JPS6355407A - Method and device for measuring accuracy of cured surface - Google Patents

Abstract

PURPOSE:To efficiently measure the accuracy of a curved surface of an object to be measured, with accuracy being endurable for practical use, by constituting the titled device so that the respective reflected rays from the object to be measured and a reference reflecting surface can be projected onto the same screen. CONSTITUTION:This device is constituted of a slide projector which has incorporated with a light source and a concentric circle-shaped pattern, a collimator lens 5 which is under said projector and converts a light beam from the projector 1 to parallel rays, a collimator lens 6 for converging the parallel rays emitted from the lens 5 to a focus of a prototype 2, the prototype 2 which is provided on an optical path of a light beam and has a reference reflecting surface 201 of a prescribed curvature, and a screen 3 to which two reflected light images from the reflecting surface 201 of an object to be measured 4 which has been placed on the reflecting surface 201. In this state, for instance, when the accuracy of the curved surface of the object to be measured 4 is bad, a first reflected light image by a reflection on the surface of the object to be measured 4, and a second reflected light image by a reflection on the reference surface of the prototype 2 are shifted and projected, respectively. By measuring this shift distance, the accuracy of the curved surface of the object to be measured 4 can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for measuring the accuracy of a curved surface of a material, such as the amount of warpage of a material having a smooth curved surface.

The method and apparatus of the present invention are useful for measuring the precision of curved surfaces such as liquid crystal cells or reflectors.

[Prior Art] Conventionally, the curvature or precision of the curved surface of a transparent or semi-transparent member such as a lens or a spherical mirror has been measured by placing the member to be measured on a Newtonian prototype having a predetermined curvature, and The beam is irradiated with coherent light, and measurements are made using Newton's prototype method, which creates interference fringes due to the difference in the optical paths of the reflected light from both.

Alternatively, it is also possible to measure the accuracy of a curved surface such as curvature using a so-called three-dimensional measuring device (Linges ferometer method).

A method based on focal length measurement is also used.

[Problems to be Solved by the Invention] In recent years, liquid crystal cells having a curved shape have tended to be applied to wide mirrors, outer mirrors, moon roofs, etc. mounted on vehicles. As a result, it has become impossible to ignore defects in curved surfaces such as warping of cell substrates, and a method and apparatus that can easily measure the accuracy thereof is desired.

Note that the Newtonian prototype method described above has too high accuracy and is good for measuring lenses and the like, but is not suitable for measuring members that do not require high precision, such as warping of liquid crystals. This is because the number of interference fringes to be counted becomes too large. Furthermore, when using a three-dimensional measuring device, information can only be obtained two-dimensionally in one measurement.

The present invention has been made in view of these problems, and it is an object of the present invention to provide a method and apparatus that meet the above requirements.

[Means for Solving the Problems] The method for measuring curved surface accuracy, which is the first aspect of the present invention, is based on a method for measuring curved surface accuracy which is a first aspect of the present invention. Objects to be measured having curved □ surfaces are arranged so as to overlap each other, and a light beam blocked by a reference pattern is irradiated onto the reference reflective surface to form a first reflected light image by reflection on the surface of the object to be measured. , and a second reflected light image resulting from reflection on the reference reflective surface of the prototype are projected onto the same screen, and due to the difference between the first reflected light image and the second reflected light image, the object to be measured is It is characterized by determining the accuracy of the curved surface.

Moreover, the curved surface accuracy measuring device which is the second invention of the present invention is as follows:
A prototype having a reference reflecting surface with a predetermined curvature, and an object to be measured having a curved surface with a curvature that substantially matches the predetermined curvature can be placed so as to be superimposed on the light incident side; a light source that illuminates the reference reflective surface; a light shielding section that is located between the light source and the reference reflective surface and blocks the irradiated light from the light source with a predetermined reference pattern; The optical path includes a semi-transparent mirror that is inclined at a predetermined angle and placed with its reflective surface facing the prototype side, and a screen that projects a reflected light image reflected by the reflective surface of the semi-transparent mirror. The accuracy of the curved surface of the object to be measured is determined by the difference between the first reflected light image projected on the screen, which is caused by reflection on the surface of the object to be measured, and the second reflected light image, which is reflected by the reference reflective surface. It is characterized by the fact that it asks for.

