Shape measuring device, shape measuring method, and glass plate manufacturing method

A shape measuring apparatus includes: an image pick-up section that captures an image of two reflection spot groups of a pattern reflected in a first surface M1 and a second surface of a transparent flat plate and generates an image containing two reflection images separated in a direction perpendicular to a direction of extending; a first surface reflection spot group estimating section that estimates from the image a first surface reflection spot group of the pattern generated by the first surface of the transparent flat plate; an inclination angle calculating section that calculates an inclination angle of the first surface of the transparent flat plate at an estimated position of the first surface reflection spot group; and a surface shape determining section that determines a shape of the first surface of the transparent flat plate based on the calculated inclination angle.

TECHNICAL FIELD

The present invention relates to a shape measuring apparatus, a shape measuring method, and a manufacturing method for glass plates.

BACKGROUND ART

In the conventional art, as an example of a method of measuring a surface shape such as fine waviness in the first surface of a transparent flat plate, a technique disclosed in JP-A-2009-128098 is known. In this measuring method, an image generated when a pattern arranged above a transparent flat plate is reflected in the first surface of the transparent flat plate is captured by a line sensor. Then, on the basis of the obtained image, the surface shape of the transparent flat plate is calculated.

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

Nevertheless, in the measuring method of JP-A-2009-128098, in order that the first surface reflection image and the second surface reflection image of the transparent flat plate should be separated so that an exact surface shape should be obtained, a pattern designed in correspondence to the plate thickness of the transparent flat plate and an image capturing means like a three-line type color camera constructed from a plurality of line sensors have been necessary. Further, when the measuring method of JP-A-2009-128098 is used, the first surface reflection image and the second surface reflection image can be separated. Nevertheless, it has been difficult to determine which one of these is the first surface reflection image.

The present invention has been devised in view of such situations. Its object is to allow a simple construction to achieve accurate measurement of the surface shape of a transparent flat plate.

Means for Solving the Problem

In order to resolve the above-mentioned problems, the shape measuring apparatus according to an aspect of the present invention includes: an image pick-up section that is arranged such that an optical axis becomes perpendicular to a direction of extending of a linear pattern arranged above a transparent flat plate serving as a measurement object, the image pick-up section being configured to capture an image of two reflection spot groups of the pattern generated by a first surface and a second surface of the transparent flat plate and generate an image containing two reflection images separated in a direction perpendicular to the direction of extending; a first surface reflection spot group estimating section configured to estimate a first surface reflection spot group of the pattern generated from the image by the first surface of the transparent flat plate by using a positional relation of the transparent flat plate, the pattern, and the image pick-up section; an inclination angle calculating section configured to calculate an inclination angle of the first surface of the transparent flat plate at a position of the estimated first surface reflection spot group by using the positional relation of the transparent flat plate, the pattern, and the image pick-up section; and a surface shape determining section configured to determine a shape of the first surface of the transparent flat plate based on the calculated inclination angle.

In the above-mentioned shape measuring apparatus, the inclination angle calculating section may calculate the inclination angle on the basis of a condition that an incident angle of incident light travelling from the pattern toward a position of the first surface reflection spot group is equal to a reflection angle of reflected light travelling from a position of the first surface reflection spot group toward the image pick-up section.

In the above-mentioned shape measuring apparatus, the pattern may be a pattern constructed such that a plurality of dots are arranged linearly in the extending direction.

In the above-mentioned shape measuring apparatus, the transparent flat plate may be conveyed in a direction perpendicular to the direction of extending.

In order to resolve the above-mentioned problems, the shape measuring method according to an aspect of the present invention includes the steps of: by using an image pick-up section arranged such that an optical axis becomes perpendicular to a direction of extending of a linear pattern arranged above a transparent flat plate serving as a measurement object, capturing an image of two reflection spot groups of the pattern generated by a first surface and a second surface of the transparent flat plate and thereby generates an image containing two reflection images separated in a direction perpendicular to the direction of extending; estimating from the image a first surface reflection spot group of the pattern in the first surface of the transparent flat plate by using a positional relation of the transparent flat plate, the pattern, and the image pick-up section; calculating an inclination angle of the first surface of the transparent flat plate at a position of the estimated first surface reflection spot group by using the positional relation of the transparent flat plate, the pattern, and the image pick-up section; and determining a shape of the first surface of the transparent flat plate based on the calculated inclination angle.

