JPH0463322B2 - - Google Patents

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 apparatus of the present invention are useful for measuring the flatness of glass plates, liquid crystal cells, reflectors, and the like.

[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. It is measured using interference fringes (Newton rings) created by the optical path difference of the reflected light.

In addition, as a method for measuring flatness, JIS-
The method specified in R3202 (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 the amount of warpage using a distance gauge are used. .

[Problems to be Solved by the Invention] However, the above-described conventional methods are not simple. Also, the method using the distance gauge is
In some cases, the flatness of the object to be measured was measured only partially (measuring only the periphery).

However, in recent years, as devices to which liquid crystal cells are applied, such as car interior mirrors and meter displays, have become larger and mass-produced, it has become impossible to ignore the warpage of cell substrates. A method and apparatus that can measure this is desired.

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 problem] The flatness measuring method which is the first invention of the present invention is as follows:
A transparent or semi-transparent plate-shaped object to be measured is placed on the light incident side of a reference reflection plate having a flat reference reflection surface, and is shielded from light by a grid-like reference pattern. A light beam set to include the object to be measured is irradiated at a predetermined angle with respect to the normal to the reference reflective surface, and a first reflected light image is formed by reflection on the surface of the object to be measured; projecting a second reflected light image resulting from reflection on the reference reflective surface onto the same screen, and determining the amount of warpage of the object to be measured from the deviation between the first reflected light image and the second reflected light image; It is characterized by

Further, the flatness measuring device, which is the second invention of the present invention, has a flat reference reflecting surface, and a reference surface on which a transparent or translucent plate-shaped object to be measured can be placed so as to be overlapped on the light incident side. a light source that irradiates the reference reflective surface with a light beam set such that the object to be measured is included in the illumination area from a direction inclined at a predetermined angle with respect to the normal to the reference reflective surface; a light shielding section located between the light source and the reference reflective surface, which blocks the irradiated light from the light source with a grid-like reference pattern; and projects an image of reflected light from the reference reflective surface and the object to be measured. and a screen, and due to a difference between a first reflected light image projected on the screen caused by reflection on the surface of the object to be measured and a second reflected light image caused by reflection at the reference reflective surface, the object to be measured is The feature is that the amount of warpage of an object is determined.

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 amount of warpage, that is, the 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 curvature. 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.

The object to be measured is assumed to be, for example, a transparent or translucent plate-like member such as various glass substrates, ceramic substrates, resin substrates, and liquid crystal cells manufactured using these substrates used for thin film production.

The grating reference pattern provides a reflected light image.

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 to enable the reflected light image to 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. Further, the illumination area of the light beam is set in accordance with the size of the object to be measured.
In other words, since the distance (distortion amount) between the reference reflector and the outer edge of the object to be measured is determined by the deviation between the first reflected light image and the second reflected light image projected on the same screen, the illumination area of the light beam is is set so as to include at least the object to be measured. Thereby, the strain from the inside of the object to be measured to the outer edge is measured.

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] There is no warping of the object to be measured, and the flatness is good.
If the surface is smooth, the first reflected light image and the second reflected light image will overlap, and the reflected image formed on the screen will be clearly visible.

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

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

[Examples] The present invention will be described below based on specific examples.

(Example 1) FIG. 1 shows a flatness measuring device according to Example 1 of the present invention.

This device includes a slide projector 1 having a built-in light source and a grid pattern, and below the slide projector 1,
A reference reflecting plate 2 is provided horizontally in the optical path of the light beam from the slide projector 1 and has a flat reference reflecting surface 21 with no warp on the upper surface; and the reference reflecting surface 21
It is composed of a transparent object to be measured 4 placed thereon and a screen 3 on which two reflected light images from a reference reflecting surface 21 are projected.

Note that the optical axis of the central part 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 2 of the object to be measured is 300 mm, and the illumination area of the irradiation light is set to be larger than the width.