In other words, the present invention projects the respective reflected light beams from the object to be measured and the reference reflecting surface onto the same screen, and obtains information regarding the curved surface accuracy from the deviation thereof.

Here, the reference reflective surface with a predetermined curvature refers to a reflective surface that has a smooth surface and a predetermined radius of curvature. Further, the predetermined radius of curvature is the radius of curvature of the member whose curved surface accuracy is to be determined in an ideal state. Note that the reflectance is determined in relation to the reflectance of the surface of the object to be measured. In short, it is sufficient that the observer can clearly distinguish between the first reflected light image and the second reflected light image.

Further, the reference reflective surface of the prototype may be made of glass, but a reflective film of aluminum or the like may be formed as necessary.

The object to be measured is, for example, a -71 substrate used for film production, a liquid crystal cell manufactured using these substrates, a reflecting plate such as a mirror, and a member having a curved surface. Note that as long as the thickness is 3 mm or less, deviations due to reflection on the front and back surfaces can be ignored. In addition, if the object to be measured is not transparent, the amount of deviation from the projected pattern from the standard at the end face of the object to be measured is determined.

If a semi-transparent mirror is disposed between the light source and the reference reflecting surface, and the reflected light image is reflected by the semi-transparent mirror and then projected onto a screen, the degree of freedom in device design increases.

Further, by using an optical device such as a collimator and making the light beam passing through the semi-transparent mirror and the light beam reflected by the semi-transparent mirror into parallel light beams, the accuracy of measurement is improved.

The reference pattern provides a reflected light image.

For example, if a concentric pattern is used as the reference pattern, it becomes easier to observe deviations.

For example, if frosted glass, a diffuser plate, a milky white resin plate, thin paper, or the like is used as the screen, the first reflected light image and the second reflected light image can be observed from the back side. Furthermore, a scale may be provided on the screen for measuring the shift distance of each reflected image.

[Effect j: If the curvature of the object to be measured matches the curvature of the reference reflective surface and is smooth, the first reflected light image and the second reflected light image overlap,
The reflected image formed on the screen appears clear.

On the other hand, if the precision of the curved surface of the object to be measured is poor and the curvature is partially different from that of the reference reflecting surface, the surface of the object to be measured and the reference reflecting surface are not parallel in the portions where the curvature differs, so the first reflected light The image and the second reflected light image are projected with a difference between each other.

By measuring the deviation distance δ, information regarding the accuracy of the curved surface of the object to be measured is obtained.

[Example] The present invention will be explained below based on specific examples.

First, the measurement principle will be explained with reference to FIG. Although the following explanation has been made regarding a flat surface, the discussion can also be made that each minute portion irradiated with a light beam is a flat surface even in the case of a curved surface according to the present invention.

The tangent 41 of the reflective surface of the object to be measured 4 and the reference reflective surface 21 form an angle of θ[radl at a location further away from the origin O (the center of the object to be measured 4: see Figure 1). do.

In this case, the amount of warpage d at the part is d- or θ...
・It is given by (1).

Now, from the light source, the normal line 210 of the reference reflecting surface 21 (as shown in the figure, it is better to think of it as a plane 21- parallel to the reflecting surface 21)
When a ray a1 is incident at an angle α to
, is reflected by the surface 21' and becomes a light ray a2.

At the same time, the light ray a1 is also reflected by the surface 401,
It becomes light ray a3.

However, the normal 210 of the surface 21 and the normal 410 erected to the surface 401 form an angle θ[radl. Therefore, the rays at and a3 form an angle 2θ [rad].

Therefore, if the distance from the reflection point to the screen 3 is L, the deviation distance δ on the screen 3 is given as δ=2Lθ (2).

From equations (1) and (2), δ=2Ld/father...(3) get.

That is, by measuring the deviation distance δ, the warpage Id can be determined.

As shown in FIG. 1, the device used in this example includes a slide projector 1 that includes a light source and a concentric pattern, and a device below the slide projector 1 that converts light from the slide projector 1 into parallel light beams. A collimator lens 5 and a screen 3 on which parallel light rays emitted from the collimator lens 5 are converged to the focal point of the prototype 2 and two reflected light images from a reference reflective surface 401 of the measurement object 4 are projected via a semi-transparent mirror 7. It is composed of.