In the above-mentioned shape measuring method, the inclination angle calculating step may calculate the inclination angle on the basis of a condition that an incident angle of incident light travelling from the pattern toward the first surface reflection spot group is equal to a reflection angle of reflected light travelling from a position of the first surface reflection spot group toward the image pick-up section.

In the above-mentioned shape measuring method, the pattern may be a pattern constructed such that a plurality of dots are arranged linearly in the extending direction.

In the above-mentioned shape measuring method, the transparent flat plate may be conveyed in a direction perpendicular to the direction of extending.

In order to resolve the above-mentioned problems, the manufacturing method for glass plates according to an aspect of the present invention includes: a melting step of melting raw material so as to obtain molten glass; a forming step of forming the molten glass into a continuous plate-shaped glass ribbon; a slow cooling step of gradually cooling the glass ribbon in the course of conveying so as to remove stress; a measurement step of measuring the surface shape of the glass ribbon; a cutting step of cutting the glass ribbon; and a control step of controlling slow cooling conditions in the slow cooling step based on a measurement result of the measurement step, wherein the measurement step is a step in which measurement is performed on the glass ribbon by using the above-mentioned shape measuring method.

Effects of the Invention

According to the present invention, a simple construction is allowed to achieve accurate measurement of the surface shape of a transparent flat plate.

MODES FOR CARRYING OUT THE INVENTION

First Embodiment

A first embodiment of the present invention is described below with reference to the drawings.

FIG. 1is a diagram showing a measuring method for the surface shape of a transparent flat plate according to the first embodiment.

A transparent flat plate3serving as a measurement object is, for example, a glass plate (a glass ribbon204inFIG. 10, described later). InFIG. 1, the transparent flat plate3is conveyed in the y-direction shown in the figure by the conveying apparatus not shown.

Above the transparent flat plate3(in the z-direction in the figure), a pattern member4is provided. On one surface of the pattern member4, a pattern X is provided that is constructed from dots X1, X2, X3, . . . aligned in line. The pattern member4is arranged such that the direction of alignment of the dots X1, X2, X2, . . . is in parallel to the x-direction in the figure (a direction perpendicular to the conveyance direction and parallel to the first surface of the transparent flat plate3) and that the surface provided with the pattern X is slightly inclined toward the transparent flat plate3side. Accordingly, on the first surface M1of the transparent flat plate3, a reflection spot group A of the pattern X is formed in a manner of extending in a direction perpendicular to the conveyance direction.

Further, a camera (area camera)2is provided above the transparent flat plate3. The camera2is arranged such that its optical axis is oriented in the direction perpendicular to the direction of extending of the reflection spot group A and that the reflection image of the pattern is contained within the picked-up image. Here, the positions and the orientations of the pattern member4and the camera2are fixed.

In the present embodiment, an image containing the reflection image of the pattern X is captured by using the camera2arranged in this manner. Then, on the basis of the obtained image, the shape of the first surface M1of the transparent flat plate3is measured. Here, in the present embodiment, it is assumed that the height H (the average height) of the transparent flat plate3first surface is known and that the surface shape to be measured is fine waviness or the like present in the first surface M1of the transparent flat plate3.

Here, in the positional relation of the transparent flat plate3, the pattern member4, and the camera2shown inFIG. 1, the pattern X of the pattern member4is reflected in a reflection spot group B in the second surface M2of the transparent flat plate3, and then captured by the camera2.FIG. 2is a diagram showing an example of the image G captured by the camera2. From the positional relation of the camera2inFIG. 1, the y-direction inFIG. 1corresponds to the down direction in the image G inFIG. 2, and the x-direction inFIG. 1corresponds to the left direction in the image G inFIG. 2. In the example inFIG. 1, as shown inFIG. 2, in the camera2, the reflection image b generated by the reflection spot group B is captured in a state of being separated into a position deviating in the positive y-axis direction (toward the side close to the camera2) from the reflection image “a” generated by the reflection spot group A in the first surface M1of the transparent flat plate3. The amount of positional deviation is determined by the position of arrangement of the pattern member4and the thickness t of the transparent flat plate3. Then, when the size of each dot constituting the pattern X is sufficiently small, the line of the reflection image generated by the reflection spot group A is clearly separable from the line of the reflection image generated by the reflection spot group B.