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 [rad] at a location away from the origin 0 (the center of the object to be measured 4: see Figure 1). do.

In this case, the amount of warpage d at the portion is d=θ……(1) is given by

Now, when a light ray _{a 1} forming an angle α with respect to the normal 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) is incident from the light source, the light ray a ₁ is reflected by surface 21',
The ray becomes a ₂ .

At the same time, the light ray a ₁ is also reflected by the surface 41 and becomes a light source a ₃ .

However, the normal 210 of the surface 21 and the surface 41
It forms an angle θ [rad] with the normal line 410 erected at .
Therefore, the rays a ₂ and a ₃ 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／……(3) get.

That is, by measuring the deviation distance δ, the amount of warpage d can be determined.

In the above device, no collimator is disposed between the slide projector 1 and the reference reflecting surface 21, and therefore the irradiated light beam is not a parallel light beam. For this reason, some errors are inevitable, but for example,
Using a plate material of 280 x 70 x t1.9 mm, we conducted a pop-up inspection to extract those with d > 0.1 mm (warpage of 0.035% or more), and found that the defective rate after extraction could be kept below 1%. did it. In view of the fact that the defective rate (defective rate after defective products are pushed out) using conventional feeler gauges was over 30%, this device was found to be sufficiently durable for practical use.

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

Further, for reference, the relationship between the amount of warpage of the object to be measured and the displacement distance during projection is shown in FIG.

(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 to the slide projector 1 is 70 cm, and the distance to the screen 3 is
170 cm, and a long plate-shaped glass substrate 4 (280 mm x 70 mm x 1.9 mm) as the object to be measured.
It was placed on the reflective surface 21 of the reference reflective plate 2, which was equipped 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 reflecting plate 21, and the reflectance was about 20%. The shift distance δ of the reflected light image of the glass plate 4 measured in this manner was 4 mm when the amount of warpage was 0.1 mm.

[Effects of the Invention] As described above, according to the present invention, it is possible to easily measure the amount of warpage, that is, the flatness, of the object to be measured with an accuracy that can withstand practical use, using a device with a simple configuration.

In addition, since the configuration is simple and does not use optical means such as a collimator or a semi-transparent mirror, the amount of light 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 Example 1 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 amount of warpage of the object to be measured and the displacement distance during projection. 1...Slide projector, 2...Reference reflector, 3...Screen, 4...Measurement object.

Claims (1)

[Claims] 1. Transparent or semi-transparent plate-shaped objects to be measured are arranged in an overlapping manner on the light incident side of a reference reflecting plate having a flat reference reflecting surface, and are shielded from light by a grid-like reference pattern. irradiating a light beam set so that the object to be measured is included in the illumination area at a predetermined angle with respect to the normal to the reference reflecting surface, A first reflected light image and a second reflected light image resulting from reflection on the reference reflective surface are projected on the same screen, and due to a deviation between the first reflected light image and the second reflected light image, the object to be measured is A flatness measurement method characterized by determining the amount of warpage. 2. The flatness measuring method according to claim 1, wherein the predetermined angle of inclination is 5 degrees or less. 3. A reference reflecting plate having a flat reference reflecting surface and on which a transparent or semi-transparent plate-shaped object to be measured can be arranged so as to overlap on the light incident side; and a predetermined angle with respect to the normal of the reference reflecting surface. a light source that irradiates the reference reflective surface with a light beam set such that the object to be measured is included in its illumination area from an inclined direction; and a light source that is located between the light source and the reference reflective surface; a light shielding part that blocks the irradiated light from the reference reflective surface using a grid-like reference pattern; and a screen that projects an image of the reflected light from the reference reflecting surface and the object to be measured, the image of the object to be measured projected onto the screen. Flatness characterized in that the amount of warpage of the object to be measured is determined from the difference between a first reflected light image due to reflection on the surface of the object and a second reflected light image due to reflection on the reference reflective surface. measuring device. 4. The flatness measuring device according to claim 3, 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.