JPS6342413A - Method and instrument for measuring flatness - Google Patents

Abstract

PURPOSE:To easily measure the flatness of a body to be measured with practical accuracy by projecting reflected light images of the surface of the body to be measured and a reference reflecting surface on the same screen, and measuring the deviation between both light images. CONSTITUTION:This instrument consists of a slide projector 1 which has a light source and a grating type pattern internally, a reference reflecting plate 2 which has the flat reference reflecting surface 21 on the top surface and is positioned below the projector, and the screen 3 where the two reflected light images of the plate type body 4 to be measured on the surface 21 and the surface 21 are projected. The center axis of the projection light of from the projector 1 is slanted at alpha (<=5 deg.) to a normal to the origin O of the surface 21. Then, the deviation distance delta of the reflected light images of the body 4 to be measured and the surface 21 on the screen 3 is delta=2Ld/l, where (d) is the curvature quantity at the position where a tangent to the reflecting from the reflecting surface of the body 4 and the surface 2 are at distance l from the point O, theta is their angle in terms of radian, and L is the distance from the reflection point of the projection light to the screen 3. Namely, the deviation distance delta is measured to find the curvature quantity (d).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for measuring the flatness of a transparent or translucent plate-like material, such as the amount of warpage of the material.

The method and position of the present invention are useful for measuring the flatness of glass plates, liquid crystal cells, reflectors, etc.

[Prior Art] Conventionally, the flatness of the surface or the parallelism of both sides of a transparent or translucent plate-like material such as a glass substrate has been determined by, for example, irradiating the plate-like material with coherent light and measuring it from the front and back surfaces. The measurement is performed using the interference fringes created by the optical path difference of the reflected light (the Newton ring).

In addition, as a method for measuring flatness, J l5-R320
2 (JIS Handbook, published by the Japanese Standards Association), or the method of placing the object to be measured on a flat surface plate and measuring warped bonds using a feeler gauge. .

[Problems to be Solved by the Invention] However, the above-described conventional methods were not simple. Furthermore, the method using a feeler gauge measures the flatness of the object only partially (measuring only the peripheral edge).

However, in recent years, as devices that use liquid crystal cells, such as car interior mirrors and meter displays, have become larger and mass-produced, it has become impossible to ignore the warping of cell substrates, and the parallelism of the front and back surfaces and the flatness of the surface have become increasingly important. There is a need for a method and apparatus that can easily measure the accuracy of degrees and the like.

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 Problem C] The flatness measuring method, which is the first invention of the present invention, overlaps a plate-shaped object to be measured on the light incident side of a reference reflector having a flat reference anti-tA surface. A light beam shielded by the reference pattern is irradiated at a predetermined angle with respect to the normal to the reference reflective surface, and a first reflected light image is produced by reflection on the surface of the object to be measured; The second reflection caused by the reference reflection surface
The method is characterized in that the reflected light images are projected onto the same screen, and the flatness of the object to be measured is determined from the deviation between the first reflected light image and the second reflected light image.

Further, the flatness measuring device according to the second aspect of the present invention includes: a reference reflecting plate having a flat reference reflecting surface and on which a plate-shaped object to be measured can be placed so as to overlap on the light incident side; A light source that irradiates the reflective surface from a direction inclined at a predetermined angle with respect to the normal to the reference reflective surface, and a light source located between the light source and the reference reflective surface that directs the irradiated light from the light source into a predetermined reference pattern. and a screen for projecting a reflected light image from the reference reflecting surface and the object to be measured, wherein the first reflection caused by reflection on the surface of the object to be measured is projected onto the screen. The method is characterized in that the flatness of the object to be measured is determined from the deviation between the optical image and the second reflected optical image caused by reflection on the reference reflective surface.

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

Here, the flat reference reflective surface refers to a reflective surface that is free from unevenness and warpage and has an infinite radius of convexity. In addition, the reflectance is
It is determined by the relative relationship with 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.

The objects to be measured are, for example, various glass substrates, long ceramic plates, resin substrates used to create thin films, liquid crystal cells manufactured from these substrates, or flat members such as reflective plates such as mirrors. ing.

The reference pattern provides a reflected light image.

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

In the present invention, the incident angle of the light beam that illuminates the reference reflective surface is inclined at a predetermined angle with respect to the normal to the reference reflective surface. This is so that the reflected light image can be directly projected onto the screen. Here, "directly" means not via an optical device such as a mirror or lens. Note that when the inclination angle is set to 5 degrees or less, the influence caused by the fact that the incident light rays are not parallel rays can be ignored.

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.

[Function] If the flatness of the 1!1 object is good and smooth, the first reflected light image and the second reflected light image will overlap, and the reflected image formed as a P image on the screen will be clearly visible. .

On the other hand, if the flatness of the object to be measured is poor, the surface of the object to be measured and the reference reflective surface are not parallel, so the first reflected light image and the second
The reflected light images are projected with a difference from each other.

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

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

<Embodiment 1> FIG. 1 shows a flatness 11 determining device according to Embodiment 1 of the present invention.