For example, the positional relation of the transparent flat plate3, the pattern member4, and the camera2and the size of each dot of the pattern X are determined by the relation shown inFIG. 3.FIG. 3is a diagram showing the light beam path in a case that the transparent flat plate3is image-captured from the camera2in a situation viewed from the horizontal direction (the x-direction) inFIG. 1. The camera2and the pattern member4provided with the pattern X are arranged above the transparent flat plate3of plate thickness t. The length of each dot in the direction perpendicular to the direction of extending of the pattern X is P.

The following description is given for a case that reverse ray tracing is performed on the light beam reaching the camera2, that is, for a case that the light beam path is traced from the camera side with a line of sight LX viewing the transparent flat plate3from the camera2.FIG. 3shows an example that the line of sight of the camera2(the straight line LX) is reflected in the first surface M1of the transparent flat plate3at an angle equal to the incident angle φ1and then travels in the direction of the light beam path LY so as to reach an edge of the pattern X. At that time, at the reflection spot in the first surface M1, the line of sight LX of the camera2is refracted into the transparent flat plate3at a refraction angle φ2, then reflected in the second surface M2, then refracted at the first surface M1, then travels in the direction of the light beam path LZ, and then reaches the pattern member9. This indicates that the line of sight LX of the camera reaches two sites separated by a distance Q on the surface of the pattern member4. That is, when a situation that the reflection images of the pattern X reflected in the front and the second surfaces of the transparent flat plate3are captured by the camera2is considered, it is indicated that the reflection image b generated by the reflection in the second surface M2of the pattern X is generated at a position deviating by the distance Q from the reflection image “a” generated by the reflection in the first surface M1. Here, the distance Q is calculated according to the following Formula (1).
Q=2t·cos φ1·tan φ2(1)
Here, the incident angle φ1and the refraction angle φ2are in the relation of the following Formula (2), where the refractive index of the transparent flat plate3is denoted by n.
sin φ1=n·sin φ2(2)

InFIG. 2, the condition necessary for satisfying a requirement that the reflection images “a” and b generated by the reflection spot groups A and B are separated, that is, each dot of the reflection image “a” generated by the reflection in the first surface M1does not overlap with each dot of the reflection image b generated by the reflection in the second surface M2is g>0. When this situation is described for the relation inFIG. 3, the positional relation of the transparent flat plate3, the pattern member4, and the camera2and the size of each dot of the pattern X are determined such that the length P of each dot is smaller than the distance Q (P<Q). For example, when the length P of each dot is to be adjusted, it is sufficient that the setup satisfies the following Formula (3).
P<2t·cos φ1·tan φ2(3)

Here, the pattern X is not limited to dots, and the length P in the direction perpendicular to the direction of extending of the pattern X may appropriately be set up within a range that the above-mentioned condition is satisfied.

FIG. 4is a diagram showing the relation between the reflection spot group A and the shape of the first surface M1of the transparent flat plate3, and shows a situation that the positional relation of the individual components inFIG. 1is viewed from the horizontal direction (the x-direction). A method of calculating the shape of the first surface M1of the transparent flat plate3on the basis of the image G is described below with reference toFIGS. 2 and 4.

InFIG. 4, the reflection spot group A is located on the first surface M1of the transparent flat plate3. Then, its position (the position in the right and left directions in the figure) can be know from the position (the position in the y-direction inFIG. 2) of the reflection image “a” generated by the reflection spot group A in the image G (FIG. 2).

That is, when a particular image G containing the reflection image “a” is obtained, the reflection spot group A on the first surface M1of the transparent flat plate3is located on the line of sight (the straight line LA inFIG. 4) viewed from the camera2toward the direction of the reflection image “a” in the image G. Thus, the position where the line of sight (the straight line LA) intersects the first surface M1of the transparent flat plate3indicates the position of the reflection spot group A on the first surface M1of the transparent flat plate3. When it is assumed that the height H measured from a particular reference plane M (the floor or the like) to the first surface M1of the transparent flat plate3is constant, the position of the reflection spot group A on the first surface M1of the transparent flat plate3can be identified in the above-mentioned method.

Here, as shown inFIG. 2, the image G contains: the line of the reflection image “a” generated by the reflection spot group A in the first surface M1of the transparent flat plate3; and the line of the reflection image b generated by the reflection spot group B in the second surface M2of the transparent flat plate3. Then, as described above, on the basis of the positional relation of the individual components shown inFIG. 1, the upper line (on the negative y-axis direction side inFIG. 2) in the two lines in the image G is the line corresponding to the reflection image “a”.

