with respect to the measured shape is minimized. (Fitting). From the relationship between the mounting reference plane of the object to be measured and the coordinate system formed by the three spheres, and the relationship between the coordinate system formed by the three spheres and the position and rotation of the measurement surface prepared in this way, The position and rotation of the measurement surface with respect to the surface can be measured.

As described above, three spheres are installed on the position measuring jig, and the relationship between the reference surface and the curved surface can be measured with high accuracy based on the relationship between the reference surface and the three spheres and the relationship between the three spheres and the curved surface. It will be. This makes it possible to measure the position of the mirror surface with respect to the reference surface of the mold when forming an optical mirror surface on the mold piece, and to correct the error if the position does not fall within the predetermined accuracy. is there. It is also possible to measure optical components made by the molding method, and if the position of the optical surface causes an error due to shrinkage or deformation due to molding, accurately measure the error and correct the optical mirror surface of the mold piece. is there.

Also, by using a sphere, the center of the sphere can be measured with high accuracy using a three-dimensional measuring machine, and the center coordinates of the sphere can also be measured with high accuracy using a measuring machine.

In order to obtain a high-precision sphere having a high sphericity at a low cost, a ball bearing is most suitable, and its diameter is 2 to 10 m from the viewpoint of easy measurement and easy handling.
m is suitable.

As a method of attaching the sphere to the jig, there is a method in which a screw is formed below the sphere by electric discharge machining and the sphere is fixed by using a screw. However, the sphericity of the sphere is reduced by electric discharge machining.
The method of bonding has the advantage that the sphericity does not change and can be fixed securely.

[0028]

As described above, according to the present invention,
A three-dimensional free-form surface can be measured accurately.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which an object to be measured is attached to a position measuring jig of an optical mirror surface and a curved surface is measured.

FIG. 2 is a diagram illustrating an example of a method of attaching a sphere.

FIG. 3 is a view showing a jig for determining a tool position by a conventional method.

FIG. 4 is a view showing measurement dimensions for measuring a jig to obtain a tool position.

[Explanation of symbols]

 1, 2, 3 sphere 4 base upper surface 5, 6 reference surface 7 DUT 8 sphere support member upper surface 9 shaft portion 10 screw 41 tool 42 oval shape 45 main shaft

Claims (3)

[Claims] 1. A measuring jig for measuring a shape of an object to be measured by a three-dimensional measuring machine, comprising: a jig main body; and a jig main body. A measuring jig comprising: three spheres for measuring a shape of an object to be measured. 2. The three spheres have a diameter of 2 to 10 mm.
The measuring jig according to claim 1, wherein a high-precision ball bearing is used. 3. The measuring jig according to claim 1, wherein the three spheres are fixed to the jig main body directly or at an end thereof via a set screw with an adhesive. Utensils.