This device includes a slide projector 1 that includes a light source and a grid pattern, and a reference that is provided below the slide projector 1 under water in the optical path of the light beam from the slide projector 1 and has a flat reference reflective surface 21 on the upper surface. A reflecting plate 2, an object to be measured 4 placed on the reference reflecting surface 21, and the reference reflecting surface 21.
A groove is formed by a screen 3 on which two anti-Q-dimensional optical images from the screen 3 are projected.

Note that the optical axis at the center of the irradiated light from the slide projector 1 is inclined by 3 degrees with respect to the normal to the reference reflective surface 21. Further, the width of the object to be measured is 2 or 300 mm.

The principle of measurement by the above device will be explained with reference to FIG.

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 R away from the origin 0 (the center of the object to be measured 4: see Figure 1). do.

In this case, the warp lid at the part is d-cross θ...
・It is given by (1).

Now, from the light source, the normal line 21 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 forming an angle α with respect to 0 is incident, the ray at is reflected by the surface 21' and becomes a ray a2.

At the same time, the light beam al is also reflected by the surface 41,
This becomes light source a3.

However, the normal 210 of the surface 21 and the normal 410 erected to the surface 41 form an angle θ[radl.

Therefore, the rays a2 and a3 form an angle 2θ [radl.

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), get.

That is, by measuring the deviation distance δ, the warpage ff1d
can be found.

In the above device, slide projector 1 - reference reflective surface 2
A collimator is not placed between the two, and therefore the irradiation light beam is not a parallel light beam either. For this reason, some errors are inevitable, but
For example, the object to be measured is 280 x 70 x 1.9 m.
When we conducted a pop-up test using a plate material of m to extract those with d > 0.1 mm (warpage of 0.035% or more),
It was possible to reduce the defective rate after extraction to 1% or less. In view of the fact that the defective rate (defective rate after defective products are pushed out) by conventional feeler gauges was 30% or more, it was found that this device is sufficiently durable for practical use.

J3, the slide projector 1 manufactured by Cabin Kogyo Co., Ltd. <f=75 mm, 1:2.5> was used.

For reference, FIG. 4 shows the relationship between the maximum warpage of the object to be measured and the displacement distance during projection.

(Example 2) As shown in FIG. 2, a slide projector 1 similar to that of Example 1 was installed on a flat surface, and the light beam was irradiated at an angle of 5 degrees with respect to the normal to the reference reflector. The reference reflector 2 is tilted, and the distance from the slide projector 1 is 70 cm.
The distance to the screen 3 was 170 cm, and a long plate-shaped glass substrate 4 (280 m
mx70mmx1.9mm) was placed t'a on the reflective surface 21 of the reference reflective plate 2, which was provided with a stopper in advance.

Further, the reflectance of the glass substrate 4 was about 4%, and a reflective film was formed on the surface of the reference reflector 21, and the reflectance was about 20%. The shift distance δ of the reflected light image of the glass plate 4 measured in this way was 4 mm when the warpage was 0°1 mm.

[Effects of the Invention] As described above, according to the present invention, it is possible to easily measure the flatness of an object to be measured with a degree of practicality using a device with a simple configuration.

Furthermore, since the configuration is simple and does not use optical means such as a collimator or a semi-transparent mirror, the light intensity of the light beam is less likely to decrease, so there is no need to perform inspection in a dark room.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of a flatness measuring device according to a first embodiment of the present invention. FIG. 2 is a diagram showing a flatness measuring device according to Example 2 of the present invention. FIG. 3 is a diagram showing the measurement principle of the present invention. FIG. 4 is a graph showing the relationship between the warp of the object to be measured and the displacement distance during projection. 1...Slide projector 2...Reference reflector 3...Screen 4...Object to be measured Patent applicant Toyota Motor Corporation Figure 3 Figure 4

Claims (5)

[Claims] (1) Place plate-shaped objects to be measured on the light incident side of a reference reflector having a flat reference reflective surface so as to overlap them, and direct the light rays blocked by the reference pattern to the normal line of the reference reflective surface. irradiating the object at a predetermined angle and projecting 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 onto the same screen; A method for measuring flatness, characterized in that the flatness of the object to be measured is determined from the deviation between the first reflected light image and the second reflected light image. (2) The flatness measuring method according to claim 1, wherein the predetermined angle of inclination is 5 degrees or less. (3) The flatness measuring method according to claim 1, wherein the reference pattern is a grid pattern. (4) a reference reflecting plate having a flat reference reflecting surface and on which a plate-shaped object to be measured can be placed so as to overlap on the light incident side; and a direction inclined at a predetermined angle with respect to the normal to the reference reflecting surface. a light source that irradiates the 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; a screen for projecting a reflected light image from the object to be measured; a first reflected light image projected onto the screen by reflection from the surface of the object to be measured; and a second reflected light image by reflection from the reference reflective surface; A flatness measuring device characterized in that the flatness of the object to be measured is determined based on a deviation from a reflected light image. (5) The flatness measuring device according to claim 4, 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.