Then, when the position of the reflection spot group A on the first surface M1of the transparent flat plate3has been identified as described above, on the basis of the positional relation of the pattern X, the camera2, and the reflection spot group A inFIG. 4, the shape of the part at the reflection spot group A within the first surface M1of the transparent flat plate3can be calculated as described below.

That is, as shown inFIG. 4, light (indicated by a straight line LC) emitted from the pattern X of the pattern member4is reflected in the first surface M1of the transparent flat plate3at the position of the reflection spot group A, and then travels toward the camera2. The optical path of the reflected light is a straight line LA. Here, when the position of the reflection spot group A on the first surface M1of the transparent flat plate3is determined, the incident light LC and the reflected light LA are determined. Further, from the condition that the incident angle φ of the incident light LC incident at the position of the reflection spot group A is equal to the reflection angle φ of the reflected light LA reflected at the position of the reflection spot group A, a reflection plane S1is determined at the position of the reflection spot group A.

The reflection plane S1is a minute plane constituting the first surface M1of the transparent flat plate3at the position of the reflection spot group A. In other words, the local surface of the transparent flat plate3at the position of the reflection spot group A has the same inclination angle as the reflection plane S1inFIG. 4. As such, the shape (the inclination angle) of the first surface M1of the transparent flat plate3has been obtained at the position of the reflection spot group A.

When similar processing is performed on each spot in the reflection image “a” generated by the reflection spot group A inFIG. 2, the shape of the first surface M1of the transparent flat plate3is obtained at the position of each spot on the reflection spot group A. Further, when similar processing is performed successively in association with the conveyance of the transparent flat plate3toward the y-direction, the shape of the entire surface of the first surface M1of the transparent flat plate3can be obtained.

FIG. 5is a diagram showing the configuration of a shape measuring apparatus for implementing a measuring method for the surface shape of a transparent flat plate according to the above-mentioned embodiment.

InFIG. 5, the shape measuring apparatus includes an image pick-up section11and a computer10. The image pick-up section11is the camera2shown in the above-mentionedFIGS. 1 and 4. The computer10includes an image capturing section12, a first surface reflection spot group estimating section13, an inclination angle calculating section19, a surface shape determining section15, and a storage section16. Here, as for the individual sections12to15of the computer10except for the storage section16, their functions are implemented when a CPU executes a predetermined computer program stored in a ROM or the like.

The image capturing section12captures an image G (FIG. 2) from the image pick-up section11. A single image G may be used. Alternatively, a plurality of images G may be used that are captured successively in correspondence to the conveyance of the transparent flat plate3. From a single image G, as a result of the processing of the individual sections described below, the shape of the first surface M1of the transparent flat plate3can be obtained in a particular cross section parallel to the x-axis (FIG. 1). Further, when a plurality of consecutive images G are used, the surface shape can be obtained in a somewhat spread region of the first surface M1of the transparent flat plate3.

The first surface reflection spot group estimating section13detects from the image G a reflection image “a” contained in the image G and generated by the reflection spot group A of the pattern X in the first surface M1of the transparent flat plate3. Specifically, first, the first surface reflection spot group estimating section13detects a reflection image “a” and a reflection image b (two lines) from the image G by using a widely known image processing technique such as image recognition. As described above, which one of the two lines is the reflection image “a” is determined depending on the positional relation of the transparent flat plate3, the pattern member4, and the camera2, and hence is known. The storage section16already stores the known information that indicates which one is the reflection image “a”. Then, by using the information, the first surface reflection spot group estimating section13detects the reflection image “a” from the detected two lines consisting of the reflection image “a” and the reflection image b.

On the basis of the reflection image “a” detected from the image G, the inclination angle calculating section14calculates the inclination angle of the first surface M1of the transparent flat plate3at the position of the reflection spot group A on the first surface M1of the transparent flat plate3. The detailed calculation procedure is as follows.

First, the inclination angle calculating section14calculates the vertical direction (y-direction) position of the reflection image “a” in the image G. Then, on the basis of the vertical direction position, the inclination angle calculating section14calculates the position of the reflection spot group A located on the first surface M1of the transparent flat plate3. In order that the position of the reflection spot group A on the first surface M1is obtained, as described above, it is sufficient that the position where the straight line LA inFIG. 4intersects the first surface M1of the transparent flat plate3is obtained by geometric calculation. Alternatively, the correspondence relation between the vertical direction position in the image G and the position on the first surface M1of the transparent flat plate3may be tabulated in advance on the basis of the relative arrangement of the camera2and the transparent flat plate3. Then, by using the table, the position on the first surface M1of the transparent flat plate3may be calculated on the basis of the vertical direction position in the image G. The information concerning the arrangement of the camera2, the above-mentioned table, and the like necessary for the above-mentioned geometric calculation are stored in the storage section16. Then, using these, the inclination angle calculating section14performs the above-mentioned processing.