A glass with a unidirectional curvature having a radius of curvature R of 1800 mm was used as the prototype. Further, a curved glass having a radius of curvature R of 1800 mm, dimensions φ100 mm, and plate thickness 1.1 mm in an ideal state was used as the object to be measured. When this object to be measured was measured using a three-dimensional measuring machine, the warp IId was 0.1 mm, and at this time, a deviation of about 3 mm occurred on the screen.

A graph showing the relationship between the amount of warpage d of the object to be measured and the deviation distance δ during projection was created and a pop-up inspection was carried out (when the deviation was 3 mm).
When we conducted a splash test on items that exceeded 100%, the work efficiency was further improved than before.

As the slide projector 1, one manufactured by Cabin Kogyo (f=75 mm, 1:2.5) was used.

[Effects of the Invention] As described above, according to the present invention, it is possible to easily and efficiently measure the accuracy of a curved surface of a workpiece having a relatively large curvature with an accuracy that can be used in practice using a device with a simple configuration. .

[Brief explanation of drawings]

FIG. 1 is a principle diagram of a curved surface accuracy measuring device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating certain principles of the invention. 1...Slide projector, 2...Prototype 3...Screen 4...Object to be measured 5.6...Collimator 7...Semi-transparent mirror

Claims (7)

[Claims] (1) Place an object to be measured having a curved surface with a curvature that approximately matches the predetermined curvature on the light incident side of a prototype having a reference reflective surface with a predetermined curvature so as to overlap the same, and shield the object from light with the reference pattern. irradiate the reference reflective surface with a light ray, and obtain a first reflected light image due to reflection on the surface of the object to be measured and a second reflected light image due to reflection on the reference reflective surface of the prototype;
A method for measuring curved surface accuracy, characterized in that the curved surface accuracy of the object to be measured is determined from the deviation between the first reflected light image and the second reflected light image by projecting them onto the same screen. (2) When irradiating the reference reflective surface and the object to be measured with the light beam, the light beam is transmitted through a semi-transparent mirror tilted at a predetermined angle with respect to the optical axis, and the two reflected light beams are projected onto a screen. When making
The curved surface accuracy measuring method according to claim 1, wherein the curved surface accuracy is reflected by the semi-transparent mirror and then projected. (3) Using a predetermined optical device, the light beam passing through the semi-transparent mirror and the light beam reflected by the semi-transparent mirror are made into parallel light beams, and the light beam incident on the reference reflecting surface forming the concave mirror is reflected. The curved surface accuracy measuring method according to claim 2, wherein the light beam is converged to the focal point of the surface. (4) The curved surface accuracy measuring method according to claim 1, wherein the reference pattern is a concentric pattern. (5) a prototype having a reference reflecting surface with a predetermined curvature, and on which an object to be measured having a curved surface with a curvature that substantially matches the predetermined curvature can be placed overlappingly on the light incident side; and the prototype. a light source that illuminates the reference reflective surface; a light shielding section that is located between the light source and the reference reflective surface and blocks the irradiated light from the light source with a predetermined reference pattern; and the light source and the reference reflective surface. a semi-transparent mirror tilted at a predetermined angle and placed with its reflective surface facing the prototype side, and a screen for projecting a reflected light image reflected by the reflective surface of the semi-transparent mirror, in the optical path of the semi-transparent mirror; , the accuracy of the curved surface of the object to be measured is determined by the difference between the first reflected light image projected on the screen, which is caused by reflection on the surface of the object to be measured, and the second reflected light image, which is reflected by the reference reflective surface. A curved surface accuracy measuring device characterized by: (6) Between the light source and the reference reflective surface, a light beam passing through the semi-transparent mirror and a light beam reflected by the semi-transparent mirror are parallel rays, and a light ray incident on the reference reflective surface forming a concave mirror is provided. The curved surface accuracy measuring device according to claim 5, further comprising an optical device for converging the reference reflection surface to the focal point of the reference reflecting surface. (7) The curved surface accuracy measuring device according to claim 5, wherein the screen has a milky-white thin plate shape that allows the first reflected light image and the second reflected light image to be observed from the back side.