Then, the inclination angle calculating section14calculates the individual optical paths (seeFIG. 4) of the incident light LC from the pattern X and the reflected light LA toward the camera2at the position of the reflection spot group A on the first surface M1of the transparent flat plate3obtained as described above. Then, the inclination angle calculating section14calculates the reflection plane S1that reflects the incident light LC in the direction of the reflected light LA (a reflection plane that satisfies the relation that the reflection angle φ of the incident angle φ=the reflected light LA of the incident light LC) (seeFIG. 4), and then calculates the inclination angle of the obtained reflection plane S1. This inclination angle is the inclination angle of the first surface M1of the transparent flat plate3at the position of the reflection spot group A on the first surface M1of the transparent flat plate3, and is the calculation result of the inclination angle calculating section14.

Here, in order to calculate respectively the incident light LC, the reflected light LA, and the reflection plane S1, it is sufficient that geometric calculation is performed by using the positional relation of the individual components shown inFIG. 4. Alternatively, the correspondence relation between the position of the reflection spot group A on the first surface M1of the transparent flat plate3and the inclination angle of the reflection plane S1may be tabulated in advance on the basis of the relative arrangement between the three components consisting of the camera2, the transparent flat plate3, and the pattern member4(the pattern X). Then, the individual results may be calculated by using the table. The information concerning the arrangement of the camera2, the above-mentioned table, and the like necessary for the above-mentioned geometric calculation are stored in the storage section16. Then, using these, the inclination angle calculating section14performs the above-mentioned processing.

The inclination angle calculating section14performs the processing consisting of these individual calculation procedures, onto each spot of the reflection spot group A (e.g., onto the reflection spots corresponding to all dots constituting the pattern X).

On the basis of the inclination angle of the first surface M1of the transparent flat plate3obtained by the inclination angle calculating section14, the surface shape determining section15determines the shape of the first surface M1of the transparent flat plate3. When a single image G captured by the image capturing section12is used alone, the shape of the first surface M1of the transparent flat plate3is determined in one cross section parallel to the x-axis (FIG. 1). Alternatively, a plurality of images G are used that are captured successively in correspondence to the conveyance of the transparent flat plate3, the shape is determined in a somewhat spread region in the first surface M1of the transparent flat plate3. For example, when this shape measurement is performed continuously at all times, waviness and the like in the first surface of the glass ribbon204shown inFIG. 10can be monitored over the entirety in the length direction of the glass ribbon.

Second Embodiment

A second embodiment of the present invention is described below with reference to the drawings. Here, the second embodiment is the same as the first embodiment except for the points described below.

FIG. 6is a diagram showing a pattern provided in a pattern member4′ and an image G′ captured by the camera2.

The pattern member4′ includes three rows of patterns X(1), X(2), X(3) where a large number of dots are aligned in line in one direction (the right and left directions in the figure). When the pattern member4′ like this is used, the image G′ contains six lines in total consisting of: reflection images a(1), a(2), a(3) of the reflection spot group A of the individual patterns X(1), X(2), X(3) generated by the first surface M1of the transparent flat plate3; and reflection images b(1), b(2), b(3) of the reflection spot group B of the individual patterns X(1), X(2), X(3) generated by the second surface M2of the transparent flat plate3. When the intervals of the pattern X of the three rows (1), X(2), X(3) are set up appropriately, the individual reflection images can be separated within the image G′. Further, which one of these six lines is the reflection image of a particular pattern (for example, the pattern X (1)) generated by the first surface M1of the transparent flat plate3can be known, similarly to the first embodiment, from the positional relation of the individual components shown inFIG. 1.

According to the present configuration, even when a particular reflection image in the image G′ becomes indistinct, for example, by a reason that dust adheres to the first surface M1of the transparent flat plate3, the shape of the first surface M1of the transparent flat plate3can be measured by using other clear reflection images.

Third Embodiment

A third embodiment of the present invention is described below with reference to the drawings. Here, the third embodiment is the same as the first embodiment except for the points described below.

In the first embodiment, the height H measured from the reference plane M to the first surface M1of the transparent flat plate3has been known. In contrast, in the third embodiment, the shape of the first surface M1of the transparent flat plate3can be measured even when the height H of the first surface M1of the transparent flat plate3is unknown.

FIG. 7is a diagram showing a pattern provided in a pattern member4″ and an image G″ captured by the camera2.

The pattern member4″ includes: a pattern X where a large number of dots are aligned in line in one direction (the right and left directions in the figure); and a marker XM arranged near one dot XS constituting the pattern X. When the pattern member4″ like this is employed, in the image G″ contains a reflection image of the marker XM, in addition to the reflection images “a” and b of the reflection spot group A and the reflection spot group B of the pattern X generated by the first surface M1and the second surface M2of the transparent flat plate3.

In the present embodiment, the unknown height H of the first surface M1of the transparent flat plate3is obtained by using the reflection images of the marker XM and the dot XS. Once the height H of the first surface M1of the transparent flat plate3is obtained, similarly to the first embodiment, the shape of the first surface M1of the transparent flat plate3is obtained by using the reflection image of the pattern X.

A method of obtaining the height H of the first surface M1of the transparent flat plate3by using the reflection images of the marker XM and the dot XS is described below with reference toFIGS. 8 and 9.

First, attention is focused on the dot XS. Light emitted from the dot XS (seeFIG. 8) on the pattern member4″ is reflected in the first surface M1of the transparent flat plate3and thereby forms reflection image AS (seeFIG. 7) in the image G″. At that time, since the height H of the first surface M1of the transparent flat plate3is unknown, the true reflection spot on the first surface M1of the transparent flat plate3is not uniquely identified (the reflection spot is located somewhere on a straight line LS extending from the camera2toward the reflection image AS in the image G″).FIG. 8shows three reflection spot candidates A1(1), A1(2), A1(3) having different height H values. The height values of the reflection spot groups A1(1), A1(2), and A1(3) are denoted by H1, H2, H3(H1<H2<H3) respectively.

Here, when the reflection spot group A1(1) of height H1is adopted, the (assumed) tangential plane of the transparent flat plate3in the reflection spot group A1(1) is expected to have an inclination angle θ1(1) equal to that of the reflection plane S1where the light emitted from the dot XS on the pattern member4″ and then incident on the reflection spot group A1(1) is reflected toward the camera2along the straight line LS. When the reflection spot group A1(2) or A1(3) is adopted, similarly, the (assumed) tangential plane of the transparent flat plate3at each reflection spot has an inclination angle θ1(2) or θ1(3) equal to that of the corresponding reflection plane S2or S3.

At that time, when the reflection spot is located at a higher position (that is, A1(2) is higher than A1(1), and A1(3) than A1(2)), the incident angles from the dot XS on the pattern member4″ toward the individual reflection planes S1, S2, S3become shallower. Thus, the relation of θ1(1)<θ1(2)<θ1(3) is realized (here, the inclination angle is defined as the angle contained by the negative x-axis direction in the figure and the normal of each reflection plane directed upward in the figure). This relation is shown by a curve C1in the graph ofFIG. 9. As such, the inclination angle θ1(n) is a function of the height Hnof the reflection spot. Here, as described above, which point on the curve C1corresponds to the true reflection spot cannot uniquely be determined.

Next, attention is focused on the marker XM. Similarly to the dot XS, the reflection spot on the first surface M1of the transparent flat plate3where the light emitted from the marker XM on the pattern member4″ is reflected toward the camera2is located somewhere on the straight line LM directed from the camera2toward the reflection image AM in the image G″ (not uniquely identified).

Next, attention is focused on intersection point groups A2(1), A2(2), A2(3), . . . where the above-mentioned (assumed) tangential planes (the reflection planes S1, S2, S3, . . . ) that pass respectively the above-mentioned reflection spot candidates A1(1), A1(2), A1(3), . . . intersect the straight line LM. The dot XS and the marker XM are neighborhood points on the pattern member4″. Thus, each spot group A1(n) and the corresponding spot group A2(n) are similarly neighborhood points (n=1, 2, . . . ).

Here, a premise is placed that the change in the shape of the first surface M1of the transparent flat plate3is sufficiently loose. Then, at two mutual neighborhood points on the first surface M1of the transparent flat plate3, the individual tangential planes passing these two points respectively can be regarded as the same plane.

Thus, if a particular spot group A1(k) among the above-mentioned reflection spot candidates is the true reflection spot on the first surface M1of the transparent flat plate3, the spot group A2(k) located on the tangential plane (the reflection plane Sk) of the transparent flat plate3that passes the spot group A1(k) is concluded to be similarly a point on the first surface M1of the transparent flat plate3. Then, when a reflection plane Sk′ is considered that, by using the spot group A2(k) as a reflection spot, reflects the light from the upper the marker XM on the pattern member4″ toward the direction of the camera2along the straight line LM, the reflection plane (that is, the tangential plane of the transparent flat plate3in the spot group A2(k)) becomes identical to the tangential plane (the reflection plane Sk) of the transparent flat plate3in the spot group A1(k). Thus, the inclination angle θ2(k) is concluded to be equal to the inclination angle θ1(k).FIG. 8shows a situation that the spot group A1(2) is the true reflection spot on the first surface M1of the transparent flat plate3.

On the other hand, as for spot groups A1(j) (here, and corresponding to the spot groups A1(1) and A1(3) inFIG. 8) which is not the true reflection spot on the first surface M1of the transparent flat plate3, the spot group A2(j) located on the (assumed) tangential plane (the reflection plane Sj) of the transparent flat plate3that passes the spot group A1(j) is not a point on the first surface M1of the transparent flat plate3. Thus, the inclination angle θ2(j) of the reflection plane where the light from the upper the marker XM on the pattern member4″ is reflected at the spot group A2(j) toward the direction of the camera2along the straight line LM is concluded to be different from the inclination angle θ1(j).

Thus, as for the above-mentioned intersection point groups A2(1), A2(2), A2(3), . . . between the individual (assumed) tangential planes (the reflection planes S1, S2, S3, . . . ) passing the reflection spot candidates A1(1), A1(2), A1(3), . . . corresponding to the dot XS and the straight line LM determined by the marker XM, the inclination angles θ2(1), θ2(2), θ2(3), . . . of the (assumed) tangential planes (the reflection planes S1′, S2′, S3′, . . . ) are acquired. Then, by acquiring a reflection spot candidate A1(k) satisfying θ2(k)=θ1(k), it is concluded that the inclination angle θ1(k) and the height Hkat the reflection spot are obtained because the reflection spot group A1(k) is the true reflection spot.

In addition to the curve C1described above, the graph ofFIG. 9shows a curve C2indicating the relation between the height H′nof each above-mentioned intersection point group A2(n) and the inclination angle θ2(n) of the tangential plane at each intersection point group A2(n). In this graph, the spot group A1(2) where the value θ1(n) agrees with the value θ2(n) is the true reflection spot on the first surface M1of the transparent flat plate3.

As described above, the height H=Hkof the first surface M1of the transparent flat plate3has been calculated. Thus, similarly to the first embodiment, the shape of the first surface M1of the transparent flat plate3can be obtained by using the height H.

Fourth Embodiment

An example of application of the present invention in a manufacturing line for glass plates is described below.FIG. 10is a schematic explanation diagram of a manufacturing line for glass plates to which the shape measuring apparatus shown inFIG. 5is applied. A manufacturing method for glass plates in the manufacturing line shown inFIG. 10includes: a melting step of melting glass raw material so as to obtain molten glass; a forming step of forming the molten glass into a continuous plate-shaped glass ribbon; a slow cooling step of gradually cooling the glass ribbon in the course of moving; a shape measurement step of measuring the surface shape of the glass ribbon; a cutting step of cutting the glass ribbon; a control stop of, on the basis of the surface shape of the glass ribbon obtained by the measurement step, controlling slow cooling conditions in the slow cooling step.FIG. 11shows the steps of the manufacturing method for glass plates.

Specifically, during the manufacturing steps for glass plates, when a glass ribbon has been concluded to have a large warp on the basis of the data of surface shape of the glass ribbon obtained in the shape measuring method of the present invention, slow cooling conditions in the slow cooling step, like cooling rate conditions and cooling temperature conditions, are changed with taking into consideration the magnitude and the location of the warp. This prevents a defect in the shape caused by the warp or a crack caused by the warp, and thereby permits manufacturing of glass plates at a satisfactory yield.

Examples of the forming step include a float method, a roll-out method, a down draw method, and a fusion method. The present invention may appropriately employ any one of these, or another method. The example inFIG. 10is described for a case that a float method is employed.

At the melting step (S1inFIG. 11), a batch obtained by preparing and mixing raw materials such as silica sand, limestone, and soda ash in accordance with the composition of the glassware is supplied into a furnace, and then heated and melted at a temperature of approximately 1400° C. or higher in accordance with the type of the glass, so that molten glass is obtained. For example, the batch is supplied into the furnace through one end of the furnace. Then, a flame obtained by combustion of heavy oil or a flame obtained by combustion of mixture of natural gas and air is applied on the batch, so that the batch is heated and melted at a temperature of approximately 1550° C. or higher. As a result, molten glass is obtained. Further, an electric melting furnace may be employed for obtaining molten glass.

At the forming step (S2inFIG. 11), the molten glass obtained at the melting step is introduced through a furnace downstream section201into a molten tin bath203. Then, the molten glass is floated on the molten tin202and moved in the conveyance direction in the figure, so as to be formed into a continuous plate-shaped glass ribbon204(corresponding to the transparent flat plate3). At that time, in order that the glass ribbon204should be formed in a predetermined plate thickness, revolving rolls (top roll205) are pressed against both side parts of the glass ribbon204so that the glass ribbon204is expanded outward in the width direction (a direction perpendicular to the conveyance direction).

At the slow cooling step (S3inFIG. 11), the glass ribbon204formed as described above is extracted from the molten tin bath203by lift-out rolls208. Then, the glass ribbon204is moved inside the lehr210in the conveyance direction in the figure by metallic rolls209, so that the temperature of the glass ribbon204is cooled gradually. Subsequently, in the course from the exit of the lehr210to the cutting step, the glass ribbon204is cooled further into a temperature near the ordinary temperature. The lehr210includes a mechanism for supplying a controlled amount of heat by using combustion gas or an electric heater so as to perform slow cooling, which is located at a necessary position in the furnace. The temperature of the glass ribbon204at the exit from the lehr210is at or below the strain point of the glass of the glass ribbon204. That is, depending on the type of glass, the glass ribbon204is usually cooled to 150 to 250° C. The slow cooling step is employed for the purpose of removing the residual stress in the inside of the glass ribbon209and of reducing the temperature of the glass ribbon204. At the slow cooling step, the glass ribbon204passes through a measurement section211(corresponding to the shape measuring apparatus inFIG. 5), and is then conveyed to a glass ribbon cutting section212. The glass ribbon cutting section212cuts the glass ribbon204having undergone slow cooling into a temperature near the ordinary temperature (the cutting step). Here, the temperature of the glass ribbon at the glass ribbon cutting section212is usually in the range of an ambient temperature at the place to 50° C.

The position of image capturing for the glass ribbon204at the measurement step (S4inFIG. 11) (that is, the position of the measurement section211) is a position where the temperature of the glass ribbon204is at or below the strain point of the glass. Usually, the measurement section211is arranged at a position in the downstream of the conveyance direction relative to the glass ribbon exit of the lehr210. Further, it is preferable that the measurement section211is arranged at a position where the temperature of the glass ribbon204is at or below 200° C. Further, the measurement section211may be provided in the immediate upstream of the cutting step. However, in a case that the data obtained at the measurement step is to be reflected at the cutting step, it is preferable that the measurement section211is arranged at a position distant from the cutting position by 30 cm or greater, in particular, by 1 m or greater, depending on the movement speed of the glass ribbon204.

At the control step (S5inFIG. 11), controlling means (not shown) is utilized that, on the basis of the surface shape of the glass ribbon204obtained at the measurement step, calculates slow cooling conditions used in the lehr210. In response to instructions of the slow cooling conditions exchanged with the lehr210, the controlling means changes the conditions for the combustion gas, the electric heater, and the like provided in the lehr210. As such, the energy provided partly to the glass ribbon204or the rate of the provided energy is changed so that control can be performed for suppressing deformation such as curvature.

The embodiments of the present invention have been described above in detail with reference to the drawings. However, detailed configuration is not limited to these embodiments, and may adopt a design and the like within a scope not departing from the spirit of the present invention.

The present application has been described in detail with reference to particular embodiments. However, it is obvious for the person skilled in the art that various kinds of changes and modifications can be made without departing from the spirit and the scope of the present invention. The present application is based on a Japanese patent application (Japanese Patent Application No. 2010-136510) filed on Jun. 15, 2010, whose contents are incorporated herein by reference.

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